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Old 04-21-2019, 06:48 AM   #1
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ABYC standards for batteries in series

Moving Paul's question from another thread...

Originally Posted by PaulGel View Post
...I had two 6v batteries in each main engine start bank and I was told by a very experienced ABYC marine electrician to replace them with one 12VDC 8D and not to use 2 x 6VDc. One set had failed anyway so no great loss. Has anyone heard this from other sources? It was news to me.
There is no ABYC rule (in E-10 or E-11) against the 2 x 6VDc setup you had.

E- (2016) does requires a "charge equalizer" in the case where two batteries are connected in series, but only where the batteries are used for multiple voltages. For example, if two 12v batteries are connected in series and this bank supports both 12v and 24v devices, then ABYC requires the charge equalizer. This would not be the case for you.

Your electrician may have had other reasons for wanting you to switch to 8D's. Did he specifically cite ABYC?

Personally, when the 4x 8Ds I have are ready for replacing, I will probably go with 2 x 6VDc batteries in series, mainly because they are smaller and easier to remove-and-replace. Either that or I'll be using 6x 2V carbon-foam batteries.

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Old 04-23-2019, 09:31 PM   #2
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He didnít quote ABYC as the reason I just mentioned it to validate his opinion. I think the reason was the potential for resistance across the bridging cable when a high start current was present versus the relatively low internal resistance of one unitary battery but I was too busy paying to be able to concentrate.

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Old 04-24-2019, 05:06 AM   #3
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A 1' long jumper results in .03 volts drop with 400 amps cranking. The connectors add a little more drop. I wouldn't worry about that much voltage drop.

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Old 04-24-2019, 10:21 AM   #4
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It could have been related to the battery type, starting vs deep cycle, that he recommended the change. For my EH700 Hinos, I have two 31 series starting type batteries in parallel. I also have two pairs of 6v golf cart batteries connected first with two in series, for a 12v combination, then the combination connected in parallel, for house batteries. I have a similar setup of golf cart batteries for the inverter circuit that is set up as a separate AC circuit. The AC circuit is for the outlets, microwave and refrigerator, the house batteries support everything else 12v.
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