Building a "Smart" battery charger
marty
I was wondering if anyone out there has tackled building a smart charger
for ni-cad batteries. Or if they now of a reasonably priced model
somewhere. Thanks.
--
Marty Scriven
La Verne, CA
sket...@tstonramp.com
Ken Lee
In article <01bcfa8a$9df2d7e0$899a37ce@martycomp>, "marty"
<sket...@tstonramp.com> writes:
|> I was wondering if anyone out there has tackled building a smart charger
|> for ni-cad batteries. Or if they now of a reasonably priced model
|> somewhere. Thanks.
For more info than you are ever likely to need on bicycle lighting
(including smart chargers), see http://cycling.org/mailing.lists/bikecurrent/
--
Ken Lee, ken...@rahul.net, http://www.rahul.net/kenton/
Francois Cau
marty wrote:
>
> I was wondering if anyone out there has tackled building a smart charger
> for ni-cad batteries. Or if they now of a reasonably priced model
You should be able to find some application notes on their site:
http://www.maxim-ic.com/
Bye
--
Francois CAU
Franco...@ensimag.imag.fr //// THOMSON multimedia
franco...@hol.fr (@ @) Grenoble, FRANCE
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Reg_Burgess%AntiSpamPostfix%
In article <01bcfa8a$9df2d7e0$899a37ce@martycomp> "marty"
> I was wondering if anyone out there has tackled building a smart charger
> for ni-cad batteries. Or if they now of a reasonably priced model
I have read some material on this at sci.geo.satellite.nav
There is a lot of knowledge in that news group and a lot of interest in
NiCaDs, "intelligent" chargers, etc. I think there is a web page
reference to schematics, plans, parts lists, etc., though I don't seem to
have bookmarked it. Handheld GPS receivers seem to go through 4 AA cells
in 20 hours or so, hence the interest in rechargeables.
regards,
Reg
Tom Younger
marty wrote:
>
> I was wondering if anyone out there has tackled building a smart charger
> for ni-cad batteries. Or if they now of a reasonably priced model
> somewhere. Thanks.
Check out your local hobby shop which specializes in Radio Controlled
Cars. They will have many NiCad chargers for the cars -- these will
work well with your bicycle light if you get a good charger.
Geoffrey Levand
I was asking for something specific and perfect for my city,
Whereupon lo! upsprang the post of "marty" <sket...@tstonramp.com>:
>I was wondering if anyone out there has tackled building a smart charger
>for ni-cad batteries. Or if they now of a reasonably priced model
>somewhere. Thanks.
>--
Philips has a design app note on their Web site:
AN439 87C751 fast NiCad charger (12 pgs)
Jeffrey L. Bell
Tom Younger <tyou...@gulf.csc.uvic.ca> wrote:
>
>Check out your local hobby shop which specializes in Radio Controlled
>Cars. They will have many NiCad chargers for the cars -- these will
>work well with your bicycle light if you get a good charger.
The problem there is that the voltages don't match up.
Most lighting systems are 6 or 12 V.
Aren't most RC cars 7.2?
-Jeff
Ed Chait
Yes, or 8.4. 12V will make them go very fast, but not for very long:).
Ed Chait
Mike Miller
Do you know the URL for that?
/m
Jeffrey L. Bell
[posted & emailed]
In a previous article, Mike Miller <my...@ibm.net> wrote:
>...
>>Philips has a design app note on their Web site:
>>AN439 87C751 fast NiCad charger (12 pgs)
>
>Do you know the URL for that?
http://www.semiconductors.philips.com/acrobat/8117.pdf
-Jeff Bell
Jeffrey L. Bell
I wrote:
>http://www.semiconductors.philips.com/acrobat/8117.pdf
One thing that I figured out right after I posted the above is that
the 87c751 is general purpose embedded processor rather than a chip
meant just for batter charging. It has an 8 bit 80c51
microcontroller, plus eprom, RAM, and I/o ports integrated into one
chip. To do the battery charging you'll have to find a way of
compiling the C code that they have in the application note and
loading into the 87c51. See 3017.pdf for info on the CPU.
If you want to do tinkering, it sounds like a great way to get started
in experimenting with embedded controllers. On the other hand, if all
you want is battery charger it might be better to go with one of the
benchmarq of maxim chips.
-Jeff Bell
Tom Younger
Jeffrey L. Bell wrote:
>
> Tom Younger <tyou...@gulf.csc.uvic.ca> wrote:
> >
> >Check out your local hobby shop which specializes in Radio Controlled
> >Cars. They will have many NiCad chargers for the cars -- these will
> >work well with your bicycle light if you get a good charger.
>
> The problem there is that the voltages don't match up.
> Most lighting systems are 6 or 12 V.
> Aren't most RC cars 7.2?
>
Yep. But that doesn't matter. Most high end chargers regulate current
-- not voltage.
Giles Morris
> > The problem there is that the voltages don't match up.
> > Most lighting systems are 6 or 12 V.
> > Aren't most RC cars 7.2?
> Yep. But that doesn't matter. Most high end chargers regulate current
> -- not voltage.
