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WZRELB Reliable Inverters Low Voltage Cutoff Mod How To

heavy-impact

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If you have one of these off grid inverters and the low voltage cutoff activates out of spec or you just want to adjust the low voltage cutoff lower or higher you can do this mod. You will need a few inches of 30 gauge wire and a 10K trimmer pot, (I like the 15 turn ones) and a soldering iron with small tip. It helps to have a magnifying visor and a hot glue gun.

Disconnect the inverter from any power.
Remove the cover from the inverter.
Locate the voltage regulation board just in front of the short heat sink.
Remove the R11 resistor with a soldering iron and tweezers.
Solder a couple inches of wire onto the center leg and either outer leg of the trimmer pot. Doesn't matter which outside leg just use one or the other.
Connect a ohm meter to the trimmer center leg and whichever outside leg you plan to use and set the trimmer to 5000ohm.
Solder the two wires from the trimmer pot to the R11 solder pads where you removed the resistor.
If you have a benchtop power supply you can power the inverter from it to set the low voltage cutoff using the trimmer, otherwise set it with a low battery.
Lower the trimmer resistance to lower cutoff voltage. Increase resistance to raise the cutoff voltage.

I put hot glue over my alarm because I hate it and don't need it.

If you're not comfortable doing this type work then pay someone else to do it.


reliable inv.jpgV comp board - (1).jpgV comp board - (2).jpg
 
I have been trying to figure out how to cut off my inverter at a higher level than my DC loads ... This solves that.

Thank you for posting it.
 
Very nice mod! I've been looking at this inverter manufacturer.

I currently have a a 36v setup and planning to go to 48v in the future. How much lower can we set the cutoff without getting into trouble?

For example, on the 48v inverter, the factory alarm is set at 42v and the cutoff at 41v. Could someone go as low as 38v for the cutoff? This would let me run the inverter on the 36v battery for a while before I upgrade the battery to 48v
 
Very nice mod! I've been looking at this inverter manufacturer.

I currently have a a 36v setup and planning to go to 48v in the future. How much lower can we set the cutoff without getting into trouble?

For example, on the 48v inverter, the factory alarm is set at 42v and the cutoff at 41v. Could someone go as low as 38v for the cutoff? This would let me run the inverter on the 36v battery for a while before I upgrade the battery to 48v
The spec for my 36v version is low alarm at 30v and shut down at 29.5v but mine was doing both at 32.5v. After the mod I set the shut down at 30V. You may not get more than 2.5v lower than the factory setting.
 
The spec for my 36v version is low alarm at 30v and shut down at 29.5v but mine was doing both at 32.5v. After the mod I set the shut down at 30V. You may not get more than 2.5v lower than the factory setting.
Make sense but thought it might be worth a try to check. I know Victron makes a 48v inverter that will also work for a 36v battery.
 
You may want to solder the wiper to one end of the pot so that if the wiper fails to make contact (and believe me they do) it defaults to the resistance of the track instead of failing open circuit. This way you have it can either result in the inverter to stop working (thinks the voltage is too low) or the low voltage protection is completely disabled.

Besides that, good job, how did you figure out it was that resistor? I'm currently stuck finding a 24V 2000W inverter for a 6s pack (needs to shut down at 18V instead of 19.5 that most do).

Another simplier approach would changing the voltage after the power switch, so far what I've seen is that the power switch in a inverter interrupts just the supply voltage to the control circuitry (that is voltage at the switch leads = battery voltage), that means for example if you want to use a 4s pack (charge to 16.8V max) in a 12V inverter (usually shuts down at 15V) by putting two diodes in series with the switch you would bring down the voltage at the control circuitry by 1.4V so it will shut down at 16.4V instead of 15V. Add more diodes if you want to increase it (wouldn't go above 17V) it also has the plus of increasing the low voltage disconnect.

Now to increase the low voltage disconnect for example using a 3S pack in a 12V inverter (battery is discharged at 8.4V but inverter will shut down at 9.5V usually) you will need to a small boost converter after the switch, and that also means that the low voltage protection is completly disabled (you would need to at the very least add one which is simple).
 
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You may want to solder the wiper to one end of the pot so that if the wiper fails to make contact (and believe me they do) it defaults to the resistance of the track instead of failing open circuit. This way you have it can either result in the inverter to stop working (thinks the voltage is too low) or the low voltage protection is completely disabled.

