12 replies to this topic

[maccers]

My battery is losing charge very quickly, within a week of it being fully charged using a mains to 12v charger but not using the car at all. I think it may be the ECU as its the only thing I have added that's different from when the battery held charge for weeks with no car use.

 

Its a Halfords year old one, biggest one with max cranking power I could fit into the battery box.

 

How do I see if any device fitted is drawing any power? I have a digital multimeter with voltage, current, amps etc but just wanted to know where to put the probes to measure it?

[Captain Mainwaring]

This may sound sarcastic, but are you confident using your meter?

If you are then you can go ahead and try. I only ask because you can damage your meter if not.

Go for DC 10A first with battery term disconnected and series your meter between battery terminal and clamp - this will let you see if anything is leaking.

 

Do take care - messing with batteries an ammeters can ruin your day and burn your fingers.

 

You could also do the same thing at the starter term if you prefer but the same caveats apply.

[maccers]

Thanks for that, I will give this a try. Assume its then just a case of pulling fuses to identify what drawing power?

[zony]

Make sure you have at least 10A DC otherwise the meter will fry. Some things do draw current all the time, clock, alarm etc but you should be looking at no more than 50 - 80 mA per hour.

[maccers]

Tested at battery, 0.13 draw. Remove radio fuse and re-test shows 0.00 draw. I do have an alarm LED connected but this shows up as 0.00 on meter, so maybe so small.

 

Is 0.13a draw usual for a radio for memory etc? Its an Alpine semi decent model.

[mini13]

yeah that seems reasonable,

[xrocketengineer]

What kind of ECU are you talking about? If it is a SPI ECU, the drain can be difficult, if not impossible to measure but it can still be there. It is a "smart failure" because it sets and activates the main relay in the relay box when the car is started, but when the engine is turned off, the main relay remains active draining the battery over a couple of days. The failure resets when the battery dies, the battery is disconnected or either one of the two connectors on the relay box is momentarily disconnected. The other symptom besides the battery dying, was that the relay box was warm to the touch after sitting overnight with no use.  

This scenario could happen with other electronics too.

 

http://www.theminifo...-smart-failure/

[maccers]

Its an Emerald retro fitted ECU to drive my injection/eaton s/c setup. I run the ECU from switched only. The ECU has 2 12v feed wires, one switched and one either constant live or switched, I opted for both on switched feed. I pulled the master fuse that I have put inline between battery live and 6 * fuse box for the various bits needed for injection, made no difference when doing the multimeter test, only thing was the stereo.

 

I left the auto charger on the battery all day, started from 12.8 to 14.4, then went back to 13.3, so maybe the battery is past its best?

[KernowCooper]

The battery should read 12.65v which is a fullycharged voltage reading, and the voltage should be check after a 8 hour period otherwise you'll get a false reading,

[Captain Mainwaring]

Tested at battery, 0.13 draw. Remove radio fuse and re-test shows 0.00 draw. I do have an alarm LED connected but this shows up as 0.00 on meter, so maybe so small.

 

Is 0.13a draw usual for a radio for memory etc? Its an Alpine semi decent model.

 

 

Too much I think - that's nearly 1.5 watts - a sidelight is 5 watts....if your battery was past it's best....it would take the edge off it.

Memory shouldn't need anything like that to sustain..

[maccers]

Hmm, its definately the radio, as when I pull the fuse for that, there are zero amps drawn. I'll just have to remember to keep the battery charger on it in condition mode.

[Captain Mainwaring]

Hmm, its definately the radio, as when I pull the fuse for that, there are zero amps drawn. I'll just have to remember to keep the battery charger on it in condition mode.

 Doing a search....it should be between 25-40 mA...or 0.025 Amperes......

Edited by Captain Mainwaring, 27 June 2013 - 11:29 AM.

[maccers]

The battery level is dropping slowly to around the 12 mark over the past few days after charging to the maximum and then leaving it, with no connections on it.

 

I'll look in the Alpine manual to see if they list a current draw for the memory. I dont even really use the radio much anyway when driving...!