question

bjorn avatar image
bjorn asked

Multiple MPPT chargers on same profile but not progressing at same rate

I have a 100/30 and a 150/35 MPPT controller each with a similar set of panels charging a common battery bank. They are both set on charging profile 1. They are connected to a common positive shunt and a common negative shunt that then proceed to respectively the battery positive and the negative battery monitor shunt. The 30A charger reaches absorption and float but the 35A stays in bulk. How can the chargers tell the difference between the actual battery voltage and the voltage of the other MPPT charger? My bmv700 battery monitor says the batteries are at 100% but I'm unsure about its settings. I have 8 Trojan sagm 6V 375Ah batteries in 2x 24V strings. Not sure at what voltage I should set the charged voltage and the tail current. I have 750Ah at 24V. Any help would be greatly appreciated!

MPPT Controllers
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1 Answer
klim8skeptic avatar image
klim8skeptic answered ·

Hi Bjorn,

EDIT, !check that both mppt are set to the same battery voltage!

What you are seeing is due the small voltage differences on the mppt battery terminals.

This is due the voltage loss between the mppt and the battery. Different cable type/length/thickness/current will give voltage variation. Every fuse/isolator/joint will also have a voltage loss. Even cable temp will have an effect.

After you have updated the mppt's firmware and are happy with your install, the only other option would be to a Smart battery sense, and if your mppt are bluesolar add 2 Bluetooth smart dongle.

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