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Chat Area => General Car Chat => Topic started by: Auto Addict on 16 July 2017, 07:44:08

Title: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 07:44:08
From time to time I like to codition charge my car battery to try and keep it in tip top condition.

The Merc has 2 batteries, one undr the bonnet and one in the boot.

There is a dedicated charging point under the bonnet for attaching  the + and - clamps from the charger.

Question is, does the charger then try to charge both batteries at the same time?

If it does, I can't see how it could go through the conditining cycles :-\
Title: Re: Merc 2 battery question.
Post by: TD on 16 July 2017, 08:15:07
The 'charging points' I think are for jump starting .... if you have a look I believe they will have gert big cables to them  :)

I would have thought the 'charging points' are connected to the battery connected to the starter only.
The other battery being a separate circuit for running electrics and gets charged from the alternator only....
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 08:25:35
The 'charging points' I think are for jump starting .... if you have a look I believe they will have gert big cables to them  :)

I would have thought the 'charging points' are connected to the battery connected to the starter only.
The other battery being a separate circuit for running electrics and gets charged from the alternator only....

According to the manual they are charging/jump starting terminals.

The + goes straight to the + on the battery under the bonnet and the - goes straight to ground on the body.
Title: Re: Merc 2 battery question.
Post by: TD on 16 July 2017, 08:50:40
The 'charging points' I think are for jump starting .... if you have a look I believe they will have gert big cables to them  :)

I would have thought the 'charging points' are connected to the battery connected to the starter only.
The other battery being a separate circuit for running electrics and gets charged from the alternator only....

According to the manual they are charging/jump starting terminals.

The + goes straight to the + on the battery under the bonnet and the - goes straight to ground on the body.

So, be fine to use for charging then  :y

My other point about the other battery being on a separate circuit still stands, having them connected in parallel all the time makes no sense to me...apart from looking at a wiring diagram I guess the other way to prove its separate, is to disconnect the + from the one in the boot and see if the lead still has 12v on it....
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 09:14:15
The 'charging points' I think are for jump starting .... if you have a look I believe they will have gert big cables to them  :)

I would have thought the 'charging points' are connected to the battery connected to the starter only.
The other battery being a separate circuit for running electrics and gets charged from the alternator only....

According to the manual they are charging/jump starting terminals.

The + goes straight to the + on the battery under the bonnet and the - goes straight to ground on the body.

So, be fine to use for charging then  :y

My other point about the other battery being on a separate circuit still stands, having them connected in parallel all the time makes no sense to me...apart from looking at a wiring diagram I guess the other way to prove its separate, is to disconnect the + from the one in the boot and see if the lead still has 12v on it....

Disconnecting batteries on a Merc can lead to all sorts of problems, so I'm lead to believe :(
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 09:21:20
Are you SURE that there is a direct link to the under-bonnet battery, with no big fat diode or relay in the line?

Ron.
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 09:33:29
Are you SURE that there is a direct link to the under-bonnet battery, with no big fat diode or relay in the line?

Ron.

Yes :y
Title: Re: Merc 2 battery question.
Post by: TD on 16 July 2017, 09:36:15
The 'charging points' I think are for jump starting .... if you have a look I believe they will have gert big cables to them  :)

I would have thought the 'charging points' are connected to the battery connected to the starter only.
The other battery being a separate circuit for running electrics and gets charged from the alternator only....

According to the manual they are charging/jump starting terminals.

The + goes straight to the + on the battery under the bonnet and the - goes straight to ground on the body.

So, be fine to use for charging then  :y

My other point about the other battery being on a separate circuit still stands, having them connected in parallel all the time makes no sense to me...apart from looking at a wiring diagram I guess the other way to prove its separate, is to disconnect the + from the one in the boot and see if the lead still has 12v on it....

Disconnecting batteries on a Merc can lead to all sorts of problems, so I'm lead to believe :(

Maybe  :-\

Tho if you use the merc fairly regularly on decent runs and its not parked up for a week or two at a time, if it were myself, I don't think id bother to charge the battery  :-\
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 09:40:40
Right I think I have answerd my own question.

The battery in the boot is a small 12v.

The battery  under the bonnet is a big starter battery.

Both batteries read different voltages.

If they were linked in any way, they would read the same voltage :y
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 09:49:14
Is the boot battery voltage lower by about 0.7 volts than the larger battery?

Ron.
Title: Re: Merc 2 battery question.
Post by: TheBoy on 16 July 2017, 11:22:56
Ahh, the joys of start-stop wank ;D
Title: Re: Merc 2 battery question.
Post by: TheBoy on 16 July 2017, 11:25:12
Not sure if the Merc is the same, but on the Shaguar, you have to be careful where you connect the charger due to the battery monitor "ecu" on it.  Plugging the charger directly on the battery terminals confuddles the hell out of it, then it does all sorts of weird shit, like not charging the battery when the car is running.

