I don't know whether to ground all our systems to the chassis. Most of the Gillig's systems are 24v, but it also uses 12v provided by a Vanner. Both those voltages are, of course, grounded to the chassis. Our solar powered, 24v house system is not grounded to the chassis. 120v AC power from our inverter IS grounded to the chassis. Our minimal 12v house needs are currently provided by a small step down transformer, but the APU I'm adding will require considerably more 12v DC to operate its systems. My plan is to install a second house system (smaller battery bank) and charge it with the APU alternator and a single solar panel.
On a different thread, several posters mentioned not grounding differing voltage systems to the chassis. Is it best to run dedicated ground loops for both the 12v and 24v house systems? I don't have a clue.
Jim
I can not think of any reason why you would need isolate the ground loops. Nearly every new vehicle on the road today steps the battery voltage (12+) down to reference voltages (5+ and 3+) for various sensors and control motors-- all the grounds have 0+ voltage potential and are tied together. I am curious of the logic behind isolating the grounds.
Ground is ground, doesn't make a difference what the positive side is. Will be interesting what others have to say.
Sent from my iPad using Tapatalk
I never could get clear in my mind they ground to frame but all the gurus say a dedicated ground I know for a fact the Allison World Transmission and the DDEC will give you fits if any other ground are on the dedicated grounds it makes no sense to me
Quote from: luvrbus on July 09, 2014, 07:40:18 AM
I never could get clear in my mind they ground to frame but all the gurus say a dedicated ground I know for a fact the Allison World Transmission and the DDEC will give you fits if any other ground is on the dedicated grounds it makes no sense to me
Glad I'm not the only one confused. Looking forward to more input on this one.
Jim
Jim -
I asked this same question to Mike Sokol at noshockzone.org and this was his response -
QuoteThe most important connection from your shore power plug is indeed the safety ground wire to your bus chassis. According to both the NEC and RVIA codes, this must be uninterrupted by any switches or contacts. This is typically done by bonding (connecting) your RV's circuit breaker panel to the bus chassis via a heavy wire, usually 6 gauge or so along with bolting the panel to the metal frame. The incoming shore power cable's green safety ground wire is then directly connected to the ground bus bar in the breaker box. What needs to stay isolated from the metal box is the neutral bus (white wires) which separates the ground and neutral bus connections inside your vehicle. And you note, the ground and neutrals are bonded together by the generator or inverter (when running from them), or bonded together back at the campgrounds incoming service panel.
While it seems like the 12-volt DC and 120-volt AC circuits will get their "grounds" confused, they actually live together happily. What you have to be careful of is wiring color since in 12-volt DC wiring the black is negative (ground) while in 120-volt AC wiring the black is hot (120-volts). Yeah, that's caused more than a little confusion at times.
My guess is the only equipment that would have issues with a shared ground is 12-24v sensitive electronic equipment that relies on a specific voltage reading to operate such as the DDEC that Cliff mentioned. It could possibly give you incorrect readings on gauges as well but this is just a guess on my part.
I am a firm believer in home runs for grounds but that leaves a single point of failure if you ever lose the home run. In a perfect world with 12v or 24v I think I would have a home run (one positive and one negative) to a terminal block in each section or zone of 12v or 24v supply and ground the block to the frame.
Wondering what the big coach manufacturers are doing...
-Sean
Considering virtually all municipal electrical lines of all voltages and types are grounded through the Earth, the chassis is the same. Electricity only seeks out it's own voltage. Doesn't matter whether it is AC or DC.
In California, there is a twin electrical line coming from Washington and interestingly is DC. You can see the towers off 395 when going north from L.A. towards Mammoth. It is the tower that only has two sets of wires-most towers have three sets for 3 phase AC. Good Luck, TomC
Tom -
Most of the high power lines that have to carry voltages for long distances are DC because of efficiency. I think the limit on AC voltage is like 30 or 40 miles or something like that.
-Sean
Quote from: Seangie on July 09, 2014, 08:52:08 AM
Tom -
Most of the high power lines that have to carry voltages for long distances are DC because of efficiency. I think the limit on AC voltage is like 30 or 40 miles or something like that.
-Sean
I thought it was the other way around?
Nope. DC for long runs....Im sure its out there in Google land somewhere.
