Combining AGM and Cranking batteries

Submitted: Wednesday, Jan 28, 2009 at 08:26

ThreadID: 65477 Views:4014 Replies:5 FollowUps:9

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madcow

Well my Delkor M27 Deep Cycle battery has just about died. I've only recently replaced the cranking battery with a Supercharge Gold in my GU 4.2tdi 03. I looking at possibly slotting in an AGM bettery to run the fridge/s. Battery management is via a Pirahana system. With an extended trip coming up I'd like to gether everyones thoughts on either an AGM or Traditional Deep Cycle Battery. Given that an AGM will charge more quickly I'm leaning that way.

Thoughts , Ideas?

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Reply By: Member - Norm C (QLD) - Wednesday, Jan 28, 2009 at 09:38

Wednesday, Jan 28, 2009 at 09:38

AGM is certainly the way to go in my opinion. No problem connecting to cranking battery via isolator.

Some say AGMs are no good in the engine bay due to heat. I had a 90 AH AGM in the engine bay of my Hilux for close to three years. I took it out last August and it is now in the engine bay of my 70 Series Toyota. As long as it is not right against the exhaust manifold or turbo, my experience says they are fine in engine bay.

I have a second AGM (120 AH) in the back of the ute, connected in parallel with the one in the engine bay with 50 Amp circuit breakers at each battery. All works fine.

Norm C

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Follow Up By: Member -Signman - Wednesday, Jan 28, 2009 at 11:27

Wednesday, Jan 28, 2009 at 11:27

Are both your aux. batterys of the same capacity??

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Follow Up By: Member - Norm C (QLD) - Wednesday, Jan 28, 2009 at 12:05

Wednesday, Jan 28, 2009 at 12:05

90 AH in engine bay, 120 AH in back, Signman

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Follow Up By: Member -Signman - Wednesday, Jan 28, 2009 at 12:34

Wednesday, Jan 28, 2009 at 12:34

Hi Norm
I thought there was some issue having dissimilar capacity batterys hooked up for a parallel charge??
Please correct me if I'm wrong !!!

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Follow Up By: Member - Norm C (QLD) - Thursday, Jan 29, 2009 at 14:25

Thursday, Jan 29, 2009 at 14:25

That's a view expressed by some, but I don't think many subscribe to it any more.

Certainly, I have had no problem with it. Both batteries get close to a full charge on a long drive. My measure of this is that on returning from a camping trip, I put the batteries (separately) on a CTek smart charger. On most occasions they go straight to 'float' within a couple of minutes.

The current batteries have been used this way for close to 3 years, with no sign of trouble.

That's my experience. If in doubt, put a post on a separate thread. You will get lots of different views, but I think you know the people you can trust on 12 Volt issues so you can sort the wheat from the chaff.

Norm C

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Follow Up By: Member - Mike DID - Thursday, Jan 29, 2009 at 16:46

Thursday, Jan 29, 2009 at 16:46

It's not a good idea to connect two different types of batteries in parallel - but if you're using an Isolator, then the batteries are not in parallel.

e.g. while the Starting battery remains fully charged, you're discharging the Auxiliary !!!

So if each battery (Starting, Auxiliary) is capable of being charged correctly by the Alternator, then they will charge as well when both are connected to the Alternator.