I had a similiar thing with the Hudson.Constant flat battery. Found that the power windows had a constant power to them and would work all the time. Changed that over to work with ignition on and problem gone.
50 to 70 milliamps might be considered "acceptable" (I guess) in late model electrical systems, but unless it has an electric clock, an old car shouldn't have any draw when shut down.
That’s what I thought. I have a analog clock, 1940s. My power windows don’t work unless the key in on.
They said it’s low, but tested good. Mind you, when I tested it Christmas morning it was 12v. This morning it was 7v. I haven’t driven it. Only testing for draw. They are going to charge it to see if it holds charge. Then they want me to comeback to test the alternator. If every morning it starts then the alternator should be good. It’s only after a couple days does the battery die. That should mean the battery isn’t holding charge?
They can't really definitively test a battery at 7 volts. You'll see conductance type battery testers that will use the existing battery voltage and convert it to an AC signal and feed it back through the plates for some kind of jiggery-pokery analysis. I have one, and they are cool, but it isn't an actual load test. If this type of tester says a battery is defective, it is. On the other hand if it says a battery is OK, it might be. Anyhoo if the battery is only measuring 7 volts it is really getting drawn down hard, or is defective, or both. Like Bones mentioned, once a starting battery gets knocked down hard they will never again quite be what they once were - repeat that process just a few times more and it's done - pretty much good only for a core. This is why starting batteries die very quickly when used in deep cycle applications. You'll have to measure the charging voltage output of the alternator under load. Turn the headllights on, turn the heater fan on, radio, etc.
Put your battery on a charger and charge it up , completely. Remove either battery cable, let car sit for 1 or 2 days. Hook up battery cable, see if car starts, if it won’t . Bad battery! If it starts, take cable back off wait two more days. If it starts then , you probably have a good battery! Charge battery and keep the battery cables on car and see if there is a difference! This takes time, but it shows what’s going on better than any tester. If it’s your play car, it should be no problem! Bones
Charge the battery. Disconnect one battery lead. Hook a 12volt test light between the battery post and the lead. If the test light lights up you have a draw that will cause the battery to go dead. It takes around a 1 amp draw to light the test light. If it does not light the any draw would be small and should not drain the battery. (Clocks sometimes cause a draw when tested like this) If there is a draw, start unplugging things until the light goes out. (Sometimes internal regulator alternators can cause a draw)
I will do this 2nd, I connect the test light the same as I would the multi meter? Positive connected and the test light between the neg post and neg cable?
Now put it in the car and leave it disconnected for a couple days and then check like stated above. I would not take a counter man's opinion as gospel.
test light between the disconnected battery post and the disconnected cable. make sure every thing is switched off. does not matter if you use the positive or ground side
Why use a test light with low sensitivity when the way more sensitive multimeter you already have says EXACTLY how much current flows? Sure, there are times when a lamp is a better choice (when you need a load at the same time as you check for voltage), and people who don't understand multimeters may feel more safe using a lamp, but it's extremely crude.
I do agree. I figure it won’t hurt to double check with a light. I actually plan on taking a photo with my meter connected then my light connected to see what people think. I can’t wrap my head around why my car drain the battery if my milliamperes are so low and I don’t have a running accessory except a analog clock.
Batteries are kinda funny! During my 33 year career I dealt with a fleet of trucks, some with six batteries! I have seen batteries do just about everything in the world. They are actually one of the hardest things on a car to “ test” accurately! The tests I described is about as fool proof as you can get...... for some things! Lol Bones
A 0.13mA load probably won't give you a visible spark. Disconnect the clock and then try it. That small a current draw could just be a dirty conductive terminal, connector, etc, going to ground (highly unlikely, but I have had a few), or an erroneous meter reading (spurious crap the meter is picking up from appliances, nearby AC circuits, etc.).
One of the other good ways to test batteries is with a good about 10 amp battery charger with a built in regulater. You can charge a discharged battery and see how long it takes to reach full charge. Then set the battery out for a while( days) then reconnect the charger and see how long it takes to go back to reading full charge.These methods take time, but are very accurate! Bones
That should read 12.6 for a fully charged battery. 12.33 volts , in itself , does not mean a bad battery, just maybe slightly discharged. Set on the bench and read the voltage tomorrow, it should be almost the same. That is the beauty of the digital gauges, way more accurate than analog! Bones
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