BB. wrote: »
At the very least, it is recommended that batteries in series should be relatively close in AH capacity.
For testing, it is not going to hurt anything... For long term, you might have problems with equalization (some batteries may undercharge and others over charge in the string--depending on capacity, leakage current, etc.).
Equalization can make batteries all 100% charged--but it does this by overcharging some batteries to bring the "weak" ones back to 100% charge.
Over the long term, equalization is pretty hard on batteries and should only be done when needed (for example, when the range of specific gravity is 0.030 or greater from lowest to highest cell).
Normally equalization is done once every 1-3 months or so for flooded cell batteries. Some companies recommend equalization every 2-3 months, and others only equalize when needed.