Do I need this?

[M2M]

Originally Posted by alexiskai

I did connect batteries in parallel like that one time, and they were Optimas, but the only reason I did it is because I had accidentally deep-discharged one of them – to the point where my trickle charger wouldn't start the flow of power when I connected it.

Someone then informed me that you could connect another battery in parallel between the dead battery and the charger, get the charger to start sending power to that battery, and the power would "overflow" to the dead battery. And then after doing that for a while you take the second battery out and recharge the first one like normal.

And it totally worked. Brought that Optima back from zero.

I dunno why you would do this in a car, though. Like if you cannot run your Model A off an Optima red-top, you have other problems.

I can think of one reason. Although this setup still gives you 6v I think it boosts the cold cranking amps tremendously which would be good to have in Arctic winter temperatures of below -40. Your vehicle’s battery loses 50% of its power when the temperature falls below 0 degrees F (-18 degrees C).