I have a 2005 Excursion V10 with 130K on it. Battery seems to keep draining over days of use. replace the alternator when it test on the vehical with a bad diode. Battery is a 3 year old Optima. Battery charges fine, but over days of around town use it drains. If I drive on the highway does not seem to be a problem. CHecked all the doors to make sure the wife did not lightly close the rear hatch (dang switches) and all was closed tight but yet this AM my wife tells me it is dead again. Back on the charger. Any thoughts? No lights are left on, nothing plugged into the lighter outlets. I hate to buy a new battery to find out this one is good.

Thanks folks

APEXDUCK

 

The next step is a parasitic draw test. You'll need a DVM with capability to read milliamps. Basically, Insert the probes in series with a battery cable and note the resting current draw after an hour, say. Should be no more than 50 ma. approx. Start pulling fuses and see what circuit is causing the trouble. Likely candidates include any aftermarket sound system installed by your BIL, security systems, and factory rear window wiper.

 

I just went through a charging system nightmare with mine over the past few weeks. I would check the following things first:

Voltage output at the stud on the back of the alternator
Voltage drop between the alternator and the battery
Double check all battery terminals are nice and tight

Do you have any type of aftermarket chargers or inverters hooked up in your truck?

Stupid question - Does your battery light come on briefly when you start your truck?

 

Did you get a battery load test? I had the same proplem with my 2005.Sears Pep boys will run a 45mim test for free.My battery was two years old and was bad.I had the same proplem with my tahoe.battery was 6 months old.
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I have to agree with Larry Grimes with this one. Check the battery first. There is no need to be chasing problems that may not even exist. The bad alternator that you replaced could have taken out the battery with it. I recently replaced the battery in my 05' and I can testify to the fact that the Ex was doing all kinds of crazy stuff with a bad battery in it.

I don't regularly drive all of my trucks enough to keep the batteries maintained. So I use CTEK chargers on them when not in use. One of the best decisions I've ever made regarding upkeep.

 

Thanks for the input folks. I charged the battery again and cleaned the tightened the battery connection very good. Will see over the next couple of days how it works out. Wife has been trained on how to connect the charger if needed.

Thanks

APEXDUCK