Battery Flattening Issues

Steve Wasteney

Member
Original poster
Supporting Member
Joined
Nov 16, 2015
Messages
43
Location
Southampton UK
A couple of months ago I started to get a flat battery every couple of days. I thought (because I have no idea how old the battery is) that it was probably time for a change. I have fitted a good quality heavy duty battery.
The problem is still there and possibly worse, as in flat every day now. There is nothing obvious but it must be a heavy drain to flatten the battery overnight.
Is there anything on the TJ that commonly fails to create this fault? The Check Engine Light stays on all the time and has done since this fault started occuring. I have used diagnostics which registered a stored code for the throttle position sensor. I changed that also, reset the code and it comes straight back. Could these faults be related ?
Any help would be really appreciated.
 
I don't think a TPS could have anything to do with the battery.

I'd be more inclined to look at the alternator as the culprit.
 
In your case, I would disconnect the negative battery cable from the battery, hook up a test light from cable to battery post. If test light is lit, pull fuses until test light goes out. See what fuse shuts the light off. That should show you what circuit is draining battery.
 
In your case, I would disconnect the negative battery cable from the battery, hook up a test light from cable to battery post. If test light is lit, pull fuses until test light goes out. See what fuse shuts the light off. That should show you what circuit is draining battery.

Good, solid trouble shooting advice right there!
 
  • Like
Reactions: Frank and Stinger
In your case, I would disconnect the negative battery cable from the battery, hook up a test light from cable to battery post. If test light is lit, pull fuses until test light goes out. See what fuse shuts the light off. That should show you what circuit is draining battery.

X2. This is solid advice.
 
  • Like
Reactions: Frank and NateD
UPJOHN called it. You have some kind of drain you need to find. On another note, never heard a dead battery called "flat" before.:D
It's British. One of my grandads would say "damnit boy, you ran the battery flat!". But that was on an old tractor with a very weak 6 volt system.
 
  • Like
Reactions: Chris
Speaking of British... I friggin LOVE Broadchurch!!!!

Gotta be in the top 3 best shows I've ever seen.
 
Thanks for the comments guys. Will get on with testing at the weekend.
I know that over there you call it a dead battery. Problem on this side of the pond, we refer to a battery as dead when it has finally had it and can't be recharged.
 
  • Like
Reactions: Chris
One thing that can cause such a fast drain of a battery is a bad/shorted rectifier in the alternator. It can still charge somewhat but the shorted rectifier (diode) will suck a battery flat/dead in short order. Improperly installed relays and ignition system immobilizers are also common causes of dead batteries.