# Tell me about car battery chargers **URL:** \ **Category:** Factual Questions\ **Created:** [July 1, 2012, 11:11pm UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947 "2012-07-01T23:11:00Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![PlainJain](https://avatars.discourse-cdn.com/v4/letter/p/5daacb/32.png) [@PlainJain](https://boards.straightdope.com/u/PlainJain)\ **Post date:** [July 1, 2012, 11:11pm UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/1 "2012-07-01T23:11:00Z")
Background: I have a 1999 Chevy Tahoe. About 6 months ago it was stolen. I got it back a month later but the person who stole it cut into the electrical system to rig up a heavy duty stereo system. I disconnected all that stuff. I now find if I don’t start my truck within three days the battery goes dead. I’m guessing there is a small drain some where. It has a new battery in it. My question: I’m looking for a small, inexpensive charger to keep on the battery while it’s parked in the garage. I was thinking I should get a trickle charger (because that’s what I’ve heard in the past) but I’ve read on the internet not to waste my time with them. So for what I’m trying to accomplish (keeping my battery charged), what type of battery charger do I need? ETA: I know I need to fix the root problem but don’t really have the smarts to fix it or the money to pay someone. . ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [July 1, 2012, 11:22pm UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/2 "2012-07-01T23:22:30Z")
I think what you want is a float or maintenance charger. I see from my link below that they are also called tenders. Many regular battery chargers go into float mode when the charge is complete. > **[How to charge all lead acid batteries; how to charge SLA lead...](https://www.powerstream.com/SLA.htm)** > > 12V SLA battery charger,lead acid battery charging techniques and algorithms,sealed lead acid batteries,Pb battery,SLA,VRLA,Gel,Flooded and AGM batteries. ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [July 1, 2012, 11:24pm UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/3 "2012-07-01T23:24:11Z")
A charger will help but won’t solve the underlying problem. I believe the best solution in the long run would be to find the leak and fix it. Any semi-competent car shop can do that. With a multimeter and a few minutes to spare you can even do it yourself: [How To Perform a Parasitic Draw Test - EricTheCarGuy - YouTube](http://www.youtube.com/watch?v=KF1gijj03_0) ---
**Author:** ![Dano83860](https://avatars.discourse-cdn.com/v4/letter/d/a4c791/32.png) [@Dano83860](https://boards.straightdope.com/u/Dano83860)\ **Post date:** [July 2, 2012, 12:07am UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/4 "2012-07-02T00:07:36Z")
I got a maintenance charger at my local Honda equipment dealer for $30. it works great to keep my generator battery charged. I would guess it would work for you too. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [July 2, 2012, 3:04am UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/5 "2012-07-02T03:04:38Z")
How about disconnecting the battery when you’re not using it? You’ll still need to disconnect the charger every time you leave, right? ---
**Author:** ![Kenm](https://avatars.discourse-cdn.com/v4/letter/k/bc79bd/32.png) [@Kenm](https://boards.straightdope.com/u/Kenm)\ **Post date:** [July 2, 2012, 3:10am UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/6 "2012-07-02T03:10:08Z")
> [@AaronX](#): > > How about disconnecting the battery when you’re not using it? You’ll still need to disconnect the charger every time you leave, right? Too many computers and other electronics that need constant current. The transmission might have to learn its shift points every day. The truck’s anti-theft gizmo wouldn’t work, and _worst_ of all, the open-sesame key fob would be useless. What means this word, key? ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [July 2, 2012, 3:13am UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/7 "2012-07-02T03:13:23Z")
Ah, I was hoping the car didn’t depend that much on electricity. Transmissions adapt shift points to drivers? ---
