Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Charging battery by driving

My fiancee in London has a Toyota Picnic with a diesel engine (2.2 turbo diesel)and a heavy duty battery. Given the price of fuel and other disincentives to driving in this city, she uses it infrequently, maybe once a week, and then for very short trips. Question, then, is: How long (or how far) should she drive it to insure the battery doesn’t eventually go flat?

Batteries eventually go flat. Most are reliable for 4 years, then become suspect. If it spends a lot of time parked, a plug-in ‘Battery Tender’ or equivalent may be a better option. For $30 USD, it will keep a good charge on the battery. It comes with battery clamps for easy on-and-off, and with ring terminals and a quick disconnect for a more permanent install.

She might consider an inexpensive maintenence charger to keep the battery fully charged. Much cheaper and convenient if she has covered parking with access to A/C outlet. Idling with the headlights and heater on will not ‘fill’ the battery. At cruising speed with no accessory draw it might take several miles and starting the engine further discharges the battery, adding to the deficit. At 12.8 volts (engine off)the battery is fully charged. When voltage drops to 12.6 volts it would be advisable to re-charge by whatever means are most convenient.

She needs a Battery Tender, which will keep the battery fully charged even if she doesn’t drive the car. These devices are inexpensive, and I’m sure they will keep the battery alive for less than the cost of driving the car.

Thanks to the three people who replied. A follow-up question. We went to the local shop where she has the car serviced to ask about chargers. The guy there said that repeated charging would ruin the battery and that she would be better advised to drive it some distance at least once a week. The risk of frequent charging harming the battery sounds implausible to me (the shop doesn’t sell chargers), but could someone please tell me if the guy we spoke to is right or not. Thanks.

What was recommended are “trickle-chargers” or Battery Tenders, rather than a traditional battery charger. One of these devices will not harm the battery, and in fact, owners of classic cars use these devices simply because their cars are rarely driven.

All the people who advised you to use a battery tender (not a battery charger) have used them, themselves. I’d trust them.

Thanks to those who responded to me second question as well. Your knowledgeable advice is much appreciated. J

Another option might be a solar battery charger. You might have to look around to find one (Google solar battery charger) These won’t quickly charge anything, but will keep a trickle charge on the battery, like the “battery tender”, and have the benefit of not needing to be plugged in, which is nice if she parks in a lot or far from an electrical source.

(Admittedly it won’t help much if she parks in a garage, unless you can place it by a window.)

While the names are often used interchangeable, the one you want should be called a battery tender. A trickle charger is almost the same thing, but not exactly and the battery tender is better and safer for your car.

Besides getting a battery tender, she should still take it out maybe once a month for a longer drive on a freeway (sorry, motorway) to thoroughly heat up the engine and oil to get water and fuel evaporated. Short trips in cold weather are very rough on the oil.

My dad has a 2003 Honda Accord which my mom bought brand new. It is driven frequently and has just over 100,000 miles on it. It still has the same battery that it came with and has never had any problems.

I’ve been using a Deltran Battery Tender for years and have been very satisfied. I originally bought it to maintain my motorcycle battery during the winter.

This is the main website The European website is

I just replaced an alternator in my 1993 Chevrolet Caprice today. The guy at the rebuild shop advised me to make sure my battery was fully charged. A discharged or failing battery is very hard on an alternator. For this reason alone I would use a battery tender to keep the battery charged. A battery is a lot cheaper and easier to replace than an alternator.

If a Battery Tender is unavailable a Trickle Charger (12V, 500 MA) could be used to charge a battery overnight maybe once a week or so.

Good Luck,

Ed B.