Low voltage cut-off on a LiPo and my ESC settings

[jameshopkins]

Hi there,

I’m new to RC’ing so please bear with me.

I’ve bought an HPI Maverick Quantum Flux with an HPI Plazma 11.1v battery and an HPI reactor 600 to charge it.

The first time I charged the battery it was from factory, and it was charged from around 50% using the balance cable too. I then set the ESC to a low-voltage cut-off of 3v - admittedly I should probably set it higher in future to allow for a greater tolerance.

After an hour of fun I put the battery into the charger and attached the balance leads. It’s worth noting that this was after the monster truck reduced temporarily reduced to what felt like 50% of its power, and then the throttle cut off completely, although the steering still worked, and the ESC was flashing a red light. Given the cut-off I configured, I was expecting a percentage reading bigger than I expected; it seemed to suggest that it was 3% for each of the 3 cells.

I triple checked the ESC settings the first time I configured it.

Does this mean I’ve ruined the battery, or am I jumping to conclusions?

Thanks for any help in advance

 

[WickedFog]

What is the voltage of the battery? If it is above 9v, you should be ok. If not, you're going to have to bring it back above 3v/cell in nimh mode more than likely. If it is overdischarged, the battery likely sustained some damage. I am not familiar with that charger, but looking at the specs, I wouldn't pay more than $10 for one, yet it lists for $65 It doesn't look like it displays any battery info. Did a hobby shop recommend that? If so, go back and drag the salesman outside and whoop his butt.

Get yourself a Hota D6 Pro.

As far as the LVC cutoff issue, until you figure it out, get yourself a LiPo alarm. Connect it and tie it down in the car to be safe.

 

[jameshopkins]

What is the voltage of the battery? If it is above 9v, you should be ok. If not, you're going to have to bring it back above 3v/cell in nimh mode more than likely. If it is overdischarged, the battery likely sustained some damage. I am not familiar with that charger, but looking at the specs, I wouldn't pay more than $10 for one, yet it lists for $65 It doesn't look like it displays any battery info. Did a hobby shop recommend that? If so, go back and drag the salesman outside and whoop his butt.

Get yourself a Hota D6 Pro.

As far as the LVC cutoff issue, until you figure it out, get yourself a LiPo alarm. Connect it and tie it down in the car to be safe.

Thanks so much for your reply. I’ve just this minute invested in a battery checker (https://www.amazon.com/dp/B07RNPHJN6/) so will check the health of it.

I’ve triple checked the LVC in the ESC manual to make sure I made the right selection. Very strange!

 

[WickedFog]

That LiPo checker is ok, but you can get the Cellmeter 8 for $3 more, and it is also a servo tester. So if it were me, I'd cancel that order and get the Cellmeter 8 instead.

But I would still get a LiPo alarm to use til you make sure your LVC is working correctly.

 

[Greywolf74]

If you stick it back on the charger and try to balance charge it, does it charge? If so then you should be ok. LiPo chargers generally wont charge a lipo if the voltage has go below a safe level. I would definitely invest in the HOTA D6Pro as WF suggested. It can read the internal resistance (IRs) of the cells and thats the best way to keep an eye on the "health" of your lipos.

 

[jameshopkins]

If you stick it back on the charger and try to balance charge it, does it charge? If so then you should be ok. LiPo chargers generally wont charge a lipo if the voltage has go below a safe level. I would definitely invest in the HOTA D6Pro as WF suggested. It can read the internal resistance (IRs) of the cells and thats the best way to keep an eye on the "health" of your lipos.

Yeah I managed to balance charge it to 100% no problem.

Although, weirdly I just took it out to an open space where I could floor it for the first time, and I had issue retaining maximum throttle after a period of a few seconds; speed would either drop to around 50% or there’d be no throttle at all. Then, after a second or two, it’d be fine again. Maybe the batteries on the receiver are on the blink

 

[tntpoof]

raise you low voltage on esc.id go to 3.6 volts next time you notice rc slowing down stop rc take a walk pick it up unplug battery. IR .it can show you some information but for a basher can be very deceptive. Try and get a better charger that show's you what batteries voltage is ..that 50 watt charger is a 1 outa 10 in my book.

 

[WickedFog]

You balance charged it to 100%, but I wonder if that charger didn't think it was a 1s or 2s or something and only charged it partially. Because that's whst it sounds like. Do you have a multi-meter? If so, you can check the cell voltages with one.

 

[jameshopkins]

You balance charged it to 100%, but I wonder if that charger didn't think it was a 1s or 2s or something and only charged it partially. Because that's whst it sounds like. Do you have a multi-meter? If so, you can check the cell voltages with one.

I get your drift, but when I’m charging it, it automatically detects the number it cells, and gives me a percentage measure of each cell’s charge.

