Battery life and testing %?

Barrio Barranco

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Nov 24, 2018
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My battery was on the last bar when I got in tonight and the range left was 4km...(whew!). I let the battery acclimatise/cool in the man cave and put it on a timer charge for 2 hrs (supposed to be 4.5 hrs on a 4A charger to fully charge). After 1.5 hrs I caught the two move to three solid lights and the 4th starting to flash so wanting to leave it at 60% I switched it off (but when I now push the test button 4 show up out of the 5....)
Is there any way of testing a Bosch battery with a multimeter to work out what % it is at? I've read that not fully charging (80 or even 90%)is a good thing and it only needs done 100% occasionally to balance the cells? Bosch have this primitive system it seems- or if I'm out for a blast at night that doesn't require maximum range do I just charge it until the 4th bar turns solid/5th flashes??
I believe that the charging is quickest until the last 20% anyway and it slows right down at this point- from what I've tested so far that first bar(like the first 10-20% of my phone) doesn't last long in use and I'm getting about 8km before it drops to 4....
To test the Bosch I'd need to know what of the 3 terminals is what...don't want a shorting/fire lol!!
 

soundwave

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i dont think you can test them with a dvm as it will only fully turn on when it is on the bike tho dealers can check it and do a discharge test if they have one.

the 5th bar is the bms balancing all the cells why it takes so long but as for usage these things like to be used so it is best to let it fully charge as you dont want the cells to get way out of whack and then get problems with it not charging if some cells have gone to far out of whack voltage wise.
 
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vfr400

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If you like doing what you read on the internet, have a go at this. Not only will it save you thousands of pounds in food bills, but they say that you'll be much healthier for it.

After you've tried it for yourself, have another think about what you're doing with your battery and what Bosch say you should do with it.
 
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Nealh

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Charge to full before each use to balance cells/battery, the cases aren't the easiest to open and you don't want to be messing with manual balancing in case you brick the battery if an error is made.
 

GLJoe

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I've read that not fully charging (80 or even 90%)is a good thing and it only needs done 100% occasionally to balance the cells? Bosch have this primitive system it seems
Charging to 80% isn't itself the 'good thing'. Its more a case of being a 'bad thing' to LEAVE the battery standing when at 100% charge.

And you say Bosch have a primitive system. How do you know this? its possible that the Bosch charging and balancing system is more sophisticated than most others out there (and as such, to counter Soundwave's comment, it may not actually be doing balancing in the final fifth segment of charge - the slowdown could simply be the slowdown of the CC/CV charge curve and it might actually be able to balance during the whole part of the charge!).
But only the Bosch designers seem to know for certain.

Until we know, its looking as if the best way to care for the batteries is to do as Nealh said - charge the batteries fully before you use them (being at 100% charge for a few hours isn't a problem). Ride your bike. Leave it in the partially discharged state when finished (leaving the battery stand at say 20% is even better than leaving it at 80%!). Charge back up before you ride again.
If you can't forward plan enough to be able to do that. Just charge it to 100% and be done with it!!
 
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Nealh

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Charging to a & level say 80% and discharging and leaving to rest at 80% are two different cases all together.

From a low discharge state and stopping charging at 80% you have more chance of the balance being out. Discharging to 80% or any voltage above lvc is likely to remain balanced as the bms general looks after this side quite well so leaving in a discharged SOC before recharging will be fine.

Any messing with a Bosch internally could lead t the BMS shutting down/bricking so best to keep to a simple charge regime of using it & leaving it at rest voltage and then fully charge before use again.
 
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Barrio Barranco

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Nov 24, 2018
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SO, this is getting confusing now....yesterday I ran it down showing 4km to go. So it was almost fully discharged. It's now Monday, I work 9-5 and won't be going on it again until the weekend so do I :
A- leave it until the next ride (ie timer charge it say Saturday before I want to go out? But leaving a depleted battery is bad isn't it?)
B- Partially charge it to get some juice in it, then fully charge it before use- but then what does stopping the charge at say halfway do to balancing etc? Is this bad?
C- Fully charge it then have to go out on TURBO and find a hill to bring it back to 60% then top it up before next use? Total ball ache and I'd be out on it at bleedin midnight if I'd done this yesterday?
D- Cut my runs short so I never use the battery once it drops to the last bar? Nightmare....
E - Buy another battery (£600)and when it drops to 1 bar swap it over? Then whatever state they are both in when I get back I leave to charge before next trip??

