Ambot avatar image
Ambot asked

Battery BMS Triggers Short Circuit Protection when connecting Multiplus

tldr: When I turn the battery on with the Multiplus connected it registers a short circuit protection event. Help!


I've read thru the Battleborn thread and wondering if I'm suffering from the same issue, but its a little different.

I have 3 RJ Lithium 24V 300AH 150 cont/300 peak batteries and a Multiplus 24/3000/50/120

I wanted to use the multiplus to charge them up equally to parallel them.

I wired everything with a single battery powered "off" (charge and discharge disabled, FETs Locked)

The battery cable is 2ga and 26 inches long and feeds to a Lynx Distributor ->Lynx Shunt -> Lynx Distributor 2

I installed 150 mega fuses everywhere that needed one just to get the Multiplus configured and the batteries charged and paralleled.

The inverter cable is 1/0 and 5 feet long

When I turn the battery on without the multiplus connected, I measure 26.4v at the Lynx Distributor 2.

When I turn the battery on with the multiplus connected the BMS registers a short circuit protection event and shuts down.

The Multiplus is OFF.

I've attempted to precharge the Multiplus by hooking up AC as in the Battleborn thread and this did NOT change things.

I have not tried a different battery.

I have not tried connecting the multiplus directly to the battery using the 1/0 wire.

In general the "short circuit" has me freaked out.

Anything glaring above that would help sort this out?

Thanks for reading.

MultiPlus Quattro Inverter ChargerLithium BatteryBattery Protect
2 |3000

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

3 Answers
Ambot avatar image
Ambot answered ·

I obtained a 30w resistor and charged the caps using the resistor between the battery and negative cable.

It indeed no longer sparked when connecting the negative to the buss bar.

I then turned on the inverter, it made a buzzing noise, then a popping noise, then smoke came out the top vents



1 comment
2 |3000

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

alan avatar image alan commented ·

Is this picture showing the resistor you wired in?

0 Likes 0 ·
1612402305855.png (1.8 MiB)
Paul B avatar image
Paul B answered ·

you are seeing this as the INrush current is to high for the batteries.

you will need to precharge the Multiplus, you may get away with it by trying this

1.Turn the batteries on both on and both connected in parallel

2. turn the multi to off

3. connect the multiplus negative wire to the Batteries Neg terminal

4. VERY quickly touch the multis positive wire to the batteries positive connection do a - on /off / on /off and keep repeating this until there is no more sparking you must do this on/off/on/off VERY quickly.

5. once the sparks stop you can leave the positive connected and all should work fine. this is basically pre charging the multiplus capacitors in small steps

2 |3000

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

Ambot avatar image Ambot commented ·

Thanks for the reply. I gave that a go and the Bms shut down after a really impressive spark. It was in a more severe state than before requiring a harder reset to clear the short circuit protection event.

At this point there’s no way I can use this inverter and battery combo as it stands.

I suppose the battle born device is the way to go, but how can I rule out a defective multiplus that is shorting out the battery for real?

Just seems hooking an inverter to a very capable battery shouldn’t cause a meltdown. 6b2c9dfc-64bb-4f80-b710-b7cb289b398f.jpeg

0 Likes 0 ·
seb71 avatar image seb71 Ambot commented ·

If precharging the inverter capacitors is the cause, a safer method is to use a resistor or an incandescent light bulb (in a bulb base, with wires attached) and connect the positive wire through that first.

0 Likes 0 ·
alan avatar image alan seb71 commented ·

Yes, I agree with this. It’s the capacitors charging triggering an over current. Wire a resistor in the circuit initially, then disconnect it and reconnect the batteries shortly after.

0 Likes 0 ·
rslifkin avatar image
rslifkin answered ·

If you have AC power available to the Multi, bring it online with AC power first and let it start "charging" the not-connected batteries. This will charge the DC input caps, so you won't get the huge inrush when you close the contactor feeding the multiplus.

2 |3000

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