Definitive Battery Charging/Disconnecting for R230

[Davgral]

Hi Everyone, I'm just about (24 hours away) from buying a 2008 R230 and for the last two days I've been googling to try to find out exactly what I can and can't do with the batteries and there doesn't seem to be consensus. The issue is that I don't have a garage and the car will sometimes sit for weeks without being started. (Bad news I know). So if any one can help a newbie please:

- Does charging the rear battery also charge the front battery? Some people say you never need to charge the front battery, as it only starts the car, but others say it provides power to the convenience electrics if the rear battery gets low.
- Can I disconnect both batteries' earth cables with the result that I will have to reset windows when I reconnect, but that's all. I understand that spikes on reconnect might blow something.
- Does anyone have experience of connecting a solar panel to the rear battery? I do this on my C280 and S500 and it seems to offset the 1%/day charge loss of lead-acid batteries.
- I've got a CTEK charger so the plan would be to charge the battery(ies) fully before leaving the car. I'm hoping that at 30mA/day usage I'll get at least 30 days grace before the car alarm goes off. If this doesn't work I'm planning to use a second lead-acid full size battery in parallel with the installed battery to double the period I can leave the car without charging.

For interest my 1987 C280 reacts to being left for weeks with no problems at all. I just reconnect the earth and off we go. The 1992 S500 is more temperamental. On reconnecting the battery the pneumatic pump for the door locks clicks a few times and then expires. I'm wondering if the R230 will be equally temperamental.

All the best, Dave

 

[DSB SL AMG]

Hi Dave,

Welcome to the forum!

Best way is to connect CTEK to main battery and trickle charge whilst you are away, OR disconnect negative on main battery and trickle charge a few days before start up. If its only for some weeks at a time I would think you do not need to worry about the second GEL battery up front which I understand is backup for consumer electronics, although I am sure others will have a view...if your battery is good I would envisage you could leave for 2-4 weeks without doing anything (unless you had a drain), but for long life always wise to keep it conditioned were possible

If you are about to pick up your R230 I am sure you have already researched but please do check the boot for water ingress as they leak through the boot / c-post seals by design, there is a DIY fix for this so may have been done already and dry, if the boot gets wet it will play havoc with the electrics and PSE pump...and if its a 500 with ABC suspension, make sure you have the struts checked before purchase as they are very expensive to replace (MB £1300 per corner).

 

[renault12ts]

I know someone with an R230 in storage which can sit for months without being on a Ctek...and it never fails to start.

But a CTEK is a good idea.

 

[brucemillar]

Regards the Solar chargers?

I have a friend (yes it's true) who uses one in his old Land Rover with mixed results. In general it is fairly good during the summer months. Not to be relied upon in the winter months.

I use a RING maintenance charger. It fits under the bonnet so can be kept away from the elements. I just the drop the mains cable out via the headlight shut line. But I do have the car garaged. In the outdoors you still have the challenge of keeping any connection dry. I have seen some clever bodging with Tupperware boxes. This included a guy who mounted his Mobile Data Dongle on the outside of his house by drilling holes in a tupperware box, dropping in the dongle then sealing the cable holes with scilicone, before fixing it to the eaves on his house.

In fact you may be able to get some "Speedfit" electrical junction boxes that are ready made for this kind of application.

 

[Davgral]

Hi David, ts and Bruce, Thanks for your tips. I guess I'm worrying about two things in particular: The consumer battery in the rear falling to a low voltage and setting off the alarm at 3am - all my 3 mercs have done this and I've had the alarms disconnected on all of them. I think the only way to be sure this won't happen is to disconnect the alarm on the R230 as well. The second thing is having the voltage spike destroy something when I reconnect the battery. BTW I would double up on the Consumer battery not the starter battery. I'm guessing the stored R230 had it's 2 earth leads disconnected, which is a route I may well go down.

Waterproofing the PSE sounds like a good idea from the number of people on the forum who have had trouble with these. I didn't go for the 500 because of the ABC.

Crunch time coming up soon. I've been lucky with cars so far, so the paperwork is going to be examined under a microscope to check the record reflects the 100% seal replacement and new back window which have supposedly been done. I'm also going to fill the boot with those little packets of silica gel that come with everything you buy these days. (Joke)

 

[c63chris]

I have a CTEK charger connected to the rear battery for mine. The logic being if this goes flat I won't be able to open the doors or anything. Worst case open up the car and charge the battery in the front to start the car. The boot seems to close easily over the lead and hopefully won't distort. Alternative was to fix the connector to the floor of the boot and connect that way but didn't fancy making a hole in the car!

 

[Davgral]

Hi Chris, The CTEK lead is not too chunky so I think I'll do the same as you. Slightly disappointed you didn't make a joke about the hole in the boot allowing the water to run out!

I've been reading up on using lead-acid batteries in parallel and there's a lot of discussion about using diodes to restrict any reverse current. However there are also some who say this is overkill, there shouldn't be any reverse current as long as the batteries are of similar condition. I've just ordered some anderson connectors and I'm going to bolt the CTEK connectors and a couple of wires with the Anderson connector at the end, to my installed Consumer battery terminals, so I can quickly get home from vacation, open up the trunk, attach the CTEK and charge both batteries at the same time, (slightly dodgy?) then unclip the extra battery and off we go. I am going to try this in preference to detaching the earth cable, at least at first.

