Nicad vs Sla?

I have been thinking about building nicad packs to eventually replace the slas I have on a couple of bikes. I currently use three 12v 7ah slas for 36 volts. I get around 12 to 15 miles per charge which is right about where I need it to be. I am thinking about building 36v 4.5 ah nicad packs. In everyone's opinion would I get more range with the slas or nicads?

I wouldn't get much of a weight savings with the nicads so I'm not sure it's worth the trouble.

Strange...you should see a pretty significant weight savings with the NiCds. They're very light per Wh. And a single 4.5Ah pack would probably be slightly less than the 7Ah SLAs. Two would be a big improvement.

I always thought nicads were about 2/3 the weight of SLAs. Still, a 4.5Ah pack is going to be a lot lighter.

I was really just going by the weight of this pack:

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1984

It says it's 3.4 lbs. I guess it would save quite a bit of weight for the entire pack. A 7ah sla weighs around 6 lbs.

Any opinions on the range difference?

I have some 9Ah SLA's that weigh about 5.5 pounds. I get about 12 miles at full throttle and 20-26 miles at 15-17 mph.
http://endless-sphere.com/forums/viewtopic.php?f=9&t=6971
I can sell them cheaper in higher quantities, I have about 15 or so left to sell, I am using them as a backup for my lifepo4 pack and for a large trailer battery.

You get the benefit of higher c rate with the nicads, and no sag.

I'm using NiCads on my BL-36 I assembled from some 14.4 v tool packs I found cheap. They are only 1500mah though so I assembled them as 48v packs and I run them in parallel to gain Amp Hours. At 1.5ah per pack(2lbs per pack) I can run 4 together for 6ah (8lbs) and it gets me 2 miles to work and 2 miles back at full throttle 25mph. I could continue to ride another 3 or 4 miles. 3 packs will work fine for the short distance I travel, but I like to be prepared. I have many more packs assembled so I can always have some charged and ready to go. Also I can add more when/if I need more range.

I was looking to try this out at minimal cost and this is a cheap alternative and it get's the job done, but it is a hassle to charge so many packs and keep them ready without buying a lot of chargers (I use 2), so I would recommend spending the money to get some good nicads with higher amp hours. This was really just an experiment for me, but I highly recommend NiCad. They take abuse well and don't need the BMS.

AVS

Those emergency backup light D nicad packs from the link are rated at 500ma discharge. I don't think they have any business being on an ebike unless they are powering lights.

vanilla ice said:

Those emergency backup light D nicad packs from the link are rated at 500ma discharge. I don't think they have any business being on an ebike unless they are powering lights.

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I'm not planning on using those packs, I was simply using that example to figure out an approximate weight. As I said in my first message, I'm planning on building my own packs. I found some higher discharge d size cells for a good price and I'm just trying to figure out if it's worth switching.

Ah, I didn't know there was such a thing as high C rate D's.

They exist, but they're not cheap. I think either Sanyo or Sony makes some capable of ebike-worthy rates, but they're like $20/cell, which puts them in the same price range as A123s.

vanilla ice said:

Ah, I didn't know there was such a thing as high C rate D's.

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I will openly admit I don't know squat about nicads. The person selling the cells said they were higher discharge nicads. I don't have the specs on them. They may suck for electric bikes. That's one of the reasons I tend to run ideas by people on here before I go too crazy.

Anyway... This d cell pack has a 15a discharge rate (my bike's max amp pull is usually only 20 amps) http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2541 so maybe it's doable? I'll see if I can get the specs on the batteries. It's so tempting because they're offering me 100 of them very very cheap.

Is anyone here using d cells on their bike?

EVTodd said:

vanilla ice said:

Ah, I didn't know there was such a thing as high C rate D's.

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I will openly admit I don't know squat about nicads. The person selling the cells said they were higher discharge nicads. I don't have the specs on them. They may suck for electric bikes. That's one of the reasons I tend to run ideas by people on here before I go too crazy.

Anyway... This d cell pack has a 15a discharge rate (my bike's max amp pull is usually only 20 amps) http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2541 so maybe it's doable? I'll see if I can get the specs on the batteries. It's so tempting because they're offering me 100 of them very very cheap.

Is anyone here using d cells on their bike?

