Battery on Freego Eagle

[Mike63]

Hi....I'm still looking to sell my Freego Eagle.
....It's 3 weeks since I last put it on charge...I tested it with volt meter it registered 41.6
....I plugged it into charger and it immediately went to green.

Is this a fair indication that the battery is perfect ?

....many thanks....Mike

 

[flecc]

Not necessarily, it could mean more than one thing, for example BMS failure. However, it's probably ok since lithium cells don't self discharge, the only current drain in storage being the minimal amount the BMS uses when quiescent.

If you go for a three or four mile run using the power liberally it should then have lost enough content to start the recharge and confirm it's all ok.

 

[Mike63]

Cheers for that flecc, If it's fine tomorrow I'll take it for a run, I wouldn't want to mess it up though,
....looks like new at the moment.
....many thanks.

 

[John F]

Not necessarily, it could mean more than one thing, for example BMS failure. However, it's probably ok since lithium cells don't self discharge, the only current drain in storage being the minimal amount the BMS uses when quiescent.

If you go for a three or four mile run using the power liberally it should then have lost enough content to start the recharge and confirm it's all ok.

I'm curious to know more about what the BMS does. What exactly does it do when the battery is not in use for example?

I hope mine is preventing it from catching fire when it's parked up in the garage! (only half joking)

 

[flecc]

It's function is to control charging, protecting cells from overcharge and distributing the charge to ensure all cells are charged to the same level. The BMS switches off the charge when charging is complete, not needing a smart charger.

It's just on standby when the battery isn't in use but still connected so it's ready for action when required. The tiny amount of current needed then comes from one of the cells. A very few select batteries have BMS with additional sophisticated functions, for example some batteries have a sleep mode that switches off the BMS after a period in standby to conserve the charge content. They wake up when reconnected to a charger. Most though are just charge controllers.

 

[John F]

It's function is to control charging, protecting cells from overcharge and distributing the charge to ensure all cells are charged to the same level. The BMS switches off the charge when charging is complete, not needing a smart charger.

It's just on standby when the battery isn't in use but still connected so it's ready for action when required. The tiny amount of current needed then comes from one of the cells. A very few select batteries have BMS with additional sophisticated functions, for example some batteries have a sleep mode that switches off the BMS after a period in standby to conserve the charge content. They wake up when reconnected to a charger. Most though are just charge controllers.

Good info thanks. It's nothing to do with safety/overheating then?

 

[Deleted member 4366]

Some BMSs have heat sensors that are buried in the cells. They will then switch off charging if discharging when they detect over-temperature. BMSs normally also have over-current protection that switches off discharge when the current is too high.

Batteries don't over-heat and catch fire on their own.

All need managing when charging and discharging whether you do it with or without a BMS. You have belt and braces in that the controller has low voltage and over-discharge rate control, and the charger has high voltage control, but these are done on the basis of pack voltage. They can't see if one cell is down to zero volts, which means that, without a balancing function, the remaining cells will be charged too high and discharged too low.

So, as long as you balance the cells either manually or with a BMS, there's very little risk of fire. The only other risk is a short-circuit from faulty wiring, but that's highly unlikely to happen while sitting in your garage unless the cat jumps on it and knocks it onto the floor.

 

[Mike63]

....I plugged it into charger and it immediately went to green.

Re. my original post....
I did not make it clear, I had not actually used the bike for 3 weeks and I assumed that with it going straight to green meant that it was fully charged.

Is this not the case ?

cheers....Mike

 

[Deleted member 4366]

It's fully charged. You have 41.7v. The fact that it charges up and holds its voltage doesn't necessarily mean that the battery is good. I've had Phylion ones that do that, but only give about 2aH. Only a discharge test will show how worn-out the battery is.

 

[Mike63]

....thanks d8veh,..... what's a discharge test ? .... can I do it ? ....how do I do it ?

cheers....Mike

 

[Deleted member 4366]

You put a wattmeter between the battery and controller,then run the bike 'til the battery's flat. You need the wattmeter where you can see it if it's the type that doesn't have a memory, otherwise you have to do it again because the wattmeter goes off with the battery unless you convert it to back-up power.

 

[flecc]

If your bike is throttle controlled or is a pedelec without torque control over power, to see if the battery is up to powering the bike at high discharges, you can tackle a steep hill that's a bit beyond it's capabilities. Ride up it giving minimal or no pedal assistance and if the battery drives the motor down to almost stalling point without cutting out, it's passed it's high discharge test for your bike.

That doesn't indicate the battery capacity since some cells can high discharge even with much reduced capacity, for the capacity you need to do as d8veh has posted just above to measure the content used.

 

[Wisper Bikes]

Thanks Flecc and Dave for your help and support, I do hope visitors to Pedelecs realise the high levels of expertise freely available here.

Happy new year to you!

All the best

David