Posted by JRP on 05/21/15 - 8:40 AM
#11
Gmondun wrote:....unless I'm in an emergency situation to get enough power.
Regarding the emergency situation... it depends.
If one of your batteries has been deeply discharged, you would NOT want to use the "ALL" switch setting. That is because the bad battery will drain power from the good battery until they are equalized. Soyou would not combine them, insyead you would keep them separate and select only the good battery to start the engine. Once they engine has been restarted, you can combine them again and they will both charge.
However, if both batteries have been equally deeply discharged, and you are trying to re-start the engine on a prayer, then yes, combining them with the "ALL" switch will give you the best chance of having enough amps to turn the starter and restart the engine.