No pre-charge resistor solution
- Thread starter pollenface
- Start date
Bossrox
Solar tinkerer
Would have been faster using the resistor but if you don't have 1 handy, an old filament style 100 watt light bulb will do just fine.
pollenface
Solar Wizard
yeah I didn't have one of those bulbs handy either, definitely If time is of the essence, don't do it my way, it was an extra 5-10 seconds of life that I'll never get back 
sunshine_eggo
Happy Breffast!
#2 pencil is about 6Ω and works well.
2Big2B
Free Wheeler
Really?
I am really sure if I need to worry about a 600W 24V Inverter, until I receive it later today.
I was trying to make out which resister Will used in his video about "Charging" the inverter's caps . And his is a bigger inverter too. Is it an "NTE RESISTOR 25 WATT 20 OHMS CEMENT WIREWOUND FLAMEPROOF 25W020" ???
Else an old light bulb. I might have some 12v auto bulbs that I could use to make a cool tool for that but if a pencil works I won't need to spend any money.
Really? #2 pencil ???
Those I have !
10-gauge
(16843)
Brucey
Solar Wizard
For such a small inverter I doubt you'll trip any battery BMS. I don't need to precharge my Victron 48/1200.Really?
I am really sure if I need to worry about a 600W 24V Inverter, until I receive it later today.
I was trying to make out which resister Will used in his video about "Charging" the inverter's caps . And his is a bigger inverter too. Is it an "NTE RESISTOR 25 WATT 20 OHMS CEMENT WIREWOUND FLAMEPROOF 25W020" ???
Else an old light bulb. I might have some 12v auto bulbs that I could use to make a cool tool for that but if a pencil works I won't need to spend any money.
Really? #2 pencil ???
Those I have !
10-gauge
(16843)
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 20,135
I don't need to pre charge my 5k's , because I have plenty of BMS available.
Q-Dog
¯\_(ツ)_/¯
I didn't precharge our Victron 24 volt Multiplus 3000. To be fair, I think I have only shut it down once or twice since I powered it up a few years ago. 800ah of storage split up between 4 batteries/BMSs.
Oh, right, I didn't precharge our 24/1200 either.
Oh, right, I didn't precharge our 24/1200 either.
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
If you have a bank of packs the "need" for the pre-charge becomes moot. That surge pull is short and divided between the packs which lessons it and does not cause the BMS' think they have a short and shutoff. I don't know what the threshold is but from my experience 2 packs with 200A BMS in Parallel handle it without a blink.
NOTE: I always install a battery on/off switch between inverter system & bank. With all batteries connected & ON, flip the switch and powerup inverter and the momentary surge as seen on the BMS' is just a blink (too fast to even see the Amp Draw it's that fast)
NOTE: I always install a battery on/off switch between inverter system & bank. With all batteries connected & ON, flip the switch and powerup inverter and the momentary surge as seen on the BMS' is just a blink (too fast to even see the Amp Draw it's that fast)
OffGridForGood
Catch, make or grow everything you can.
Is there any benefit to having a dedicated pre-charge resistor for the life of the Caps?
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 20,135
Mahendra Gomanie
New Member
JK's and OIverkill do a great job when you have enough.
I have started 4k and 6k inverters with just one JK or overkill.
Started some 8k Outback Radians with just two jk or Overlkill as well.
But I am getting to like the filament bulb strategy, Safe and soft start.
Mahendra Gomanie
New Member
The only problem I have with manual pre-charging is that it can be cumbersome, especially when you have separate battery/inverter breakers.
It's a good thing I have small hands, but scared as hell, even though I have done it countless times.
Those expensive Fortress Eflex have nice pre-charge functions and all batteries synchronize nicely when powered on in sequence.
Feels like the inverter is in heaven.
It's a good thing I have small hands, but scared as hell, even though I have done it countless times.
Those expensive Fortress Eflex have nice pre-charge functions and all batteries synchronize nicely when powered on in sequence.
Feels like the inverter is in heaven.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 20,135
Shouldn't matter what brand. Just the size of the capacitors and the discharge limit of the BMS/s.
As long as the capacitors don't draw more than the BMS limit, it's all good.
marionw
Solar Addict
The pre-charge resistor also protects the inverter from a massive in-rush of current. In many cases the large capacitors are mounted on a printed circuit board (copper trace usually built up with solder to increase current capacity). A large in-rush of current could potentially delaminate the copper trace from the underlying board.
