Do I have a defective lipo?

[DrGoatboy 132]

Just took a couple of cars out for a run with my kids. My WW2 running a standard silver can and a 3500 NiMH was still going strong after 40 mins and still has runtime left in it. My comical avante running 13.5t brushless sensored and a 4000 lipo lasted for less than 15mins.

Now I know the 4wd will sap a bit more power, and obviously the 13.5t will too (although to be honest it wasn't that much faster after a minute or 2 anyway) but I would expect the brushless to help a little in run times.

I wonder if the lipo isn't great? Is there anything I can do to check? I've only used a handful of times. No sign of swelling. Always stored at correct storage charge. They were out of stock for ages before I got one so it wasn't sitting in the shop for years before I purchased it ....

Mayor. Offer advice?

[rwordenjr 1890]

Do you have a lipo alarm ? An esc with low voltage cutoff ? When you say it lasted less than 15 minutes, the car just stopped ? 

[DrGoatboy 132]

5 hours ago, rwordenjr said:

Do you have a lipo alarm ? An esc with low voltage cutoff ? When you say it lasted less than 15 minutes, the car just stopped ? 

Thanks for replying. ESC is running a low voltage cutoff. It seemed to slow a bit over time which I wouldn't expect, then went into LV protection mode (half speed) for 30 seconds or so, then stopped. I wondered if it had overheated so let it cool but it only ran again for a few seconds before LV cutoff again.

[Snappy1 966]

Charge, drain and repeat ,

 

[DrGoatboy 132]

Ok, will cycle it a few more times. 

[rwordenjr 1890]

5 hours ago, DrGoatboy said:

Thanks for replying. ESC is running a low voltage cutoff. It seemed to slow a bit over time which I wouldn't expect, then went into LV protection mode (half speed) for 30 seconds or so, then stopped. I wondered if it had overheated so let it cool but it only ran again for a few seconds before LV cutoff again.

Your lipo is probably pulsating and dropping below the low voltage cutoff level triggering the esc to shut it down. I would get yourself a low voltage alarm and disable low voltage cutoff on esc. Run the lipo down to 3.4v per cell. I bet if you tested your volts after 15 min, it would be around 3.8v but it’s dropping below that for a spilt second when you’re on full throttle and that causes esc to shut it down. It’s either that or your esc has a high low voltage cutoff level. What esc do you have ?

[Nick G 54]

Are you always balance charging your lipo ?

[DrGoatboy 132]

Yep always balanced charged. 

[wolfdogstinkus 1893]

I found even the lipo alarm would beep sometimes under heavy load or full throttle. As @rwordenjr says, it probably just drops below 3.2volts for a second. 

Maybe time for a higher capacity lipo with a greater discharge rating?. Unless you are using a quality lipo already?

[rwordenjr 1890]

Just now, wolfdogstinkus said:

I found even the lipo alarm would beep sometimes under heavy load or full throttle. As @rwordenjr says, it probably just drops below 3.2volts for a second. 

Maybe time for a higher capacity lipo with a greater discharge rating?. Unless you are using a quality lipo already?

Yes it does. After a while, you can calculate just how long you can run before down to 3.2v-3.4v with no alarm needed. 

[DrGoatboy 132]

I don't know about quality but it's a core RC stick pack like this.

https://www.modelsport.co.uk/index.php?product_id=388538&gclid=Cj0KCQiAy579BRCPARIsAB6QoIarGVgMITTrZ64pBQF5X6J2PClZUagx2lZE_jku96wA228s7f6ncPMaAv3hEALw_wcB

Thanks for all the tips. I will check all the settings on my ESC which is a quicrun 10bl60 so I guess low end but not bargain basement. 

[DrGoatboy 132]

ESC LV cutoff is set to 3v same as default for my ESC 

[rwordenjr 1890]

20 minutes ago, DrGoatboy said:

ESC LV cutoff is set to 3v same as default for my ESC 

Do you have a voltage tester ? And what charger you using ? 

