As part of my prep for my first long trip with my bus, i was working with the house bank. I installed a digital display hooked to both the house and bus/start batteries. While watching the display, i have discovered that the house batteries are not getting charged while driving!
I am leaving either Fri or Sat, and i would like to get the house batteries taking a charge while OTR. My bus is sitting outside, and it is not supposed to get above zero for another 3 or 4 days, so i can't do anything to elaborate.
I have searched for the answer to this problem and read the archives at the other board, and read different web sites. While they all give good info and theory etc, not one of them gives a diagram showing how to hook up the needed equipment to handle this.
Is there a diagram anywhere showing what wire to take from the generator (or where ever i start from) and how to wire in a isolator or solenoid? Can you tell i am not an electrician? I can do the work, if i just know what to do.
My brother gave me a Sure Power isolator, but it is rated for only 70 amps max. Can this be used to control charging the house battery, or is it too small? If it is useable, where do i get the wire to attach as input to the isolator. This is on a 4104, neg ground.
I will greatly appreciate any help,,, even if it is only a tip on how to "hot wire" the house battery while driving to get it charged. I just can't get it into my head how the bus generator can know when the house battery is fully charged etc, and cut off the supply.
I just checked the temp outside, it is -22.2 F and still falling, so as i said, my outside time available for working on the bus is short. Thanks for any tips or advice.
Hey John Z . Till you can find out how they normally get charged, You could start the bus and then hook up a set of jumper cables between house and start batteries.
Not a bad idea,,, the distance is too far for jumpers (house batteries are way up front), but perhaps a run of 12 ga romex? Do you think that would that work?
The romex will work as long as you don"t have big load on the house batt.
Thanks. It should be ok to get by with then,, only running some fans, a couple lights, stereo, and the big draw is the furnace fan, but i usually shut that off while otr and just use the ceramic htr. Thanks again for the suggestion.
Boy,I sure hope your going someplace warmer. It"s going to get cold here in S.A
Boy, I sure hope your going someplace warmer!
Yep, thats the plan,,, head south! First fuel stop will be at 600 miles at Kansas City, MO. From there we will take off toward Ark, but be chking the weather forecasts to see where it is warm! Maybe Louisiana, maybe TX. Would like to swing through KY and TN if it works out to. I am just sick of the cold winters, and this is my second to last one i will spend here. Bringing the bicycles, and am really looking forward to putting some miles on them.
Where is S.A? BTW, just chked and it is -24.3 F and still dropping!!! Man that sucks!
Small point, but before you go connecting jump leads or cables are you sure the house batteries and start batteries are even the same voltage? They often aren't. Apologies if this basic question seems insulting but better to make sure you have checked than have you damage your batteries and maybe yourself
Jeremy
Do NOT run 12/2 romex without putting fuses in the line. 20 amp max. I am building mine and it looks like yours, a continious duty soliniod to tie the coach and house batteries together. I am controling it with a oil presure N.O. contact. This will not be heavy enough to tie the batteries together to start the engine if it is dead. I put a MCI disconnect between them for this. Make sure of the voltage of both banks. 12 volt coach? 24 Volt start? Where are you located at? There may be someone near by to help. I like looking at others buses. Goodluck Tom Y
Sorry guys. I meant the post above to go to LeagalEagles postl Tom Y
Charging a house bank from the start bank with a 12ga wire???? What am I missing? If it has a high amp alternator, like an MCI (270A) then the current going through that charge wire could be as high as that. I'm probably missing a piece of the puzzle. I know you guys wouldn't suggest connecting two battery banks with a 12ga wire.
The connecting cable should be at least 2/0, bigger if it's a long run. The solenoid needs to be rated for a least what the alternator puts out, which is probably alot more than 70A. For a simple charge system, you can just run a charge cable from the start batteries to a manual battery switch then to the house batteries. After you start the bus, turn on the switch. The solenoid does the same thing, just automatically.
