Charging

[baboon]

Hi all,

My pro connect range has fallen quite significantly since I changed to an 18t pinion; generally by the end of my 18 mile round trip commute I am down to a single light on the battery.

Question is, is it worth getting hold of an extra charger so that I can charge at both ends? Would this significantly increase battery life?

Does anyone know whether one can order extra chargers and if so how much they cost? I will ask 50cycles tomorrow if I remember but just thought someone else might be able to give me a clue.

Thanks

Peter

 

[flecc]

Better to just use the battery to almost empty on these Peter, the management system limiting loss of life resulting from that. A second charger would be an expensive option, since it would prolong battery life very little.
.

 

[baboon]

Thanks flecc.

That surprises me. I thought that lots of half charges would be better than a few full charges. That's how I thought it worked with mobile phones, anyway; perhaps they're a bit different?

Peter

 

[lectureral]

Yes - I'd like some guidance here too (if you don't mind Flecc) - I was told by the dealer that it was better to charge infrequently because the battery has a limited number of charges in it - so better to make them big ones - but I gathered from here that charging more often was better. Are we saying it does not really matter which policy we adopt (I have also heard that charging anywhere between 80 and 20% was fine)?

 

[flecc]

The rule is that frequent charging at every opportunity is best for long life on Lithium rechargeable batteries, and part charges do not equal full charges, the total of charge time is relevant.

However, the extra life gained from frequent part charging is unlikely to make an expensive additional charger worthwhile if the purchase of that can be avoided, and that's particularly true on a system with top class battery management during usage and charging. The Panasonic is one such system.
.

 

[john]

There is a fine line in all chemistries between charging to maximum capacity and overcharging. This is decided by the manufactured when designing their charger and BMS and there will be some differences in where the line has been drawn by different manufactures.

Given that, I would add to what Flecc has said by saying that if the battery has only been discharged a little (say 10%) it might be better not to recharge if you only want to use say another 10%. The aim being to minimise the number of "full charge" and "full discharge" conditions. Don't ask me how big a difference this makes, it's probably quite small. (NB This probably doesn't apply to SLA that like to be kept fully charged)

 

[Jeremy]

I think Flecc is probably right with regard to the economics of it, although depth of discharge does very significantly affect cycle life.

For most lithium chemistries, plus NiMH (but not NiCd), shallow cycling very significantly increases cycle life. The effect is non-linear, in that if a 100% to 10% charge/discharge regime is exchanged for a 90% to 30% charge/discharge regime cycle life will improve by at least an order of magnitude, maybe more. NiMH cells run under the latter regime can quite easily achieve a cycle life up in the tens of thousands of cycles, and even LiFePO4 cells seem able to get up to 5000 cycles or more when run in this way.

The difficulty is with accurately controlling charge level, rather than discharge level, much as John has alluded. To get the absolute maximum cycle life then charging to the maximum level has to be limited as well as the discharge point.

Lithium cells (of all types) are generally easier to charge limit, as they ideally need a constant current/constant voltage charge regime. To charge them fully to 100% requires a fairly lengthy portion of the charge cycle at the constant voltage phase. Cutting the charge off shortly after the cells reach the transition voltage from the constant current to constant voltage stage will limit charge to around 90%, depending on the selected cell transition voltage. The problem with this approach is that it really requires individual cell charging, as without it the cells will go out of balance. The battery management system built in to a lithium pack relies on the constant voltage phase to equalise charge in each cell, usually by shunting excess charge current around the more highly charged cells in the pack.

Given that calendar life may well be more of a practical limit than cycle life for many of us, I think you'd be well advised to just continue with the deep discharge regime. It may be that, as range drops with cell ageing you have to look again at an alternative option, such as getting another charger, at some future time.

Jeremy

 

[baboon]

Thanks for the useful input everyone.

Peter

 

[prState]

A couple things that might help you get better range without slowing you down:

I would keep it in a low power mode just to keep from accidentally activating it, when you don't really benefit that much. You can always flip it into high power mode at any time.

I don't know about your traffic situation there, but here when I'm on a road with several traffic signals there's no use at all racing madly only having to pull up abruptly. You can travel as fast or possibly faster by keeping an eye on your next potential stop. Any time you don't have to kill your momentum, is a bonus. Unlike when I drive my car, I don't really have the same option to calibrate my speed (other cars on my tail end) or speed limits, but a bike you can take advantage of this. (unless you're packed in between cars)

Check your tires more often if you're keeping an optimum high pressure. Even in my brand new tires and tubes that high pressure seems to fall off in as little as 4 days. I have a foot pump with a built in gauge right next to my bike at home, so it only takes a few seconds to check. Once you establish how fast you're losing pressure you can gauge a top up automatically.