RV Battery Bank Question

MrClean73 · June 2012

Hi,

I am in the process of designing a system for my 40' Itasca RV. I'll be using:
(3) Canadian Solar CS5P230 235W 47.2Vmp
Morningstar Tristar MPPT60 Controller
trimetric 2025RV Monitor
Dimensions Unlimited Win-12X20B3RT 2000W Charger/Inverter

I just bought 6 Trojan 105RE batteries.

My coach currently has 2 engine batteries and 3 house batteries. I came to find that my house batteries were shot, and when I found that the Trojans woudn't fit in the battery tray I impulsively replaced the house batteries without thinking a little longer term (ie. about the system I was about to start putting in)

the 3 house batteries that I just replaced are Interstate RSM-29 with specs:
12V Deep Cycle
CCA:675
MCA: 845
RC (Min) 25A: 210
Hrs at Ampere Load:
- 5: 21
- 15: 6.4
- 25: 3.4

Unfortunately, I can't return the new Interstate batteries, but I can get exchange or credit for them that can be used later...

Interstate does make a 6V Deep Cycle with the following specs, that I could potentially exchange for if it made sense:

Model: GC2-XHD
Amp hours @ 20hrs: 232
RC (Min.)
@25A: 474
@75A: 122
Hrs. at Ampere Load
- 5amps: 54.5
- 15amps: 14

So, my question is as follows: Can I use all these together (the 3 house batteries that live in the tray where they were AND the battery bank in the next compartment over in a sealed in vented box), or am I really best getting rid of the Interstate batteries (12v, deep cycle) and just sticking with the Trojan (6v).

Thoughts and feedback will be much appreciated!

Thanks in advance,
Andrew

inetdog · June 2012

Re: RV Battery Bank Question

MrClean73 wrote: »

Hi,

the 3 house batteries that I just replaced are Interstate RSM-29 with specs:
12V Deep Cycle
CCA:675
MCA: 845
RC (Min) 25A: 210
Hrs at Ampere Load:
- 5: 21
- 15: 6.4
- 25: 3.4

Any battery that quotes a CCA or MCA number, whether large or small, is not really a pure Deep Cycle battery. You will see listings, for example, for Marine Starting Batteries and Marine Deep Cycle Batteries that both quote a CCA number. But the Marine "Accessory" batteries may be different, and the Renewable Energy battery types tend to be pure Deep Cycle The usage of the term by manufacturers, especially in their marketing info, is all over the map.

From one Interstate dealer:

The best price on Interstate Batteries SRM-29, the number one Marine/RV replacement deep-cycle battery, it is the most powerful cranking battery available today.

inetdog · June 2012

Re: RV Battery Bank Question

Blackcherry04 wrote: »

The Interstate GC-2 - XHD seem to be a OK battery,

Three pounds more lead than the HD or the RD, a good sign!

Blackcherry04 · June 2012

Re: RV Battery Bank Question

inetdog wrote: »

Three pounds more lead than the HD or the RD, a good sign!

I deleted that post, I didn't realize he had already bought the Trojans till I re-read the post. I do think they are over-priced, as are some others. The Interstate GC-2 XHD is about a $120.00 street price and thats not cheap.

BillBlake · June 2012

Re: RV Battery Bank Question

Andrew,

How does the trickle charger that is built-in for when your plugged in enter into the mix?
Years ago I had a Pace Arrow Motorhome that had 2 huge 6 Volt batteries in series.
I didn't check the water levels for a stretch and that 2 Amp (they said) charger boiled them dry.
It was plugged in 99% of the time being used in an industrial yard.
The dealer couldn't get the monster 6 Volt batteries anymore and threw in a couple of 12's.
It was never the same again. They just didn't make it.

If you really want to keep both banks it would take some study. There are battery combiners on the
market that can work well. Watching what the RV guys are doing is good.
Watching what the Boat electricians are up to is even better.

https://www.google.com/#hl=en&gs_nf=1&tok=PjCFb359M6diKpn5oVhEPw&cp=17&gs_id=1u&xhr=t&q=battery+combiners&pf=p&sclient=psy-ab&oq=battery+combiners&aq=0&aqi=g1g-K1g-m1g-mK1&aql=&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&fp=be407671e0d7449&biw=1024&bih=533

I hear this guy knows a bit about the subject.

http://shop.pkys.com/automaticchargingrelays.aspx

Bill Blake

inetdog · June 2012

Re: RV Battery Bank Question

BillBlake wrote: »

If you really want to keep both banks it would take some study. There are battery combiners on the
market that can work well. Watching what the RV guys are doing is good.
Watching what the Boat electricians are up to is even better.

https://www.google.com/#hl=en&gs_nf=1&tok=PjCFb359M6diKpn5oVhEPw&cp=17&gs_id=1u&xhr=t&q=battery+combiners&pf=p&sclient=psy-ab&oq=battery+combiners&aq=0&aqi=g1g-K1g-m1g-mK1&aql=&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&fp=be407671e0d7449&biw=1024&bih=533

I hear this guy knows a bit about the subject.

http://shop.pkys.com/automaticchargingrelays.aspx

Bill Blake

I don't know how his product compares, but the information on this site is a gold mine for batteries and off-grid information. (This link is just to one small page on his site. Follow the navigation links on the left for lots more goodies.)

CATraveler · June 2012

Re: RV Battery Bank Question

I don't believe you said that 4 6's would fit in the battery box. If not then they are not an option. Aren't the 6 trojans enough power? I would not mix Trojans and Interstate of either 6V or 12V. You could have 2 separate banks but I'm thinking sell the Interstates. Possibly considering 4 GCs Interstate upgrade and then sell them.

Vic · June 2012

Re: RV Battery Bank Question

inetdog,

I do not want to get too nit-picky, but a number of real Deep Cycle batteries DO list; CCA, MCA and Reserve minutes:

From the Surrette 4KS25 Data Sheet:

COLD CRANK AMPS: (CCA) 0ºF / -17.8ºC 3714

MARINE CRANK AMPS: (MCA) 32ºF / 0ºC 4643
Even lists the 4290 minute Reserve Mins.

http://rollsbattery.com/public/specsheets/4KS25P.pdf

What you said may apply more to the Group 24, 27 sized batts.

Picking done, Vic

MrClean73 · June 2012

Re: RV Battery Bank Question

Bill,

That's a good question. I hadn't considered the trickle charger at all. I'm not sure that I need it if I have 600w+ of panels up top...

From what I'm reading, it sounds like I'm best just nixing the Interstates completely and keeping the 6 Trojan (in a separate compartment) as my house battery bank.

Unless someone wants to jump in to the contrary, I guess I'll be asking around to see who needs new batteries...

Thanks!
Andrew

inetdog · June 2012

Re: RV Battery Bank Question

MrClean73 wrote: »

Bill,

That's a good question. I hadn't considered the trickle charger at all. I'm not sure that I need it if I have 600w+ of panels up top...

Thanks!
Andrew

There is an important difference between a trickle charger (fixed small current) and a float charger (whatever it takes to maintain the float voltage by countering the battery self-discharge. )
If you will be plugged in for long periods of time, a trickle charger with either too high or too low an output current will be harmful to your batteries. I would stick with what your solar and charge controller put out, unless you are parked in the shade. Even then, connecting an alternate AC to DC source to the charge controller will be better than using a trickle charger.

RV Battery Bank Question

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