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Old 04-10-2015, 11:54 AM   #61
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Aren't your existing batteries agm? Are you going to buy a flooded group 31 or an agm? The xantrex will charge all the batteries connected to it at the setting you select. if you are going to mix flooded batteries and agms, you should use the agm setting. The flooded battery setting uses a higher voltage than is recommended for agm batteries.

The manual for your engine should give you the minimum battery requirement for starting. The highest CCA capacity in a group 31 that I have found is the Diehard Platinum marine at 1150 CCA. A flooded group 31 will probably be around 900 CCA. For starting batteries, CCA is more important than amp hour capacity.
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Old 04-10-2015, 12:00 PM   #62
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Originally Posted by ranger42c View Post
From reading, 6v golf cart batteries are said to be true deep cycle batteries, whereas 8Ds are almost always said to be really dual-purpose -- even if the label says "deep cycle." Different design in the GCs, thicker plates, better for deep cycling.

Pairs of 6v GCs at 12v usually give you about 220 Ah/pair. If four will fit where one of your current 8Ds fits, it'd be ~440 Ah vs. ~245 Ah. Or if six will fit where a pair of your current 8Ds fit, that be ~660 Ah vs. ~490.

No spills is an AGM (and gel) feature, as is reduced (not eliminated) off-gassing. Low self-discharge rate is also a feature that I've confirmed with our AGMs over winter. No maintenance is a good thing. OTOH, a flooded lead acid (FLA) system with a battery hydration system installed may be way less expensive.
I have a much smaller and simpler boat (and budget!). Decided to go with a 4 battery GC bank (440 Amp hours) with a Victronix monitor. Batteries were only $105 each and filled the space I had to work with to the brim. I have (2) 31's for a start bank. Probably overkill all around, but the price was reasonable. Our first overnight with the new house bank only saw the capacity reduced 10%...Fridge, stereo and lights...Simple..
I added a flow-rite watering system as access is problematic. I can top off the water with a few squeezes of the Bulb and a bit of distilled water. All 4 are interconnected with the Flow-rite system. Maintenance minimized!

Crown GC batteries.
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Old 04-10-2015, 12:07 PM   #63
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According to this, you should be fine with a Group 31 battery
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Old 04-10-2015, 01:46 PM   #64
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Getting Frustrated!

I ordered a Group 31 AGM, thinking I could use it in one start/house bank and the remaining good 8D AGM in the other. (I could later use the Group 31 to be my genset start battery once I figure my entire system out.). Then I called Dekka manufacturer East Penn and they say don't try to charge batteries from different groups with a single charger--even if they're both AGMs. (Total disclosure: the person I spoke with was very nice, but I'm not sure I was dealing with the technical A-team.)

I have a Xantrex Truecharge2 on the boat that has an AGM mode, but East Penn has me spooked.

Does anyone use a single charger to charge batteries of different groups? If so have you had any problems?
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Old 04-10-2015, 01:50 PM   #65
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If that G31 start-only batt will only be sitting for a week between uses, I wouldn't worry about the need for charging. It'll get enough from the alternator.
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Old 04-10-2015, 02:04 PM   #66
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I charge one bank of group 31s and one bank of 2 4Ds with the same charger. I'm not sure what the person at Deka was trying to tell you. Your charger supports three separate banks and will send current as required to each bank. Maybe she was referring to charging different battery sizes within one bank.
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Old 04-10-2015, 02:08 PM   #67
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False Alarm

Thanks Al, Blue Yonder and all who have helped me navigate unfamiliar waters.

The Xantrex rep gave me a totally different story. (In fact, I may have misled East Penn because the tech probably wasn't clear that this is a multi-bank charger.).

Xantrex says the multi bank charger will sense which battery needs additional charging and push amps to it; it will not charge all batteries on the system at the same rate or amount. As long as they're close to the same battery type (AGM, LA, etc.) the Truecharge2 will give the 8D and Group 31 AGM what they need and no more.

Hope this is true, cause I'm going for it.
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Old 04-10-2015, 02:26 PM   #68
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Sounds like you are set to at least get the boat launched. Don't forget to check the actual charging voltages at the batteries. You should also get the temp sensing cable from Xantrex if you don't have one installed.

Good luck
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Old 04-10-2015, 04:57 PM   #69
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Quote:
Originally Posted by angus99 View Post
Xantrex says the multi bank charger will sense which battery needs additional charging and push amps to it; it will not charge all batteries on the system at the same rate or amount. As long as they're close to the same battery type (AGM, LA, etc.) the Truecharge2 will give the 8D and Group 31 AGM what they need and no more.

That tracks with what Odyssey told me when I started switching, 10 years ago. I was replacing a single bank made up of two G29s and a G27. (PO maybe had added a single G27 battery to both existing banks of two G29s?)

In the near term, I was going to end up with one FLA bank of two G29s and a G27, one single FLA G27 for the genset, and a new bank of three AGM G31s. Not to worry, says he, same thing Xantrex told you. Then I checked with ProMariner (our charger), same story.

A few years later, I swapped out the second large bank for three more AGM G31s, and the genset battery changed to a single AGM G34.

All good.

-Chris
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Old 04-10-2015, 09:49 PM   #70
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Really hope I can buy you guys a beer or two one of these days.
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