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Ebike vendor in Vancouver Canada sells the nicads. I bought 3 48v 8amh and 2 36v 8amh and chargers. They are heavier than lithium but are reliable, will not sag much and go a fairs ways if you pedal. Pedalling is the trick.

Myself, I think lithium is the way to go, but they are so overpriced...

I use high discharge rate (10C) SubC NiCads in solderless tubes.

They work flawlessly and were cheap.

I built the tubes using PVC pipe and ACE Hardware #96 springs and copper contactors to ensure good conductivity.

SubC is the way to go for NiCads or NiMh...

I have a great source for Ni-Cad battery Packs(And Ni-Mh etc.),it is Sanforce Battery Co.,Hong Kong,e-mail sanforce@gmail.com,talk to Stephen. They make e-bike battery packs and acc.,the prices are very good,and Stephen is very knowledgable. I was pricing 48v-7ah and 48v-12ah packs,sorry I can't remember prices now,But he explained to me that his packs were Hi-rated-"48v-12AH can achieve 35 amp discharge long time,50 amp short time no problem.We even ran it at 80 amp discharge very short time ok..." Of course they have appropriate chargers,quick couplers etc. I have not had a chance to try the Ni-Cads yet,but what I read from a university study on battery types they are best for my use on e-bikes,high output,not fussy,and apparantly have many more cycles than lithium batteries. I had a 36v-12ah Li-ion in my last bike,very light and compact,it built to my specs by a factory in China,but it succumbed in about 6 months to charging or cucuitboard problems...I have no use for them anymore,too expensive and unreliable.
For now I run 4 12v SLA's,48v-12ah and they work great but it does take a little used to the extra wieght on the back of the bike,I have the batteries and electronics and wiring in saddle bags...When charged up the SLA pack is at 52.5 volts approx.,and after a run around town and back at home I still have over 50 volts. I haven't had a chance to go for a good long ride yet,it is raining lots right now on the West Coast. I have a 5304 front motor,not sure of top speed yet maybe 50-60kph,the cycle computer shows me pulling about 35a and 1600w at full throttle. I have to admit the bike is a little heavy.

Safe,

I have thought about making solderless tubes myself. I think it would be an easy way to replace bad cells as needed. I'm just thinking it would take a ton of cells to even equal the 36 volts/7ah I have of slas.

...and back to the weight of nicads. I was just looking at ebike.ca's web site and found this pack that looks very nice to me:

http://www.ebike.ca/store/photos/B3608CdT1-EL.jpg

I'm just a bit shocked at the weight. They show it at 13.23 lbs. That's only 4.77 lbs lighter than my slas. It would be nice to shed almost 5 lbs but I'm not sure it's worth the money to switch. I know you can drain nicads all the way down but would a 8ah nicad pack give me THAT much more range than a 7ah sla pack?

I'm starting to wonder if ping would make me a custom 7 or 8 ah pack.

EVTodd said:

I know you can drain nicads all the way down but would a 8ah nicad pack give me THAT much more range than a 7ah sla pack?

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Don't forget the dreaded Peukerts Effect.

If you run SLA's at their designed 0.1C you could get all that 7Ah out of it, but in all probablity you are running at closer to 3C or more and than means you get closer to 2Ah of actual power out of the pack.

The NiCad's deliver nearly all their power and you can't break them as easily. If you do as I do and run the SubC's which are capable of 10C and then run them conservatively like 3C or less you have a very durable and economical pack.

Solderless tubes work... but you need to build them and many people are not as good at the craftsmanship as I am. I can imagine someone trying to do it and having trouble building the tubes with precision.

So far (after 1,000 miles or so) I've had great success with solderless tubes...

Safe, rather than building them I also thought about using these:

http://www.modelelectronicscorp.com/browse_product.php?pid=30

The goal for my pack should be pretty easy to achive. Like I said, I'm getting 12 to 15 miles of range with my 7ah sla pack. Since you can run nicads all the way down maybe I can get the same range with a 4.5 ah pack.

I'm sure those tubes work fine.

My latest project will use this:



Which translates to 8 X 3 X 10 (cells) = 240 SubC cells.

As for Ah it's 6 * 2.4 = 14.4 Ah @ 48 volts for about $350.

Peak amp capacity would be well over 100 amps, but I'm never going to use more than about 25 amps and that should reduce wear and tear significantly. (using too many amps would burn up my little motor)