Battery drain

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Cunna456
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Battery drain

Post by Cunna456 » Tue Apr 30, 2019 10:13 am

I'm sure this has been asked a thousand times but its really bugging me now.
So I put a brand new battery on my polo in the evening and didn't start it, didn't even open the doors (bonnet was already up). The next morning it started fine, however after being started, driven and stopped, within an hour the battery was completely flat. I've obviously got a drain but cannot determine it. It doesn't start to drain until the engine has been started and then stopped again. However when I disconnect one terminal to attach my ammeter to try and locate the drain it doesn't have a current pull that would kill the battery. So whenever I disconnect the battery it disappears. I was hoping someone may have had the same issue before and could help me out.

RUM4MO
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Re: Battery drain

Post by RUM4MO » Tue Apr 30, 2019 7:43 pm

A couple or so questions:- does the charge warning light come on when the ignition is switched on and the engine has not been started, is so, does it go off as soon as the engine is running? What is the voltage across the battery when the engine is running at about 3K RPM with the headlights and rear window heater on?

Matt Brighton
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Re: Battery drain

Post by Matt Brighton » Thu Jul 04, 2019 5:15 pm

you tube search "eric the car guy - parasitic battery drain" and that will help you trace the source of the draw.

Best

Matt

Aybesea
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Re: Battery drain

Post by Aybesea » Thu Jul 04, 2019 11:52 pm

I had this problem ,in the end found it was the OM Beta radio i pulled the fuse which is on the right end of the dash,right bank of fuses IIRC it is the 4th from bottom but best to check.It took me ages to suss it out Still got the old radio fitted just havent got round to replacing it yet. I had the alternator checked which was replaced as that was not working to well but made no difference that is when i removed the fuse.I had the same syptoms asyou start ok then go out 2hrs later and battery had not enough volts/amps in it.

Mabe
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Re: Battery drain

Post by Mabe » Tue Aug 13, 2019 3:55 pm

I suggest two things to check: Load drain and Charging.

Load drain problem:
I have read elsewhere that when the car is in sort of sleeping mode, with no loads or switches or lights On, do the following (but only if you are confident that you know what you are doing). I have not done this myself.
Disconnect battery negative and insert a DC ammeter between battery negative terminal and the disconnected negative cable lug. The Current should not be greater than 75mA (0.075A). If it is, there could be something draining the battery and some faultfinding by systematically removing fuses would be needed.

Charging problem:
With the engine running, I have a DVM measuring the voltage across the battery. From what I have read, it seems this should be around 13.7 Volts. In my case the more or less steady reading was 12.8V. Accelerating to 2000 rpm did not make much difference. However I noticed on the DVM some sort of momentary flashes of around 13.6V, among the much more steady 12.8V (no consumer loads on. Charging voltage dropped slightly when aircon was briefly switched On). I am not sure if this Voltage is what it should be or if there could be a fault (typically a faulty diode or something).

RUM4MO
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Re: Battery drain

Post by RUM4MO » Tue Aug 13, 2019 8:27 pm

The trouble with that plan is that by disconnecting any battery leads, you will immediately re-waken the controllers, so the drain current will be a lot higher, this is where knowing/understanding what you are doing comes into its own, what you need to do is to fit a current meter (DVM set on current) set on a low range, in series with a battery terminal and before reconnecting that battery lead, apply a short circuit to the current meter terminals. Wait for maybe 45 minutes, remove the shorting link, then read off the "sleeping" current. I have my own way of doing that by using a current lead that the loose battery terminal can be passed over at the correct time.

Mabe
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Re: Battery drain

Post by Mabe » Wed Aug 14, 2019 6:04 pm

Yes, great idea. Makes sense.

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