[NLRS] Battery charge regulator

[tosca005 at umn.edu]

Well, I managed to "cook" one of my 31 AH gel cell batteries while trying 
to recharge it. It didn't explode or rupture spilling acid all over the 
place, but the case sure looks funny as it pushed outward from internal gas 
liberation. Fortunately, it held together without cracking open, but...

Anyway, not wanting to repeat that experience, I am looking for a battery 
charge regulator. I realize that a 1.4 ohm 150 watt resistor in the 
positive lead of the (replacement) battery would limit the charge current 
to about 10 amps, but it would also limit the drain current to the same 10 
amps or so, which is not enough when roving when some of the "low 
microwave" amps kick into high gear. I would like a device or circuit that 
would limit the charging current into the battery to whatever is optimal 
for a gel cell battery, but not limit how much current is drawn out of the 
battery under severe load.

An even tougher need is a way to put two 12v gel cells in series to provide 
24 volts at high current for a few of the amplifiers that need 18-26 volts, 
and still be able to safely charge the pair of batteries from the vehicle's 
12 volt electrical system. I have a 12V to 24V inverter that can deliver 
about 30 amps at 24 V, but some of the amplifiers want even more than 30 
amps when driven to the max. I figure that a pair of healthy gel cells in 
series could provide all the current I need for short periods of time, as 
long as I can keep them properly charged. Using the 12-to-24V inverter 
output across the series-connected 12V batteries would potentially work, if 
not for the problem of lack of charging current regulation leading to 
another catastrophic battery failure, which would not be nice on the road.

Ideas, anyone?

73 de W0JT