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I have sears 19.2 volt portable tools ,well the batteries are going bad.So I was looking around and found 19.2 volt 3 ah. ni-mh batt. for the same price as the 19.2 2.0 ah. ni-cd,I read that the ni-mh are less prone to have memory conditions,I also read that you can use a ni-mh charger to charge ni-cd but not the other way.My question is I have a lithium/ni-cd multi chemistry charger .should that be able to charge ni-mh batteries? Well I have used it to charge the batteries once and there was in my opinion normal charging warmth on the battery and the charging time seemed to be correct.What I have read there is something about sensing small voltages to turn the charger to trickle that is a issue on some chargers,but I have seen no references to trying a lithium type charger ,what also I have read that lithium batteries are really sensitive to heat so should'nt it have the protective circuitry?
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The lithium batteries require a special charger. Some of them have a third wire for sensing and some also sense for temp. A charger for ni-cad and ni-mh batteries sense the voltage peak and cut off the charge to a trickle charge, at least the chargers for my model aircraft do that. There is also a difference in the charge rate for all three batteries. Some ni-cad/ni-mh don't have a cutoff feature and keep charging at full rate and they need to be monitored all the time. The best way with those chargers is to have a battery fully discharged and then charge it for the length of time that the voltage and capacity of the battery requires and unplug it at the end of that time frame other wise the batteries will over heat and be damaged.
Unless the charger is designed to be able to charge each type battery it should not be used.
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