Anyone know exactly how a "smart" batt charger works?
terahertz
Posts: 55
I'm to the point where I need to·buy a power source for my project. I had originally planned to use a deep cycle marine battery but it needs to be in a sealed container and I don't want to deal with potentially explosive outgassing issues.
After some research I ordered some of the new generation high power·NiMh rechargeable batteries. I ordered 10 cells at 12,000mAh each·at 1.2 V, for a total of 120Ah, 12V when wired in series. With 120Ah of reserve power that is way more than I could get from a lead acid deep cycle marine battery.
So far so good, but I ordered the batteries before I looked into chargers.· It turns out·a charger capable of a 120Ah-12V charge is EXTREMLY expensive, or·I can charge the cells one at a time, which will take literally days.
My question to ya'll: I would like to be able to use my bench-top power supply to charge·these batteries all together in series, but·I obviously don't want to damage them. I'm willing to build whatever circuit I need to accomplish this. I assume a "smart charger" is just some sort of voltage comparator and current limiter???
Does anyone know for sure, or have any ideas?
After some research I ordered some of the new generation high power·NiMh rechargeable batteries. I ordered 10 cells at 12,000mAh each·at 1.2 V, for a total of 120Ah, 12V when wired in series. With 120Ah of reserve power that is way more than I could get from a lead acid deep cycle marine battery.
So far so good, but I ordered the batteries before I looked into chargers.· It turns out·a charger capable of a 120Ah-12V charge is EXTREMLY expensive, or·I can charge the cells one at a time, which will take literally days.
My question to ya'll: I would like to be able to use my bench-top power supply to charge·these batteries all together in series, but·I obviously don't want to damage them. I'm willing to build whatever circuit I need to accomplish this. I assume a "smart charger" is just some sort of voltage comparator and current limiter???
Does anyone know for sure, or have any ideas?
Comments
read this thread:
http://groups.google.com/group/rec.bicycles.tech/browse_thread/thread/150f4cf2e4c44cf3/995cd9818a8cf133#995cd9818a8cf133
scroll down until you see the post by Giles Morris it gets good starting there.
A quantity of (10) 1.2 Volt 12 Amp-hours cells put in series gives you 12 Volts at 12 Amp-hours NOT 120 Amp-hours.
Bean.
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Cheap used 4-digit LED display with driver IC·www.hc4led.com
Low power SD Data Logger www.sddatalogger.com
SX-Video Display Modules www.sxvm.com
"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·
You are correct Bean
Why buy when you can build?·I suppose I could use a BS2 as some sort of current controller. If I can figure out what makes a smart charger smart.
Bean.
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Cheap used 4-digit LED display with driver IC·www.hc4led.com
Low power SD Data Logger www.sddatalogger.com
SX-Video Display Modules www.sxvm.com
"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·
After some poking around, it seems like NiMh cells exhibit a brief 20mV drop when they are fully charged,·"smart" chargers then go into a trickle charge mode when this drop is detected. I've already got 2 ADC's mounted on my BOE. I just need to find that·AC relay board I have somewhere and I have my own BS2 "smart" charger.···· Hey, a mini-project!·
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Don't visit my new website...
·Computer driven,no BIG transformer,very light,will do:
·Lead Acid Std kind···· Desulfate··· Alternator check!
2 / 10 /25 /75 Auto
·WET/GEL/AGM··· mode
·got it from SAMs club!· Made by POWER on BOARD·· Smart battery charger #VEC 1095 APOB····· DSC microprocessor Digital smart control!
Vector manufacturing,ltd
·FT,lauderdale,FL,33312
·Nice unit, something to play with!
There are plenty of NI-Cad charging stuff around,the only difference is this kind of battery don,t have the memory problems ni-cads do!
·do a search on google for smart Ni-cad charger!
Cheers Dennis
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http://people.delphiforums.com/cocokiwi/Image/picture.jpg
You can easily by Lead Gelcels that don't have the gasing problem and they both retain a charge for longer periods than NiCad or NiMh and they survive better on a long-term trickle charge. That outgasing is a large part of why they went to the gel.
A smart charger is usually a 3 mode charging device. Though it would be wonderful if it also included a thermal shut down as overheating during charging is likely to be the biggest wasteful destroyer of battery life.
