Wisper 905se Sport Battery Life

[Tadpole]

I received a new Wisper 905se Sport on the 21/10/09. According to the documentation it was manufactured on 05/04/09 - nearly 7 months ago.
The battery would have been manufactured some time before this.

A new battery costs £515 and since these batteries have a finite life (not sure what as there are lots of guestimates around and it depends on this or that) I feel I am losing out. has anyone any thoughts on this?

 

[Blew it]

Welcome!

"Tadpole"

Welcome to the Pedelecs UK forum.

I fully understand your desire to get your money's worth from your battery....Good batteries don't come cheap!!.
If you are concerned about your battery, there is a way in which you can check it.

The easiest way to measure the actuall capacity of your battery, is to run it completely flat, and then recharge using a plug-in consumption meter such as THIS.

At 37 volts, the capacity of your battery should be 518 watt-hours, or, If you calculate the capacity at the nominal voltage of 36 volts, it will be 504 watt-hours.


In the meantime, you may find THIS POST reassuring.

Looking forward to hearing your first reports on your new machine...I don't think you'll be disappointed.

all the best
Bob

 

[OneWayTraffic]

I'd be interested in hearing from anyone who's had one of the 14AH wisper batteries for more than 2 years, and how it's stood up to the wear. We've heard plenty about Ezee after a year or so, and lots and lots about Wispers within a few months of purchase, but I don't think I've heard anyone give information about how much juice is left in the battery after 2 years of use.

 

[OneWayTraffic]

"Tadpole"

Welcome to the Pedelecs UK forum.

I fully understand your desire to get your money's worth from your battery....Good batteries don't come cheap!!.
If you are concerned about your battery, there is a way in which you can check it.

The easiest way to measure the actuall capacity of your battery, is to run it completely flat, and then recharge using a plug-in consumption meter such as THIS.

At 37 volts, the capacity of your battery should be 518 watt-hours, or, If you calculate the capacity at the nominal voltage of 36 volts, it will be 504 watt-hours.


In the meantime, you may find THIS POST reassuring.

Looking forward to hearing your first reports on your new machine...I don't think you'll be disappointed.

all the best
Bob

You're assuming 100% efficiency for the charger itself and the chemical process to charge the battery. I'm not sure what the efficiency is, but I'd guess roughly 75% or so.

 

[flecc]

I doubt the 14 Ah batteries have existed that long so there probably isn't any user two year experience. However, the life will be longer than the existing 10 Ah equivalents since the higher the capacity, the less a battery is stressed by any given motor. As for the chronological age when you received it, today's polymer batteries are less affected than the early non-polymer lithium types were by age decay. The chemical aging decay that remains comes into play more after the battery is conditioned and brought into use, so it's doubtful you'd detect much difference between your battery and one flown in from manufacture. I've just happily bought another make polymer battery that was used once a couple of months ago and was probably made early this year.
.

 

[OneWayTraffic]

So hopefully one would get a good 500 cycles without a substantial decrease in range over 3 years? That's 25,000km or so per battery if true.

As an aside Flecc, to what C rate would you wish to limit a discharge to in order to maximise life? 1C? Or less?

 

[Mussels]

So hopefully one would get a good 500 cycles without a substantial decrease in range over 3 years? That's 25,000km or so per battery if true.

As an aside Flecc, to what C rate would you wish to limit a discharge to in order to maximise life? 1C? Or less?

I've done about 20,000km over the last 15 months and not seen any deterioration in my 14ah battery yet. Saying that it may die in a couple of months but I'm not expecting it as it is only normally half used on each charge.

 

[Wisper Bikes]

Wisper battery 7 months old.

Hi Tadpole, I hope you have much enjoyment from your Wisper and thanks for your business.

The battery will have been topped up during the 7 months so since production, you will not have any problems.

All the best David

 

[flecc]

As an aside Flecc, to what C rate would you wish to limit a discharge to in order to maximise life? 1C? Or less?

1C is probably the lowest practical figure unless in very easy territory.

More important is the depth of discharge, the less is used the longer a battery lasts. For example, NiMh and lithium batteries used on satellites are used every 24 hours in the dark phase of their transit and then recharged by their solar cells in the light phase. They last for 10 years before the satellite is serviced or replaced, a battery life of over 3600 charges.

They are perfectly ordinary batteries, but the secret of their long life is that only about one seventh of their capacity is used daily before recharging. Of course that is impractical on an e-bike, but using a a very large battery or double batteries in parallel does extend the life quite a lot, hence my saying the 14 Ah Wisper battery will last longer than a 10 Ah for any given set of conditions.

The most ideal circumstance is using only a small part of the capacity in the middle of the capacity range, never using below 20% of capacity and never charging above 80% of capacity. This avoids stressing the cells and is called charge cycling, very appropriate in our case!
.