Fulltiming somewhere in the USA
1984 Eagle 10S
www.herdofturtles.org (http://www.herdofturtles.org)
Heres a good explanation, at first when Westinghouse and Edison were competing for the American system for electricity, DC could only go a mile, that was overcome, Tesla had a third wireless system.
AC current is a specific type of electric current in which the direction of the current's flow is reversed, or alternated, on a regular basis. Direct current is no different electrically from alternating current except for the fact that it flows in the same direction at all times. Alternating current was chosen early in the 20th century as the North American standard because it presented fewer risks and promised higher reliability than competing DC systems of the day. Many of DC's deficiencies were later corrected, but not until a substantial North American infrastructure had already been developed. DC is the European standard.
Electric power distribution requires a circuit, usually represented as two wires leading to a device that uses electricity. In AC current, one wire is negative and the other is either is positive or neutral (ground). The two wires take turns at sending electricity. In North America, AC current uses a standard "rhythm" in which each side gets its turn 60 times each second, thus the 60Hz designation given to standard AC current. This switching of polarity takes the form of a rhythmic pulse in the electrical current that occurs within the normal audible range. This is why you can actually hear this rhythm in circuits such as fluorescent lighting ballasts and audio equipment as a low buzzing tone. This buzz is referred to as "sixty cycle hum". Prior to the 1970s, two AC power schemes were used in North America. One offered energy at 45-50Hz, the other at 60Hz. "Fifty-cycle power", occasionally referred to as "rural power", is now obsolete and the 60Hz standard is now used throughout North America.
In DC circuits, the electricity is always the same polarity, which means that in a two-wire circuit, one "wire", or side of the circuit, is always negative, and the negative side is always the one that sends the electricity. There is no hum because there is no cyclic change in current flow. DC current is more effective for long-distance, high-voltage transmission because it results in less energy lost in transmission, but the cost of converting DC current to AC is relatively high, so DC is typically cost-effective only for long-distance transmission.
Electrical devices that convert electricity directly into other forms of energy can operate just as effectively from AC current as from DC. Lightbulbs and heating elements don't care whether their energy is supplied by AC or DC current. However, nearly all modern electronic devices require direct current for their operation. Alternating current is still used to deliver electricity to the device, and a transformer is included with these devices to convert AC power to DC power (usually at much lower than the supplied voltage) so that electronic devices can use it.
Many good explanations like this one out there,
Lvmci...
I think Europe uses 240vac 50 cycle.
AC was adopted because it could be stepped up to very high voltages for long transmission distances and stepped down to lower voltage at the other end. DC had
no similar ability as it doesn't work with transformers. The DC transmission lines Tom mentioned are very high voltage and is a special case; dedicated supply and load.
For more see
http://en.wikipedia.org/wiki/High-voltage_direct_current (http://en.wikipedia.org/wiki/High-voltage_direct_current)
Thanks for the info on transmission lines, but I'd love more input on grounding my bus systems. It's only the two DC house system voltages that puzzle me. As I said, the 120v AC is already grounded to the chassis. Should I do the same with 12v and 24v DC house systems? I would have routinely done so until some of the contributions to my charging a 24v system from a 12v source thread seemed to suggest that this was not a good idea.
Quote from: lvmci on July 09, 2014, 09:21:33 AM
In DC circuits, the electricity is always the same polarity, which means that in a two-wire circuit, one "wire", or side of the circuit, is always negative, and the negative side is always the one that sends the electricity.
Innocent question from an electrical far-from-expert (me): isn't Positive the side that sends the power out, and Negative is the return path for that power after it has been "used". Hence, "Negative Ground" in vehicles. Help, I'm confused!
I'm going to start my conversion's electrical systems soon, so I'm all ears and open to all suggestions.
Thanks, John
I saw a 4104 GM burn the guy change most of + ground stuff but forgot a few and it let the smoke out in a hurry when he connected the 2-8D batteries so to me looks like DC power can come from either depending on which is grounded
Aren't all these new huge windmills across the country DC like the ones from the past ?
My question would be this...if you do not ground the DC to the chassis where else would you ?
Quote from: eagle19952 on July 09, 2014, 04:28:15 PM
My question would be this...if you do not ground the DC to the chassis where else would you ?
Dedicated, heavy-gauge wire ground loop for each house voltage. Tap the loop at any point where I need that voltage.
