to charge or not to charge? that is my question

[halflife]

I have seen people calculate the life of their batteries by taking the maximum range, say 20 miles, and then multiplying by the number of charge cycles quoted by the manufacture of the battery. 500x20= 10,000 for example

I was wondering, what about if you regularly do not discharge your battery? What then is the best way of getting the maximum mileage out of your battery?

I cycle about 9 miles to work every day and then 9 miles home. Both to and from work are within the range of a single charge, however I charge the battery when I get to work and then when I get home again.

Due to the battery companies quoting a number of charge cycles for a life of the battery, would I be better doing both journeys on a single charge. I am not concerned about the cost of the charge, only the life of the battery. The battery is Lithium Ion.

Thank you

Halflife

 

[Jeremy]

Battery cycle life is non-linearly dependent on depth of discharge, for pretty much all battery types. This means that what you're doing at the moment, partially discharging to less than 50% and recharging, will give you a significantly extended battery life.

Deep discharge is the one thing that seriously shortens battery life. The best example of this are the batteries in hybrid cars. They run shallow discharge cycles of around 30 to 40% maximum and get many tens of thousands of cycles from batteries that would probably struggle to do more than a few hundred cycles if deep discharged.

Jeremy

 

[Jones175]

Hi Jeremy
Does this also include NiMh batteries as well?
Because I'm also using about 50% of the charge of the battery

Regards
Andy

 

[Jeremy]

Yes, it does apply to NiMH batteries. Prius hybrid batteries are NiMH and have an 8 year, 100,000 mile warranty. 100,000 miles equates to a cycle life of well over 10,000 cycles, but the Prius only shallow cycles it's NiMH cells over a 30% to 40% discharge depth. The Prius also limits maximum charge to about 90%, again to extend life, although I'm not sure how significant this is for an ebike battery.

Jeremy

 

[halflife]

Thanks Jeremy

That answers my question great. I will continue to charge in work and at home (at least I only pay for 1/2 the electric )

I might invest in another charger so that I dont have to cart the one I have back and two.

Halflife

 

[Jones175]

Thanks Jeremy and to you Halflife for asking the question in the first place

Regards
Andy

 

[WALKERMAN]

Battery Charging

Battery cycle life is non-linearly dependent on depth of discharge, for pretty much all battery types. This means that what you're doing at the moment, partially discharging to less than 50% and recharging, will give you a significantly extended battery life.

Deep discharge is the one thing that seriously shortens battery life. The best example of this are the batteries in hybrid cars. They run shallow discharge cycles of around 30 to 40% maximum and get many tens of thousands of cycles from batteries that would probably struggle to do more than a few hundred cycles if deep discharged.

Jeremy

This re-charging business has been a bit of a mystery to me as I assummed it was necessary to try to run the battery right down before re-charging.
I have been doing 25 miles on my Pro Connect but there is still two lights lit-up when I need to do a recharge for the rest of the week travelling to work.
I was concerned that I may be shortening the battery life. So it seems I am O.K. doing the recharge at two lights?

 

[JohnInStockie]

This re-charging business has been a bit of a mystery to me as I assummed it was necessary to try to run the battery right down before re-charging.
I have been doing 25 miles on my Pro Connect but there is still two lights lit-up when I need to do a recharge for the rest of the week travelling to work.
I was concerned that I may be shortening the battery life. So it seems I am O.K. doing the recharge at two lights?

Thats about the same as me Walkerman, and based on what Jeremy and other experts advise, I think thats the best method.

John

 

[flecc]

I was concerned that I may be shortening the battery life. So it seems I am O.K. doing the recharge at two lights?

Once conditioned by one or two full charges and discharges, lithium batteries appreciate part charging for a long life, so what you are doing is fine.

Some industry expert advice with NiMh batteries has been to use the whole charge from time to time, about every 10 charges or so, which is different from the Toyota method Jeremy speaks of. I think much may depend on the cell quality in the respect, the cells in the Toyota being top quality Panasonic ones. Cheaper cells might benefit from occasional full use of the content.
.
.

 

[Jeremy]

The need for the occasional deep discharge with NiMH has more to do with cell balancing, making sure all cells are at the same state of charge, than anything else. It is probably a good idea with a bike NiMH pack, as Flecc says, because bike NiMH packs don't have any balancing circuits as a rule.

Lithium packs shouldn't need this treatment, as they pretty much have to have battery management systems (that perform cell balancing amongst other things) in order to work safely.

Older NiCd battery packs certainly need regular deep discharge, as they exhibit some critical failure modes (loss of apparent capacity and internal cell "whiskering") if only run over shallow cycles. I doubt that there are too many NiCd packs still around, which is a pity in some ways, as, despite their rather nasty environmental issues, NiCd cells could have a long life, have lower self-discharge than NiMH and withstand a fair amount of abuse.

Jeremy