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PICList Thread
'[EE] Batteries'
2009\04\20@042533 by Luis.Moreira

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Hi Guys,
I have a couple of battery drills where the NiCad batteries are shot. I
have no justification to scrap the drills just because of that, as I
only use them occasionally and they are perfectly fine.
My biggest problem is that, because I used them sometimes very
infrequently the batteries are always discharged when I needed them. I
then left them charging for long periods of time with the charger
supplied and that's what probably damaged the battery packs.
Both drills have two battery packs, so I can play a bit...

My requirement is to have at least one battery pack fully charged
whenever I need it for each drill.

So here are my questions:

       - These are 12V drills, the battery packs have 10 of what it
seems C type batteries in it, all in series, which makes sense for 12V.
They are marked 1500Ah. For ease of build I would like to change the
batteries to AA type and use 2500Ah ones. Are these a feasible
replacement?

       - Looking at my requirements, which type of batteries should I
use NiCad or NIMH.


Best Regards
               Luis





2009\04\20@051239 by cdb

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Is it the battery packs or the charger?

I'd expect if you had a more intelligent charger, your batteries would
last much longer.

How did this manage to thread itself into the capacitor thread? Upset
my whole indexing system.

Colin
--
cdb, spam_OUTcolinTakeThisOuTspambtech-online.co.uk on 20/04/2009

Web presence: http://www.btech-online.co.uk  

Hosted by:  http://www.1and1.co.uk/?k_id=7988359







2009\04\20@051453 by Tony Smith

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> My requirement is to have at least one battery pack fully charged
> whenever I need it for each drill.
>
> So here are my questions:
>
>        - These are 12V drills, the battery packs have 10 of what it
> seems C type batteries in it, all in series, which makes sense for 12V.
> They are marked 1500Ah. For ease of build I would like to change the
> batteries to AA type and use 2500Ah ones. Are these a feasible
> replacement?
>
>        - Looking at my requirements, which type of batteries should I
> use NiCad or NIMH.


There's a topic that'll last forever.

NiCads are cheap, light, available, tolerate abuse and can be
trickle-charged.  Downside is they self-discharge in a month or two.

NiMh are more expensive, heavier, should be easy to find, don't like being
abused and don't like being trickle charged.  On the plus side the
self-discharge is a bit slower, and they have a higher capacity.

NiCad & trickle-charge might be the easier solution, since you already have
most of the bits.  Your packs will have a dud cell or two, the rest will be
fine, so get replacements or scavenge from another pack.

Most, if not all power tool chargers suck, regardless of brand & price.  A
cheap solution might be rig up a timer to charge the battery at a high rate
for 5,6,whatever hours, and then drop back to trickle charge after that.  A
lot of chargers used to do that, now the cheaper ones are just a
transformer, no smarts at all.

There are now NiMh that take a year or so to self-discharge, Eneloop is one
brand name (from Sanyo, I think).  I don't know how different they are to
normal NiMh in regards to price.  Dunno if you can get them in the funny
sizes that power tool battery packs use (Sub-C, 4/5 AA etc).

Come to think of it, I've a few things in the 'occasional use' category, I
should do that myself.  I wonder if I can charge them off the solar cells
from those garden light things, I've got a pile of them and they're cheap
anyways.  A cell or two & a boost circuit?

Tony

2009\04\20@075117 by Luis.Moreira

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Hi Tony,
Ok so the NiCads seem to be the answer, I didn't know you can trickle
charge them. The charger that came with the drill will apparently charge
the batteries in 3 hours, so it must have a high charge rate is this
contributing to damage the batteries?
I had a look at the battery university site, and it seems to suggest
that my battery packs may not be dead and just need some "exercise" and
" reconciliation", Shall I try that first?
If I go the replacement route I most likely need to go for the AA type
of batteries, I know there is a higher internal resistance but how much
performance will I lose?
Thanks for you help
                               Luis
 




{Original Message removed}

2009\04\20@082854 by olin piclist

face picon face
Luis Moreira wrote:
> I have a couple of battery drills where the NiCad batteries are shot.
>
> - Looking at my requirements, which type of batteries should I
> use NiCad or NIMH.

