MPPT 75/10, why has the battery voltage suddenly dropped?

DIY
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1

Hi all, I recently set up a system powering a rain gauge with an MPPT 75/10, 20W solar panel and 30 Ah LiFEPO4 battery. The set up isn’t local but it is telemetered and reports battery voltage every hour along with rainfall. The controller is set to the lithium battery preset.

It was working fine until last night when the voltage suddenly dropped. The voltage increased again but it doesn’t seem to be charging. The weather forecast for the area was sunny and previously it would charge at least a little even on overcast days and the overnight minimum voltage would stay fairly constant.

Any ideas what is going on before I go out to fix it? I’ve attached a voltage chart because it probably explains it better.

Shorncote
Shorncote1001×505 53.3 KB

2

Check the fuse?

3

Sorry, those sharp jumps between 13 and 14v should be a loose connection, with sun the voltage jumps up, without its the battery voltage again.

1 Like
4

I was thinking that is a possibility as well. Either way connections from mptt to battery have to be physically checked.

5

Thanks, that’s annoying if it’s something that simple but should be an easy fix. Bad connection makes sense as when we use that type of battery without solar it lasts a long time (rain gauge is very low power) and the voltage doesn’t suddenly drop like that.

6

Anything else it could be, maybe an incorrect setting? I’ve noticed something similar at a different site. The voltage has been dropping at about 08:00 every morning which seems unlikely for a bad contact.

Cassington
Cassington984×504 50.5 KB

I have only used these controllers at three sites so far. The third is as I’d expect:-

grendon
grendon848×497 69.5 KB

7

For me it would be my wife making coffee :wink:

8

Haha, unfortunately this is just in a hut powering some low power equipment monitoring river levels so there shouldn’t be anyone in there!