Jim - you can safely ground everything to the frame of the bus. As I said in a previous post - I would run a direct line from the negative (ground) of the 12v or 24v supply to a block and then ground the block to the frame. Make sure your 12v and 24v Batteries both have a direct fused connection to the frame of the bus (ground/return path for DC).
As far as wire size - blue sea makes a great app for your smart phone where you put in any combination of watts/amps/volts/length etc and it calculates fuses and wire size.
Have fun ;)
-Sean
Fulltiming somewhere in the USA
1984 Eagle 10S
www.herdofturtles.org (http://www.herdofturtles.org)
One thing to keep in mind here is that the AC chassis grounds are not normally carrying any current, they are just safety grounds in case of equipment failure. DC circuits, 12 or 24 volts, the chassis ground is carrying current and it is not always the best conductor, thus the suggestion that you run a copper home run return from each load.
BTW, the reason for DC power transmission on the west coast is that the distance from Bonneville Power to the Los Angeles area is 1500 miles, the half wave length of 60 Hz. If you know anything about antennas and wavelength, that is the zero crossing point, thus very high losses.
(I did some work at Bonneville years ago and that's the explanation I got from the engineers).
I have no expertise to back this up, but the way I see it is that there is no problem with grounding multiple electrical voltages to the chassis. That's what we have had on both buses and what it is the overwhelming norm. Electronics are a different story; small variations can cause large changes. Hence, as LRB mentioned, engine and transmission computers use isolated circuits.
Quote from: Seangie on July 09, 2014, 06:44:31 PM
I would run a direct line from the negative (ground) of the 12v or 24v supply to a block and then ground the block to the frame. Make sure your 12v and 24v Batteries both have a direct fused connection to the frame of the bus (ground/return path for DC).
www.herdofturtles.org (http://www.herdofturtles.org)
Sean,
To be sure I'm understanding you, are you saying to ground each battery bank to the chassis through a fuse AND ALSO run a ground wire to the negative side of a fuse block WHICH IS ALSO grounded to the chassis?
Thanks for all the input.
Jim
I would chime in to mention some info if I can just put it out there and some of you can take off with it. Some of these I worked with in the past a bit, anyway Each component has to be considered separately, Lets understand converters some are not isolated themselves and thus have a floating ground these should not use the same general frame as I understand because even dc is powerful.
terms like isolate, home run, J1939, CAN, Multiplexing are all way out there, and were there.
the AC grounds need some "nec" answers wayout of my league
The newest 01 up mostly ecms, atms, bdms are needing isolated grounds (home runs) because they - hold on now CAN use the same wire to do different things on a vehicle using a system called multiplexing via J1939 protocol, to top it off these voltages might have hi sides and low sides.
Again Im interested in working through this with you all as there are many many sharper knives here than me.
Just wanted to send this out there
Good day everybody
Quote from: Seangie on July 09, 2014, 09:11:34 AM
Nope. DC for long runs....Im sure its out there in Google land somewhere.
Fulltiming somewhere in the USA
1984 Eagle 10S
www.herdofturtles.org (http://www.herdofturtles.org)
My understanding is that DC is used primarily for high power undersea links that aren't too long. Because an AC line has too much capacitive coupling between the phases in such small-diameter cables so losses are higher than for DC which has only resistive losses.
http://en.wikipedia.org/wiki/Pacific_DC_Intertie (http://en.wikipedia.org/wiki/Pacific_DC_Intertie) has a bit on this tie line ande they say skin effect is one deciding factor, plus the ease of connecting two non-synchronised power systems.
QuoteDC is the European standard
for what?
Quote from: Lostranger on July 10, 2014, 04:44:59 PM
Sean,
To be sure I'm understanding you, are you saying to ground each battery bank to the chassis through a fuse AND ALSO run a ground wire to the negative side of a fuse block WHICH IS ALSO grounded to the chassis?
Thanks for all the input.
Jim
Jim - that is correct. Not totally necessary as it is common to ground the negative to the frame (which supplies a return path to the 12v battery that is also grounded to the frame) and not have a seperate run for the negative on a DC circuit.
