Comparison of Battery Characteristics

[ITSPETEINIT]

I have been thinking how difficult it is to form a conclusion as to which
type/size (Ah/Voltage) of battery would best suit one's purpose not only for would be e-bikers but also for those who wondered why they chose the type of battery they did when they bought their e-bike (particularly if there was a choice).

Of course the information imparted by such a survey would be subjective and determined by the type of use that the owner had put their bike to and that could be compared with(to) the manufacturer's information (where it is transparent).

The categories of character I had in mind (but the list is not exhaustive) are:

Number of Type of Batteries in use (subscribers to this forum)
Type of battery: Lead Acid/NiMH/Lithium (of which there are some sub-types)
Safety factors. (spontaneous combustion, etc)
For each capacity/type: Range according to type of terrain (Hilly/Average/Flat - perhaps defined.
For each capacity/type: Effect on Speed - on the flat/up hill (various grades).
Number of recharge cycles expected.
Useful Life of chemical content depending upon use (heavy, moderate/light - as defined for this purpose) showing decline in Range/speed with time/use.
Failure rate as experienced where it fell short of expectation from published specifications.
The economics of low Ah batteries (eg 7Ah), compared with higher Ah batteries (eg 13Ah or more if available)
Price factor(according to manufacturers/suppliers)
Availabilty of replacement batteries.
Recelling feasibility
Weight
Charge Time
Memory effect (Yes/No)
Relative Efficiency (Amps/Kg)

As I have said, the opinions given in the survey will be subjective, but across the spectrum of users, and compared with manufacturers' published characteristics, the results would be useful.

This is a lot of work especially for those with specialized knowledge of the subject. But there has been a lot of publication of e-bikers perceptions of how their bikes and their BATTERIES have performed which could usefully be drawn together in one location.

It goes without saying that everyone should feel free to post his opinion of what this survey should cover.

Peter

 

[flecc]

I think much of the information is already available Peter. There's a summary of what type to choose on this site, according to usage, and also other articles on the characteristics.

The Battery University website is an excellent and reliable source for those who wish to delve much deeper into the behaviour, life etc of the various types.

My own views and experience in answer to the questions is as follows:

Type of battery: My preference is NiMh at present. Lead Acid too heavy, Li-ion types have either safety or performance limitations, particularly when stressed as in steep or sustained hill climbing. NiMh are only a little heavier than Li-ion, much lighter than lead acid and always do the job without fail.

Safety factors: Cobalt based Li-ion can suffer spontaneous ignition failure. Both other types are quite safe.

Range: No true answer can be given due to what size is fitted. A large lead acid as in the Powabyke gives an very good range. However, in a size for size context, the lead acid is out. Li-ion gives the better range in flat country where the battery isn't stressed, but in hilly terrain that drops to the same as NiMh, as shown by two of my bikes with two different motors using the two battery types.

Effect on speed: Terrain makes no difference, only voltage affects speed on hub motor bikes, higher voltage = higher speed. The eZee Li-ion (37 volt) is a little faster than the NiMh (36 volt), by exactly that proportional difference, i.e. very small. The US Batteryspace company markets 39.6 volt NiMh packs as substitutes for 36 volt packs for those wanting to boost their speed.

Number of recharge cycles: I always ignore this since the differences in usage seriously affect the outcome. Any given number can be worthless, and lifetime experience is a better indicator. Mine and other experiences is that NiMh is the clear leader here, Li-ion due to capacity loss lasting no longer than lead acid in traction use, circa 18 months, but depending on usage and care. To show how impossible it is to be categoric though, much depends on the range necessary. Someone who's individual trips are always less than 4 miles for shopping etc can go on with a battery for years until it's range has dropped to that. A commuter doing 15/20 miles each way might find one battery type impossibly inconvenient to use after a little over a year.

Useful life of chemical content is the same thing as range, since speed is barely affected. Voltage doesn't change appreciably with age, just capacity.

Failure rate: Much depends on charger quality, especially with NiMh. Assuming a good charger, Li-ion is the only type I've known to display premature failure, especially the newer formulations.

Economics: The larger capacity sizes are almost always the more economical, the one exception being for new introductions. For example, an NiMh using 8 Ah cells cheap, but one using the newest 10 Ah cells dear for the moment until they become common.

Price: Lead acid the winner despite a somewhat short life, but well looked after NiMh can run a close second. Li-ion well behind, being much more expensive due to both initial cost and shorter than NiMh life.

Availability: Li-ion are usually bike specific so are likely to become the most prone to unavailability. Even lead acid has been hit by non-availability now, since one battery size is no longer manufactured and there are bikes on sale now with packs that can never have the content replaced, Beware! Again NiMh is the clear winner, since they can be re-celled and the only other technical content is an easily replaced and very cheap Thermistor. One factor can affect all three types though, if one is unlucky enough to break a case, that's generally not available separately and could be discontinued.

