Wisper battery decline - how does it work?

[allen-uk]

I have a 2010 Wisper 905 with 36v14a battery.

So far it's done 7 months, and about 800 miles.

While it is obviously subjective, what seems to be happening is this. When I first rode the bike on full charge, certain local hills were easy. Now when I ride the bike on full charge, they are less easy.

I was anticipating that the battery would last 2 years or so, but hadn't really anticipated this sort of decline 25% of the way through its life.

Is what I'm describing normal? And if not is there any less subjective test (given that I haven't got access to any electrical kit).

Ta.

Allen.

 

[NRG]

Capacity normally declines over time and temperature has a very large affect on performance so jump to conclusions until you can test under similar conditions to when you first got the bike.

 

[allen-uk]

....temperature has a very large affect on performance

So would 20°C in July and 0°C in January account for the perceived difference in power?


A

 

[NRG]

Yep........

 

[allen-uk]

So, while we're on the subject, what DOES happen towards the end of a battery's life? Does it clap out, all of a sudden, need charging more often, fail to hold a charge, or what?

Ta.

A

 

[JuicyBike]

There will definately be a marked reduction in performance in cold weather and I would not doubt that a battery from Wisper will be anything other than top notch. That will be the reason: the cold weather.

You can test a battery capacity. Little rechargeables are easy to measure, larger ones take a bit of specialist kit which include some safe means of discharge, quickly.

I couldn't resist picking up a "battery analyser" for $100 on my recent trip to China (worth 5 times that and so far only sourced in California) and should have it here in 6 weeks. I wanted to check some batteries claimed to hold 17.5AH, which I have on good authority are in fact 16AH.

You should notice a fresh charge will be just as powerful in the bike using an old battery. But the older the battery becomes the sooner it will loose its charge.

You could of course measure the time it takes to charge your battery as a rough guide, but that would mean letting it run down completely, which is never advised.

 

[rog_london]

Just one thing Bob, so you're not too disappointed....

The capacity of a battery depends on many things, and one which you need to keep in mind is the discharge rate. Most batteries are quoted at the 10-hour rate, ("C/10") i.e. in the case of a 17.5Ah battery, if you discharge it at 1.75 amps, it should run for about ten hours. What if you discharge at the C rate? In theory it should last an hour, but even if it's in good condition you won't get anywhere near that - anything from 45 minutes down to half an hour would be quite normal.

It's a problem with ebikes, as we very often discharge at much more than the C/10 rate. What does make a huge difference is the quality of the battery. What is quoted in the ads is rarely born out in the real world, even though they're not actually lying to you!

What happens as the battery ages? One, the internal resistance rises, so you might find the bike cuts out on a steep hill even though the battery isn't flat. Two, it won't hold its charge so well - go for a ride with a freshly charged and ideally still warm battery and you'll get a (much) better result than if it's been standing around for a few days. Three, of course, you lose capacity anyway, and because you're pushing the active remainder of the battery more and more, the capacity drops progressively more rapidly.

Rog.

 

[flecc]

So, while we're on the subject, what DOES happen towards the end of a battery's life? Does it clap out, all of a sudden, need charging more often, fail to hold a charge, or what?

Ta.

A

The range starts to fall and therefore the period of weaker power that occurs as the battery empties starts to come in earlier.

With the more powerful motors like yours, a point is eventually reached when with the bike under high load as in steep hill climbing, the power will suddenly cut out. This happens when the battery output voltage under high load drops to below about 32 volts when the safety cutout operates to prevent battery cell damage.

If the hills that cause that are unavoidable, it's time to change the battery for a new one.

However, if you can avoid both the longer journeys and the steepest hills, you will be able to prolong the useful life. In the days of the very powerful original Torq 1 bike, it was very noticeable how much longer users in the flattish eastern counties could keep their batteries running, compared with those of us in the very hilly areas.
.

 

[NRG]

As long as the cells are of good or reasonable quality the 1 to 2c discharge rates of normal 'legal' spec bikes don't affect capacity that much if at all.

