House battery and solar panel sizing

[PP]

Can we re-iterate the math on the batteries again? If I'm not mistaken a T105 6V battery is approx 115AH. To push up to 24V using 4 of them, you still only have 115AH----Correct? It's just now at 24V instead of 6V. The same arrangement, which is what I currently have on the house side at 12V is giving me approx 230AH. Am I figuring this right? To get 460AH at 24V will take a lot of batteries.... I think....
Will
I've been know to be in the shed needing an edge. (Translation-Not the sharpest tool in the shed)

[neoneddy]

https://www.thesolarbiz.com/trojan-t105-golf-cart-6v-225-ah-battery.html?fee=1&fep=36&gclid=CjwKCAjw2NvLBRAjEiwAF98GMYOXI434vu6mGJ1DzXJrO03vLH9TLUnK3gJoYoi2tliVvpZXbrQnyxoC7IAQAvD_BwE

The battery is 225 ah .   You are correct, putting batteries in series builds voltage.  This is good for increasing efficiency and reducing line loss.  To build a ~460 ah 24v battery bank it would take 8 batteries in a 2x4 configuration.

[PP]

https://www.thesolarbiz.com/trojan-t105-golf-cart-6v-225-ah-battery.html?fee=1&fep=36&gclid=CjwKCAjw2NvLBRAjEiwAF98GMYOXI434vu6mGJ1DzXJrO03vLH9TLUnK3gJoYoi2tliVvpZXbrQnyxoC7IAQAvD_BwE

The battery is 225 ah .   You are correct, putting batteries in series builds voltage.  This is good for increasing efficiency and reducing line loss.  To build a ~460 ah 24v battery bank it would take 8 batteries in a 2x4 configuration.

Thanks for clearing that up for me.

[windtrader]

Solar can drastically reduce your generator run time and keep your batteries floated but most people can't live without a generator

Exactly my plan. The bus has an 8Kw genset and that remains a key component of the electrical system. The less it is used, the better. Last weekend I nearly got into a punch up with some A-hole bitching about the diesel fumes from the genny early in the morning. Then I started the bus as well and he really went off. LOL. The more flexibility I have to run the gen if needed the better.

[windtrader]

If the stated capacity in Wh uses a SOC of 1.75v then how does one estimate the partial DOD capacity. Like how much Kw is available at 30%, 40%, 50% DOD?

[Geoff]

I'm sorry to interject a note of reality but ............

Solar is a lifestyle choice, not a power source.  If you are willing to drastically alter your lifestyle you MAY be able to put sufficient solar panels on your coach to live off them but I stress the word "MAY".  If you are just wanting to keep the batteries topped off while the coach is unused then no worries, solar will work. 

If you are serious about solar then its all about the watts.  Figure out your power usage.  There's no magic.  800 or 1000 watts of solar on a coach is huge but that's the kind of numbers you will need and in my never to be humble opinion you'll still need a generator.  There's no point obsessing about battery capacity if you don't have enough watts coming out of the panels to recharge the batteries.  And you've only got about 6 hours of truly useful solar input each day.

Been there done that.  Solar can drastically reduce your generator run time and keep your batteries floated but most people can't live without a generator.

Listen to Bob- do you want a bus to travel in or a freak show with a dozen solar panels?  I have traveled a lot and I can't recall a bus or RV with solar panels on the road. That is crap for traveling.

--Geoff

[windtrader]

No plans to make the bus look like it is full of panels up top. Researching if a couple might help keep the house battery bank topped off during the day. Main thing now is to finish the math if the new bank of 4 6v 230Ah golf batteries connected in series is a solid base of energy storage.

If I'm reading correcting one just takes the stated full storage and can divide using DOD to compute the usable energy. For example, the 24v 230Ah battery bank has max energy storage of 24X230=5,520 Wh. At 50% DOD the available energy is 2,760 Wh. Based on our usage profile, this should work fine to get through a day of electrical consumption.

Main pending decision is correctly sizing and selecting the right golf batteries.

Who knows - if the new battery bank does a good job and a short generator session gets them topped of each day, I may skip the solar. Always better to plan for future upgrades early rather than later.

Don

[neoneddy]

These are the ones I have.

https://www.batteriesplus.com/battery/rv/deep-cycle/6/sligc115    Ask for the 10% off  online discount in-store, they'll give it to you plus some because  they get the money vs it going to corporate. Worked for me anyway.  I even said these are for a new application where there is no core to possibly exchange, they waived the core charge on 4 batteries, saved me $100 right there.

A generator topping them off each day would probably do it, but in my humble opinion, the future is clearly PV in some form or another.  Even if you only run 200 - 400 watts to start, that  will keep everything charged when not in use (not sure if you're a full timer or not).

http://www.aimscorp.net/Power-Inverter-Charger/   I run one of these for now... they have an auto gen start when voltage gets low.  Eventually I'll go Victron, but I ain't made of money quite yet.

