During this Covid malarkey I tried an Oxford Oximiser 888 to keep my LS430 fully charged. Having been a Biker for 50 plus years, these are common with bikers. I was a little unsure as to the difference in amperage resistance between large car batteries and the much smaller motorcycle batteries, as these Optimisers are designed to be left on indefinitely with no danger of boiling a battery, which would happen with a regular battery charger. However after a few days measuring the input and retained voltage, everything was fine. To the point that I ordered 2 more for wife and daughters car. They retail at £25 each including delivery from Sportsbikeshop.Co. They show the voltage constantly on the tiny screen, and they monitor and top up the batteries constantly. Hope this helps.