Don't ask how I know this ::)
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 11:30:05
Also, TB, if you use a conditioning/maintaining charger - the Halfords "smart" charger, for example, you can potentially (no pun intended!) confuse the ECU because it pulse-charges, and they don't like it up 'em!  :(

Ron.
Title: Re: Merc 2 battery question.
Post by: STEMO on 16 July 2017, 11:31:05
I just don't get any of this. I've had my astra for over two years now, never felt the need to go near the battery, it just does everything it needs to do by itself. If it went flat for any reason, then I'd know it was kaput and fit a new one.
Why the need to charge the battery on your cars?
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 11:46:45
The need arises when you leave it unused for a week or two, due to the quiescent drain taken by all of the splendid systems incorporated into these modern Omegas.  :-X

Ron.
Title: Re: Merc 2 battery question.
Post by: Sir Tigger KC on 16 July 2017, 11:48:37
I just don't get any of this. I've had my astra for over two years now, never felt the need to go near the battery, it just does everything it needs to do by itself. If it went flat for any reason, then I'd know it was kaput and fit a new one.
Why the need to charge the battery on your cars?

+1  :y

I think there's huge potential there for damaging your electrical system unless you completely disconnect both batteries and charge them directly!  ::)  :-\

If it ain't broke.....  ;)
Title: Re: Merc 2 battery question.
Post by: STEMO on 16 July 2017, 11:59:34
The need arises when you leave it unused for a week or two, due to the quiescent drain taken by all of the splendid systems incorporated into these modern Omegas.  :-X

Ron.
But we're not talking about omegas, we're talking about mercs and jags.
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 12:05:28
Sorry, I had an Omega mind-set there! Maybe the same applies?

Ron.
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 12:17:13
No, providing you have the correct charger, you can charge the Merc in situ, using the charging point terminals.

You must not charge the battery by connecting the charger directly to the battery terminals.

The key must not be in the ignition when you charge, else you will fubar the alternator.
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 12:18:29
Is the boot battery voltage lower by about 0.7 volts than the larger battery?

Ron.

No, its slightly higher.
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 12:21:02
Ok, that' MY theory shot down!  :(

Ron.
Title: Re: Merc 2 battery question.
Post by: Viral_Jim on 16 July 2017, 12:30:27
I just don't get any of this. I've had my astra for over two years now, never felt the need to go near the battery, it just does everything it needs to do by itself. If it went flat for any reason, then I'd know it was kaput and fit a new one.
Why the need to charge the battery on your cars?

Got to agree with Stemo, in my previous job I worked away 3weeks at a stretch 10months of the year. My cars were in Birmingham Airport carpark in the elements for all that time and never had an issue with charge. That was a mondeo, x-type, omega and the yeti.

Coming back on a Friday night I've never seen an AA van in the carpark. If battery drain was an issue, surely they'd be jump starting them in their droves?  ;D
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 12:41:42
I just don't get any of this. I've had my astra for over two years now, never felt the need to go near the battery, it just does everything it needs to do by itself. If it went flat for any reason, then I'd know it was kaput and fit a new one.
Why the need to charge the battery on your cars?

Got to agree with Stemo, in my previous job I worked away 3weeks at a stretch 10months of the year. My cars were in Birmingham Airport carpark in the elements for all that time and never had an issue with charge. That was a mondeo, x-type, omega and the yeti.

Coming back on a Friday night I've never seen an AA van in the carpark. If battery drain was an issue, surely they'd be jump starting them in their droves?  ;D

Its not a question of it going flat, it's a matter of keeping it in tip top condition, the wifes Astra, for example, the battery is 10 years old and still going strong because I keep it conditioned.
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 12:46:41
I agree totally. If I haven't used my Omega for a couple of days, I trickle-charge the battery to keep it topped up, because if allowed to discharge significantly and then charge it, it counts as deep-cycling and they are not constructed to cope with that; it sheds active material from the plates, to fall to the base of the battery and likely to short it out internally - or at best, to reduce its capacity.

Ron.
Title: Re: Merc 2 battery question.
Post by: Andy B on 16 July 2017, 13:38:30
I need the jump start connections under the bonnet as you can't see my battery without removing the driver's seat  ???
Title: Re: Merc 2 battery question.
Post by: Doctor Gollum on 16 July 2017, 14:26:18
Jump starting via the boot battery will fry things.
Title: Re: Merc 2 battery question.
Post by: Lincs Robert on 16 July 2017, 15:24:50
I recall that some exotic/expensive stuff has two batteries. One at 12volts to start the engine and another at 42 volts for the other electrics. They also have twin output alternators.

