I've been using the one that Frank sells in my car and I really like it. It is small, light and plenty powerful for my needs. Mine runs the transbrake, 2-step, Racepak and the shift light/tach converter. The Racepak records battery voltage and I'm seeing 20V when they are fully charged. Everything listed above works fine at 20V. I have two batteries so that I can swap from run to run or just use one for a back up.