A bms is good for people who are not knowledgeable about cell voltages, or for people who couldn't car less, or for people who just want simple worry free plug in and forget!
However I've learned that you do not need a bms at all, while out on a ride get a few of these, one for each pack
You have to set the low voltage alarm so you know it's time to back off on the throttle or even to shut off the controller altogether.
Some bms also add another 100-200 Euros to the price of the batteries and they don't have a very good reliability record, though I had no issues with my Ping bms!
LiPo is definitely the best in the business for E-Bikes as they pack some energy and can discharge very high C from a very small pack, LiFeP04 can't begin to touch it! Sure A123 make good cells but they can't offer the high discharge and charge rates of LiPo and they are very expensive! You can make a cheap 16ah 44 volt pack for around 330 U.S.D.
Then there is around 100 U.S.D for shipping to Europe, and maybe the same for other countries.
44 volts is plenty for my geared motor but not so for pie users who would need 60+ volts for decent speed! But the beauty of LiPo is I can change my pack from 16ah to 8ah for short trips or cycles that I want to exercise, I can dump the extra weight, you can't do that with a 20ah ping! And the 8ah pack will weigh only 2.5 kgs or the 16ah 5.5. 32ah 44V LiPo would weigh around the same as a 20ah Ping!
The cost of the charger and power supply can add another 150-200+ depending on how fast you want to charge. My Icharger setup will be capable of charging at around 20 amps, and should charge my 16ah pack in just under an hour, of course you can charge much faster than that but it get's damn expensive and besides 1 hour is plenty fast, much better than 4 hours for a 48V 20ah ping with a 5 amp charger!
And power supply
Of course you could use a bulk charger and disconnect the ping bms and charge it much faster and use it's normal bms for discharge or to balance now and then, though I never had a balance issue with the ping and the lights always came on within 1-2 mins of each other!
Faster charging LiPo gets expensive, and it's the power supply that's the most expensive, you can pay up to 350 U.S.D for a meanwell 24V 1500watt P.S.U and I think many people in the U.S and Canada have problems after that on 120AC mains!
You can be lucky to find a power supply cheap on e-bay used, or new. SOme guys even bulk charge with just the meanwell, they seem to be the best out there!
Say my pack would be 49.44 volts charged, going by 4.15 ish seems to be the agreed maximum voltage to extend the life of LiPo to some say 800+ cycles! So you set your meanwell to 49.44 volts and it will limit the current when the desired voltage is reached!
That way of charging is usually done after a few cycles to make sure all the cells are closely matched because you will be charging without balancing and balancing is not necessary most of the time if you don't bring your pact to lvc all the time!
It's the easiest way to charge, because for my Icharger I'll have to break my pack's series packs into parallel to charge while it monitors the cells, no big deal really, but you could get a cheap 10 amp meanwell for charging while out on the road without the need to bring the Icharger along!
I know it may seem daunting for those used to plug in and forget
but once you do your research and pay attention to your wiring you will be fine. I'm still waiting for my batteries!
