Do I need cyclic batteries?

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newtrikebuilder
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Do I need cyclic batteries?

Postby newtrikebuilder » Sun May 02, 2010 9:49 pm

I'm considering building an etrike at the moment, but things are starting to look expensive. I've found some cheap lead acid batteries, but they aren't cyclic. Cyclic ones cost roughly double and they don't have enough capacity. What will happen these lead acid batteries, will they die within a few hours of use, or should can I expect a few thousand miles from them? Are there many people using normal lead acid batteries in electric vehicles?

The battery I'm looking at is 100Ah, with 850 S.A.E cold start. So I'm guess that it should cope a bit better than the lower capacity ones. If these are no good then I think the project is going to be too expensive.

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ChrisB
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Re: Do I need cyclic batteries?

Postby ChrisB » Sun May 02, 2010 10:05 pm

Hi NTB and welcome to the BVS forums

To be honest you need to spend as MUCH as possible on your batteries, DO NOT USE normal car battery types, you'll be lucky to get 20-30 cycles out of them.
Leisure batteries will fair better but wont like the heavy current drain, dual purpose ones like marine types are slightly better as they are happier to supply high cuurrents and will also be happier being cycled but are only a halfway house.

Some people are saying the "elecsol" brand are now better but I've yet to see any results from their improved batteries :|

Batteries are the key to electric vehicles, use decent batteries and reap the rewards, use low spec/incorrect batteries will frustrate you and make the project end up with poor range.

What voltage will the Trike be running ??

ChrisB
I reject reality and substitute my own !!!!!!

newtrikebuilder
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Re: Do I need cyclic batteries?

Postby newtrikebuilder » Mon May 03, 2010 8:14 am

ChrisB wrote:Hi NTB and welcome to the BVS forums

To be honest you need to spend as MUCH as possible on your batteries, DO NOT USE normal car battery types, you'll be lucky to get 20-30 cycles out of them.
Leisure batteries will fair better but wont like the heavy current drain, dual purpose ones like marine types are slightly better as they are happier to supply high cuurrents and will also be happier being cycled but are only a halfway house.

Some people are saying the "elecsol" brand are now better but I've yet to see any results from their improved batteries :|

Batteries are the key to electric vehicles, use decent batteries and reap the rewards, use low spec/incorrect batteries will frustrate you and make the project end up with poor range.

What voltage will the Trike be running ??

ChrisB


I need to keep build costs down really. At the moment I'm not sure how much I will use the vehicle, and with the amount that I will use it, it will cost me a lot per mile.

I've found some marine batteries which are a similar price, but 90Ah instead of 100Ah. This should be enough though.

I have also seen some AGM (Absorbent Glass Mat) batteries. Does anybody know about these? They claim to have no plate movement and after searching the Internet it looks like they should last for 400 cycles (20% DoD) but be able to handle more current. These are almost double the price though.

My voltage will be 72V (6 x 12V).

I just had a look at those Elecsol batteries. They are a good price, a bit smaller and should be lightweight, which is ideal. My concern with them is that their cold cranking performance is less than half what the car battery could do. The car battery I was looking at was an Alphaline.

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ChrisB
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Re: Do I need cyclic batteries?

Postby ChrisB » Mon May 03, 2010 8:34 pm

newtrikebuilder wrote:I need to keep build costs down really. At the moment I'm not sure how much I will use the vehicle, and with the amount that I will use it, it will cost me a lot per mile.

I've found some marine batteries which are a similar price, but 90Ah instead of 100Ah. This should be enough though.

I have also seen some AGM (Absorbent Glass Mat) batteries. Does anybody know about these? They claim to have no plate movement and after searching the Internet it looks like they should last for 400 cycles (20% DoD) but be able to handle more current. These are almost double the price though.

My voltage will be 72V (6 x 12V).

I just had a look at those Elecsol batteries. They are a good price, a bit smaller and should be lightweight, which is ideal. My concern with them is that their cold cranking performance is less than half what the car battery could do. The car battery I was looking at was an Alphaline.


