Charging lead/acid batteries
How to charge batteries
This subject has multiple answers. I chose to go with what the manufacturers recommend as I am not too keen on replacing the 50+ batteries within the next two years. Both Yuasa and Hawker (Cyclon) recommend a constant voltage and a current limiter. A constant current charger forces the battery to charge at a predetermined pace. The battery pulls a few amps at the beginning and then charges until it reaches about 13V, after that de decline in current is very slow. During this time the battery is getting it's actual capacity.
The circuit for this charger is found on my Battery Charger page, it uses a regulator and current limiting circuit. It is very easy and cheap to build, but be sure to cool the regulator well with a good heat sink if you are using it to charge filament batteries. For B+ the current should be quite low as most tubes don't pull a lot of anode current.
Another question is whether it is advisable to charge the batteries of the B+ with a single charger while they are connected in series. I think this is not a good idea as each battery has it's own Ri, which is different from the other batteries. This will cause certain batteries to charge fully while others are only at 70-80%. When playing these batteries, they form the weak link in the chain and eventually be worn down faster than the other batteries.
It is much better to charge the batteries seperatly. This will see to it that each battery reaches 100% at it's own pace, but does get there eventually. This means a seperate charger for each battery is required. If you do not want to make so many chargers then an option would be to connect a few batteries in parallel to the same charger. I would not do more than two or three as you have similar problems to the series charge method.
The battery should be charged at 13.5-13.8V and current limited to 1/10th of the capacity (i.e. a 10Ah battery should be limited to 1A of current).
© Jim de Kort