Ongoing power drain issue

[Steve P]

Don`t know if you have a DAB radio, but on my Vitesse I fitted a classic looking DAB with an aerial converter so I could retain the telescopic aerial, battery started draining and I narrowed it down to the aerial converter dragging the battery down slowly, changed the wiring to a switched feed and all ok.

Steve 

[GrahamB]

How long does it take the battery to go flat? If you have a 30 AHr battery and it lasts 15 hours you are looking for a current of 2 amps or 24 watts so it will not be a small bulb.  As it has been converted to an alternator, has it been connected correctly?  Perhaps the field coils are permanently live.

[johny]

Think the alternator has been disconnected and it made no difference☹️

[SpitFire6]

On 11/02/2024 at 14:14, jagnut66 said:

Hi,

Well, one thing has remained consistent during my Heralds hiatus, that is an ongoing power drain issue.

I have disconnected various items today in order to eliminate them but one thing has made me do a double take.

To start at the beginning, the first thing I did today, having had the battery on charge overnight, was start her up and allow the engine to run for half an hour.

During which I put my meter across the battery, it read about 14.5 volts, I switched off and it dropped to about 13.5, then carried on dropping whilst I watched.........

I disconnected the alternator (to rule out backflow), no effect. The coil, no effect. The radio, no effect. The starter motor, no effect.

Then I disconnected the positive lead from the starter solenoid. with just the earth lead connected to the battery the volt reading started to go back up!?

I walked away and left it a while to make sure it wasn't my imagination.

It had dropped to a reading of 13.19 volts.

It now read 13.27 volts.

So what is going on?

I'm hoping someone on here can offer some clues or point me in the right direction.

Best wishes,

Mike. 

Hi,
It will drop from 14.5 to 12.6. You are at 13.27. No problem.

12.6 = 100% charged after resting. (Could be 12,4 to 12.8 depending on battery type)
1 volt less = 0% AKA Flat. (10.6 is dead & now with reduced life when recharged)
2 Volt more is fully charged & Charging. (14.4-14.8)

Here is my battery voltage every 2 minutes. Wet type & seen better days.

Cheers,
Iain.
 

 

ACU77L _Jan 2024_Report.xls

[johny]

When the battery was completely isolated Iain the voltage 'started to go back up' and I cant think of any explanation of that other than a drain. Does need proving though by putting the multimeter on amps in series with the +ve battery connection AND NOT OPERATING THE STARTER!

[jagnut66]

13 minutes ago, johny said:

When the battery was completely isolated Iain the voltage 'started to go back up' and I cant think of any explanation of that other than a drain.

Not completely Johny, which was the bit that puzzled me, the earth was still connected (positive disconnected).

Many thanks to all, I am reading the replies with interest, there are other (non electrical) things I need to resolve but, regarding this problem, I will start with the 'usual suspects' mentioned in the earlier posts. If anyone has more possibilities to add, please do, it could be anything at this stage.

Best wishes,

Mike.

[jagnut66]

1 hour ago, SpitFire6 said:

Cheers,
Iain.

PS: Personally I like it best in black Iain. 👍

[Wagger]

1 hour ago, jagnut66 said:

Not completely Johny, which was the bit that puzzled me, the earth was still connected (positive disconnected).

Many thanks to all, I am reading the replies with interest, there are other (non electrical) things I need to resolve but, regarding this problem, I will start with the 'usual suspects' mentioned in the earlier posts. If anyone has more possibilities to add, please do, it could be anything at this stage.

Best wishes,

Mike.

If you load a battery, then disconnect it altogether, its voltage will rise. It is a peculiar effect due to internal resistance, gassing and some inherant capacitance.

[johny]

Exactly so if on electrically isolating the battery (by disconnecting the positive lead) its voltage starts to rise you have probably removed a load and as the ignition was already off it must be a drain🤔

I would definitely prove this first though before going mad chasing possibilities...

[DerekS]

Interesting reading this.

Boot light?

Derek.

[SpitFire6]

Hi,
My understanding is that when the battery has been fully charged & battery is connected the voltage falls quicker than with the battery left unconnected?
You have tried to isolate all fuses with no success?
 

As already mentioned, fit a low-wattage lamp between the battery terminal and clamp. If it does not glow I would not worry. Milliamps are nothing.
The parasitic load could be something electronic you have added. Diodes or control if an alternator?
A series connected milliammeter was mentioned. 
Cheers,
Iain.

 

 

[Unkel Kunkel]

Modern cars  can have all  manner of systems that can remain active for varying periods of time after everything is apparently switched off, but our old cars, unless they have extras added are fairly straightforward and an old school  12v circuit with a bulb in it - ( as others  have already suggested on here ) in series ie between battery  neg.( if neg earth) and body should suffice to detect a drain.

Another approach ( advocated by Scotty Kilmer on U -tube -not  to everyone’s taste but some good advice sometimes!) to both protect your  multimeter by avoiding high current throughit   and to detect small parasitic drains, is to put a  biggish ceramic resistor 1 Ohm 10 watt placed in series with the earth lead and measure the voltage across the resistor.

(Multimeters normally  have a good wide DC voltage range)

I have used this method -when searching for a mysterious parasitic drain on a VW.

It should give a very  low reading  - in mV.

Apparently, some Mercs can ‘ normally’ have a reading of around 30 mV.

Something like an interior/ dash light on would give a much higher voltage 3  or 6 V perhaps 

Then a case of disconnecting things.

The voltage quoted after charging - as others have noted, does drop after charging and after disconnecting things as the ‘float charge’ which can be  as high as 14 or so drop-and   if it settle and stay at  12.7 V then that’s fine.