Ross
OK Ross, so your saying i can just run a piece of 2/0 wire between the positive posts of the bus battery bank and the house battery bank, with a switch in between? Sounds simple enough. Yes, both banks are 12v. Would it be worth the extra length of cable to bring it into the driver compartment with the disconnect switch? Or should i just leave the cable as short as possible? Bus bank is in rearmost bay drover side, and house bank is is bay right behind front axle driver side, so the driver panel is right above the house bank.
I wouldn't bring that large wire and switch into the driver's area.
I used a 200 amp relay to connect mine. Works well. I'd recommend you do it that way. Then you can put the switch in the driver's area.
If you don't get it by the time you leave, you're welcome to drop by on the way past the cities (not too far out of your way) and I'll help you get it figured out. Unfortunately I don't have a shop to pull it into but I've worked in the cold before. We could make it work.
Do you have a relay?
If you need a switch, or a fuse/holder, I may have it here, of I can get it from Waytek in Chanhassan. Might be able to get a relay from Grainger in Plymouth, too, if you don't have one.
Craig, that is an incredible offer! Thank you very much, but i would hate to drag you out in the cold so early on a Sat morning. But using your advice i know what i need to do and will try to track down those parts. I like your idea about the relay. I believe there is a Grainger in Duluth, if not, i know there is a Graybar that should have them. I may not get it all hooked up before i leave, but it will give me something to do when i get somewhere warmer, while the brats are cooking! I sure would like to see your bus,,, i still remember the pics you sent me about the pex fittings. It looks like you are doing one hell of a job on it! Maybe it will be warmer on our next time through. Thanks again.
I think the size of the relay depends on the size of the house battery bank, not on the size of the alternator.
On DML I had four 8-D batteries. Although I had a 150 amp capacity charger, the most amps I ever saw the charger putting out was about 70-75. This was when I had run the batteries down pretty low. Generally it was in the 40-50 amp range. I personally believe the 70 amp isolator he has is adequate unless the battery bank is significantly larger than four 8-D's, and the wire would not need to be larger than six guage.
Many people make the mistake of calculating the charge circuit components based on the capacity of the alternator. It really needs to be based on the capacity of the battery to take a charge at the highest acceptance rate without boiling the battery.
Although it may exist, I have never seen a house battery bank capable of accepting a 200 amp charge.
Richard
tom and gumpy,
could either of you post a picture of your setup.
I have an eagle, so its 12 volt system for house and start. I'm trying to understand if you can use 1 solenoid for both the charge connection and to help jump start if start batteries get just a little low on mine. (Again, since the are both 12 volt)
Gumpy for example, you have a 200 amp solenoid. Is that plenty enough rating if you have a 270/300 amp alternator?
My bus says the solenoid is a jump start relay. I was thinking as long as I energize the solenoid while the engine is running it would allow my house batteries to charge.
I'm not sure how to tell the amp rating of my solenoid. I did not build my bus just bought it. You can see my pictures of my solenoid under my posting for Jump Start Relay. I guess I need to determine if it is a continuous duty solenoid too.
Any thoughts appreciated. Its a little cold here in Nashville so I'll wait a few days before I have some of my own answers. Just looking for as much input as possible. I thought if I have some low amp start relay only, I would change it out for a heavy duty solenoid and get all the benefits I was looking for.
Evan in Nashville....if anybody is close by, feel free to stop by and look and ponder...
Richard, i went to a web site for a distributor for the Sure Power isolator. After looking over their info, i don't know if it will work on my bus or not. They mention that whether or not you can use an isolator depends on whether your alternator is externally or internally switched. Hell! I don't even know if my 59 04 has a generator or an alternator! Simply wiring the two banks together with some sort of switch to connect or disconnect, i can understand. I would be comfortable putting that together. I do not have the knowledge to wire in the isolator.
I understand. It definitely will work, but you really need to stop at Grumpy's or someone else to get it hooked up. For the interim, the contactor will work fine.
Richard
BTW, the older 4104's had a generator. The newer ones had an alternator. You can easily tell it you like. If it has a removable band, and under the band are large brushes riding on copper commutator bars, it ia a generator.
