diy solar

diy solar

WZRELB Reliable Inverters Low Voltage Cutoff Mod How To

H

heavy-impact

New Member
Joined
Apr 28, 2020
Messages
71
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
 
Htfan said:
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
Click to expand...
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.
 
heavy-impact said:
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.
Click to expand...
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).
 
Last edited:
Samueru said:
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).
Click to expand...
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.
 
heavy-impact said:
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.
Click to expand...
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.
 
Samueru said:
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.
Click to expand...
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 !
 
theoldwizard1 said:
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 !
Click to expand...
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.
 

Attachments

  • Capture.jpg
    Capture.jpg
    72.6 KB · Views: 20
theoldwizard1 said:
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.
Click to expand...
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.
 
I don't see this problem at low loads on mine. I would suggest to contact the manufacturer. It might be that it goes into standby mode too quick because it thinks there is no load. Their engineers actually seem to care and should be able to help out.
 
upnorthandpersonal said:
I don't see this problem at low loads on mine. I would suggest to contact the manufacturer. It might be that it goes into standby mode too quick because it thinks there is no load. Their engineers actually seem to care and should be able to help out.
Click to expand...
I noticed the light blinking when I first bought it. Months later now, I have it connected to a transfer switch and when I tested yesterday this issue is causing the lights to flicker. I can video the output end of the panel and I bet they will know exactly what is wrong. I had pretty much decided that would be my next move. Thanks for the input.
 
DThames said:
I noticed the light blinking when I first bought it. Months later now, I have it connected to a transfer switch and when I tested yesterday this issue is causing the lights to flicker. I can video the output end of the panel and I bet they will know exactly what is wrong. I had pretty much decided that would be my next move. Thanks for the input.
Click to expand...

You may have done this but step 1 is to double check ALL connections in the system.

Also be certain you are delivering adequate DC current and voltage.

Just a couple thoughts.
 
No Load (video)
10watt LED (video)
60watt load (video)

At some larger load point (have not taken the time to zero in on the value) the problem goes away.

Just by the looks of it, it would be something like some voltage (internally) gets too high and some circuit control cuts output until the voltage is back down, then the voltage builds again, and the cycle repeats. Under enough load the offending circuit point is loaded enough that the voltage can't out of the limit, so the problem is not then seen.

Connections and available power are good. Inverter fed directly from battery terminals (2 in parallel with separate cables), no BMS, no possible weak point between battery and inverter.
 
Last edited:
Having a fixed LBCO can be a problem. One thing common to many setups is too much resistance voltage drop in the battery lines, primarily due to too small gauge cable for current used during peak load.

You would like to have the inverter hit LBCO before BMS low cell shutoff but with too much cabling voltage drop on heavy loads you have a hard time setting inverter LBCO high enough and not have inverter spurious shut downs on heavy load. Some inverters have an adjustable LBCO timer that helps for surge loads by requiring the LBCO voltage to stay below trip voltage for some set time. A real low battery condition is slow and sustained, a surge load induced voltage drop on inverter can be ignored with a LBCO timer to ride over the short time period of inverter input voltage sag.

Nothing to do with LBCO, but many of the low cost Chinese inverters have trouble with PWM output AC filter. Biggest issue is the toroid cores are not physically large enough to handle high 50Hz or 60 Hz AC current without saturating the core. The low freq AC is like a heavy DC bias on the core forcing it near magnetic saturation where the inductance drops to low level. When this happens there is no longer sufficient high frequency PWM filtering. They skimp on inductance to avoid severe core saturation for the smaller core but this creates a lower reactive load during light loading on inverter raising DC idle current draw.
 
Last edited:
RCinFLA said:
Nothing to do with LBCO, but many of the low cost Chinese inverters have trouble with PWM output AC filter. Biggest issue is the toroid cores are not physically large enough to handle high 50Hz or 60 Hz AC current without saturating the core.
Click to expand...
Most low cost Chinese inverter use a "high frequency" front end. The incoming DC is pulsed and sent to multiple EI core transformers. The output of these transformers is rectified using Schottky diode resulting in high voltage DC. This is converted input a high voltage AC output typically using an EGS002 daughter board (based on a EG8010), some MOSFET drivers (IR2110 or similar) and then a number of power MOSFETs. The typical putput filter is just an L and a C.

More "expensive" designs use low voltage, high current to drive a large toroidal transformer.

Some of the Chinese companies are now using PIC based controllers instead of the the EG8010. Similar functionality but there is much more flexibility in feedback and output to drive user interfaces.
 
