Charging A Flat Battery

[br1anstorm]

My IS300 Sportcross has been sitting outside and hasn't been used for about a month (I've been away). Tried to start it this morning, and the Battery was totally flat (even the remote unlock wouldn't work and there's no interior light).

I assumed that - as it's been sub zero most nights - this must have affected the Battery, although it's worrying that it shoudl go flat in a matter of a few weeks. Maybe there is a power-drain somewhere. But as a first step, I thought I'd connect a trickle-charger to revive the Battery, which is what I normally do with any of my other cars

I thought I would do so without disconnecting the Battery terminals, so as not to deprive the security/alarm systems etc of power. As soon as I connected the charger there was a regular loud "clicking" sound from somewhere in the engine bay, and the needle of the charger twitched along with the clicks. When I switched off the charger the clicks continued, and only stopped when I physically disconnected the charger from the Battery terminals.

What does this indicate? I'm no auto-electrician, but this doesn't seem normal. Does it mean there's a major power-drain or bad connection somewhere which is the source of the clicking sound?

Meanwhile I have disconnected and removed the Battery and have started trickle-charging it separately . I am wondering whether to put it back and try using a booster-battery to jump-start. But before doing so I'd like to know what caused the clicking sound, in case connecting another Battery via jump-leads risks doing harm.

Any thoughts/comments would be appreciated.

[dave1]

If you use a booster to jump it try to make sure it is antisurge. Best bet is to call your breakdown provider as they will have antisurge booster capabilities.

It is always best to disconnect the Battery and remove it before charging.

[br1anstorm]

Thanks, dave1 - I wasn't planning to use one of those booster packs, just jump-leads from another Battery (which according to the owner's manual is OK, provided of course the connections are done correctly!).

In fact while the Battery was out of the vehicle and charging, I spoke to a Lexus tech guy on the phone. His verdict was that the clicking was a relay trying to activate (possibly for the anti-theft alarm).

In the event, once the Battery was recharged I reconnected it. The alarm then went off - which was a relief - and I was able to switch it off using the wireless remote in the normal way. A decent road -run to warm the engine and get the Battery fully charged seems to have dealt with the problem.

I would however like to check to see if the Battery goes flat again. Can anyone tell me the best way to measure the small current drain that does normally occur (radio-memory, alarm, etc) when the ignition is switched off, and what should the reading(s) be?

[dave1]

Glad you got it sorted quickly and easily. It would probably be worth another phone call to your Lexus tech guy who should be able to give you the correct info.

[Donkeymc06]

As far as i know the only way to check the current draw without access to an oscilloscope and a current clamp... is to wire an ammeter (multi-meter) in series to the circuit, basically take one of the connections of the Battery and connect one lead of the meter to the Battery pole and the other to the lead you took of the Battery... just be careful if you take the positive lead of the Battery dont let it touch the the body of the car or the negitive terminal...

Another thing to check is the condition of the Battery, make sure the electrolyte is about 2mm above the cells, then use a hydrometer to check the electrolyte..

[steve2006]

If you want to check the parasitic Battery drain this link should explain how to.

http://flashoffroad.com/electrical/Batteries/BatteryDrain.html

[dave1]

If you want to check the parasitic battery drain this link should explain how to.

http://flashoffroad....tteryDrain.html

Interesting link Steve.

[br1anstorm]

Thanks, especially to Steve2006 - that linked web page was exactly the advice i needed. And I knew there had to be a specific tech term.... "parasitic Battery drain"!