Quote from: John Z on February 04, 2007, 09:09:41 AM
Richard, i went to a web site for a distributor for the Sure Power isolator. After looking over their info, i don't know if it will work on my bus or not. They mention that whether or not you can use an isolator depends on whether your alternator is externally or internally switched. Hell! I don't even know if my 59 04 has a generator or an alternator! Simply wiring the two banks together with some sort of switch to connect or disconnect, i can understand. I would be comfortable putting that together. I do not have the knowledge to wire in the isolator.
Another way to tell if it's an alternator or the original Delco generator is if it has 4 connectors on the side, (1 huge for battery connection and 3 smaller connectors), it's a generator. Also if it has a filter on the back end... it's a generator.
Here's a photo of a generator:
Quote from: LegalEagle82 on February 04, 2007, 09:09:06 AM
Gumpy for example, you have a 200 amp solenoid. Is that plenty enough rating if you have a 270/300 amp alternator?
My bus says the solenoid is a jump start relay. I was thinking as long as I energize the solenoid while the engine is running it would allow my house batteries to charge.
That is plenty large. The most I've ever seen going into my batteries off the engine is just over 100 amps @ 24v when the relay is first turned on, and then it drops very quickly to around 50-60 amps, and then drops as the batteries charge through the day of driving.
Trace recommends maximum charge rate at 1/5 the battery capacity. My bank is 440 amp hours @ 24v. That comes out to 88 amps max. This is used to calculate the inverter charger setting. I've never seen a continuous charge off the alternator above that, and again, only a short term (less than 3 minutes) above that when first connected.
If my bus batteries should get discharged and I needed to augment them with the house battery, I'd engage the relay, and let it sit for awhile before trying to start. This gives the coach batteries a chance to come up in charge prior to engaging the starter. That way, you are not drawing huge loads off the house bank during starting.
While relays and solenoids are great, for the people that know how to troubleshoot them. Wouldnt a simple marine type selector switch be better for us non electric types? A 4 position switch rated at 350 amps continuous is less than $50 at marine supply stores.
John,
If you come to Ark. I'm at the KOA, North Little Rock. Should be here at least a couple more weeks.
Bill
Dallas and Richard, thanks to you guys, i am pretty sure i have an alternator! Cool! I checked it and no removeable band, and only three terminals - the large output cable, one marked "relay" and one marked "F", and above the F is marked "Do not ground." Not sure this helps me right now with getting the house bank charged, but it is good info to have in my book.
Bill - unreal! We were just looking at the AAA Arkansas book last night for a camp ground for the second night out. We may just look you up if for no other reason than to say "Hi." If all goes according to our rough plan, we would arrive evening Sun 2/11.
The relay i can understand and wire up,, but was looking at Grainger catalog and sure can't tell which one to buy, but am sure they can help me pick that out. The 12v switch to trigger the relay should not need to be anything special thouigh should it?
Thanks again to all you guys,, sure do appreciate the help.
Quote from: jjrbus on February 04, 2007, 11:12:10 AM
While relays and solenoids are great, for the people that know how to troubleshoot them. Wouldnt a simple marine type selector switch be better for us non electric types? A 4 position switch rated at 350 amps continuous is less than $50 at marine supply stores.
The advantage to a solenoid is location, you can put it close to the batteries. If the batteries are in the rear and you want the switch up front it will take a lot of heavy cable. Another advantage is that the solenoid can be controlled in such a way that you can't forget it (by wiring into the ignition switch for example).
Len
John, I would suggest a fuse at one battery connection and the switch on the other end, both properly sized for the wire used. Easy to cut off the juice in the cable in case of an emergency.
When charging my house bank, or my 2- 8d coach batteries, the current draw routinely exceeds 250amps. But no matter how large a battery bank I have. The main issue is what You intend to do.
If you have an inverter, microwave, a/c unit or any high amp draw appliance, or battery bank the total amp draw will be alot, most likely all the alternator can put out. This will be the total of the batteries being recharged, as well as the total load of the electrical use.
To small a wire and fuse and you will have more money in blown fuses, and a useless system.
If on the other hand you have really small electrical draws and battery bank that draw no more than a #6, wire can handle, then by all means you COULD use small connections.
We all use our busses differently.
Good luck with your choices.
