need help for solar charge controller

[ch wazir]

If someone have a solar panels of 1400 watt,24 volt outputting approx. 60 A and have two mppt charge controllers rated at 30 A each,is it possible to connect the both in parallel to meet the required 60 A demand to charge the batteries 600AH where both the charge controllers are identical.Thanks

 

[iukhan]

The output of two 24V MPPT charge Controller can be combined. I would not recommend to combine the input of the controllers.

The best solution could be, connect half the number of solar panels to one charge controller and the remaining to other controller and combine the output to the battery.

 

[ch wazir]

hello jukhan,
thanks for quick reply,i didn't understand what will happen if input of both controllers are combined,plz explain it in somewhat detail if possible,regards.

 

[BradtheRad]

You need to make it impossible for either controller to draw more than its rated capacity.
By this rule you could hook up one half of your panels to one controller, and the other half to the second controller.

To charge the same battery bank, they should be adjusted to have identical charging envelopes.

I am not sure what harm would result if they do not transition from bulk charge to float charge at the same volt level.
Or if they turn on charging at a different low battery voltage. Etc.

Since you would be connecting the controllers' outputs, you also need to make sure that current can never flow from one controller back into the other. Perhaps by running tests using fewer panels, etc.

 

[ch wazir]

thanks BradtheRad for corect answer,regards.

 

[iukhan]

.....To charge the same battery bank, they should be adjusted to have identical charging envelopes.

ch wazir is using identical charge controllers. So this should not be a problem.

I am not sure what harm would result if they do not transition from bulk charge to float charge at the same volt level.

The transition from bulk charge to float will not harm anything even if there is some difference between float voltage level of both controllers.

Since you would be connecting the controllers' outputs, you also need to make sure that current can never flow from one controller back into the other.

I never heard /experienced that current flow back from battery to charger, so how can current flow from one controller back into the other.

 

[BradtheRad]

ch wazir is using identical charge controllers. So this should not be a problem.

Even though they are identical models...

They may have an adjustment on the pcb, which the user can change to suit his particular battery, and adjust the charging envelope.

The transition from bulk charge to float will not harm anything even if there is some difference between float voltage level of both controllers.

I do not suppose one or two tenths of a volt difference will cause a problem.

Nevertheless it is a good idea to observe the controllers during a few charge sessions, to see how they perform. The aim should be to obtain optimum performance. Whatever adjustments are made to one controller should also be made to the other.

I never heard /experienced that current flow back from battery to charger, so how can current flow from one controller back into the other.

Suppose the battery is disconnected. Will one controller try to 'charge' the other controller?

These are MPPT, designed to maintain highest ampere flow. With their outputs connected, each may try to generate a higher volt level than the other, with unpredictable results.

Hence my recommendation to carry out tests.

 

[ch wazir]

thanks both of you for detailed discussion ,now on i will carry out the test and will intimate the result accordingly.Regards,

 

[iukhan]

I have designed, developed and installed a number of solar controllers and panels. I never have faced any performance degradation. No adjustment is needed. Yes, a 24V controller cannot be connected to 12V.

Suppose the battery is disconnected. Will one controller try to 'charge' the other controller?

Nothing will happen. In most cases the charge controllers will not turn ON because they are designed to power up from battery. Even if this is not the case they will not charge each other. Power cannot flow back into the charge controller by design.

These are MPPT, designed to maintain highest ampere flow.

Correction please, MPPT charge controller are not designed to maintain highest current rather they are designed to maintain / extract maximum power from solar panel. Moreover controller have internal protections for overvoltage.

Now lets take an example, suppose that we have two charge controller one have float voltage at 27V and the other is 28V for a 24 volts system. (though in real life this much difference does not exist.). Assume that both controller are able to turn on without batteries.

Now let connect first controller to one set of panels. The output voltage will try to increase but then eventually settled at 27V. The controller will try to maintain the voltage. The same will happen for the other controller. The controller will try to maintain the voltage at 28V.

Now connect the two charge controller (Positive to positive and negative to negative). The voltage of first controller will increase from 27V. To maintain the voltage, the first controller will turn off its charging (No current flow). So, the voltage of combined controller will be 28V with almost 0A current (batteries disconnected). NO ISSUE OR HARM.

 

[ch wazir]

thanks mr jukhan.i m highly grateful for urs detailed response,regards

 

[BradtheRad]

I am satisfied with Iukhan's explanation in post #9.

 

[ch wazir]

Thanks both of you.Regards
Ch wazir

 

[ch wazir]

hello mr jukhan,
can one get the solar charger more than 24 volts ie 36 volt to 96 volts if available from where because these are not available in Lahore Pakistan electronics market or may u plz help provide a feasible mppt solar charger cct.which may be assembled locally.thank

 

[iukhan]

can one get the solar charger more than 24 volts ie 36 volt to 96 volts if available from where because these are not available in Lahore Pakistan electronics market

You can obtain solar charger for high voltage in Lahore from QPS www.qps-intl.com

may u plz help provide a feasible mppt solar charger cct.which may be assembled locally.

Due to contractual obligations, I cannot publish my design/code for MPPT charge controllers. But if you need assistance, in your design, I surely will help the best I can.