To compare the 2 - In an AC circuit you have a hot wire (black), a neutral wire (white) which both go back to the panel (connected to the "source") Then there is a "green" ground that connects to the frame of the appliance or device requiring power. This green wire carries excess voltage (in case of a short) back to the panel then to the ground. In an RV the ground will be bonded to the neutral inside the generator or bonded to the neutral somewhere beyond the pedastal at the campground.
In DC if you want a true ground (like you would have in an AC circuit) you would have a positive wire (red is typical), a negative wire (unfortunately black is typical although yellow, orange or blue can be common here) and then you can run a seperate line grounding the device to the chassis (green) that could carry any additional voltage back through the frame and because we don't have an alternating current it would just be carried back to the negative connection on the battery. If you think of the negative in a DC circuit as neutral this is where you would be "bonding" the ground and the neutral.
The DC current would take the return path of least resistance (the wire that is directly run to the negative on the battery) unless there was a short in the device or wire in which case the return path would be the chassis of the bus.
If you had breakers or a fuse for your DC circuit they should "pop" if there is a short as there would be no resistance in a short circuit and the amperage would shoot up.
I reccomended fusing the negative side of your batteries based on past conversations with Sean Welsh who made some really good points as to why. You'll have to dig up previous posts to read those details.
Know that most of my DC circuits including the bus circuits are all grounded to the frame and do not have a return wire. Also the positive side of my batteries are fused, not the negative. I should practice what I preach but it takes time and money for that as most of my DC stuff was done before I got the bus. Know that it is on my to do list to update this. ;D
I hope that is not too confusing. I do agree with previous comments that there are some devices that need their own circuit but in the DC world that circuit is typically designed into the device itself as anything battery operated (12v, 24v or on an alternator) will be operating in a system that has fluctuating voltages.
-Sean
Fulltiming somewhere in the USA
1984 Eagle 10S
www.herdofturtles.org (http://www.herdofturtles.org)
Oooops...double post
OK confused here LOL
What size fuse should I but in the Neg side of my 12v and 24v systems ??
they have always been straight to ground :)
will have to but this on the list of to do :)
Wasn't it Lucas the Prince of Darkness that fused the ground on some of the British cars and bikes,I have heard the argument for years on fusing the ground and installing the relays on the ground side both pro and con.
Richard (Driving Mrs Lazy) had every relay on the Eagle on the ground side Sonnie and Mike worked for weeks trying to make the systems work Sonnie replaced all the relays to the + side so I guess it gets down to preference
Here is one past discussion on grounding the negative side of the house battery bank: http://www.busconversions.com/bbs/index.php?topic=22290.msg244760#msg244760 (http://www.busconversions.com/bbs/index.php?topic=22290.msg244760#msg244760) (http://www.busconversions.com/bbs/index.php?topic=22290.msg244760#msg244760 (http://www.busconversions.com/bbs/index.php?topic=22290.msg244760#msg244760))
Sean makes a potent argument. One of the last posts in the referenced thread offers several links to related threads on this board. I have not looked at any of those, but I'm sure they include gems.
Based on what I've learned, I believe I will put my catastrophic fuse on the ground side of both house battery banks. On the 24v bank, that will mean connecting a type T fuse to the last battery in pack. At the other end of the fuse holder I plan to connect both the inverter negative lead and a ground strap to chassis. Plan to do same with 12v bank, but no inverter connects to it. Ground/fuse/strap to chassis.
Does this sound reasonable to those who know? Any recommendations on fuse sizes? 24v battery bank is 490 amp/hours. 12v bank is 245 amp/hours. 2/0 cable all round.
Thanks again for the great discussion.
Jim
This link on battery info has been posted before, but it couldn't hurt to make it available again: http://www.batteryfaq.org (http://www.batteryfaq.org)
Aren't the catastrophic fuse a delay type with the sand I had problems with mine showing some voltage but would not run the inverter.
I have a Magnum inverter and was torn between the fuse on the - or + Magnum told me on the + side or void the warranty lol for the life of me I could never figure out how they could tell were the fuse was located if you needed warranty work
Just guessing but I would say the inverter has internal connections to it's chassis ground. So if your ground side fuse blows, it still has full power through those circuits.
re: Sean's comment on automotive fusible links; they are not part of the start circuit. They are in the circuit supplying power to the fuse box. I do not support fusing the starter or alternator circuits but each to his own.
