What is Battery Level?

    What is Battery Level?

    An Solar battery It will indicate a certain voltage depending on the charge level in which it is at all times. This is very useful to know exactly your charge percentage.

    To do this, it is necessary to watch it at rest, that is, at least an hour after disconnecting the loads (either from the panels or from an external source such as a generator set. It must be done this way since as long as the batteries receive current, their voltage will be distorted and will not be the real one.

    The following voltage/charge level relationship is suitable for all types of solar batteries, whether monoblock solar, AGM, Gel or stationary batteries:

    Battery charge level


    In relation to batteries with maintenance, the level of electrolytes (liquids) should be checked approximately every 30 days to extend their useful life. If the liquid level is low, it is recommended to fill it up to the indicated level with distilled water and carry out a charging process.


    To find which fuse we have to use we will have to divide the power of our inverter by the voltage of our solar installation.

    Example: For a 3000w inverter that operates on a 24 volt system, the formula would be the following:

    In this case we would need a fuse that is around 125 Ah for proper protection.

    Battery connection method

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    1. Bulk Stage:

    In this first stage, current is supplied to the battery at maximum intensity, so that the voltage (voltage) increases rapidly until it reaches approximately 12,6 V, and then gradually until the first voltage limit. Once this limit is reached, the battery is 80-90% charged. From this point on, the charging current absorption is reduced rapidly. We are now at a potential of 14,4-14,8 V depending on the battery. If you want to charge a battery bank, the voltage limit would be between 10-20% of the nominal current of the battery, that is, between 100-200 A for a 1000 A/h battery bank. At this stage the Charge regulator that is located between the panel and the accumulator does not play any role, since the current is supplied at maximum intensity, but without it the Bulk phase would be permanent and the current coming from the solar could destroy the battery due to overcharging.

    2. Absorption Stage:

    In this phase the charging current slowly decreases until the battery is charged to 100%. In this stage we work at the voltage reached at the end of the Bulk stage, called the absorption limit. It is important to know the values ​​of the voltages used accurately and always in accordance with the manufacturer's instructions. The purpose of this stage is to recover the electrolyte, which may have been altered in deep discharge processes, so in batteries that have undergone a prolonged deep discharge, the absorption phase will be longer to ensure that the electrolyte is completely recovered.

    3. Flotation Stage:

    In this phase the battery is already charged to 100% and what is done is to provide the necessary current to compensate for self-discharge, so that it remains at 100%. It works at low and constant potentials. If the battery is intended to be stored, the float voltage cannot vary more than 1% from that recommended by the manufacturer. For liquid batteries, it is recommended to provide voltages between 12,9-14 V, although the uselessness of the battery for long periods (months) is not recommended. On the other hand, gel batteries can be left in the floating phase for long periods without problems.

    4. Equalization Stage:

    Its purpose is the rise of the gas within the acid (electrolyte) making the solution become homogeneous; This is why it is also called the gas stage. In this way we avoid a higher density at the bottom that could cause sulfation of the plates. After this stage we ensure that all the cells have the same voltage. The controller can carry out this stage every certain period of time; if it is intended to be done by hand, it should be carried out if a disparity in values ​​in the density of the electrolyte is detected.

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