How to select the best lipo battery for your flying application.The basic theory and safe practices are discussed and how to avoid a lipo battery fire.
The development of the modern Lithium Polymer (Lipo) battery has made the current crop of airborne vehicles possible. Never before have we been able to use as much electrical power in such a small, light weight package.
The price we must pay for this is offset by the chance of fire! I believe the fire risk can be minimized to the point where it is no longer of concern and we will take you through the steps of selecting the best lipo battery for your application.
If you are replacing an existing battery, or buying another one to extend a flying session, then the first question to ask is what is the physical space available?
It may be possible to use a more up-to-date lipo, that is smaller than the original and maybe has a more electrical capacity (measured in mAh, displayed on the battery) or maybe a larger capacity battery can be used in the space available. (Please check the balance point if a heavier battery is used).
The next information is the voltage of the pack. Lipo cells have a nominal charged voltage of 3.7 volts per cell. Cells are connected together, in series, to generate the voltage required. Thus a 1S battery will be 3.7V nominal, a 2S pack will be 7.4V, a 3S will be 11.1v and so on.
The maximum size generally used today, in a single battery is a 6S pack(22.2V). If a higher voltage is required, then packs can be connected together in series.
The information on this page, should show you how to select the best lipo battery for your application.
Here are the lipo batteries that I have used and my impression of each, from the expensive to the less expensive ( I don't like the word "cheap")
In my experience, they have been the "best lipo battery" for my applications.
You may think you have the best lipo battery, but even those can be a fire hazard!
First of all, double check every connection you make or are about to make to ensure polarity is correct! Make absolutely sure that positive leads are only connected to positive leads and the same with negative leads.
This may sound very basic but mistakes can happen! If polarity is reversed then the lipo will burst into flames! This happened to me recently and was I shocked! Fortunately no serious damage resulted, but I did loose a good battery and destroyed an ESC.
The other most common situation where fires can happen, is during the charging of lipo batteries. Only use a charger that is specifically intended to charge lithium polymer batteries and has the capacity to charge your pack.
If your battery came with a charger then you are probably OK. Just ensure that any switches are in the correct position and read the manual that came with your package.
It is a good idea to use a fireproof charging bag, during the charge cycle. That way, if a fire does start, then it can be contained and hopefully no damage to property will result.
The Liposack is a soft, fireproof lipo battery bag that will be replaced by the manufacturer,if damaged by a battery fire.
There are other types available, but this is, I believe, the original.
Another idea is to use a ceramic container of some description. I use an old metal biscuit tin that will not burn, but it is capable of conducting electricity yet it has worked well for me.
Click on the photo to visit Amazon.
The best lipo battery connectors are the ones that work for you! You have to decide which connector system you would prefer and then, if required, replace, by soldering on your connector of choice or use an adapter.
I don't think that any of these can be described as the "best Lipo battery connector" Each battery manufacturer favors there own and all are good quality and should perform well.
I must thank Roger's Hobby Center for the use of the photos of the connectors. They have an excellent hobby shop and also an article on their web site regarding lipos. Click here to see this informative article.
Some people find soldering a challenge and the alternative is to use connector adapters. I started to do this and find the results very good. Some purists will object that the more connectors their are, the greater the chance of a problem. But I think that a solid, well built adapter is much preferable to a poorly soldered connector,especially if our aim is to produce the best lipo battery assembly we can!
Now when I buy a new battery, I also order the appropriate adapter. The links below may help you locate the one you need.
I have been used to storing re-chargeable batteries at full voltage, for a long time. The nicd and nimh packs we have been using for years always seemed to prefer a full charge or no charge when in storage. The lipo is different! They should be stored at a voltage of approximately 3.8V per cell .
When at full charge, they will be at 4.2V per cell and the nominal voltage is 3.7V.
When you return from a flying session, connect the batteries up to your charger and select "Storage". The battery will be charged or discharged until the 3.8V per cell level is reached. Now it can be safely stored, until the next flying session. Remember I prefer to charge at a 1C rate, so I charge the night before I am planning a visit to the club field.
By using this storage voltage, the life of your batteries will dramatically increase!
If you are designing your own electric installation then you must do a few calculations. I found, awhile ago, that the tables shown on the Castle Creations web site save a lot of time and are accurate.
They have tables for prop driven airplanes, ducted fans and helicopters. Click here to visit their site and use these very useful tools.
Lipos do Puff-up or bulge sometimes. If it is only a small amount and the battery still takes a full charge and lasts as long as it always did, then you can continue to use it.
It may be a sign that the life of the battery is coming to an end, so keep a close eye on it's performance.
DO NOT try to relieve the bulge by piercing the covering! If you try this, it will not work and a fire or other nasty things may happen! I have heard of many fixes for this problem but none of them can be safe.
Even the best lipo battery can start to "puff" and I have tried a few thing to try to reduce it, but for me none of them work! (Like putting them in the freezer).
When a battery is no longer of use to us, because it cannot take a full charge or runs down too fast, it still may contain electrical power and thus could still cause a fire.
Before dumping it in the trash, it should be completely discharged. One way of doing this is to leave it in a salt water solution until the volt meter shows 0 volts. Add salt to a bucket of water, until no more will dissolve, then dump in the old battery. Leave it for 24 hours and check the voltage,
You can make a simple discharge device by soldering wires and a connector onto an automotive light bulb, connect it to the battery and let it sit. Be careful and use a lipo discharge bag as batteries can get hot when voltage is very low.
It is worth checking at your local hobby shop. Some do offer a lipo disposal service that can make this procedure very simple!