Re-celling: As above, only NiMh can be recelled. In theory this could arrive for Li-ion, but with the diverse types and the safety implications, it's unlikely.
.

 

[ITSPETEINIT]

In answer to Flecc's immediate response

To say "my ink was hardly dry" is an understatement.

What you have said Flecc, and so consisely, is what I was looking for. It may only be one user's/expert's opinion but with the LINK it puts most if not all of the answers to the questions that were in the mind of the reader (and mine), and a few that were not IN ONE PLACE.
Other subscribers' experiences could be appended perhaps.

It could perhaps be re-iterated under "F.A.Q's" - One button gets you all (?) the answers. (someone will probably tell me it already is)
If I leave this reply to find out, I shall probably lose this work, as I already did once this morning.
Peter
PS do you 'copy and paste' these informative postings from other material in
your keeping?

 

[ITSPETEINIT]

My Battery requirements Revealed.

Looking at your 'precisely what I was looking for' reply again, I have concluded that with a little lateral thinking I really need two batteries for the best economics and life.

Firstly, the Li-ion one I have already which, fault or not, is already showing sign of decrepitude after 400 miles (hopefully I may be proved wrong) - I can use this for shopping (five miles each way) which is a relatively flat journey.

Secondly, a NiMH one which will serve my purposes better for more extended trips into the country which may well have some serious hills which have been perceived from behind the wheel of a car as fairly flat and the trip to the Doctor in Shaftesbury (9 miles each way) up a 10% hill which is my nemesis. A sufficiently energetic ride to put alarm into my BP readings.

Of course an NiMH battery will require a different charger (that's right isn't it?). A little more expense but it is range that is my number one priority rather than cost. Just had a thought: I could take both with me on the 'Tours' to save that muscle burning ride home when the capacity of one is exceeded. Another 5Kg (more or less). It's a pity that a 10Ah battery has such large dimensions - it's not an easy or comfortable fit in either my panniers or on my pannier rack.
Peter
I thought that was brilliant connecting another battery into the circuit of a Twist - but where was the battery? Presumably in a pannier. (I shall lose this if I take a diversion to that site). Was it a plug-in connection at the battery end or hardwired?

 

[flecc]

I do have a file of "copy and paste" items Peter, and that's still growing but little used. My contribution above was typed afresh "off the top of my head", answering point by point.

I use the two battery method, Li-ion and NiMh, using them according to need. Short journeys ideal for Li-ion which can immediately be recharged with advantage, longer and particularly hilly journeys with NiMh.

Yes, NiMh do need a second charger since they have to "read" from the thermistor in the battery to determine the way in which the charge progresses and terminates. One big advantage with a second battery with the eZee NiMh charger is the discharging. Their charger has no discharge function, but for health and long life, an NiMh should be quite fully discharged from time to time. With a spare battery, it's easy to ride the NiMh until it runs out and swap into the Li-ion to return home for charging.

I sometimes carry a second battery diagonally upright in one of my large panniers, and have carried two spares in the two panniers on two long journey occasions.

Yes, "Grandad" did carry the spare Powacycle battery in a pannier, but they only weigh about 3.5 kilos against the 5.4 kilo 36 volt eZee one. The Powacycle battery uses strip contact sockets like the eZee ones, but much thinner. I daresay "Grandad" was using some appropriate strip plug in contacts. There's now a handy link to his tip on the Tips page of my Twist site, which in turn is linked to from my Torq Talk site home page.
.

 

[Mike Robinson]

I have a Nimh battery - so what's the best way of charging / using this type of battery?

So far I just charge it up when I get back from a ride. I understand you should fully discharge it once a month but no idea why. How do I do this this though? There isn't a switch on the charger but I have gone for a few longer rides (20 mile). I don't fancy getting caught out with no power at all a long way from home. Maybe I should pay my son to sit on the bike and just hold the throttle open for an hour or two. Would I harm the battery by leaving it plugged in overnight?

People mention treating their batteries correctly but rarely mention any details as to what's correct and what's not.

Mike

 

[flecc]

You've basically summed it up Mike. Use the battery and charge afterwards, but occasionally empty it and then recharge. Many chargers have a discharge function, sometimes called refresh, to do this for you when you ask it to.

The reason for this is to avoid loss of capacity. The earlier NiCad types suffered from Memory Effect, a phenomenon which made the battery remember the point at which the last charge began, and then not allow discharge below that point. Therefore it was important that they were fully discharged every time.

When NiMh took their place, the hype had it that memory effect was a thing of the past, but in fact that wasn't wholly true, NiMh can suffer to a limited extent. Hence the need to occasionally fully discharge to avoid loss of capacity. Perversely, NiMh musn't be completely flattened since that wrecks them, but discharging on the bike or with a suitable discharging charger cuts out before the damage point.

My advice is to try and find the range by trial and error and every 10 charges run it close to that point with repeated journeys but without stranding yourself. Then you can indeed run the motor with the bike wheel off the ground or the bike inverted until cutout. The snag is it takes many hours, since when spinning without a load the consumption is minimal. Í ran an eZee battery very low by riding, and it still took more than seven hours spinning to bring it to cutout!

