AGM batteries are in great demand today. Many automakers install them in their cars, in particular, BMW and Mercedes-Benz. The reviews of car owners show that the service life of such batteries reaches 5-10 years. During this time, ordinary acid-lead batteries fully exhaust their resources.
However, AGM units have a number of drawbacks:
- they do not tolerate deep discharge
- they must not be started from another car since explosive oxygen and hydrogen are released due to chemical reactions under the influence of an electric discharge
- extreme sensitivity to increased charge
- quick discharge due to possible current leakage
If you have such a battery on your vehicle, do not allow it to discharge. Accordingly, the question arises: how do you choose the best AGM battery charger and exploit it safely?
AGM battery charging tips
First of all, do not leave an AGM unit without supervision while charging. You should closely control voltage and temperature. Otherwise, you may encounter such a phenomenon as thermal acceleration. What is it?
Simply put, this is an electrolyte heating. When the liquid is heated, the resistance decreases. Respectively, higher charging current can be delivered. As a result, a battery starts to warm up and the risk of a short circuit arises. In such a case, it is necessary to immediately stop charging and take a break for cooling.
Recommendations on safe AGM battery charge:
- use chargers with a shutdown function
- the best option is an electronic charger with IUoU charging mode (multi-stage charging)
- do not charge cold or overheated (above +45°C) batteries
- the room must have good ventilation
Voltage an AGM battery needs
The normal, 100% charge level for an AGM unit is 13 volts. If this value decreases to 12.5 or lower, the unit must be urgently charged. With a charge below 12 volts, the battery would need to be 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 cells shorting, which causes overheating and evaporation through the outlet openings.
The IUoU charging mode (it can be selected automatically on an electronic device) consists of several stages:
- charging with a stable current (0.1 of the battery capacity) with a voltage of not more than 14.8 volts
- charge accumulation with 14.2-14.8 volts
- maintaining a stable voltage
- “finishing” – float charging with 13.2-13.8 volts, until the voltage on the battery’s electrodes reaches 12.7-13 volts
The advantage of an automatic charger is that it controls various charging parameters and switches itself off or lowers voltage and current when the temperature rises. If you use an ordinary charging tool, then having gone away even for a short time, you risk burning the fiberglass that cannot be restored.
If you remove a battery from a car for winter storage, it must be regularly charged with floating currents (voltage of not more than 13.8 volts).