**Author:** ![Kenm](https://avatars.discourse-cdn.com/v4/letter/k/bc79bd/32.png) [@Kenm](https://boards.straightdope.com/u/Kenm)\ **Post date:** [July 2, 2012, 4:39am UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/8 "2012-07-02T04:39:45Z")
> [@AaronX](#): > > Transmissions adapt shift points to drivers? Here’s [**one example:**](https://ixquick.com/do/search) > [@](#): > > Some transmission problems may require “retraining” the computer. This is also necessary if an electronic transmission or computer has been replaced. Chrysler TSB 18-24-95 describes the retraining procedure that allows the computer to relearn the correct shift points. > 1. Disconnect the battery to erase the computer’s memory. > 2. Reconnect the battery and start the engine. > 3. Drive he vehicle while trying to maintain a constant throttle position as it accelerates up through all four gears. If the transmission is shifting properly, it should be in 4th gear by the time you reach 45 to 50 mph. Repeat this procedure from a standing start 15 to 20 times. > 4. With the vehicle traveling at less than 25 mph, do five to eight wide open throttle kickdowns to get the transmission to downshift to 1st from 2nd or 3rd gear. Drive in 2nd or 3rd gear for at least five seconds between kickdowns and remember to kick it down only when you are going less than 25 mph. > 5. While driving at 45 to 50 mph, do five to eight part to wide open throttle kickdowns to either 2nd or 3rd from 4th gear. Again, continue driving for at least five seconds in 4th gear between kickdowns. And the radio probably would lose its station settings. **Edit:** Screwed up the link. It’s here: [Diagnose Automatic Transmission](http://www.aa1car.com/library/2002/bf90222.htm) ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [July 2, 2012, 5:18am UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/9 "2012-07-02T05:18:06Z")
Wow, I didn’t know that. That’s useful if you change gear ratios, I guess. Maybe they should use non volatile memory though. ---
**Author:** ![PlainJain](https://avatars.discourse-cdn.com/v4/letter/p/5daacb/32.png) [@PlainJain](https://boards.straightdope.com/u/PlainJain)\ **Post date:** [July 2, 2012, 6:28am UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/10 "2012-07-02T06:28:11Z")
> [@jnglmassiv](#): > > I think what you want is a float or maintenance charger. I see from my link below that they are also called tenders. Many regular battery chargers go into float mode when the charge is complete. > [http://www.powerstream.com/SLA.htm](http://www.powerstream.com/SLA.htm) Thanks for that link. I don’t know if I could manage that test myself but I know people who probably could. The info towards the end on parasitic draws was especially helpful in that it pointed me to possible culprits. Still looking for info on chargers in the mean time. Thanks everyone. ---
**Author:** ![BottledBlondJeanie](https://avatars.discourse-cdn.com/v4/letter/b/0ea827/32.png) [@BottledBlondJeanie](https://boards.straightdope.com/u/BottledBlondJeanie)\ **Post date:** [July 2, 2012, 7:40pm UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/11 "2012-07-02T19:40:21Z")
FWIW, a floater/ tender is what you want. I have several cars and don’t always drive them enough to keep a good charge on the batteries. Due to computer stuff I don’t disconnect my cables. The floater/tender won’t overcharge your battery like a trickle charger can. I have never had good experiences with Schumacher brand. You may want to buy a charger you can use to charge a flat battery if the Tahoe is your only vehicle. They aren’t that much more expensive. Try Amazon. Car part stores mark them up ridiculously. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [July 2, 2012, 10:36pm UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/12 "2012-07-02T22:36:51Z")
> [@PlainJain](#): > > Thanks for that link. I don’t know if I could manage that test myself but I know people who probably could. The info towards the end on parasitic draws was especially helpful in that it pointed me to possible culprits. > > Still looking for info on chargers in the mean time. The link wasn’t for helping with testing, it was to demonstrate the float or tender charger principle. [Here, $19 at Walmart.](http://www.walmart.com/ip/Schumacher-SpeedCharge-Battery-Maintainer-and-Charger/13005742) ---
**Author:** ![BottledBlondJeanie](https://avatars.discourse-cdn.com/v4/letter/b/0ea827/32.png) [@BottledBlondJeanie](https://boards.straightdope.com/u/BottledBlondJeanie)\ **Post date:** [July 3, 2012, 1:47am UTC](https://boards.straightdope.com/t/tell-me-about-car-battery-chargers/626947/13 "2012-07-03T01:47:33Z")
> [@jnglmassiv](#): > > The link wasn’t for helping with testing, it was to demonstrate the float or tender charger principle. [Here, $19 at Walmart.](http://www.walmart.com/ip/Schumacher-SpeedCharge-Battery-Maintainer-and-Charger/13005742) And that one is what started my hatred against all chargers branded Schumacher. It’s a saga no one wants to hear, but there are others around that price range. Also, for the OP’s Tahoe year, you might be fine disconnecting the battery when not in use.