I have a pickup truck that I rarely use. I use it so rarely that I need to deliberately drive it occasionally when I’d prefer to use the car, to keep the battery charged. A couple of weeks ago I found that I’d waited too long and the starter wouldn’t turn over. So to prevent this from happening again and to avoid the need for maintenance drives, I bought a charger / maintainer (this one).
So here’s the problem. It’s not convenient to keep it plugged in constantly, because there’s no convenient power outlet to the parking spot. I have to run an extension cord across a walkway. Everything I read about using a maintainer seems to expect it to be plugged in constantly. Can I keep the battery in good shape by plugging it in at intervals? Like just plug it in once a week until it indicates that the battery is fully charged, then unplug it until next week?
The truck shouldn’t need to be charged up even that often unless you have something draining the battery or a bad alternator or battery.
But yes, there shouldn’t be any issue with doing like that, at least not in general. If your battery goes from full to dead in such a short period of time, I’d be concerned that those deep cycles could cause an issue. On an otherwise healthy battery, I don’t see any issue. That’s basically what your alternator is doing.
You may want to look into what’s causing it to die so quickly. If the truck is a bit older (and has less electronics) you could think about just disconnecting the battery during the times you’re not using it. They even make a switch you can install between the battery and cable to disconnect it. It’s meant more as a cheap kill switch (to prevent it from being stolen) but it would work for this application as well.
Oh, I’m not saying the battery dies in a week. I was just throwing that out as a charging interval. If it’s possible to keep the battery healthy with monthly charging or even less, that’s even better.
This last time it died, it had been at least 2 months since it was driven, possibly 3-4 months.
Hell, one of my trucks has been having some issues lately and for the past year or two, I throw a tender on the battery just to get it back from not being able to crank the engine to having full voltage. Granted, it can take a day or two, but it works just fine.
How often you need to charge the battery depends on the vehicle. Some vehicles need to be charged every week or two. Others can go months between charges.
The shelf life of a battery isn’t the issue here. The issue is the drain on the battery while it’s connected to the vehicle, since many things will still draw a small amount of power. For example, the radio typically draws a small amount of power so that it can maintain its memory, which holds your radio station presets and other radio settings like the volume, EQ settings, etc. The engine computer will often also use a small amount of power to maintain its own internal settings.
As for sitting still for extended periods of time, in large lead acid batteries, what can happen over time is that the electrolyte starts to stratify based on density. When that happens, you get these small eddy currents that end up sulfating the battery plates and ruining the battery. Large lead acid battery systems will sometimes contain stirring rods to periodically stir up the electrolyte and prevent this from happening. Car batteries are significantly smaller though, and I have read conflicting technical information about whether stratification of the electrolyte can result in significant plate sulfation in a car battery. In any event, it would only be a problem on a vehicle that sits for months at a time. Driving the vehicle once every month or so should shake up the electrolyte enough to prevent this from ever being a problem.
Vehicles that sit for too long can develop other problems as well, like rubber seals drying out, and water vapor from the air condensing inside the engine and mixing in with your oil. Brakes can also rust. You also don’t want to drive the vehicle for a mile or two and that’s it. At least once a month or so, you want to drive the vehicle enough so that it completely warms up. Once the engine completely warms up, any water that might have made its way into the engine, and any water that condensed out of the exhaust inside the exhaust pipes will get flashed into steam and will be expelled from the vehicle. If you only drive the vehicle for a mile or two say once every week or two, it is very common for your exhaust system to rust out prematurely due to water condensation.
Vehicles that sit for a long time can also develop flat spots on their tires. In my experience, driving the vehicle around every day for a couple of weeks will make these flat spots go away. Rust on brakes and rotors will generally wipe itself off from friction fairly quickly, but if the brake calipers are rusty and sticky, you can generally break them free by driving slowly around your neighborhood and repeatedly slamming on the brakes.
Gasoline also goes bad. The gas in the tank will go bad more quickly if there is a lot of air in the tank, and blended fuels tend to go bad faster than non-blended fuels. You want to drive the vehicle often enough that you go through a tank of gas at least once every six months or so.
Ding Ding Ding, we have a winner. I have been using one of these on my old work truck. I’ll sometimes go 6 months without running the truck and it starts right up every time.
Racer, does yours just plug into the cigarette lighter?
My truck is a 2004 Dodge. I kinda wonder if there is some electrical component that will not allow it to charge the battery from the cigarette lighter. A diode I think.
I wouldn’t expect there to be, there should just be two wires that go right to the ground/fusebox. However, you’ll have to make sure the lighter works while the truck/car is off. I don’t know that all vehicles, especially know that those are just ‘power supplies’ and not cigarette lights, work when the key is off. If they don’t supply power when the truck isn’t running, you won’t be able to feed power back into them when the truck is off either.
The rule thumb that I use, and I just completely made this up, so it is probably not appropriate for GQ, is the following. For the motorcycle, if I have not ridden it in two weeks, and do not plan to ride it again soon, I put it on the tender. Same for the truck, but with a cutoff of one month instead of two weeks. I know that both vehicles can survive much longer without being on the tender, but that when I do put them on the tender after those intervals, it does charge the battery for some time before going into maintenance mode.
My feeling is that batteries are expensive, and plugging them in isn’t too difficult, so when the charge has dropped by a noticeable amount it’s time to top them off.
Mine is a 91 Ford. The lighter was long gone when I bought it. I cut off the lighter adapter, spiced on 2 wires and ran those to the battery. I salvaged 2 clips from a thrift store bought battery charger. The cell array sits on my dash, I just disconnect the battery clips before starting the truck.
I have a car that will drain a battery to 70% from full in three weeks just sitting. That’s pretty quick. Most cars don’t drain that fast. I have numerous vehicles on tenders, and a couple that cannot be on tenders because they are in storage without electrical outlets. If you can top off the battery every month, you are going to be just fine. A longer interval might suffice, too, even six weeks. If you are storing a vehicle for months with no intent to use, pull the battery.
If you have a tender that notes the charge %, and you run it up to 100%, remove it, then come back in a few weeks and note the drop.
The deeper you dip into the battery and the longer the % is low, the shorter the life of the battery overall.
