question

richie-gorrod avatar image
richie-gorrod asked

Adding batteries to Mutliplus system

I have a Multi 5000/24 with ESS assistant.

4 x 250/80 Mppt connected to a bank of 2s 6p 12v 135aH batteries.

I also have a PV system on the roof that feeds into the multi to charge the batteries when we have excess solar. (I inherited this when I bought the house with a good feed in tariff)

The DC coupled battery are set not to feed in.

I would like to add another 12 batteries to this system.

I dont have BMV or smart shunt.

I understand that I need to reconfigure the multi with the new battery bank capacity but how does the multi know the % of SOC?

Would I be best to buy BMV.?

Many thanks


Rich

SOCmultipus
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2 Answers
Mike Dorsett avatar image
Mike Dorsett answered ·

Assuming that you are using lead acid batteries, then the Soc is approximated from the energy into and out of the battery. The inverter will measure the current into and out of the battery to determine Soc, and set this to a given value at end of absorption charge.

Adding more battery is relatively simple if they are the same type, and you only need to change the total Ah in the inverter.

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richie-gorrod avatar image
richie-gorrod answered ·

Many Thanks Mike. They are AGM's.

Is it just the charge from the Multiplus or is ok to allow the Mppt charge the batteries too. They are all connected to a Colour control so when charging they I see the total current going into the batteries from both the mppt and Muti. At the moment they dont get to float as I have charging disabled on the multi. I do get some charge from the panels on the roof (AC coupled system) when they have excess energy.

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