Does anyone have a link or suggestion for a 24v precharge resistor.
Inverter capacitor charging spark!
- Thread starter atatistcheff
- Start date
And I just connect one to my battery and positive side of inverter for how long
Any incandescent light bulb will do... I’m just saying...
10-30 seconds should be long enough
TheGriz
More Power Scottie!!!
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Could you please an post an ebay/amazon link for the resistor you are referring.
Heres a silly question but how exactly do you put this tiny resistor inline with a 2/0 battery cable? Or is it on its own wire running from inverter to battery?
I first hook up the negative cable.
Then I hold one end of the resistor on the positive terminal and touch your 2/0 cable to the other end. A few seconds later you are done. Hook up the positive cable and go about your day ?
In case anyone wants to see this process done:
I have a marine battery selector installed on my bank, I put a light bulb on the #1 position, and the 1/0 cable on #2, I first select #1, the light bulb glows for a sec, then dims. Then I switch to #2... done.
Take a look at Will’s video at 19 seconds in.
He mentions damage to your BMS so Victron need not address that issue.
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
This is what I do:
https://diysolarforum.com/resources/inverter-disconnect-switch-with-precharge.60/
A couple of notes:
1) I like this better than a push-button because even if you rotate the switch quickly, you will at least partially pre-charge the caps, but it is easy to forget to press the push-button.
2) When I first developed the design in the resource, I was worried about the case where someone leaves the switch on pre-charge *and* has the inverter on. In this case I was worried about a lot of current going through the pre-charge resistors and overheating them. Consequently I put the PTC resisters in to act as a limiting device to prevent any problems. I have since tried this on three different inverters and if you leave the switch on pre-charge while the inverter on, the inverter detects low battery and does not fully turn on. Consequently, the pre-charge resistors never heat up. I am debating whether I should remove the PTC from the design but I don't know if the sample of 3 different inverters are representative of all inverters.. (I did not put the PTC in the last build I did because the inverter I was using did not need it)
https://diysolarforum.com/resources/inverter-disconnect-switch-with-precharge.60/
A couple of notes:
1) I like this better than a push-button because even if you rotate the switch quickly, you will at least partially pre-charge the caps, but it is easy to forget to press the push-button.
2) When I first developed the design in the resource, I was worried about the case where someone leaves the switch on pre-charge *and* has the inverter on. In this case I was worried about a lot of current going through the pre-charge resistors and overheating them. Consequently I put the PTC resisters in to act as a limiting device to prevent any problems. I have since tried this on three different inverters and if you leave the switch on pre-charge while the inverter on, the inverter detects low battery and does not fully turn on. Consequently, the pre-charge resistors never heat up. I am debating whether I should remove the PTC from the design but I don't know if the sample of 3 different inverters are representative of all inverters.. (I did not put the PTC in the last build I did because the inverter I was using did not need it)
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gnubie
Solar Wizard
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Victron isn't a cheapie Chinese manufacturer so you can expect decent quality components. Try dead dropping a crappy 2000uF electro capacitor onto a 200 amp power supply 30 times and let me know how it performs after that ...
*edit*
added 'dead'
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
In the inverter, the only thing that is taking the current is the capacitors and wires (and *possibly* a shunt) so it is not a surprise the inverter manual does not mention it. Several folks have commented that the inrush is bad for the capacitors. I can not say they are wrong, but I am not sure how the current would damage them.
The surge current through the battery is probably not good for the LiFePO4 cells, but my guess is the surge is so short the cells handle it with little or no damage.
Where things get 'interesting' is the surge current through the BMS, In this case you are putting a momentary but monster current through the FETs of the BMS. In many cases, the BMS will detect this as a short circuit and shut off. (You can see this in a few of @Will Prowse videos). Even if the BMS does not shut off, the surge through the FETs can damage them.
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Legs of capacitors are relatively thin, so are PCB tracks ... large currents, even momentarily, could cause enough heating effect to damage them?
gnubie
Solar Wizard
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Damage can be hidden within the capacitor too. The joint between the leg and the sheet can be degraded, oxides can form on the foil, both increasing the ESR significantly and the latter reducing the capacitance too. Quality capacitor manufacturers provide this info, I'm sure a Google search will turn up heaps of info if anyone wants to do more reading about it.
I've mentioned it before but there is a class of capacitor specifically for high current flows, pulse capacitors. You'll find them in applications like electric fence controllers, very high ripple current applications etc.
I've mentioned it before but there is a class of capacitor specifically for high current flows, pulse capacitors. You'll find them in applications like electric fence controllers, very high ripple current applications etc.
But if there's other loads than the inverter the PTC is still useful as they usually don't have LVD unlike the inverter.
NB: in the last page of the ressource the last diagram title should say 48 V instead of 24 V. Also most of the resistors values aren't standard and will be hard to find and more expensive, you should pick from the E12 series (or the E24 one if you really need closer values)
I doubt very much you'd see this inrush with a clamp meter, maybe a modern oscilloscope. These unrestricted inrush currents would only last for milli-seconds, certainly less time than it would take to blink.
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FilterGuy
Solar Engineering Consultant - EG4 and Consumers
OK.... I would not have expected such a short surge to effect the traces or component leads.
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