 

[Mussels]

Sorry for dragging up an old thread but I'm looking for a way to show how much capacity is left in my 2008 905se battery. I haven't noticed any loss of capacity but I guess there must have been some, how do I measure this?
I have a new battery I could compare it to, I guess I could use the power consumption meter as detailed above on both batteries and check the difference. Even that seems vague as the charging losses may exaggerate or understate the difference and I won't know which, then the different BMS may distort the findings. If I were to use this method then I'd need to find a way to run the battery down until the BMS shuts it off, I don't really want to ride it until it's flat or leave it running off the ground for hours.
I could buy a battery analyser but this seems a complicated and expensive way of doing it, I would also need a safe load to use that won't damage the battery.

Any ideas chap(esse)s?

 

[rog_london]

Sorry for dragging up an old thread but I'm looking for a way to show how much capacity is left in my 2008 905se battery. I haven't noticed any loss of capacity but I guess there must have been some, how do I measure this?
I have a new battery I could compare it to, I guess I could use the power consumption meter as detailed above on both batteries and check the difference. Even that seems vague as the charging losses may exaggerate or understate the difference and I won't know which, then the different BMS may distort the findings. If I were to use this method then I'd need to find a way to run the battery down until the BMS shuts it off, I don't really want to ride it until it's flat or leave it running off the ground for hours.
I could buy a battery analyser but this seems a complicated and expensive way of doing it, I would also need a safe load to use that won't damage the battery.

Any ideas chap(esse)s?

I'd have thought that would be a difficult and possibly meaningless exercise. The problems are to do with exactly what you normally do with your battery - how far you discharge it before recharging (journey length), how long after discharge before you recharge, how steep your hills are, how much effort you put in yourself, how fast you ride, whether you use lots of throttle and not least how many pies you eat (!)

You could arrange a full discharge under controlled conditions - i.e. through a suitable resistor - and time to cut-off, but this would not reflect normal use, and you'd get different results with different discharge rates, of course.

If you started off with a brand new battery and did a controlled discharge test this would act as a baseline for a further similar test after some use. I still don't know whether that would be useful though.

Are you really that curious? You'll find out soon enough when it's getting tired. I'd expect a slight increase in capacity to begin with and then some loss after that, but I wouldn't expect much loss in capacity for a good while, after which deterioration would be at an ever increasing rate due to over-use of the reducing capacity to do the same things you have always done.

One piece of information which never seems to be made available is the discharge rate required to achieve the rated capacity when new. I suspect a discharge current much less than that required by an e-bike would be used to obtain that value.

Rog.

 

[flecc]

You shouldn't do a full discharge using resistors, you could wreck your batteries since that method wouldn't have the safe 31.5 volt cutoff.

Running with the wheel off the ground to fully discharge a charged 14 Ah battery would take days, not hours. I ran a fairly empty battery on a powerful Torq like that for 8 hours and it made no noticeable difference. No-load consumption is negligible.

The only way to get practical and fairly accurate results is to ride both in the identical conditions/same route to cutoff. Static instrument checks will tell you nothing useful since the chemical state cannot be measured electrically, and dynamic instrument checks will not produce realistically comparable answers.
.

 

[rog_london]

You shouldn't do a full discharge using resistors, you could wreck your batteries since that method wouldn't have the safe 31.5 volt cutoff.


.

Ah, you may be right of course - some batteries would cut off by themselves depending on the BMS fitted, whereas others depend on the controller to do that.....

Rog.

 

[Mussels]

I'd have thought that would be a difficult and possibly meaningless exercise. The problems are to do with exactly what you normally do with your battery - how far you discharge it before recharging (journey length), how long after discharge before you recharge, how steep your hills are, how much effort you put in yourself, how fast you ride, whether you use lots of throttle and not least how many pies you eat (!)

I'm selling my 905 and I'd like to say to a buyer that x test produces y results, it gives them something to go on rather than some bloke off the interweb says it's good. I'm not expecting a great answer but maybe something that can reduce the uncertainty.

The only way to get practical and fairly accurate results is to ride both in the identical conditions/same route to cutoff. Static instrument checks will tell you nothing useful since the chemical state cannot be measured electrically, and dynamic instrument checks will not produce realistically comparable answers.
.

I can't even do that as the batteries have different connections.

 

[NRG]

You would need to perform a full charge / discharge / charge routine with the last charge routine monitored to see how much charge goes into the battery, then you'll know it's current maximum capacity.

 

[flecc]

You would need to perform a full charge / discharge / charge routine with the last charge routine monitored to see how much charge goes into the battery, then you'll know it's current maximum capacity.

But you need to deduct something according to the charger efficiency, typically around 15% to be deducted, but guesswork so still far from certain.

The other problem with battery comparison is usefulness of the capacity. Actual dynamic capacity depends on the discharge rate and cell health, older cells don't hold up under high discharge as well as new ones.
.