AGM batteries are capable of being charged at a faster rate, and may draw additional amperage from the alternator if it is not regulated. Many cars that come with AGM batteries have special charge rates (newer Porsche Cayennes that come with AGM batteries have a setting in the computer for this, for example).
I have an older Porsche Cayenne Twin Turbo that does not come with an AGM battery. Is it always safe to replace standard batteries with AGM variants?
Yes for the most part an AGM is a drop in replacement for your standard Lead Acid Battery. The charging voltages are almost identical. You are correct that they have a lower internal resistance and can be charged at a much faster rate. This shouldn't cause a problem on the majority of vehicles as the wiring in the car is designed to handle the maximum rated output of the alternator.
I put a AGM battery in my audi a4 1999 , and the computer got confused enough to throw up annoying symbols on the dash , like bulb out errors and the like , so i changed back to excide premium 90AH , I recon the cars computer just could't figure out what had changed ,with the AGM being able to be recharged 5 times faster than the standard battery , but no damage done , every day is a school day .
I agree with Lee. I just put 2 AGM batteries in my 08 G8 Gt thinking it was going to be better and after some research it seems that older cars don't know how to deal with the AGM format when replaced being that the alternators aren't programmed to deal with AGM batteries. I started seeing high voltages when starting the car (15.6v) then after driving about 6 miles, the voltages would drop to 14.8v (normal for my car), then after 15 miles it would drop to 13.2v (definitely not normal). Got both batteries tested and they both show they're bad. I figure the initial charging of 15.6v (which I've never seen in my car before the install of this battery) is killing the unit. Going back to Autozone to switch back to a regular battery when I get off work.
With that said, let's not push everyone to install AGM batteries in their cars if the car wasn't designed to use it.
The following paragraph from this site helped me draw this conclusion:
https://atempower.com/blogs/news/three-misconceptions-about-agm-batteries
"While the installation of the battery may be the same for the two battery styles, some vehicles require an extra step to tell the vehicle that the battery has been replaced. Newer vehicles have a Battery Sensor Module or similar systems. These systems require recalibration with a scan tool if the battery is replaced. If the system is not recalibrated, the alternator might overcharge the new battery and cause the battery to fail soon after replacement."
Disconnect the battery sensor, you can then use what-ever battery you like as the EMU does not know what type of battery is now installed and reverts to a standard charging regime which is OK for both types of battery. I have a Merc and 981 Cayman both have the sensor disconnected, I did it on both cars to get rid of stop/start.
Rob.
I'm getting reduced gas mileage on my AGM upgrade for my Honda 2015 Civic. I know it's a lot of money for a battery for the car but I need reliable winter time starting but not the reduced gas mileage I lost 4 miles a gallon when I went to the agm. And that's keeping in mind I had a bad cell in the old battery. Which was starting fine in the summer just didn't want to risk it in the winter.
One thing a lot of folks neglect to consider when replacing/upgrading from a bad battery with dead cells. The battery has been going bad for quite a long time before the cell died.
The alternator and it's regulator has been working harder trying to optimize charging of the battery and compensating to operate all the other electronics in the vehicle while the battery was gradually going bad.
By the time the cell in the battery died, the regulator and alternator both have been working at max output that stressed their components beyond their limitations. Once you connect the new replacement or upgraded battery, it sends a shock into the regulator and alternator which causes one or both of them to malfunction.
Best case scenario, the regulator pops and the alternator stops working altogether. Worst case scenario, the regulator overloads the new battery, which damages the battery and fries the alternator. This can also lead to catastrophic damages to the vehicle's ECM/ECU.
To reduce the risk of these conditions occurring, it's a good idea to get a battery tender that reconditions the battery cells and use it once or twice a year. This drastically increases the lifespan of your battery and reduces the risk of damages to the alternator, it's regulator, and any other components of the vehicle.
If you're replacing a battery with a dead cell, it's a really good idea to either replace the alternator or have it properly tested and then replaced if it's not working at optimal performance.