[Dave5Cs]

Don just a suggestion on starting the genny in the morning. get or make a stack pipe for it. Pipe venturi for air at the bottom and up the diesel fumes go into the air instead of accumlating at the ground and neighbors area.

Second if starting the engine to air up hook a shop compressor into your air system with a shutoff valve on the in line. Turn the compressor on before you leave you will fill the system without needing to start the engine until you leave. HTH
Dave

[bobofthenorth]

Bob, 800 or 1000 watts really isn't that much.   I've got 2kW, and I would have more if I had roof space for it.   With solar now down to not much over 50 cents a watt (I paid 79 cents, and that's now high by current pricing) it's almost cheaper to carpet the roof with PV panels than to build a tropical roof over it for insulation!   To complement my PV I'll also have two solar water heating panels  -  heck, if I'm getting my electricity for free, why not also heat my water for free?

With enough PV power I really don't feel I'll need to compromise my lifestyle.   I'll have a 12K minisplit in the front and a small window A/C in the bedroom, I'll run my tools and toys just like now, I can use a microwave and an induction cooktop, so it will work for me.   I'm not an energy hog even at home  -  I lived for many years in a little old house with only a 20 amp feed (yes, twenty!), and two of us managed just fine with it.   I intend to not be anywhere stinking hot in the summer or bloody cold in the winter  -  that's why buses have wheels!   No more brass monkey weather for me.

John

Absolutely John, with 2K watts you can approach "normal" living.  You're dreaming if you think you'll run much AC off that but I'll believe the rest of the electrical systems within reason.  The reality is that most solar enthusiasts think that 500 watts is a lot of power when its actually mainly a joke.  If you managed to fit 2K watts on your roof then you must know how difficult that was and I'll go so far as to say that for most people by the time they get around existing roof obstructions its simply not practical.  More power to you (pun intended) if you made it work but solar newcomers need to hear a dose of reality early on and I'm the a**hole that helps provide it.

[buswarrior]

Listen to BoTN...

And you aren't going to top off your batteries with the generator, unless you like to listen to it run all day, trickling the critical last few amps into them.

The method for many is a blended approach.

From the battery charging perspective, the generator can do some heavy lifting, either on purpose, or as a bonus, when it is turned on for other purposes, and then the generator may be shut down when the other purposes are done. The solar panels do the rest of the job.

The peeps who run the generator "for a couple hours" to charge the batteries, don't get long battery life from that style of charging, as the bank does not reach full charge, and the generator wastes a bunch of fuel, may be running lightly loaded, another cardinal $in, and fills the air with stink and noise... pissing off the neighbours....

A boost from the generator, a little solar and a lot of silent running?

And if your geography or style of camping involves running the generator all day for the HVAC, then there is little need for solar other than storage battery maintenance?

One of the struggles in choosing a battery bank voltage is the commitment required to up-size.
12 volt banks can be built-up a pair of golf cart batts at a time. the 24 volt banks need multiples of 4 golf cart batts.

cable sizing, inverter wattage limits, space for batteries, solar panel parking spots upstairs...

Tell me again how this can all be called "camping"

happy coaching!
buswarrior

[neoneddy]

Buswarrior,

I've been considering using grid tie inverters in the bus plus solar so while parked at my house it helps offset energy use. Then you can also get solar tax credits because you have a house solar array, that happens to be on a bus.

Lastly I'm not too much of a crackpot but I like to hedge my bets.  If the world goes to hell, it will be nice to have something to live in that is somewhat self sustaining. Or any kind of disaster, more likely the big solar storm that will take out our grid.

I digress, it's not camping, it just a fun hobby that we tell.people is camping so they don't ask too many questions :-)

[windtrader]

OK, great discussion about this topic and feel sufficiently educated to at least get new house batteries.

Decided the following:
1) System is 24v and stays that way. Understand the higher costs when upgrading
2) Going with deep cycle 6v golf batteries (GC2). Four make a 24v battery bank.
3) Foregoing the high end brands like Trojan given how much cheaper Costco sells them.
4) After getting new bank going, will start a full energy use audit and optimize energy use (i.e. switch all lights to LED)
5) After a good idea of daily energy use, configure solar for charging battery bank.
6) Generator will be used as necessary to replenish the battery bank, knowing they won't be topping off hopefully getting through bulk and absorption stages via Vanner inverter/charger or bus alternator while on the road.

[buswarrior]

charging via the bus alternator going down the road is an unhappy experience, unless you have a proper regulator.

The stock regulator is dumb, and won't recharge a house bank properly. Same as every regular automotive alternator, they need proper external regulation and protection.

3 or 4 stage regulator, with battery and alternator temperature sensors.

Every way to care for a big house bank costs lots. Redundancy costs lots more...

That's why we roll our own!

happy coaching!
buswarrior

[Lee Bradley]

Windtrader have you considered L-16 batteries in place of the golf cart batteries?  Same foot print but about 4" taller and about 400 ah.