Bill
JohnZ,
I went thru this some time back as the isolation relay whcih connects house and coach batts, while OTR stuck in ( closed ). It was a intermittent duty relay, not intended for use over 3-5 minutes. This would work in a horm application.
I was looking for a 200 Amp Continuious Duty Relay and had one in my 5-C. The coach air cond. had been removed, however the 200 Amp relays were in the front bagg bay.
Sorry I have not been around a 41XX, so my help stops here.
The idea is the bus charges the two coach batts with 24Vdc, you connect an equalizer to derive 12Vdc (equally across the 2 coach batts, if not the weaker batt will take all the load (less internal resistance) The relay connects the this derived 12V to the house batts. Just run the 24V relay coil wire to the voltage regulator. When the coach is running the relay connects the two coach and house batts.
I would short term pull the coach batts out and into the house or heated space. Clean them off. Bring them up to 65 - 70 Deg. It will take 8 - 10 hours due to mass. Heck put them in the bath tub, clean them up right, Your wife will understand,,,, I would be sleeping the bus if I did that..
Charge the batts invividually with a large cap. 12V charger.
Install just before you leave or decide to start up. Clean the cables as well.
I will try to gin up a sketch of this and provide later. I think that Wrico has some wiring digrams, but I might be wrong
Best of Luck and hope this helps.
Gary
I just picked up a 24 volt continuous duty solenoid (relay) for joining the house and start batteries from Gainger. It was $70, which was the best price I could find it for. I have a DPDT switch mounted near the parking brake knob. It'll allow me to connect the battery banks automatically (when the 'not gen' light goes off and the HVAC blowers will come on), manually, for jump starting off the house batteries, or off, to keep the batteries separate.
This solenoid is also available in a 12 volt version. If you need the part number, I can get it for you.
The only question I have is where the connection that allows the HVAC blowers to turn on. I haven't been able to locate anything in the manuals. Thanks.
David
David, what was the Grainger part number? How many amps can it handle?
It handles 200 amps continuous. Here's the link http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611756367 (http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611756367), Grainger part number 6C025. The hardest part of the whole thing was getting an account set up (I'm not a business). I'm glad I did, though, as there are lots of items that'll be helpful for this project.
David
Thanks David, one of those with a 12v trigger is just what i need. Now i just need to figure out and decide how heavy of wire to use for running between the battery banks. Just to show you how poor i am at electrical theory; until your post, i did not know that a solenoid and relay were the same critter! Thanks again.
Gary, i apprecitate your advice, and if you do get time to work up a drawing, that would be very helpful to me. Thanks.
Quote from: John Z on February 05, 2007, 05:33:29 AM
Thanks David, one of those with a 12v trigger is just what i need. Now i just need to figure out and decide how heavy of wire to use for running between the battery banks. Just to show you how poor i am at electrical theory; until your post, i did not know that a solenoid and relay were the same critter! Thanks again.
I'm going to recommend you use 4/0 welding cable to do your connections. With 12 volt banks, you'll be running higher amperage. 4/0 welding cable ought to be available locally at a welding supply shop. It won't be cheap, though. Have them crimp and solder ends on it,
or see http://www.gumpydog.com/bus/MC9_WIP/Electrical/Batteries/batteries.htm (http://www.gumpydog.com/bus/MC9_WIP/Electrical/Batteries/batteries.htm) for some home made tips.
Quote from: John Z on February 05, 2007, 05:33:29 AM
Thanks David, one of those with a 12v trigger is just what i need. Now i just need to figure out and decide how heavy of wire to use for running between the battery banks. Just to show you how poor i am at electrical theory; until your post, i did not know that a solenoid and relay were the same critter! Thanks again.
I think a relay is for smaller loads, a solenoid is for big DC loads, and a contactor is for large AC loads, but I could be wrong. One thing I forgot to add is that I also added an Intelletec latching solenoid (called a "Big Boy" 200+ amps continuous, 1200 for something like 30 seconds) to act as my main disconnect. I can activate it via a momentary DPDT toggle switch also mounted next to the parking brake control. I kept the original MCI disconnect as in case of some sort of malfunction of the solenoid. I added one of those small Bosch cube relays to prevent the solenoid switch from being activated and disconnecting the batteries while the bus is running. Doing this can damage/ burn out the alternator, from what I've been told.
