Sanyo N3000CR Nicads..racing??

[johnws6]

All,

I have about 300 Sanyo N3000CR nicads i'm thinking about using for an electric pocket bike. My plan is to make them into a 40S 5P pack, and then maybe a 40S 2P pack as well, so possibly 40S 7P total. I have to split them up so they fit, i'm just not sure if i should bother or will need the extra power.

Current setup:
Cat eye pocket bike
Met DC 36 volt 6" diameter motor ( ebay special )
Logisystems 48 volt 700 amp controller

I had used 1/2D saft nicads before, i got them cheap what can i say. They had a relatively high resistance rating and weren't for high discharge applications. They ended up finally overheating and going into thermal runaway and blowing through in some places.
These are the cells i originally used in a 40S 5P pack.... http://www.saftbatteries.com/doc/Documents/rechargeable/Cube675/vre_1-2_ddata_sheet.0dea3c4f-cde2-413e-8c75-a00aa46bcbfc.pdf

This is what i'm going to use.... http://www.sanyo.co.jp/energy/english/spec/cadnica/N-3000CR.pdf

I'm really wondering if i should bother with any sort of cooling system i guess is my main question. With the problems i've run into the past with the old pack i've learned my lesson as far as keeping battery heating to a minimum. I have some decent air flowing computer fans that i could incorporate into the pack to keep it cool, and i've thought of also placing aluminum flex tubing between the cells also using a water cooling system with ice, i dont know if this would be effective. Does anyone think i should even bother or think i would need to have a cooling system in place with these cells?

 

[liveforphysics]

Depending on your budget, it would seem high discharge lipo packs would offer much better performance with minimal weight and volume.

However, if you are just looking to use the cells you have available, and you have space for them in your project, that looks like a pretty nice cell for NiCd chemistry.

-Luke

 

[pgt400]

How do you charge a nicad 5p pack? I've always heard it can't be done without diodes to separate the cells?

 

[Jeremy Harris]

Even with isolating diodes it's still dodgy charging NiCd or NiMH cells in parallel. I had a really nasty battery explosion and fire from charging a small 20S, 2P, NiMH pack about a year ago (there's a thread here somewhere with photos of the debris) and would never, ever, risk charging with cells still connected in parallel again. I know that NiCd is a bit more tolerant of over-charge than NiMH, but I'd still not risk it.

I guess it would be OK if the cells were wired into separate series strings, each fed by an individual charger though. All that would be needed would be a way to connect the individual series cell packs together for discharge.

Jeremy

 

[johnws6]

Depending on your budget, it would seem high discharge lipo packs would offer much better performance with minimal weight and volume.

However, if you are just looking to use the cells you have available, and you have space for them in your project, that looks like a pretty nice cell for NiCd chemistry.

-Luke

If i could find them pretty reasonably priced i would go for it, but i haven't really found any cheap enough to make it worth while. The other worry i have is lipo can catch fire and explode. I'd have to make a pretty tough battery box i guess.

 

[johnws6]

Even with isolating diodes it's still dodgy charging NiCd or NiMH cells in parallel. I had a really nasty battery explosion and fire from charging a small 20S, 2P, NiMH pack about a year ago (there's a thread here somewhere with photos of the debris) and would never, ever, risk charging with cells still connected in parallel again. I know that NiCd is a bit more tolerant of over-charge than NiMH, but I'd still not risk it.

I guess it would be OK if the cells were wired into separate series strings, each fed by an individual charger though. All that would be needed would be a way to connect the individual series cell packs together for discharge.

Jeremy

My actual plan is to never disconnect the packs in any way physically. In my example of the 40S 5P pack i am actually splitting each pack into 20S for charging using a battery selector switch. Mc master part 69685K61. It's basically a very high power 3 way switch, it's actually rated 48 volts and 350 amps continuous on the case, i dont know why mc master has it listed as 32 volts. I am using "10" 30 minute 24 volt hitachi chargers from the power tool world.

I'm going to have the 3 way switch link the 24 volt packs into series. This way i can have individual wires from each 24 volt pack come off into a anderson powerpole connector block mounted on the side panel for charging.

 

[Jeremy Harris]

I configured my pack as two series strings of 30 cells each, connected via a large double Schottky diode to parallel them up. There's a thread here that discusses what probably happened: http://endless-sphere.com/forums/viewtopic.php?f=14&t=3241#p47328http://endless-sphere.com/forums/viewtopic.php?f=14&t=3241#p47328

Jeremy

 

[johnws6]

I configured my pack as two series strings of 30 cells each, connected via a large double Schottky diode to parallel them up. There's a thread here that discusses what probably happened: http://endless-sphere.com/forums/viewtopic.php?f=14&t=3241#p47328http://endless-sphere.com/forums/viewtopic.php?f=14&t=3241#p47328

Jeremy

I read through that thread a while back. I never was a fan of Nimh batteries, they always seemed too delicate to abuse. I know they have more capacity per size and weight than nicad but when i was involved with robotics, and more specifically combat robotics, you didn't see people using BMS systems. Most of those guys in the larger weight classes use hawkers and high quality sanyo nicads. I've never had a sanyo nicad blow up on me. I have had saft and gp cells of nimh and nicad chemistry go bad on me though, which has led me to the current route i'm taking as mentioned earlier. Also, i've never trusted nimh batteries to be balance charged using a low current.

 

[johnws6]

Actually, now that I think about it more, my idea for seperating the 48 volt packs into two 24 volt packs for charging won't work. I was planning on using 1 high power switch to separate them for charging but this would still leave them in 24 volt parallel packs. Hmmm i guess the only way to make this work is to use 5 switches or physically disconnect the series connections to split the 48 volt packs up for charging.

 

[webfootguy]

I have about 300 Sanyo N3000CR nicads i'm thinking about using for an electric pocket bike.

So where did you come up with 300 cells? The TWIKE I'm rebuilding uses 280 Panasonic 2800 mAh C sized cells per pack (up to 3 packs) and I need to replace some of the cells. Got a good source?
--phil