Safe Start Procedures for Hybrid Inverters?

[Crowz]

Well yeah but these are 1500 dollar Chinese inverters we’re talkin here…lol

My $1300 LF inverter has no problems doing it

 

[ksmithaz1]

it's not the A/C load it's the massive surge used to charge the caps in the inverter. This happens with all Growatt, Victron and EG4 6000XP inverters. I always used a resistor to charge the caps but on this new install i tried just powering the device on. The first inverter is not an issue because of the caps in the battery but the issue is the second / third inverters. 25 kw of battery's won't start the 2nd inverter even with no A/C load on the first inverter. Since the EG4 6000XP has a D/C breaker I hate to install another cutoff switch with a precharge resistor on each one but I may have to.

I wish the inverter company's started putting in a precharge state on powering on the device.

If you are already committed to hardware you own, then you could probably do this with a fat relay, and a relatively fat bypass resistor, around the relay. You would want the inverter plus side to feed a cap and a couple of resistors for the control side of the relay with an RC of 2-4 seconds, maybe less. You are not looking for precision, just a delay, then kick a relay once the cap charges, if the power goes out, figure the cap size for the time you want to delay the break, and prevent a brown down from popping the relay based on the current draw of the relay coil.

 

[Lighthouse Beacon]

My $1300 LF inverter has no problems doing it

Yeah @Crowz but all the cool kids are doing hf. All the @42OhmsPA followers would make fun of me I get a 6048!!!!

 

[timselectric]

I've seen numerous discussions about 'pre-charge' for inverters. It would seem to me that if this is necessary it would be handled trivially in the inverter with a relay, and a ballast resistor in front of the 48v caps. As soon as the caps hit the proper voltage level, the relay kicks on bypassing the ballast resistor. Same principle as a "Power Good" circuit on most electronics boards, only with a relay instead of an IC. I would consider this a design flaw if this was necessary to prevent damage or creating a fault, to a battery/ on a BMS. Having to manually "pre-charge" an inverter sounds pathetic.

Every inverter has capacitors. And every BMS has a current limit.
You could call it a design flaw. But being diy'ers , we are the designers of our own systems. It's not a damaging situation. And it's not a problem with FLA batteries.
It only started being a problem when we switched to BMS controlled batteries. If allowed to, the capacitors can take a full charge in a split second. Which can be over 300a , for a split second. And LFP (Unlike FLA) batteries have no problem giving that out. But the BMS's see this as a dead short and shut down for safety.
If you have enough BMS capacity in your system, then there's no problem. If you're trying to build your system on a budget, you may need to add a precharge circuit.
I've never had any problems with this personally. Because my system started with a single inverter. And a LiFePower4 server rack battery, which has a built-in precharge circuit. And by the time I put in the second and third units, I had plenty of battery. Or actually BMS capacity.

 

[timselectric]

I just flip the main load panel breaker on and off not individual breakers.

I don't even do that. I just let the system fire up with all loads connected and waiting for power. It's no different than if it shuts down from being overloaded and automatically restarts.

And it's a $700 high frequency unit.

 

[timselectric]

Since the EG4 6000XP has a D/C breaker I hate to install another cutoff switch with a precharge resistor on each one but I may have to.

I would put it at the buit in breaker. Keep it as simple as possible. You just need a DPST push button.