Quote from: luvrbus on July 12, 2014, 10:07:59 AM
I have a Magnum inverter and was torn between the fuse on the - or + Magnum told me on the + side or void the warranty
My Magnum is out of warranty, so....
Keep in mind that the fuse I am talking about is a catastrophe fuse on the negative side of the batteries that connects to the frame. I would still fuse all my dc devices (inverter, fridge, lights...etc.) on the positive side.
-Sean
Fulltiming somewhere in the USA
1984 Eagle 10S
www.herdofturtles.org (http://www.herdofturtles.org)
Quote from: Seangie on July 12, 2014, 03:56:49 PM
Keep in mind that the fuse I am talking about is a catastrophe fuse on the negative side of the batteries that connects to the frame. I would still fuse all my dc devices (inverter, fridge, lights...etc.) on the positive side.
Got it. Fusing every load was never an issue. My original question was whether to ground the two house DC systems to the chassis or run dedicated ground loops for 24v and 12v. In the process of working through that, I discovered the concept of putting the catastrophic battery fuse on the ground side rather than the positive side. THAT was a new idea for me, but I like it.
Thanks again.
Jim
I have knew Sean Welsh and Dick Wright both for a long time it was always a interesting conversation to listen at those 2 on their ideas on generators and inverters I didn't know enough about a electrical setup to tell which party was right or wrong
Then would someone paint a picture of this catastrophic fuse saving a bus from burning to the ground, or an example of the result of not having one...or even provide a picture of one installed.
I don't have one. never crosssed my mind that I'd need one.
Seangie even thinks it's a good idea but he doesn't have one.
Ground is ground it's all ending up in the same place no matter where you attach it. Next we'll all be pounding brass rods 8ft feet into the ground.
It saves the batteries and inverter if your lucky Donald ,100's around that don't have the high dollar catastrophic fuse just a safety valve people buy Me personally I never saw a inverter or cable burn on one most of the time the relays go out and the inverter doesn't work anyway and I had factory conversion with 2 -2012 Trace Inverters they were not fused either
The fuse I had that was bad was a Ebay deal the guy screwed me it would test because when I open it I found the silica in the sand had melted and formed kinda of link, 50 bucks and real pissed over that deal
Jim can I ask what models are the inverters or components for your dc system, I thought you mentioned solar also. Just curious and interested
Thanks and good day
Quote from: brmax on July 13, 2014, 09:30:36 AM
Jim can I ask what models are the inverters or components for your dc system, I thought you mentioned solar also. Just curious and interested
Thanks and good day
We have four Samsung, 255 watt PV panels that are rated at nominal 24v each. I wired them in two series pairs to feed 48v to a MorningStar 65 amp MPPT charge controller. From there to main bank of four 8D AGM batteries wired series/parallel for 24v. The MorningStar can be set for 12/24/48v output. (I think. Not sure about the 48v output, but 48v input is no problem.) Battery bank wired with 2/0 fine strand copper to Magnum MS4024 inverter. We probably don't need 4000 watts of inverter potential, but the price was right, and it performs flawlessly. So does the solar charging system. I used to think that all "modern" house vehicles had to depend on shore power and/or a large generator, but reading Rob Gray's build in 2011 convinced me otherwise. We've been off grid since February of last year. We have an old Kohler 4500w gasoline generator, but we've not used it or hooked to shore power in months. We do currently live without air conditioning, however. That should change before end of summer, but we'll use a tiny window unit over the bed and run it sparingly.
Even though we're living in the bus, our conversion is a work in progress. We'll be buying a Sundanzer chest-type refrigerator to operate on 24v. Current refer is propane. We have a full-size front loading Maytag washer and propane dryer. Our Rheem, propane-fired, tankless water heater is probably overkill for two people, but, again, the price was right, and it works flawlessly. We both love to cook. We'll replace the current Magic Chef propane rv range with a 30" Premier range that uses battery ignition. All lighting will be LED. We're doing as much as possible with 24v DC, but we have a few things that take 12v, and so far that has meant using a small step-down device. Our primary 120v AC needs are washing clothes, entertainment and power tools.
Our primary heat source is a small wood burner I patterned on stoves designed for yachts. We used propane radiant heaters for backup last winter, but no more. I recently acquired a ThermoKing Tripac APU. It's an older model, and I am in the process of refurbing it to use instead of the generator. It will mount over the engine where the original air handler sat. We'll use it for backup heat and cooling in the bed/bath/utility area at the rear of the bus. When it is running, it's alternator(s) will charge batteries.
