Discharge Lipos before charging?
 

Hello,

Finally I bought some Lipos in oder to start RC racing again. I thought that these batteries can be charged days before use and also can be re-charged after runnning without having to care for the remaining capacity :woot: . Now I read on a touring car forum that folks discharge their Lipos to 6V before charging them with even more than 1C. This charging method shall offer more punch and therefore more speed. Have you ever heard of something like this? I feel like things are going back to NIMH age :thumbdown:. Perhaps I better stick to my crawlers...

Cheers, Norbert

Discharge to 3v per cell!?? I wouldnt have said thats a good idea, ideally you dont want a lipo cell to drop below 3.3v per cell, 3v at absolute max!
regarding c charge rate, importantly make sure you check what the charge rate is for your lipo,, if its 1c dont be tempted to up the charge rate, also from what I've read if you want longevity from your lipo dont charge at more than 1c anyway.
If you are storing your lipo for say 3 weeks or more its a good idea to charge/discharge them to around 3.8v per cell

Lipo's have no "memory" so don't need discharging and re-charging before use like nimh did. They also don't self discharge like nimh did, so between use they don't need looking after to the same extent - my one and only pack has been sat in my garage for nearly 2 months without use so after a I month made sure it was at around 80% charged (which it was) and left it.
Not sure if charging at more than 1c gives more punch or not, but they're more than fast enough as they are.
When I do eventually race again I'll just charge them (at 1c) to capacity for round one and then re-charge again between rounds.
It really is that simple! (some touring car drivers like to make these things seem more complicated than they need to be)

They are wrong. Never charge you lipos more than 1c and you never need to discharge them.

Lipos can run below 3.v per cell but it's best to set the cut-off as 3.2 to be safe. If I remember right I think the electrical specs when manufacturing devices is 2.6v a cell as minimum (that was for mobile phones which wouldn't draw as much as motor.

Nosram state in their instruction booklet for their 5000 50C X-treme race lipos that the maximum charge rate is 15amps (3C) but the recommended charge rate is 10amps. (2C)

Surely its fine if they are recommending it?

Are you mental it'll be like a nuclear holocaust!! I think 5 amps would be fine.

Regarding discharging, you don't need to bother. I run the car then straight away recharge them for the next round. I don't even take them out of the car.

not true if the manufactures stae it that can take it safley traktech say up to 5c on thier 5000 packs!
the BRCA advice 1c and the only benifit from faster charge rates is quicker charger, it reduces the life of you lipo as a down side.
no benifit from cyling and you should not repeak lipo!
your claim of 5 amps is enough is true!

You can charge at higher C rates but it's not recommended by the BRCA to my knowledge and all it does is shorten your battery life.

+1. The only thing that seems to be agreed by everyone is not to store them at full charge, but to use the popular chargers' discharge programmes to drop them down to nominal voltage (3.7/7.4/etc) if storing for more than a couple of weeks.

I've tried it all, and can tell you that charging above 1C, re-peaking and discharge-before-charge makes no difference at all except to cane the cells harder than you need to. On the track, the clock can't show me any difference.

Stick to 1C charge rates, storing them discharged from the last race if using them weekly/fortnightly, and no re-peaking. HTH :)

Lipos are able to run below 3v per cell then?? Thats not what I've read time & time again

Thanks for the advice mates. I will stick to the manufacturers instructions than. This topic became quite popular in German forums because of the results of the HPI challenge finals a few days ago. Some guys complained because others were faster than them although running the same motor, battery etc. The faster guys answered that it is all just a matter of Lipo charging as I described in my first post. :thumbdown:

You're very welcome. That comment on the HPI Challenge makes me laugh - we had exactly the same ten years ago when we used NiCad cells!!

I wonder if, having taken them right down, and then blasted them on the way up, the LiPo has got warm? If so, then that would explain the punch and volts they get. A warm LiPo will give you more punch for the first few laps, and technically will give you a 'higher' voltage after charge. That's why there is a Rule in lots of countries that LiPo must be at ambient temperature when going on to race - not sure about BRCA Rules. Just a thought...

i fear they may have been over charging:thumbdown:

I have found that if i pre charge my lipos before race day they have less punch then if they are charged on the day.