Here's a link to a 12 volt version: http://www.partsguy.com/cgi-bin/PartsGuy/586-108111.html (http://www.partsguy.com/cgi-bin/PartsGuy/586-108111.html). I'm using 3/0 wiring between the battery side of the Intelletec solenoid and the battery 'bridging' solenoid. The main cable from the engine compartment to the batteries is 4/0, I believe. I think that for the few times I'll be jumping from the house battseries to the start batteries, and the fact that it'll be about 3' in total length, I should be fine. One thing about the White-Rodgers 586 solenoid is that the terminals are 5/16" instead of the 1/2" on my Intelletec, so you'll need to keep that in mind when getting a cable made.
The Intelletec "Big Boy" disconnect is nice because it keeps one from having to open the battery compartment door and disconnect the power. I didn't like the fact that doing this made it real obvious to anybody watching how to switch the power back on in my bus. Being that my MCI doesn't have a dead bolt, I felt that a somewhat hidden switch inside would take care of this problem, as well as be MUCH more convenient. They're kind of expensive, but I got mine on the e-place for less than $75. There's a 12 volt version listed at the moment. My 24 volt models works well, so far, and makes a huge "CLUNK" when being activated. It's huge and makes that White-Rodgers combiner solenoid look wimpy, but I'm sure that will work fine too. Good luck with it.
David
Edited after reading gumpy's post... on a 12 volt system, 4/0 would probably be better. I'm just not using it 'cause it's so expensive. I went to a local alternator/ starter rebuilder that I know somewhat and got him to make up my cables. Actually, he was busy and showed me how to crimp them with this huge crimper (looks like a big bolt cutter almost) and he inspected my crimps. Like was mentioned, it's not cheap. I think I'll have between $175-200 in battery cables, not including what's being run to the distribution panels, converter/ charger, or Vanner equailzer. As another note, I found the local Boater's World to have very good prices on their big cables. Their duplex and triplex cables were pricey, but I think they have down to 2 or 0 awg for a very reasonable price.
There was a post I did on jumper solenoid, but disappeared when the board was changed. I used two 150 amp continuous duty solenoids (look like the old Ford starting solenoid) since I have the 300 amp Delco 50DN 12v. I have them strapped together with a heavy gauge strap so they work to handle the possible 300 amp and for intermittant starting assistance. It is wired to the dash with a on-off-on toggle. One position works with the engine side through the ignition switching. So if the deep cycle batteries are dead can switch it over and have the engine alternator charge them back up. The other position is wired through the deep cycle batteries so if the starting batteries are dead can use the gen with the inverter/charger to charge them up. Sort of weird, but if the deep cycles are way down, the inverter/charger will not activate until it gets a boost of 12v. I have had both sets of batteries down for one reason or another and am glad of both position possibility. They have been 100% reliable even with me leaving them activated for several weeks a couple of times. Good Luck, TomC
John, Heres what I did. I used a Napa ST95 12 v cont. solinoid, $30.00. I set this on a normally open oil presure contact. This is to charge my coach bettery only. I used #6 wire with a 50 amp circuit breaker. My batteries are behind the switches, 1 switch to diconnect engine bat. 1 switch to tie engine to coach, and 1 switch to disconnect coach bat. I have a couple 24v solinoids and relays to part with and will put them on the trade section. Goodluck, Tom Y
Tom, that looks like a really nice setup, but might be a bit more involved than i am aiming for. Where did you get those switches? Could they be used for battery disconnects? My bus is needing disconnects for both sets of batteries.
Today i stopped at Grainger, and they do not carry a solenoid heavier than 100 amp that has a 12v trigger. So i am really no closer to having a plan for this problem.
So how does one calculate the draw that the house bank could have? If i put 3 deep charge batteries in there that are each rated at 850 amps, what kind of draw would they have when they are roughly half discharged?
Thanks again for any help.
