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GLOUCESTER ELECTRIC RACING CAR CLUB
New Club Rules on the Safe use of Li-Po Batteries
When the club decided to allow the use of Lithium Polyester (Li-Po) batteries last year we stipulated in our rules that these batteries should be charged in accordance with the BRCA’s guide to their safe use. We also stipulated that all Li-Po users charge their cells in fireproof bags. Following representations from some members and clarification from the BRCA about the use of LiPo’s, we have decided to revise our rules to bring them into line with the latest thinking, based on the now extensive experience gathered from their use. As a result, we will no longer require that LiPo’s be charged in fireproof bags. That said, you should remember that
any rechargeable battery that is currently on the market has a small risk of explosion, fire, and smoke emission if not handled properly. Lithium (LiPo) batteries are no different, neither are they fundamentally unsafe. However, they do need to be treated with respect. The following precautions should help exploit the full potential of Li-Po batteries, without having a major incident.
In accordance with BRCA rules, all Lithium Polymer (a.k.a. Li-Poly/LiPo) battery packs must have a hard, protective case that completely envelopes the cell(s). Foil coated battery packs are specifically banned. Individual cells used in the construction of the battery shall be rated at 3.7 volts nominal and the pack shall be 2 cells in series. All LiPo packs must be charged with a LiPo-capable charger using the industry standard CC/CV (Constant Current/Constant Voltage) charge profile. LiPo batteries may be charged to a maximum of 8.40V +/-0.04V. Deliberate overcharging is a serious safety hazard and anyone found doing so will have their club membership suspended.
General Precautions
- Only charge LiPo batteries on a charger specifically design for LiPo batteries. Always ensure you use the correct charging voltage for the cell count. This will be 7.4v (2S) for car packs.
- The maximum charge rate must not exceed 1C, e.g. 3.2A for a 3200 mAh pack. For best charging, low charge rates should be used where possible.
- Double check the charge voltage (or cell count), mAh, and current settings on your charger before each charge.
- If you leave charging LiPo cells unattended (i.e. to race) ensure that someone nearby keeps an eye on them for you and knows how to turn off your charger when the charge process is complete.
- Check your charger for safety. After charging, check battery with a digital voltmeter, the voltage for a fully charged pack should be between 8.32V to 8.45V.
- The minimum safe discharge voltage is 6.0V (3.0V) per cell when not on load. Cells allowed to drop below this figure may not recharge. Therefore, when you finish racing always ensure you disconnect you battery from the ESC. Failure to do so may well drain the battery below 6.0V.
- A number of the electronic speed controllers have a LiPo feature built into their software; make sure that this has been enabled. Otherwise fit a LiPo cut-off device.
- Use connectors that can not be short circuited. Under no circumstances should the ESC wires be soldered directly to your battery.
- Do not short the battery as it may catch fire. If you accidentally short a battery, place it outside, inform race control and then observe the battery for 10 minutes. It may swell up and possibly catch on fire.
- LiPo packs are designed for operating temperatures up to 40°C and under no circumstances must they become hotter than 60°C.
- If a pack is involved in a crash or is otherwise damaged, remove the pack from the model and inspect for damage to the pack and the wiring/connections.
- · Lithium polymer batteries do not vent. If the integrity of the battery is compromised, swelling will occur. If the battery is damaged and the case begins to expand, discontinue use immediately and place outside the building.
Thank you for your co-operation.
Ashley Wirdnam
Secretary
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