question

Fabian Pagel avatar image

High voltage on MPPT 75/15 battery output, when BMS closes due to temperature

Dear all,

I try to figure out, if the behaviour I see is per design or not. In my van I have installed a Victron LifePo4, a BMS12/200 and a MPPT75/15 with 2x110W solar panels. Due to the current cold weather conditions (<5°C), the battery and the BMS shutdown the battery charging.

Whenever there is sun available, the voltage on my BMS load and the MPPT battery output increase to ~17V. I assume this is due to the battery shutdown for charging. As soon, as the battery is open (>5°C), the voltage decreases to a normal level.

Is that expected? I thought the MPPT will reduce somehow the voltage when there is no charging in progress.

Why I am asking the question? If put the MPPT battery charging minus on the BMS load pin, where all my other load is also connected to. Now I have ~17V on all my devices, as long as the battery is shutdown. Is my design correct or do I need to change something?

best regards,

Fabian

MPPT - Solar Charge ControllerBMSsolarvoltage
1 comment
10 |3000 characters needed characters left characters exceeded

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

Check the battery voltage the mppt is set to.

Update the mppt firmware, if not current version v1.46.

5 Answers
KevP avatar image

I have a LiFePo battery that can be charged down to -20 deg. Check to see if yours is restricted to the default 5 deg. If not, you can switch it off in the battery settings of the MPPT.

Share
10 |3000 characters needed characters left characters exceeded

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

Guy Stewart (Victron Community Manager) avatar image

Hi @Fabian Pagel

Do the answers to this question describe what you are seeing?

https://community.victronenergy.com/questions/38304/using-a-smartsolar-mppt-10030-with-a-common-port-b-1.html

Or is it something else?

Share
10 |3000 characters needed characters left characters exceeded

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

Fabian Pagel avatar image

@kai Unfortunately I can not heat up my batteries. So I need to solve the problem by configuration and that was my initial question, if I may have an configuration issue?

@M.Lange Yes, it is set to Lithium for sure. I read about absorption, is that maybe something, what I need to configure?

4 comments Share
10 |3000 characters needed characters left characters exceeded

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

sorry, that's about it from me. I don't have hands on experience with the MPPTs; don't know their expected behaviour if the battery is disconnected.

Do you have the 17V permanently or is it just a short peak?

Without battery the MPPT should maximal go to the absorption voltage.

Fabian Pagel avatar image Fabian Pagel Matthias Lange - DE ·

Unfortunately it goes up to ~16-17V and stays there..

Check the battery voltage the mppt is set to.

Update the mppt firmware, if not current version v1.46.


Known issues:
⦁ When connecting a power supply on the PV inputs, for example on a test bench, in combination with a battery (24V..48V) on the BATTERY input, a reset to default settings immediately triggers an error 38 (overvoltage). This enables the PV input short protection; and because there is a power supply connected; instead of a real PV array, the MPPT charger is damaged. Introduced in v1.26 and solved in v1.39.

kai avatar image

The underlying issue is the low temp (the BMS cuts out to protect the battery). Are you able to re-design the system with supplementary heating to keep the battery (& BMS) above the low temp threshold?


e.g.

https://community.victronenergy.com/questions/38030/lifepo4-low-temperature-protection.html

Share
10 |3000 characters needed characters left characters exceeded

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

Matthias Lange - DE avatar image

Is the MPPT set to lithium? If not you'll maybe get this high voltages due to the temperature compensation.

Share
10 |3000 characters needed characters left characters exceeded

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