# Battery tender question **URL:** \ **Category:** Factual Questions\ **Created:** [September 11, 2022, 2:03pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380 "2022-09-11T14:03:06Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [September 12, 2022, 2:12pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/21 "2022-09-12T14:12:28Z")
> [@ZonexandScout](#): > > Caveat: It may work just fine and never have a problem. But people often turn off the water supply to the hoses to their washing machines when they leave a house unoccupied…simply because the results when everything ISN’T OK are pretty bad. We turn off water to the entire house. Only way to be sure. ---
**Author:** ![ZonexandScout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zonexandscout/32/544_2.png) [@ZonexandScout](https://boards.straightdope.com/u/ZonexandScout)\ **Post date:** [September 12, 2022, 2:20pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/22 "2022-09-12T14:20:25Z")
Better than nuking it from orbit. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [September 12, 2022, 2:36pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/23 "2022-09-12T14:36:58Z")
😉 one of my favorite movies. ---
**Author:** ![a6ka97](https://avatars.discourse-cdn.com/v4/letter/a/c2a13f/32.png) [@a6ka97](https://boards.straightdope.com/u/a6ka97)\ **Post date:** [September 12, 2022, 3:57pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/24 "2022-09-12T15:57:49Z")
I’m sure the Battery Tender company’s (it is a brand name) customer service would love to answer your question. Is there an 800 number or a email/web site on the tender that you could contact to get a correct answer? I would hate to have your truck catch on fire due to getting the wrong answer from here. Personally I don’t think it will make a difference as my son’s motorcycle has a tender that stays hooked to the battery, (difficult to access the battery) all the time. Granted the amps his motorcycle puts out is probably way less than your truck. ---
**Author:** ![echoreply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/echoreply/32/3641_2.png) [@echoreply](https://boards.straightdope.com/u/echoreply)\ **Post date:** [September 12, 2022, 6:04pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/25 "2022-09-12T18:04:29Z")
> [@Machine\_Elf](#): > > The accessory cable for connecting a Battery Tender to a battery is fitted with an in-line fuse holder, and comes with a 7.5-amp fuse: I think that is the correct solution, but the installed ring connectors are too small to attach to car battery posts. Perhaps they are supposed to be installed on the screw used to tighten the battery cable to the post? I have one of those cables for my truck, but I’ve never figured out how to install it. The battery uses side terminal bolts, so the cables screw directly into the battery, instead of clamping to the terminals. I haven’t found another obvious attachment point for the positive connection. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 12, 2022, 6:07pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/26 "2022-09-12T18:07:02Z")
Isn’t there a removable bolt on those terminals? Just put it under its head. ---
**Author:** ![echoreply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/echoreply/32/3641_2.png) [@echoreply](https://boards.straightdope.com/u/echoreply)\ **Post date:** [September 12, 2022, 6:08pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/27 "2022-09-12T18:08:11Z")
> [@beowulff](#): > > Just put it under its head The ring terminals are too small for this, and I just haven’t bothered to swap them with larger rings. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 12, 2022, 6:15pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/28 "2022-09-12T18:15:07Z")
I’ve been known to drill them out… ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [September 12, 2022, 6:15pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/29 "2022-09-12T18:15:36Z")
My battery is a mess with cables. A plow is hooked up, and a winch. As I said above it gets one hell of a work out. For now, I’m just using the clamps from the tender to hook it up. Far from ideal I know. ---
**Author:** ![Polarity](https://avatars.discourse-cdn.com/v4/letter/p/7cd45c/32.png) [@Polarity](https://boards.straightdope.com/u/Polarity)\ **Post date:** [September 13, 2022, 12:42am UTC](https://boards.straightdope.com/t/battery-tender-question/971380/30 "2022-09-13T00:42:18Z")
Wouldn’t be a problem at all. We do it all the time for backup generators. Battery charger is permanently installed. It sits on the lot attached to the battery but unused. Generator goes on rent and battery charger gets plugged in, so the generator can start when needed. Generator occasionally starts up and runs with the battery charger still powered and attached. In short, it gets used in all possible configuration with no damage ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 13, 2022, 1:39am UTC](https://boards.straightdope.com/t/battery-tender-question/971380/31 "2022-09-13T01:39:07Z")
> [@enipla](#): > > It would be easier to just fix the thing in place and not have to open the hood in the middle of a blizzard and remove the unit. Just unplug it. If underhood access during inclement weather is the main issue, then route longer wires from the battery to somewhere more convenient - maybe up near the windshield, or even in the passenger compartment. Connect your tender somewhere like that, and it’ll be much easier to disconnect when the hood is frozen shut and covered by six inches of snow. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [September 13, 2022, 4:15am UTC](https://boards.straightdope.com/t/battery-tender-question/971380/32 "2022-09-13T04:15:18Z")
> [@ZonexandScout](#): > > If you want to attach the charger permanently, I’d strongly suggest using the quick disconnect that many of them have (or which you can install yourself) to disconnect the unit from the battery when not in use This is a good answer, and what I was gong to suggest myself. The Quick Disconnect can extend out the grill making unplugging very convenient. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [September 13, 2022, 6:50am UTC](https://boards.straightdope.com/t/battery-tender-question/971380/33 "2022-09-13T06:50:55Z")
