2 of 5 MPPT shows significante higher voltage

DIY
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1

Hi
We have 5 MPPT chargers connected in the same point to our house bank of Lithium 12 V 750 Ah.

Two of the chargers indicates 14,2-14,3 Volt and they charge in abs and float. At the same time the other 3 chargers indicates a voltage of 13,7 Volt and charge in bulk mode. The difference is about 0,5 V higher for the two MPPTs.

The BMV indicates the same voltage as the 3 other MPPTs.

I have tried to make a reset to default but that didn’t help.

What can be the problem?

Thanks

Erik

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2

Probably voltage drop along the wires from the MPPT to the battery. Look for a poor crimp or bad connection.

All 4 of my 75/15’s are within 10mV.

3

Yes, check the cabling, crimps, fuses, on both positive and negative poles

4

Get a multimeter and when charging measure the voltage on each MPPT’s battery terminals. Then you will know if the voltages are different or if it is a measurement error. Simple basic electrical troubleshooting rather than thinking it is a settings issue.

5

Thanks for your reply.

I made some measurements on the bat. side on the MPPT and for three of those it was between 13,57 V and 13,74 V, the two others was 14,06 V and 14,07 V. On the batteri connection it 13,72 V. At the same time BMV indicates 13,26 V, and the batteries between 13,20 V and 13,22 V. See enclosed photo.

MPPT with Voltage.pdf (1.7 MB)

Those two with higher voltage has been liked this for a week. FYI, we are on the hard in Panama.

6

Time to check all your MPPT to battery cables on those 2 units. Good to confirm the MPPT readings are OK.

7

I made new connections on all cables from MPPT to the battery connection point and i seems to give the correct measurements now.

Thanks for your advice!

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