Battery testing

[Robert Bruninga]

Save those old Headlamps. The HIGH beam filament is usually still good and
makes an excellent load (near constant current) for battery testing at 5
amps.



I put it on a fully charged (5 year old) 20 Ah battery and it dropped from
13.8 down to 10.75V (the full capacity drop-out point) in 3 hours. Thus
the capacity of the battery is about 15 Ah.



Here’s why I did the test: I had to pre-test some 20 Ah batteries to find
one to carry up a half-mile 300’ hill and then 100’ tower and run my
station for 4 hours guaranteed. Years past, I had lugged along several
batteries (heavy!) to make SURE my station would operate (since I never
have any idea of the capacity of all the junk batteries I have lying
around.)



This year, I PRE-tested my batteries with the headlamps. One was 15 Ah,
another was 14, the third was 10 and the worst was 1 Ah? Wow, my luck
would have been to take the 1Ah one. But this way, I only had to carry the
15 Ah one and had full confidence it would last the entire event.



So don’t carry unknowns into the field. Test them first with a headlamp.



Just a tip,

Bob, Wb4APR