Besides that, good job, how did you figure out it was that resistor? I'm currently stuck finding a 24V 2000W inverter for a 6s pack (needs to shut down at 18V instead of 19.5 that most do).

Another simplier approach would changing the voltage after the power switch, so far what I've seen is that the power switch in a inverter interrupts just the supply voltage to the control circuitry (that is voltage at the switch leads = battery voltage), that means for example if you want to use a 4s pack (charge to 16.8V max) in a 12V inverter (usually shuts down at 15V) by putting two diodes in series with the switch you would bring down the voltage at the control circuitry by 1.4V so it will shut down at 16.4V instead of 15V. Add more diodes if you want to increase it (wouldn't go above 17V) it also has the plus of increasing the low voltage disconnect.

Now to increase the low voltage disconnect for example using a 3S pack in a 12V inverter (battery is discharged at 8.4V but inverter will shut down at 9.5V usually) you will need to a small boost converter after the switch, and that also means that the low voltage protection is completly disabled (you would need to at the very least add one which is simple).
Removing the resistance on this particular circuit will not cause a problem since the cutoff won't go below 30v and all my battery packs are safe to 28v. Most inverters use this same chip to compare against a 5v reference.
 
Removing the resistance on this particular circuit will not cause a problem since the cutoff won't go below 30v and all my battery packs are safe to 28v. Most inverters use this same chip to compare against a 5v reference.
You're saying that if the resistor and the potentiometer were not present (wiper fails to make contact) the inverter will still work? Alright then, it just means that the low voltage protection would be disabled, not much a problem if you have a bms or another protection circuit before.
 
You're saying that if the resistor and the potentiometer were not present (wiper fails to make contact) the inverter will still work? Alright then, it just means that the low voltage protection would be disabled, not much a problem if you have a bms or another protection circuit before.
No, the cutoff will continue working at about 2.5v less than the factory setting.
 
Just catching up. One question.

HOW DID YOU FIGURE OUT WHICH RESISTOR WAS USED IN THE LOW VOLTAGE DETECTION CIRCUIT ! I would have lost the rest of what little hair I had left and been in the looney bin trying to reverse engineer that !
 
Just catching up. One question.

HOW DID YOU FIGURE OUT WHICH RESISTOR WAS USED IN THE LOW VOLTAGE DETECTION CIRCUIT ! I would have lost the rest of what little hair I had left and been in the looney bin trying to reverse engineer that !
Look up the number on the chip, get a schematic and trace the leg comparing reference voltage. You can also contact any chinese manufacturer and request the information from their engineer. Just tell them it's off and you want to correct it yourself.
 
R11 is right next to an LM224 op-amp. It is probably part of a voltage divider along with R12 or maybe R14.

The other chip in the picture is a SG2525 is a regulating pulse width modulator. My guess is this controlling the low voltage to high voltage conversion.
 
I have the 5kW 48V version, can't believe I missed this post. This thing is actually very serviceable, and you get proper information from their engineers. They even (used to) have repair kits available, but they will help you out in any case if there are issues with components and replacement parts if you need them.
 
I have the 4000w version from the same company. When it is under a light load, it has trouble with voltage regulation and it can make lights flicker. Would anyone happen to know how to tweak the voltage regulation on this unit?
 
It is probably NOT the voltage regulation circuit. It is likely the output filter capacitor (kind of dark orange). Either one is going bad or they are undersized.
 

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It is probably NOT the voltage regulation circuit. It is likely the output filter capacitor (kind of dark orange). Either one is going bad or they are undersized.
So how would a bad filter capacitor allow proper operation under a big more load but basically pulse off and on under lighter loads (please explain)? The red light looks like a heartbeat until the load gets up above a few hundred watts. I am not sure of the exact load point but the problem is seen only on light loads.
 
Ah good question and it made me re-think my answer !

You are correct, if you are not getting ripple under a heavier load the capacitors are probably fine. That huge inductor and those two caps likely are part of a low pass "pi filter". The cut off for filter is not correct. What you need is a different TYPE of capacitor added in there. One that will work better at a different frequency.

Unfortunately I have been away from electronic design for too long (15+ years) to remember the specifics.
 
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