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Power Jack 5000W ( LFPSW-5000)


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Hello All,

First of all, thanks to Genetrysolar for hosting this forum.

I know a fair bit regarding electronics, but it is always good to know people that work with

these specific inverters, so I do not need to re-invent the wheel without schematics.

I purchased a Power Jack LFPSW-5000, 220 volt / 24 volt years ago, and just recently started to use it.

If I look at the features, I most likely have the version 8.

The inverter works fine, swapped the thermostat ( TO-220 model ) for the fan to a 40ºC, since I do not like the inverter to run so hot, and I took the main

bolt and metal disc of the toroidal transformer to prevent heat trapped inside it and provide better cooling.

Inverter is running nicely. Even at higher and inductive loads, it is not really getting warm. It is just the charging that is giving me problems.

When I set the inverter to charge ( ups function and inverter without load ), it gradually starts to charge and after ± 40 seconds it reaches the peak charge of ± 1400 watts.

Looking at my shunt, it is charging 40 amps.

I have 4 batteries 12 volt 200 Ah to make a total of 24 volts and 400 Ah, so the 40 Amps charging is just fine when batteries are discharged to 50 %.

The only problem, the inverter's transformer overheats after ± 10 minutes of charging. And yes, thermistor is right, because it really gets hot.

When I leave the inverter "ON" for a while and let it cool ( in alarm, charging is OFF, but fan keeps running ),

I can restart the charging, and after stopping, cooling off, and starting a couple of times, I eventually get to the point where batteries are almost full, and the

inverter throttles down the charging current as expected, and from ± 800 watts charging down, it does not trip the temperature alarm anymore.

So, it is just at peek charging where the transformer overheats.

I tried to lower the battery spec. voltage setting on the inverter rotary switch, but it still charges at full capacitiy where it overheats.

Any idea if there is a possibility to lower the output current on the charger board or another way to tackle this problem. Thanks in advance for any ideas.


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9 hours ago, MarcvE said:

Any idea if there is a possibility to lower the output current on the charger board or another way to tackle this problem.

Technically, the constant current limit is set by a hardcode number in the CPU firmware.

However, this number is scaled by the tiny SMT "DIP" switches on the "charger" board.  This basically is a resistor assortment that shunts the transformer current readout.  If you turn one or more of these switches off, it will cause the fixed current limit number to be reached sooner.

BUT...there's a monkey wrench in the game: by turning one or more of those switches off, it will also reduce the "inverter overload" threshold (on the L1 circuit).  If you feel very electrically handy, it could be possible to wire up a circuit to adjust this "shunting" based on whether the AC Mains relay is on or off.

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Thanks for the reply.

I noticed the dipswitches on the charger board in your youtube-video about the version 9 board-set, but I have a version 8 that does not have the dipswitches.

The only parts I have close to the position of the dipswitches on the version 9, are some smd resistors that are marked as "adjust".

Any idea if these control the charge level ?



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I decided to leave the inverter alone. Will use a smart external charger to charge the batteries,and just use the PJ as inverter, which is working fine.

I needed to modify the system anyhow. Only charge when Solar PV is above ± 800 watts, and use inverter on

batteries when sun is down, until batteries are empty, and wait until next "sunshine" before charging again.

With a separate charger that will be a lot easier, PLUS, I don't have to rely on the PJ charger messing up my battery bank.

Thanks for the info, and will probably look into one of your inverters when I need one. Old but reliable LF technology.

Thx, Marc

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