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A charge controller keeps the battery bank from being overloaded as electricity from from solar panels are transmitted. This will only work if the controller can handle the watts being produced by the solar panel and the battery voltage. That is what we will cover in this guide.
A 60 amp charge controller has a maximum capacity of 1440 watts for a 24V solar panel system and 2880 watts for a 48V system. These charge controllers are mostly for 24V and 48V solar panel systems, and are not designed for 12V batteries which are commonly used with 18V solar panels.
Calculate Charge Controller Watt Capacity
The formula is amps x volts = watts. You have to know the solar panel system voltage to get the watts. A safety margin of 25% is also recommended to offset power fluctuations. Here are the most common charge controller amps and their matching volts and watts used today.
- 60 amps x 12 volts = 720 watts
- 60 amps x 24 volts = 1440 watts
- 60 amps x 48 volts = 2880 watts
Those are the maximum wattage levels the charge controller can deal with. The 25% safety margin suggests reducing the wattage output by 25% or get a bigger charge controller size.
While 60 amp charge controllers like the PowMr Controller are ideal for 24V and 48V solar panels, a 12V solar panel requires a 20 amp controller. The most common charge controllers are sold in 12V, 24V, 48V and 60V. The highest amp rating is 60 and voltage capacity is from 6 to 60V.
With an MPPT charge controller, it is the battery voltage, not the solar panel voltage, that gets charged. The battery bank voltage determines how many watts of solar power you can run. With a PWM controller the output is more limited. PWM controllers can work on small solar panel systems, but for heavy watts and amps usage, MPPT i better.
Controller and Battery Voltage
The solar panel voltage must be higher by 25%-30% than the battery voltage when charging. A 12V battery requires a 15-18V solar panel, a 24V battery needs a 20-30V solar panel and so on. The charge controller must be capable of meeting these demands plus an extra percentage for safety. With an MPPT controller the voltages are equalized.
So there are two factors to consider here, the voltage of the solar panel and the battery. Because the controller manages current going into the battery, it is of primary importance. The battery voltage cannot be higher than the controller.
To keep charge controller sizing simple, it must be large enough to handle the amps and voltage the solar panel is producing. If the voltage is 24 and the amps 30, the charge controller must be at least 30 amps. Add another 25% for the safety margin and the controller amps should be 40 or 60.
Calculate Charge Controller Battery Capacity
A device such as the OneSolar 60A charge controller can handle a battery up to 60 amp hours if it is 24V or 48V. A 36V 60 amp battery might not be compatible so check the controller specs to be sure.
What if you have a 12V battery at 60 amps or less? As mentioned earlier, it probably won’t run regardless of the battery type. But if your controller is compatible, you can connect it as you would any controller to a battery.
The rules for charging batteries applies whether the controller is 60 amps or lower. For lead batteries that means a depth of discharge at 50%. For lithium ion it can be 75% or higher. If you have a lead acid battery that means only half the amps / watts are usable for each charge, so include that in your calculations.
Because batteries and charge controllers both use amps, there is no need to convert amps into watts. You only need the conversion if you want to know the controller’s maximum solar panel capacity. However it really depends more on the battery and its usage.
If the battery is 100ah but you only use 50 amps or less an hour, the charge controller will run fine. There will only be problems if the draw exceeds the controller capacity.
Note that charge controller load outputs and sizes are not an exact match to watts and battery amps. Most common MPPT and PWM controller sizes are 10, 15, 20, 30 and 60 amps. If your system requires 20 amps, use a 30 amp controller, but if it needs 30, go for 60. It never hurts to go a bigger size.
Going for the next biggest size is playing it smart. You will end up with more than a 25% safety margin, but it provides peace of mind and second, you can expand your system and the controller will still hold up.
Can You Connect Two 60 Amp Charge Controllers?
You can connect two charge controllers on one battery bank to boost capacity. This can be handy if you need a lot of power available. If you have set up a solar shed or a solar powered motor, using two charge controllers will increase power.
Most off grid systems and large solar arrays draw thousands of watts and amps, so a single charge controller will not be sufficient. In these cases you can hook up two or more 60 amp controllers (or any amp size for that matter) to one battery bank.
Make certain the battery can handle the increased current. Batteries each have their own limits so check the product manual before adding another charge controller. The configuration will also depend on whether you want to increase the amps or the voltage.
60 Amp Charge Controllers: MPPT vs. PWM
MPPT controllers are also designed to work with unusual and high voltage ratings. When an MPPT senses there is a voltage difference in the system, it reduces the higher voltage to match the lower voltage. The solar panels, battery and charge controller end up with the same voltage rating.
An MPPT charge controller is better suited for 60 amps because it can handle higher voltages without losing energy. An MPPT controller also works better in cases where the solar panel voltage is higher than the battery voltage.
If your solar array is 800 watts, 48V and paired with a 24V battery, divide the watts by the lower volts.
800 / 24 = 33.3
33.3 + 25% = 41.6
So you need a 41.6 amp charge controller,. Rounded off, you should get a 60 amp unit as it’s more common than the 50 amps.
This formula can be used for other solar panel sizes, batteries and controllers. It is easy for a newcomer to get confused with the different voltages and not be sure which to use. That is where MPPTs come into play and make a difference. They remove all the complications and ensure all components are at the same rating.
Tips for Using 60 Amp Charge Controllers
Charge controllers today are durable and designed for long term use. However you will get more out of them by applying the following tips. Note that these apply not just for 60 amp controllers, but also those of other sizes too.
Consult a Professional Expert
If you are still unsure whether to get an MPPT or PWM, or what capacity is suited for your solar panel, consult an expert. Hooking up the wrong controller to the battery and solar panel can lead to system overload and damage the components. By seeking guidance you will be able to avoid this.
So you have figured out that 60 amps is right for your system, but for how long? An MPPT controller is not cheap, so think of the foreseeable future. Are you going to need more amps? Are you going to load a solar welder or other power tools into the system?
If you have any plans of expanding, consider adding another controller. 60 amps an hour is a lot of power, but that gets used up fast if you load a motor on the batteries. On the other hand, think also if 60 amps might be too much. Depending on the setup you may be better off with a 30 amp controller instead.
The charge controller needs to be properly connected to the battery bank and the PV modules. Your instruction manual will provide directions for the specific location of the device so use those as reference.
It should be stressed that the distance between solar panels and batteries affects performance, and so does the controller location. By optimizing the installation spots, you will get the best possible results when you run the controller.
The wires and cable connections have to be secure as well. You decide whether to configure multiple controllers in a series or parallel, as it will depend on your power requirements. Make sure to test the controller and the other components before connecting any large appliances onto the system.
Solar panels, controllers and other components are safe to use, but accidents can happen if you are not careful. Charge controllers perform important tasks, and if if is not installed correctly, you may be caught unaware in case the battery bank overload. That is why you should only buy high quality charge controllers and follow the installation instructions carefully.
With all the conversion formulas needed to manage solar panels, batteries and charge controllers, it can be somewhat confusing for a newcomer. But as shown here you only have to learn a few basic formulas and you are good to go. Because charge controllers play an important role in battery charging, choosing the right one is crucial.