A Few Words of CAUTION!!!

[Shannon Davis]

Here is some info that was forwarded to me- source is Thunder Power.

Series Charging and Usage:

At Thunder Power we do understand many applications will require the use of multiple packs in series to achieve the desired level of performance. For example, some airplanes and helicopters will require the use of two 3s4p packs in series to fly as a single 6s4p pack. While it is possible to use multiple packs in series, Thunder Power /Advanced Energy Tech cannot be responsible for any problems encountered during series charging and or usage.

Again, you are on your own when charging or discharging packs in series – do so at your own risk.

Charging:

- Use only a charger designed for charging Lithium Polymer batteries
- You must use a high quality digital voltmeter (Capable of readings to 0.01v) to check voltage in order to correctly follow the steps outlined below. Your charger or Whattmeter are NOT accurate ways to measure pack voltage, and the use of a digital voltmeter is REQUIRED for safe series charging and discharging.
- When charging packs separately for series use on different chargers, it is VERY important that you check the calibration of each charger. To do this, you must simply charge each pack individually on each charger and check voltage. If the voltage of each pack is within the limits as outlined in the steps below, the chargers are very closely calibrated. If the chargers are not closely calibrated and the packs show voltage differing beyond the ranges listed below, you cannot safely use the packs in series (See “Usage” below for more information).
- If charging multiple packs in series at the same time on the same charger you must:
o Make a visual inspection of each pack to check for any obviously damaged, swollen, punctured cells, etc.
o Check the voltage of each pack independently after EVERY flight and before EVERY charge session.
o The voltage of each pack MUST be within 0.01v. This is very easy to check when using two like voltage packs. For example, you may only charge two 3s4p packs together in series as 6s4p if they read 11.10v for one pack and 11.10v (also safe if 11.09v or 11.11v) for the second pack. Actual voltage will of course vary based on the level of discharge for the packs.
o When using two packs of differing voltage, you must pay extra attention to the voltage of the packs and cells before charging them in series. For example, when charging a 2s4p and 3s4p in series as 5s4p you must first read the voltage of each pack individually. The 2s4p reads 8.10v and the 3s4p reads 12.15v after a flight. You must now divide the voltage of the pack by the number of SERIES cells within that pack; 2s4p: 8.10v/2 cells = 4.05v per cell. Now the 3s4p: 12.15v/3 cells = 4.05v per cell. Because the voltage of the INDIVIDUAL cells within each pack share the same voltage, this 2s4p and 3s4p pack are safe to charge in series as a single 5s4p pack. Again, you may ONLY charge packs in series if the voltage of the individual cells in both packs are within 0.01v.
o Never leave your charger unattended when charging any Lithium Polymer battery packs, whether they are individual packs or multiple packs in series!

Usage:

- You must use a high quality digital voltmeter (Capable of readings to 0.01v) to check voltage in order to correctly follow the steps outlined below. Your charger or Whattmeter are NOT accurate ways to measure pack voltage, and the use of a digital voltmeter is REQUIRED for safe series charging and discharging.
- After PROPERLY charging your multiple packs in series, or separately on different chargers for use in series, you must:
o Make a visual inspection of each pack to check for any obviously damaged, swollen, punctured cells, etc
o Check the voltage of each pack independently, even if packs were charged together in series.
o The voltage of each pack MUST be within 0.01v. This is very easy to check when using two like voltage packs. For example, you may only discharge two 3s4p packs together in series as 6s4p if they read 12.60v for one pack and 12.60v (also safe if 12.59v or 12.61v) for the second pack. Actual voltage will of course vary based on the level of charge for the packs.
o When using two packs of differing voltage, you must pay extra attention to the voltage of the packs and cells before charging them in series. For example, when using a 2s4p and 3s4p in series as 5s4p you must first read the voltage of each pack individually. The 2s4p reads 8.40v and the 3s4p reads 12.60v after charging. You must now divide the voltage of the pack by the number of SERIES cells within that pack; 2s4p: 8.40v/2 cells = 4.20v per cell. Now the 3s4p: 12.60v/3 cells = 4.20v per cell. Because the voltage of the INDIVIDUAL cells within each pack share the same voltage, this 2s4p and 3s4p pack are safe to use in series as a single 5s4p pack. Again, you may ONLY discharge packs in series if the voltage of the individual cells in both packs are within 0.01v.
o If after charging your packs in series or individually the voltage differs beyond 0.01v, it is possible to top off the lower voltage pack so it more closely matches the high voltage pack. This is typically more common when charging packs on different chargers, though you must also check packs charged in series independently after charge as well. Be sure to select the PROPER cell count when topping off a nearly fully charged pack; failure to do so will result in a fire!
- After strictly following all the above guidelines and ensuring your packs are within 0.01v, your packs are ready for use in series. However, there are a few steps which must also be taken during the discharge of the packs in series to prevent problems:
o Do not over discharge your packs. It is recommended to only discharge around 90% of the pack capacity. This creates a buffer and will prevent any LiPo pack (whether individual or in series) from becoming over discharged. When a LiPo pack is over discharged cells within the pack will be damaged and may even swell. Thunder Power / Advanced Energy Tech is not responsible for the repair or replacement of packs which have been damaged due to over discharge.
o Always check the voltage of each pack individually after discharge. Do not charge packs that may have been over discharged. Once packs have cooled, repeat the steps for charging.

[Airboss]

thanks i hope everyone reads this.

[cjheli]

Does anyone have good info on storing LiPo for a few weeks or so. I seen info on, they should be at around 60% charged, also info that it didn't matter. If the 60% charge is the answer, then if they were stored at 100%, how bad was that for the LiPo.

Thanks CJ

[nabl74]

Originally Posted by cjheli

Does anyone have good info on storing LiPo for a few weeks or so. I seen info on, they should be at around 60% charged, also info that it didn't matter. If the 60% charge is the answer, then if they were stored at 100%, how bad was that for the LiPo.

Thanks CJ

Best practice for long term storage is to storage charge your pack so that each cell is at around 60%. 3.85v. Then stick in an air tight zip bag or enclosure and put in fridge. Chemical breakdown of battery during storage is reduced below 20deg celcius

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[nabl74]

Originally Posted by cjheli

Does anyone have good info on storing LiPo for a few weeks or so. I seen info on, they should be at around 60% charged, also info that it didn't matter. If the 60% charge is the answer, then if they were stored at 100%, how bad was that for the LiPo.

Thanks CJ

It all comes down to long term life and safety. You wont notice impact when storing your battery at 100% immediately or over a week. But long this practice will result in the pack deteriorating quicker


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