My battery seems to drain after a heavy rain

Hello. My battery has been draining. It has happened to me 2 times in the last few months. The first time was after I came out from working an 8 hour shift and the 2nd time the truck was sitting for not quite 2 full days. The only factor that is the same for both occasions is that we had extremely heavy rain a few hours before I went to start the truck and realized the battery was drained.

 

How old is your battery?

Do you have a Multimeter to test it before starting, after starting, and after a long drive?

 

My battery is about 6 months old. Yes,I have a multi meter. What exactly am I looking for before, after and after a long drive?

 

https://itstillruns.com/test-car-battery-multimeter-2210578.html

 

Sounds like you may have a short somewhere when it gets wet. If it only happens after it rains that is where I would start.

 

What is the best way to go about tracking something like that down?

 

Good question. I really don't have a good answer.

Its just that the rain was a common denominator.

 

Hopefully someone will have a process for you

 

Start pulling fuses one by one and measure the resistance across the terminals where the fuse plugs in. Anything more than a fractional reading would be a good place to start.

 

Check your battery posts and battery ground to body ground connections.

 

Since I've never experienced humidity as a cause of battery discharge, my first impression is that your battery discharging when it rains is simply a coincidental observation. If you live in southern New Mexico or far West Texas, the veracity of that observation becomes infinitely more likely; on the gulf coast or in Seattle where it's usually raining, not so much.

A cursory inspection of cables, grounds, and wiring harnesses costs nothing, but has to be thorough to avoid missing a root problem, wasting time and effort. Measuring the draw at each fuse will be definitive if the battery is actually discharging from an unintended current draw (allegedly when it's wet). Most likely, your problem is simply a cheap battery that lasted only six months. (Some are bad from installation) You get what you pay for with batteries these days; virgin lead costs big bucks, recycled lead is cheap, but environmentally friendly.

Start by using sandpaper to clean the battery terminals and the inside contact surfaces of the cable ends. If that doesn't fix your problem, then confirm the battery is actually in good health. I don't trust parts-store battery tests. If the terminals and cable ends are clean, the next-most-likely problem is going to be the battery.

 

I’m having the same issue. My ‘03 is not my daily driver so it might go a week or two between running. Usually not a problem unless it rains heavily.

my mechanic replaced the battery on warranty as one of the cells was dry before it should have been. But the new battery was dead yesterday, after a couple days of rain. Interstate batteries are not the cheapest, and I even upgraded to the heavy duty battery. They reinstalled the terminal cables also.

I’m going to test the fuses as described above. Will update if I learn anything. Thanks for this tip and the thread. Cheers.

 

@Dadof5boys there are plenty of videos on YouTube on how to properly diagnose and troubleshoot this condition as this isn't uncommon. https://www.youtube.com/results?search_query=parasitic+draw+test+12v

Keep us posted with regards to what you discover!

 

Actually, I misspoke earlier. You want to measure the amperage draw between the negative cable and the negative post. Set your meter on 10 amps DC and see what the current draw is. It should be well below 1 amp. Make sure lights are off, doors are closed, etc...