Probably NiCd since they generally have higher current capability, which is
probably what the drill requires.


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2009\04\20@084027 by Clint Sharp

picon face
In message <00a101c9c1b3$b0b6b340$0300a8c0@main>, Olin Lathrop
<.....olin_piclistKILLspamspam@spam@embedinc.com> writes
>Luis Moreira wrote:
>> I have a couple of battery drills where the NiCad batteries are shot.
>>
>> - Looking at my requirements, which type of batteries should I
>> use NiCad or NIMH.
>
>Probably NiCd since they generally have higher current capability, which is
>probably what the drill requires.
>
The OP also mentioned going down a cell size from C to AA, wondering if
the larger cell sizes have a lower internal resistance and higher
available current?
--
Clint Sharp

2009\04\20@084942 by Carl Denk

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If a battery pack goes bad, I recommend
http://www.primecell.com/howto.htm

We have sent several cordless drill batteries, and they are returned
within about a week. They offer replacing NIcd with Nimh, claim you can
use the same charger, they build something into the pac to allow that. I
have stuck with the Nicd. It has been hard to see where they opened the
case, very minor seam noticed.

Olin Lathrop wrote:
{Quote hidden}

2009\04\20@102949 by William \Chops\ Westfield

face picon face

On Apr 20, 2009, at 4:51 AM, Luis Moreira wrote:

> Downside is they self-discharge in a month or two.

I am very much liking my "lithium" rechargable screwdriver.
Very little self-discharge, and inherent "smart" charging.
Still a bit pricey beyond the screwdriver sized, but ... nice.

BillW

2009\04\20@105725 by Tony Smith

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face
> Hi Tony,
> Ok so the NiCads seem to be the answer, I didn't know you can trickle
> charge them. The charger that came with the drill will apparently charge
> the batteries in 3 hours, so it must have a high charge rate is this
> contributing to damage the batteries?
> I had a look at the battery university site, and it seems to suggest
> that my battery packs may not be dead and just need some "exercise" and
> " reconciliation", Shall I try that first?
> If I go the replacement route I most likely need to go for the AA type
> of batteries, I know there is a higher internal resistance but how much
> performance will I lose?
> Thanks for you help
>                                Luis


Heat kills the batteries, so a high charge rate plus forgetting to turn the
charger off is what does the damage.

One drill I have here is 14v & 1200mAh NiCad, which is fairly low capacity
but typical.  The charger (plug pack) puts out 18v @ 400mA, and recommends a
time of 3-5 hours.  The base would just have a large resistor to limit the
current a bit, not exactly ideal.  

I forget what the recommended rate for NiCad is, probably 1/10 of it's
capacity for 150% of hours.  That works out at 120mA for 15 hours.  The
super-fast rate is 1200mAh for 1.5 hours, which is what the tradesman type
chargers do, or even faster.  I've seen 5A put into 3500mAh packs.  They
measure the pack temperature though, and stop if they get hot.

Trickle is maybe 1/30 or even less, so 40mA forever.  (seems a bit high... I
must look it up sometime.)

So my drill is supposed to be ~400mA (1/3 capacity) for 4.5 hours.  If I
forget, it'll get roasted.

You can make a simple current controlled charger from a LM317 adjustable
voltage regulator, getting it to do 2 different rates shouldn't be hard,
it's just changing the value of a resistor.  With a gentle rate & a timer to
switch from charge to trickle, you could get away with not having the
fancier features, like voltage detection etc.  Of course the timer assumes
the battery is flat, so you may get some damage from overcharging, but so
what if you only get 100 charges less out of something used a few times a
year?

Dodgy eBayers aside, it's becoming hard to get NiCads these days when NiMh
offers 2-3 times the capacity.  Using AA batteries (provided they fit)
should work, it depends on how many amps the drill pulls.  Some NiCads can
put out 30 amps, so it probably will.

