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Old 09-01-2015, 13:01   #1
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24.9v 135w solar into pwm 12v system?

My last panel died and I need to replace I am looking at a 135W 24.9vmp panel. I have a Prostar PS 15 PWM controller with a 12v system. It is only a few bucks more for the extra 35w compared to the 100w 17.9vmp panel.

Will the extra voltage have any adverse effects to my system Ie controller?
The controller manual does not list a max voltage from the solar panel. Only that the controler will sense the voltage of the battery.
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Old 09-01-2015, 14:18   #2
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Re: 24.9v 135w solar into pwm 12v system?

Most controllers have a maximum amperage capacity. Better check that first.
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Old 09-01-2015, 15:27   #3
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Re: 24.9v 135w solar into pwm 12v system?

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Originally Posted by onestepcsy37 View Post
Most controllers have a maximum amperage capacity. Better check that first.
The amperage of the panel does not increase from the 100w to 135w just the voltage as there is a few more cells in series. The amps are close to 5.8.
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Old 09-01-2015, 21:06   #4
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Re: 24.9v 135w solar into pwm 12v system?

If your controller can handle higher voltage, you should not see any adverse effect, but you will not see any performance improvement either. For that you would have to replace your PWM with MPPT (which will convert higher voltage to higher current).
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Old 09-01-2015, 21:14   #5
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Re: 24.9v 135w solar into pwm 12v system?

Operation manual for PROSTAR PS 15 says max input voltage is 30V, you should be OK.
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Old 09-01-2015, 21:29   #6
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Re: 24.9v 135w solar into pwm 12v system?

Hate to say but it will not work, your PWM charge controller only switches the panel voltage on and off, it does not lower the voltage, You need a charge controller such as some of the more expensive MPPT charge controllers. If the Controller you have will accept the higher voltage you will not do any damage but will only get half the rated power as your battery will pull the module voltage down to battery voltage or 12? volts but the max current will not change. approx 5 amps at 12.5 volts is only 62 watts. You need a different charge controller or 12 volt (16 - 18 volt) solar panel to use with your existing controller.
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Old 09-01-2015, 23:15   #7
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Re: 24.9v 135w solar into pwm 12v system?

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Originally Posted by BambooSailor View Post
Operation manual for PROSTAR PS 15 says max input voltage is 30V, you should be OK.
If this is correct the 135w panel will damage the regulator and should not be used.

If the Vmp is 24.9v the Voc will be around 31v. Panels can occasionally exceed their Voc so you need a controller that is rated to around 35-40v (or higher) to be safely used with this panel.

Unlike Max current where most regulators/controllers can self protect, if the conrtollers maximium voltage is exceeded even very briefly it will be damaged.

There will be no, or virtually no, gain in output from the larger panel with the extra 35w with a PWM controller anyway. The panel will be physically bigger. The 100w panel is the only choice unless you update the controller.
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Old 09-01-2015, 23:33   #8
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Re: 24.9v 135w solar into pwm 12v system?

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Hate to say but it will not work, your PWM charge controller only switches the panel voltage on and off, it does not lower the voltage,
If the PWM controller was rated to a high enough voltage it could be used with higher voltage panels without any risk of damage to the battery or panels.

Higher voltage panels can even be directly connected to the battery in an emergency if your controler fails. The battery will limit the system voltage.

Without a controller you need to manually disconect the panels from the battery as the battery becomes charged, and the voltage level rises above the absorption voltage (usually about 14.6v). If you don't do this the battery will be damaged, but it is a good trick to get you out of trouble if your controller fails. Without the voltage conversion of the MPPT the output will be less, but you will at least get some power.
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Old 10-01-2015, 10:18   #9
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Re: 24.9v 135w solar into pwm 12v system?

Thanks for the input. I will stick with the 100w panel. Just wanted to check.
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