Question on partial charging

Barry Heaven

Pedelecer
Sep 19, 2009
162
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Knowing how fussy Lithium batteries are I have always assumed that it is best to fully charge a battery. Occasionally it would be useful to do a quick top-up rather than wait for the full 3 to 5 hour charging cycle to complete.

Does anyone know or have any experience in using partial charges? Would it harm the battery in the short or long term? My bike is a Kalkhoff Pro Connect with a Panasonic battery.
 

flecc

Member
Oct 25, 2006
50,496
28,373
Opposite way round Barry. Once a new lithium battery has been fully emptied and recharged twice to condition it, all further charges should be partial for longest life.

That doesn't mean charging after a couple of minutes use of course, but recharging after using a quarter to a half the content is much better than fully discharging always which stresses the cells.
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lemmy

Esteemed Pedelecer
I notice that for maximum life on the batteries or electric cars, they are charged to 80% and then run down to 20% and some makers guarantee the units for 10 years so that must be ideal.

On the other hand, for an electric bike you'd really always want to charge to max. Flecc recommended not charging until at least two of the lights on the battery were extinguished.

I've had my Tasman for nine months now in more or less daily use for trips of varying length from a couple of miles return to 40 miles return. I decided at the outset that whatever the effect on the battery, the bike was my slave, not me its, so I'd charge and discharge it according to my needs rather than the battery's.

Even so, generally don't charge the battery until 2 lights are out but If I have a long trip to do I charge it to full regardless. After 8 months, the battery still shows full charge capacity and still goes the same distance for any given state of discharge. So, no damage done so far.

Flecc, fount of all wisdom, will probably reply - but I have a policy of regurgitating his words before he has a chance in order to usurp his guru status and make myself rich :D
 

flecc

Member
Oct 25, 2006
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I decided at the outset that whatever the effect on the battery, the bike was my slave, not me its, so I'd charge and discharge it according to my needs rather than the battery's.
I do this too, and use them to the full likewise, but it's a rich man's policy, as shown by my once finishing off three lithium batteries within 16 months. "Only" £250 each at the time though. :eek:
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Barry Heaven

Pedelecer
Sep 19, 2009
162
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Opposite way round Barry. Once a new lithium battery has been fully emptied and recharged twice to condition it, all further charges should be partial for longest life.

That doesn't mean charging after a couple of minutes use of course, but recharging after using a quarter to a half the content is much better than fully discharging always which stresses the cells.
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Thanks Flecc. I didn't put my question very well. I am thinking about a situation where I visit somewhere and do a quick top-up charge to extend the range but don't have the time to wait the 3 or so hours for the battery to fully complete charging, e.g. may charge from say 2 lights to only 4, i.e. the charger doesn't go though the whole process until all the lights extinguish.
 

flecc

Member
Oct 25, 2006
50,496
28,373
That's fine, it won't seriously harm a lithium battery. They are rather like the lead acid batteries in our cars in this respect, and they last four or more years of constant topping up while the engine is running.

In fact not having time to complete the charge is ideal, since it means the battery is operating in the central charge state zone between about 20% and 80% of charge which is ideal for longest life.

It's the two ends that damage most, the last stages of emptying and the last stages of filling, both extremes maximising the stress on the chemical content of the cells.
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Barry Heaven

Pedelecer
Sep 19, 2009
162
0
That's fine, it won't seriously harm a lithium battery. They are rather like the lead acid batteries in our cars in this respect, and they last four or more years of constant topping up while the engine is running.

In fact not having time to complete the charge is ideal, since it means the battery is operating in the central charge state zone between about 20% and 80% of charge which is ideal for longest life.

It's the two ends that damage most, the last stages of emptying and the last stages of filling, both extremes maximising the stress on the chemical content of the cells.
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Thanks again Flecc. These batteries really do like to be fussed over but, as Lemmy and you have said, you can't let them rule your life!:D
 

flecc

Member
Oct 25, 2006
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Thanks again Flecc. These batteries really do like to be fussed over but, as Lemmy and you have said, you can't let them rule your life!:D
In a sense perhaps, but in practice they are the least fussy of all, part charging anytime is really ideal for all round usage, plus they are light.

Previous types could be far more fussy and awkward. NiCad had to be fully discharged because of memory effect and had much lower capacity and range. NiMh were a bit heavier than NiCad and had to be fully discharged occasionally since they too could suffer the odd ill effects of constant part charging. And paste electrolyte lead acid (SLA) were just far too heavy, didn't last very long and couldn't give up much more than half their capacity because of the peukert effect.

Against that lot lithium is very welcome now it's reliable, though lower prices would be helpful.
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tillson

Esteemed Pedelecer
May 29, 2008
5,145
3,003
I only use my bike to get to and from work, which is about 10 miles each way. I always charge the battery when I arrive home, after 20 miles, and these days it is well into the final flashing LED stage.

It wouldn't really cause me any inconvenience to partially charge my battery (Panasonic Crank system) at each end of commute. (ie do ten mile and then partially charge). Would there be any advantage to keeping the charge level in the battery between, say, 2 and 4 LEDs illuminated by employing a system of partial charging and discharging? As I say, this wouldn't cause me any difficulty, but if the benefits are minimal it probably isn't worth it. Any opinions?
 

flecc

Member
Oct 25, 2006
50,496
28,373
Is there any realistic prospect of this, do you think?
I think lower prices will come with time, but it should be remembered that a major part of today's prices on imported goods is the very unfavourable exchange rate situation since we got ourselves into an economic mess.

If the present government's cutbacks and repayment of international debts go ahead according to their four year schedule, we can look forward to gradually reducing prices once and if it's seen that the policies are beginning to work, maybe from two years time onwards.
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flecc

Member
Oct 25, 2006
50,496
28,373
I only use my bike to get to and from work, which is about 10 miles each way. I always charge the battery when I arrive home, after 20 miles, and these days it is well into the final flashing LED stage.

It wouldn't really cause me any inconvenience to partially charge my battery (Panasonic Crank system) at each end of commute. (ie do ten mile and then partially charge). Would there be any advantage to keeping the charge level in the battery between, say, 2 and 4 LEDs illuminated by employing a system of partial charging and discharging? As I say, this wouldn't cause me any difficulty, but if the benefits are minimal it probably isn't worth it. Any opinions?
I doubt the benefits are very large with a good quality battery and I would just use as you are until the range gets just short of the whole day, then switch to each end charging. You will then get the slight gain from that second half of life part charging with the minimum of inconvenience overall.
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