AGM or Standard 12v charge mode?

[Warmywhite]

I have a 2018 Mercedes GLC Coupe with an AGM battery(I think). I seldom use it after leasing an EV and get regular emails warning of critical low battery.
When switching on the Draper 53491 smart charger it went to 12v STD. Later I noticed it had changed to 12v LFP charging. I changed the mode to 12v AGM charging. Is this the correct thing to do or should it charge in 12v STD mode? I don't want to damage the battery.

Thanks in advance.

 

[190]

It don't do any harm either way although the AGM mode will charge an AGM more fully as the std mode charges to 14.5 volts and the AGM mode to 14.8 volts. Both modes float at the same voltage of 13.8. Even if the battery isn't an AGM, short term use of a few hours on the AGM mode won't harm it but I wouldn't leave a standard battery on that mode long term as it may never reach the float stage It's far more of a concern that the battery is getting to the critical low stage which will be talking a toll on the batteries prospective life span. An infrequently used car needs a routine charge every week or two.

 

[Warmywhite]

Thanks very much for your reply. I've checked the label on the battery and it does indeed state AGM.

I'll be sure to take your advice and charge the battery regularly. My initial thoughts were to leave the Draper charger connected all the time to maintain charge but not sure if this is sensible.

 

[DSM10000]

Thanks very much for your reply. I've checked the label on the battery and it does indeed state AGM.

I'll be sure to take your advice and charge the battery regularly. My initial thoughts were to leave the Draper charger connected all the time to maintain charge but not sure if this is sensible.

If the car has Stop /Start then it should be an AGM battery. It should be marked on the battery so you can check.

 

[chic0821]

Get a Ctek MXS 5 then you can leave it on forever. Mine is on for 6 months at a time. Car starts first time. Below is blurb from Ctek

The MXS 5.0 is an advanced microprocessor controlled battery charger which gives unrivalled performance for lead acid batteries from 1.2-110Ah. It comes with automatic temperature compensation built in which ensures the best charging performance, even in the most extreme conditions. The MXS 5.0 also includes battery diagnosis to establish whether your battery can receive and retain a charge, patented automatic desulphation program, an AGM option which maximises the performance life of most Stop/Start batteries and a special Recond mode for reconditioning deeply discharged batteries. The MXS 5.0 uses CTEK’s patented float/pulse system, which is the most efficient maintenance mode when a battery is connected for long periods.

 

[Warmywhite]

Just bought the Draper one after reading AutoExpress reviews online but thanks for that.

 

[alabbasi]

Just look at the battery , it will say if it's AGM and if it has a vent hole on any of the sides, it will likely be a regular lead acid. Most cars now with batteries in the cabin (like under the back seat) will be AGM.

AGM batteries will have different charging characteristics. If you change from one to the other, you're supposed to go into the cars programming and change the settings in order to get maximum life of the battery. Not that any battery will last more than 5 years in Texas.

 

[OneForTheRoad]

Just look at the battery , it will say if it's AGM and if it has a vent hole on any of the sides, it will likely be a regular lead acid. Most cars now with batteries in the cabin (like under the back seat) will be AGM.

AGM batteries will have different charging characteristics. If you change from one to the other, you're supposed to go into the cars programming and change the settings in order to get maximum life of the battery. Not that any battery will last more than 5 years in Texas.

AGM batteries have vent holes in the side .

 

[190]

AGM batteries have vent holes in the side .

A vent on an AGM may not be so obvious but they will have one somewhere because it's a vent for a safety valve. Without a vent you have a potential bomb in the event of gross overcharging causing the battery to gas off and pressurise.

AGM's are VRLA's Valve Regulated Lead Acid batteries which work at a slight pressure above atmospheric when being charged in order to recombine vapours back to liquid when they gas off. They are sometimes called sealed batteries but that's only true in normal operation. Gross overcharging will cause them to exceed the safety valve pressure and make them vent with a loss of electrolyte. The vent may not be routed away from the battery but it's better than the battery going bang.