The R230 user manual states that the only way to activate the alarm on the car is to press the "lock" button on the remote key. So I am going to use the following procedure when I leave the car:

- turn off all the lights, comand and heating / cooling functions.
- Press down the passenger door button
- lock the driver's door manually with the flat key
- lock the trunk manually

I'm hoping by doing this to get well below the 30mA current draw as the alarm will be deactivated. Anyone have experience of the current draw in these circumstances?

Dave

 

[Davgral]

Front starter Battery

Regards the Solar chargers?

I have a friend (yes it's true) who uses one in his old Land Rover with mixed results. In general it is fairly good during the summer months. Not to be relied upon in the winter months.

I use a RING maintenance charger. It fits under the bonnet so can be kept away from the elements. I just the drop the mains cable out via the headlight shut line. But I do have the car garaged. In the outdoors you still have the challenge of keeping any connection dry. I have seen some clever bodging with Tupperware boxes. This included a guy who mounted his Mobile Data Dongle on the outside of his house by drilling holes in a tupperware box, dropping in the dongle then sealing the cable holes with scilicone, before fixing it to the eaves on his house.

In fact you may be able to get some "Speedfit" electrical junction boxes that are ready made for this kind of application.

Hi Bruce, can I infer from your positioning of the Ring charger under the hood mean that you are charging only the starter battery? Or does charging the starter battery also charge the convenience battery? Most people seem to suffer from the Convenience battery going flat, so this is really pertinent to my problem. Kind regards Dave.

 

[190]

Using a solar charger seems an attractive way to keep the battery charged but the one I tried was hopeless. It only produced the rated output in full sunshine and the rest of the time did almost nothing. This was some years ago so they might have improved. I recall there are different types of solar panel, and one of them has a performance that doesn't drop off so dramatically in less than full sun.

 

[DSB SL AMG]

Hi Dave,

As far as I am aware fitting of a new R230 rear seal does not fix the boot 'MB pond', root cause is design issue, it needs the DIY fix which I think is easily done...there is a great write up on this on the other side as already stated best to inspect boot area for signs of water ingress...

to check the record reflects the 100% seal replacement and new back window which have supposedly been done. I'm also going to fill the boot with those little packets of silica gel that come with everything you buy these days. (Joke)

 

[Davgral]

Thanks David. It rained last night and no damp bits so far but I'll check the DIY fix and apply it, Thank you. I think I'll also put a tupperware box upended over the electronics on the left side of the trunk. They do look very exposed to any drips.

I picked up the SL350 last night and drove it for 4 hours to get back home. I absolutely love it. Should have gotten one of these years ago. Compared to the S500 it's noisier, the ride is a lot harsher and the steering is sharper - all as you'd expect. If I buy another one I'll get the 500 with air suspension. I think the risk of a strut or four needing replacement is worth the difference in ride quality. Had the roof down today and it's magical.

I did also get some factual data from a mechanic who checked. The front and rear batteries are completely isolated from each other. I guess there is one alternator that charges both, but the front conventional battery only starts the car and after that there is no current drain at all. The front battery doesn't pick up any deficiency in the rear AGM Consumer battery. Similarly a dead front battery and a full rear battery will still not start the car. This explains Renault12ts's friend's R230 which always starts. Not starting the car is equivalent to disconnecting the earth cable to the front battery.

The mechanic said that with good batteries and no non-standard current drain, locking the car with the manual key should still allow the car to be started after 2-3 months. We shall see.

Good news for me is that although the advertisement didn't mention it, the car came with CD multi-changer and Bluetooth connectivity for the phone. One happy bunny so far!

 

[Rosso1]

Have you guys thought of using the Sunforce (i think alot of people use this brand in the States I have their sucurity lights at home and they work very well) trickle charger it should cover enough of your lost battery drain. It could just rest on your dash while charging? Sunforce Products 58012 Solar 12-Volt Battery Maintainer, 2-Watt | eBay

 

[Davgral]

Have you guys thought of using the Sunforce (i think alot of people use this brand in the States I have their sucurity lights at home and they work very well) trickle charger it should cover enough of your lost battery drain. It could just rest on your dash while charging? Sunforce Products 58012 Solar 12-Volt Battery Maintainer, 2-Watt | eBay

Hi Rosso, I've got a Ring 2.4W and a Ring 6W with both mounted in the rear window of the C280 and S500 respectively. The C280 battery seems to cope with that just fine and stays charged, but although the S500 solar panel is more than twice as powerful it can't make up for the deterioration in an old battery and that's been in this last month's sunny weather. I spoke to a man at Exide today and the 1% deterioration per day that I've quoted, is a number made up by someone in my past. The Exide man says the real deterioration/day is a complex matter with a large number of parameters, including temperature, age, number of times the battery has been deep cycled, etc. etc. Could be 1%, could be anything.

Waiting for this weekend so I can examine the car after a significant downpour, to see if the garage's promise on the C pillar seal's integrity holds true.