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daprod avatar image
daprod asked

MPPT 150/85 stops bulking over 26A and goes to float

I have an MPPT 150/85 connected to 3 Lithium batteries LiFePo4 in 12V with over 1100W of solar panels. I changed the cables from the MPPT to the batteries for bigger ones and added a 85A fuse. Since then, the MPPT bulks until 25A and when it reaches that current, it goes back to either float or absorption, it doesn't matter if the batteries are 50% or 80% charged. It is then impossible for me to fully charge the batteries as I'm living out of those.

What could be the cause of this?

Thanks,

Yann

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mppt state
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1 Answer
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mvas answered ·

What is the measured voltage at the terminals of all three batteries.
What is the measured voltage at the battery terminals on the Solar Charge Controller?
When high amps are flowing.
Is there a voltage drop across the cables and/or fuse when high amps are flowing?
Did you proper crimp and torque all connections - recheck.

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daprod avatar image daprod commented ·

I measured during the day and the voltage at the batteries terminal were all 13.17V.

The voltage at the battery terminals on the solar charge controller was 13.4V all accros the cable, fuse and connector.I tried to crimp it properly but this cable is quite big, so it's difficult to know for sure everything is 100% crimped right.
Thanks for the reply.

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mvas avatar image mvas daprod commented ·
If you put the all of the old cables back, does it work again? If yes, then swap one component at a time until you find the problem. Use the process of elimination!
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daprod avatar image daprod mvas commented ·
Yes it works with the old cable, the issue is either the new cable connectors or the fuse.
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