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SmartSolar battery voltage spike

I have a SmartSolar 250/100 mc-4 with 3 280W panels connected to it. All goes to a 200 ah 12v lithium battery. Today I experienced voltage spikes from 13.9 to 26v and back multiple times. It burned my inverter and the house almost caught fire. What is the cause? Anyone?

battery system voltage
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kosio86 answered ·

Hi,

I had the very same issue with my brand new setup today.Brand new 200Ah Lifepo4 battery was at 13.3v showing 88%. No loads were ON. SmartSolar was Floating and not charging. I turned the Fridge ON and Smart Solar started providing 3A of power. Battery was providing just 1A of the total 4A the fridge needed. Then I turned off the fridge using a breaker after Smart Battery Protect 100 and I got 16.5V spike at the BP and at the Smart Battery Sense BP threw E4 for high Voltage. Fortunately, nothing burned as my spike went to 16.5v only and probably BP disconnected the loads due to E4. I am concerned that this may got dangerous if heavier load is disconnected instead of the fridge. I am using 35mm copper wire with copper lugs crimped with hydraulic crimper. It is definately not a problem with the cables. I had the same system before but was with Lead acid battery and without Smart Battery sense. I haven't noticed voltage spikes back then.

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WKirby avatar image
WKirby answered ·

In what part of the circuit were you measuring the Voltage?

Poor wiring or a loose connection is the first thing that comes to my mind. If the battery was soundly connected, then it would be impossible for the Voltage to suddenly double.
A poor connection can easily cause the impedance of the circuit to suddenly rise and therefore the MPPT output Voltage will jump up abruptly whilst it is charging (maybe 800W at a guess?).
There will probably be a spark, the connection becomes acceptable again and the Voltage goes back to normal.

A lithium battery has a very low impedance, it will be physically and chemically impossible for 800W of power to suddenly raise the battery Voltage by x2 unless there is something wrong with your battery which is unlikely. If the MPPT failed and at worst tied the PV array directly to the battery there is still not enough power jump right up to 26V.
Only a high impedance fault, wiring / connection issue can cause this mode of failure.

Please check all of your connections and wiring. Something is wrong there.

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I checked the wiring and all is fine.. Can’t be the cause. MC-4 on PV side. Bolted battery terminals on battery side. Controller direct to battery with short cables. Nothing out of the ordinary. My history on phone app for yesterday shows max PV voltage 35.21 and max battery voltage of 28.1! Min battery voltage same day is 12.95. Other days my max battery voltage does not exceed 14.30. On position 7 (lithium) at the dial.

What batteries are you using? and do you have pictures of the install / wiring?

Could also be a battery with internal disconnect BMS inside, that is overcharged and opens connection, in combination with incorrectly configured MPPT? (24v setting?)