Hope that's not too much of an answer. We're still learning how to live off grid, but we seem to be getting better. We have utility water at home base, so we don't have to operate a well pump.
Jim
Your rig does sound interesting.... :)
this part i did not know was possible...
to feed 48v to a MorningStar 65 amp MPPT charge controller. From there to main bank of four 8D AGM batteries wired series/parallel for 24v. The MorningStar can be set for 12/24/48v output.
Does this reduce the charge time....what is it's advantage ??
could this be configured as
48 volt panel config to the controller
set to 12 volt output charge
into 12 volt battery bank.
Quote from: eagle19952 on July 14, 2014, 07:31:02 AM
Your rig does sound interesting.... :)
this part i did not know was possible...
to feed 48v to a MorningStar 65 amp MPPT charge controller. From there to main bank of four 8D AGM batteries wired series/parallel for 24v. The MorningStar can be set for 12/24/48v output.
Does this reduce the charge time....what is it's advantage ??
could this be configured as
48 volt panel config to the controller
set to 12 volt output charge
into 12 volt battery bank.
I run 48v from the panels because it's easy to do, and it makes for lower line loss. The MorningStar will definitely provide charge for a 12v battery bank. Just select for that in the setup. 48v in with 12v out is no problem.
The big advantage of Maximum Power Point Tracking (MPPT) solar charge controllers is that they will down-convert voltage from the PV array to whatever the batteries need, but at the same time they up-convert current, so the power remains essentially the same. Like Lostranger, I will be using the Morningstar TS-MPPT-60 controllers for my setup. My PV panels produce about 30V and 8.5A each, and I'll run four panels in parallel to each controller which will then turn that into about 14.5V to charge the batteries, but it will push about 60A into the batteries if needed, twice the current the panels produce. Magic! The controllers can accept up to 150V input, such as from a large system with panels in series, and down-convert to 12, 24 or 48V - however, the closer the panel voltage is to the charging voltage, the more efficient the controllers run. For my application the controllers will be running at high-90s % efficiency.
If you have Pulse Width Modulated (PWM) controllers, essentially they waste the excess voltage by not converting it into amps, so for larger systems they don't make any sense to use. For us folk achieving total self-sufficiency from solar (yes, it can be done, contrary to what the naysayers think), squeezing every possible amp into the batteries is the key.
John
Quote from: Iceni John on July 14, 2014, 12:57:25 PM
The big advantage of Maximum Power Point Tracking (MPPT) solar charge controllers is that they will down-convert voltage from the PV array to whatever the batteries need, but at the same time they up-convert current, so the power remains essentially the same. Like Lostranger, I will be using the Morningstar TS-MPPT-60 controllers for my setup. My PV panels produce about 30V and 8.5A each, and I'll run four panels in parallel to each controller which will then turn that into about 14.5V to charge the batteries, but it will push about 60A into the batteries if needed, twice the current the panels produce. Magic! The controllers can accept up to 150V input, such as from a large system with panels in series, and down-convert to 12, 24 or 48V - however, the closer the panel voltage is to the charging voltage, the more efficient the controllers run. For my application the controllers will be running at high-90s % efficiency.
If you have Pulse Width Modulated (PWM) controllers, essentially they waste the excess voltage by not converting it into amps, so for larger systems they don't make any sense to use. For us folk achieving total self-sufficiency from solar (yes, it can be done, contrary to what the naysayers think), squeezing every possible amp into the batteries is the key.
John
What batteries (type like AGM, size, how many, etc.) are you using for this setup, John?
Probably golfcart, maybe L-16, perhaps something else if I can get a good deal on them. I made two pull-out drawers that each have space for four batteries, but because I have two separate systems running in parallel I could conceivably have different types of batteries in each drawer, provided the controllers can handle them. I'll be charging golfcart batteries at the upper end of their 5 to 13% recommended charge rate - my intention is to have the batteries fully charged by midday or very soon after, leaving all the panels' output during the afternoon for heating water or running power tools etc.
