3000M H batteries

[Bootlegger]

 Guy's I have some 3000 M H batteries coming and I plan to use 10 of the 1.2 volt to make a 12 volt starter battery.  What is the proper (safe way) to charge these batteries?  Thanks...

[FLOYD CARTER]

What is M H?  Metal hydroxide?    You indicate 1.2 volts each, indicating they are NOT lithium.  Therefore, normal charging of NiMH or NiCd cells is a constant current charge at 1/10 the indicated mAh.   

Connecting 10 in series gives a terminal voltage of 12 volts.   To get a constant current charge, the charger must be of a higher voltage. For instance, if the charger is 24 volts, open circuit, the difference between charger voltage and battery voltage is 24-12= 12 Volts.  Connecting that charger to the 12 volt battery requires a series-connected resistor to set the charge current.  That resistance equals The difference in voltages divided by the desired charge current.  In this case, charge current should be 300 mA.

The resistor would be (24-12)/.3= 40 Ohms.  The power rating of the resistor is I sqrd X R  or .3 X .3 X 40=3.6 Watts  (use 5 Watt size)

Similar calculations apply to the open-circuit voltage of  your charger.

[Fred Underwood]

Or, use a charger that is compatible with the chemistry, probably NiMH as noted.  Many of the chargers on the market now are multi-chemistry capable.  Most of the Li-Poly chargers will do Li type batteries, and NiXX and Lead acid.  They also have circuitry for auto shut off or trickle.

[John Rist]

What Fred said.  If you need a charger I have had good luck with Thunder Power chargers.  They will handle all types.

https://www.thunderpowerrc.com/collections/chargers/products/thunder-power-rc-100w-10a-ac-dc-charger-tp610hvc

This one is AC & DC powered and handles one battery pack at a time.

I fly electric so I bought the 4 battery TP charger.  Love it! 

[Bootlegger]

 I guess that I need my head examined again, these are ni cad batteries and I failed to post that info, please do not shoot!!!

[Dan McEntee]

   Are you sure they are NiCad? At 3000Mah, I don't think there was ever a NiCad sub-c battery that had that capacity, and they might in fact be nickle metal hydride? Either way, you just need a common charger that has been produced by the millions over the last 20 years that is capable of charging up to 10 or 12 cells. Probably hundreds of thousands of them sitting idle in basements and garages all over the country. Countless numbers of vehicles that ran on twin 6 and 7 cell packs have been marketed. Seems to me that we have been down this road before and that you have acquired one of those? These were typical for R/C cars and airplanes before Lipo batteries came along. You just need to decide of what connector you require for that much current and equip your charger, battery and starter with them in the proper manor. 
  Type at you later,
  Dan McEntee

[FLOYD CARTER]

Of course, some chargers used by electric flyers will work with NiCd, NiMH, or LiPo types.  Make sure NiMH capacity includes 10 cells.

My suggestion was for a home-brew charger.  (I made my own charger)


and BTW, you charge NiCd and NiMH cells the same way.