Frequently asked questions about battery chargers
Can my charger be used with lead acid and gel batteries?
Possibly. Some chargers can be adjusted manually to recharge either conventional Lead acid or sealed Gel batteries. This is usually done by means of an output adjustment screw or toggle switches. If your charger is not suitable the batteries will fail prematurely. If you are in any doubt you should contact the charger manufacturers.
Can a standard car charger be used with my batteries?
If you are recharging a car or van the answer is yes. If you want to recharge large commercial batteries you must ensure the charger output is sufficiently high enough before charging commences. If you are charging deep cycle or traction batteries the answer is no. Deep cycle and traction wet lead acid batteries require a higher charging voltage and charge current than the average automotive charger can produce.
How long will it take my batteries to fully recharge?
The amount of time it takes a battery to charge depends on the type of battery and charger and on how long it took to discharge (slow or fast). As a rule of thumb you can divide the battery capacity by the maximum charge capacity and add four hours. The four hours is for the so-called after-charging time, where the battery determines how much more current it needs to get back to a fully charged state. For example, an empty 200 Ah battery connected to a 40A battery charger would take about 200 divided by 40 = 5 + 4 hours to charge, 9 hours in total. If the battery had been only 50% discharged the calculation would be: 100 divided by 40 = 2 + 4 hours, 6 hours in total.
When do I need to perform an equalization charge?
Equalizing should only be performed on vented wet lead acid batteries. How often this might occur with your battery will vary depending on your application. You will need to monitor your battery voltage and specific gravity to determine when equalization is needed. For example, it is time to equalize if the measured specific gravity values are below manufacturer’s recommended values after charging (recommended value for Trojan Deep Cycle batteries is 1.277 +/- .007 at 80o F). Equalizing is also required if the specific gravity value of any individual cell varies 30 points or more. Reduced performance can also be an indicator that equalizing is necessary. Equalization should also be performed when individual battery voltages in a battery pack range greater than 0.15 volts for 6 volt batteries or 0.30 volts for 12 volt batteries. A good rule of thumb is to perform equalize charging once every 10 cycles.
What type of charger should I buy?
An automatic charger offers the greatest convenience. Just plug the battery into the charger and the charger does the rest. Manual chargers, although equally effective at charging batteries, require a greater level of attention.
What size charger should I buy?
A properly sized charger takes into account battery capacity and the time interval between charges. In applications where cycling is infrequent, such as weekend users, or infrequent or seasonal usage, a charger with an output current rating between 10 and 13% of the battery’s rated 20-hour capacity will suffice. In applications where battery recharge must be accomplished within 8 to 10 hours, a three stage, automatic charger, rated at 20% of the battery capacity, may be required.