John, The one I bought from Napa is a 200 amp 12 volt. You may want to try them. The disconnects came from Ebay a MCI part. I have a couple more, will list on this board some day. My bus had one on it when new but it was 24 v. Tom Y
Quote from: John Z on February 05, 2007, 06:27:41 PM
Tom, that looks like a really nice setup, but might be a bit more involved than i am aiming for. Where did you get those switches? Could they be used for battery disconnects? My bus is needing disconnects for both sets of batteries.
Today i stopped at Grainger, and they do not carry a solenoid heavier than 100 amp that has a 12v trigger. So i am really no closer to having a plan for this problem.
So how does one calculate the draw that the house bank could have? If i put 3 deep charge batteries in there that are each rated at 850 amps, what kind of draw would they have when they are roughly half discharged?
Thanks again for any help.
John, you can google white-rodgers 586 12 volt solenoid. This place http://texasindustrialelectric.com/relays.asp (http://texasindustrialelectric.com/relays.asp) has 'em for not much more than Grainger. Go to the website I posted and search the page for 586 and you'll see it about half way down.
David
You might also check eBay item # 150087398878. Good luck!
This thread has morphed into a lot of comments on solenoids so I might as well add mine.
The word solenoid refers to the method used to move the electrical contact. When used for DC switching it is a cheap, brute force method instead of using an ezpensive DC contactor.
There are two ratings on every electrical switch. One is the amount of current the contacts can carry and the other rating is how much it can switch. The switching rating on AC is dependent on whether the load is inductive or resitive as well as voltage. On DC it is dependent on voltage and the ability to break the arc. Expensive DC contactors use magnetic blowouts to break the arc. Solenoid switches use a strong spring and a big gap, which is the reason for using a solenoid instead of an eletromagnet and a flat armature.
The usual current carrying capacity of a switch is three or four times the switching capacity. This is how you can run your starter through a 200 amp solenoid to your house batteries. Just don't try and switch it with the starter cranking.
A word of caution on putting any kind of switches in parallel to carry more current. They will not switch at exactly the same time. If the voltage and current are high enough to cause contact welding, the one that switches first will have stuck contacts.
OK, i looked at the 6v golf cart batteries at Sam's club. 225 amp hours. So if i buy just 2 of them for now, cable them to make a 12v unit, will that give me about 200 amp hours of use before i would need to charge them?
John Z, you will get better results if you think in terms of 1/3 of the rated power being available between recharges when you are boondocking. This will give you some decent service from your batteries.
You can take more out of your batteries, but the more you take, the more disappointed you will be with your system. The batteries you are looking at are rated about 1 1/3 KWH each, so using about 1/2 KWH between recharges would be a good target.
Since they weigh about 65 pounds each, you will have about 4 KWH you can take out of 500 pounds of batteries between recharges, even though they will hold around 11 KWH.
If you were to compare using the power for running an electric heater with using propane to produce heat in a furnace, you would use most of one 14 ounce bottle of propane. Using electricity to heat or cool while boondocking is usually a losing proposition in your RV.
For what it's worth.
Tom Caffrey
I agree with Tom C's comments and there is alot of information within the old Xantrex inverter installation manuals, which are still avail online at their web site. Need to look maybe in the archives but the old unit 2012 again going from my head is there with much more in depth info on cable sizes, batt types, batt recharges, and how much to deplete batteries between charges. Very in dpeth but all there. I found the diagrams numerous and helpful. New manuals all without this info, lawyers doing I guess.
Gatta get to work, I will try to supply the site later.
Only 20 f above with 1-2 " , so I am not complaining.
Gary
If you go to www.bluesea.com and do a search for blue seas 9112, you will find an automatic switch that will charge your house bank from the engine while running, charge the coach batteries from the inverter, automaticlly, and you can flip a switch to combine both banks for emergency starting power and a little light on the dash lets you know that it is all working like it is suppose to. If you want one, I have a couple that I will sell. e-mail me.
OK, i am getting a 4/0 cable, and i picked up a continous rated 200 amp solenoid. My question is where do i attach the cable? Does it run from the bulkhead terminal that the start batterie's positive cables are bolted to, or should it attach to the positive terminal of one of the start batteries?
