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MG Midget and Sprite Technical - Alternator / Battery issues NMC

I have an issue with the wifes Mazda 2 (63reg) which she no longer drives so it gets periods of inactivity (3-4 weeks).
About a year ago the original battery went down so as it was 'getting on' in age, so I replaced it with a h/d Varta - again after about 4 wekks layoff - would not start - so recharging first with my trusty old charger to get it going then the newer 7 amp computer one.

This has been ongoing and I originally thought the parasitic loads of alarms etc was the cause, over the last week I have recharged the battery and got it up to about 12.4 volts so not brilliant - when I run the car initially I get about 14/13.8 but it rapidly drops to about 12.6 @ 2000revs.

So i'm thinking have I got an alt issue after all - diode leaking current when switched off etc + why would the voltage drop soon after starting below the normal say 13.8volt alt output when the battery voltage before starting was down to 12.3 ?

I am assuming that the Mazda does not have a smart charging system (like the Adverc in my old yacht had) and is a basic unit ?

This is rather annoying me as I can't figure it out - probably have to take it to the local garage to get the alt tested out.
richard b

When you say 63 reg --what year is that, not 1963
Depending on the year model it could be normal, if it has a battery voltage sensing system it'll drop like that if there's no load, you could try connecting your volt meter accross the battery, wait till it drops and then turn the lights on, it should bounce up to the 13.8 range for a little while like that then drop back to the 12.5 again

Just depends on the year model-----?
William Revit

Hi Willy,

Its a 2014 car - the registrations here now have a double didgit in them to identify the year - some people just have to be the first to get the latest plate each year !
63 is 2013/2014.

Its the problem of self discharge that seems most worrying as this is not even in very cold conditions - yet !
richard b

Haha Willy, we've been here before. Remember the thread about your midget and when/where it was registered? Maybe we didn't go into too much detail about the more recent registrations.

'63' is registered between 1st September 2013 and 28th February 2014.

Here's a list from DVLA leaflet INF104.

If you want full chapter and verse, it's available here

Edit: Took too long and Richard got in first.

Dave O'Neill 2

Re. 21st century UK date vehicle registration sequence.

I know I'm really old, but . . . it took me ages to get my head around the two digit date sequence.

It's easy: the first digit (of the two digit date sequence) signifies the 'decade and month' of registration, the second digit gives the 'year of the decade'.

For the first digit, bear in mind that the first decade has March registration as number 'O', and September registration as number '5'. With incrementing numbers for subsequent decades.

With that in mind, any vehicle's registration date can be solved without having to use a look-up table.

J Thomson

Below might be easier for Willy to see on his "smart" device - it ends just before 63 reg but the pattern is easy to see.

Nigel Atkins

Did you photo all of those yourself Nigel? Must have taken you a while.

Who else can remember collecting car registration numbers? The ultimate was to get an example of every registration authority (pre DVLA of course) or to get a long numerical sequence. I didn't get very far with mine, mostly I think because we didn't have a car so never got very far from JO and WL

If you consistently get 14v at start up, I bet the alternator is ok. As Willy says, turn the headlights on to see if the fall in charging voltage is restored. You could put an ammeter in series with the battery to see what is happening with ignition on (engine off). Current should be lowish but enough to flatten battery over time . Then turn off ignition and see if current falls to zero after a while - modern cars need to "go to sleep". I have an intermittent problem with my V70 flattening its battery whilst at rest. I'm of the opinion that there is an intermittent parasitic discharge, possibly caused by a door sensor not switching off sometimes i.e. so the car doesn't go to sleep properly. Hard to diagnose but worth considering imv.
Bill Bretherton

I presume this car doesn't have regenerative braking?

Guy, if I had taken photos the numbers would all have a downward slope to the left.

I got it off the net somewhere I think, (might have been DVLA?) can't remember now, here's the previous for Willy and others.

Nigel Atkins

Might as well finish the set, for those that don't already know (like me for a very long time) note 'E' reg dates.

