dual battery question...
I have a question.... My 290 GTD has one big 100ah battery.
I would like to fit an aux battery to power my fridge and some other stuff like radio and 220v converter.
I see that some people put 2 optima batteries (a red one and a yellow one) in the tray where the original battery is now. This would be a very clean and simple solution....
...but the optima starter batt is only 50 Ah??? Is this enough to start my 290 TD engine???
If it is...why does mercedes fit a huge 100ah battery?
thanks,
Geoffrey
Hi
if you fit two 12v batteries in parallel you double the amperage and maintain the 12volts that the system is built.to use ....take the maximum size of the tray and choose two batteries that will fit in by height width and length plus maximum capacity ** example--- 2 x 100amp will give you 200amps availability at 12volts.... you need to consider the strain this may put on the existing alternator and the manufacture of brackets and retainers required to hold the batteries in place in event of and accident......
Hello Geoffrey,
If you connect two Optima 50Ah batteries in parallel you will end up with a setup identical to the one you have now (12V, 100Ah).
You could consider installing a 12V, 125Ah, 1200 CCA (Cold Cranking Amps), Heavy Duty, Commercial Battery.
These batteries were originally fitted to the diesel 460 series by Mercedes-Benz.
You can obtain such a battery from an MB dealer citing part number A001 541 82 01 (List price in Germany is 435.11 Euros + VAT).
This battery is 286mm x 269mm x 230mm in size and will fit into the standard battery tray.
Alternatively you can look for Varta 625 023 000 or 625 23 which is the OEM version of the same battery. You can get it from www.tayna.co.uk for about 220 pounds + VAT.
A second alternative is to search for any battery conforming to the 6TN standard dimension (which is a military standard if I can recall) to which both batteries above adhere to.
You will need some additional brackets and clamps to secure the battery in place - you can also get them from an MB dealer for not much.
Then, there is another solution: use two 12V, 70Ah batteries connected in parallel. These batteries were utilised in the 24V versions of the 461 series, but they were connected in series, so as to provide the necessary 24V. They too will fit in the battery tray but not without some modifications and some additional hardware. You can order them at any MB dealer using part number A 002 541 79 01 26 (List price in Germany is 197.76 Euros + VAT). This solution will give you 140Ah.
I prefer clean solutions myself - I would go fot the single large battery. I have looked into this matter due to the fact that I am considering to change the 74Ah battery on my 1991 300GE with the 125Ah unit.
Please feel free to PM me if you need any further assistance (e.g. part numbers).
Remember Ah is an indication of the battery's capacity whilst CCA is an indication of how much power the battery can deliver at once.
For example a 50Ah battery can theoretically provide you with a steady current of 1A for 50 hours whilst a 100Ah battery can provide 1A for 100 hours or 2A for 50 hours etc.
A 1200 CCA battery can give you a current of upto 1200 amperes (even when cold) without exploding(!), but of course for a very short period of time.
Regards
Michael
Hi G,
I don't think the Optima will be big enough for your diesel: as an example I have an old 98-built 300 TD estate. It was -3 degrees this morning and the damned thing wouldn't start (I changed the battery with a small spare when the original one gave up the ghost about half a year ago). The battery was too small. I had to double it up to get the thing to start. I would have thought the 290TD isn't that dissimilar to the 300TD engine as they come from the same era. I would stick with your big starter battery and not sacrifice doubt.
The battery trays on the Gs are, in my opinion, just too small to fit two good-sized batteries: I always try to fit the punchiest batteries available for the space required. I know its a bind, but my solution to the dual battery set-up was to hard wire a portable battery box into the rear of my G: this is my aux battery. It was the only way that I could find a way of fitting two Odyssey 1500s: I've had very bad experiences with the Optimas (especially when they've discharged a lot - if they are very low, they will cook on recharging and you have to throw them out - its an older technolody. The more modern dry cell or gel batteries can charge a lot quicker and don't cook!).
This battery box set-up, by the way, has proven to be a bit of a revelation for me. I didn't like the idea at first, but having lived with it for two years now, I'm a massive fan of the set-up. It does take up some stowage space in the back, but not enough to impede me from putting everything else I normally have in the car. On a practical side, if I'm at home, I just take it out and put it on the trickle charger for storage or use the battery box for other little chores (i.e. using it to power our little 12V rotary motor on our spit roast!).