Since that's a lot of bother, just running on the road to below three quarters charge every ten or so charges is probably a sensible compromise.
.

 

[Mike Robinson]

I'm a bit confused but then I've just come back from the pub.

NiMh can suffer to a limited extent. Hence the need to occasionally fully discharge to avoid loss of capacity.

Perversely, NiMh mustn't be completely flattened since that wrecks them

So should I completely discharge them or not?

Mike

 

[allotmenteer]

I'm a bit confused but then I've just come back from the pub.

NiMh can suffer to a limited extent. Hence the need to occasionally fully discharge to avoid loss of capacity.

Perversely, NiMh mustn't be completely flattened since that wrecks them

So should I completely discharge them or not?

Mike

I believe this means that you should never over-discharge Nimh below about 1V per cell otherwise they are ruined. Discharging them on the bike (or with a suitable charger) will discharge them to a safe level but will stop short of a damaging level of discharge.

 

[flecc]

Yes, as allotmenteer said Mike, and as I said at the foot of the post, chargers and bikes don't make that mistake.

My mention that they should not be over discharged was a warning to all not to try ad hoc methods of discharging such as with vehicle light bulbs or resistors, since that could wreck them, by going below 1 volt per cell.
.

 

[electric.mike]

Availability: Li-ion are usually bike specific so are likely to become the most prone to unavailability. Even lead acid has been hit by non-availability now, since one battery size is no longer manufactured and there are bikes on sale now with packs that can never have the content replaced, Beware! Again NiMh is the clear winner, since they can be re-celled and the only other technical content is an easily replaced and very cheap Thermistor. One factor can affect all three types though, if one is unlucky enough to break a case, that's generally not available separately and could be discontinued.

flecc out of interest if i have bought a bike (powabyke)or have i allready? which sla batteries became unobtainable for, considering the size of my battery case, would i be able to get a nimh pack put together complete with charger, to match the energy reserve i now have 36v14ah or even improve on it.
mike
ps i am trying to learn from the battery posts on here.

 

[Baboonking]

flecc out of interest if i have bought a bike (powabyke)or have i allready? which sla batteries became unobtainable for, considering the size of my battery case, would i be able to get a nimh pack put together complete with charger, to match the energy reserve i now have 36v14ah or even improve on it.
mike
ps i am trying to learn from the battery posts on here.

Mike,

I've recently got a couple of powabykes and will be replacing the battery packs with nimh. I'll post up my experiences when I do. I'll probably build my own batteries from individual cells but any of the 36 volt packs sold here should work (providing they fit) Ebikes.ca store. Bear in mind that 14AH sla is equivalent energy to 9 or 10AH nimh.

 

[flecc]

Hello Mike

No problem with availability of the units which Powabyke use you'll be pleased to know. The problem is specific to some Urban Mover models, due to them having 36 volt batteries with three 12 volt SLAs inside which haven't been a popular size. In consequence, those SLAs are no longer made, so once a pack is finished, the owner is stuck.

Regrettably, electricbikesales are still selling these models at £499 last time I looked, while telling existing owners there's no more batteries. I'll refrain from further comment.

I think Powabyke already make NiMh batteries for many of their models, so you have no problem either way, you can carry on with SLA or upgrade at a higher price to NiMh.
.

 

[Baboonking]

Hello Mike



I think Powabyke already make NiMh batteries for many of their models, so you have no problem either way, you can carry on with SLA or upgrade at a higher price to NiMh.
.

I think they''ve skipped nimh and gone straight to lithium see Powabyke :: Powabyke Electric Bikes

I'd be interested to hear otherwise

 

[electric.mike]

flecc urban mover need to be very careful, the sale of goods act can be a very powerful tool if used properly,(upto 6 years) and even after a couple of years of use i would have thought a court would not have expected`an electric bike to be unusable.


Baboonking yes its lithium so i thought let everybody but me be the test,i will maybe get on that bandwagon a lot later.
mike

 

[flecc]

I think they''ve skipped nimh and gone straight to lithium see Powabyke :: Powabyke Electric Bikes

I'd be interested to hear otherwise

Thanks for the update. I last looked as they talking about NiMh, and I await with interest what sort and size of Lithium they use with their motors which peak at 700 watts. For Li-ion to deliver the 20 amps, they'll need a big battery and possibly cobalt based. The eZee 10 Ah manganese based Li-ion is at it's limit at around 16 amps.

The market is going to be interesting now they've got alloy frames, modern batteries and a weight of 28 kilos. Powabykes can no longer be called tanks it seems!
.

 

[Baboonking]

and I await with interest what sort and size of Lithium they use with their motors which peak at 700 watts.

.

Interesting to hear that. I guessed the peak must be quite high as they do seem to have quite a lot of torque. I'm just hooking up a braindrain to test the stock figures now. Soon as i've done this it will be modification time