[orange4boy]

Full charging is mandatory for lead acid. A few minutes of car charging will not keep a battery charged. They must have a full charge or they sulphate and die a premature death. That takes a long slow tapered charge to achieve. At home with an automatic charger

My take on this is different than Metrompg. I think it does pay for itself if you buy a good battery. Treated Properly, a deep cycled battery will last as long or longer than an average normally used battery and ten percent better FE adds up quickly. Optima yellow or blue top can be deep cycled more times than flooded due to higher lead purity. I have a set of d31 that are ten years old and they still outperform new series 27 deep cycles on my high amp electric motorcycle. I killed two sets of Costco deep cycles but these oldies are still kicking. They are regularly cycled to 40%.

I'm going to disable the DC-DC on the insight soon to try grid powering on that car. I may even be able to a-b-a test as I now live (ack) in the Fraser Valley. Hybrids should get an even bigger improvement than regular cars due to their hungrier electronics, electric steering, etc.