Balancing an Ebike battery

[johnnyb47]

Hi,
Today at work I was having a chat with a work colleague on how to balance an Ebike battery.My understanding is that every few weeks you should charge the battery fully until the red light on the charger turns to green and then instead of unplugging it, leave it on for an hour or so because this is when the balancing takes place.
He disagrees and says the balancing takes place while the red light is on and that when it turns green the charger has then completely switched off and should be unplugged immediately.
Is there anybody here who knows more about this,than us couple of Wally's at work today.
All the very best,
Johnny.

 

[Jotheboat]

The manufacturer is the one to ask?

 

[Drago]

It depends completely on the manufacturer and whatever on board BMS the battery may or may not have.

 

[wiggydiggy]

I've never heard of 'balancing a battery', does it involve scales

My own Bosch Battery can be charged at any level, or have its charge interupted, with no ill effects. In fact the advice the guide I have for it tells me fully charging/discharging the battery puts extra load on the cells, and can shorten its life. It does have automatic cut off for when it's fully charged. Generally unlesss I am planning a ride of above 50 miles (the range is normally upto 55miles ish) I'll not charge it fully.

 

[Dadam]

I've heard of it. Depends on how sophisticated the BMS is but usually you don't have to worry about it. Certainly not every few weeks.
A battery is a bunch of individual cells wired up together. Each one might have a slightly different voltage. If a few are too low, the battery will stop providing much power when there's still energy in many of the cells. In this case the controller will stop the assist to avoid damaging the cells so this reduces the bike's of range. Depending on the BMS it might be programmed to do this after it registers "full" or it might be a case of letting it fully discharge and then recharging. Contact manufacturer and ask them before messing about.

 

[fossyant]

One would assume the 'decent' packs have a fairly sophisticated battery management system - so see what the manufacturer says.

A simple example is li-po's for battery lights - I often charge a 4 cell battery with the basic power adapter - there is no battery management. Once in a while I'll take out the batteries and pop in my smart charger. The cells all do tend to charge to full within a short time scale of each other.

The battery management circuit will do this for you, and I would assume occasional full charges are worth doing.

 

[albion]

It really depends on usage. Those fires are likely caused by batteries without balancing as part of their makeup as well as them containing used cells. When this happens it is possible they also fail to detect dead cells, the bms being a fairly dumb charging system.

A recommendation for new bikes is to drain the battery flat, charge to 100% and then leave it on charge for 24 hours. Balancing is one cell at a time so the process is slow.
Repeat this every 3 or 6 months depending on how much you use it. Too often is also bad too as draining flat can also reduce the number of charge cycles dramatically.

Store at about 40% charge and charge up before a ride if you can.