Here is an update. The MFG replied to my support request. "The problem happens most often when the battery voltage is high and the load is light". It appears the inverter is shutting off and on several times per second because the high voltage DC is too high. I was asked to drop the battery voltage to 24.0v and test. Everything was fine at 24.0v. At 24.3, you could see a flicker in a 60w incandescent lamp. I am using LiFePo4 batteries so 24.0v is a bit of a joke. I have not heard back from them if there is an option to adjust it or not.

Another note, at 26v when the load gets to about 1400 watts the flickering in the lights stops.
 
upnorthandpersonal said:
Interesting. Mine is a 48V version - I got to go try and replicate what you see.
Click to expand...
With the inverter on and no load, the red light on the inverter is pulsing like a heartbeat. Lighting loads, the lights pulse in sync with the red light. More load, the light goes faster until you can't see it any longer. But you can see the lights pulsing.
 
I just quickly tested. My battery sits at 53V. I both connected a single small load and also ran no-load. I don't have the red LED come on at all, and everything works fine.
 
heavy-impact said:
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.

View attachment 24832View attachment 24833View attachment 24834
Click to expand...
Didn't work on my 2000 watts, my voltage regulation board is different than yours or I'm on the wrong board! My R11 resistor was 10k (1002).
20210307_203134.jpg
 
Hello all. I’m new here but I’m hoping someone can help me out.

So I did this mod with the intent of turning the voltage cutoff to the mid 9’s (I have a 12v 1000w 120v) but alas - this is unfortunately when I realized my soldering skills aren’t nearly what they used to be in my older age.

I damaged the pad of the resistor and then when tried to repair it damaged a trace and probably the LM224 ic along with it. It actually DID work perfectly. Once. Then nothing so I am assuming the voltage control board is damaged beyond repair.

Problem is - apart from waiting for the manufacturer to get back to me then slowly ship me one from China (which could take months) I can not find this exact board anywhere at all. And believe me I’ve looked. Everywhere

Can anyone tell me where I can get a replacement board or compatible one?? The ones I’ve found don’t have the on off switch input nor the horn (not that I need that). Only thing written on the board other than the ic part numbers is “LBQJ - v4.2”

I have the same one pictured in the original post. Can anyone please help??? Thanks I’m advance.
 

Attachments

  • 033C7E04-112E-4503-9443-6FB49C1807FB.jpeg
    033C7E04-112E-4503-9443-6FB49C1807FB.jpeg
    121 KB · Views: 24
Last edited:
jdilly said:
I damaged the pad of the resistor and then when tried to repair it damaged a trace and probably the LM224 ic along with it.
Click to expand...

Unless you overheated the LM224 it should be fine. Fixing the trace with some wire should be worth a try. Even if that LM is broken, it's a €0.42 part or so, so you could replace that too.

If you're in Europe somewhere I could give a go at fixing it.

I don't know of any other source besides the manufacturer.
 
I did indeed overheat and damage the LM224 when I tried to repair it. Unfortunately I hadn’t realized how much the disease I have has progressed until I tried to do some precise soldering and couldn’t stop my hands from shaking. It just started getting worse the more I tried because I got frustrated. I should have walked away for the night.

Also unfortunately I’m in the United States but I do appreciate the offer.

If all else fails I’m sure the MFG can send me a new board - and worst worst case scenario I will try to get a new LM224 and be more careful repairing it. Was just hoping someone would know where to get one besides the MFG, or if there was a compatible one.
 
You can purchase a new LM224 op amp if need be and bypass the bad section of trace by soldering a piece of wire from one solder point to the next. If your hands aren't steady enough take all the parts to an electronics repair shop or TV repair shop and point out what you want soldered.
Good luck.
 
heavy-impact said:
No, the cutoff will continue working at about 2.5v less than the factory setting.
Click to expand...
I just removed the r11 resistor based on this thread. After removal, the inverter stopped working - when i turn it on it just runs the alarm directly. Perhaps i should connect the 2 Solder lugs left after the resistor? Or what am i getting wrong?
 
DThames said:
Here is an update. The MFG replied to my support request. "The problem happens most often when the battery voltage is high and the load is light". It appears the inverter is shutting off and on several times per second because the high voltage DC is too high. I was asked to drop the battery voltage to 24.0v and test. Everything was fine at 24.0v. At 24.3, you could see a flicker in a 60w incandescent lamp. I am using LiFePo4 batteries so 24.0v is a bit of a joke. I have not heard back from them if there is an option to adjust it or not.

