What sub-C to use? NiCad or NiMH?

[Wolf]

Ok, this has nothing to do with flashlights but I know most of you know way more then most about batterys /ubbthreads/images/graemlins/help.gif problem I have is one of my NiCad /ubbthreads/images/graemlins/icon15.gif 18vt 2.4ah Milwaukee tool battery pack died, wont take a charge and is showing 1.7 volts on my DMM, IMO it seems to be doa, well instead of paying 70-$80 for a new NiCad pack /ubbthreads/images/graemlins/broke.gif + /ubbthreads/images/graemlins/icon15.gif
Who wants to keep a NiCad when there is NiMH /ubbthreads/images/graemlins/cool.gif well I cracked the pack open (screwed together not glued thankfully) it has 15 sub-c cells in it (Dia 22.76mmX43.7mm) and seems to have a thermo switch in it as well
one of my newer packs (on 2nd charge cycle now) showed 20 volts fresh
So.. The questions of the day is
1: NiMH or /ubbthreads/images/graemlins/icon15.gif NiCad
2: What mah cells should I use?
3: Should I get good charger/peak-match the cells? (I have 10 of these packs total 7 of which are the same age of the one that died so I expect to be "Reloading" a few more packs soon)
4: Anything I should keep in mind with this swap idea? the factory chargers I have all say NiCad/NiMH on them, and I use them in 2 drills, a sawzall, a circular saw, a 1/2" impact gun and I use the tools often
5: Best source for NiMH cells?

 

[VidPro]

here is some ideas, because them packs in them tools and them tools cost a LOT, this is all my "OPINION" and does not represent facts.

if at all possible get NI-MHY , most of the charging circuits that i have changed the batteries in the tool, or parts from NI_CD to NI_MHY have charged the NI_MHY as well or better than they did the ni-cads.

you can not in any way shape or form, replace JUST a few or one, of the dead cells, the whole pack must be changed.
because if some of the cells are better, or worse than others, you will get more reverse charging when the pack is low.
and in these, Large higher voltage multiple batteries in series packs, that is usually the PROBLEM that ruins them, not memory, or all the other stuff, the pack imbalances is the problem.
so much so, that the packs i design for my video lights (also high power) i make sure are dissasembleable, so i can cycle them as seperate cells every once in a while.

back to the charger, if your NI-MHYS are 3X the power of your NI-CDs (which is about par) it will take the same charging circuit 3X as long, or very close to that.
it will charge them slower, so it wont be so mean to the batteries.
because it will also RUN for 3X as long, this is not usually a problem, if it is, then do something to upgrade the chargers then.

the other packs that are not yet dead, may be 100% salvagable, if you want to play maintanance games with them, there are even locations where they "recondition" a ni-cd pack for big money.
You can recondition the pack also, just remove the cells and discharge them as seperate units, then charge them (even if its in the pack) then discharge them as seperate units again. that should be sufficient.
this attempts to balance out the cells that are high.

sources??? i donno, i got to THOMAS distributing first, then other places, like batteries only and other web locations that will sell seperate cells. dont have all the links here.

 

[MrAl]

Hi there,

I'd have to recommend sticking with the NiCd's for power
tools. The reason being that the NiCd's handle very large
currents better than NiMH cells without damage, and may
even have lower internal resistance.
Besides that, there's also the issue of how to charge
if NiMH cells were installed. NiMH cells dont charge the
same way NiCd cells can be charged, and could easily be
damaged if using the same charger that was used to charge
the NiCd's.

I had considered the same for one of my drill packs, and
also decided to stick with NiCd's.


Take care,
Al

 

[Wolf]

Well I dont see how a 1300-2400mah NiCad battery can out power a 3300mah NiMH cell that doesnt make much sense, I did alot of research last night, and my charger (as I noted in the first post) IS NiMH ready, Far as i understand NiHM works somewhat better then NiCad in cold
From what I have read I think I am going to give the NiMH a shot with GP 3300mah sub-c NiMH which are said to hold at 1.8-1.7 voltish UNDER LOAD

 

[Ginseng]

What MrAL said.

