MultiPlus 800VA – Two DC outputs for charging two batteries

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Oscar asked Sep 13, '21

MultiPlus 800VA – Two DC outputs for charging two batteries

Hello everybody.

Guys I am testing a Multiplus 800 ( NOT a Multiplus II ) ,and I have a question regarding the possibility to charge the ENGINE battery ( i.e second battery ) using a dedicated output on the Multiplus 800. On the Multiplus 800 Manual is written :

Two DC outputs for charging two batteries

The main DC terminal can supply the full output current.

The second output, intended for charging a starter battery, is limited to 1 A and has a slightly lower output voltage.

I noticed that even if the Multiplus is diconnectted from the line power ( i.e 220 Vac ) and is not working as a charger , on the second output ( used to charged the ENGINE BATTERY ) around 13 Vdc are always present. I suppose this voltage / current is provided by the Lithium battery ( in this scenario ).

Question :

Is this behavior correct ? In other words when the Multiplus is not charging any battery is it correct that the Lithium battery is it charging permanently the ENGINE battery ? Can this ( small but ) continuous drain cause a problem to the Lithium battery on long term ? OR is it working "as expected " ? I have a 100 A Lithium battery with EXTERNAL BMS.

Thanks in advance for your help.

Oscar

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Answer 1 · 2021-09-13T14:21:27Z

wkirby answered · Sep 13, 2021 at 02:21 PM

Yes, this output is available even when mains is not present, the idea being to maintain the start battery at all times.
It is a lower Voltage just enough for maintenance of the starting battery. The output current, once the start battery Voltage is up, will be a few mA trickle charge so not much drain on the house battery.

Remember that the output for 24V MultiPlus is for 24V start battery, do not connect a 12V start battery to a 24V MultiPlus.

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Oscar commented · Sep 13, 2021 at 05:04 PM

Thanks a lot this is exactly what I am looking for. Anyway I have a 12 Vdc Multiplus 800 VA NOT a 24 Vdc and the output - with a voltmeter - it's around 13 Vdc without any engine battery connected .These are great news ! Have a nice day ahead !

Oscar

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