I had to use two controllers because I want to keep the house system the same 12V as the chassis, otherwise life gets too complicated with different voltages. The theoretical disadvantages of 12V for heavier loads are offset by the simplicity of having everything able to run off any source, including connecting the house batteries to the chassis in emergencies. Simple is good!
John
Thanks Jim and everybody for sharing there input and the topic is very helpful, Its great as I can re read some discussions if needed.
Great work thanks again
Quote from: Iceni John on July 15, 2014, 08:16:30 AM
Probably golfcart, maybe L-16, perhaps something else if I can get a good deal on them. I made two pull-out drawers that each have space for four batteries, but because I have two separate systems running in parallel I could conceivably have different types of batteries in each drawer, provided the controllers can handle them. I'll be charging golfcart batteries at the upper end of their 5 to 13% recommended charge rate - my intention is to have the batteries fully charged by midday or very soon after, leaving all the panels' output during the afternoon for heating water or running power tools etc.
I had to use two controllers because I want to keep the house system the same 12V as the chassis, otherwise life gets too complicated with different voltages. The theoretical disadvantages of 12V for heavier loads are offset by the simplicity of having everything able to run off any source, including connecting the house batteries to the chassis in emergencies. Simple is good!
John
Thanks, John. Not AGM? Won't they charge quicker (i.e. let you take advantage of the best sun time)?
It's less that AGM charge quicker than wet at the same charge rate, it's more that AGM can accept a higher charge rate so can be charged faster. If the solar system can deliver say 25 amps at 14.5 volts charge rate you can charge a 250 AH bank at 10% for wet or AGM, but if you can get 75 amps at 14.5 volts you can charge a 250 AH AGM bank in a third the time. Roughly speaking, of course. Usually a solar system is charge rate limited by the output of the field. The other big advantage of AGM deep cycle batteries is they can be discharged to around 20% SOC while wet batteries should only be discharged to 50% SOC before you start to hurt their life significantly. Wet cell manufacturers actually recommend no more than 80% SOC for best life. That means an AGM bank could have double to triple the usable capacity for the same AH rating. It's all a balancing act.
Brian
Quote from: bevans6 on July 16, 2014, 04:17:26 AM
It's less that AGM charge quicker than wet at the same charge rate, it's more that AGM can accept a higher charge rate so can be charged faster. If the solar system can deliver say 25 amps at 14.5 volts charge rate you can charge a 250 AH bank at 10% for wet or AGM, but if you can get 75 amps at 14.5 volts you can charge a 250 AH AGM bank in a third the time. Roughly speaking, of course. Usually a solar system is charge rate limited by the output of the field. The other big advantage of AGM deep cycle batteries is they can be discharged to around 20% SOC while wet batteries should only be discharged to 50% SOC before you start to hurt their life significantly. Wet cell manufacturers actually recommend no more than 80% SOC for best life. That means an AGM bank could have double to triple the usable capacity for the same AH rating. It's all a balancing act.
Brian
Yeah, that's pretty much what I was (clumsily) getting to. But what happens if a solar array can put out 75 amps but the batteries will only accept 25? Does the battery get cooked? Does the "extra" charge just "not happen"? If the charge controller holds the charge at a max of 25, doesn't that mean that you're losing a big chunk of your charge capacity during peak sun times? After all, there's a curve to solar output; low in the AM, high at midday, and low in the late PM. You wouldn't want to lose any opportunity to charge with all the panel output, right?
And balancing, yes, like $$$ balanced against no-$$$.
I think that's why you have a charge controller, so that batteries don't get cooked. If your solar setup has excess capacity, it's just like it wasn't ever there. It only counts if it gets used by something.
Brian
Quote from: bevans6 on July 16, 2014, 07:52:50 AMI think that's why you have a charge controller, so that batteries don't get cooked. If your solar setup has excess capacity, it's just like it wasn't ever there. It only counts if it gets used by something. Brian
That's what I would have guessed (but if I don't know, I ask). But my estimation was right ... if you have an hour of big sunshine and you don't put all that energy in a battery, it's lost? Thanks, this solar stuff is all new to me ... and I never caught on to all those electrictron things anyway.
It's like you have a 200 amp service at your house, but all the lights are off. The 200 amps isn't getting used so it's just like it wasn't there.
