First, forgive me and direct me to another thread if this topic has already been covered elsewhere. I searched and was unable to find it.

Often when I return home at night in my 2013 TCH my traction battery is half charged and I think - wouldn't it be great to have some way to top off the battery with cheap and less-polluting electricity? Also, from what I have read regarding rechargeable batteries (in power tools), they much prefer having a full charge than a partial charge. Longer battery life maybe?

I do realize that the TCH traction batteries carry only enough power to go a couple miles so this isn't a game changer but, if it were relatively cheap and easy to set up some way to plug the big battery into a 120 volt outlet at night, I would do it.

Note that I do occasionally top off the 12v battery at night which would have some limited effect on the total amps in vehicle storage. I do that mainly to keep the 12v in good shape.

Thank you in advance, David

 

It's been discussed many times on many forums.

Any efficiency improvements will be offset by a significantly reduced battery life.

The ONLY batteries that like to be at full charge are Lead-acid. All others don't. Lead-acid batteries last longest by keeping them fully charged and discharging them as little as possible. They eat themselves at lower SoC.

NiMH, NiCd and Lithium last longest when operating in mid-range SoC, roughly 20-80%.

NiCd requires frequent full depth discharge to restore lost capacity.
NiMH requires the same, but dramatically less frequently.

NiMH loses capacity by the inducement of voltage depression resulting from both short cycling AND low current over-charging (the kind you propose).

In addition to the other reasons, keeping the battery in mid-range SoC is to keep a reserve available for regenerative braking. The lack of available capacity for the first few stops of your trip would fail to recapture the kinetic energy as battery chemical energy and bleed it off in the form of heat.

 

That was very helpful! Thank you, Steve. It confirms my suspicion that, were it good practice, people would be doing it.

David