Just noticed the letters are shown as being at the start of the reg plate which is incorrect, they would be at the end of the reg plate, i.e. ABC 123A (for 1963)

Nigel Atkins

(timed out)

I gave a poor example with two As, better would be -
i.e. BRP 123A, the A at the end for 1963.
Nigel Atkins

Well I'm glad we have sorted out my reg date !!!

Having had a search it seems that its not an uncommon problem but solutions seem few and far between.

I did try turning on the lights and fan motor whilst reving and the alt did pick up and seemed to stay up at about 13.6

I need to use the car tommorrow so will check voltage before I go (having put a bit of load on the battery to get a true reading) and when I return.

I think then I need to start hunting parasitic loads as Bill notes.

richard b

yes reg date problems are not uncommon. :)

First thing I found on a quick search was the following, you may have already seen though - new (specific) battery seemed to solve this chap's issue, over 2 years of proof -

Also only today, whilst researching something else, I read about another issue where the parasitic drain on older cars was radio/CD player switching to 'on' whilst car the car is 'sleeping'.
Nigel Atkins

Sounds to me like your car has what is known locally here as the smart charging system--
These systems usually run quite a large battery, 550-650cca
To be honest they are a real pain
I've had people do a 300klm trip and stop somewhere at the end and their car won't start as there wasn't any load on the system to activate the alternator, the battery just sits there and goes flat unless something like the lights or heater fan etc are sensed
The actual voltage regulating is done by the engine's pcm
IF --your car is the same as the Ford/Mazda here you can take it into your dealer and they can download the vehicle data and switch things on and off, there are heaps of options like automatic locking ,drive off locking, daytime running lights ,etc
One of these options is the charging system
There will be an option for battery sensing-This needs to be changed over to non-sensing-
By doing this the alternator will then charge like an ordinary alternator and run at the expected 13.8-14 all the time
Luckily your car should be able to be switched over, the option of changing it has been removed from the list on new cars a couple of years ago

It's a real pain on vehicles like the Ford Ranger utes that get used a lot here for towing caravans etc---The poor old owners go out and get a secondary battery fitted for their caravan with a cutout and the cutouts operate at 13v-----With a normal charging system the second battery gets charged up as they drive along but with the smartcharge system dropping back below 13v the second battery doesn't get charged
The only other thing that 'might' be causing an issue for you is that if the car is kept in a garage unlocked there can be a drain through an alert body module
Not sure on a Mazda2 but I know on Subaru and some Kia cars that the car has to be locked to turn the module off otherwise they draw about .05amp and gradually run the battery flat over a couple of weeks
Late model Subaru WRX are really bad for it and have to be put in what they call storage mode by locking the car twice within 3secs and that turns everything off except the alarm and locking which go into a non current drawing mode as well
Hope this helps
William Revit

Willie, this is exactly why I asked if it had regenerative braking.

With regen braking the "smart" alternator switches off early to allow capacity in the battery to take the regen charge. Second battery and solar panel control systems don't understand this and won't switch over until the main battery is fully charged so everything just goes flat.
Fitting out a day van the electrician couldn't work out what the problem was so my son in law asked me to see what I could do with it. It took a lot of searching on the internet to find out what was happening.
I should have asked here! You would have told me!

"second battery gets charged up as they drive along but with the smartcharge system dropping back below 13v the second battery doesn't get charged"

Thanks for explaining the rego numbering system I can actually understand that, but splitting it into 6 month lots makes it messy---Would have been a lot simpler as 2000==00

Thanks for that info Guy
I've never worked on something with Regenerative braking but good info to store in the old head
William Revit

Willy, your post at 23.54 makes a lot of sense and I've learned more from it! My understanding from Richard's first post is that the battery has drained after the car has stood a while which is what I've been experiencing myself (not currently) so does that point to an "alert body module", as you describe it, not shutting something down properly or some other parasitic drain? As I suggested, an ammeter in series with the battery (I mean a DMM on a 10A range carefully connected and placed externally) might indicate this sort of problem over time.
Bill Bretherton

Willie, the regenerative braking was on a T7 series VW van, - so nothing very flash! I don't know if they all have it, or maybe just some models, though presumably the alternator control is a software option.

tbh, I have no idea how regenerative braking actually works. I know what it is, but not the how of it!