I think it's only 7 series, A8's and the like - but certainly something to be wary of!
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 16:05:36
Jump starting via the boot battery will fry things.

Not a lot of people no that ::)
Title: Re: Merc 2 battery question.
Post by: STEMO on 16 July 2017, 16:24:14
Well....if I get five years out of a battery....then have to fork out c.£80 for a new one..that's ok with me. Beats the f**k out of farting around with chargers and stuff  ;D
I suppose people who hang on to their cars for ten years or more will have this mindset, but as I've never held on to one for more than four years, it's someone else's problem.
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 16 July 2017, 16:39:37
Well....if I get five years out of a battery....then have to fork out c.£80 for a new one..that's ok with me. Beats the f**k out of farting around with chargers and stuff  ;D
I suppose people who hang on to their cars for ten years or more will have this mindset, but as I've never held on to one for more than four years, it's someone else's problem.

I wish I was wealthy :'(
Title: Re: Merc 2 battery question.
Post by: STEMO on 16 July 2017, 17:26:12
Well....if I get five years out of a battery....then have to fork out c.£80 for a new one..that's ok with me. Beats the f**k out of farting around with chargers and stuff  ;D
I suppose people who hang on to their cars for ten years or more will have this mindset, but as I've never held on to one for more than four years, it's someone else's problem.

I wish I was wealthy :'(
Wealthy enough to buy a merc, I only own a frugal 1.4 astra.  :(
Title: Re: Merc 2 battery question.
Post by: TD on 16 July 2017, 17:43:41
Well....if I get five years out of a battery....then have to fork out c.£80 for a new one..that's ok with me. Beats the f**k out of farting around with chargers and stuff  ;D
I suppose people who hang on to their cars for ten years or more will have this mindset, but as I've never held on to one for more than four years, it's someone else's problem.

I wish I was wealthy :'(
Wealthy enough to buy a merc, I only own a frugal 1.4 astra.  :(

And if you'd looked after your battery....you could be running about in a merc too with the savings  :D :)
Title: Re: Merc 2 battery question.
Post by: Viral_Jim on 16 July 2017, 17:59:44
Its not a question of it going flat, it's a matter of keeping it in tip top condition, the wifes Astra, for example, the battery is 10 years old and still going strong because I keep it conditioned.

Ah I see, Fair enough, each to their own.  :y

For me, for a saving of £18-20 per year I couldn't be ar$ed with the effort. Then again, I am a member of the "throw away generation" so that's to be expected  ;D
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 18:13:41
And you are not on a non-elastic pension, Jimmy!  :(

Ron.
Title: Re: Merc 2 battery question.
Post by: TheBoy on 16 July 2017, 18:19:01
Also, TB, if you use a conditioning/maintaining charger - the Halfords "smart" charger, for example, you can potentially (no pun intended!) confuse the ECU because it pulse-charges, and they don't like it up 'em!  :(

Ron.
Some chargers are designed to be used whilst still connected to the car. Most smartchargers fall into this category, but check instructions.
Title: Re: Merc 2 battery question.
Post by: TheBoy on 16 July 2017, 18:23:47
I found my Omegas are good for about 3.5-4 weeks without usage (or charging), much beyond, and you run the risk of not being able to start.

HOWEVER. As with most battery technologies, its completely shags them to leave them in a semi discharged condition for any period.

Hence, I do use a charger when appropriate.
Title: Re: Merc 2 battery question.
Post by: Viral_Jim on 16 July 2017, 18:27:38
And you are not on a non-elastic pension, Jimmy!  :(

Ron.

Very true. I'm on the new scheme where they retire you about 4 days post-mortem  ;D

Anyway, I thought that all you lot retired at 53 on a final salary pension scheme? It's what everyone else my age seems to believe ::)
Title: Re: Merc 2 battery question.
Post by: Bigron on 16 July 2017, 19:25:31
Also, TB, if you use a conditioning/maintaining charger - the Halfords "smart" charger, for example, you can potentially (no pun intended!) confuse the ECU because it pulse-charges, and they don't like it up 'em!  :(

Ron.
Some chargers are designed to be used whilst still connected to the car. Most smartchargers fall into this category, but check instructions.

