safe low voltage cut off

[BlazinKreeper]

I have a new ESC and was wondering what a safe low voltage cut off would be..also if it should be different for 2 or 3 cell packs?

[Chris_The_Battery_Man]

3v per cell is the rule of thumb

[spillproof]

Some might consider that low. 3.2 and 3.3 are pretty common. If a cell goes below 3.00 it could be hard to recover.

Another key thing to remember is that the ESC is basing its LVC on the aggregate voltage, as it is not aware of the actual per cell voltage. So, if you use 3.0v on a 3s, the LVC will kick in at 9v. But since it does not account for individual cell voltage, you could easily end up with one cell over depleted. I have done this myself. Over draining lipo's is one of the main causes of them failing. Its why there is LVC.

I recommend 3.3v generally. I also run a separate alarm that monitors each cell individually. It prevents the battery from becoming unbalanced and damaged.

ymmv

[CRAWLERJOE]

I run all mine at 3.2 v per cell just to be on the safe side

[Chris_The_Battery_Man]

Originally Posted by spillproof

Some might consider that low. 3.2 and 3.3 are pretty common. If a cell goes below 3.00 it could be hard to recover.

Another key thing to remember is that the ESC is basing its LVC on the aggregate voltage, as it is not aware of the actual per cell voltage. So, if you use 3.0v on a 3s, the LVC will kick in at 9v. But since it does not account for individual cell voltage, you could easily end up with one cell over depleted. I have done this myself. Over draining lipo's is one of the main causes of them failing. Its why there is LVC.

I recommend 3.3v generally. I also run a separate alarm that monitors each cell individually. It prevents the battery from becoming unbalanced and damaged.

ymmv

The 3.3v rule is really meant for high amp applications + low quality cells. They do this so that the voltage drop doesnt over run the LVC.

Lipos going under 3V isnt that deadly. I have to say (of the record) that I have had many go under when I am being stubborn and they are fine. Usually, that's monitoring on a loaded voltage. Once the pack is un-loaded, it will bump up. I have taken cells down to 2.5ish, and once they sit, they bump up to over 3v

The 3.2-3.3v is really kind of a catch22. If you have a poor quality lipo, the voltage sag while loaded will hit the 9.9-9.6V range easily, and cut off. I have seen it many many times. Now it doesnt really HURT anything to have a higher cutoff. But I do NOT recommend it


I have never run my LVC's set to anything higher than 3v, and have NEVER had an issue. I am also really hard on my stuff since I work in the industry, and can afford to say "EFF it, Jump it anyhow!"


3v is still even high. 2.75 was the old voltage WAY back in the day. Still is really, if the voltage detection on these chargers wasnt so bitchy.



So take it from a battery pro.... 3V per cell.... ALWAYS

[Olle P]

I've been thinking about this...

A few issues comes to mind:
- Temporary voltage drop as an effect of high load. This doesn't damage the battery and should ideally not trigger the cutoff.
- Voltage variations between cells. The cutoff should trig as soon as any one cell hits low voltage at low load.

Conclusions:
- Ideally the LVC should monitor through the balance plug(s) to sense each cell individually.
- LVC shouldn't be instant response, but trig on the average (or even maximum) voltage over some time (5+ seconds). So once the voltage for a cell stays below 2.8V for more than 5s then the LVC is triggered.

Unfortunately it seems like the LVCs in use don't work ideally, and therefore a higher trig level with lots of "false positives" has to be used.

[Charlie-III]

I use a value of 3.2VPC to be safe. Thus 6.4VDC for a 2S, 9.6VDC for a 3S.

Why?

I have to BUY my packs.

It also allows for a cell that dips rather low.

I will agree that a low MAH pack coupled with a low "C" can drop the pack voltage under load (usually in BL applications or "go-fasts").

I only run packs from CBP (sorry CtBM......sorta) and use these values to save my investment in packs. I only get decent packs from CBP. Elite packs for ~800mah+ and ThunderPower packs for smaller mah.
I may try the "Nano-Tec's" for small packs for my XR-10. I have "guidance" from TurboFest (a local club member) to try these out.

My current employment is battery related, but for VRLA (Valve Regulated Lead Acid.....UPS industry) so I understand some of the other issues related to batteries in general.

PS, CtBM.......you still want me ordering batteries from/supporting CBP?????

[cbr6fs]

Problem with going too low voltage wise is that on 2S and upwards cheaper packs tend to start to go out of balance.

On my nano-tech cells i am able to drop to 3v and the pack still stays balanced.
With my SMC packs if i go anything below 3.2v then the cells start going out of balance.

Problem is on poor quality packs the cells are not very well matched, so once you start dropping below say 3.2v the discharge rate between the 2 cells tends to differ more dramatically than above 3.2v.

In reality though the difference run time wise between 3v and 3.2v is seconds, so it's really not worth the hassle IMO.

[indiana mudcat]

I have to bump NiMh if my cells go below 3.2 per cell (Oynx 230) so I run 3.3 to give a little. All my batteries are Thunder Power 45 or 65c and I never have early or false cutoffs, low C packs and a brushless setup was a different story.

[RootBreaker]

im a 3.4v kinda guy.. so 10.2v cutoff.. which was funny cuz after i set it couldnt figure out why my truck wouldnt drive.. but had steering.. NiMh are 7.2.. DOH!!!!!!!! so then i put the lipos and and FLEW!!!!!!

[TrickyRicky]

I run 3.2v because I run cheap packs. Hard to keep balanced if I go to 3.0v.

[RootBreaker]

Originally Posted by TrickyRicky

I run 3.2v because I run cheap packs. Hard to keep balanced if I go to 3.0v.

yeah i got 500mah 3s turnigy for $5 each.. got 3 of them
cheap is for me!!!

[alexchen86]

I run my cut off at 3.4 on all my rigs (scale/comp/go-fast) I only run 3s and 4s. I run all types of packs from Gens Ace, Sky Lipo, CBP Elite, Thunder Power, Max Amps, Venom, and Turnigy Nano Techs. I usually try to find 30C and up packs.

At my original 3.0V/cell occasionally even my 40C packs on my ebuggy (MMM/2200kv/7955TG) will have one cell go wacky on me below 3.0V. I would have to bump charge in NiMH mode to get that one cell back up to the 3.0V range to properly balance charge.

After I set it at 3.4V/cell I've never had that problem anymore. I also did not notice THAT much of a run time difference. Plus usually by then your rig starts dipping in power anyway so you know LVC is about to kick in!