Cheers Guy

and Bill
As you say the only real way to find if there's a drain is to get a meter into it and see what's happening
My Bosch scope has a magic amp meter with an inductive pickup that makes life easy

Just out of interest
I had a fella with a Kia Carnival wagon that he used for going fishing, he would leave a side door open and sit in there in comfort with his rod out the side (luxury fishing)but his battery would go flat with the mass of internal lights so he pulled all the globes out to stop that which was ok for that purpouse---anyway one night he left the wagon in his garage with the door open to air the thing out and overnight the battery went flat and he came to me to check why--Hooked it up and found even with the globes out the current draw was 1.5amp with the door open and almost 0 shut, so with the door open the body module was still active and feeding drivers and possibly a relay---after shutting the door it would still draw for about 20 secs and then taper off to almost 0(the globes would have dimmed off if they were fitted) Then that last little bit of draw wouldn't go away till the doors were locked and even then it hung in there for about 1/4 of an hour then dropped to 0
William Revit

Yes, I found with my V70 that it took a while to "go to sleep". The battery is below the rear cargo area (estate/ wagon) so I could connect a meter up and view it through the rear window but your scope would be much better. Cars are almost too complicated now!
Bill Bretherton

And it is even worse with keyless: when the car detects that the key is around the car, it starts a lot of computers and lights, thinking you will get in and drive.

The Lexus does this, but she is parked in the street, so usually, if I walk near by, it is to go for a ride :)
But if you have your car in a garage where you go often to pick up things, and always keep your keys in your pocket/jacket, then you "wake up" the car quiet often ;)

Much harder to wake up the Midget... :D

(Don't get my wrong, I love the keyless: car's key almost never move from my jacket's pocket)
CH Hamon

Its one of the reasons why I like the Midget. All this technology - key less entry, smart charging, adaptive cruise control etc just leaves me cold.

I'm all for technology making life better and safer but it has to work properly otherwise (to me) its pointless and at best irritating.

Sorry, rant over. As you were....
Chris Madge

Chris I totally agree - this is a small fairly basic runabout car but simplicity seems impossible to obtain these days !
The smart charging (?) is also now linked to the endless drive for mpg - reduced engine load etc.

Thanks Willy for explaining the Ford/Mazda system - i've read up a lot more now and have a basic grasp of what I consider as the unwanted tech on a small runabout car.

Did a parasitic load check with the amp meter and found it dropped to 0.02amps after a while with the car shut down and doors locked etc. i.e about 0.5 amp/hour per day and 15amp/hour per month - can see my problem now as the car does have that sort of period of inactivity now my wife no longer drives.
That would pull the voltage way down especially if the battery is not fully charged to start with.

Found the best way to get the alt up to 14v is to put the heater blower on full ! No wonder these batteries get sulphated.

I thought the bonnet was unmonitored (I had locked up the car with only the bonnet open) however when I dropped the bonnet the indicators flashed 'good bye' to me !

On a seperate subject the setting sand in the block paviors is doing a fine job - only a couple of weeds where a bit of settlement movement has occurred, it has now seen a couple of summers - have you tried it as yet ?

richard b

I believe the reason why we have new registration dates twice a year is that it evens the new car sales out through the year; some of us Brits are a vain lot(!) and sales always peak at the start of the new reg.
J Smith

Last year, one of the older regulars at Loton (He must be 80ish but still goes like stink) ran a very quick Focus RS with keyless ignition.

At one event he shared it with a friend. After the friend's first run, the car was dead when he came to re-start it in top paddock to return down the hill.

The 'key' was still in the owner's pocket half a mile away in the main paddock!

It took a while for them to live that one down.

Probably not a good idea to let SWMBO borrow your keyless car to go shopping without making sure you've handed over the key!
C Mee

Richard it sounds like you need one of those trickle chargers to plug in to when its parked up in the garage.