If you intend to use the charger that came with your system and it originally used nicads, stick with nicads. I think you must have mistyped your last post as nimh chemistry doesn't deliver 1.7-1.8V/cell under any condition. I use the GP3300 and IMO they'd be a waste of money in a tool pack. Last I checked, they were about $5.25 each. An 18V pack would cost you $85 with shipping and at that point, might as well buy a Milwaukee replacement.

In nicads use the Sanyo N-1900SCR ($2.50). In nimh, use the new Sanyo 3600 ($4.75). The question I'd ask is the double capacity worth double the cost especially since you have 10 packs. The difference in total cell cost is almost $340 between nicad and nimh.

Wilkey

 

[Wolf]

Good points Ginseng, the NiMH specs I posted are not a typo, alot of the RC racers are using the gp3300 with insanely high discharge rates
Somehow everyone that has replyed has overlooked the fact that the orignal charger for the tools are NiMH ready, I might just end up converting 2 of my packs to NiMH for use when I am not in the shop/ off-roading and just go with the suggested Sanyo N-1900SCR (but where are ya gettign them?)
Now that I've though about it alittle also, the double capacity might be good in the shop as well, but... how will my charge times be effected?

 

[Ginseng]

Wolf,

I use the GP3300 and GP3700 in various light setups and while they will comfortably handle discharges of 10A and beyond, they do so at cell voltages of "only" 1.15V/cell. This is not far off of GPs own product data sheets.

Well, doubling capacity will roughly double your charge time. Now that I think about it, it might be nice to have one or two nimh packs for those times when you'll be away from the charger and need to get work done. Several toolmakers are selling tools with nimh packs and the general consensus is that they far outperform their nicad counterparts. In fact, when my Makita finally croaks, I'm going to buy a tool with a nimh pack.

BTW, I highly recommend www.battlepacks.com for your high-current cell needs.

Wilkey

 

[evan9162]

Still, NiMH doesn't ever deliver 1.6-1.7V per cell.

 

[Wolf]

/ubbthreads/images/graemlins/stupid.gif oops, 1.18vts...

 

[MrAl]

Hello again,

Wow, 15 cells in one pack? That's a lot of series cells
to charge in series when using NiMH cells. I dont even
like charging TWO in series...no way would i want to
charge 15...unless each cell had it's own sensor maybe.

I'd hate to see you spend a lot of money and end up having
a pack that doesnt live that long.


Take care,
Al

 

[Wolf]

[ QUOTE ]
Ginseng said:
Wolf,

I use the GP3300 and GP3700 in various light setups and while they will comfortably handle discharges of 10A and beyond, they do so at cell voltages of "only" 1.15V/cell. This is not far off of GPs own product data sheets.

Well, doubling capacity will roughly double your charge time. Now that I think about it, it might be nice to have one or two nimh packs for those times when you'll be away from the charger and need to get work done. Several toolmakers are selling tools with nimh packs and the general consensus is that they far outperform their nicad counterparts. In fact, when my Makita finally croaks, I'm going to buy a tool with a nimh pack.

BTW, I highly recommend www.battlepacks.com for your high-current cell needs.

Wilkey

[/ QUOTE ]

ouch just looked at battlepacks prices /ubbthreads/images/graemlins/icon15.gif
I was looking at www.maxamps.com little better prices for the GP's they carry some nice connectors for making custom packs (great for the spotlight guys) and for the GP3300 they "gauranteed to be at least 1.18s or your money back"
I have a few dead makita 4.8v drills that I am thinking of making small NiMH cells for cause they are just too handy for small drilling
As for the comment about the 15 cells, yeah it is alittle nuts, makes me somewhat worry about charging them, esp seeing most of the hobby chargers dont do more then 8 cells (i think..) I figure at worst if the NiMH cells dont work out, I'll just use NiCads to reload the tool packs and guess I'll have to find a hand-held Spotlight to HID (one of them home-depot branded alum Vectors looks good to me /ubbthreads/images/graemlins/grin.gif )

 

[lumen aeternum]

I'm guessing that since 2005, the recommendation today would be to upgrade from NiCad to Lithium Ion batteries, instead of NiMH ???

Unless the tool was of a type where you might want to be able to keep going even when the battery is providing a lot less torque, in which case sticking with NiCad is the better choice (???)