Talk Morgan Forums Morgan Sports Cars Morgan Aero 8, 2012< Plus 8, SuperSports, Coupe & Aeromax Battery Drain Rate

After a new battery and charger I've been monitoring battery drain, possibly a bit obsessively.

So far it seems as if the battery looses 0.2v per 24 hours, or 1.2v a week.
The battery needs to be at 12.2v, minimum, to be certain of starting the engine, so 10 days is about the longest time it is "safe" to leave the car without charging, or using.
It is, of course, possible to turn everything off with the master switch, but then the radio station memory is lost.

What I want to know is what is drawing power?

It will be a whole host of items Peter.

The radio pre-sets , the ecu , the electonic modules around the car , various memories in the electronics, and probably many more.

That makes two of us Peter, please let us know if you find out.

My S4 does the same and also seems to dislike the Ctek charger I was using - which kept going into fault mode. Now using a Halfrauds unit which seems to do the job well. The boot opening button and hazard button both remain faintly illuminated, when the car is off. Techniques say this is "normal" and couldn't find any other obvious drain.

I have tried everything, even trying to talk Mrs R into getting in the boot to see if the light goes off when closed! It does, but I had to video the event myself as my powers of persuasion have obviously declined over the years.

I have a very sensitive clip on current ammeter and I went around my Classic Plus 8 checking a few residual drains and decided it was easier to throw the Red switch every time. I have left her for 8 weeks once on a holiday and she fired up straight away, the ECU soon relearns the temporary information so it makes no difference and out of interest the radio is the only remaining drain once the Red switch is thrown so I don't loose the memory on the Becker unit - this may not be the case with the Aero 8.

Difficult to comment sensibly without some more details - battery size for example. Does the car have an alarm? Does it have a tracker? Those two are the most likely permanent draws on the battery. You might expect an alarm to use maybe 40mA and a tracker a further 20 so 60 in total. Over 24 hours thats 1.5 Ah. If your battery is fully charged and is say 60Ah capacity then it will drop to 12.2 v ( half charged) in something like 20 days.

Your numbers are a bit odd. Fully charged your battery voltage is 12.7 or 12.8. 10 days to drop to 12.2 is 0.06 per day. 0.2v per day would have your battery down to 10.7v in 10 days. Are you being confused by the approc 14v voltage you can measure immediately after running the engine? This is surface charge and there is no power behind it - left to itself it will decay away failry quickly. to the normal 12.7.

On a modern "electronic " car, a stand time before you get issues of 15 to 20 days isnt unusual. Both my Ferraris have been in that bracket as is my wife's Smart Roadster

We had a friend with an Aero arrive here a couple of years back and it turned out that a seemingly good battery was going flat overnight however if he operated the inertia kill switch, thereby disconnecting the battery, it would start without problems the next morning. We went to the local auto electrician and discovered two things: 1) there was a constant drain on the battery that was enough to flatten any battery overnight, and 2) the battery was a little down on power and needed replacing.

It was too difficult to identify the source of the drain but when the battery was replaced the current drain dropped back to virtually normal for the various small items that had to remain live to some degree, central locking, radio, etc.

So it seems that if the battery is not fully up to the correct voltage some item in the car was not fully disconnecting when the ignition was turn off. With a fully charged battery the item turned off correctly.

I'm not sure how accurate (scientifically?) your conclusion is Peter (and I know you are not claiming it to be) but that is the best explanation I have come across of why Aero type cars' batteries drain excessively......

James

Can anyone advise if the close proximity of the keys to the car when it is parked could make any difference to the battery drain? I have heard that if the keys are stored close enough to the car, then the canbus (?) system doesn't shut down fully - hence more drain. My keys are usually stored indoors, but the cupboard is probably less than five feet from the fuse box of the car.

Also, I wonder could that also trigger my repeated fault mode on the Ctek charger?

I'll experiment further with key position and Ctek reconnected.

I am not aware of any proximity capability of the BMW/Morgan system unlike cars with keyless go/start. I would doubt this could be the issue.

My S2 had a trapped wire in the engine bay which was causing a consistent drain which a specialist electrician isolated and replaced. It was pretty good after that and would do a couple of weeks without a charge. It had no alarm and a Becker which retained memories. I was using the banner red bull back then. It did not have a tracker. The boot lamp is always lightly on even when parked and locked.

The Coupe does have the mother of all trackers and has never been able to do more than about 2-3 days without a drive or boost/trickle. Various lights have a mind of their own.

I still love it. Just like the wife loves a defective me. A little.

We are back from a weekend away, having driven the car about 200 miles. The battery us showing 12.9v, ignition off.
I've connected the charger, a "RING" brand device that charges, maintains, repairs and keeps a battery warm in very cold conditions. It is capable of charging at 12A in repair mode.
In maintenance mode it sarges at up to 0.5A.

The battery is new, a Yusa 60Amp device.

There is no tracker or other device and the USB adaptor is unplugged.

When the ignition is off the heated front screen with is partly illuminated for about 10 min before going out.
Also, as soon as the door is opened the footwell lights come on and the seatbelt, hazard flasher and heated screen come on.

The Radio is an Alpine device that does not have any ability to retain station information when disconnected.