Are 9 batteries too many?

[Photobug]

My new class C RV has a 'chassis' battery to start the van, then the 'coach' battery is composed of 4 golf cart batteries. I believe the previous owner sourced all his parts from Walmart. When he decided to add solar he added 4 more golf cart batteries to a large Tupperware with 4 batteries. The 300 watts of solar on the roof go directly to this second coach battery pack and it is used to power a 1000w pure sine inverter. I believe the previous owner used this to power the 32" t.v. and maybe charge a laptop. Just in case that is not enough power, the normal coach battery pack also powers an inverter with AC outlets around the coach. In case there is not enough batteries around, the rig has a 4000W inverter. Up till now we have been happy with a single Costco 12v battery to power all our needs while camping, so feel the 9 batteries are a bit overkill, even though I now have a air conditioner and microwave to consider, but those are powered by the generator. I am feeling fat dumb and happy already.

• I have not even gotten in to explore the wiring to see the layout but I assume it is rigged so the house battery is charged when I am driving. So now my problems is I have more power than I know what to do with. Some of the other issues I have.
• I don't think the system is optimized solar to only the extra coach battery bank. Except for the solar controller which I have not explored or gotten to know yet, there is no meters or control for the battery banks.
• The second battery bank is taking up some valuable real estate. It occupies the space next to the spare tire and is only one of two good sized lockers on board. I'd like that space back.
• The roof is pretty much unusable with an A.C. and solar panels taking up most of the space. As I am looking at some maxtracks this locker would be a good space to store them.
• I don't think the second coach battery is properly vented.

I am looking for advice to optimize my resources on this rig. I have some ideas but looking for suggestions also.

• Remove both or just both or just one of the golf cart groups from the second 'coach' bank.
• Move the wire run from the solar charger to reach the primary 'coach' battery bank.
• Add some sort of battery monitor to the 'coach' battery.
• Take the spare 12v groups and add one to my trailerable sailboat and the other to my truck's 'coach' battery bank.

 

[Joe917]

Sounds like a badly made setup. The owner "needed" more power so he added more batteries. The fact that he made two banks and only has 300 watts of solar pretty much guarantees the batteries never fully charge.
Your plan is spot on, get down to one bank of 4 gc.
Get the solar hooked to the bank, add more solar (though you may not have room), Rule of thumb is 1 Watt solar for each A/hr battery.
Add a coulomb counting battery monitor (one that requires a shunt). A Volt meter is useless for checking batteries while in use.

 

[john61ct]

The ideal is one big House bank, circuit completely isolated from the Starter battery, at least when there is no charge source active.

2x 6V GCs in series makes one 12V unit.

Not a great idea to go past 2, maybe 3 of those in parallel to create a big bank, will shorten lifespan and wear unevenly.

Better to use lower voltage and higher Ah capacity units, 2V cells giving ideal flexibility.

But if you only want say 600-700Ah then the lower cost of using 3 pairs of 200+Ah 6V GC units will outweigh the disadvantages of a non-optimal layout.

An additional non-engine bank would only be good if needed for a specialized heavy-current load like winching, wheelchair lift, buffering an aircon unit etc

 

[vtsoundman]

....
2x 6V GCs in series makes one 12V unit.

Not a great idea to go past 2, maybe 3 of those in parallel to create a big bank, will shorten lifespan and wear unevenly.

....

....

A bit of an overstatement and over generalization.

It all depends upon how the banks are deployed.

All types of systems, including UPS, off-grid solar, large DC systems use multiple Banks of batteries and parallel of all types and sizes. Inbalance develops if the batteries are (1) of different age (2) wired incorrectly, (3) kept at different temperatures...

Larger cells, like 2 volt cells, can indeed be better, but not always. In an RV situation, if properly cared for, the garden variety group 31 or 6 volt batteries, it's going to be very hard to beat the value prop, form factor, and ease of replacement.

Group 31 and or 6 volt golf cart batteries are far cheaper than 2 volt cells... Usually on the order of 30 to 50% cheaper per amp hour to use a mass-produced mass consumed form factor.

Sent from my Pixel 4a using Tapatalk

 

[Chuck1]

3 ways you can wire 4 battery's, you have a complex system and it will be a puzzle

Q,Take the spare 12v groups and add one to my trailerable sailboat and the other to my truck's 'coach' battery bank.

A, you cant mix battery's of different ages or brands even sometimes, plus other details.

You need to study or find someone who can look at it in person.




4 battery wiring

 

[DaveInDenver]

All types of systems, including UPS, off-grid solar, large DC systems use multiple Banks of batteries and parallel of all types and sizes. Inbalance develops if the batteries are (1) of different age (2) wired incorrectly, (3) kept at different temperatures...

Indeed true. If you've been in the battery room for grid storage, data center, radio transmitter or telecom office then you know it's possible to build elaborate battery banks. But the bank is matched to the load and charging capability, which is controlled to the individual battery, even down to the cell in some cases, within the bank.

The effort and cost has to be worth the benefit, which might not be the case for you @Photobug. Keep it simple and trust the typical and tried best practices.

 

[Peter_n_Margaret]

Adding more batteries is like opening a new bank account without increasing your income.
There is always a way to add more solar.

Cheers,
Peter
OKA196 motorhome

 

[IdaSHO]

Adding more batteries is like opening a new bank account without increasing your income.

That's a great way to put it.

 

[john61ct]

The trick with off grid solar-only living

is ensuring you can track your energy usage (Ah @12V per day)

and keep below your average energy input per day

Then you can have a small bank, or a huge one.

All having a huge one buys you, is a bigger buffer for cloudy days.

Which can prove handy so long as we're just taking temporary variation.

But, in the end your income has to average out to be 110% of your outgo.

Of course day-long drives, or staying at a powered site twice a week, or a genset

or especially a combination of these

gives more flexibility.