#rapid battery self-discharge, cause? (2004 Ford F-150)

19 messages · Page 1 of 1 (latest)

final dust
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My battery's (Optima 34-78) voltage seems to drop quickly on its own. I don't have an exact rate on that yet, but after 4 days of no use (and battery disconnected), the truck hesitated to start. I'm curious what can cause this, considering it's a relatively new battery (bought ~2022).

Problem... I'm also questioning whether the truck has a parasitic drain, which led to the battery being damaged, or if the battery itself has been broken (self-discharging) all this time. I'm hesitating to ascribe the former, as I know that discharging a battery will decrease its performance/capacity, but I don't think that it would cause the battery to start self-discharging, right?

short raven
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Well did you wire up anything custom?

How long have you had the truck? Was it always draining like this or only since "new" battery?

nocturne token
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one is to turn absolutely everything in the car off, disconnect the negative terminal and test the draw, it should be something super duper low like 0.03A or less

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the next would be to run the car and test the voltage of the battery with the car running, it should be running above 13.8-14, anything under and there's a heavy draw or the alternator isn't charging the battery properly

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another I would do would be drive the car around a normal day, and when you're finished driving for the day, check the battery, it should be read something like 12.7 or something high with the car off

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If you've found parasitic drain, start pulling fuses until it goes to 0.03A or something draw

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If you can get a trickle charger for your battery too, you could charge it fully by wall power, then you can rule out if the battery itself is goosed because it honestly takes a lot to kill a car battery, especially an optima

nocturne token
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@final dust Did you get any further?

final dust
# nocturne token <@706244372466892872> Did you get any further?

Sorry been busy, but I did make some progress based on what you suggested and an oreilly battery test.

Finally got around to checking for parasitic draw and I'm reading a whopping single ampere... I'm surprised the battery doesn't die even faster. I was kinda rushed, so maybe that's just the initial draw of the truck's computers running or something?

I checked the voltage while running and it did increase above 13.8. Forgot the exact number. So I assume the alternator's charging properly.

Unfortunately I didn't get a chance to drive it around or anything, just running it quickly in the yard it's currently stored in.

Last but not least, I had oreillys test the battery and it's allegedly fine.

Here's what I'm confused on though; we've specifically been disconnecting the battery after use in case of parasitic drain and I swear the battery has still discharged itself a few times as I mentioned. So what I'm doing now is having the battery sit in a room and I'm checking the voltage every few days TCC_PepeThink

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Pretty sure I did that same test a few months ago and the battery discharged... but I gotta sanity check myself again. Always possible that I had misread a voltage or something dumb lol

final dust
# short raven Well did you wire up anything custom? How long have you had the truck? Was it a...

As far as I'm aware, nothing custom. I'd have to ask family about the exact history of this problem (it's not exactly my truck)... don't know if it started before or after the new battery. Either way, I'm mainly wondering if a battery self-discharging is realistically a problem I could run into, or if someone simply forgot to unplug the battery from the truck one night and didn't tell me lol

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(see the above thing i'm testing)

short raven
final dust
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yeah, very possible i simply screwed up multiple times haha

hexed cedarBOT
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GG @final dust, you just advanced to level 1! Chat more to level up and earn top roles!

final dust
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actively trying to make a more controlled scientific test, but sadly my time to work on this is limited. so watching the voltage is probably the best way to check

final dust
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We have a THIRD UNKNOWN VARIABLE. My HARBOR FREIGHT multimeter, at some point unknown to the minds of men,,,, has begun intermittently giving FALSE LOW READINGS.

short raven