ASK Cubby- More Of Your Questions, Less Of My Answers
Always a treat to read your columns. I have been wondering about something I have read around “the internets” on LiPo break-in. Some say yes, some say no… some swear by it others have never done it and say it’s a myth. What is the deal? Do lipos need to be broken in for longer life/ better performance? Is internal resistance affected? What is internal resistance anyway? Thanks for your words wisdom.
Cubby- Well hola there Gustavo (reminds me of Breaking Bad), thanks for writing in.
So let’s see, you want to know if it is worth your while to break-in a new LiPo battery. During the first few cycles of a LiPo, it will slightly increase its output voltage. This curve goes up for a number of cycles, lets say during the first 10, after that, the pack will start producing slightly less voltage as it “wears out”.
Back in the day, I tried various “break-in” charge rates, as well as discharge rates, while testing break-in cycling on a West Mountain CBA. Some did seem to produce improved discharge voltage down the line, others, not so much. The main thing I did see what that different cells preferred different rates (charge, discharge, or both) during the “break-in” period. This told me that to get much, if any, benefit from a new pack, I would first spends hundreds of hours figuring out an optimal break in procedure.
When you work with batteries in a professional setting (actual real lab testing), it is extremely time intensive. If you read on some Joe-Blow forum somewhere that some guys swears he has a great LiPo break-in method, 99.999999% of the time they are full of it. They have not put in the hundreds of hours with dozens of packs required to find such a thing, and even they had, from what I have seen first hand, that would only really work for one particular cell. Otherwise, they all tend to rise in voltage for the first 5-10 cycles, regardless of how they are treated during those initial cycles.
About internal resistance, it was a big term back in the NiMH days and is useful for relating the output of one pack compared to another, but now days it really is just confusing for new hobbyists. Typically old school racers types will bust out “My uber race pack has an internal resistance of .0000000001 mΩ and it puts out soooo much power!!” when they are trying to sound like they know what they are doing. What us industry types would rather people look at is simply voltage under load. Saying a pack puts out 7 volts under a 30 amp load is typically easier for a noobie to understand than internal resistance.
So, to boil it down, I don’t believe in “breaking in” LiPo packs, get your money out of them by just driving them!
And, if you are looking for real specs to compare packs, those are truly far and few between. Before buying a pack I would recommend looking for first hand recommendations on-line, or a review by a reputable tester.
“Old School Battery Question
Hey Cubby, It’s been a while.
So we all know and love LiPos and are used to making sure that we store them at the correct voltage when not in use, but what is the preferred way to store old-school NiMH and NiCd batteries?
I picked up a couple of Tamiya dump trucks for my 4 year old kids (these things are surprisingly robust and fun), but naturally my local hobby store only had NiMH and NiCd stick packs that would fit. There’s no documentation with the batteries, and there are numerous schools of thought on the interwebs about whether to store them full, discharged or 40-50%. Can you shine any light on this issue?
Cubby- Yo hey Glen, thanks for writing in. That is pretty freak’n cool that you hooked your kids up with some Tamiya dump trucks! See people, that’s how the hobby is supposed to work, and that’s how we keep our hobby going.
OK, so about modern NiMH and NiCd cells, I really have no clue. I haven’t tested any in forever, and I rarely use them here at work. And, when I do use them for work, they are cheap RTR packs they we certainly do not treat very well. LOL. So… back in the day we always stored those types of cells completely discharged. I don’t know if that is the best way to go on the newer cells or not, and I am certainly not going to do the testing to find out. LOL.
However, what I would recommend is cutting the check for some LiPos that come in the true/curved NiMH form factor. They are not easy to find, but you’ll instantly get more performance, plus you won’t have to worry about the false-peaking problems of Nickel based cells, which is really the part that keeps me away from them now days.
Have a dire question? Need an answer desperately? Have a rant that you just HAVE to get off your chest? Email me- thecubreportrc at gmail dot com.
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