Option B seems logical as long as I fully charge every time ??? Is it?
 

Andy McNish

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Nov 28, 2018
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Plug it in the evening before your next morning ride (or in the morning if you are doing an afternoon or evening ride). Just try not to leave it 100% charged for days on end.

If you are worried it being almost dischargd then charge it to 3 bars now and leave it stored at that until the night before your next ride.

Everything else is overthinking IMHO.
 
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Barrio Barranco

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This says:
"Partial and random charge is fine; does not need full charge; lower voltage limit preferred; keep battery cool"

https://batteryuniversity.com/learn/article/do_and_dont_battery_table

This is more specific to E-bikes and seems to clarify the situation to me....if the battery is done stick some charge in it to 20-60%, then fully charge it before each ride and get out on it asap -when it has cooled from the charging - which should minimise time at fully charged and sort out any balancing.....

https://www.electricbike.com/ebike-battery-longevity/
 

soundwave

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i have some fully charged Panasonic cells i use for my lights but have not used them for months now ill dig out the dvm and see what there at voltage wise 4.2v is full charge.
 
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scott gaza

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Oct 20, 2018
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You are doing the right thing m8 let the battery acclimatise/cool in you're man cave and put it on a timer charge 3-4 hrs when it has cooled its ready to be used again. HEAT is the main stress factor that a battery will not enjoy! I would how ever recommend a less powerful charger .
 

Nealh

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Charge it till you have 2 or 3 bars showing then leave it till the night before and do a full charge.
Battery won't go out of balance just because you do a partial charge before a full balance charge, balancing issues will only occur if you don't carry out full charges.
 
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Jon Matthews

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I'm going to throw in a curved ball here. I maybe or may not be correct and this is made on my experience with working with battery technology. If a manufacturer wanted to give a battery maximum life then the obvious way would be to let the BMS charge the battery to 80% only. What I'm saying here is when the display says its 100% charged it maybe only charged to 80% of it's capacity. Does that make sense?
 

Barrio Barranco

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Bosch claim 500 charges to 100% which tallies with this, so you could double the amount at 90% or triple at 80%....

screen-shot-2018-05-04-at-11-08-35-am.png
 

vfr400

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I'm going to throw in a curved ball here. I maybe or may not be correct and this is made on my experience with working with battery technology. If a manufacturer wanted to give a battery maximum life then the obvious way would be to let the BMS charge the battery to 80% only. What I'm saying here is when the display says its 100% charged it maybe only charged to 80% of it's capacity. Does that make sense?
Smart thinking, and it's sort of true. I guess that's partly how they arrived at 4.2v per cell as the charge level. In fact there are some cells that you can charge to 4.25v or higher, but I've never seen a BMS or charger exploiting that.

If I remember, the Battery University did their tests at 4.2v as 100%, though that was some time ago and might be invalid with today's cells.

There are so many unknows that I think it's just not worth worrying about. It could be a lot of messing about for nothing. Even if it was proved to lengthen cell life, there are so many other external factors that could still make it a waste of effort.
 
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soundwave

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well my 400w batt from 2014 that has always been used with a dongle has now lost about 30-40% of its original range which is imo not bad as i do hammer the crap out of them why decent cells are a must.

tho as jimmy can now recell these things i wont ever buy a new one but you need a working batt as you need the bms not to loose power while doing it why he charges more for a bosch batt.
 

Barrio Barranco

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Nov 24, 2018
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Yeah if I used mine just at weekends it should last 5 years, what advances will have happened by then this might end up my commuter bike and owning a new e-bike!!??
 

vfr400

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Bosch claim 500 charges to 100% which tallies with this, so you could double the amount at 90% or triple at 80%....

View attachment 29246
When was that test done and which cells were used? There are nany manufacturers and each has many different versions of lithium cells, plus, there are many different chemistries, electrode types and construction methods. You can prove anything if you pull the right data from the right tests and conveniently ignore the fata that conflicts with your theory. Have a look at this, which explains something similar to how that works.
 
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