I am looking for a charger for a B & D modelKC144BP 14.4 V battery

14 volts charge is correct. Standing voltage on a good fully charge battery is 13.2 volts or so. I check one on charge with a 6 amp charger and it was 14.2 volts. It dropped to 13.8 with charger off.

Connected in series the amperage is still 14 and the voltage is 36. Connected in parallel, the amperage is 42 and the voltage 12.

A load tester is typically a resistance pack with an amp gauge to see how the battery deals with current draw. most automotive parts stores have one to bench test car/motorcycle batteries, which they do at no charge (pardon the pun).

Batteries can have a "surface charge"(voltage) which will supply low current at the specified voltage from a battery with bad cells, but when a real operating load, such as for an electric motor, the charge drops to zip..

If the charger is putting out voltage to the battery while it's plugged in then it would definitely be a battery issue, generally the charging system for electric wheel-chairs has regulatory circuits to prevent over charging so having one plugged in when not in use typically doesn't cause issues.

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Absolutely. NiMH batteries are direct replacements for Nicads - in use and in charging.

I am not sure you are asking what you really want to know

This will be a 12 volt dc system
The battery AMPERAGE will be labeled on the battery generally some where around 750 to 900 Cold Cranking Amps
Amps will have nothing to do with charging the battery
A battery CHARGER will have a MAXIMUM amp output Most lf them are 4 to 10 amps on a slow charge

Probably a weak connection. Clean the clamping surface and the battery connection surface and try again.

Yes you can charge the 12 volt bttery on a trickle charger. You should use a 1 amp or less charger. Check the battery every 1/2 hour or so for heat. If it get's hot you should stop charging. Power packs that have a 12 volt rating will charge your battery safer and better but will take longer (like a cell phone charger) look at the voltage ratings on the charger. You will have to adapt the plug to hook it up and test for correct pos. and negative connections. The 7amp hour batery should be fully charged by a .5 amp (500ma) charger in about 14 hours (multiply the amps times hours of charge and do not go over the 7amp hours of the battery when deciding how long to charge). After charging check voltage, it should be around 12. Let the battery set for a few hours (overnight) and check the voltage again. It should be around 12 still. A fresh charge will usually show a higher reading (called a surface charge) than a battery sitting around. 4.5 v will not operate your device, 9.5 v or higher should.