Car Battery Load Test With Multimeter | EASY DIY

Learn how to perform a QUICK and ACCURATE load test of a 12-volt car battery using a multi meter with and without a Min/Max Function!

[@I.Live4oldcars.prospecting]

This was very helpful. And easy to understand. Thank you

[@ReviveMyRide]

Cheers! Glad it was helpful! Thanks, Phil

[@I.Live4oldcars.prospecting]

@@ReviveMyRide your welcome

[@Malc2169]

6 * 1.7v = 10.2v, there's your minimum. 6 * 2.35 = 14.1v to 6 * 2.40 = 14.4v while running/charging. That's your numbers. Source - 34 years working in the battery industry.

[@user-gm8qq8cf4x]

Do a video mate

[@LarryBinFL]

This is not really a situation to do a load test; if you see a 0.6V drop from full in a few minutes with the car off, then there is either a problem with significant drain on the battery, or the battery is rapidly self-discharging. What you *should* have done is first disconnect the negative lead and check amperage flowing out of the battery with car off. It should be *very* low, I've never measured it but I'd expect less than 200mA. And if it is high, like 1A, then I would expect there is a problem. But more likely, you would see a reasonable number, and all you should do then is leave the battery disconnected and see if it is self -draining. That is common in older lead-acid batteries, as the plates will sulfate and drop that sulfate to the bottom, where it builds up and eventually shorts a cell. If the battery is good, it will barely drop in voltage. Even with a little load on it, you should see it drop to 13.2V, which is the steady state for a full battery (2.2V per cell), before it finally drops and stays at 12V. But if a cell is bad, it will continue to drop, possibly down to 10V (5 times 2V) if one cell is bad, and even lower if the problem is across cells.
Also, not sure I would call what you did a "Load Test", but labels may differ across the Atlantic. Here in the USA, a Load Test is putting a measured heavy load on the battery and looking at the current it supplies as well as the voltage the battery can hold up.

[@ReviveMyRide]

Thanks for the very comprehensive comment! I did check the amperage “drain” and it was negligible. I don’t really think it matters what order you do these tests in, it’s more of a process of elimination, usually starting with the most likely and I had a feeling the battery wasn’t holding charge. Maybe I should have included it but I was trying to stay focussed on the load test in this video. My battery is 14 months old and has never been left in a discharged state, so I knew the problem wasn’t sulphate. I’m aware of method for a Full load test using a known heavy load but most people don’t have one of these at home and it’s harder to get to a shop for it to be done if your car is having starting problems. I’ve used this method of using the starter motor as the load many times and have always gotten really good results. Maybe give it a try next time you have a battery issue and see how the tests compare? Thanks, Phil

[@petersimms4982]

🇨🇳👍

[@ArcanePath360]

My voltage is displayed on my dash on my bike. When I first power up, before cranking, the V sometimes shows it's as low as 6-7v but rapidly rising until it slowly creeps up to 12.2 where I crank it. If I try to start it too soon it dies momentarily and the bike does a factory reset. Usually the 2nd crank it starts up fine.

[@ReviveMyRide]

Very weird symptoms! I haven’t come across that before…

[@ArcanePath360]

@@ReviveMyRide I think there's a big load on it, just as I power it on. It has automatic suspension control which I think it tests as well as a servo motor on the exhaust valve, ABS pump, all kinds of diagnostics I don't even understand. There's a whirring noise which doesn't seem to go away either.
I just bought the Topdon BT20 load tester so maybe that will reveal some of what's going on with my starting issues, as sometimes it is a bit iffy at cranking.

[@rosemcbirney5123]

My battery is saying charged 1345 on the bench should it still read that number in the morning if it’s drops down is telling me the battery is failing

[@ReviveMyRide]

Hi, does charged 1347 mean 13.47 volts? Yes, I would expect the battery to have pretty much the same charge in the morning if disconnected and left overnight. If it has dropped a lot, then yes, that wouldn’t be good news for the battery. However, if it stays the same, doesn’t mean the battery is good, hence doing load tests etc to test the battery. Cheers, Phil

[@rosemcbirney5123]

Thank you for responding I will get a load test

[@tigermoth3194]

Great video. Now subscribed 👍👍

[@ReviveMyRide]

Thank you! And great to have you as a subscriber 👍😎 cheers, Phil

[@leonardodavinci303]

Nice overview. You didn't put the other promised link in the description.

[@ReviveMyRide]

Thanks! Sorry about the link, totally forgot. I haven't done a video yet on this but there's a channel that I like to watch called "Eric the car guy". He did a good video on this, here's the link! th-cam.com/video/KF1gijj03_0/w-d-xo.html Cheers, Phil

[@petersimms4982]

🇨🇳👍

[@julesviolin]

That cranking sounded really slow rpm to me without even looking at the meter.😅

[@ReviveMyRide]

Agree! You mean the second crank right? First one sounded ok and a lot of people only do one load test. I’ve learned to do two because if you do a short journey, the alternator doesn’t have much time to charge the battery and you can get stranded! Cheer, Phil

[@petersimms4982]

🇨🇳👍

[@petersimms4982]

Spent 40 years fix German dumpsters , always problems with power drains, spilt drinks,water ingress?? A living nightmare. I’m retired and drive a Tesla mod3 ,never been sooooo happy 😉

[@ReviveMyRide]

I had a Merc CLK for 12yrs, and a BMW Z4 for a similar amount of time, never any issues but the newer cars? Now that’s a different story. I’m glad you are enjoying your Tesla, I’ve been in one, fantastic machines but not my cup of tea 🫖 cheers, Phil