Capacitors in DC Circuits
In dc circuits, when a dc voltage is first applied to a capacitor with no charge, it initially acts almost as a short circuit by allowing a maximum value of current to flow
en.wikipedia.org
Many BMS's have a pre-charge resistor built in. For me, with my SunGoldPower inverter's switch in the off position, I close the breaker on one EG4 LifePower4 battery which automatically uses a build in pre-charge resistor to charge the capacitors in the inverter and is does also prevent a large current from tripping the BMS
Capacitors in DC Circuits
In dc circuits, when a dc voltage is first applied to a capacitor with no charge, it initially acts almost as a short circuit by allowing a maximum value of current to flow
Pre-charge - Wikipedia
Many BMS's have a pre-charge resistor built in. For me, with my SunGoldPower inverter's switch in the off position, I close the breaker on one EG4 LifePower4 battery which automatically uses a build in pre-charge resistor to charge the capacitors in the inverter and is does also prevent a large current from tripping the BMS
Mahendra Gomanie
New Member
Nice, I asked for a scientific explanation as to why inverters should be precharged besides causing BMS to trip but didn't get a good answer.The pre-charge resistor also protects the inverter from a massive in-rush of current. In many cases the large capacitors are mounted on a printed circuit board (copper trace usually built up with solder to increase current capacity). A large in-rush of current could potentially delaminate the copper trace from the underlying board.
Capacitors in DC Circuits
In dc circuits, when a dc voltage is first applied to a capacitor with no charge, it initially acts almost as a short circuit by allowing a maximum value of current to flow
Pre-charge - Wikipedia
Many BMS's have a pre-charge resistor built in. For me, with my SunGoldPower inverter's switch in the off position, I close the breaker on one EG4 LifePower4 battery which automatically uses a build in pre-charge resistor to charge the capacitors in the inverter and is does also prevent a large current from tripping the BMS
This explains a lot.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 20,135
I have never seen an inverter with a built in pre-charge resistor.
Which they would have, if the manufacturers were concerned about it.
Mahendra Gomanie
New Member
not all inverters have an off button, Most like Outback, Midnite, Victron, Schneider do not,The pre-charge resistor also protects the inverter from a massive in-rush of current. In many cases the large capacitors are mounted on a printed circuit board (copper trace usually built up with solder to increase current capacity). A large in-rush of current could potentially delaminate the copper trace from the underlying board.
Capacitors in DC Circuits
In dc circuits, when a dc voltage is first applied to a capacitor with no charge, it initially acts almost as a short circuit by allowing a maximum value of current to flow
Pre-charge - Wikipedia
Many BMS's have a pre-charge resistor built in. For me, with my SunGoldPower inverter's switch in the off position, I close the breaker on one EG4 LifePower4 battery which automatically uses a build in pre-charge resistor to charge the capacitors in the inverter and is does also prevent a large current from tripping the BMS
You have to make use of their Breaker as the on-and-off switch.
I wonder about the reasoning for this.
Mahendra Gomanie
New Member
Dont think there are any.
This was discussed on another thread .
Can't remember the exact reason for not engineering into the inverter's design but I recall some guys mentioned some complications as a result it was built into batteries instead.
The Split phase inverters from WZRELB come with a terminal that is next to the normal positive battery terminal that allows you to pre-charge the capacitors.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 20,135
It's only added to some BMS's , because it's only an issue for BMS's.
Precharging wasn't a thing until BMS's were introduced.
Brucey
Solar Wizard
Victrons have a switch: on/off/charger only.
Q-Dog
¯\_(ツ)_/¯
What Victron inverters do not have an off switch? Both of mine do.
Even with the victron units off those caps are still dead and need charge to system voltage. I’ve used 1 ohm 25w resistor and get a little spark on my MPII 24v 3k. Once charged, and unit off, idle consumption is very minimal, less than 1w as I used a lab powersupply with current limited first time I energized, it showed zero idle m.
After removing the resistor I can watch the voltage fall after 15-20 seconds voltage was back to zero.
After removing the resistor I can watch the voltage fall after 15-20 seconds voltage was back to zero.
Mahendra Gomanie
New Member
ok seems I was wrong about the Victrons.
Similar threads
