Waterproofing the 48V10Ah battery pack

[Christoff]

I bought a Magic Pie II and 48V10Ah LiFEPO4 battery pack at the start of the year. It is my first e-bike and I am very happy- no more traffic and almost no running costs! I have just over 1300km on the odometer so far.

After a week of wet winter weather, my range suddenly decreased by about 40%. Choosing where to look first I decided it is likely the battery pack since I can find no peak power problems, cycling drag (brakes not releasing, or wheel/motor not running freely) or anything else leading me to think it is the motor. Nothing is running hot either.

I opened the battery pack, and was quite relieved that it has a full battery management circuit with each cell connecting to a PCB. I read that Golden Motor did not use a balancing circuit for the LiFEPO4 cells since they claimed the cells would balance upon overcharge but I have yet to discover any LiFEPO manufacturer confirming this. Maybe they realised a BMS is needed and introduced it?

I think I found my culprit after opening the heatshrink: The main wire's crimp was faulty and broke off easily. It must have had a bad connection and added a lot of resistance, possibly causing the charger to switch off early, and also causing some energy loss although I expected it to run hotter if it ate 40% of my pack energy, but maybe the heat was too far from the edge of the pack.

Now that I opened the pack I realised it has absorbed a lot of moisture inside. And salty moisture as well since I drive next to the coast. I will have to do something about the moisture inside the battery pack. Does anyone have any tips? The best I can think is to conformal coat all open connections (or simply paint resin on everything which is cheaper) and dry out the pack in a dri-buddi once a week to make sure the moisture gets out. But a dri-buddi might be too hot.

I need to close the pack again, any tips for replacing the nice big blue heatshrink? I suspect broad plastic cello-tape will have to do.

Is there a topic for batteries?

[Cornelius]

Nothing new with water into the battery; how about a raincoat for the battery?

http://goldenmotor.com/SMF/index.php?topic=2320.msg12611#msg12611

[Marsbar]

What about putting the battery pack into a water proof plastic box?
I did so, completely water proof... also tucked the charger inside!
Also use proper water tight glands...
Drill a drain hole in bottom if you like to be sure no water builds up.

Picture below is just an example, buy a size that fits your needs.

Another suggestion: Make a cover using aluminum or transparent polycarbonate plastic you bend using a heat gun.

[Christoff]

Thanks for all the tips. I like the shower cap type cover idea. Easy solution. I hope my pack is still OK. I'll test the range tomorrow.

[GM Canada]

I opened the battery pack, and was quite relieved that it has a full battery management circuit with each cell connecting to a PCB. I read that Golden Motor did not use a balancing circuit for the LiFEPO4 cells since they claimed the cells would balance upon overcharge but I have yet to discover any LiFEPO manufacturer confirming this. Maybe they realised a BMS is needed and introduced it?

People tend to spread rumours about GM batteries not being as good as they actually are. I suspect its because they like to pay more for the well known brand names. When people mention the GM batteries are quite often half the price they feel obligated to make up things to discount the quality. I have never seen any GM battery packs without a BMS. Now that you have opened your pack you can clearly see how well the liFePO4 batteries are made. For others that have not you can look at the following link to judge for yourself.

http://goldenmotor.com/SMF/index.php?topic=4260.msg24829#msg24829

Gary

[Marsbar]

A bit on the side of the tread, but while speaking of these batteries: It would be interesting to perform drain test of various batteries. By that I mean to charge the batteries fully, then load them with 10A (using a lightbulb or resistor wire) and then the useful time befor the BMS shuts down the battery.

You would need an ampere meter, load (resistor wire or lightbulbs), and possibly a buzzer connected to a relay that starts to sound when the voltage is missing. (So you remember to stop the timer correctly...)

I bought a battery advertised as 48V 15Ah, but looking closer and taking note of the weight I now assume this battery is 10Ah. This was a pain since I needed at least 15Ah got my cycling route.

I am definitely going to test my battery that I bought on e-bay to see what I really got.

[GM Canada]

I have not done any controlled tests but do know the 48v10Ah battery kicks out between 38 and 39 volts and I can get as much as 9.85 Ah out of it.

Gary