question

jasontav avatar image

LiFePo4 Smart and Battery Protect on the charger side going into short circuit after restart

I had a scenario where the batteries told the ve.bus BMS "allow to charge:NO" because the battery temperature was below 5°C - well one battery was, see my unanswered question here: https://community.victronenergy.com/questions/34077/smartlithium-battery-temperature-sensor-believable.html

Since I never got an answer for this, I am using the BMS and the temperature of the battery as measured internally as the "source of all knowledge" to control the chargers, rather than the temperature reported by the BMV-712.

This in turn turned off the battery protect on the charger side (I have 1x BlueSolar 150/70 and 2x SmartSolar 150/35 there)

All good so far.

However, when the temperature increased, and the BMS changed to "allow to charge:YES" the Battery Protect (configured in Li-ion mode) eventually went to error E1 - short circuit.

When I measured the voltage on the charger side of the BP it was ~30V - battery side was ~26V.

I then disabled the chargers using Victron Connect, restarted the battery protect by removing and replacing the remote connection from the BMS, waited until the BP had configured, then restarted the chargers one by one.

The system came up.
Obviously I don’t want to have to do this every time the system shuts down due to low temperature.

Any help appreciated.

MPPT - Solar Charge ControllerBattery Protecttemperature
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2 Answers
rpetrovski-forum avatar image
rpetrovski-forum answered ·

So, just had a pleasure of experiencing similar issue. When MPPT takes battery voltage from smart networking or from DVCC, it tends to raise its side voltage when BP is open quite high. 16+ volt on 12v system. And it is a pretty cloudy day today. When BP engages, it sees high inrush and thinks a short circuit is going on. One of workarounds is to turn off DVCC and remove MPPT from smart network group. Works for me but brings up the question of why victron wouldn't patch MPPT to be a bit smarter about battery voltage source when charge current is 0.

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Just had exactly the same problem with my smart bp 12/24 65.. used to isolate my mppt 100/30 from the lithium’s when the bms instructs a load/charge disconnect. The mppt 12 charge side creeps up to 16 volts and then when the bms cl12/100 enables charge again to the battery protect, it senses a current inrush and throws an E1 or e4 short circuit, or over voltage error... It just so happens my mppt( it’s actually a blue solar with a Bluetooth dongle) is connected as a network to my bmv. I will disconnect them tomorrow and see if it solves the problem. There is no need for them to be connected, as them sensing is being taken care of by the bms...

JohnC avatar image
JohnC answered ·

Hi @JasonTav.

Putting aside your temp issues totally, what is the purpose of your BP?

They aren't designed for reverse current on a charger circuit, so why is it there?

I may be missing something here, but perhaps this is your deeper issue. We need more info to see what you're doing with this BP.

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This is the only allowed configuration where there is a potential for reverse current, as it is very small. I can't locate the comments from victron that confirm this, but it is in this labyrinth of a forum somewhere......


The reason I am using it is so that the BMS (or, the "source of all knowledge about the batteries") can control the chargers


perhaps @Guy Stewart (Victron Community Manager) can pitch in with that confirmation......

Smart networking the bmv and mppt's together will provide the mppt's with temp data, and will stop charging below 5c.

I have a Venus device and according to the Smart Networking FAQ you shouldn't use Smart Networking if you have a GX device.


Besides I want to use the batteries temperature sensor to control charging (via the BMS), not the BMV-712 temp sensor.