Need help selecting battery for 2012-Forester 2251sle

[chamnic]

Hello all,

My battery seems finished, does not keep charge for long. My battery as a sticker that says NC-27 on it. Does that means it's a group 27 type battery (seems logical to me but we never know) ?

Looking at group 27 batteries, I see some which are dual-purpose, ie starting and deep cycle and some which seems to be only deep-cycles ?

Is the starting purpose of those dual battery so that we can start the generator off that battery ?

There are also no spec on battery (like Cold Cranking Amp) … does it matter ?

Some are Maintenance free (AGM) and some not, are AGM worth the extra price difference ?

thanks in advance

[Chuck_S]

A single battery is usual for a self-propelled camper and there is certainly a starting battery for the vehicle's engine. This ain't it. Group 27 is the size of a deep cycle "house" battery. Since this is not a starting battery the absence of "cold cranking amps" is expected and in fact the presence of cold cranking amps is a sign the battery is not deep cycle. You want a deep cycle battery for the house battery.

Starting batteries are designed to start large engines like the truck chassis of your camper. Not sure how your generator is wired but it should start fine on the house battery. I start my Honda 50 outboard with a deep cycle AGM battery without damaging the battery. I doubt your genset is this big.

AGM batteries take little maintenance but are expensive. I run them on boats as they can be stowed is out of the way places. Camper batteries are usually accessible and flooded batteries are fine. Group 27 is bigger than Group 24 but has little capacity compared to setups using a pair of batteries such as two Group 27s in parallel or a pair of high amp hour 6v "golf cart" batteries in series.

Since you need a new battery I'd consider going to two batteries if there's room or a higher capacity single battery.

-- Chuck

[chamnic]

Thanks Chuck.

I checked the specs on generator (Cummins Onan RV QG 4000) and it says it need a minimum battery rating of 450 CCA so I guess that means I need a dual purpose then ..right ?

I understand the advantages of dual 6 volts batteries but we're never away from shore power for long period of time so do not need the extra capacity.

[Chuck_S]

Dual purpose batteries are horrible compromises. My Honda 50 outboard wants 420 CCA and I've started it exclusively for several years with a Group 24 (27?)-sized AGM deep cycle battery.

Can you start the generator with the truck starting battery? Would make sense at that's gotta have a lot of CCA available.

-- Chuck

[chamnic]

The generator is all wired-in the RV so as test, I unplugged the current battery and tried starting the generator see if it would take its power from the truck battery but it did not so it's wired to the house battery (maybe what I tried did not make sense from an electrical standpoint).

I think from your experience, I could go with a deep-cycle only battery. For what's it's worth, we rarely use the generator anyway (mostly for micro-wave when stopping for lunch or dinner).

Thanks Chuck for the help

[rsdata]

Interstate batteries. dual purpose ( start-deep cycle), group 27 at Costco are less than $80 IF you bring in your old core to trade-in...

best deal going I have found, and Interstate is a GOOD battery...

[Larry-NC]

Originally Posted by chamnic

Hello all,

My battery seems finished, does not keep charge for long. My battery as a sticker that says NC-27 on it. Does that means it's a group 27 type battery (seems logical to me but we never know) ?

Looking at group 27 batteries, I see some which are dual-purpose, ie starting and deep cycle and some which seems to be only deep-cycles ?

Is the starting purpose of those dual battery so that we can start the generator off that battery ?

There are also no spec on battery (like Cold Cranking Amp) … does it matter ?

Some are Maintenance free (AGM) and some not, are AGM worth the extra price difference ?

thanks in advance

What's the date on the battery? Is it the original 2012? Or a replacement? Look at the date tag on it. If it's original, it could be due for replacement. If it's newer, you would want to look for something that's drawing it down--a light left on in a compartment, radio on with volume down, refrigerator light not going off, etc.

• Turn everything off
• Remove one cable from the battery.
• Set your multimeter to the 10 Amp scale and plug one test lead into the Common jack and one into the 10 Amp jack.
• Touch one lead to the battery post and the other to the cable. You should read less than, say, 0.1 Amps.
• Change the meter to the 200 mA scale and move the test lead from the 10A jack to the V-ohm-A jack. Repeat the measurement.
• This should be less than 100 mA. The higher it is, the more "parasitic" drain there is on the battery. This could be due to something you just added: GPS,radio, backup cam, that draws power when it's "off."

Larry

[poppytoymaker]

Not rocket science. I have a 2015 2251sle and when I decieded it was time for a new battery I took the old one out and took it tod Advance Auto and they matched me up. why would you start your gen with truck battery unless house batteries were to wee and in that case I would start the gen. with truck running and that would charge the house batteris. Just curious.

[camaraderie]

No one has asked the key question: Do you boondock/dry camp without electricity?
If so...THEN you need at least a decent TRUE deep cycle battery that has a 20amphour rating from the mfr. ...Suggest a Trojan or a Deka dc series for good performance if you are going to stick with a single 12V. ALL Group 27 deep cycle batteries will give you roughly the same amp hours AND enough power to start your generator. The Deka deep cycle DC27 marine master for example has 575 cold cranking amps.
The major differences you will find between brands in the deep cycle category is cycle life...which is largely about the amount of lead used...so weight is a good clue when comparing since THAT spec remains secret except when the marketing department makes stuff up!
If you DO boondock...you might consider adding another 12V or a pair of 6V's instead of a single.
As for AGM's...they provide NO PERFORMANCE ADVANTAGE in capacity or cycle life over wet cells. What they DO provide is:
1/10th the self discharge rate which is good if you store your camper without electric for long periods.
Ability to take a faster charge...saving generator time & $$
Ability to work inside a coach or upside down and no adding water.

On the downside...they REALLY don't like heat or being left less than fully charged.

IMO they are a waste of money unless you need the storage advantage or are fulltiming it and can control the environment and take advantage of the charging capabilities.

Oh..and if you don't boon dock...you don't cycle so a deep cycle is a waste and you should head to Walmart and get a dual purpose single group 21.
Hope this helps.