# Will a bad car battery not take a jump and then work just fine? **URL:** \ **Category:** Factual Questions\ **Created:** [July 15, 2024, 10:52pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290 "2024-07-15T22:52:15Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![Al128](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/al128/32/16541_2.png) [@Al128](https://boards.straightdope.com/u/Al128)\ **Post date:** [July 17, 2024, 10:27am UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/21 "2024-07-17T10:27:45Z")
> [@Dallas\_Jones](#): > > The _first thing_ to do when having battery issues is to clean off any corrosion and be sure that the cables and posts that they connect to are clean and bright. They are lead and clean up with just a little brush or sandpaper. brush water with lots of sodium bicarbonate onto the terminals… that will eat any corrosion away (light blueish foam forming in the process) … ---
**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:** [July 17, 2024, 3:41pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/22 "2024-07-17T15:41:02Z")
> [@Francis\_Vaughan](#): > > Lead acid batteries can sometimes fail due to the failure of one of the bridging connections between cells. Just simple mechanical separation of the connection. This is particularly a problem with off roading, and why batteries intended for this use exist. It’s also an issue with drag racing. If you’re building a drag car, the battery should be oriented so that the plates in the battery are parallel (in-line) with the direction of travel. ---
**Author:** ![sweeteviljesus](https://avatars.discourse-cdn.com/v4/letter/s/898d66/32.png) [@sweeteviljesus](https://boards.straightdope.com/u/sweeteviljesus)\ **Post date:** [May 30, 2025, 6:26pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/23 "2025-05-30T18:26:44Z")
[deleted] ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [May 31, 2025, 2:17am UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/24 "2025-05-31T02:17:27Z")
> [@LSLGuy](#): > > Heavy corrosion amounts to effectively weakening the battery. Remove the terminals, clean off the corrosion with a suitable battery terminal brush and reassemble and your battery may well gain a new lease on life. I concur. Not a bad idea to carry a small wrench and terminal brush or spray cleaner in the trunk. ---
**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:** [May 31, 2025, 10:09am UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/25 "2025-05-31T10:09:48Z")
Last week our son was working on an old car that has been sitting in our driveway for a while. He had been messing around with it for an hour trying to get the engine to turn over, was getting frustrated, and asked for my help. The battery was fairly new, fully charged (12.6 V), and presumably healthy. Radio and blower fan worked with the key in the ON position. But when he turned the key to crank the engine, all we heard was a “click.” I asked him to turn on the headlight switch. He did so, and the lights did _not_ come on. Hmmm… The battery terminals looked dirty and corroded. And both were loose! I told him to disconnect the battery cable terminals and thoroughly clean them - and the battery posts - with a wire brush, and then use a ratchet & socket to tighten them to the battery posts. He did so, and the engine fired right up. The look in his eyes was priceless. He now knows that clean & tight battery connections are an absolute necessity when the load wants 300+ amps. ---
**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:** [May 31, 2025, 5:56pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/26 "2025-05-31T17:56:12Z")
If you have an older (well-used) car, that has had the battery replaced several times, the clamps can get stretched to the point where no amount of tightening them will make a good contact. The clamp ends will meet before the terminal gets squeezed. When this happens, cut them off an replace with brass battery clamps. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [May 31, 2025, 6:02pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/27 "2025-05-31T18:02:37Z")
I doubt your battery was bad, most likely it was a simple bad connection at the post of your battery which would have been corrected when he replaced your battery. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 31, 2025, 6:04pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/28 "2025-05-31T18:04:02Z")
> [@beowulff](#): > > When this happens, cut them off an replace with brass battery clamps. Probably better to replace the whole battery wire(s). Those large swaged connectors are attached very thoroughly at the factory. Any field joint you can make between a separate new connector and the existing cable will be a lot less durable electrically. You’ve just introduced 1 or 2 major new weak points into an already aging electrical system. To be sure, if you’re pinching pennies those cables cost $10-$30 each. Whereas clamp-on terminals are as cheap as $10/pair ---
**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:** [May 31, 2025, 6:47pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/29 "2025-05-31T18:47:48Z")
Well, when I do it, I solder them… ---
**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:** [May 31, 2025, 7:30pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/30 "2025-05-31T19:30:40Z")
I had an F350 Diesel with dual batteries. It had a special positive cable that was eye-wateringly expensive. I ended up making my own with welding cable and big split-bolts, and it worked great! ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [May 31, 2025, 7:32pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/31 "2025-05-31T19:32:12Z")
> [@LSLGuy](#): > > Probably better to replace the whole battery wire(s). What gauge would the wires have to be to not set your car on fire if you wanted to DIY it? ---
**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:** [May 31, 2025, 7:32pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/32 "2025-05-31T19:32:41Z")
Aught or bigger. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 31, 2025, 7:41pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/33 "2025-05-31T19:41:09Z")
The ones you buy at the car parts store tend to be 4ga or 6ga. I might choose 2ga if I wanted to make it bulletproof, but there’s definitely diminishing returns to bigger. For example: **[Advance Auto Parts: Search “battery cable”](https://shop.advanceautoparts.com/web/SearchResults?searchTerm=battery+cables&autoSuggest=false&recentSearch=false&storeId=10151&catalogId=10051&langId=-1)**. If you want to get more specific, add your vehicle type at the top. ---
**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:** [May 31, 2025, 7:51pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/34 "2025-05-31T19:51:19Z")
It really depends on the vehicle. The truck had giant cables. A tiny 4-banger can get away with bell wire… ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 31, 2025, 8:01pm UTC](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290/35 "2025-05-31T20:01:29Z")
For sure. Definitely don’t go smaller than factory. But you can assume factory was the barest minimum. [Previous page](https://boards.straightdope.com/t/will-a-bad-car-battery-not-take-a-jump-and-then-work-just-fine/1004290.md?page=1)