How to charge an AGM car battery? In no case..
AGM batteries are in great demand today. Many automakers install them under the hoods of their cars, in particular, this applies to BMW and Mercedes-Benz. Well, manufacturers such as Varta or Bosch produce batteries using AGM technologies. And, judging by the reviews of car owners, the service life of such a battery reaches 5-10 years. During this time, conventional liquid lead-acid batteries, as a rule, fully develop their resource.
However, no matter how far technology has gone, the ideal battery has not yet been created. AGM batteries have a number of their own disadvantages:
- they do not tolerate deep discharge;
- they cannot be lit from another car, since, due to chemical reactions under the action of an electric discharge, explosive oxygen and hydrogen are released;
- extremely sensitive to charge increase;
- quickly discharged due to possible current leakage.
In any case, if you have such a battery on your car, you should not allow it to discharge. Accordingly, the question arises - how to properly charge an AGM battery? The problem is further aggravated by the fact that motorists often confuse AGM batteries with Gel technology. By and large, AGM batteries are practically no different from conventional batteries, it's just that the electrolyte in them is in microporous plastic, and this imposes some problems. For example, during recharging, the mixing of the electrolyte does not occur at such an active pace as in conventional starter liquid batteries.
Ways to charge AGM batteries
First of all, the vodi.su portal notes that it is impossible to leave an AGM battery without supervision during charging. It is necessary to control not only the strength and voltage of the current, but also the temperature. Otherwise, you may encounter such a phenomenon as thermal acceleration or thermal runaway of the battery. What it is?
In simple terms, this is the heating of the electrolyte. When the liquid is heated, the resistance decreases, respectively, it can receive even more charging current. As a result, the case starts to really heat up and there is a risk of a short circuit. If you are faced with the fact that the battery is heating up, you need to immediately stop charging and allow time for cooling and diffusion so that the electrolyte is mixed.
We would not recommend listening to the advice of acquaintances or various bloggers who often write articles without really understanding the material. If you have an AGM battery of one or another manufacturer, it must come with a warranty card and a booklet that describes the methods and conditions of charging.
So, the manufacturer Varta gives the following recommendations on how to charge AGM batteries:
- use chargers with a shutdown function;
- the best option is electronic chargers with IUoU charging mode (multi-stage charging, which we will write about below);
- do not charge cold or overheated (above + 45 ° C) batteries;
- the room must be well ventilated.
Thus, if you do not have a special charger that supports various charging modes, it is better not to start this event, but to entrust it to experienced battery workers.
AGM battery charging modes
The normal, 100 percent charge level for an AGM battery is 13 volts. If this value drops to 12,5 and below, then it must be urgently charged. When charging below 12 volts, the battery will need to be “overclocked” or revived, and this process can take up to three days. If the battery starts to discharge quickly, and there is a smell of electrolyte under the hood, this may indicate a short circuit of the cells, which causes overheating and evaporation through the exhaust holes.
IUoU charging mode (it can be selected automatically on the electronic device), consists of several steps:
- charging with a stable current (0,1 of the battery capacity) with a voltage of not more than 14,8 volts;
- charge accumulation under voltage of 14,2-14,8 Volts;
- maintaining a stable voltage;
- “Finishing” - charging with a floating charge of 13,2-13,8 Volts until the voltage on the battery electrodes reaches 12,7-13 Volts, depending on the calculated value.
The advantage of an automatic charger is that it monitors various charging parameters and independently turns off or lowers the voltage and current when the temperature rises. If you use ordinary charging, then you can, even for a short time, burn the mat (fiberglass), which cannot be restored.
There are also other modes:
- IUIoU - at the third stage, stabilization occurs with higher currents (suitable for batteries with a capacity of 45 Ah or more);
- two-stage charging - supply of the main charge and its “finishing”, that is, storage at a floating voltage;
- charging with the main current - 10% of the capacity and voltage up to 14,8 volts.
If you remove the battery for the winter and put it in long-term storage, it must be regularly charged with floating currents (under a voltage of no more than 13,8 volts). Qualified battery workers at the service station know a lot of other ways to revive the battery, for example, they “accelerate” it at low currents for several hours, then check the voltage in each of the cans.
As stated in the warranty for Varta AGM batteries, their service life is 7 years, subject to full compliance with the manufacturer's requirements. In general, this technology has proven itself from the best side, since the batteries easily tolerate strong vibrations and start the engine well at low temperatures. The fact that their sale price is gradually decreasing is also encouraging - an AGM battery, on average, costs twice as much as its liquid counterparts. And more recently, the price was almost three times higher.
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