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revolution9

Voltmeter Reading

Hello,

I'm about to fit a voltmeter to a Stryfe to monitor the level of a 2S Lipo and prolong it's life.

At what voltage level should I stop using the pack, and recharge?
I've done a search here and else where, but cant find a definitive answer.

I've seen 3V3 suggested

Please advise
OldNoob

You will very rarely go below 3.6v, even with multiple games all day, provided you properly specified the pack to suit your motors. Most voltage ALARMS are set to beep at 3.4-3.5v PER CELL. If you have a manual volt meter I would stop using the pack at 3.5v per cell or for your 2s pack 7v total.
I have never got below 7.2v total, even on triple XP or triple blades at a whole day game.
3.3v per cell is the ABSOLUTE cut off point. Below that risks damaging the cell permanently.
revolution9

Thanks for the advice
SSGT

Effectively it's whatever you're comfortable with. Unlike a lot of nickel chemistries, lithium chemistries don't like being deep cycled so, if you want them to last longer, it's better to simply top them up (either to full if you're playing again in the next day or so, or to storage charge if you aren't) rather than running them flat over multiple games and then charging them back up.

Somewhere around 3V is commonly regarded as "end of discharge" (i.e. effectively 100% flat) for the sort of packs we us (some lithium cells can supposedly go as low as 2.8V, or even 2.5V depending on the specific chemistry, but I really wouldn't be comfortable going that far with the packs we use) but you should really avoid even going that far if you can help it. 3.3V per cell is a reasonable absolute minimum to work to, but I know many don't like discharging their packs below 3.5V. Also bear in mind that the voltmeter gives the overall voltage of the pack not the individual cell voltage so adding an additional factor of safety allows for mismatched cell voltages due to uneven discharge as a pack ages. If the voltmeter reads 6.6V that could mean both cells are at 3.3V but it could also mean one is at 3.2V and the other is at 3.4V. For one of the cells to have dipped below 3V the other must be at least 3.6V - a 0.6V difference is quite large and so it should be safe to assume that if the voltmeter reads 6.6V neither cell will be below 3V if the pack that has been balanced charged and is in relatively good condition. If you worked to 6V, or even 6.2V, then even a relatively small difference in cell voltage could mean one cell has been over discharged. With higher cell counts this effect can be more pronounced (for a 3S pack a voltmeter reading 9.9V means one cell could be below 3V if the other two cells are at least 3.45V each - only a 0.45V difference). For this reason many recommend using a low voltage alarm that plugs into the balance leads and measures individual cell voltages. I often don't discharge packs much below nominal voltage over the course of a day so you may even find that after a day of games your pack is sitting almost bang on storage charge ready to be put away until next time.

In short 3.3V per cell is a good absolute minimum to work to, whereas 3.5V per cell is a good conservative minimum that will prolong pack life - that said, depending on the capacity/motors/how you play, you may find you never even get that low.

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