If a pack has been left to discharge, running it thru a few charge/discharge
cycles can get it working properly again.  Sometimes one cell gets damaged
so you need to find it and replace it.  Almost forgot, unless you have a
spot welder, you need to buy batteries with tabs so you can solder them.
The tab stuff is hard to buy too.

Tony

2009\04\20@110044 by Tony Smith

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face
> > I have a couple of battery drills where the NiCad batteries are shot.
> >
> > - Looking at my requirements, which type of batteries should I
> > use NiCad or NIMH.
>
> Probably NiCd since they generally have higher current capability, which
is
> probably what the drill requires.


(Good) tools have high-discharge NiMh batteries, these deliver more amps
than NiCad.

Tony

2009\04\20@115329 by Ariel Rocholl

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GP and Kan are examples of NiMh brands that can easily outperform NiCd in
discharge rate. However, Sanyo Eneloop brand proposed above is high internal
resistance and, besides low self-discharge rate, is not good for anything
else and certainly not for discharge rate.

2009/4/20 Tony Smith <ajsmithspamKILLspambeagle.com.au>

{Quote hidden}

> -

2009\04\20@120717 by Michael Rigby-Jones

picon face


> -----Original Message-----
> From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu] On
Behalf
> Of Ariel Rocholl
> Sent: 20 April 2009 16:53
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Batteries
>
> GP and Kan are examples of NiMh brands that can easily outperform NiCd
in
> discharge rate. However, Sanyo Eneloop brand proposed above is high
> internal
> resistance and, besides low self-discharge rate, is not good for
anything
> else and certainly not for discharge rate.

And yet one of the advantages claimed by Sanyo is that Eneloops have
lower internal impedance than typical NiMH cells, and are suitable for
high current discharge.

Regards

Mike

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2009\04\20@121707 by Ariel Rocholl

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I tested that myself and don't get any low internal impedance on Eneloop.
Perhaps that is true when comparing with low end NiMh brands, but if you
compare a 2000mah GP discharge with a 2000mah Eneloop, GP outperforms
significantly.

2009/4/20 Michael Rigby-Jones <Michael.Rigby-Jonesspamspam_OUTbookham.com>

>
>
> > {Original Message removed}

2009\04\20@235415 by William \Chops\ Westfield

face picon face

On Apr 20, 2009, at 9:17 AM, Ariel Rocholl wrote:

>>> However, Sanyo Eneloop brand proposed above is high internal  
>>> resistance and, besides low self-discharge rate, is not good for  
>>> anything else and certainly not for discharge rate.

>> I tested that myself and don't get any low internal impedance on  
>> Eneloop.

What sort of numbers are you talking about?  The candlepower forum  
folk tested Eneloop AA at 4A discharge and got pretty impressive  
results, and also showed "flash amps" at over 12A for cells.

www.candlepowerforums.com/vb/showpost.php?p=2644360&postcount=257
http://www.candlepowerforums.com/vb/showpost.php?p=2188073&postcount=9

That may be low compared to the batteries that the RC crowd likes to  
put in their cars and boats for maximum power, but it's pretty  
impressive in general and would probably work OK in the average  
cordless drill...

BillW

2009\04\21@001308 by Russell McMahon

face
flavicon
face
> I have a couple of battery drills where the NiCad batteries are shot. I
> have no justification to scrap the drills just because of that, as I
> only use them occasionally and they are perfectly fine.
> My biggest problem is that, because I used them sometimes very
> infrequently the batteries are always discharged when I needed them. I
> then left them charging for long periods of time with the charger
> supplied and that's what probably damaged the battery packs.
> Both drills have two battery packs, so I can play a bit...
>
> My requirement is to have at least one battery pack fully charged
> whenever I need it for each drill.


I'd seriously consider lead-acid!
Small SLA.
Float charge.
Moderately good self discharge shelf life.
Moderately OK discharge rate.

