Battery care

[rigel]

As a new ebike owner and having done some research it seems the weak point is clearly the life of the battery.

It's always accepted that you can only charge & discharge a rechargeable a finite number of times. Whilst it is hardly surprising that time is also a life factor I have read articles stating that time will impact regardless of how many charges are made.

I have a 36v 16ah which will/should give a range of 50 - 60 miles, far more than I am ever likely to do on a single trip.

Am I right is saying that in order to prolong battery life I should charge it often and not let it run down. If so is there any 'cut off' point that is best, e.g. 75% charge left, or would repeatedly charging a well charged battery damge it?

Also if time is a factor, how do you know how old the battery is when you buy the bike. I bought a 2010 model at a discount but upgraded the battery to a 16ah which certainly looks new but it could have sat on the shelf for some time.

Sorry if I appear clueless ---- I know loads about petrol engines but this is all new!

 

[flecc]

Definitely charge often, though it's best to use a reasonable proportion like a quarter of the capacity and not charge every tiny bit used like a short trip to a shop at the end the road for example.

For best life avoid the extremes of charge, discharge to empty or the last stage of charge to full, since these cause the greatest chemical stress. Stopping charge about 20% short of full is ideal, but even avoiding the top 10% is well worth it. Of course this can be difficult to judge over time unless the batterey has at least 5 LED charge content indicators.

The rate of discharge also affects the life, but with a 16 Ah battery that should not have a severe effect.

 

[rigel]

Thanks flecc

I note your comment about not charging fully --- my battery has 3 lights on it so as you say it may be difficult to judge.

From what you say it seems that 'partial' charges don't harm the battery at all and in fact may well be beneficial in prolonging life, so I'll bear that in mind.

Thanks again

 

[gerryscott]

sorry flecc,what do you mean don't charge to full? I just charge mine till the green light comes on.

 

[NRG]

Often the cells are balanced at the end of charge so continually not charging to full may lead to a pack with unbalanced cells. If adopting a short charge scheme it's advisable to complete a full charge say every ten short charges or so....

 

[indalo]

If adopting a short charge scheme it's advisable to complete a full charge say every ten short charges or so....

NRG's model is what I use on my laptop batteries, (4 of them!) and it has served me very well although the demands are a little different from those required of bike batteries.

Regards,
Indalo

 

[lemmy]

It seems to me that the battery is my servant, not me its'.

Therefore I charge it when I want, sometimes after going a couple of miles in the morning and then finding I want to do a maximum range journey the same afternoon, others running the battery down to cut-out point.

So far, from a new range of 27 miles stop start in London, I'm down to 24 miles after 18 months so any harm I'm doing to the battery is fine by me. If it lasts 2 years I'll be happy (warranted for 60% capacity after 2 years, I reckon mine will be at worst 80%), if it lasts 3 years and still does 20 miles, I'll be delighted, buy an 18ah job and keep the other as a touring spare.

 

[flecc]

sorry flecc,what do you mean don't charge to full? I just charge mine till the green light comes on.

That's full Gerry. The manufacturer will have made a small allowance at the top end, but the last stages of charge stress the cells most. If your battery doesn't have five LED indications of charge, just carry on as you are, the gains from short charging aren't huge. I'm with Lemmy on this, I just use my batteries to the full and buy new ones when necessary.