Pre-charging inverter capacitors?

I’ve seen videos that say you need to pre-charge the inverter capacitors using a resistor when starting up a system that has Lithium ion batteries to prevent a rush of power. I can’t see how there would be a rush of power if the inverter is off and you follow the sequence in the owners manual. The battery manufacturer said he never heard of that happening unless the output was on and there was a load when it was turned on. I’m going to be starting my new 1100ah system for the first time soon and I was wondering if anyone has experienced damage to the inverter by following the sequence of turning on one battery breaker, then the breaker to the inverter, then powering up the inverter, followed by the other battery breakers, then turning on the utility breaker then turning on the output breaker and last the panel breakers. Also, my system has a 250 breaker from batteries to the inverter, a 100 amp breaker from each battery to the bus bars, a 100 amp breaker from each charge controller to the bus bars and a 60 amp breaker with lightning protection on the combiner boxes, is there anything I’m missing? This system has been running on gel batteries so far with no problems. Any suggestions would be greatly appreciated. the dog

In case anyone else is wondering about this. Turn on the breaker to the inverter, turn on the breaker from one battery, then turn on the battery on/off switch. It does the pre-charge. Then turn on the inverter, then all the other breakers then the batteries one at a time. If the battery doesn’t have a on/off switch you need to use a resistor to pre-charge the inverter capacitor first.

Yes, a common issue. The inrush current to the capacitors happens when the battery isolator is first turned on. This is normal, the spike can cause some (sensitive) lithium batteries to trip off or shut down. The more batteries that are ON the better because the spike is shared between them.

I had this issue using Pylontech batteries connected to a Multiplus inverter. A large resistor and two-pole DC startup switch to trickle charge the inverter capacitors is a good idea. The Selectronic SP PRO inverters have this already built into the inverter.

It seems these batteries I bought have that in them as well. Monsoon Season started the day I competed the installation and have only had one day of full sun. But even so they will often run the night even with a 50% charge.

  1. For lithium batteries, BMS will protect the battery and will not cause damage to the battery and inverter.
  2. When the BMS is powered on, it first charges the capacitor of the inverter through the resistor(Precharge circuit) to protect the lithium battery. If there is no resistance(Precharge circuit), the current through the battery will reach more than 1000A, which will damage the life of the battery or cause a safety accident.
  3. The BMS needs to match the inverter to ensure the battery starts up smoothly. Otherwise, the battery will fail to boot due to excessive current. If this happens, you can quickly press the switch of the battery several times to fully charge the capacitor of the inverter, so that the battery can be turned on. But there is still a large inrush current, which is not friendly to the battery. The best inverter is that the battery is matched.

Thanks for the info!