Charging dead battery, relay constantly clicking

[LTC8K6]

The batteries aren't the problem, the problem is the very high parasitic draw from all the electronics, alarms, keyless entry, push button start (RFID) crap. Disabling the SmartKey system on the Toyotas makes a huge difference in lowering this parasitic draw but you can't do that on the newer cars anymore which totally sucks. On the first gen cars with the smart key system, you could disable the system with a button under the dash but with the newer cars, you can't do this and you basically have to live with this very high parasitic draw which is a problem if you drive your car infrequently.

My Jeep has IOD fuses. If you are going to let it sit, you remove these fuses. This ends most of the parasitic draw.

IOD fuse-Ignition Off Draw.

http://www.wkjeeps.com/wk_fuses.htm#DRAW

http://www.wkjeeps.com/wk_fuses.htm#IPM

 

[phucheneh]

The draw with the car at rest is not very much. A fraction of an amp. If it's causing a discharged battery, even after the car sits for a few days (hell, weeks), something else is wrong.

The exception would be if the car is being operated with the battery at a habitually low charge- e.g. you use the car to make a bunch of short, low-speed trips. Possibly with long periods of sitting in between intermittent bursts of said trips. That can be hard on any car, and I've seen it cause no-starts on pretty new cars where there was nothing else to blame. Seen TSB's from manufacturers about it, too.

edit: but that's not a parasitic draw issue. It's a 'using electricity faster than the car is making it' kind of issue. A few crank of the starter motor is a lot more significant than sitting for a day.

Also, on the draw thing: if you actually check it with an ammeter, you need to give newer cars a little while to settle down. Think of it like a normal Windows PC- you tell it to shut down, but it wants to take some time to make sure everything is in order first.

 

[LTC8K6]

IIRC, if you leave the IOD fuse out on the Jeep, when you turn the key on, you will see a message telling you the fuse is missing.

 

[tortillasoup]

The draw with the car at rest is not very much. A fraction of an amp. If it's causing a discharged battery, even after the car sits for a few days (hell, weeks), something else is wrong.

The exception would be if the car is being operated with the battery at a habitually low charge- e.g. you use the car to make a bunch of short, low-speed trips. Possibly with long periods of sitting in between intermittent bursts of said trips. That can be hard on any car, and I've seen it cause no-starts on pretty new cars where there was nothing else to blame. Seen TSB's from manufacturers about it, too.

edit: but that's not a parasitic draw issue. It's a 'using electricity faster than the car is making it' kind of issue. A few crank of the starter motor is a lot more significant than sitting for a day.

Also, on the draw thing: if you actually check it with an ammeter, you need to give newer cars a little while to settle down. Think of it like a normal Windows PC- you tell it to shut down, but it wants to take some time to make sure everything is in order first.

True, however in the circumstance like you've described, when I disable the SmartKey system on vehicles that allow me to, the resting battery voltage is significantly higher than when it's still enabled. Like if I come to the vehicle like 2 weeks or a month later, the car with the Smartkey enabled will have a battery resting voltage of 11.9V connected but if that same car had the SmartKey disabled for the same period of time, the resting voltage is like 12.3V. Parasitic draw really does add up and alternators are really just battery maintainers, not chargers.

 

[LTC8K6]

IIRC, 11.9V no load is completely dead for a 12V lead acid battery.

 

[tortillasoup]

It's not "completely dead", just fully discharged technically speaking. You can easily crank the engine with a charge that low FYI. Anyway but yeah the smartkey is a huge power draw and disabling it really helped with that issue.

 

[LTC8K6]

It's not "completely dead", just fully discharged technically speaking. You can easily crank the engine with a charge that low FYI. Anyway but yeah the smartkey is a huge power draw and disabling it really helped with that issue.

No, 11.9V without a load is a very low SOC, iirc.

Be very surprised if it cranked over an engine.

 

[tortillasoup]

No, 11.9V without a load is a very low SOC, iirc.

Be very surprised if it cranked over an engine.

Well a group 26 battery at 11.9v is certainly going to have an easier time than say a group 51 at that voltage...

 

[Zenmervolt]

You can easily crank the engine with a charge that low FYI.

No. You cannot. Not unless what you have are 5 perfect and fully-charged cells with one bad/reversed cell.

If the battery is otherwise good, a no-load voltage of 11.9 volts means the thing is dead. It won't crank an engine. Period.

ZV