[DrGoatboy 132]

Mystery solved. Think I have lead us all on a wild goose chase. Sorry. Thanks everyone for your help. It's been really useful to learn some more. Disappointed this has died so quickly. Only run this battery maybe 10 times. Luck of the draw I guess.

 

 

[DrGoatboy 132]

Interestingly my charge won't now let me discharge the battery as the voltage is too low. That's weird?

[wolfdogstinkus 1893]

If the cells are unbalanced and one is below 3volts, you can rescue it by charging without the balance lead for about 30seconds which will get the low cell high enough for the computer to play with it from there..

Then you can run a few cycles and see what happens.

[DrGoatboy 132]

1 cell is below 2 volts! Plus it's gone a bit puffy when I looked a bit closer. Basically it's fubar. Would still be good to get it fully flat though.

[Snappy1 966]

You will need to get the low cell up before you can discharge the high cell though

When this has happened to me I just charged the Lipo on nimh setting for just a few minutes, it will bring the low cell up, then you can recharge the battery on Lipo setting, then discharge to say 3.3v per cell and cycle , you will know soon enough if it’s dead

 

[Wooders28 4723]

How have you managed to get it down to 5.09v? 

The ESC should only let it drop to 6v min for Lipo, although that esc will allow - no cut off, 2.6v ,2.8v , 3v (stock setting), 3.2v and 3.4v. I run my 10bl120 at 3.2v now, as I've a cell on its way out, and dropped to 2.8v with the other cell at 3.2v. 

Might be worth investing in a programmer, as sometimes the beeps can get confusing (if i remember right, 4 beeps is option 4, 1 long beep is 5, short beep + long beep #6 etc ?) 

 

 

[DrGoatboy 132]

1 cell is at 1.9v and 1 is at 3.1v. I assume the 1.9v cell is dead. I have never been convinced the pack was very good.

I don't have a programming card but pretty sure I have the beeps right.

[wolfdogstinkus 1893]

Is your charger refusing to charge it?

Unplug the balance lead and run the charge for a minute, this will bump up the low cell to a chargeable state..

Stop charge cycle, plug in balance lead, charge normally, it should change normally, then you can cycle it a few times to see if you can rescue it.

[DrGoatboy 132]

Thanks guys. I managed to get the bad cell up high enough for the charger to not alarm out by giving it a 30sec blast on NiMH setting.

Alas it's too late....

 

[Wooders28 4723]

On 11/9/2020 at 7:50 AM, DrGoatboy said:

1 cell is at 1.9v and 1 is at 3.1v. I assume the 1.9v cell is dead. I have never been convinced the pack was very good.

That's not good! 

Is it your only Lipo?

I'd be looking at the ESC settings and purchase a plug in alarm as a back up, they're only cheap, until you're 100% the low volt in the esc is set right.

I'd also check the settings on the charger, 4.2v finish voltage etc, as even if it was a lesser brand (Core RC is made by Schumacher, so it's not poor quality), balancing charging every charge and balance storage charging, you should have got more life out of it than that!! 

[DrGoatboy 132]

18 minutes ago, Wooders28 said:

That's not good! 

Is it your only Lipo?

I'd be looking at the ESC settings and purchase a plug in alarm as a back up, they're only cheap, until you're 100% the low volt in the esc is set right.

I'd also check the settings on the charger, 4.2v finish voltage etc, as even if it was a lesser brand (Core RC is made by Schumacher, so it's not poor quality), balancing charging every charge and balance storage charging, you should have got more life out of it than that!! 

It's my only 2s. My 3s (which I don't really use anymore) have been perfect on the same charger and same ESC.

[Wooders28 4723]

1 hour ago, DrGoatboy said:

It's my only 2s. My 3s (which I don't really use anymore) have been perfect on the same charger and same ESC.

I'd still check the charger settings, free to do and will only take a minute, on my chargers the 3s can have different finish voltages.

Seems strange the voltage dropped so low, the cut off should have kicked in a good volt before. The voltage difference is so great, that suggests a duff cell, might be worth contacting the supplier and see about a replacement, they can only say no..