I’ve recently been given a company car to use. So my normal vehicle (Chevy PU) sets up a lot. The car battery goes dead within a week or two.
I realize I could start it and let it run for a bit every day to prevent this, but is there a better way? Will disconnecting the battery help? Should I get a trickle charger? Should I do both?
Also, if I disconnect the battery, will disconnecting just one terminal work?
Thanks
If the battery is draining in a week or two there’s either a small short or drain on the battery, or the battery is just old and weak. Letting it go flat isn’t good for the battery so a trickle charger might be a good idea. You can also pick up a battery isolator at any parts store, which is just a switch that you put on the negative terminal to disconnect the battery so you don’t have to mess with the terminal connector. If you just want to disconnect the battery manually, always disconnect the negative terminal. No need to touch the positive terminal.
Disconnecting the battery can cause issues.
Sometimes the engine computer relies on the battery to keep its settings. If you disconnect the battery long enough for it to lose its settings, then the car won’t run as efficiently while the computer goes back through its “learning” phase.
Your radio will likely lose all of its presets. If the radio has anti-theft protection, disconnecting the battery can cause issues with it, and you might need to take it into the dealer to do a factory reset.
Some alarm / anti-theft systems will also have issues.
If you disconnect the battery, and it won’t cause issues with your car, removing one of the terminals is sufficient. You don’t need to remove both. A lot of folks say to remove the negative terminal first, though in many cases it doesn’t make much difference. On some cars, if you remove the positive first, you can accidentally create a short between the positive terminal and the car’s body (which is electrically connected to the negative terminal) through your wrench, which is definitely not recommended. Worst case, the battery explodes in your face. If you remove the negative first and your wrench accidentally touches the car body, that’s what the negative is already connected to so no biggie.
The isolator switch that @steronz mentioned also works well and will save you some wear and tear on your battery terminals.
A trickle charger works well. You don’t need to disconnect the battery.
You should drive the car about once a month, long enough for the engine to fully reach its operating temperature. If you don’t let the engine get up to temperature, then water that has condensed in the engine will stay there and contaminate your oil, and water from engine combustion will settle in your exhaust system, causing it to rust and die an early death. If you get everything up to temperature, then the water gets flashed into steam and expelled from the car.
Your tires can develop flat spots from sitting. In my experience these usually work their way out on their own after a couple of weeks of daily driving, but you might want to lift the car up onto jack stands to keep the tires from developing flat spots.
You need to drive the car enough to go through a tank of gas every six months or so, otherwise the gas can start to go bad. Your car will probably run on year-old gas, but it will likely run a bit rough.
I’ve had this one for two years for my generator battery. No problems at all.
Anecdotal:
After my dad died we had to deal with his car (2002 Infiniti Q45 I think). I am pretty sure it had not moved in at least three years (maybe more). We called a tow truck to take it away. Flat tires, dead battery. Nothing was working on it. As it happened it was in a very difficult position for a tow truck to get at it. So, the tow truck driver hooked up a jumper to the battery. I said no way was this car gonna start. The tow driver shrugged, got in the car and it started up with no fuss like it had been driven yesterday. I am not going to say it was running well. But it ran. He drove it out of the garage and got it into a position for his tow truck to be able to hook it up.
I was floored. Never in a million years did I think that thing was going to start.
One other thing about a trickle charger: On many newer vehicles there is some sort of Battery Management System (BMS).
This computerized adjunct wants to monitor current flow into and out of the battery and is tasked with keeping track of the charge state. On my truck, there’s a device on the negative cable to the battery.
I don’t even pretend to know all the particulars, but I was told that my trickle charger should NOT be hooked directly to the battery + and - terminals but should be hooked to the + terminal and chassis so that the BMS is still involved. (It would effectively be bypassed if I connected directly to the negative terminal.)
Not a mechanic, not your mechanic, just hoping to help.
Trickle charging is a great solution. I’d also recommend checking a few things like :
So much helpful information, thanks.
Couple more questions…
I have the same problem with my plow truck. I can’t use a solar trickle charger because of the amount of snow we get. It would just get buried.
I use what is called a battery tender. Ya have to plug it in and unplug it but it works great. Beats the hell out of trying to jump start the truck when you’re ass deep in snow.
There is a fairly recent thread about it here in Factual Questions. I’ll try to find it.
Here it is - Battery tender question
Yes.
Return the switch and buy a charger?
Seems legit 