And, I'm surprised that BB hasn't weighed in bt now and suggested that you
use LiIon cells fro "dead" LiIon packs. A very good idea if you are willing
to take the effort required,


          Russell


2009\04\21@002253 by William \Chops\ Westfield

face picon face

On Apr 20, 2009, at 9:12 PM, Russell McMahon wrote:

> I'm surprised that BB hasn't weighed in bt now and suggested that you
> use LiIon cells fro "dead" LiIon packs. A very good idea if you are  
> willing
> to take the effort required,

Don't forget the undervoltage protection.  Otherwise, this is a very  
good way to burn out the rest of the cells from the broken LiIon  
pack.  LiIon cells will dump a lot of current into the motor well past  
the point of no return.  By the time the motor stops spinning, the  
cells will probably never charge again (been there, did that...)

BillW

2009\04\21@003500 by Bob Blick

face
flavicon
face
Russell McMahon wrote:
>
> And, I'm surprised that BB hasn't weighed in bt now and suggested that you
> use LiIon cells fro "dead" LiIon packs. A very good idea if you are willing
> to take the effort required,

Hey.

I was driving autocross all weekend and consequently this evening had to
work on my car, so I've been busy :)

But yeah, used laptop packs frequently have lots of good cells in them.
Self-discharge is pretty much nonexistent on Li-Ion. Charging equalizer
schematics using opamp+transistor pairs or power opamps are easily found
on the web, or use a real management chip. Just avoid deep discharge and
you'll have an excellent cordless drill. A bar-graph chip makes it look
very high-tech.

6 cells in series-parallel for 11 volts nominal will probably be a good
starting place for a 12 volt replacement.

Cheerful regards,

Bob

2009\04\21@043423 by Ariel Rocholl

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That is right. For a 2Ah AA size Eneloop 4A sustained, that is only 2C. I
wouldn't call that "pretty impresive results". This is low when compared to
more than 15C a GP can offer (50Amp for a 3.3Ah GP is kind of standard).
This is inline or better than a Sanyo NiCD. Eneloop may be ok for a drill, I
don't know, but if you want to outperform a NiCD, don't think a Eneloop will
do.

2009/4/21 William "Chops" Westfield <@spam@westfwKILLspamspammac.com>

{Quote hidden}

> -

2009\04\21@062915 by Tony Smith

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> >>> However, Sanyo Eneloop brand proposed above is high internal
> >>> resistance and, besides low self-discharge rate, is not good for
> >>> anything else and certainly not for discharge rate.
>
> >> I tested that myself and don't get any low internal impedance on
> >> Eneloop.
>
> What sort of numbers are you talking about?  The candlepower forum
> folk tested Eneloop AA at 4A discharge and got pretty impressive
> results, and also showed "flash amps" at over 12A for cells.


NiCads are higher than that, so are typical NiMh.

It depends on the cell size, from memory an AA Nicad can put out 20 amps, a
C one about 30.  Nimh is about 1/3rd of that.

The NiMh cells used in tools can do 40 amps or more.  Horrible
self-discharge though.

Tony



2009\04\21@092836 by Jeff Findley

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"Carl Denk" <KILLspamcdenkKILLspamspamwindstream.net> wrote in message
news:RemoveME49EC6F64.1030302TakeThisOuTspamwindstream.net...
> If a battery pack goes bad, I recommend
> http://www.primecell.com/howto.htm
>
> We have sent several cordless drill batteries, and they are returned
> within about a week. They offer replacing NIcd with Nimh, claim you can
> use the same charger, they build something into the pac to allow that. I
> have stuck with the Nicd. It has been hard to see where they opened the
> case, very minor seam noticed.

Sounds good, but the prices are a bit steep.  I can buy a new battery pack
for my Makita from Lowes for less than what they want to rebuild.  I'd
imagine shipping and labor come into play here.

Harbor Freight seems to have replacement packs for drills.  But whether or
not they'd fit your drill is dicey.  That and whether or not they use "good"
batteries is surely debatable.

Jeff
--
"Many things that were acceptable in 1958 are no longer acceptable today.
My own standards have changed too."  -- Freeman Dyson



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