Lexus4321

AGM's still vent. They vent water slower than std FLA's. But, over time as the liquid in the AGM disappears, the batt performance goes down too, and at some point the batt won't ever get a full charge from any "smart" charger because batt voltage can't reach back up to full charge voltage. Then soon after that the batt voltage will drop off significantly.

I read some interesting write-ups about history of batts, and whether changing a OEM FLA to AGM is good idea or not.
I believe my GX came with a "sealed" FLA with the view glass like some IntState batts have. That batt lasted I think 6yrs for me.

From reading, AGM's came to market with good performance improvements, but also came with extra cost. Then over the years AGM's quality and performance have gone down, so much so that std FLA's are on-par with AGM's and vice-versa. Diehard Platinum FLA is $10 less than the AGM, and has 12mo more warranty, and, specs are about identical. Most I see these days is AGM marketing fluff, like "lighter" and "spill-proof" and "maintenance free".

As for using AGM where a FLA was used. Some write-ups seem to say that the charging system is designed to charge using a specific batt profile (gel vs fla vs agm), etc. I am sure charging systems back then were not designed to be able to charge everything. But, newer charging systems with use of small simple IC's can adapt to various batt chemistry, so swapping is easier. But it's still not clear to me what vehicle(s) is or is not swap happy.

chiph9

From my understanding, the advantage of an AGM is that there aren't heavy lead plates (the lead is rolled up in the mat) so they're more resistant to vibration and shaking. Which is good for an off-roader.

They used to cost at least 50% more than flooded lead-acid batteries, but I think constant complaints from people about their price caused the manufacturers to cheapen the construction in order to sell more of them.
Usual story...

Chip H.

cssnms

AGM batteries only vent if overcharged. Under normal operation they do not vent. They are VRLA. The H2 and O2 that are produced will recombine inside the battery and no gases escape or are "vented" from the battery.

As mentioned, AGM tend to be more resilient to impact, which is why they are popular on boats as well as their other positive attributes. Quality AGM's also tend to have a higher AH rating and can be discharged lower than a lead acid battery without killing the battery in the process. They tend to be smaller in size by comparison with a comparable lead acid but are as heavy or heavier due to their construction.

Not all AGM's are created equal. Odyssey batteries are made in the US and contain 99% virgin lead. Northstar is another good brand and often sold under other labels.

Lexus4321

AGM's do vent.

AGM's dry out, some more so than others. My project AGM's went fully dry, perhaps ill-made AGM's.

Is the 2006 GX charging system made to charge FLA and AGM battery?

Lexus4321

Some test data.

New coscto batt fresh off my Minn Kota charger measured 12.7v, installed and started engine, voltage measures 14.3v
It sat overnight.
Measured resting batt again, 12.5v, started engine and measured 14.1v and 7.96A into batt.
(engine running tests had my HID and fog lamps on).

Some charts show FLA's as 12.7v@100% charge, and 12.5v@95% charge. So my batt is shedding 5% sitting overnight?

cssnms

Glass mat batteries ONLY vent when overcharged, that is the ONLY time excess gases are produced.

Lexus4321

When is a battery in a GX470 not charging when the engine is running? There is no batt charge controller in GX470 that we can find on some newer vehicles.
If I install AGM that is full at ~12.7v, then as soon as the engine starts the batt begins to overcharge.

So is the AGM battery any good for the GX470?

cssnms

WHAT?!

Maintaining a state of charge within spec and being in a state of over charge are two distinctly different things.

Ill explain this again, the gasses omitted in an AGM recombine internally under a state of normal charge, as-in within spec. In the event the battery is overcharged beyond rated capacity (15v+) due to a faulty cell, bad charger, bad voltage regulator in car or whatever, the risk of gasses building up is high in which case the valve will release when that happens, this is to keep the battery from exploding. Again this is the only time an AGM will vent.


Perhaps Odyssey's characteristic description and definitions will help you to understand - see maintenance, ventilation and definitions. Odyssey also very clearly warns against over charging an AGM (15v+) and how it will not only shorten the life of the battery but that it will cause excessive off gasing and the battery to vent.

