I have good experience with battery pulser, which remove the sulfat crust from the lead plates.
The battery in my Escalade was down in capacity half a year ago. When I let the vehicle on ignition, after I stop the engine, five to ten minutes where enough to drain the battery enough, to prevent the car from start.
I installed the pulser and now my battery has a good capacity I don't know if it also helps when the battery suffers from too much heat.
Here a link just for example. I don't recomment expecially this unit i have a different one, but I think they all work new same principle...
Novitec Megapulser 12 V Bleiakku-Refresher 12 V.
www.ebay.de