question

skamp_x@hotmail.com avatar image
skamp_x@hotmail.com asked

Battery Protect not switching back on

Got Victron battery protect in my system, works and disconnects when battery voltage gets to low, but I do have 2 problems with it.
It will not switch back on when battery's are recharged and give a error code saying it detects a short circuit. while there ain't one, I assume it's because the inverter behind it wants to draw power when it switches back on, only solution is to disconnect the inverter , then reconnect it after the battery protect is on, far from ideal.. , second problem , using high loads (like 800 + watts) after a few minutes the voltage drops to a point the BP switches off (assuming battery's are getting low) even when they are still +60%.

Current system 2x80ah/12v AGM in parallel (efficient type connection)

150amp fuse , 12/24 100 Victron battery protect (set to disconnect at 11,3v)

a combo of panels totaling 300watt in parrallel

MPPT 100/20 Victron solar regulator ,12v 1500watt pure sin inverter.

Battery Protect
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.

1 Answer
ben avatar image
ben answered ·

Yep, when it switches back on, the inverter’s buffer caps take a huge current in-rush. The BP sees all that flow and decides it’s a short and shuts back down.

This is one of the reasons I don’t think anyone should use a BP with an inverter, or with any substantial load that is subject to inrush, really. They are much less useful in the real world than they look like they would be from the datasheet.

For the second problem, you need current-compensated disconnect if you want to handle that load situation for a battery that has a large voltage drop. You can’t do that with a BP, either, although you can use it as a one-way “relay” and control it from some other device that does make that calculation.

1 comment
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.

skamp_x@hotmail.com avatar image skamp_x@hotmail.com commented ·

Thank you for your reply, given me the needed info.

The system is ment to be partially off grid, so anything can still go grid if needed,

idea is to try use the batterys as much as possible (when enuf sun) ,to run stuff like tv , some lights , pc screen, microwave(high watt) ,to lower daily usage of grid power, and as backup if power goes down.

I'v been looking at the setup and I could reshuffle some parts and probably get the BP and inverter about 15cm closer to the batterys. (its about 60cm away now).

That should help a bit with the low voltage. During daytime the voltage added from the regulator would help making it no problem for high watt short use.

I do watch the battery status daily, the BP is a last defense incase I wasn't paying attention.

I will add another circuit breaker between the BP and inverter, and use it as a switch,

so if the BP disconnects , I open the breaker, let it reconnect, then close the breaker.

(so I don't have to disconnect the wires every time).

One added question though , would adding 2 more batterys in parallel make the voltage drop less? or thicker cables (or 2 cables instead of one).

0 Likes 0 ·