 

[WickedFog]

I get your drift, but when I’m charging it, it automatically detects the number it cells, and gives me a percentage measure of each cell’s charge.

Well something's off if it only ran for a few seconds. I wouldn't run it anymore til you know for sure how the pack is.

 

[jameshopkins]

So I continued to run the truck from a balanced charge, and it started to randomly disable the throttle (although I steering was still active), but after a couple of seconds it'd run at around 50% throttle again. I could see a flashing red light on the ESC whilst this was happening.

When I checked the cell capacities, they were all 27% (3.7v) after previously setting an LVC of 3.4v. I assumed when the LVC was triggered, the car would be consistently disabled? Is this the correct assumption?

 

[Greywolf74]

So I continued to run the truck from a balanced charge, and it started to randomly disable the throttle (although I steering was still active), but after a couple of seconds it'd run at around 50% throttle again. I could see a flashing red light on the ESC whilst this was happening.

When I checked the cell capacities, they were all 27% (3.7v) after previously setting an LVC of 3.4v. I assumed when the LVC was triggered, the car would be consistently disabled? Is this the correct assumption?

Not necessarily. It depends on the ESC. The ESC could be programmed to respond in the manner you describe but it may not be. If its not programmed to stay disabled after being tripped then it could be resetting. In order to understand why that would be, you have to first understand that once a load is removed from a battery the voltage will "rebound" upwards a bit. If the ESC isnt programmed to stay cut off then it could be triggered thus removing the load from the battery allowing voltage to "rebound" back up a few tenths of a volt. When this happens the ESC now reads the voltage as being higher than the LVC and thus the ESC re-engages. Once the ESC re-engages then it reapplies a load on the battery which will almost immediately pull the voltage back down which will in turn trip the LVC again.

I hope that made sense

 

[jameshopkins]

Not necessarily. It depends on the ESC. The ESC could be programmed to respond in the manner you describe but it may not be. If its not programmed to stay disabled after being tripped then it could be resetting. In order to understand why that would be, you have to first understand that once a load is removed from a battery the voltage will "rebound" upwards a bit. If the ESC isnt programmed to stay cut off then it could be triggered thus removing the load from the battery allowing voltage to "rebound" back up a few tenths of a volt. When this happens the ESC now reads the voltage as being higher than the LVC and thus the ESC re-engages. Once the ESC re-engages then it reapplies a load on the battery which will almost immediately pull the voltage back down which will in turn trip the LVC again.

I hope that made sense

That makes a lot of sense; a very insightful comment, thanks very much! I’ll check the programmable options on the ESC. Thanks so much again for the informative reply!

 

[Greywolf74]

That makes a lot of sense; a very insightful comment, thanks very much! I’ll check the programmable options on the ESC. Thanks so much again for the informative reply!

Anytime.

As a side note, When I say its in the ESC programming I dont mean any setting you can go in and program, I mean the way in which the hard coded firmware is written.

 

[jameshopkins]

Anytime.

As a side note, When I say its in the ESC programming I dont mean any setting you can go in and program, I mean the way in which the hard coded firmware is written.

Ah ok gotcha. Spot the newbie!

The scenario you describe seems to tally with what I’m observing; that is that these symptoms get more frequent the longer I try to drive the truck after it happens the first time.

Unfortunately I don’t have a monitor to check the IR, but I’m going to assume everything is OK for the time being!

 

[Greywolf74]

Ah ok gotcha. Spot the newbie!

The scenario you describe seems to tally with what I’m observing; that is that these symptoms get more frequent the longer I try to drive the truck after it happens the first time.

This would track with what I'm saying because the more you deplete the battery the less it will rebound each time.

Unfortunately I don’t have a monitor to check the IR, but I’m going to assume everything is OK for the time being!

As long as the battery isnt puffing and your getting 10-15+ minutes of good run time right after a full balance charge then you should be fine. Once it hits LVC though Id just go ahead and stop running it until you can recharge the battery

 

[jameshopkins]

Ah ok gotcha. Spot the newbie!

The scenario you describe seems to tally with what I’m observing; that is that these symptoms get more frequent the longer I try to drive the truck after it happens the first time.

Unfortunately I don’t have a monitor to check the IR, but I’m going to assume everything is OK for the time being!

This would track with what I'm saying because the more you deplete the battery the less it will rebound each time.


As long as the battery isnt puffing and your getting 10-15+ minutes of good run time right after a full balance charge then you should be fine. Once it hits LVC though Id just go ahead and stop running it until you can recharge the battery

Yes that and also the voltage readings I was getting when it wasn’t under load of 3.7v per cell. The LVC is set to 3.4v so there’s potentially a 0.3v ‘rebound’