tolsen

Battery drain

15 posts in this topic

Starter battery in my 2002 Cabrio runs flat in about a week. Current draw whilst car is locked and no consumers on is 0.15 A, equivalent to 25 Ah in seven days. 

Obviously a fault somewhere and a potential fire risk. 

 

I have as a temporary measure fitted an ingenious, dead cheap and well made China battery pole screw down isolation switch so can no longer lock the car overnight but no problem here.  

 

The master plan is to start at the rear end and go over all wiring. 

 

Must sort out this soon as planning to go mackerel fishing. 

 

 

 

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Load test your battery could be weak or a plate shorted out.

A brand new battery can be NFG freash off the shelf or any day in use from then on.

25 ah shouldn't drain a battery enough to not start a Smart

When I bought mine it hadn't been started in 6 months and It fired right up on about it's 3rd revolution about the same still for cold starts it was a bit slow as I'm sure the it wasn't at full charge we also had to dig it out off the snow bank it was parked in to open a door so it had sat a while.

Diodes in alternator are the most likely culprit for battery drain.

Disconnect the leads off of the alt and recheck your load draw.

Next is to start pulling fuses one at a time to see which one stops the load draw

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Condition of starter battery has nothing to do with the amps drawn by the car when it is partked, locked and all consumers turned off.

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i agree with Mike.  try unplugging your radio.  my was doing the same thing.

after the SAM shuts down  (usually 3 seconds after you turn off the key)  the radio is the only drain on the battery.

the battery in my car with the radio plugged in would go flat in 3 days,    i can leave the car sit for weeks with the radio unplugged,  and have no issues.

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Radio when turned off only draws 20 mA according to my uncalibrated Fluke multimeter.

 

It looks now like the fault is intermittent because battery drain measured a few minutes ago appears normal at 0.013 A.

 

I have locked the Smart with both side windows open and the multimeter reading amps between battery negative pole and chassis.

 

The culprit may be a sticking relay.  When switching on and off parking lights the amps go back up to 0.15 A, sometimes drops to the normal 0.013 A but sometimes stay constant at 0.15 A.  So getting nearer to homing in on the cause I think.

 

There also appears to be a fault in wiring to my trailer socket.  A fantastic trailer light test tool arrived recently all the way from China.  This tool tests both trailer lights and trailer light socket on the car.  All trailer lights work when connected to the car but tool tells me there is a fault with brake light.  Testing brake light on its own is OK but trailer brake light does also indicate on tool when I turn on parking lights so need to check that out further.

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A NORMAL radio only draws that much.  A faulty one will drain it overnight.  I know of two diesel fortwos that had mysterious drains that ended up being a faulty Grundig unit.

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1 hour ago, MikeT said:

A NORMAL radio only draws that much.  A faulty one will drain it overnight.  I know of two diesel fortwos that had mysterious drains that ended up being a faulty Grundig unit.

nothing about my smart is normal..  including the driver.    lol

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My Smart is behaving just now:

8CA99FF8-A839-4CA3-9D8D-D882B58AB16E.jpeg

Note the green hand knob on negative pole. Another dead cheap quality product from China. Will soon become expensive for the Americans. 

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Standard diagnostic procedure for locating an electrical component that has a parasitic draw is the following.

1. Disconnect the positive terminal from the battery and hook up the ammeter in between the cable end and the positive battery post. Your meter is now in series with the battery.

 2.  Make sure the car is fully turned off and observe the current draw. It should  be below .05 amps.

3. If it draws quite a bit more than that you start removing fuses one at a time until the current flow drops to something like .05 amps.

4. You have now isolated the circuit with parasitic draw component on it and you should be able to disconnect the few components on that circuit and further narrow the search down.

5. Sometimes you have an intermittent fault that could be hard to isolate. It could be a component, wiring or a computer. Selectively removing the suspect part could also help find the culprit.

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I measure amps between negative pole and chassis as nearer and easier access.  Otherwise I have followed same procedure but since this appears to be an intermittent fault it may take some time to sort it out. 

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Got an intermittent problem with my thirty years old microwave too. Got that one sorted. Found turning off and on contact breaker fixes it. 

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