Battery Questions Please (Samsung 36v 9ah Lithium Ion Battery)

[Forever Blue]

If anyone can please answer any of these, I'd appreciate it:

1) If you overcharge a battery accidentally even once, will that damage the battery by giving the bike LESS riding time? Because just 1x we accidentally overcharged by 3 hrs, but had 1/2 the riding time we used to...1.5 hrs instead of 3 hrs & we've been biking the same terrain so what gives?

2) Which is better or does it matter...to ride the bike till it's completely drained all the way, then charge it fully OR when it's almost drained, then charge it fully?

3) After a battery's 100% charged, after how many days of non-use does it start draining?

4) Any tips or tricks on how to lengthen the life of the battery in general?

 

[PedalUma]

Hi,
Don't worry about it. Just have fun!
1) These are quality cells. Likely you have a quality BMS to go with them. That is the management chip. It will stop charging when full. Try charging it with the battery turned off sometime. Then turn the battery on to fill to the last 10% if you need a full charge that day.
2) Batteries 'like' to be between 20 to 90% full. Li batteries do not have 'memory' but never drain it all the way.
3) If you store a battery, do it at about 80% then after 3 months plug it in for 10 minutes and check it. It should be back at 80%.
4) These cells are good for 1,000 charges. That is once per week for 19-years. It will be obsolete within five-years so do not sweat it.

 

[Forever Blue]

Thanks a lot, PedalUma. I just want the LONGEST (in which the longer, the more fun, ha!) riding time as possible. My fiance' was even wanting to buy us each a 2nd battery, so we'll have twice as much riding time when the 1st ones are drained. But those batteries are like $500-600 each, so I don't know about that!

 

[theemartymac]

Thanks a lot, PedalUma. I just want the LONGEST (in which the longer, the more fun, ha!) riding time as possible. My fiance' was even wanting to buy us each a 2nd battery, so we'll have twice as much riding time when the 1st ones are drained. But those batteries are like $500-600 each, so I don't know about that!

I agree with Uma, don't sweat the petty stuff (and don't pet the sweaty stuff, but I digress ;-) ). The BMS should manage it fine, and it would have to be a pretty bad charger to not have any auto-finish feature. Just don't leave it plugged in unnecessarily.

As for the second battery, I love having two as it eliminates range anxiety altogether, and it allows me to rotate the batteries so I can usually just pop the fresh one in after a ride (try and commute 2-3 days a week in the summer), and charge the other one later, after it cools off or warms up in the winter. I have a charger that allows me to select the charge level and rate, so I slow charge to 80% and top up the night before if I'm planning a big ride. But you're right on the cost. Especially right now as it seems everyone has spiked their prices quite dramatically as of late. Not a great time to buy.

If you both have the same battery pack on your bikes, you could probably just get one spare if you were looking for the safety margin as well. If one of you is burning much more battery than the other, swap it out at maybe 40% with the full one, and then let the other rider use that 40% as a backup if they run low on the way home. And another even cheaper option if you have reasonable access to plugs on your route is to pick up a charger that can charge faster (e.g. 5-6amp) and then you can top a low bike up quite a bit during a short coffee break. But fast charging is harder on the battery, so that is probably not the best option for frequent rides.

 

[Gionnirocket]

If anyone can please answer any of these, I'd appreciate it:

1) If you overcharge a battery accidentally even once, will that damage the battery by giving the bike LESS riding time? Because just 1x we accidentally overcharged by 3 hrs, but had 1/2 the riding time we used to...1.5 hrs instead of 3 hrs & we've been biking the same terrain so what gives?

2) Which is better or does it matter...to ride the bike till it's completely drained all the way, then charge it fully OR when it's almost drained, then charge it fully?

3) After a battery's 100% charged, after how many days of non-use does it start draining?

4) Any tips or tricks on how to lengthen the life of the battery in general?

This is a good thread for you to read.
E-Bike Battery Guide

 

[harryS]

Batteries are designed so that they shut off charging when full. They cannot be overcharged (not easily) . So you could leave the charger on forever, and the battery would not overcharge. It's still not a good idea. Some chargers are cheap and will overheat,. If the charger caught fire, well, that's not the battery's fault and it's one reason why we try to unplug everything when the charging is done.

But in answer to your question, if you managed to overcharge a lithium battery even once, you just made it into a time bomb. THe same goes if you managed to over discharge it, run it truly flat. Battery makers put in safety circuits so you cannot do either.

 

[Forever Blue]

Thanks a lot, theemartymac, Gionniorocket, & harryS. Buying 2 more new batteries is the price of another whole bike almost. I think I'd rather buy a different bike instead before 2 more batteries for the ones we have.
theemartymac, to comment on something you said, fiance' & I use up the same amount of battery when we bike since neither of us ever goes biking w/o the other or some other route, etc., but the, "1 battery purchase" is a good suggestion!