The modes are usually an intial charge mode, a fast charge mode, and a trickle charge mode. The idea here is to not damage the battery by immediately putting it unnecessisarily into a fast charge. If it is not deeply depleted, the intial charge rate may be enough to top off the battery. Fast charge is for batteries that are more depleted. The trickle charge is obvious.
As you can see, the smart charger is all about rate. Still, the darn things are not smart enough to have one size fits all batteries. Chargers need to be matched to what they are charging as charge rates are determined in ratios to the amp/hours of the battery.
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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
I do not know if this will help you
This is·the battery charger that i have used in the past
This comes as a kit that you built your self a very easy kit to put together
At this web page
With this charger you charge one battery to 12 battery with a·dip switch and you select charing rate from 250 milamps·,500· 750 ,to one amp
That you hard wire select
http://www.gibsonteched.com/R-DN1.html
Sam
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Chris Savage
Parallax Tech Support
As an R/C flyer I use NiMH packs and my charger advertises that it fast charges to 95% capacity the does two hours of trickle charge to top off. How much is hype? I can't tell the difference in flying time.
And it does so until I remove the batteries.
(Yes, I have had them in the charger for a week with no noticeable effect.)
They call it 'top-up charging' but that's just what Trickle-charging is supposed to do, anyway...
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Don't visit my new website...
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Chris Savage
Parallax Tech Support
When I get it and test it, I'll post on this thread·how it works.
The confusion probably comes from the fact that most chargers are not specific to the battery type, yet the batteries themselves have different charging characteristics (NiMh,NiCD,LioN).
Do you know if anyone actually built one? It seems like it would be a fairly·easy and usefull thing to make. Maybe I'll put that on my list, I have 5 projects due to myself/others/school by the end of the month.
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Chris Savage
Parallax Tech Support
Something to keep in mind....many types of batteries, none of them charge the same (duration and intensity)....
It's hard to do immediate damage to a battery by charging it wrong (within reason) but prolonged and repeated 'wrong-doing' will kill it.
We have a lot of remote stations that use solar/RV batteries to keep them going. A lot of the guys will try to 'equalize' the battery because they were told it will extend the life!
More often than not, the batteries died because of this. Either because the batteries were equalized too long (and the electrolyte evaporated or the casing cracked) or it was done too hard (too high current) and the plates warped and killed a cell.
Anyhow, IMHO the most 'cheaper' chargers really only trickle charge a battery. You have to pay for the benefits of 'smart' chargers....but what the 'more' that they do isn't all that fancy, but how they do it is (microprocessor controlled PWM chargers..etc..).
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·
Steve
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
· ^ what he said
The idea is the a steady flow of electricity does not allow the physical chemistry of the battery to properly organize and restructure the molecules on the plates. It may be that it also eliminates accumulation of heat created by internal resistances during the charge
By pulsing it, you charge a little and wait a little -- but in the end you come up to charge sooner and have more battery life.
Of course the theory of battery charging has to be compared with the harsh reality of users just pluging and unpluging whenever. Also, user leave batteries on the dashboard of their car [noparse][[/noparse]too hot an environment for storage] and run them down to near zero [noparse][[/noparse]for recharge they should be used to about 50% onlly].
So.... what good is a smart charger with a dumb user? {forgive me, but it was just too easy to make that statement}
BTW, I see lots of advertizers tht tout 'smart chargers', but none will actually explain the superiority of their inteligences. I have my doubts that you are getting your money's worth. Most of this feels like the marketing department created a perception of additional value. Look at where Sony is today with Lithium batteries -- a $94,000,000 loss.
I have gone back to lead gel cells as they are well documented for surviving use and abuse while holding a charge in storage the longest. Seems at least a path to buying less heavy metal devices over the long haul.
The Art of Electronics has a good introduction to comparing the different kinds of batteries.· But for me, it is far easier to manange only one kind than to deal with all the information.· It becomes like keeping a wine cellar.· You have to enjoy watching your inventory.· If I have a special need [noparse][[/noparse]like my PDA], it is mated with a special charger.
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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
Post Edited (Kramer) : 11/9/2006 3:52:35 PM GMT