Brian
Exactly. I will have the potential ability to put up to 120A into my batteries, but most of the time they'll be charging at much less than that depending on their SOC. When using solar the high-power appliance should be used after the batteries are on float, so load-management is the key. Charging the batteries is always the priority.
John
I'm glad this thread took a turn toward solar. I got my grounding questions answered along the way, and now we get to talk about important alternative energy stuff. We're a year and a half off grid at the end of this month. Other bus nuts can do the same.
Jim
I was wondering if charging with solar while there is possibly significant draw on the batteries affects battery life? Does the inverter run off the batteries or more off the solar panels (almost directly)?
BTW, Kenworth, White, Frieghtliner all had positive ground (DC) systems "back in the day". I understood it had more to do with reducing body/chassis corrosion somehow.
Quote from: krank on July 16, 2014, 05:40:43 PM
I was wondering if charging with solar while there is possibly significant draw on the batteries affects battery life? Does the inverter run off the batteries or more off the solar panels (almost directly)?
The connections to the batteries from the panels' charge controller, and the connection from the batteries to the loads, are one and the same. In effect the load is driven from the CC's output, but via the batteries. I.e., if charging at 50A while drawing a 50A load, the batteries' net loss or gain is zero; if charging at more than their load drawn out, the batteries will still be charging, albeit at a slow rate, and if the charging is less than their load the batteries will be slowly depleted. Battery life is dependent on depth of discharge, number of cycles, plate sulfation, and to a lesser effect their rate of discharge (subject to Peukert Effect and all that good stuff). However, battery life should be longer if charged by solar, for the simple reason that the batteries should get fully charged almost every day within a few hours, and they are constantly getting a top-up charge during the day. For this reason I'm hoping that I can get a long life from cheap basic FLA batteries like golfcart or similar, but I plan on having a DOD of no more than 25 to 30%. If I can get eight years of useful life from my batteries I'll be happy.
Maybe I should tell folk that my bus has radiated-thermonuclear charging powered by off-site fusion of helium atoms. Yeah!
John
"BTW, Kenworth, White, Frieghtliner all had positive ground (DC) systems "back in the day". I understood it had more to do with reducing body/chassis corrosion somehow."
This is pretty much correct but backwards. There is always galvanic corrosion potential in an electrical connection with dissimilar metals. Positive ground systems tend to save the copper wire and sacrifice the chassis. Negative ground systems tend to save the chassis and sacrifice the wire. I never really thought about it much, but telephone systems use negative 48V for the subscriber loop, that is positive ground to keep the copper wire from corroding. In a vehicle it's easier to fix a wire than a chassis ground point.
Brian
Quote from: bevans6 on July 17, 2014, 04:46:23 AM
"BTW, Kenworth, White, Frieghtliner all had positive ground (DC) systems "back in the day". I understood it had more to do with reducing body/chassis corrosion somehow."
This is pretty much correct but backwards. There is always galvanic corrosion potential in an electrical connection with dissimilar metals. Positive ground systems tend to save the copper wire and sacrifice the chassis. Negative ground systems tend to save the chassis and sacrifice the wire. I never really thought about it much, but telephone systems use negative 48V for the subscriber loop, that is positive ground to keep the copper wire from corroding. In a vehicle it's easier to fix a wire than a chassis ground point.
Brian
Lucas used that similar logic decades ago. My '62 MGA had pos ground but by the time I went to work for Norton motorcycles in 1972, we'd gone to neg ground (and Lucas was supplying all their new-OEM components in neg ground).
Quote from: Iceni John on July 16, 2014, 08:57:06 PM
Maybe I should tell folk that my bus has radiated-thermonuclear charging powered by off-site fusion of helium atoms. Yeah!
John
:o ;D
Haha. Just don't tell your insurance agent!
Reason I was asking is there is a difference for us in the shop when testing, say an ABS system using a battery vs a battery charger. Using a small 10A battery charger will not power the ABS system properly and we have to use a charged battery(don't know why). I was just wondering if it would make any different to special electronic devices or systems using solar but I assume the controller would take care of that?
Quote from: bevans6 on July 17, 2014, 04:46:23 AM
"BTW, Kenworth, White, Frieghtliner all had positive ground (DC) systems "back in the day". I understood it had more to do with reducing body/chassis corrosion somehow."
This is pretty much correct but backwards.
Brian
Yeah, seemed that way to me! ;D