Or sell it if its np longer getting used.

did the current draw change between bonnet open--shut, I'd imagine with it up the body module would still be alive and monitoring it

Funny you should ask about the setting sand, I've been waiting for the weather to dry out a bit and only last weekend high pressure water blasted the area (again) and as soon as that has dried right out, which it nearly has it's going to happen, the plan is to sweep it in and go over it with a vibrator/whacker and resweep till the sand has gone right in all the cracks then give it a light hose in to set it-----------sound ok to you

It's been on/off wet here for months and now and with the bushfire season on the Mainland starting early, it's a bit of a worry with all the growth about the place
We're fairly safe here on the coast but already the temps are up and it's not even summer yet-It hit 37C in Hobart yesterday till a change came through then it dropped like 10 deg in 10 mins.-----weird
William Revit

I didn't check with the bonnet closed as it was news to me that it was monitored will have to find the switch.
Would need to rig up some extension wires to do that check - one day may be !

Back to the s/sand - I just brushed mine into the gaps with a soft sweeping brush, important to get rid of surplus as it would leave a cementy wash colour on the blocks.

Be very gentle with the water as it only needs to be wetted sufficently to activate the cement, too hard and it will be washed out - need a good forcast for following couple of days ideally.

Oh if you do use a hose put rags in the drain outlets to contain the cement fats, as any run off slurry will cause issues with the drains.

richard b

Saturday morning--rain
MG concours here today as well so that'll be a bit of a fizzer
Good tip with the drain, I've had trouble with that before and it was a disaster, the drain goes straight down the back wall of the house for about 12-14ft through beach stones which are a real pain to dig out---rags it is--if it ever stops raining
William Revit

I think the battery has been damaged by going a bit flat a couple of times - well enough not to start the engine - modern batteries seem less able to recover - probably closely packed plates etc. So i have replaced it with the correct size and will see how that performs.

Does anybody know what the 'correx' loose plastic box around battery sides on the car is for ? Didn't quite fit the new one (correct number) so i've left it off for now.
Batteries never used to have a loose jacket !
richard b

insulation against heat and cold.

Lift the bonnet of old cars and you can walk around the engine bay, modern cars you can't get a fag paper in, lots of components fighting for space giving off their heat and reducing insulating air gaps.

Plus the amount of electrical items on an old car is minimal compared to modern cars, modern batteries have a lot more to do and more often as we've read in this thread. They also need to be very reliable as modern owners aren't used to driver and service maintenance as much as us very ancient folk.
Nigel Atkins

(missed the edit)

ETA: as regards the battery going too flat - I assume you used an old slow low rate charger to try to bring it back as the more modern and/or higher rate chargers to me don't seem to do as well as the old chargers. IIRC (very) slow discharge is best treated with (very) slow recharge. I always give a car battery two chances as it is one of the most oversold car components but I also want the car to always start without the slightest hassle so don't hesitate to change the battery if required.
Nigel Atkins

Hi everyone
What would you see as an abnormal parasitic load in a relatively modern basic car - Iím around 750mamp which seems high


That does seem too high; at that rate the battery would be flat in about 3-4 days. (4x24x0.75 = 72 A/hrs)

How long are you leaving it before you are checking the current. I know my car takes about 30-40 minutes before it goes into 'deep sleep'. IIRC the drain after that is about 30mA.
J Smith

That seems far too high to me - as noted you need to let the car go to sleep with doors locked etc before checking - mine takes about a minute to shut down systems.
Then if high start pulling fuses whilst monitoring the current draw to try and identify the faulty item.

A starter type battery will be damaged if it goes below about 10.5volts and at this level any warantees are voided (DAHIKT). If you totally flatten modern car batteries they don't recover well and many modern battery chargers will not even start to charge them - you can often start the recharging with an old style charger which does not have a computer chip in sight !
However care needs to be taken as the battery can if it get hot spurt its acid out !
richard b

This thread was discussed between 17/11/2019 and 02/12/2019

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