Precharge inverters
- Thread starter tammons
- Start date
sunshine_eggo
Happy Breffast!
With lead acid batteries, 24V+ or 2000W+
With LFP batteries, all.
With LFP batteries, all.
Yes definitely
sunshine_eggo
Happy Breffast!
In almost all cases, yes. The BMS registers the cap inrush as a short circuit and disables discharge.
If you'd rather not, a #2 pencil sharpened at both ends makes a great pre-charge resistor.
Awesome idea, never thought of that.
Wonder why nobody has come up with a time delay circuit to precharge the caps when you plug in an inverter?
I watched a video where the poster had a second terminal on the back of an inverter, touched it first with the + battery lead then hooked it up.
I assume the inverter had a resistor inside to precharge the caps.
I watched a video where the poster had a second terminal on the back of an inverter, touched it first with the + battery lead then hooked it up.
I assume the inverter had a resistor inside to precharge the caps.
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Some think you need a big honking 50 Watt resistor or better. With my Magnum MS4448PAE inverter (4400 Watts, 48vdc), a 50 ohm 10 Watt doesn't even get warm. There's a momentary current of 48vdc/50ohm=0.96amp for a fraction of a second dissipating 0.96*0.96*50=46.08watts, but it taiils off before my 10watt resister starts to get warm (don't turn the inverter on until after the main breaker is on). On my panel I have room for extra DC breakers, so added a breaker+resistor in parallel with the main breaker, a push button might be better if you have a place to mount it. I doubt there's an inverter out there with caps big enough to where such a 10watt resistor is not sufficient. I also use another 50ohm 10watt across the connection from battery to PT-100 charge controller, as that can give a bit of an arc too. Here's ten "10W 50 ohm Wire Wound Resistor" for $0.35/each: https://www.amazon.com/gp/product/B0BR6GRCHL A #2 pencil lead from end to end is about 25 ohms, should work fine if that's all you got (expose the lead on the ends leaving most of the wood to absorb any heat) but would be a harder to permanently install and is more fragile.
Some of the packaged batteries have it built in. I had been using a pencil and then moved on to a switched resistor and then one day had Dan who owns Trophy battery on the phone and he pointed out there is a pre-charge in their batteries that you have to press the reset button and cycle the battery to activate - duh. EG4 looks to have it built into their batteries , SOK too, probably others.
Trophy:
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