question

eyacht avatar image
eyacht asked

MPPT not charging but Victron Connect says it is

Hi everyone - I have an odd situation that I hope someone can shed some light on. I have an MPPT 75/10 that has my 48V propulsion bank connected as PV in and the battery out goes to my starter battery. There is no load connected. In the Victron Connect app, everything looks great - battery voltage is 13.4V and it's in float. I just went to turn on the generator and got no power at the panel. Having checked the breakers I took a voltmeter to the starter battery and it's completely dead - 3.5V. I have no idea how the app can read healthy voltage and the battery is pretty much dead. Any thoughts? Thank you in advance.

EDIT 10 Aug 23 - I followed advice and measured voltage from MPPT + to battery - and from MPPT - to battery +. The first was 2.4V and the other 10.3V so there is an issue somewhere with the positive wire from the MPPT. I suspect a dodgy fuse holder. Thanks everyone for your input and advice.

battery chargingMPPT SmartSolarAGM Battery
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
wkirby avatar image
wkirby answered ·

If the MPPT reads 13.4V and the battery its self reads a different Voltage then that means that the battery is not connected to the MPPT for some reason, perhaps a wiring fault or a blown fuse or open circuit breaker.

3 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

eyacht avatar image eyacht commented ·
The wiring is pretty straight-forward as described above .. but why would a blown fuse or open circuit breaker cause the MPPT to read 13.4V? If the breaker or fuse to the battery has gone, wouldn't it read zero?
0 Likes 0 ·
seb71 avatar image seb71 eyacht commented ·
The MPPT would output voltage at its battery terminal if it has voltage at PV terminals from a PV array, even if not connected to a battery at battery terminals.


But you should not connect PV without a battery on battery terminals.
0 Likes 0 ·
eyacht avatar image eyacht seb71 commented ·
Really? I thought it would read the battery voltage. So you're saying the reading in the app (and at the MPPT battery output terminals) is the "produced" voltage and not the actual voltage at the battery?
0 Likes 0 ·
seb71 avatar image
seb71 answered ·

I have an MPPT 75/10 that has my 48V propulsion bank connected as PV in and the battery out goes to my starter battery.

Do not use a battery as PV input for any MPPT.

13 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

eyacht avatar image eyacht commented ·
Why not? Input voltage is input voltage; panel or battery doesn't matter.
0 Likes 0 ·
Alexandra avatar image Alexandra ♦ eyacht commented ·

@eYacht

It is outside of intended product design and use. There is a product whose intended use use is DC to DC charging - ...orion....

Mainly because the short circuit current for a battery is higher than the PV input is designed for.

The second is it is an mppt so meant to track its input.... A battery cannot be 'tracked'.

Basically it can't protect anything if it needs to without self destruction.

Likely in your setup right now the fuse has blown on the unit. Hopefully that is all that is wrong right now. Since you have no errors that is likely it.

1 Like 1 ·
Show more comments

Related Resources

MPPT product page

VictronConnect manual

PWM or MPPT

MPPT calculator

MPPT codes

Additional resources still need to be added for this topic

VictronConnect VE.Bus charging manual