Semi-technical charging question

[extremeR1der]

I've been using a 4 AA custom charger to charge my dual cells. It's fairly inexpensive and so are batteries, so I've just been kinda winging it with charge times.

Now I'm looking to either buy or make a charger that I can use for more than just BCG's.

Going by actofgod's advice:
"2) Each adapter has a different current that it delivers, in mA. To figure out how long (in hours) you need to charge with a given current, divide the capacity of the batteries (40mAh) by the charge rate in mA. (ChilledOut says that rechargeable AA's put out about 1000mA if you're using them for a custom AA charger instead of using an AC-to-DC adapter.) Multiply by 1.2 to account for inefficiencies in the charging process, then multiply by 60 to convert to minutes. Finally, multiply whatever follows the decimal point by 60 to get the seconds.

Ex: using 300mAh charger, 40mAh / 300 = 0.13333
0.13333 * 1.2 = 0.16
0.16 * 60 = 9.6 minutes
0.6 (the part after the decimal in 9.6) * 60 = 36
final answer: 9 minutes, 36 seconds"
Layman's linky

It should be as simple as finding an adaptor that has variable voltage and either has or can be modded to have amperage regulation.

In my search for out of the box chargers, I've come across many that are not suitable for NiMH batts and many that ARE suitable for NiHM batts.
My question is simply: Why?

I wouldn't feel confident making a custom charger if it was harmful for NiHM batts (remember this will be used for more than just BCG's).

[Buzzbait]

I can't answer your question, but can make a recommendation. The Piranha Digital Peak Charger seems to be held in very high regard, and won't blow your wallet either.

[extremeR1der]

Thanks, Buzzbait!

It looks a little better than the one I was initially considering and it costs about the same.
http://www2.towerhobbies.com/cgi-bin...?&I=LE2269&P=1

The Piranha has a better display and you can increment the charge rate in 100mAh steps. versus the 500mAh steps in the MRC.

Nice recommendation

[cowfish_29]

The description of the pirhana Peak charger says that it will charge batteries from 50mah to 5000mah. The little button cells are 40mah.... is that a problem?

[Namuna]

Using a Peak Charger is a great idea because it handles everything for you. Just tell it the charge rate and the charger automatically monitors the voltage and stops charging when it detects the 'peak'.

Just be careful when buying to remember that Peak Chargers are usually geared for 'at the track' setup. Which means they don't just plug into the wall AC...Like these Piranha Peak Chargers, unless you've got a spare car battery hanging around to connect to, you'll have to buy a Power Supply for it.

[Buzzbait]

I believe that the Piranha I mentioned ships with an AC adapter. At least that's what it looked like when I viewed the online instruction manual.

[extremeR1der]

Thanks for the replies, guys.

..but does anyone know why some chargers are not suitable for NiMH batteries?