Why not Nicad?

[fitek]

BTW, the 4Ah Tenergy cells in this thread aren't as good a deal as the 3.5Ah; the 4Ah cells are 70 cents/W-h vs 64 cents/W-h for the 3.5Ah.

 

[Link]

Don't use the Tenergy D cells. They're not made for high-amp discharge by any means. They barely pull 10A.
And the other cells (at least the 3800mAh sub-Cs and the AAs) don't hold as much as they claim.

 

[Parker]

I noticed that a the new bosch cordless drill that showed up at work today reverted back to nicads where
they were previously boasting NiMH. For me my SLA's are working good for now so I'm not rushed.
I am doubting I'm going to get around to taking the time to build my own pack though. Maybe I could interest
someone here in building me a pack on down the road. mmm

 

[safe]

http://www.ebikes.ca/store/#Batteries

NiCads

In the rush to upgrade from Lead Acid to the latest NiMH and Lithium packs, it seems that most companies forgot about the old venerable Nickel Cadmium battery as a suitable option for ebikes. NiCads have a solid and proven track record in demanding rechargeable battery applications, and because of the diminished interest they are available these days at very reasonable prices.

The NiCad batteries are about half the weight of an equivalent lead acid battery pack, but not a whole lot more expensive. While the cell manufacturer says that they can handle 5C discharge currents, we don't recommend they are used in a pack configuration above about 3C continuous. The cells get quite warm on discharge, partly because they have a higher internal resistance than a similar NiMH pack, and partly because the discharge reaction is more exothermic.

 

[safe]

What To Do For Project #002?

I've been going back and forth with a lot of ideas about what the heck I'm going to do to fill my Project #002 bike. It was designed to hold 80 "D" cells and yet it can just as easily hold up to 120 "SubC" cells in the same place. So I've been looking at all kinds of arrangements and pricing scenarios.

The "D" cell NiMh cells tend to have the problem that while they have more capacity they tend to be weak in the "C" rate department.

The "SubC" cell NiMh give plenty of "C" rated amps, but their capacity is not very good.

Both the NiMh have short calender and cycle life so you have the "gotcha" that you might run out of time to really use them up if you don't ride the bike frequently enough.

NiCad "D" cells are pretty cheap, they last a long time and the capacity is slightly better than the SubC's (usually) but less than the D's. They can be rapidly charged at 1C which means that you can get more rides in per day if that's what you want to do. (no long 8 hour recharges)

So I'm looking at:

NiCd D Size 5000 mAh Rechargeable Flat Top battery - $3.85

http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1775

...and:

D size Nickel Cadmium Rechargeable Battery 7000 mAh - $4.75

http://www.batteryjunction.com/r1ed-gd7000.html

...for charging there is this:

(4) Smart Charger (1.8A) 24V NiMH / NiCd Pack - $39.95

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2969

...or possibly the more expensive (but better):

(4) 24V 4A NiMH / NiCd Charger - $80

http://www.ebikes.ca/store/#Batteries

Thoughts?

 

[Nil]

How about strapping these little Nicads to your bike? 122AH per cell, 23 cells.

I would be interested in seeing the bike that can haul these things, wouldnt want to ride it myself though. As someone said 'Chicks don't digg acid burns'... what about Alkali Burns?

 

[TylerDurden]

How about strapping these little Nicads to your bike? 122AH per cell, 23 cells.

Kickass on a trailer...

 

[Toorbough ULL-Zeveigh]

Both the NiMh have short calender and cycle life so you have the "gotcha" that you might run out of time to really use them up if you don't ride the bike frequently enough.

utter rubbish, no truth in it whatsoever, total opposite in fact.
YPedal's NiMH worked as new after sitting unused for a year, not to mention Knightmb experience, hell, even the Prius pack warranty.
Perhaps it's true of the craptastic Tenergy's you plan on buying.

Put it this way, if you truly believe 500 cycles min & 5+ years is so short, at least it's longer than SLA, even LiPo.

 

[Sputnik]

It's important to store them with some charge. I think storing them completely discharged can possibly cause them to leak electrolyte and degrade quickly.

I remember reading an article many years ago that mentioned when storing NiCd cells for extended periods of time, the cells must be in a discharged and cooled state. Not just discharged, but shorted across its terminals as well! The article mentioned slowly discharging to nearly 0V before storing with the short (obviously).

