gordonjcp wrote:

But chemical reactions work better when they're hot...

That is basically a true statement, however in the case of a Flooded Lead acid battery (Sealed AGM and Gel as well) this is not a good thing.
There is a thing called thermal runaway that will occur in a battery that is under charge, and very hot. It causes the acid to boil and in extreme cases, the battery can explode or catch fire. I have seen both happen personally......Not pretty, and MAN, the smell!
Another fun fact about Lead acid batteries, is that they will have their lives halved for every 10 deg C above 25 deg C operating temperature.
Bearing this in mind, the first thing I did was remove the cover from the battery to get it more air circulation.
For Roger and the other folks that live where it get's cold enough to make the Brass Monkey nervous, the cover, as well as extra insulation around the battery is a good idea. I have even seen heating mats for under the battery that get plugged into mains at night.

Getting to the charge voltage thing:
For virtually all types of Lead Acid battery the "Gassing Point" is 14.2 volts @ 25 deg C (77 deg F) Getting the voltage above this will accelerate water loss as the H2O in the fluid undergoes electrolysis into it's component parts: Hydrogen and Oxygen.
This is technically not the thermal boiling you get from a runaway, but will cause more than desired water use.

I still want to dissect an alternator regulator for one of these things as I suspect there could be some type of temp comp or 2 stage charging going on here.
The proper recharge curve for a starting battery (Many thin plates for quick high energy) would be to charge to 14.2 - 14.4 for a brief time, like 5 min, and then drop to an "Absorb" voltage of 13.8. This will fully recharge a 12 volt battery without undue gassing. An alternator that holds the voltage above 14.2 constantly will cook the battery more quickly.
As the temperature of the battery rises, you need to lower the voltage as the gassing point drops as temp. increases, so Spiggy seeing 13.8 in Dubai would be consistent with a well designed alternator / regulator.
On the other hand, you need to increase the charge voltage a bit as it get's colder as the Gassing point rises the colder it gets.
Since it seems to be winter for most of you, what are you seeing on a nice brisk 10 deg (-10?) Morning as far as voltage goes?

Of course, the other explanation for the voltage ramping down with heat is that as you get an electromagnet (Alternators have 2) hot, they lose efficiency and the fields become weaker. A happy coincidence for our poor overheated batteries!

Aloha,
After spending the last 4+ months in New Zealand, where I drove A clapped out Camry, A totally soulless Bluebird, A miserable Kia, and a super cheepo Honda somethingorother, I am home here in Hawaii for a week. Here, I have a really small Chevy Shitbox of a hatchback Hire car.
For various reasons, I have been through 3 of these Chevy's in 2 days! (The blue one was the worst, only went 2 miles before shitting itself)
Being on an extended trip on the old lifeboat, I closed up shop here, sold the wife's 00 and de registered and stored the 02.
Kept a battery maintainer on it and she fired up instantly, and rose back up to ride height! Magic!

I was invited to to neighbor's house for BBQ and as it is not currently road legal, I "Had" to take the 8 mile back way up the mountain (Mauna Kea) to get there.
Fortunately it is an old sugar cane haul road, and has not been repaired for over 20 years, so it is in really bad shape (Yes!!)
For a quick jaunt up the hill, it was just plain fun with 2 river crossings.

Getting to the point.......RANGE ROVERS ROCK!!!! ('specially P-38's)
It is soooooo nice to drive a real fully capable truck that feels and handles like a velvet tank.
I had almost forgotten this due to the load of tin can trash I have been borrowing, or hiring lately.

I know that you all know this, but I am still having an Adrenalin rush from a very fast descent. Too much fun!
Oh, the Home kill Beef and Beer was epic as well! :)
Cheers,
Tom

Well, I may be an American, but probably not a very good one..........Migrated to Hawaii 26 Years ago!
Mainland USA is a great place to be FROM...........
Of course, now I have even given that up for a more nomadic existence......
So, nope, to ego-centrism here!
Now, there is a very angry ex pat Brit in Wa state who does seem a wee bit peeved at all of the Z Plate registration folks out there........

Aloha George,
Pull up a comfy chair!
Like you, I have been keeping my fleet (Now just my 02) going totally solo in Hawaii as there is no dealer on the Big Island, (and driving to Honolulu get's the rugs wet every time!)
Gotta ask though.....Is it really less expensive or easier to get parts from UK as opposed to sourcing them somewhere stateside?

Welcome back from the "Dark side" and into the light!
Jeeps are pretty good. Decent motors and running gear, but everything else is made of snot and tissue paper. Not surprising then, that a truck that has been built down to a price point just does not have the same "residual quality" as one that you paid through the nose for to get it off the lot!
P-38's were well designed, and well built using (Mostly) the best stuff available. Other than the odd electrical gremlins (C'mon! They are British after all) The feel you get from driving a 15 year old RR versus an equivalent Jeep is just not even close!
And, as a bonus, if (when?) the P-38 does strand you you will be much more comfortable and of course you will look better sitting there!

Aloha, and Kia Ora!
Thanks for the invite Gilbert.
Nice place ya got here....Very roomy.....
Got a wee bit irked by tyrannical admin eh?

Glad to be aboard even though I am currently motoring in my "other Car" It is at least still British, being an Waveney Class Ex RNLI Lifeboat.
Sort of the P-38 of the waves, but without as many electrical issues.(Touch wood!)
I do have the Nanocom on board, in case I find something interesting when I get to Oz in a few months.
Ya never know.....The 85 Classic Outback basher is still very much loved and I am not eager to replace it, but I have been spoiled by the P-38s
Cheers,
Tom aka Bolt