Pre charging Multiplus 3000W

[Mountainlion]

I have a Victron Multiplus 3000W with 2xSOK 280Ah installed in a boat.

That means I switch off the main battery switch when I do not use the boat. So Multiplus is disconnected.

Is there any pre charge circuits built in to the batteries?

How long does the capacitors stay charged?

As my Inverter is connected with a two position switch I normally start the system with the switch in the lead/acid position. Then when it is working I switch over to LFP.

Is that a safe method?

 

[sunshine_eggo]

I have a Victron Multiplus 3000W with 2xSOK 280Ah installed in a boat.

Is there any pre charge circuits built in to the batteries?

highly doubtful. Typically only the server rack batteries have that function when specifically engaged, i.e., you follow a specific startup procedure.

How long does the capacitors stay charged?

Enough seconds to allow you to take a resistor out of the circuit and then make the battery connection without an additional spark.

As my Inverter is connected with a two position switch I normally start the system with the switch in the lead/acid position. Then when it is working I switch over to LFP.

Is that a safe method?

Are the positions isolated, i.e., on 1 you have lead acid, and on 2 you have LFP, but they are never in parallel?

If so, that should be mostly fine (you are still getting a spark in the switch); however, you don't need to turn the inverter on. Simply making the battery connection charges the caps, so going from off to 1 (lead acid) for a few seconds and then on to 2 (LFP) and THEN turning the inverter on should be fine.

A #2 pencil sharpened at both ends is an effective pre-charge resistor if you ever need to go that route.

 

[Mountainlion]

highly doubtful. Typically only the server rack batteries have that function when specifically engaged, i.e., you follow a specific startup procedure.



Enough seconds to allow you to take a resistor out of the circuit and then make the battery connection without an additional spark.



Are the positions isolated, i.e., on 1 you have lead acid, and on 2 you have LFP, but they are never in parallel?

If so, that should be mostly fine (you are still getting a spark in the switch); however, you don't need to turn the inverter on. Simply making the battery connection charges the caps, so going from off to 1 (lead acid) for a few seconds and then on to 2 (LFP) and THEN turning the inverter on should be fine.

A #2 pencil sharpened at both ends is an effective pre-charge resistor if you ever need to go that route.

Thanks. The switch is isolated. Lead and LFP never parallel.

Going from 1 to 2 probably goes faster than using a resistor and then turning the switch.

 

[Dooug]

I use a extra blue seas battery switch part number 6011 for my multiplus 3000 combined with a resistor. I turn it to "on", it precharges (i just wait a few seconds) then to "combine" and leave it. Works great so far, have not kicked a BMS out yet.

I followed the instructions from this document on the forum https://diysolarforum.com/resources/inverter-disconnect-switch-with-precharge.60/

 

[RCinFLA]

If your boat runs on gasoline you have another consideration of wanting to avoid sparks setting off gasoline vapors trapped under floorboards.