I've looked at the Alphaline and they look like normal Car Starter batteries.....which they are :wink:

What you have to remember is that car starter batteries only ever get discharged by 2-5% maxium each time you use them (modern engines sometimes dont even use that much out of them during starting), thus they are constructed to carry this out, if you start discharging them to 80% they would very quickly fall over within just 30 or so cycles, due to the plates expanding and contracting causing the material to just fall off the plates in the end :(

While it looks like a cheap option using car starter batteries they really are not suitable for cyclic opperation and you'll only end up having to replace them very quickly.

AGM's are generally much better at cyclic work and you should get a good 400-500 cycles or more depending on your disharge currents.

To help you choose, its worth looking at the C rating of the battery you are thinking of using and try to match this to the discharge currents you will be giving them, although most of the time you will exceed it in a EV.

Take a look at the Alphaline 100ah battery its actual rating is over the 20h rate i.e C20 , thus to see its actual capacity you divide the 100ah by the 20hr rate which gives you 5..... 5amps per hour for 20hrs, not a lot is it, when I suspect in a EV you will be pulling 30-50amps all the time !!!!!!!
If you start discharging the battery above this then you wont actually get its rated ah from it.

Us EV folk discharge batteries really quite hard, and we really need to look at C1 rating i.e the Ah rating on a 1hr discharge, due to the currents that will be drawn by the motor. Rarely will you find a flooded LA battery giving a C1 rating as there not very good at delivering it, the next best rating is C5 thus a 100Ah C5 will deliver 20amps per hour for 5 hrs, as you can see this is much better than a C20 100Ah battery, of course the best battery would be a 100Ah C1 which would deliver 100amps for 1hr.

Li-ion batteries are very good at this 8) but then they are also loads of money :(

Trojans are generally pretty good something like these http://www.trojanbattery.com/Products/27TMX12V.aspx

How ever if you look even their C5 rating is just 85ah which means they will deliver 17amps per hr for 5 hrs, not exactly wonderful but they are constructed for deep cycling, how ever even these will not like being discharged outside these figures and will fail earlier than if they where kept within their design specs.

This is the main reason milk floats....a) went a slow as they did, and b) had such large battery packs, they needed to make sure the discharge current matched the discharge curve of the battery as best as possible.

Sorry for all the figures etc, hope it sort of makes sence, REALLY avoid using car starter batteries as you will be dissappointed with the end result in the end......they will be fine to start with but will very quickly fade away :cry:

ChrisB
I reject reality and substitute my own !!!!!!

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Peter Eggleston
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Re: Do I need cyclic batteries?

Postby Peter Eggleston » Mon May 03, 2010 9:32 pm

My head is getting sore from banging it against a brick wall!
Item no 220593094415 on ebay.
I have been running a set similar to these on my 45 mph slow milk float for the last 7 years doing 3000 miles per year, and they are still going strong.
I paid £11.00 per 12 volt battery for mine. They are ten times better than the Elecsols I had before.
I agree do not use car batteries, but there are alternatives without spending a fortune.
Peter

newtrikebuilder
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Re: Do I need cyclic batteries?

Postby newtrikebuilder » Mon May 03, 2010 9:46 pm

I've seen the Trojans but they are far too tall, so they wouldn't fit. I want to be able to do at least 60 miles at high speeds. 33Ah (C20) is supposed to give about 25 or 35 (can't remember which) miles. So I would expect 100Ah to do more than double that. I can't be certain which battery they used for their figures though, but it looks like it was that 33Ah one. I've also planning to get regen braking which should help.

I'm going to build my chassis for the Elecsol batteries and review the prices etc. when I'm ready for the batteries.

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Jeremy
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Re: Do I need cyclic batteries?

Postby Jeremy » Tue May 04, 2010 6:17 am

You'll need more than 33Ah of lead acid (any flavour) at 72V to do 30+ miles at speeds up to 60mph, on anything. 33Ah at 72V is a theoretical 2376Wh, which is a usable (assuming deep discharge cyclic cells) power capacity of around 1900Wh.

