FD Ignition Problem - Battery Info!

[FDTRX7]

Hey Guys,

Thought I'd share a problem I had yesterday.

Had a bad battery in the daily thrasher so I took the RX for my morning work. After finishing up and finding some spare time around lunch time, headed on down to the auto parts store to get a new battery and put the RX back to bed.

Well... Got back into the RX and it didn't crank over...

All normal accessory lights were on, everything worked in the car, just turned the key and *Click* nothing....

After checking the Battery Terminals, rolling the car forward and back to see if it was a jammed starter motor I borrowed a multimeter from the auto shop.

*NOW THE IMPORTANT PART*
Battery was showing charge of 15v, but when put under 12v stress it dropped to 11v (Below cranking charge). The ECU senses the voltage and if it's too low it doesn't allow the starter to crank to prevent engine damage!

$147 later for a second battery, fired first time. (I guess it was jelous and wanted a new battery too....)

The battery that's recommended for the FD3S has a recommended Crank Charge Capacity of 620, But due to the physical size of the recommended battery, it is too tall for the mounting brackets. You're after the smaller battery with CCA 600 for a better fit.

Don't chance keeping the larger battery and not mounting it in!
- Unsecured Batteries are defectable
- It's too close to the AST! Take a left hander too quick and the battery will hit it!

*SYMPTOMS OF A FAILING BATTERY*
I found that the last few times I cold started it, Cold Start Mode didn't kick in (Revs and holds at 3,000 RPM for about 5 seconds then drops to normal idle).
This could be an indication of the battery going bad.

[13bwankel]

A good battery should never show 15V or 18V the maximum your charging system should be charging at is 14.4 so the battery shouldn't be getting above that.

IF once under load the volts drop below 12V then the amps of the battery are too low, that is caused by sulfur or calcium (depending on the type of battery) depositing on the lead plates.

Basically when the charge drops in the battery the acid starts to solidify (for lack of a better word) on the lead plates. once on there it doesn't really break down again. once the plate is completely covered in this solid calcium or sulfur the electricity can't pass though into the lead plate, and the battery "drops a cell"

When this happens it's dead, it breaks the circuit inside the battery and it no longer works at all.

Top end battery chargers have a "breakdown" cycle as part of a 7 or so stage charge but you're looking at a 200 dollar plus battery charger. AND it's only good on batteries that are still good. (think of it more as a preventive maintainance rather than something you can use to fix it)

If you want I can test your charging system to see if it's charging correctly.
James

[FDTRX7]

Thanks for the info James, I was running purely by memory typing this out.

It was a battery failure that was the problem, the altenator is charging it just fine as I had the system tested as part of the bettery replacement (Due to go back again for a second free test).

The tell tale sign I also had that the battery was old was some leakage from the top of the cell plugs (Looks like water damage), this is contributed because of the high under bonett temps.

There was also no calcified acid on the terminals.