Battery Voltage after LVC kicks in?

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Fireblade

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Corally RC's
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I've got 2 6S packs and one seems to hit LVC sooner than the other, so I since I now own a multimeter which basically makes me a qualified sparky I thought I'd throw it across them both to compare.

One was at 22.4v (3.76v per cell) and the other was at 23.4v (3.9v per cell)

Neither was anywhere near the 3.1v that LVC is set at. Why?
 
You’re seeing combined or averaged voltage acrossed all cells most likely, however it is possible to check each cell’s voltage through the balance connector I believe.
My guess is voltage sag under load. How soon after hitting LVC did you check the pack voltage? They will come back up to “resting” voltage after some time has passed.
I’m guessing that not all cells within the pack are reading the exact same voltage after hitting LVC? There’s always some variance across the cell voltages within a pack. In general the closer the readings from each are to one another the better “matched” the cells are. Separates the good battery packs from the cheap in general. Cheaper packs aren’t as well matched across the cells as higher quality “matched cell” packs.
Typically as a battery ages and has more cycles on it one or more of the cells start to build internal resistance (ir), once a pack has a cell (or more) with higher ir, it will eventually trigger a “false” or premature LVC response from the esc circuitry.
 
Cheers for the explanation, I for the first time used the ir function on my charger

Black battery - 3,4,5,5,4,4
Blue Battery - 5,4,4,4,48,4

Voltages on both packs are within .02 volts

The strange thing is, it is the Blue pack that seems to last the longest.
 
Partydaz said:
Them IR are alright I have packs that hit 8-10 Mohms still working sound :D
Click to expand...
Same here. I know they’re getting bad when the pack starts getting hot during use. Well, batteries that didn’t get hot when healthy that is.
 
I use them up until they start to swell when I see IR of 15Mohm + I think well the cell volts are fine this puffing has been here for a while be alright 😅
Live Dangerously Austin Powers GIF


All the lipos I have put in the lipo grave yard out back have all had a weak cell so need get gone. Only had one that puffed to scary levels and that was a 4s 6700mah traxxas lipo thing would roll around the bench it swelled up that much.
 
Fireblade said:
Cheers for the explanation, I for the first time used the ir function on my charger

Black battery - 3,4,5,5,4,4
Blue Battery - 5,4,4,4,48,4

Voltages on both packs are within .02 volts

The strange thing is, it is the Blue pack that seems to last the longest.
Click to expand...
48 mohm is an issue.

The battery will sag during high current use and then recover. You do not want the sag to go too low at any point as the battery will be damaged. Sagging too low causes the battery to get warm, this is your first indicator. Higher internal resistance cells sag more than low IR cells. This is another indicator.

The sag point is often debated. I would never allow a battery to sag below 3.1v for any cell. My batteries typically have 3.6-3.7 resting volts per cell after use. As they age and IR picks up, the resting voltage after use increases because they sag to my 3.1v cutoff earlier.

SMC has a nice tech writeup if you want more detailed information.
 
This is off subject but with your LVC set at 3.1v your batteries won't be lasting long. Under 3.4v the cells start to draw unevenly. Eventually cell 1 will die. I went through a lot of batteries before I figured this out.
 
I think for bashers it's important to set the low voltage cut off no lower than 3.3v/cell.

Lower than this will result in a damaged battery. Worst case scenario is thermal run away and fire inside your rig! 😱

For racing, I don't set a LVC at all - because sessions are 5 minutes and my 2S batteries never drop below 50% - even when running 4.5T motors.

As a rule of thumb, try and keep your batteries no less than 10% at the point when you put them back on charge. Get used to how your rigs drive at 10% battery. Develop your memory muscle.

Store them at 25%.

Charge them on the day of use. Don't leave them fully charged for days on end - this will kill your batteries just as much.

Don't leave them get too hot. Hand warm - okay. Hand hot - not okay.

Cold weather running - sags the pack much more easily, which in turn can chemically degrade your cells. Avoid doing this repeatedly.

HV Lipos at sanctioned racing events are not allowed to be charged to anything higher than 4.2v/cell.

So on a 6S pack - consider whether you really need to max out the charge. Is 25.1v enough? If it is - stick with it and don't needlessly go above it.

Likewise - 4S - 16.8v.

Ever noticed how that last 1% takes longer? You may not need to stress your batteries this way.

Charge rates. Stick to 1c. Yes - it takes longer to charge them, but your batteries will also last longer.

Battery life depends on all of the above factors. Sadly, we can't just cherry pick one factor whilst hoping the other things don't matter as much.

The better your battery management - the longer they're going to last.

38854.webp
 
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