I just replaced the battery on my wife's 2006 'S' Cabrio, and one the dealer sold me is slightly different from the one that came with the car in 2006. Specifically, there's no nipple on the new battery to attach the vent tube - in fact, the new battery appears to be sealed.

Is it an AGM battery, a gel cell, or just a conventional battery that happens to be sealed? The reason I'm asking is that my battery charger has a button on the front for selecting between conventional, AGM and gel cell, and I want to make sure I'm using the correct setting.

Thanks,
Scott

 

hmmmm, didn't know there was a difference in charging for an AGM

guess that explains why my cheap-*** HF charger freaked when I hooked it up to an OPTIMA . . .

and I now see OPTIMA is releasing their own super-duper charger . . .

check off today for learning something new!

 

Scott: Someone who knows about batteries (probably not me) might be able to help if you specify which battery you bought.

 

I, too, am not aware of any charging differences between a conventional lead/acid battery and an AGM.

 

The manual for my charger doesn't go into specifics as to the different charging schedules for conventional, gel cell and AGM batteries, but from what I can find on the web, AGM/Gel Cell (especially Gel Cell) batteries require a lower charging voltage compared to conventional batteries.

 

I find it somewhat surprising that AGM would be any different from conventional batteries. The AGM is just a conventional battery with conventional acid that has glass mats between the cells. Yuasa, who makes very high quality batteries for motorcycles and other types of sport vehicles makes no distinction between conventional and AGM with respect to charging.

Gell batteries use a different acid formulation, though.

 

been digging and a few google searches will yield a number of references for the problems with basic chargers vs gel and AGM batteries . . .

here's one for AGM: http://www.hotrod.com/techarticles/g...y/viewall.html

with regard to gel
Some other disadvantages of gel cells is that they must be charged at a lower voltage (2/10th's less) than flooded or AGM batteries. If overcharged, voids can develop in the gel which will never heal, causing a loss in battery capacity.

found in http://www.windsun.com/Batteries/Battery_FAQ.htm

 

Also, I think some of the older low-tech chargers use wicked-high charging voltages, like 16-18V. Evidently, conventional batteries can handle that well *enough*, but not AGM or Gell Cells. I agree that most modern chargers probably use almost-identical charging profiles for AGM and conventional batteries anyway, so the only thing you really have to treat in a "special" way are Gell Cells.

 

Neither of those two articles says much. The first only hints at AGM being different because of their statement about special AGM chargers being marketed and sold. But just because something is sold and marketed doesn't mean it's necessary or required.

The second article makes no distinction between conventional lead acid and AGM other than to say a certain brand will accept a much higher charge level than others. Otherwise it can be inferred from the article that conventional and AGM have the same charging requirements and only gel batteries have some special considerations.

The main thing is to make sure you're not putting too much current into a battery and to also make sure that if you're not using a smart charger that monitors battery charge level and adjusts accordingly, that you don't just leave the battery hooked up to the charger indefinately.

 

seems to me the major thrust of the first article is that a deeply discharged AGM may be 'invisible' to simple or older charger aka "the won't take a charge" issue; but those chargers can be tricked into seeing the battery, or presumable newer chanrgers with an AGM setting would 'see' them.

I know that was the case with my cheap charger and a flat as a pancake OPTIMA. The charger just cycled continuously onn and off, leaving me to believe the battery was completely toast. But alas, not the case . . . avoid the full discharge and you'll never encounter the issue.

Second - Gels seem to dislike the full push of a cheap rapid charger and you may damage the battery

But there is a lot of stuff to wade thru to get to those points I suppose....

 

Nothing new about chargers not seeing a battery. It can happen with any battery type, including conventional car batteries and gel batteries.