Yes, TB, I would expect some of the more modern ones are safe to use whilst the battery is still connected, but the Halford ones in particular specifically advise against this practice and as some Oofers may be a little impecunious (like me!) and would have earlier models, I was only doing my Oof duty and offering a caveat.  :y

Ron.
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 17 July 2017, 06:50:19
Also, TB, if you use a conditioning/maintaining charger - the Halfords "smart" charger, for example, you can potentially (no pun intended!) confuse the ECU because it pulse-charges, and they don't like it up 'em!  :(

Ron.
Some chargers are designed to be used whilst still connected to the car. Most smartchargers fall into this category, but check instructions.

Yes, TB, I would expect some of the more modern ones are safe to use whilst the battery is still connected, but the Halford ones in particular specifically advise against this practice and as some Oofers may be a little impecunious (like me!) and would have earlier models, I was only doing my Oof duty and offering a caveat.  :y

Ron.

You get what you pay for.
Title: Re: Merc 2 battery question.
Post by: TheBoy on 17 July 2017, 17:11:13
Also, TB, if you use a conditioning/maintaining charger - the Halfords "smart" charger, for example, you can potentially (no pun intended!) confuse the ECU because it pulse-charges, and they don't like it up 'em!  :(

Ron.
Some chargers are designed to be used whilst still connected to the car. Most smartchargers fall into this category, but check instructions.

Yes, TB, I would expect some of the more modern ones are safe to use whilst the battery is still connected, but the Halford ones in particular specifically advise against this practice and as some Oofers may be a little impecunious (like me!) and would have earlier models, I was only doing my Oof duty and offering a caveat.  :y

Ron.
The Halfords SmartCharge 200 won't harm after you've used it a couple of times....  ....mainly because you've already blown the power transistors in it. A proper PoS from a reliability standpoint.  Generally cheaper to buy from Ring direct (though every bit as unreliable still).  It really is a nasty charger.

The more upmarket Ring ones, as sold at Halfords, specifically state you can charge on the vehicle. This is what I use.
Title: Re: Merc 2 battery question.
Post by: Bigron on 17 July 2017, 17:41:03
Thanks for that, TB. My Halfords one is quite old and is definitly contra-indicated for on-vehicle charging. It's actually in a safe place now, so I cannot easily check the model number!  :-[

Ron.
Title: Re: Merc 2 battery question.
Post by: TheBoy on 17 July 2017, 17:53:30
Thanks for that, TB. My Halfords one is quite old and is definitly contra-indicated for on-vehicle charging. It's actually in a safe place now, so I cannot easily check the model number!  :-[

Ron.
Sure its a Smart Charger, not just an Automatic Charger (that by its nature must have battery removed)?
Title: Re: Merc 2 battery question.
Post by: Bigron on 17 July 2017, 18:12:48
I'm only going by the label; what do I know!  ???

Ron.

P.S. No, I ain't sure.....or am I?

P.P.S. Yesterday I was undeciden: now I'm not so sure!
Title: Re: Merc 2 battery question.
Post by: Auto Addict on 17 July 2017, 20:26:14
Also, TB, if you use a conditioning/maintaining charger - the Halfords "smart" charger, for example, you can potentially (no pun intended!) confuse the ECU because it pulse-charges, and they don't like it up 'em!  :(

Ron.
Some chargers are designed to be used whilst still connected to the car. Most smartchargers fall into this category, but check instructions.

Yes, TB, I would expect some of the more modern ones are safe to use whilst the battery is still connected, but the Halford ones in particular specifically advise against this practice and as some Oofers may be a little impecunious (like me!) and would have earlier models, I was only doing my Oof duty and offering a caveat.  :y

Ron.
The Halfords SmartCharge 200 won't harm after you've used it a couple of times....  ....mainly because you've already blown the power transistors in it. A proper PoS from a reliability standpoint.  Generally cheaper to buy from Ring direct (though every bit as unreliable still).  It really is a nasty charger.

The more upmarket Ring ones, as sold at Halfords, specifically state you can charge on the vehicle. This is what I use.

I use an upmarket Ring, served me well, recovered a couple of neighbours batteries that seemed cream crackered.
Title: Re: Merc 2 battery question.
Post by: Field Marshal Dr. Opti on 18 July 2017, 13:21:31
Well....if I get five years out of a battery....then have to fork out c.£80 for a new one..that's ok with me. Beats the f**k out of farting around with chargers and stuff  ;D
I suppose people who hang on to their cars for ten years or more will have this mindset, but as I've never held on to one for more than four years, it's someone else's problem.

I wish I was wealthy :'(

STMO is as wealthy as an Arab oil sheik. The sort who drive their brand new Range Rover in the desert and leave it there once it runs out of petrol. ::)

The Astra, presented in the most unfortunate shade of green known to man, will soon be history.