Capacitor pre-charge

[Djbodya]

So who has the answers on this. I'm running the EG4 6500EX with the EG4 server rack battery if I turn off the entire system battery and all do I need to precharge the inverter capacitors befor I turn it all on again? I don't plan to run the system 24-7 I want to be able to turn it on and off.

 

[burgerking]

10ohm for 60 seconds should be able to precharge the caps

 

[Jim Burrow]

Will P. using a 50 ohm Capacitor. I do too. If your controller is off for a good period of time, it is a good idea to pre-charge the capacitor with the resistor.

 

[boondox]

I use a 25 ohm resistor. I have a switch and fuse inline with it. Since I have two inverters I use a DPST switch, one side of the switch goes to one inverter, the other to the second inverter. The 25 ohm allows the inverters to boot up, once they are lit up I hit the breaker and kill the switch.

 

[burgerking]

50ohm, 25ohm would be safer than using 10ohm.

 

[Djbodya]

So what I'm understanding is even if my entire system is connected and I kept it off for 3 months, turning on the battery and after a few seconds turning on the inverter won't work? And also PV disconnect flipped on at that time can destroy the eg4 6500EX?

 

[burgerking]

So what I'm understanding is even if my entire system is connected and I kept it off for 3 months, turning on the battery and after a few seconds turning on the inverter won't work? And also PV disconnect flipped on at that time can destroy the eg4 6500EX?

That is not it.

Inverters in general will have very large capacitors, could be as large as a few farads, so much so, the mere action of physically connecting Battery to Inverter (or turning the Battery Breaker ON) will cause larger surge current, could be enough to blow the battery fuse, trip the battery CB or even kill the BMS's transistor(s). THESE are what we are trying to avoid.

However, if your battery is already physically connected to the inverter, the inverter's caps are already charged. no need to "precharge" even if the Inverter was off for a year.

 

[Djbodya]

That is not it.

Inverters in general will have very large capacitors as large as a few farads, so much so, the mere action of connecting Battery to Inverter will cause larger surge current enough to blow the battery fuse, trip the battery CB or even kill the BMS's transistor(s). THESE are what we are trying to avoid.

Yes I understand that. If I keep everything connected and turn the system on and off over the period or months will that cause potential problems or am I good to cycle it without any issues?

 

[timselectric]

As previously explained. You only need to consider pre charging, if power was disconnected.
If you don't disconnect the battery from the inverter, the capacitors stay charged.

 

[eshwayri]

eshwayri​

1 day ago
Question: I have a 150Amp "ignition protected" circuit breaker/switch between the battery bank and the inverter. It is always off when I plug in the batteries, and I use Anderson SB175 plugs on the battery terminals. I turn on the circuit from the switch. Do I still have risk of sparking/arcing at the battery terminals? I would think the risk is at the circuit breaker itself as the lugs on the battery are very well secured when the circuit goes live. I didn't see anything with my 12V AGM batteries and 1200 Watt inverter, but I am about to swap out the AGMs with LiFePO4s. Will the lower resistance from the LiFePO4s cause this to be an issue when it wasn't with the AGMs? The following year I might move to 24V and a 2000 Watt inverter. I won't be going larger for sure. Is it then that I have to factor in the pre-charge? or am I still too small? I will probably have to build a by-pass circuit to do the pre-charging since there are no loose wires to just touch the way it is shown in the video. My setup is for camping with everything except the batteries pre-connected and wired on a wooden back-board, with circuit breakers on every inter-connect (solar panels, inverter, load, and small fuse box for individual 12V power distribution). The batteries and the board plug in via Anderson SB175s. Power on sequence is first the fuse between the batteries and the solar charger, then the fuse between the battery and the inverter, and finally the fuse between the panels and the solar charger. Looking for advice.

 

[timselectric]

eshwayri​

1 day ago
Question: I have a 150Amp "ignition protected" circuit breaker/switch between the battery bank and the inverter. It is always off when I plug in the batteries, and I use Anderson SB175 plugs on the battery terminals. I turn on the circuit from the switch. Do I still have risk of sparking/arcing at the battery terminals? I would think the risk is at the circuit breaker itself as the lugs on the battery are very well secured when the circuit goes live. I didn't see anything with my 12V AGM batteries and 1200 Watt inverter, but I am about to swap out the AGMs with LiFePO4s. Will the lower resistance from the LiFePO4s cause this to be an issue when it wasn't with the AGMs? The following year I might move to 24V and a 2000 Watt inverter. I won't be going larger for sure. Is it then that I have to factor in the pre-charge? or am I still too small? I will probably have to build a by-pass circuit to do the pre-charging since there are no loose wires to just touch the way it is shown in the video. My setup is for camping with everything except the batteries pre-connected and wired on a wooden back-board, with circuit breakers on every inter-connect (solar panels, inverter, load, and small fuse box for individual 12V power distribution). The batteries and the board plug in via Anderson SB175s. Power on sequence is first the fuse between the batteries and the solar charger, then the fuse between the battery and the inverter, and finally the fuse between the panels and the solar charger. Looking for advice.

Pre-charge resistor is to protect the battery BMS, from the surge of charging the inverter capacitors.

 

[threepets]

will this work for the pre charge?

 

[Djbodya]

will this work for the pre charge?

If you have the eg4 battery the precharge is not needed the risisters on the battery precharge

 

[boondox]

If you have the eg4 battery the precharge is not needed the risisters on the battery precharge

Untrue, I think it depends on te size of the input capacitors. At least on my Magnum inverters with EG4's, I need a pre charge.

 

[timselectric]

Untrue, I think it depends on te size of the input capacitors. At least on my Magnum inverters with EG4's, I need a pre charge.

EG4 server rack batteries have built-in precharge resistor. Other EG4 batteries do not.

 

[boondox]

EG4 server rack batteries have built-in precharge resistor. Other EG4 batteries do not.

Well, mine are rack mount. Not sure if there are different ones, at least mine came with rack mount hardware.

I'd like to know how the built in pre-charge resistors work. DO they bypass the breaker or how exactly are they wired?

 

[timselectric]

Well, mine are rack mount. Not sure if there are different ones, at least mine came with rack mount hardware.

I'd like to know how the built in pre-charge resistors work. DO they bypass the breaker or how exactly are they wired?

When you first turn on the breaker. It goes through the Precharge cycle. Make sure that the connection between the batteries and inverter is available when you turn it on. (No other breaker or switch between the two in off position)

 

[OffgridMatty]

I have two EG4 Lifepower4 batteries connected to a Growatt 24v hybrid inverter. I've never pre-charged anything and was told the batteries have a pre-charge resistor integrated in. So far so good, as long as I turn on the DC breaker between the batteries and the inverter/SCC first.

 

[sollap]

will this work for the pre charge?

That resistor will work. It's 200 ohms though, so it'll take 4 times as long as a 50 ohm resistor would. No big deal, just don't rush it. Give it a few minutes, at 51.2v nominal it's only passing about 1/4 of an amp.

 

[boondox]

When you first turn on the breaker. It goes through the Precharge cycle. Make sure that the connection between the batteries and inverter is available when you turn it on. (No other breaker or switch between the two in off position)

Still curious as to how it is actually wired.