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How to choose the correct battery charger?

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How to choose the correct battery charger?

1. What do we need to know about chargers?

Firstly, we need to be aware that there are different chargers with different outputs. For example, their voltage output may vary from 6V to 12V and 24V. There are different output currents as well as overcharging protection. Typically these chargers are equipped with overload protection, back-up protection and short-circuit protection.

Most newer chargers adjust the charging current and voltage automatically. For proper charging, the current of these chargers should not exceed 10% of  the battery capacity. For instance, if the battery has a 70Ah (Amp/Hour) capacity then the charging current should not be higher than 7 Amps (A).

The lower the current, the more it takes to fully charge the battery. We already mentioned that there are different overload protections. First type of overload protection is when a green lamp lights up and the charger turns off automatically. Second type is when the charger uses a trickle charge to just maintain the reserved power inside the battery without overcharging it. The second type of overload protection is mainly used for off-season batteries such as for ATVs, UTVs, motorcycles, etc.

2. Charging SLA Batteries:

We strongly advise to charge a battery only in a well-ventilated room since gas is released during charging which is flammable and poisonous. Also, avoid contact with the electrolyte because a dissolved sulfuric acid is created during the recharging.  If by accident, acid spills on your clothes it will damage them so you should use a baking soda to neutralize the effect of the sulfuric acid.

If you need to charge a 12V battery then you will have to use a 12 volt charger. Same applies for 6V batteries - 6V charger is required. Chargers that have 24V output charge two 12 volt batteries simultaneously. Before purchasing the charger you need to make sure that the charger voltage matches the battery voltage. The aforementioned 24 volt battery set is a result of two 12V batteries connected in series, which use the a 24 volt output. They can also be charged separately. Hence, the two 12V batteries will have to use two 12V chargers. 

3. For how long should I charge my battery?

There is a simple formula used to calculate the charging time of a battery. For example, we have a 12 Volt 7 Amp Hour battery and a 12V 1 Amp Charger. The formula is: (7*1.3)/1 which gives us approximately 9 hours of charging. This formula is under the assumption that before recharging the battery is completely discharged which is rarely the case. 

In other words, to estimate the charging time you have to multiply the AH of the battery by 1.3 and then divide the result by the amperage of the charger. 

4. Choosing the correct charger:

Simply said, the higher the amp hour of a battery, the higher the charger amps you will need to charge the battery. However, for maintaining  the charge a lower amp charger will work just as well. We have prepared a table that will hopefully make things easier when choosing the correct charger for your battery:

Battery AH

Charger Amps

Under 7AH

500 mAh - 1 Amp

7AH - 20AH

1 Amp - 2 Amps

21AH - 40AH

2 Amps - 3 Amps

41AH - 75AH

3 Amps - 5 Amps

76AH - 100AH

6 Amps - 10 Amps

101AH - 125AH

10 Amps - 15 Amps

126AH and up

15 Amps - 20 Amps

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