I would be careful about following this advice. The idea of a smart charger
is that it charges in several phases. First the bulk phase to quickly
restore the majority (say 75%) of the charge in the battery, then an
acceptance phase to restore the remaining 25%. The float phase is a
maintenance phase to keep the battery charged without cooking it. How does
the charger know what current it should be putting out at each moment?
Simple: It looks at the battery's voltage.
A charger should also be matched to the battery capacity. This is clear
when you consider what would happen if you used a charger intended to put
40A into a large bank of batteries on a small rechargeable button cell of
the same voltage.
Giles Morris
Tom Younger
Giles Morris wrote:
>
> > > The problem there is that the voltages don't match up.
> > > Most lighting systems are 6 or 12 V.
> > > Aren't most RC cars 7.2?
>
> > Yep. But that doesn't matter. Most high end chargers regulate current
> > -- not voltage.
>
> I would be careful about following this advice. The idea of a smart charger
> is that it charges in several phases. First the bulk phase to quickly
> restore the majority (say 75%) of the charge in the battery, then an
> acceptance phase to restore the remaining 25%. The float phase is a
> maintenance phase to keep the battery charged without cooking it. How does
> the charger know what current it should be putting out at each moment?
> Simple: It looks at the battery's voltage.
>
Different types of batteries require different types of charging.
Nicads
are very tough and can withstand and actually thrive on high rate
charging
and discharging. However, gell cells / lead acid are much more finicky
when it comes to charging them in an optimal way. Lead acid like to be
charged with varying rates depending on it's current charged state,
however with Ni-cads you just blast them with power untill their
internal
resistance starts to decrease, or with a sufficient charge current, they
reach a certain temperature above the ambient air temperature. This all
comes from many years of experience using Ni-cads in R/C car racing --
and my batteries have out-lasted everyone elses that I race with. I'm
using batteries 6 years old, and they work just as good as newer, higher
capacity models.
> A charger should also be matched to the battery capacity. This is clear
> when you consider what would happen if you used a charger intended to put
> 40A into a large bank of batteries on a small rechargeable button cell of
> the same voltage.
As I was saying, Ni-cad battery chargers of the type I was trying to
reccommend (but might not have been clear on) regulate current. A
selectable current, so you can charge at any current you want. The
current you adjust depending on the type of cell you are charging --
as a general rule, if the cell is much longer than its diameter, you
use a low current, if the cell is about 2x longer than its diameter,
you can safely use a high current (in the range of 5 - 10 amps) and
if the cell is much shorter than its diameter, you again use a lower
current (0.5 - 1 ampere).
However, this is just advice that I have from many years of using
NiC-Cads in demanding circumstances with high discharge
characteristics -- nothing I say here you will find reccommended
by the manufacturer. However, what I do works better for me with
the application I use the batteries in than the manufacturers
reccommendations -- of course YMMV.
James Hadley
"Giles Morris" <No.Mo...@Spam.federal.unisys.com.Spam> wrote:. How
does
>the charger know what current it should be putting out at each moment?
>Simple: It looks at the battery's voltage.
Actually, the RC chargers under discussion DON'T look at battery
voltage per se. They are "smart" in that they sense when a battery is
charged and shut off. They do not "maintain" a battery. they sense a
full charge either by a slight drop in voltage (the behavior of Ni Cad
cells when they are fully cherged) or by the heat that is produced by
a fully charged pack - most often though by the voltage drop. It does
not matter what the voltage of the battery is. The same RC chargers
are used for 4 cell (1/12 scale racing) which is a 4.8 volt pack as
for 1/10 scale modified - whcih used a 7 cell (8.4 volt) pack. The
charger "peak detects" just as well on the 4.8 as the 8.4 volt pack.
The batteries vary from 1200 ma to 2000 ma batteries. It also works
equally well on this range of cells. I'm not sure of the
capacity of lighting NiCads and don't mean to speak to those - but
these are the facts of RC "peak detecting" or "smart" chargers.
Jamie
Giles Morris
James Hadley <jpha...@mail.bcpl.lib.md.us> wrote in article
<664o1j$hdo$1...@news.abs.net>...
>> How does
> >the charger know what current it should be putting out at each moment?
> >Simple: It looks at the battery's voltage.
> Actually, the RC chargers under discussion DON'T look at battery
> voltage per se. They are "smart" in that they sense when a battery is
> charged and shut off
Thanks for the clarification. I guess there are different definitions of
"smart"
Giles
Rc chopper
>I was wondering if anyone out there has tackled building a smart charger
>for ni-cad batteries. Or if they now of a reasonably priced model
>somewhere. Thanks.
>--
I Fly Rc helicopters and I depend on my batteries and chargers. The best
charger on the market is the Alpha 4 by litco.
It is ten units in one. It can cycle batteries 3 ways, it will peak, trickle,
fast, C10, or slope anaylize charge a battery. It handles upto 36 cells, its a
load meter, it will charge gell cells and metal hydride, and it handles 4 packs
at a time. It cost 200.00$ and they are back ordered. 717 689-7835 in NJ
No i don't have any affiliation i just love the product. Most serious RC heli
pilots use them and we have to trust a very expensive and dangerious heli to
our batteries.
Rc Cho...@aol.com :~`)
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The Dumbest questions are often said in silence.
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