Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Rechargeable Batteries

Status
Not open for further replies.

yash gupta

New Member
I want to know that what does 'mAH' or 'AH' mean in rechargeable batteries.
What does it tell us about the max current, the charge and discharge time?

Please if anyone knows it, tell me.
 
Thanks. I got the answer.
mAh is a measure of the amount of charge stored in a cell or battery (set of cells). One (1) Ah is the equivalent of 1000mAh, and so the statement can be made that a cell with 2000mAh of stored charge can supply a device drawing one (1) mA for 2000 hours -- before needing replacement or recharge.
 
Hi there,

The max current though is usually obtained from the manufacturer. For NiMH this is usually pretty high, but for Li-ion you really have to stay at or below the manufacturers recommendations.
 
Thanks. I got the answer.
mAh is a measure of the amount of charge stored in a cell or battery (set of cells). One (1) Ah is the equivalent of 1000mAh, and so the statement can be made that a cell with 2000mAh of stored charge can supply a device drawing one (1) mA for 2000 hours -- before needing replacement or recharge.

hi,
I suggest that you also look at the conversion efficiency for charging batteries compared to the discharge time/rates, its not 100%.
 
A 2000mAh battery never has the full 2000mAh.
 
Last edited by a moderator:
A 2000mAh battery never has the full 2000mAh.
Ni-MH cells are used at very high currents and the capacity doesn't drop.
Here is an AA Ni-MH cell from Energizer:
 

Attachments

  • AA Ni-MH cell high currents.PNG
    AA Ni-MH cell high currents.PNG
    49.8 KB · Views: 211
Li ion batteries

Thanks!
Now I have another question.
There is a small white rectangle present on the side of a li-ion battery, where it has the terminals.
What is it used for and what does it indicate?
In a new battery, I saw it white. In an old one, it was almost black and in another, equally old, it was magenta.
It seems that it indicates the health of the battery. Is it so?
And why are there 3-4 terminals present on a li-ion battery, when only 2 are req.?
And 1-2 of those show no voltage at all.Liion.png
 
Last edited:
I think it is some pressure control thing,etc. Am I right?
 
Last edited:
Be polite and at least make an attempt to Google the subject yourself. Then if not clear ask your questions
 
I tried. And even wikipedia has no answers. If you have foound the answer on google, tell me also. And i'm sorry if you think i'm wrong.
 
Hi there,


I dont think this has been mentioned yet, but some NiMH batteries are better than others. This comes about because of two different specifications, which by the way are not mentioned in any of the ads for the products. We know about the 'cell capacity' rating, which is typically 2000mAh or 2200mAh or similar, but another rating that is not mentioned in any of the ads for standard NiMH cells is the 'capacity retention' rating. This turns out to be a very important rating which needs to be looked at in order to determine absolutely whether or not a given cell will fit your application or not. If this rating is ignored, you may end up with cells that you simply can not use for what you intended to use them for.
Charge retention is the ability (or length of time) of the cell to HOLD a charge once it has been charged completely.

Case in point: Energizer 2500mAh NiMH cells. There have been a million complaints about these cells in that once they are charged completely they quickly loose their charge so even the next day they may not hold more than 50 percent of the original charge. I would not have believed this could happen so fast until i actually had this experience myself and asked Energizer to take them back. Energizer was understanding though and sent me a coupon for 10 dollars USD so i could go buy another product instead. Just to note however they did state that there was no known problem with the 2500mAh cells, so that was typical operation. Was it really just a set of bad cells? I would think so if so many people didnt have the same 'problem'. Was it fixed? I wont buy another set to find out, but instead turn to a new type of cell to recently hit the marketplace...

"Low Self Discharge" NiMH cells (or LSD cells) are cells that hold their charge for several months and loose only a small amount per month. After several months the cells are still very much usable as they still hold much of their charge. These cells are really great. The drawback? The highest capacity at the date of this writing is only around 2000mAh, but that's still very good when you consider that they loose very very little charge in a week.
Case in point: Kodac low self discharge cells. I actually tested four of these cells over a 6 month period and found them to perform exactly as stated by the manufacturer. The charge retention was exceptionally good, meaning that even after a year the cells would still have plenty of charge left in them.
Other manu's:
Sanyo, makes one of the best perhaps, named "Eneloop Cells", comes in colors but the colors may not be available in the US yet (maybe in Europe).
Rayovac, i think they called these "Hybrid Cells".

By the way, these cells come in the package ready to use unlike the standard NiMH.

If you are planning on using NiMH cells for anything you should certainly look into these kind of cells first.
 
Last edited:
It was probably an indicator code for the maker of the battery, it could be an age indicator like you suggested, it'd be easier to slap a sticker on the side than it would be to put a date code on the pack.
 
I have used Energizer Ni-MH AA cells for years and never had a problem. They are made for Energizer in Japan, maybe by Sanyo.
The originals were 2100mAh then 2500mAh, then 2450mAh and labelled "holds charge 40% longer than cells sold in 2005", then 2300mAh and labelled "charge retention 6 months, charge up to 150 times more than Energizer AA 2450mAh cells".
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top