Does the battery ( assuming it’s a good ‘un) go flat eventually ?

 

 

Edited February 13 by Unkel Kunkel

[Wagger]

For those of us who were Electrical Engineers we were lucky to have the training and access to measuring kit, including AVO 8 meters and their accessories called 'Shunts'. If you can find some at auto jumbles then they can be used placed between battery post and lead and that will enable the current to be measured as a Voltage across the known Shunt. If you can find a stout 0.01 ohm shunt, then a reading of 1 volt equates to a current of 100 amps.

For tiny currents, use a 100 ohm resistor. a reading of 1 volt then equates to a current of 10mA. 10V would equate to 100mA.

I am lucky to have a test box with loads of fixed resistors on it. You are looking for currents to be less than 100mA really. Ideally, however, it should read zero on these old cars. 100mA will render the battery flat in less than 400 hours.

Using a current clamp around my battery lead, my 'Modern' has a current drain of 500mA for 20 seconds after turning  the ignition off and locking. It then falls to 20mA which would render the battery flat in 4000 hours. I do not have the patience to wait half an hour sitting in the boot watching.

[JohnD]

Wagger,

An alternative question, please!

I have a TRansit (Mk6) as my race barge, and as such it doesn't get used a lot.    I have a CTEK battery charger that lives IN the van, plugged into the battery.    When it's parked outside, I run the camp-ground 'hook-up'  cable to it from the garage and the CTEK lights up.  I just leave there , until I use the van again, maybe in three or four weeks time.  Is this good/bad/OK for the battery?

Thanks,

JOhn

[mpbarrett]

depends if its designed to be left connected to the battery. If so it will regulate its output depending on the battery state, and should not do anything bad to the battery.

mike

[Wagger]

1 hour ago, JohnD said:

Wagger,

An alternative question, please!

I have a TRansit (Mk6) as my race barge, and as such it doesn't get used a lot.    I have a CTEK battery charger that lives IN the van, plugged into the battery.    When it's parked outside, I run the camp-ground 'hook-up'  cable to it from the garage and the CTEK lights up.  I just leave there , until I use the van again, maybe in three or four weeks time.  Is this good/bad/OK for the battery?

Thanks,

JOhn

Hi JohnD.

Presumably it is a Lead Acid Battery and the charger is for those. I have left chargers connected to old batteries for years even after they have not been good enough for the vehicles and used them in computer UPS's. I can see no reason why the battery should suffer. You could periodically check the battery voltage. Most lead acid ones can be left on constant voltage chargers at 13.8 volts. It cannot be any worse than running a vehicle daily so long as no overcharging is happening.

I have lead acid gel batteries in a UPS and a mobility scooter and they have lasted for ages and are on charge permanently.

Lloyd.

Edited February 13 by Wagger

[JohnD]

Excellent!  Thank you for the reassurance!

John

[PeteH]

In recent years, I have taken to connecting small (15W) solar panels to any standing batteries, tends to be just enough to keep them "live".

Pete

[Pete Lewis]

On 11/02/2024 at 14:14, jagnut66 said:

disconnected the alternator (to rule out backflow), no effect. The coil, no effect. The radio, no effect. The starter motor, no effect.

Then I disconnected the positive lead from the starter solenoid. with just the earth lead connected to the battery the volt reading started to go back up!?

lets get back to basics 

battery mains charging 14.2 - 15v   normal

battery float charge will be less than charging voltage -  normal 

disconnect battery check voltage .   leave disconnected for 2 hrs !  check voltage  if high regen is good  if lower you have a cell problem .

connect battery with only the starter connected  . crank engine 10 seconds  should stay above 10.2 volts .if lower like 9.5v starter has issue , 9 and lower the battery is failing under load regen is around voltage 10.2 -10.8.

connect alternator  leave exciter plug off  check voltage .leave overnight should drop .5v failing diodes 3v drop isnt uncommon . 

report back after ,

 

mick 

[jagnut66]

8 hours ago, SpitFire6 said:

My understanding is that when the battery has been fully charged & battery is connected the voltage falls quicker than with the battery left unconnected

Correct Iain.

7 hours ago, Unkel Kunkel said:

Does the battery ( assuming it’s a good ‘un) go flat eventually ?

It did once but I have since recharged it.

 

38 minutes ago, PeteH said:

In recent years, I have taken to connecting small (15W) solar panels to any standing batteries, tends to be just enough to keep them "live".

Pete

Interesting, something for when the drain has been traced and fixed though.

Do you have a link(s) to the set up you use?

Best wishes,

Mike.

[jagnut66]

9 minutes ago, Pete Lewis said:

lets get back to basics 

Thanks Pete.

Edited February 13 by jagnut66

[Pete Lewis]

is there really a problem here or are we chasing a nothing 

if its charging and does it actually go flat (well low enought to not start) 

the herald is pretty basic with few things to really drain rather than voltage variations 

Pete

[Wagger]

As PeteL has inferred, have we made this too complicated? It is very easy for me to add stuff that is a bit OTT on electrics. If there is an unwanted load that cannot be found, fit a battery isolator. That will stop unwanted drain.

Look for added items like radios and alarms. Previous owners may have done mods that are wired to the wrong fuse etc.

[johny]

All this could be clarified very quickly by setting the multimeter to the highest DC amp scale (maybe changing lead positions on it) and, with the ignition off, connecting the meter between a battery terminal and its disconnected lead. You dont have to touch anything else to see if theres a drain current showing - please put us out of our misery Mike!

[DerekS]

At risk of nagging, Is there a boot light fitted? If so, is it going off and staying off as it should?  Can be a problem...

Derek.