When it comes to lithium cell technology, the lithium polymer (LiPo or Li-poly) and the lithium ion (Li-ion) are significantly different from the commonly-used NiMH and NiCd batteries. There are various aspects to consider before you use lithium cells.
One of the most being safety. While every type of cell should be treated with caution due to energy contained in the batteries, once they are fully charged it is important to know that lithium cells contain the maximum in energy density. These batteries have unique qualities and require extremely specialized safety considerations.
Charging Lithium Polymer Batteries
The lithium cells have to be charged in a very different way than the NiMh and NiCad batteries. These batteries require specialized chargers that are designed in a specific way in order to charge lithium polymer cells. One of the recommended chargers would be the TAHMAZO T26 charger; this is the type of charger that can be used on all cell types and is able to charge up to 10 LiPo cells. This charger features 10 battery memories, which makes it far easier to utilize.
Typically any type of charger that is able to charge the lithium ion will be able to charge the lithium polymer, making sure that the batteries in question have the correct cell count. It is extremely important to note that a NiMh or NiCad-only battery charger is never used to charge the lithium cells because charging the cells is dangerous when using the lithium batteries.
Manufacturers and experts all recommend extreme caution when charging these cell types. One of the first steps in preparing the charger for lithium cells is to make sure the charger has been set to the right cell count or voltage. If this step is missed the battery could potentially burst into violent flames. To date there have been numerous fires that have been caused directly from lithium batteries. For this reason it is now a standard practice that anyone wishing to use lithium polymer batteries should be aware of how to charge the cells and the safety precautions involved.
Below are the guidelines for charging and using lithium polymer batteries:
- Only use the chargers that have been approved for use with lithium batteries. These chargers should be designed for use on Li-Ion and Li-Poly.
- The correct cell-count must be set on the charger. If the user is not informed on how to perform this operation it is advisable to rather use a charger that you do know how to operate or not charge the batteries at all.
- Make sure to balance charge your new lithium battery for the next couple of cycles. After that you can do it every 10th cycle. This is vital due to the risk of a pack that has become unbalanced, thus having the potential to explode. If each of the cells is showing a reading that they are not within at least 0.1 volt to one another, the user needs to charge each of the cells separately up to 4.2 volts, which means they will all be equal. If after the period of each discharge the lithium pack shows up unbalanced, one of the cells are more than likely faulty and the entire pack will need to be replaced. (Of course, some lithium packs are different and will require a different amount of volts for recharging.)
- The batteries and the charger need to be placed onto surfaces that are safe before charging the batteries, which means that if they do catch on fire damages can be contained. Some of the suggestions include fireplaces, Pyrex dishes that are filled with sand or a vented fire safe.
- The batteries should never be charged for more than an hour at a time. Exceeding this time significantly increases the chances of a fire.
- If one of the cells happens to balloon while on charge, the cell should not be punctured while still hot. This will cause a short circuit resulting in overheating. After you have let the cell sit in a fire safe place for at least 2 hours. Discharge the cell/pack slowly by wiring a flashlight bulb of appropriate voltage (higher voltage is ok, lower voltage is no) up to your batteries connector type and attaching the bulb to the battery. Wait until the light is completely off, then throw the battery away. This is an important step to do so the cell is safe enough to throw away.
- The batteries should only be charged in ventilated and open areas. (In the case of a battery rupturing or exploding they will emit dangerous material and fumes.)
- When charging lithium batteries, keep a bucket of sand nearby. This is a cost effective way to extinguish fires. It is very cheap and absolutely necessary.
(Also make sure to check out this battery disposal guide for information regarding instructions and regulations about battery disposal.)
When it comes to handling lithium polymer batteries with care it is important for any user to realize that these batteries can be extremely dangerous. It is very important to follow these safety tips and ensure that the right charger is used.
Featured photo credit: Hexcam via dronetraining.co.uk