LIPO Batteries
 

Hi guys,

Little experience with these, what do people charge at? and what do people set the cut off voltage to when charging and discharging?

Thanks

Nathan

Hi Nathan,

Generally you want to be charging between 1 & 2 C
E.g. If you have a 5600mah battery then charge at 5.6amps, 6200mah = 6.2amps and so on, charging at 2C is basically double that. charging at a higher amp doesn't make any difference to performance as voltage is limited anyway. But obviously will charge quicker and can reduce cell life.

Voltage limit in the UK is 8.4v

Generally discharging isn't needed, but regular balance charging will keep the cells in good condition.

Hope that helps you

Thanks luke, so i just set my charge cutt off voltage to 8.44v?

Say if its an old pack though and i wanted to cycle it what would i set my discharge cutt off voltage to?

Thanks

The voltage limit at most races in the US is 8.40v, and the ROAR races have a limit of 1C charge rate.

For discharging, don't go below 3.0v per cell, so 6.0v for a 2s pack, or you'll kill the pack. To be safe, I'd limit it to 3.2v per cell, or 6.4v.

That said, you really don't need to cycle the packs. Just leave the remaining charge in them after your race until the next race day. Then just charge and go.

From the next summer series the UK will also be 8.40V.

Nathan, make sure you are using a lipo compatible charger set in lipo mode, you shouldn't have to set any voltages.

It will ask how many cells the pack is (2s for a 7.4V pack) then let the charger sort out the voltages.

Lowest voltage is 3V per cell.

Skiddins

ROAR states 8.5volts in the US !

In the UK, where Nathan is, it's 8.4v please don't go higher

http://www.roarracing.com/downloads/..._Rule_Book.pdf

Not according to the published ROAR rule book. But thanks for playing. On page 39:

8.3.2.5.2 Li-Poly battery maximum charge voltage.
- 1s Li-Poly batteries may be charged to a maximum of 4.20v.
- 2s Li-Poly batteries may be charged to a maximum of 8.40v.
- 3s Li-Poly batteries may be charged to a maximum of 12.6v
- 4s Li-poly batteries may be charged to a maximum of 16.80v.
- 2S LiFe batteries may be charged to a maximum of 7.40v.
- There will be no allowances for overages.

I have continually pushed the max on both max resting voltage and max current (when charging like everyone else does cc/cv)


My max resting voltage is 4.3-4.33 and my max cc/cv rate is about 15C. Sorry I can't help with discharge cut-off because it depends on the reason for discharging. Both are personal preference.

I've also kept a small chart of termination or resting voltages , but it is very sparse and one cannot draw any conclusions from it yet. None of mine have damage , but these reports of overcharge are damage reports and range from 4.44,4.54,4.48,4.37. The only thing I can say for sure is that 4.5 volts is probably too high , but I've not done any "sacrificial testing". I should proabably do that since I have many cells that are worth about $1.

lipo battery
 

Hi all after some advice went to charge my 14.8v lipo and the charger said low voltage does this mean it's dead or is there anything i can do to charge it again?

There are some chargers (e.g. Revolectrix Powerlabs) that have a specific mode to restore low voltage lipo packs.
Also if you can measure the individual cell voltages, then it may be possible to get it back to life.
Otherwise it would be very risky.

charge 3C
cutoff 3,2v

use the nimh mode

Put the battery in a lipo bag or fire box. Set the charger to NIMH mode and charge for about a minute and then retry it in lipo mode. I have brought a few packs back this way. I have them marked and will only run them in practice or heats. I will not run them in the mains. I have noticed that they don't have the same punch as a battery that was not run low.

some of this info doesn't seem right after spending the last few days reading and watching videos about lipo's.

you guys are saying to just slam a large charge into a battery and call it good. that's the 1. thing they say not to do with a lipo. they all have a different charge rates that you're supposed to follow.
they're not all the same basically.

http://2bfly.com/knowledgebase/batte...dos-and-donts/

this is a calculator you can use to determine the proper rate to charge your lipos.

http://2bfly.com/tools/

Uh, I dont see anybody saying to throw 20A into any lipo.....most lipo's should have a charge spec on them and most newer ones support a charge rating of 5C or more.
So a 2C or 3C charge (2-3 times the rated capacity) is not uncommon and shouldn't affect the battery in a negative way.