faulkton avatar image
faulkton asked

Battery locations and overall system input? Any obvious mistakes?

I live full time in a 30’ class A RV and rarely have shore power. This is what i have so fart and the upgrade path i am looking at. any sort of input/advice from people who know more than me is really appreciated.

I have a total of six Costco golfcart batteries, 210 A/h each, running at 12V for a total of 630 A/h. Two batteries are under the hood and the other four are in the rear with 2000w inverter. There is a SCC connected close to each bank of batteries , so two SCC total. All batteries bought at the same time and are isolated from the starter battery but not each other. So was this a terrible idea? Should i move the two fron batteries to the rear or is this ok?

The 12v fuse panel for the RV was already in the rear next to the AC/DC charger, powered by the grid or the onboard generator and connected to the house batteries under the hood with 4 gauge wire running the length of the RV. Since this came from the factory, i figured it was ok. I didnt think it was a good idea to run the SCC through 30’ of wire If i didnt have to. There wasn’t enough room under the hood for all the batteries And I’d dont know how many amps the alternator puts out & that’s why i decided to put two in front and 4 in rear.

The front batteries have a 100/20 SCC and the rear have a 100/30. That maxes out at 50amps total for 630 a/h of batteries. I have six 100W panels total, mimicking the battery placement, two on the front SCC a four on the rear.

I plan on adding more panels as i go and will probably swap out and add more battery at some point, but i wanted to learn on cheap batteries that I could exchage easily if I kill them in under a year.

What i am thinking , unless i get told this was a stupid setup and have to change it, I want to add 6 more panels. Basically doubling the panels on each SCC in parallel. When i do that i will also swap the 100/30 for the 100/50 but leave the 100/20 up front. I realize that in full sun both SCC will be maxed out in current And will be wasting some.

My thinking is that the 100/30 puts out around 25amps with 400w in panels now, so I wouldn’t actually be wasting much but would improve my cloudy day performance. My understanding is that over paneling the current like this is ok as long as it never goes over the voltage hard limit of the SCC, which would be fine doubling the number if panels i have right now.

The panels are mounted on pallets, but not actually mounted on the roof so that i can prop them up facing the sun, which makes a big difference. When i add panels i plan on permanently mounting them to the roof. My thinking is that it is a good idea to have some i can set out direct sun, without having to be parked in the direct sun.

So, if you managed to read all this, thanks. Now what do you think of my setup and what, if anything should i change? Think my plan to over-panel is safe and ok?

MPPT Controllersbattery
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Paul B avatar image Paul B commented ·

Suggest that you do a wiring diagram of exactly how you have it connected or propose to connect it, showing relative positions and ALL CONNECTIONS and wire sizes. this will also help us help you

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2 Answers
Kevin Windrem avatar image
Kevin Windrem answered ·

60' (round trip) of #4 wire is likely to cause significant voltage drop when running the inverter: 2.5 volts for 2000 watts (166 ams @ 12 volts). 4/0 wire reduces this to about 0.3 volts which is still significant when paralleling batteries and attempting to significant current out of the bank.

In your current configuration, you may find that the 6 batteries function more like 4 since the front 2 have so much wire resistance compared to the back 4.

Locating all batteries as close together as possible is generally the best approach. If that's not possible, throw as much copper as you can at the connection between the two battery banks. TWO 4/0 cables each for positive and negative would be a start.

I don't think there is much benefit to using separate solar charges for each bank since they are in parallel anyway. Think about one large solar controller and wiring the panels in a series/parallel arrangement.

If you do have separate roof and ground solar arrays, DO use separate controllers for them.

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randy-putnam avatar image
randy-putnam answered ·

Another thought about the PV. Instead of adding more 100W panels perhaps look at higher wattage panels. I’m using 2 170W monocrystalline panel in parallel on the hardtop roof of my 26’ Trojan boat, thru a Victron Smart 100/30 which works fine, and will charge 2 Battle Born LFP 100AH batteries, in parallel, which are replacing my 2 old (and very heavy) 114AH lead acid batteries.

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