My local Interstate battery distributor has regular and AGM Batteries for my 2003 XK8. Both are vented.
That being said, the existing battery does not seem to have a vent nor do I see a vent tube anywhere.

Should it be vented?

 

Yes, and get the AGM.
Should be a small vacuum tube with a right angle plug in connection hanging around the back fire wall at the bottom. Near the high fuse connecter. Goes to the outside.

 

Why do you prefer the AGM? THis is probably like asking which tire someone likes but I have to ask.
Thanks

 

Greg, like you, I have a few cars and they tend to set around. I have no trouble with the AGM's on a tender for long periods of time. I do move one around a bit but the XK8 stays on the tender most of the time and the battery gives little to no fumes in the trunk where the standard ones did.
The cost does make it second out in some cases.
Did you find the vent tube?

 

I have yet to find that vent. Do you use a special tender for AGM batteries?

 

my NAPA branded AGM battery has no visible vent. It’s my understanding that the battery is normally to be considered “sealed” unless an overcharging situation is ongoing. In which case it WILL vent . I have not bothered to dissect my battery to see how that actually works. So far the battery is about 5 years old and is connected to a tender whenever the car is sitting overnight or longer.

For the first year of ownership I didn’t bother with the tender and the car had one electrical gremlin after another. And this is with a battery and charging system that tested 100% normal.


After using the tender, no more failsafe engine warnings, etc.

The tender I used for 3 + years did not have an AGM setting. It worked fine. Last Christmas Amazon had a sale on the NOCO Genius tenders and I couldn’t resist putting my
old tender out to pasture. The new tender, a NOCO Genius 5, does have an AGM setting, which I do use.

Z

 

Thanks for that info.

 

If you hurry, Amazon has a Cyber Monday deal on the NOCO Genius 2 for about $35. I use them on all of my occasional drivers.

 

Just went there and ordered. Thanks

 

Old Battery.
Plates stop about 5/8 inch from the bottom to make a sediment space for bits that are blown off the plates by bubbles created when charging ..Electrolyte just above the top of the plates . Between the plates is anything from wood to glass fibre not over well packed .Usually charged to 15.5v by a Dynamo to 100%
Modern battery.
Plates go right to the bottom .Plates tightly wrapped in fibre glass . Extra volume created is used for electrolyte over the plates . Vented ,No top up ( unless you drill it) Usually charged to 14.4v unless you have a computer controlled alternator which drops is back after a short time at 14.4v. Does not gas due to low voltage . 80% of the capacity achieved but no maintenance. No antimony used Calcium or silver to stiffen the plates. often has magic eye ..Green 50% + charged Black below 50% Clear low electrolyte ..may blow up if charged Scrap.( This is when you drill it and top up with distilled water for another 3 years use )
AMG
As above but sealed and all electrolyte absorbed into the fibre glass Seperators no free electrolyte. Pressure valve in case of over charging. 80%
Spiral wound.
Recognized by the none square case . plates wound in a spiral giving great vibration protection. Sealed. Good for off road and aero planes. expensive. 80%
Cranking Amps.
The big con ...Two standards ... Automobile at 0 F -18degc and Marine tested at 32 f or 0 deg C.
Its the current that will discharge the battery to 6v in 3 min. The marine batteries look better but arnt.
Some brands in UK sold for cars but are marine.
Leisure batteries ...excuse to charge more $$ for a standard battery.
Storage ..fully charge ,wrap in cling film and put in the freezer. Thats what happens to plant in the Alaskan winter.

 

When you you say regular battery, do you mean a 6 cap, fill it with acid type? That's pretty old fashion for a pretty high tech car. Absorbed Gas Mat is the way to go as it is usually a sealed, more juice, no slosh affair. The gel things like an Optima battery are pretty expensive and not necessary for our application. I don't plan on off-roading in my 8. With our cars so sensitive to low voltage I would stick with AGM. my .02 after you had all the info you needed already TM

 

Well everyone who has read what I said is informed ..
Personally I think AMG is unnecessary overkill and extra expense. An egg is an egg and a battery is a battery ie a lump of lead. The bigger lump you can get for your money the better.

 

AMG is unnecessary, you will get there with an ordinary Mercedes.......
But AGM is way better than an old school lead and acid battery. Most Battery vendors claim 2-3 times the life.
My Optima Red Top AGM I bought new in 2002 started my Daily Driver every time until 2019! And Norway is not the easiest place for a battery

 

Optima red top is a spiral wound battery and very expensive. Ie it takes it longer to fall apart .

 

I’ve always gotten longer life from the AGM batteries. Current one (NAPA branded) is only 5 years old, so I expect it will last 4 or 5 more years. The no-brand AMG in our other car is over 10 years one and still working fine.

Am averaging 10+ years from the non-Optima AGM’s and a little better than that on my last Optima. Never got that life with a traditional battery.

Not an engineer, so I can’t speak to why the AGM’s last longer, but there does seem to be some technological advances or breakthrough.

Z

PS And then there were the Lucas batteries that I had to replace by the dozen on the old Triumphs I sold and serviced. They were the worst ever. The Yuasa replacements lasted at least twice or three times as long.

 

HA HA. I was going to make the same comment about an AMG. Obviously a typo but funny one.

 

In the AGM the seperators are made like envelopes with the bottom fastened in resin.All tightly packed so no space for bits to fall off . Add to that no Antimony which poisoned batteries by leaving one plate grid weak.This was replaced in the 70s with Calcium and more recently silver to stiffen the plate grids. No vent but a pressure valve so in normal use no venting at all so no loss of electrolyte. So overall a physically stronger set up but not as strong as a spiral wound. Hence the longer life.

 

Anyone who would even consider putting a flooded battery in an enclosed space has never seen a hydrogen gas explosion. AGM batteries are sealed for a reason and the only battery type suited for the trunk of a car.

 

Yes usually the end blows off ...been there seen that

 

Well, the battery that was in the car for the last 7 years was a vented battery with no vents open and neither connected to the vent tube. The battery now has one plugged and the other connected to the vent tube as designed originally.