As an example, my very lightweight (30kg, less rider), relatively low drag, recumbent electric bike uses about 13Wh per mile at just 20mph. Raising the speed from 20mph to 60mph would increase the power consumption to about 117Wh per mile (power required is approximately proportional to the cube of the speed increase) and reduce my range from around 25 miles to about 3 miles. Increasing the weight by adding more batteries would increase the power required further, as acceleration and hill climbing power are proportional to weight, as is rolling resistance to some extent.

I think you need to budget for a minimum power requirement of around 150Wh per mile, as that will give you some slack to allow for battery capacity loss with cycling and age, and give the pack an easier time. Generally, you need to assume that the discharge depth for lead acid shouldn't go below 80%, so, for 30 miles range you need 150 x 30 = 4500Wh, and allowing for no more than 80% discharge this increases the pack capacity to 5625Wh. At 72V this equates to about 78Ah of rated battery capacity (5625 / 72).

If you reduce your speed requirement from 60mph to 35mph, then the power required drops dramatically, probably to somewhere around 50Wh per mile. The battery capacity needed then drops proportionally, to something like the capacity you've quoted.

I don't know what your budget is, but have you looked at using cheap (a relative term!) lithium packs? The guys over on the Endless Sphere have been having great success with using model aircraft lithium packs. These are now pretty safe if charged properly (good chargers are pretty cheap) plus they deliver extremely high current with virtually no loss of capacity (15C is trivial, most comfortably deliver 25C). Life is comparable to good quality AGM batteries, a few hundred cycles, but weight and volume are much, much lower.

This trike http://www.youtube.com/watch?v=WKAMus3oSdw is running at around 20kW with just a tiny 45V RC lithium battery pack. This battery technology may still be way outside your budget, but might be worth saving for if you really want something small, light and fast with a fairly good range.

Jeremy

newtrikebuilder
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Re: Do I need cyclic batteries?

Postby newtrikebuilder » Tue May 04, 2010 7:18 pm

I'm now aiming for 96V, which should allow me to hit 60mph. This should be a bit easier for the batteries and give me up to 9.6kw.

Some of my route will be slower. There are lots of twisty roads (can't do 60mph on these), a few 30mph limits, and few 60mph roads, and then about 10-15 miles in a 70mph limit (probably 60mph for the trike).

btw, I was never planning to reach 20% DoD and won't reach this if possible. My journey is just over 50 miles, but I want to allow a little extra just in case I take a wrong turn or something.

I know it's hard to tell, but do you think this is possible with regen braking? The trike normally weighs around 160kg, but with the extra batterys I'm probably looking at 200-250kg.

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ChrisB
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Re: Do I need cyclic batteries?

Postby ChrisB » Tue May 04, 2010 8:24 pm

newtrikebuilder wrote:I've seen the Trojans but they are far too tall, so they wouldn't fit. I want to be able to do at least 60 miles at high speeds. 33Ah (C20) is supposed to give about 25 or 35 (can't remember which) miles. So I would expect 100Ah to do more than double that. I can't be certain which battery they used for their figures though, but it looks like it was that 33Ah one. I've also planning to get regen braking which should help.

I'm going to build my chassis for the Elecsol batteries and review the prices etc. when I'm ready for the batteries.


Absolutely no chance I'm afraid :cry: 33Ah @ C20 works out at a MAXIMUM discharge of 1.65amps per hour for 20hrs, I'm really not sure where your getting those figure from but even at 96volts that means your using a motor rated at about 160watts :? my electric bike motor is rated at 200watts and even with a 15ah LiFePO4 pack which will deliver C1 rating its only good for about 30miles @ 15mph, no amount of regen braking is going to make the difference up.

Do look at Peters ebay number and those batteries, they are REALLY the sort you need to be looking at :wink: and their cheap'ish 8)

ChrisB
I reject reality and substitute my own !!!!!!

newtrikebuilder
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Re: Do I need cyclic batteries?

Postby newtrikebuilder » Tue May 04, 2010 9:32 pm

Those batteries on ebay are far too tall.


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