Starting Battery CCA

[shrew]

This is kind of a dumb question, however...

I currently have 2 Group 31 AGM Dep Cycle batteries (1 for starter, and 1 for house). I'm looking to expand my house amp hour capacity. The 2 Group 31 AGM's are identical Make, Model, type, capacity. It seems to make the most sense to move the starting battery over to the house and buy a new starting battery.

The specs for the starter are:

Min. Amps: 60
Max. Amps: 95

so in looking at Cold Cranking Amps (CCA) I'm looking at batteries around 800 CCA to 1020 CCA. If the start has a limited range of 60~95 amps, how does that translate for CCA on the battery. In other words will ANY starting battery suffice? Looking for a little advise.

[Phillbo]

I go by the rule of 850 CCA Minimum.

[ss3964spd]

Shrew,

You really don't need much of a battery to get that engine started. CCA's can be important if you're trying to start an engine when it is really, really cold - low 30's and below, and/or if the engine is habitually difficult to start (takes lots of cranking). It's really no different than starting an automobile engine. The AGM battery that I use to start the big block in my old convertible is about 700 CCA. The engine does take a bit of cranking if it hasn't been started for a couple of days, and the car has sat for weeks without being started. The battery has never had a problem. I use a lead acid GP 24 as the starting battery for the 350 MAG in my boat - 800 CCA I think, and it, too, has sat for over a month. Cranks right up.

Dan

[shrew]

I got a Group 24 that claims 1000CCA, though I strongly suspect that is at 68F, not zero. I moved the existing starting battery over to the house. I now have 2 Group 31 AGM Deep Cycles and a Group 24 Starting. I left the starting battery to run off the alternator and the battery charger is now onlly pushing the house batteries. The boat starts stronger and better and now I have more than enough house battery.

I spent 6 days and 5 nights out. I ran my little honda 2000 genny for approx. 2hrs per day. I NEVER had a problem with house power. I know I'm running at a deficit, but I also now know that I can get a week without much worries. Thanks for the feedback. This worked out better than I expected.

[pascavone]

if you read your boat battery charger manual, it says you need to change the jumper switch setting for gel, optima batteries, away from acid batteries.

the gel's don't take trickle charges, so the battery charger has to push 14 amps of nothing.....

[shrew]

Correct, i have a Xantrex 3 bank 40 amp battery charger. It is currently set to AGM which is what the 2 Group 31 house batteries are. This is why I didn't bother connecting the starting battery flooded lead-acid to the charger. The Honda 2k only puts out about 13.3 amps. As a result, the when the genny is running the charger, you never see the charger read above 10amps. (Display shows 5 amp, 10 amp, 20 amp, etc.). When I run the genny, I also run the fridge off of the genny as well.

What this is doing is taking the total number of amp hours drawn by the fridge, minus the amp hours while the genny is running the fridge, minus the amp hours being replaced in the house bank by the genny. This is reducing the amp hour burn rate, however I am still burning more amps than I'm generating. This is ok, as I don't need to be out there for weeks. It has proven that I can be out there for 6 days.

[ss3964spd]

Sounds like a well working set up Shrew.

You're right about the 1000 CCA. Automotive battery cranking amps are listed as CCA's - Cold Cranking Amps - which are measured at 0*F for 30 seconds. Boat battery cranking amps are listed as MCA - Marine Cranking Amps - which are measured at 32*F for 30 seconds.

Or something like that.

Dan

[biggerseagar]

Shrew I am going to try to apply my 5 months of experience in the Battery business with your question.

First...... 800 CCA is more than enough to start your engines and take care of your 12v. Big diesel trucks need the big CCA to start up not a gas engine. You are only as good as your worst battery.

If my formula is correct......... to figure out AH (amp hour)take your reserve capacity of your battery and times it by .6. So if on your battery you have a RC rating of 230 x .6 is 138 AH. Wire your batteries in parallel... keep the 12V but your AH and RC triples to 414 AH or RC 690.

Hope this helps.....

Roger

I would just buy another 31 series and with the genny as backup you should not have to worry about power.

[shrew]

Awesome Roger, thanks. Now I gotta break out my slide ruler.

Here are the specs on the house batt.:

[TABLE="width: 100%"]
[TR]
[TD="bgcolor: #66ccff"]Lifeline Battery
Part Number[/TD]
[TD="bgcolor: #66ccff, colspan: 3"]Cold Cranking Amps[/TD]
[TD="bgcolor: #66ccff"]Rated Cap.
Amp. Hrs
20 Hr Rate[/TD]
[TD="bgcolor: #66ccff, colspan: 3"]Minutes of Discharge[/TD]
[/TR]
[TR]
[TD="bgcolor: #66ccff"]68°[/TD]
[TD="bgcolor: #66ccff"]32°[/TD]
[TD="bgcolor: #66ccff"]0°[/TD]
[TD="bgcolor: #66ccff"]25 Amps[/TD]
[TD="bgcolor: #66ccff"]15 Amps[/TD]
[TD="bgcolor: #66ccff"]8 Amps[/TD]
[/TR]
[/TABLE]
[TABLE="width: 100%"]
[TR]
[TD="bgcolor: #d0efff, align: center"]GPL-31T [/TD]
[TD="bgcolor: #d0efff, align: center"]880 [/TD]
[TD="bgcolor: #d0efff, align: center"]750 [/TD]
[TD="bgcolor: #d0efff, align: center"]600 [/TD]
[TD="bgcolor: #d0efff, align: center"]105[/TD]
[TD="bgcolor: #d0efff, align: center"]195[/TD]
[TD="bgcolor: #d0efff, align: center"]340[/TD]
[TD="bgcolor: #d0efff, align: center"]688[/TD]
[/TR]
[/TABLE]