Good luck/ph
I've been looking into alternative power options for our camper (transit diesel). It currently has two 70Ah batts wired in parrallel and I was advised not to mess with this set-up for cold start reasons and so far it's been fine.
They will power the lights, radio, laptop etc quite happily and still start the van in the morning. However, there's no way I'd run the fridge off of them while stationary. A 12v fridge will probably output something like 110w (110/12 = 9.2amps) so it won't take long to run your batteries down (c. 11 hours to run a fully charged 100Ah battery to nothing) so they're incapable of starting a big diesel lump.
My advice: Buy a 2 or 3 way fridge that will run off of gas or 12v electric. Connect it to your regular battery to cool whilst driving (via fuse, switch and relay) and then switch to gas when stationary. A 2.75kg butane bottle won't take up much more room than an extra battery.
Those are very tidy jobs! Nice work whoever did them. I understand your question and also wanted to do the same, but then I've got a 463 and it wasn't possible to fit two - even small - batteries in the engine bay. If your 461 is basically the same as those 460s in the pics you could do the following: instead of using a split battery system (like NL, Piranah or I think even the IBS one - which will only allow you to link the batteries up to 100 Amps, i.e. not enough to start a big cold diesel) why don't you use a marine-spec 350Amp VSR (voltage sensitive relay) instead. That way you could have your batteries connected in parallel under the bonnet and they are still isolated from each other when your aux discharges. The advantage with the marine VSRs is that you can manually link the batteries (i.e. via a big switch on the VSR) if you need more amps to cold start your diesel - in the case of the one I mentioned, 350 Amps should be enough to start your car. I've installed this system on my Pinz and the only problem is that the VSR itself is quite big: in the case of the G, you'd probably have it mounted under your seat (where the fire extinguisher is) so that you don't have to open the bonnet to link the batteries. This system works really well and it is beautifully basic in its concept: once the voltage on the main battery goes above 13.2V the charge is let through to the aux battery and it cuts out at about 12.8V. It is super reliable and waterproof as well. If you did this, you could get away with the two smaller batteries you mentioned under your bonnet.
By the way, the Odesseys will not discharge fully as they have some sort of cut out mechanism, so that you will always have a minimum reserve capability left in them (I can't remember the exact numbers, but again if you manually linked two 1500s on minimum charge, you should still be able to get away with starting your car). Be aware that the Optimas don't have this and when they discharge fully, that's it........and they will also not recharge from an alternator (unlike the more modern gel/dry cell batteries).
Would be interested if you could tell us what you did eventually and whether you think (afterwards of course....unfortunately) it was the right set-up.
ph
Thx PH. I think I'm going to build a setup with two oddeseys.
G
The big square varte battery is the best at £140 plus vat it's about 12' x12"
the euro (6tn)battery is the next best thing 12"x12" but about a inch higher but fits a 460 ok with out any mods
the last one i bought was £65 at the war and peace show about 7 years a go.
the 6tn battery is half of most tank battery ie 24volts
so find a tank spares shop or someone from the army and fit a spare battery under the rear seat.
The 12" SQ battery 6tn will only fit a rhd G, lhd has a different shaped tray
I saw this set-up recently in a RHD W461 Wolf 290 Turbo. It has the military 24V electrical system. The owner has fitted 3x 12V batteries in the battery tray. Two are connected in series for 24V, the third is for his 12V radio and some other gadgets. Very neat. Looks to me like the 6TN size battery tray.
They are military/aircraft batteries called Hawker SBS.
http://www.enersysreservepower.com/documents/PS-SBS-CL-IS-UN-v2.pdf
http://www.enersys.com/defense/documents/MSDS-2Jan00.pdf
Eddie.
UK supplier details and data sheet including dimensions:
http://www.dmstech.co.uk/pdfs/battery_sbs_01.pdf
3x SBS40 fit in the square tray.
I am going to try this setup myself.
Eddie.
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thanks for all the swift replies....
The thing is that I would like to fit everything under the bonnet....and that would mean smaller (in size) batteries.
The 460 and 461 batterie trays apparently take two oddesey or optima batteries.
That would be a neat solution! If the batteries are up to the task of starting my G....