Battery tenders KILL batteries
I can't tell you how often I've had this discussion with folks around the airport. This is only from my experience in both certified and now experimental world but I can tell you if you ever meet someone that manufactures batteries and can sit down with them to have a beer and ask them to tell you how to make a battery last a very long time, a battery tender will not come up in the conversation in a positive manner. If you have a lead acid battery just fly your plane often, that's it. Now, if you do want to purchase one of those fancy polymer batteries then you need to understand how those batteries work. I BEG YOU ALL to do your homework. I am not going to discuss it on this forum but as my friends I will tell you my experience if you want to know but privately.
Bottom line, regardless of what battery you choose to put in your plane, make sure you understand the chemistry of it and don't just throw a battery tender on it because that's what the factory "recommends".
I also fly Electric RC planes and let me tell you, the batteries for those things aren't cheap. Almost all electric RC's use LIPO (lithium polymer)batteries. When I first made the move to go from Gas to Electric RCs I really didn't understand LIPO, not many did. After about a year I noticed that the $100+ batteries that I was buying for my RCs were not holding charge properly and I was also reading about these fires that were burning down people's homes and shops where the cause was found to be LIPO. Well that obviously opened my eyes and I started to educate myself on LIP batteries. Not just for safety (although that was the primary motivator) but those darn things were expensive and were only lasting 6 to 12 months. I found out after my research that I was storing my LIPO batteries incorrectly and that I should only store my batteries at around 50% of its fully charged voltage. Imagine my surprise when I found this out and knew that I was charging ALL of my batteries to full charge week after week regardless of how often I was flying RC. Full disclosure here is that I actually thought it was bad for the batteries to be stored if they weren't fully charged. Why? Because I had heard that about other rechargeable batteries such as NiMH batteries. Well shame on me for not doing my research before hand and Thank the Good Lord for those LIPOs not combusting due to my un-educated method of storage.
My point in this long message is please do your homework on what you are putting in your plane and understand the history of it. Manufacturers rarely if ever want to admit they are at fault. Trust me I tried to work with them when we had our incident but I wasn't successful in getting them to put a warning with their product or at least a firm message on how to maintain their batteries.
