Hi everyone,
I bought some rechargeable 9V NIMH batteries, only problem is my charger can only charge AA and AAA.
They are 200mAh and list the standard charge as 20mA for 16 hours. Do you reckon I could charge these using a lab power supply with current limiting?
Also, for a longer term solution, does anyone have a simple charging circuit that would be suitable? Bonus points if it charges from a solar panel... (I have some spare ones from garden lights)
Hi everyone,
I bought some rechargeable 9V NIMH batteries, only problem is my charger can only charge AA and AAA.
They are 200mAh and list the standard charge as 20mA for 16 hours. Do you reckon I could charge these using a lab power supply with current limiting?
Absolutely. I do that all the time for custom NiMH packs.
Also, for a longer term solution, does anyone have a simple charging circuit that would be suitable? Bonus points if it charges from a solar panel... (I have some spare ones from garden lights)
Don't stuff around with other chargers. This is the one to get,
http://www.mahaenergy.com/mh-c490f-9v-charger/I switched to 9V (8.4) NiMH for my guitar wireless back in 2006. I went through a lot of batteries before I recognised that the chargers were destroying my batteries. I bought the c490f in 2010 and I've not lost a battery since (I have 4 batteries and average one a week - so that's about 52 cycles each thus far). I have a MH9000 for AA & AAA cells and I love that also, but the c490f is a winner. I bought some 9.6v powerex LSD batteries recently and man what a difference.
The c490f will charge from a car battery (so ~11-16v) so you'd probably be ok on a solar cell.
Hi everyone,
I bought some rechargeable 9V NIMH batteries, only problem is my charger can only charge AA and AAA.
They are 200mAh and list the standard charge as 20mA for 16 hours. Do you reckon I could charge these using a lab power supply with current limiting?
Also, for a longer term solution, does anyone have a simple charging circuit that would be suitable? Bonus points if it charges from a solar panel... (I have some spare ones from garden lights)
You don't even need current limiting, just a series resistor and a good stable voltage. The resistor will limit current to I = (V
powersupply - V
battery) / R. As a bonus, as the battery voltage rises due to charging, the current will decrease due to a lower voltage difference, so you can get a nice taper down to a constant trickle charge by choosing an appropriate V & R.
Thanks for the replies guys.
You don't even need current limiting, just a series resistor and a good stable voltage. The resistor will limit current to I = (Vpowersupply - Vbattery) / R. As a bonus, as the battery voltage rises due to charging, the current will decrease due to a lower voltage difference, so you can get a nice taper down to a constant trickle charge by choosing an appropriate V & R.
I ended up doing this because a 20mA current limit is too small for my power supply to accurately regulate. It would limit at 10mA then jump up to 30mA, so I left it at 30mA and placed a 150ohm resistor in series. It's very close to 20mA now.
can use LM317L in constant current mode - example circuit
here