There are various discharge test curves you can Google and the ones I've seen show a <5% drop in capacity from 1c to 5c discharge rates with the 1c rate actually achieving slightly more than the stated capacity. So unless your are buying at the lower end of the market capacity reduction due to discharge rates isn't a problem in use.

 

[allen-uk]

The range starts to fall and therefore the period of weaker power that occurs as the battery empties starts to come in earlier.

If the hills that cause that are unavoidable, it's time to change the battery for a new one.
.

As it's only been 7 months and 800 miles (or so), then I'd hope that my current complaints are explained by the temperature rather than premature battery failure!

The other thing I'm noticing is that the battery will go from 100% power (4 lights) down to 50% (2 battery lights) in, say 15 miles, rather than the 25 miles that the same process took originally. Again, I'm banking that NRG's comments on temperature are the cause, as 'originally' was in July, and now it's zero degrees.

(The battery obviously didn't STAY at 4 lights originally, but the perceived power loss was certainly more gradual back in July. Now it is NOT gradual!)

Allen

 

[Wisper Bikes]

Hi Allen

It may simply be the temperature, however if the battery continues to cause problems, please contact your supplier, we can then get the battery tested and replaced if necessary.

Best regards

David

 

[allen-uk]

Thanks as ever David.

I'll wait till the weather gets warmer and just keep charging it for the meantime.


Allen.

 

[flecc]

I feel confident that it's temperature Allen, all battery performance suffers badly with low temperatures. If you have a car, look at the battery platform under the bonnet and in most models you'll see the platform is larger than necessary for the fitted battery. That's because larger batteries are specified to compensate for loss of performance when supply is to colder countries. We get sizes like 45/55 Ah, Northern colder countries get 60/80 Ah or even 100 Ah for example.
.

 

[allen-uk]

And having been out today (a heady 8+°C in NW London), yes, you were all right, it WAS the temperature.

Freshly charged battery gave quite amazing performance - I had to keep glancing down to make sure I was in 'middle' power rather than top.

And another lesson learnt.


Allen.

 

[Wisper Bikes]

Great news Allen.

All the best and dont forget to apply the factor 50!!

All the best

David

 

[Wisper Bikes]

I feel confident that it's temperature Allen, all battery performance suffers badly with low temperatures. If you have a car, look at the battery platform under the bonnet and in most models you'll see the platform is larger than necessary for the fitted battery.
.

Ahhh... so that's why, I had always wondered!

Thanks Tony, as always a mine of information!

Best regards

David

 

[michael sullivan]

Hi Allen

It may simply be the temperature, however if the battery continues to cause problems, please contact your supplier, we can then get the battery tested and replaced if necessary.

Best regards

David

Hi I have the same problem with the same bike I bought new last August we had the same cold weather here in South Ireland went out few times over Christmas and found I was down to two lights after 5 miles and was lucky to get home after 20 miles only 1 light left on controler . I done most of the pedeling myself .I was getting well over 30 miles when I got it first. I must say I am disapointed with it now for fear I will not be able to cycle home if I run out of battery power .I travel over mostly flat terrain no big hills .I will take it to the Irish suplier in CO.LIMERICK IRELAND when the weather gets better I kept the battery in warm room during winter. How much is a new battery Thanks

 

[Wisper Bikes]

Hi Michael

Sorry to read you have a problem.

Have you spoken to Marty in Limerick yet? If the battery has died we will replace it under warranty.

Regards

David

 

[michael sullivan]

Hi David I will take the bike to Marty in Limerick we had a few problems at the start with batries which I must say Marty was very good to me .I am waiting for the weather to pick up and I will try out the bike at Martys and he can try out the battery when I take it for spin at his place ,any thanks David .ps, is there a 15amp battrey comming out soon. Cheers

 

[Wisper Bikes]

Hi Micheal

OK I look forward to hearing from you.

I will PM you regarding 15Ah batteries.

Regards

David