kenkoh
Solar Enthusiast
Want to make sure I get the right resistor.
Do I need tp precharge everytime before I turn the invertor on?ANY resistor helps massively. You just have to find a balance between resistance and rating.
Memory tool: About same volts in Ohms and 50% or more in Watts, e.g.,
24V system = 24Ω, 12W
You could round up to 50Ω and drop to 10W. More power rating on the resistor is never bad.
These would be great:
uxcell 2 Pcs Aluminum Clad Wire Wound Resistors 25W 30 Ohm 5%: Single Resistors: Amazon.com: Industrial & Scientific
uxcell 2 Pcs Aluminum Clad Wire Wound Resistors 25W 30 Ohm 5%: Single Resistors: Amazon.com: Industrial & Scientificwww.amazon.com
Do I need tp precharge everytime before I turn the invertor on?
If I never disconnect inverter from battery but turn it off, I can turn it back on without issue correct?You need to precharge any time you connect the inverter to the battery well BEFORE turning the inverter on. The battery connection is where the surge happens.
If you turn the inverter off, disconnect battery and, move a connection and then reconnect within a minute or so, you probably don't need to pre-charge again, but it doesn't hurt.
If I never disconnect inverter from battery but turn it off, I can turn it back on without issue correct?
Thanks. Solar is deep.Yes. In the off state, the inverter caps will stay charged.
Thanks. Solar is deep.
Anything. I've tried many from a few ohms to 200kWant to make sure I get the right resistor.
100w? Why? A 2w resistor works. you seriously don't need anything near that big. I usually use 5 or 10w sandbars a few ohms to 1k. Whatever i grab first in my parts bin...Works every time.I ordered some of these: https://www.ebay.com/itm/284470104226
50 Ohm 100 watt for my 48 volt setup.
Even if the input of the inverter would be a short, 50 volt -> 50 ohms = 1 amp (relative easy to find a push button that can do 1 amp)
P = UxI = 50 x 1 = 50 watt of heat disapation. so the 100 watt is a little bit of overkill ;-)
Anything. I've tried many from a few ohms to 200k
what did it do? Keep sparking? I've never had a problem. Hold it on a few seconds with unit off or it will spark some. How are you watching it charge. Shouldn't need but a few seconds then hook the wire.Have you actually used a 200kΩ resistor to precharge inverter caps? I tried a 600Ω one, and it was agonizingly slow.
It has to do with TC (Time constant), using 200K to charge about 10,000uF capacitor bank will take a long time (5TC) for the Voltage on the cap to reach the supply Voltage.what did it do? Keep sparking? I've never had a problem. Hold it on a few seconds with unit off or it will spark some. How are you watching it charge. Shouldn't need but a few seconds then hook the wire.
600 ohms into 100,000 uF would be 60 seconds time constant, charged about 63% of the way or 34 volts out of 54V.
After 3 to 5 minutes it should be mostly precharged, reducing the surge current to something in the 135A to 1000A range.
If a smaller inverter with smaller capacitor bank, would be much more fully precharged.
I don't get into all that I just grab a resistor that has a couple of W rating and put it on there and hold it for a couple of seconds and take it off and put my terminals on there and I've not had a spark problem on any of these invertersIt has to do with TC (Time constant), using 200K to charge about 10,000uF capacitor bank will take a long time (5TC) for the Voltage on the cap to reach the supply Voltage.
That is why we wonder how you come up with 'Anything. I've tried many from a few ohms to 200k'.I don't get into all that I just grab a resistor that has a couple of W rating and put it on there and hold it for a couple of seconds and take it off and put my terminals on there and I've not had a spark problem on any of these inverters
Works for me. I don't have any near that big. I have use these here. I mean you don't have to precharge you'll just get a nasty spark if you don't. And could have some bite marks. Anything is subjective. I wouldn't try a mega ohm rated Anything or over 1k. Look at my first reply. I said a few ohms to 1k. It doesn't need to be fully charged, you just don't want the spark. Maybe I'm doing it wrong , but I'm not getting a spark and I'm not using big values. Seems like common sense to me. Ohms law. Sometime when I find a 200k I'll try it and see what happens. LolThat is why we wonder how you come up with 'Anything. I've tried many from a few ohms to 200k'.