> [@ZonexandScout](#): > > TL;DR: I wouldn’t trust the charger to protect itself against back-voltage. Sorry but your attitude towards **enipla’s** proposal is irrational. Every auto is full of itty bitty circuit boards connected to the battery capable of pumping out hundreds of amps. Every single one of them is not shorting out because of itty bitty resistive or inductive or active components that cause it not to do so You are just being (as you said) a worry wort who worries about something different or new, even though it’s almost precisely the same as existing things you are used to. ---
**Author:** ![ZonexandScout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zonexandscout/32/544_2.png) [@ZonexandScout](https://boards.straightdope.com/u/ZonexandScout)\ **Post date:** [September 13, 2022, 1:09pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/34 "2022-09-13T13:09:33Z")
Yes, but every one of them is on the other side of a fuse and not connected directly to the battery terminals. They have also been thoroughly tested in an operating vehicle environment. As I’ve stated a couple times, adding a fuse to the tender’s charging cable would make me much more comfortable. ---
**Author:** ![echoreply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/echoreply/32/3641_2.png) [@echoreply](https://boards.straightdope.com/u/echoreply)\ **Post date:** [September 13, 2022, 2:19pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/35 "2022-09-13T14:19:18Z")
> [@ZonexandScout](#): > > As I’ve stated a couple times, adding a fuse to the tender’s charging cable would make me much more comfortable. Both the clip on and permanently installed Battery Tender® cables I have use fuses. The $4 tender from Harbor Freight does not have a fuse, but it also doesn’t output enough volts to charge a car battery, so it’s safe because there’s no point in connecting it. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [September 25, 2022, 11:19pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/36 "2022-09-25T23:19:06Z")
> [@beowulff](#): > > It’s easy enough to test. > Just put an ammeter in series with the battery tender leads, unplug it, and turn the engine on. If the current reads zero, you can leave it connected all the time. If the current is non-zero, but very small, you are probably safe.If the current is large (like anything over 250mA), I would not leave it connected. So has anyone _done_ these measurements yet? Alrighty then… 🙂 [![](https://live.staticflickr.com/65535/52384529194_5662cccb0e_z.jpg) ](https://live.staticflickr.com/65535/52384529194_5662cccb0e_z.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384648460_0bfd6e47d3_z.jpg) ](https://live.staticflickr.com/65535/52384648460_0bfd6e47d3_z.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52383284352_f5915d721e_w.jpg) ](https://live.staticflickr.com/65535/52383284352_f5915d721e_w.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384460738_98bf00631f_w.jpg) ](https://live.staticflickr.com/65535/52384460738_98bf00631f_w.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384219616_2e67fc0868_w.jpg) ](https://live.staticflickr.com/65535/52384219616_2e67fc0868_w.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384460013_8fb31c32a1_w.jpg) ](https://live.staticflickr.com/65535/52384460013_8fb31c32a1_w.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384647060_7a93396c9c_w.jpg) ](https://live.staticflickr.com/65535/52384647060_7a93396c9c_w.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384646715_42e455f088_w.jpg) ](https://live.staticflickr.com/65535/52384646715_42e455f088_w.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384217836_64f1aba514_w.jpg) ](https://live.staticflickr.com/65535/52384217836_64f1aba514_w.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384646045_24772c50e6_w.jpg) ](https://live.staticflickr.com/65535/52384646045_24772c50e6_w.jpg) * * * * * * [![](https://live.staticflickr.com/65535/52384526389_38a57b8a20_w.jpg) ](https://live.staticflickr.com/65535/52384526389_38a57b8a20_w.jpg) ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 26, 2022, 1:01am UTC](https://boards.straightdope.com/t/battery-tender-question/971380/37 "2022-09-26T01:01:05Z")
[![](https://img.youtube.com/vi/QeYxkULH-tQ/maxresdefault.jpg "A Christmas Story- Ralphie Daydreams for an A+ Clip (HD)") ](https://www.youtube.com/watch?v=QeYxkULH-tQ) ---
**Author:** ![Cervaise](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cervaise/32/16693_2.png) [@Cervaise](https://boards.straightdope.com/u/Cervaise)\ **Post date:** [January 1, 2023, 9:39am UTC](https://boards.straightdope.com/t/battery-tender-question/971380/38 "2023-01-01T09:39:19Z")
Was just browsing older threads and stumbled on this, and wanted to let you know you didn’t get _nearly_ enough applause for this post. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [January 1, 2023, 2:31pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/39 "2023-01-01T14:31:02Z")
Agree Cervaise. In any case, my set up of just leaving the tender connected to the battery and running the cord out through the grill and just plug it in is working great. The battery really takes a beating running the plow. And also when the winch is needed. It REALLY had a work out pulling out my neighbors plow. It was stuck good. Don’t get a 4x4 chained up on all 4 wheels stuck. You’re going to have a very bad day. I should really have a dual battery set up. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [January 1, 2023, 2:35pm UTC](https://boards.straightdope.com/t/battery-tender-question/971380/40 "2023-01-01T14:35:51Z")
Thanks. Of course, I only took measurements on the trickle charger sold by Harbor Freight; am not sure about other chargers. [Previous page](https://boards.straightdope.com/t/battery-tender-question/971380.md?page=1) [Next page](https://boards.straightdope.com/t/battery-tender-question/971380.md?page=3)