NI-CD any good for a scooter?battery pack?

[zogthegreat]

Hi everyone

Before I begin, I will state the following:

I know that lithium gives more mileage.

I know that lithium is better for recharge cycles.

I know that lithium is lighter.

However, I know that lithium is VERY expensive and I am on a very tight budget.

Here's my question:

I have been rebuilding a battery pack for a cordless drill with these:

http://www.ebay.com/itm/12PCS-Sub-C-2500mAh-1-2V-Ni-CD-Rechargeable-Battery-Tabs-Power-Tools-Pack-Yellow-/271845129722?hash=item3f4b3b7dfa

and I was wondering is there any reason NOT to use NI-Cd for a scooter? I know that lithium gives you more mileage with less weight, but but the NI-CD seem less expensive. I found these:

http://www.ebay.com/itm/30pcs-SubC-Sub-C-With-Tab-1-2V-6000mAh-Ni-MH-White-Color-Rechargeable-Battery-/111473188530?hash=item19f451deb2

Seems to me that 90 of these should give about 18ah at a cost of about $137.00 USD. A replacment pack of SLA's for my scooter is about $75.00 USD, but they are only lasting me one season. The NI-CD should last longer and have a better recharge cycle and weigh substantially less.

Any thoughts?

 

[Gregory]

First I would suggest you re-consider using lithium. A 10S 10Ah (if that's big enough to start) pack is pretty close to that budget excluding charging and BMS. Remember if the capacity of your SLA was 18Ah you need half that in lithium capacity to go about the same distance.

Now that's out of the way, I would not accept at face value a no name cell claiming 6000mAh in a sub c size. Get a single to test first. Test capacity and voltage drop under load (C rate) to see if it will meet your requirements. I am sceptical.
How are you planning to charge these? Three parallel strings one after the other (i.e three strings of 10S1P in parallel, broken down for individual charging)?

Best of luck.

 

[Punx0r]

Sounds massively over-rated and probably junk. I bought some subC nicds from China to make a replacement battery for a low-powered appliance. One was dead-on-arrival and the rest died after a few cycles.

Good quality nicd is OK (long lived, good discharge rates, twice the energy density of lead, but still well below Li-ion) but it's still difficult to work with as they cannot be charged in parallel (fire/explosion).

 

[amberwolf]

If you're going to use 90 of them in series, that's a pretty high voltage, for a pretty low Ah and probably a fairly low current (unless you don't mind a large voltage drop (sag) under load).

If you're thinking of setting up any form of Ni-xx chemistry cells in parallel, you'd better try getting more familiar with the chemistry and why it's not usually a good idea to parallel them for charge (especially) or discharge, because of the way they work.

There is a lot of info; here's some of the articles in the wiki:
https://endless-sphere.com/w/index.php/Nickel-metal_hydride_%28NiMH%29
https://endless-sphere.com/w/index.php/Nickel-cadmium_%28NiCd%29
https://endless-sphere.com/w/index.php/Charging_Nickel-based_batteries

It is possible to parallel charge them, but you can't use the cells' "built in balancing" mode (or typical types of Ni-xx chargers), and have to use a different charging method, and must monitor individual cell voltages during charging, etc.

Discharging may be a problem too, depending on pack design and circumstances.

 

[zogthegreat]

@ amberwolf

There is a lot of info; here's some of the articles in the wiki:
https://endless-sphere.com/w/index.php/Nickel-metal_hydride_%28NiMH%29
https://endless-sphere.com/w/index.php/Nickel-cadmium_%28NiCd%29
https://endless-sphere.com/w/index.php/Charging_Nickel-based_batteries

Welll, I guess that answers my question!

Thanks for the links/info amberwolf.

@ Gregory

First I would suggest you re-consider using lithium. A 10S 10Ah (if that's big enough to start) pack is pretty close to that budget excluding charging and BMS. Remember if the capacity of your SLA was 18Ah you need half that in lithium capacity to go about the same distance.

Do you have any links for batteries that would be priced in this range? I've been searching the forum, but there seems to be multiple sources, not really sure who is a good supplier.

Also, do I need to buy all of the batteries at the same time, or can I space it out, i.e. buy some batteries one month, more the next? BTW, I'n not interested in LIPO's. I bought some of these packs from HK:

http://www.hobbyking.com/hobbyking/store/__10288__Turnigy_5800mAh_6S_25C_Lipo_Pack.html

and I had dead cells on arrival! Seems HK's policy is once they are out the door, their your problem, (plus LIPO's can go boom very easily!).

Thanks to everyone for the fast responses! :lol:

 

[amberwolf]

Also, do I need to buy all of the batteries at the same time, or can I space it out, i.e. buy some batteries one month, more the next?

Why not just save up till you have enough for all of it?

Remember that batteries have a calendar life as well as usage life.

Also, that different batches could have slightly different properties, potentially affecting the operation of the pack built from them.

 

[Gregory]

I don't know what your budget, range or discharge requirements are. All I know is given you were asking about bare cells, I assumed you are interested and skilled enough to assemble a battery DIY using individual cells. And size and weight are low priority.

Pretty sure a search for "18650 supplier" would yield plenty of hits I'm just saying don't write off lithium till you've investigated all the options, because I'd hate to see you disappointed after sinking hundreds into a poor quality nicad pack. For example.......


Many users are recycling 18650 cells from laptop batteries, lots of work, big parallel strings to compensate for low discharge capability, very cheap.
DocBass occasionally sells 18650 cells from tool packs, ideal if in Canada. Used.

Tumich was selling new, quality 18650 packs from ebike batteries that failed welding QC at bargain prices. I would check him out if I was in the market.
oshikara was selling 18650 Tesla cells at reasonable prices. Newish. Probably others too.

FastTech sells cells and could do 40 x Samsung 25R 18650's for under $200 inc shipping. As can other Chinese suppliers (Supower?).
As can nkon.nl, plus a bit extra for shipping?

And yes, HobbyKing lipo like the Multistar packs also factors in.

Add the cost of a BMS and charger to any of these options.

 

[zogthegreat]

Tumich was selling new, quality 18650 packs from ebike batteries that failed welding QC at bargain prices. I would check him out if I was in the market.

Hmm, this is actually a better price than I was looking at for the NICD. Thanks! :lol:

Add the cost of a BMS and charger to any of these options.

Yeah, I've been researching the BMS, I have to settle down and decide if I'm going to stay with a 36v setup or start a new project @ 48v.

Thanks again for the link, it's a real help to me.