Lexus4321

As I mentioned, AGM's will and do dry out, just much slower than std FLA. Why the vendors keep saying AGM's last longer than FLA? That's also a lie. FLA's need regular maintenance, wheras most (read that again, most, not all) AGM's are 100% sealed so you cannot service them.

Nothing is 100%, gases will vent out of all batts.

Serviceable AGM

cssnms

Just stop already...

You do not even understand the difference between what constitutes a state of overcharge vs charging within spec and yet you continue to prattle on arguing about the functional design of an AGM, also something you clearly do not understand.

The only reason an AGM would dry out is from being OVERCHARGED and when it is OVERCHARGED the gases will vent thus the battery will lose water. Not that I expect you will accept that explanation either.

Dean2

Spot on. You can also kill an AGM prematurely from excessive heat or from multiple sequences of large discharge to low voltages and recharge, but they stand up better to that than regular Lead Acid. That said, I still run Lead Acid because they cost half, last nearly as long and Alberta weather is not hard on battery life. Typical Lead Acid one lasts at least 8 or 9years, Costco up here warranties Lead Acid for 100 months, full replacement to 48 months, prorated after that, same as an AGM.

Lexus4321

Battery lessons, again.
If the batt is 100%, then putting it on 14.4v with maybe 6-8 amps into the batt, is overcharging the batt.
Once batt is full it only needs float, which varies depending on temp, but around 75F float should only be 2.25v per cell, 12v batts are 6 cell, so 13.5v. Any voltage higher than that on a full 12v FLA, and it starts to overcharge (aka "damage"). Some odd misomer of what "overcharge" is. It is NOT just high voltage applied to the batt. If the batt is taking in 10amps, then it's taking in 10C/sec ! A full batt does not need to be forced 10C/sec.

On newer cars, they have charging controllers between batt and alternator, and when it detects a fill batt the alt voltage will drop to some lower voltage to reduced amps into the battery, which also take load off the alt, which saves fuel. Many new vehicles with these controllers will often seem like a bad alt on a meter, but it's just charge controller working.

It's also noted by many of the AGM batt makers, and others, that AGM's need more than 14.4v to do proper charging. Example, UPG lists absorption voltage 14.6-14.8. All the makers of AGM list float voltage below 14v. A car batt that is full needs nothing more than float, which of course does not happen in any vehicle unless the vehicle has active charge controller either controlling DC voltage form alt, or acting and a dc-dc buck between alt and batt. From what I have seen, Toyota manages the voltage by controlling regulator in the alt. When the batt is full the whole system drops voltage, alt is not defective generating just 13.3v

There's many examples documented, but one I just read was the batt provides around 500A for 3sec into the starter. That's 500C/sec * 3sec = 1500C. The batt then needs to charge to recover that 1500C, which could take 20-30min of alt charging. After it recovers that 1500C the batt only needs a float.

And yep, AGM's do dry out, just slower than the std FLA.

cssnms

Yea OK...

Lexus4321

If the batt is 12.77v, aka 100% full, and you swap it into a already running vehicle, attach the batt cables, and you amp clamp a batt cable, and it reads 8amps into the battery. Hmmm, the batt is full yet you are pushing 8C/sec into the batt. Does the 8C/sec just magically pass through the batt, or just get absorbed by the air in engine bay? Why would a full batt need 8C/sec? Answer is, it doesn't, and all you are doing is overcharging the batt, warming it, helping sulfation process, etc. Once full it only needs float, and this is exactly what the newer cars do.

I don't think the GX470 is properly equipped to run AGM batt. Which is probably one reason my AGM's keep dying every 3yrs. Maybe if I had the diode trick to boost alt voltage 0.5-0.7v my AGM's would last longer.
https://www.tacomaworld.com/threads/...ooster.611314/

cssnms

Tell that to the 2 Odyssey AGMs I've run in our GX. And no they didn't "dry up." 2nd AGM is still going strong.

You either bought a crap battery or your charging system is overcharging the battery i.e. bad voltage regulator. That is the ONLY way it will "dry up" that or a hole in the case.