Replacing a failed EBike charger....general public with no knowledge of electronics

[Flyback]

H

Supposing someone buys an electric bike with a charger for its 48V Lithium battery. Then 18 months later, the charger fails. The person has to then buy another charger, but may have no idea what kind to get. The charger that shipped with the bike may well be obsolete. They may then buy a replacement charger with far too high charge current , and thereby either blow the battery up, or severely reduce its lifetime, due to overheating it during charging.

How is the industry addressing this issue?..or isn’t it?

 

[alec_t]

I doubt the issue is being addressed. The manufacturers would prefer you just to buy another bike .
Given that reputable lithium cells come with a BMS attached, it would seem relatively straightforward to modify the BMS itself to incorporate a charge limiter if it doesn't already have one.

 

[Flyback]

Given that reputable lithium cells come with a BMS attached, it would seem relatively straightforward to modify the BMS itself to incorporate a charge limiter if it doesn't already have one.

Thanks, i wondered that, but that would mean an external current source driving current into an internal current source, which would be problematic...unless the battery has a label on it saying "please supply me with 48V", and then it does the current source charging from there...but who knows?

I would have thought all there is inside the battery pack is the charge balancer and over/undervoltage switch ...but does anybody confirm even this?

 

[Nigel Goodwin]

I doubt the issue is being addressed. The manufacturers would prefer you just to buy another bike .
Given that reputable lithium cells come with a BMS attached, it would seem relatively straightforward to modify the BMS itself to incorporate a charge limiter if it doesn't already have one.

I would completely disagree with that statement, small numbers of cells are available with built-in protection - nothing to do with 'reputable' manufacturers in any case. The vast majority of cells have no protection (not needed) and it's all done externally, plus charge balancing as well.

 

[Flyback]

The vast majority of cells have no protection (not needed) and it's all done externally, plus charge balancing as well.

Thanks, thats what i feared...my fear is enormous because Joe Public havent got a clue how to pick a charger for a given battery...so we are going to see battery fires, and/or quickly worn out lithium cells due to them being overcharged...loads of lithium batts in the scrap heap.....environmental nightmare.

And when it comes to charge balancing, the public have even less of a clue.......even more battery fires!

 

[Nigel Goodwin]

Thanks, i wondered that, but that would mean an external current source driving current into an internal current source, which would be problematic...unless the battery has a label on it saying "please supply me with 48V", and then it does the current source charging from there...but who knows?

I would have thought all there is inside the battery pack is the charge balancer and over/undervoltage switch ...but does anybody confirm even this?

I would expect charge balancing and protection to be in the battery pack (they couldn't really be in the charger), and the charging requirements are standard and fairly simple. Constant current initially, switching to constant voltage once the pack reaches 4.2V per cell - then continuing charging until the current falls to the required fully charged level. The actual currents involved depend on how fast you want the pack to charge, and how long you want the batteries to last - the faster you charge them the shorter their live, and also the less charge they will accept.

I usually charge my 2600mA/H 4S1P packs at 520mA and the cut off current is 130mA - this is an 'easy' charge and provided maximum battery life and maximum charge in the batteries.

You can buy numerous Li-Ion chargers, and they are specified by their output voltage (or how many cells in series they are designed for) and their charge current.

 

[Flyback]

the charging requirements are standard and fairly simple. Constant current initially, switching to constant voltage once the pack reaches 4.2V per cell - then continuing charging until the current falls to the required fully charged level. The actual currents involved depend on how fast you want the pack to charge, and how long you want the batteries to last - the faster you charge them the shorter their live, and also the less charge they will accept.

Thanks, totally agree.....though as you would i believe agree..the general public have no idea what you just said...they are just going to shove any charger into any battery pack and we will see flames and fire.

 

[Nigel Goodwin]

Thanks, thats what i feared...my fear is enormous because Joe Public havent got a clue how to pick a charger for a given battery...so we are going to see battery fires, and/or quickly worn out lithium cells due to them being overcharged...loads of lithium batts in the scrap heap.....environmental nightmare.

And when it comes to charge balancing, the public have even less of a clue.......even more battery fires!

Why?, the cells don't have protection - but the packs do - and many packs are sealed, so you can't even mess with them. If they don't contain charge balancing circuits the usual failure mode is one or more cells going S/C - so the software in my designs monitors the charge voltage, and if it's still below a preset level after ten minutes charging it's aborted as 'battery faulty'.

For a 4S battery full voltage is 4.2V, and 3.2V is about as low as you should discharge them - so a completely flat pack should be around 12.8 volts. With that figure in mind, my software looks for above 12V after ten minutes of charging.

 

[Nigel Goodwin]

Thanks, totally agree.....though as you would i believe agree..the general public have no idea what you just said...they are just going to shove any charger into any battery pack and we will see flames and fire.

Why would you see flames and fire? - presumably the packs internal protection circuits should prevent that - over voltage, cut the connection - over current, cut the connection - over heating, cut the connection - over discharge, cut the connection.

 

[alec_t]

I would completely disagree with that statement, small numbers of cells are available with built-in protection

My bad. I meant 'battery packs' rather than 'cells'.