I use only Battery Tenders on all my rides, 3 BMWs, others vehicles and on and on.
I use them and other like CTEK I think that is right because they do measure the voltage and have a good algorithm for not overcharging the battery and keeping it topped off to a full charge.
As proof I have my M3/4 which doesn't get driven much with a Batteries Plus battery from 2004. It is just fine. My E93 is 5 1/2 years old, my two diesel truck batteries were over 6 years old each and were just your run of the mill Durolast when I changed them out for Optimas.
I have the Sear battery charger and that is good for a good amp charge but not trickle charge. The ones Walmart sells too I tried and they lasted about one season so in the long run I use the battery tender and have for a long time now since about 2002.
CTEK is another company making quality chargers and the BMW model is also an intelligent charger. By the way I never buy the full size battery tender because my cars and trucks sit for days to weeks and the battery tender junior is cheaper and does the job just fine. I have 5 of these and none have failed and all are currently working charging my vehicles.
Hope that helps and didn't want to come on too strong for the battery tenders but any of those intelligent charging models is the way to go. On my BMWs and diesel truck I leave the battery tender junior in the engine bay and just run a cord to the bay. Has had no ill effects in my BMW M3 bay for the last 10 years so a little heat doesn't seem to hurt them...
Last edited by fun2drive; 10-10-2012 at 06:39 PM.