https://drive.google.com/file/d/0B4azhgT5UI-QUHhWZlFwRDhsd0U/view?usp=sharing
Now this one I find useful ....... note voltage is 14.2 at tickover after a run.
I have seen 14.3V here but only ever 14.1 in Dubai and sometimes as low as 13.8 in the heat after a run.
No doubt Bolt will be able to explain exactly why but I suspect the battery suffers in the heat (just like we do). Actually, it makes sense. When it's really hot we feel like we have no energy so why should the battery be any different?
But chemical reactions work better when they're hot...
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!
Gilbertd wrote:
No doubt Bolt will be able to explain exactly why but I suspect the battery suffers in the heat (just like we do). Actually, it makes sense. When it's really hot we feel like we have no energy so why should the battery be any different?
Truer words were never spoken!
Thanks. A very nice and concise explanation.
I knew batteries suffered out here, but not why.
Don't know about other places but here we have a battery retail chain called Motolite and if you get stuck, they will be with you in around 20 minutes, fit the new one and cart your old one away for you. No need to be stuck. One of the few things that actually works as advertised!
My last one is from them and two years later it's still going strong, so reasonable quality as well.
Wow, What a great service!
Not quite as hot here as PI but we have Interstate Battery, and if one of theirs fail, they will Instantly tell you it was obviously your fault and to sod off!
No help- Nowhere- Never!
It is evident that battery failure is much more common there since they have such a great system for getting you back on the road! (Except Mondays?)
Bolt wrote:
Wow, What a great service!
Not quite as hot here as PI but we have Interstate Battery, and if one of theirs fail, they will Instantly tell you it was obviously your fault and to sod off!
No help- Nowhere- Never!
It is evident that battery failure is much more common there since they have such a great system for getting you back on the road! (Except Mondays?)
Now that's how I would have expected it to work here, but no. They are a great bunch. Really helpful and quick. Most unusual.
Yes, except Mondays for me, unless it's a public holiday (of which we have many, many)!