Another note, at 26v when the load gets to about 1400 watts the flickering in the lights stops.
Click to expand...
Can't believe they told you this. A real poor inverter design. They appearently have an voltage overshoot ringing problem on the DC-HV DC converter first stage that is tripping its momentary shutdown. Then it takes some time to recover causing a momentary slump in DC high voltage to run the output PWM sinewave chopper. Great for surge current on input DC-HV DC converter MOSFET's putting extra stress on them.
 
Last edited:
DThames said:
I noticed the light blinking when I first bought it. Months later now, I have it connected to a transfer switch and when I tested yesterday this issue is causing the lights to flicker. I can video the output end of the panel and I bet they will know exactly what is wrong. I had pretty much decided that would be my next move. Thanks for the input.
Click to expand...
Low cost high frequency hybrid inverters will do this because their DC to HV DC converter first stage has to make a power flow mode change if it is in charging battery. When charging, and it detects an input AC loss it will reverse its DC-HV DC converter direction to supply inverter output power from batteries. This takes a little bit of time which will cause the glitch when transfer switch flips.

Once the transfer switch completes and AC input is applied again it must synchronize to new AC source, which can take a few of seconds, and go back through the DC-HV DC converter reversal process again before returning to battery charging. This means there will a few seconds of interruption in charging. This may also cause a second glitch in output AC depending on how much AC output load is when DC-HV DC converter makes its flow direction change again .

LF hybrid inverters can make the battery power flow direction change instantly.
 
Hello i will try to write more about my problem with this type of inverter. Maybe Somebody can help...

So i have the 1000w version in my camper And the problem is that lately when my 230v fridge starts running the commpressor sometimes there Is a slight voltage drop And the inverter starts beeping or even cutoffs the voltage even when the batteries Are almost full.

I found this thread based on which i would like to make the cutoff voltage as low as possible or even turn off this function completely. I have lifepo batteries with bms So i really dont need IT anyway.

So i Went ahead And desoldered the r11 resistor. After that when i Turned one the inverter IT just gives me a continous beep and never starts running. Maybe the problem is i did not add the trimmer and therefor left the Circuit open. Perhaps if i just take a piece of wire and make a connection between the two Solder lugs where the r11 resistor was to close the Circuit, Will IT fix my problem? Or can i just unplug the White wire connected to the voltage cutoff board to completely bypass it? Thanks for any input.

Since i live in the camper And really need the inverter working i dont want to make a Mistake And have no power but having IT beep every night Is also super annoying!
 
FredyPND said:
I found this thread based on which i would like to make the cutoff voltage as low as possible or even turn off this function completely. I have lifepo batteries with bms So i really dont need IT anyway.
Click to expand...
You really do not want BMS to disconnect battery as the primary low voltage detection. There are several potential issues doing this, relating to surge currents on restart. If you have a battery monitor for AH tracking you may also lose the cumulative AH info.

If you have an adjustable inverter low battery cuttoff, and you are unable to get an acceptable low battery inverter shutdown, it is usually caused by too much battery cable voltage drop on peak current demand (too small battery line wire gauge) or insuffcient battery size to support peak current demand.

With LFP batteries with a low cost BMS, the BMS MOSFET series switch resistance also comes into play during peak surge current voltage slump. Their switch resistance relates to their max current rating. Many of the low cost BMS current ratings are based on their peak current capability before they self destruct and should not be used with a continuous current greater than about half their specified current rating. They have an overtemp shutdown but that does nothing for surge current voltage drop across the BMS.

If inverter has a low battery voltage trip delay timer adjustment setting, it can be used to ignore momentary peak current DC input voltage slump.

If you allow batteries to get significantly out of balance it can impact on how low battery detect reacts. You will get significantly less capacity for battery array so original battery monitor AH capacity setting will likely be far off. When cells get to less then 20% state of charge their voltage slump under heavy load current will be greater, particularly if current peak last longer then 20-30 seconds.
 
Last edited:
You must log in or register to reply here.

Similar threads

M
Low voltage cutoff?
Replies
1
Views
264
sunshine_eggo
sunshine_eggo
K
low voltage cutoff to heat batteries only when charging
Replies
1
Views
265
timselectric
T
B
load control for low temp and low V??
Replies
0
Views
199
bkfamily1
B
S
Using a Victron Smart Battery Protect as a low temp cutoff for chargers.
Replies
1
Views
259
corn18
corn18
Bluedog225
Quattro update and low voltage cutoff
Replies
16
Views
385
Bluedog225
Bluedog225
Back
Top