After reading this thread, I think I'll be using NiCd for my electric go-ped/scooter thing. LiFePO4 is a little too expensive at the moment, even Ping's packs (Still a student).

I've read on this forum that it's common practice to first parallel Li-ion cells before stringing them together in series. Does this also hold for NiCd?

Sputnik

 

[Link]

I've read on this forum that it's common practice to first parallel Li-ion cells before stringing them together in series. Does this also hold for NiCd?

No. LiFePO4 self-balances, NiCd does not. In fact, this is a very good way to destroy them. Because their voltage actually drops slightly when they reach their end of charge, the cells that are done charging will be overfilled by the cells that aren't. This has the tendency to make them, er...explode. :?

Best way is to use parallel strings of batteries (as opposed to paralleling the cells) and use an individual charger for each string.

 

[monster]

i have lots of nicad and nimh on my bike and they work great. i do 20mile/day on them. let me elabourate...

you can parallel them for discharge no problem, but not when charging.

there is a problem when parallel charging nimh or nicd because when they reach full charge they dip slightly in voltage and this means in an unchecked parallel string the first battery to reach full charge will hog all the charger current and this could fry the battery.

however you can charge multiple nimh from one charger but the parallel batteries have to be seperatly charge terminated. so you would need to get these thermostats from maplin http://www.maplin.co.uk/Search.aspx?criteria=temperature switch&source=15&SD=Y

i suppose you could use these thermostats like a BMS if you could run them from the battery voltage. one per battery which acts to isolate the battery from charging when it gets hot. you could install them on the bike permenantly then you could just use a "dumb" charger.

 

[powermed]

ok...I think I have an answer as to "why not Nicad"

Someone update me if I'm wrong, but if I remember correctly NiCad is about the worst battery on the planet when it comes to pollution - the cadmium that is. Not that anyone here would bury one in the back yard, but in our pursuit of e-conversion and usage, is the green thing enough to make this something to avoid if for no other reason, so as to not contribute to the continued use of the technology. I'm not a polarized kind of guy - but I'll admit - it did influence my decision a few years ago when I was experimenting with tool packs.

 

[monster]

if you recycle it at end of use, like you should with any battery, then its fine. add to this the fact that Nicds last 3 times longer than most other chemistries and the overall life cycle analysis shows that Nicds are better or equal to any other chemistry for the environment. i give more weight to overall CO2 emissions than emissions to water courses -but maybe thats just me

http://www.electric-bikes.com/betterbikes/Ebike_Energy.pdf

 

[Sputnik]

I think I may change to NiMH as I cannot find any NiCd of sufficient capacity locally. I've found 13Ah NiMH F cells but may go for some 9Ah D cells. Worse case I'll have to use 4Ah C cells (Cost and space considerations).

But the site I'm looking at for cells states that NiCd has only 200 cycles as opposed to 1000 cycles for NiMH. But I've read the opposite on this forum.

Sputnik

 

[powermed]

Hi Monster - thanks for sourcing that study - good reading (if you're into that kind of thing). Comprehensive but I didn't see anything on the recycling "costs" - something I think would have been fairly straightforward to estimate with a little digging. As we all know many packs die premature deaths too...

 

[needWheels]

I think I may change to NiMH as I cannot find any NiCd of sufficient capacity locally. I've found 13Ah NiMH F cells but may go for some 9Ah D cells. Worse case I'll have to use 4Ah C cells (Cost and space considerations).

But the site I'm looking at for cells states that NiCd has only 200 cycles as opposed to 1000 cycles for NiMH.

NiCd supposedly takes much more abuse and cycles.

BUT don't make the mistake with D cells (or even F cells).
While you think you have the mAh, you do NOT have the C (draw rate) from those kinds of cells.
For example if you setup 9aH of D cells, you can only draw 1C with most D cells.
Some bikes want 20A-30A depending what you are doing (up a hill may be even more).

F cells are so expensive it's usually the same price to go LiFePo4

subc nicd/nimh are the only ones available in high C rates (5C-10C)

But then there the problem of charging such a large string of parallel subc cells.

I gave up on the idea. Saving for LiFePo4