And where should it go to on the house batteries? I am planning on leaving Fri night after work, so would really appreciate an answer so i can hook things up before we leave.
TIA
John Z, it has to go from pattery positive to battery positive on as short as possible of a run to get the benefit of the starter boost capability when the starter batteries become very discharged.
This is going to depend on where your batteries are mounted.
Tom Caffrey
Thank you Tom. I was not sure if it would make a difference whether at the bus/start battery end, it was attached to the battery post or to the junction block mounted on the bus.
How about the neg cable on the house bank, should that be as large as the positive cable?
Gosh i will be glad to have this installed and working.
John,
If your house batteries are closer to the positive cable bulkhead lug from the coach batteries than they are to the coach batteries, that would be just fine. If they are closer to the coach batteries, then hook it to the battery positive post.
Due to the size of the cable, it may be better to mount a separate bulkhead stud if you can't attach directly to the positive post. You can get these from Waytek. They also have pass-thru bulkhead studs, which work well to go through a panel.
The negative cable should be the same size as the positive and preferably should go to the same grounding lug as the coach batteries. That may not be practical, however.
Here's a few photos of the coach battery side of my crossover connect.
Here's the other one....
Thanks much Craig. The house batteries are almost 18 feet from the start batteries, so at 4.00 a foot for cable, it looks like it will have to go to ground right at the house bank. I do appreciate your help again! We were commenting last night at all the things that had to happen just right in order for us to be able to leave tonight,, and it looks like we are going to make it!
John Z, at 18 feet of distance, which means 36 feet of total conductor, you will likely be beyond any recommended distance for a large inverter. And the starter will draw more when cranking than an inverter.
Perhaps you will be able to figure out how to get a better setup.
Tom Caffrey
Thanks everybody for all your help. The guy at the welding shop talked me into 1/0 cable, said it will handle 350 amps over 50 feet. I have it all hooked up, the bus is loaded, it is about -8 and we are out of here!
Highly recommend you go with 4/0 or 0000 cable. There is no such thing as too big of a battery cable. A 1/0 just seems small to me. Good Luck, TomC
Quote from: John Z on February 09, 2007, 10:03:27 PM
Thanks everybody for all your help. The guy at the welding shop talked me into 1/0 cable, said it will handle 350 amps over 50 feet. I have it all hooked up, the bus is loaded, it is about -8 and we are out of here!
It appears, according to Jock Fugitt's information, that a 1/0 cable at 200 amps for 50 feet will have a voltage loss of 1.22 volts. That's 10% on a 12 volt system. And at 300 amps, will lose 1.83 volts. At 100 amps, the loss is 0.61 volts.
This can be significant. That means your batteries won't ever get fully charged if you're charging off the alternator. This could eventually lead to premature failure of the house batteries.
It's unlikely you'll ever be putting that much current through it. I wouldn't expect to see more than about 100 amps charging off the alternator, and only for a short time.
John, I think you will be just fine.
Some fail to consider that as the battery gets up to full change the current continuously decreases to the point that only a few amps will be flowing. There will be little or no voltage drop under these conditions.
Richard
Richard, i am in agreement with you. He showed me the chart they have in the shop and use to make up the cables. Actually, for my alternator he said i could have used 1 gauge wire. So using the 1/0 is overkill. Also, i am not running 50 feet of cable, only 20 feet. It has worked just fine so far. I must say, those golf cart batteries do seem the way to go. I am sure i will add another pair of them to the house bank before my next trip. We are in Little Rock, Arkansas tonight. Rain all day today, but temp is 55 at 8:30 at night. And after driving in -16 the first night out, i gotta say this feels just wonderful! Thanks to everyone for your help with getting me through the hook up of the solenoid etc. It works better than i had hoped. I guess now i need to work in the equalizer charger.
i ran battery cable from bus batt to a solinoid continuous duty to the house batt, have a swithcc in the driver area, has worked well for 20 yrs. had to replace the solinoid one time. romex is not the way to go, too light and its solid wire.
Frank Allen