Multiplus Starter Battery Port Operation?

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Jim asked Jun 14, '23

Multiplus Starter Battery Port Operation?

The Multiplus manual doesn't have much in the way of details about the starter battery port. I understand it charges at 4 amps and lower voltage. But when does it operate? Is it on all the time or only when AC input is active?

I have the Multiplus 12/3000/120 with a Cerbo GX and a couple of MPPT 100/50.

starter battery

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Answer 1 · 2023-06-14T19:08:48Z

Alexandra answered · Jun 14, 2023 at 07:08 PM

@Jim

It follows the charge cycle of the main house battery. So if bulk then in bulk. If floating then that one will float as well.

As far as i know it does not deplete the main bank for charging the auxiliary battery.

https://community.victronenergy.com/questions/79393/can-i-use-auxiliary-battery-charger-output-4-amp-o.html

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Jim commented · Jun 14, 2023 at 07:17 PM

Thanks for that confirmation. The starter battery is for the on-board generator. I need the starter battery to get a charge while the generator is running since the generator doesn't provide a charge to the starter battery.

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Alexandra ♦ Jim commented · Jun 15, 2023 at 06:25 AM

@Jim

If there are doubts, you could pass it through a different relay and have that relay disconnect on SOC. (So daisy chain it.)

Or simpler would be a switch/disconnect.

Then there will be maintenance of the starter battery but not cycling the house battery.

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derrick thomas commented · Jun 15, 2023 at 12:39 AM

The 4amp auxiliary output is always powered regardless of what state the multi is in. The aux output will maintain a slightly lower output voltage than the main battery bank. In theory, if off-grid with no active charging source, the aux output could actually drain the main battery bank if there was a fault in the aux battery such as a shorted cell, which would cause the aux battery to pull the voltage down.

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