I have two 5volt @ 2amp switchmode plugpacks and would like to make a battery charger able to charge 2 AA NiMh batteries, They are 1.6amps each.. I would also like to include a feature to be able to select the charge rate (slow/normal/fast) anyone know of a circuit?? I have looked EVERYWHERE for a circuit.. well, nearly... also, a timer would be good... a simple one to select the charge time.. anyhelp would be GREAT!!
Try Maxim
a circuit featuring these MAX712, 713 etc. chips was a staple in the ARRL Handbook, you can find it here at Maxim's site:
http://www.maxim-ic.com/quick_view2.cfm?qv_pk=1666
a circuit featuring these MAX712, 713 etc. chips was a staple in the ARRL Handbook, you can find it here at Maxim's site:
http://www.maxim-ic.com/quick_view2.cfm?qv_pk=1666
Ok thanx, I think I saw it before... or maybe not... Anyway, my problem is (I have many, but not relevent to this project 😀) is that I am not sure if I can connect the cells in series due to the lowish input... one schematic I saw needed 7 volts I think to charge to cells in series...
NiMh can be tricky to charge properly. Usually they use a microcontroller, and monitor voltage, current and temperature. They are very sensitive... ...you can charge them with a simple power supply, but will shorten the life/capacity of the cells.
-Dan
-Dan
The max713 is very foolproof. Monitors dv/dt, Icharge, switches to trickle charge and has a timeout. If I remember you need 2V more than the max voltage during charge. So for 2 cells that would be 2V+2V+2V=6V. So a 7V adapter would be right.
Never charge cells in parallel! They will always charge uneven.
Never charge cells in parallel! They will always charge uneven.
Havoc said:
Could I use 2 controller ICs and have a seperate circuit for each cell... I only have a 5volt plugpack.... I bought it with teh hope of making a battery charger.. 🙄 I already had the batteries... I bought then 2 years ago, but had no way of charging them... 🙄 The reason I want to use the 5volt plugpacks is bacause they are small, very small, and give 2amps out, which is good.... I suppose I may be able to modify one to get 7volts, rather that 5.... A voltage divider on the feedback line.... but I can't even get it open.. 😛 lol 🙄 They are well regulated, they still give "5 volts" (about 5.2volts) even with a 2.1amp load..... So, I think these were a good find at only $5.50AU... 🙂 🙄 I only bought 2.... I was going to buy 5.... or... what else could I do with them?
the MAX713 is a little expensive to use 2 of them -- about $7 -- but with Maxim you get a lot of utility for the USD or AUD.
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