My battery lost 1/3 of its capacity

[cwah]

Merry christmas all,

I have a 36V10A Li(NiCoMn)O2 battery purchased in september and was using it every day to commute (3 km*2 = 6 km/day). I was doing about 50 to 70 km/week.
So in 4 months I've done around 700-1000 km.


My bike uses around 12 wh/km. So for 1000 km I used 1000*12 = 12000Wh. My battery has 360wh, so I've used grossely 12000/360= 40 cycles of charge. Not much compared to the 1000 cycles told by Conhismotor.

But since the winter, I can't go that far and the voltage drop really quickly. From the 27 km distance I was able to reach initially I'm able to reach around 20 km now. It's 1/3 lower which a huge lost in such a short period of time!

I noticed another problem, sometime the battery cut for a short period of time when the voltage is lower. I don't know why, maybe it's a bad connection since I added a wattmeter?

I've heard that during winter batteries don't perform as well. When I go out, I park my bike outside for few hours and sometime the weather is really bad (very cold and raining). Maybe this is why the battery doesn't perform as well?

I don't know what to do, but this distance drop is huge. Would the capacity go back to normal on sunny days, or should I consider that's going to be permanent?

 

[flecc]

Obviously check your connections are ok first. However, capacity can drop considerably when the weather is cold, but it recovers when the warmer weather returns. Basically batteries are chemical devices and chemical reactions need heat to operate efficiently.

The cutout will probably be the low voltage when when the battery is fairly empty and the voltage dropping under load.

I can't say that's the whole of the loss since other factors could be present, you'll only know that when it's a bit warmer, but it's not necessarily a disaster at present.

 

[cwah]

Thanks Flecc. I'm not sure how to check the connection because everything seems fine when the battery is fine. So basically cables are connected, but how do I know when a cable is not well connected?

Just hope it's not going to be permanent.

 

[flecc]

If it's fine when the battery is fully charged the connections you've made should be ok. Don't worry too much about the battery, plenty of other members have too in winter but than found everything ok later when it's become warmer.

 

[tony6403]

If it's fine when the battery is fully charged the connections you've made should be ok. Don't worry too much about the battery, plenty of other members have too in winter but than found everything ok later when it's become warmer.

Thanks for this info. My battery (36v Li-ion bottle type) has been giving rise to concern to the point where I was considering buying a new one. Didn't really notice last winter as the two feet of snow meant that I didn't use the bike at all. I take it that simply keeping the battery in the house would effect improvements ?

 

[Oxygen Bicycles]

exactly, Lithium batteries don't really like when its cold and they are likely to have even 30% lower capacity. I'm sure soon summer cos back you'll notice better performance

all the best

Andrew

 

[Scottyf]

Best to keep the battery indoors or least somewhere warmer if you need the additional capacity. And only put it on the bike when it's in use.

 

[flecc]

Even if kept indoors, it will of course soon lose temperature when used for a while outdoors on a cold day, so range will still diminish from the usual.

 

[cwah]

I've noticed today that my battery needs rest to provide full capacity.

I was cycling today for 30 mn today and noticed that when I stop, the voltage was increasing slowly when not in use.

It seems that to have the full potential of the battery I have to leave it rest from time to time. Isn't that strange?

 

[flecc]

That's normal for lithium batteries cwah, especially after current drain has been quite high under load. The cell content chemically tires, but then recovers to full reaction when rested.

 

[DJH]

Best to keep the battery indoors or least somewhere warmer if you need the additional capacity. And only put it on the bike when it's in use.

This is what I have been doing with my 24v 10ah battery and recently when the temp. has been down to -5 or so I have managed my 17 mile/900ft of climb route ok. I was surprised to find I still had two greens showing on the battery on completion ( I suppose I was pedalling hard to keep warm!). I don't know what temperatures are generated by the battery in operation, perhaps if the battery is initially warm it helps it get to it's operating temp more easily - you experts out there will no doubt enlighten me?

 

[NRG]

Theres an element of self heating so if you start with a battery at room temp then it may not loose too much performance over your commute. Ultimately it will depend on how cold it is and how long its exposed to this cold temperature, wrapping or padding out a battery can help keep its performance for longer in cold temps but thats not so easy with a standard fit battery on a commercial bike...with DIY batteries its easier to achieve....

 

[cwah]

Thanks flecc, it seems that for my nicomn battery, drawing 1.2C is high current.

 

[flecc]

Thanks flecc, it seems that for my nicomn battery, drawing 1.2C is high current.

That does sound depressing! The first generations of manganese cathode batteries after the switch from cobalt did exhibit very marked chemical tiring, but most types have improved considerably since then.

Your consumption rate of 12Wh/km is a bit above average, a good rate is more like that per mile, but I think much of the chemical tiring is probably due to operating well below optimum temperature in current weather conditions. We need a warm spell to reveal if that's the case.

 

[Scottyf]

Get yourself on board with Lipo!
That way you can blow yourself up much quicker ;-)

 

[cwah]

Update on my battery today, I used it until low voltage cut-off:
- I used a total of 275wh with a weather of 10C in London.

So I have about 75% of battery total capacity. Still wondering if the capacity will be higher during summer at 25C.

 

[cwah]

My battery keep loosing its capacity.

I'm around 210-220wh max for a 360Wh battery (36V10AH)

So I only have about 60% of the battery total capacity after 6 months... Li(NiCoMn)O2 chemistry from conhismotor definitely doesn't worth it...

 

[RoadieRoger]

I have a 24V 8Ah battery on my Batribike Quartz Folder and on Saturday had to pedal the last 3 miles home after it failed on just under 20 miles of Medium assist riding .Admittedly the outward journey was into a stiff wind, but I would have thought that the return with a following wind would have compensated . The Lithium battery is 20 months old and initially would travel over 30 miles . I notice that hills , slopes and headwinds do take a toll now it is older . I will try and keep to low assist more to check the range , but this will require discipline on my part when confronted with a headwind . Too much effort and I will be better off riding a normal bike or taking the moped .