Battery

[tanuie]

Had to have a new battery today as the car wouldn't start, went to my local Mercedes indy who fitted one straight away. As it wouldn't start outside Tesco's i had to phone the AA, who came out within 30mins, well impressed.
The new battery is an MB one and i was told it was a gel battery opposed to an acid battery, what is the difference between the two.

 

[190]

Different types of battery:

The standard wet cell with liquid electrolyte usually these days the battery is low maintenance which means it very rarely needs topping up with water.

Then there are two type of battery where the electrolyte is imobilised and never needs topping up:

AGM or Absorbent Glass Mat batteries have the electrolyte absorbed in a fibreglass matting that is in contact with the plates. AGM's have very superior cranking power and they are often specified for stop/start vehicles.

Gel batteries have silica mixed in with the electrolyte to turn it into a gel. Gel batteries are more tolerant of deep discharge but to be honest straight Gel batteries are not often used for automotive purposes because they are easy to damage through over charging and they don't have quite as much cranking power as AGM's.

Just to confuse matters recently there has been a 3rd type:

Gel/AGM hybrid batteries have the advantages of both AGM and Gel. They work better in automotive applications than standard Gel's because they will safely accept a higher charge voltage. Many 'experts' have told me there is no such thing as an Gel/AGM hybrid battery but I assure you there is and I have one, not in my car but in my motorcycle. I suspect this is the type of battery you have.

 

[OneForTheRoad]

Battery School | Batteriesnorthwest.com | General Difference Between Gel and Wet Batteries

 

[markjay]

One other advantage of Gel/AGM batteries is that due to having no liquid they don't have to stay upright and are therefore better suited for applications such as rally or extreme off-road.

 

[Tommy Kaira]

I recently learned that Mercs can be very sensitive to non-OEM batteries so it's worth going for the genuine one. Gel batteries are, as mentioned above, not as susceptible to rough treatment and can be placed in any orientation. This is a benefit in an accident too as it's one less fluid to come spilling out.

 

[David404]

12v batteries like to be brought up to 100% charge on occasion, keeps them in tip top condition but alternators cant be relied on to do this reliably. I understand (feel free to jump in and correct me if you think I'm wrong) that Gel batteries can be difficult to charge and can even be damaged by incorrect charging.

I have a Ctek charger that I got for bench charging leisure batteries, works a treat, can be left on charge without fear of damaging the battery and they are rated for lead acid, Gel and AGM batteries. Not cheap and not fast chargers but if you'd like to be able to charge to full capacity occasionally useful kit. I use mine to bring car battery up to full charge 3 or 4 times a year and you can tell when turning over on the starter.

 

[190]

12v batteries like to be brought up to 100% charge on occasion, keeps them in tip top condition but alternators cant be relied on to do this reliably. I understand (feel free to jump in and correct me if you think I'm wrong) that Gel batteries can be difficult to charge and can even be damaged by incorrect charging.

Alternators on older cars may not 100% charge some the newer batteries like AGMs which need a higher charging voltage. The problem with the newer cars is even if you finish a journey with a fully charged battery the car will take an amp hour or two out of the battery while it's going to sleep especially if you open the door a few times.

Gels are not hard to charge but they are sensitive to being overcharged. The same is true for any valve regulated battery which when overcharged will vent off the electrolyte in the form of gas. Standard wet cells will do the same but unlike a wet cell you can't top up a gel battery so it will eventually die if continually overcharged. Basically you need a voltage regulated charger which most are these days.

Most of the bad rep for gel batteries stems from using old basic battery chargers that were just a transformer and diodes with no electronic voltage regulation. The output on those old chargers would rise to 16 or 17 volts once the current dropped towards full charge and that will gas off any battery.