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Replacing an inefficient Zamp solar kit with a Overland kit

Zamp solar kit Overland solar kit 6 volt batteries

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#51 Vic Harder

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Posted 02 June 2019 - 06:28 PM

Kent, flexible panels tend to be much more expensive (at least up here in Canada).

275w is still very nice. i have 265 and am looking at 42w of power going into my batteries right now. my 130l truckfridge also has not been off since installed 30 months ago
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#52 pvstoy

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Posted 03 June 2019 - 01:35 AM

I do have 3 (three) Overland Solar 160 watt panels on my roof for 480 watts. Yes they are more expensive, but... I like them.

 

I have noticed in rain that the battery is still being charged.  I run them in parallel as the voltage I normal see is 28 volts.  That is enough head room when it is cloudy and raining when less voltage is being produced to still produce some charging. Above 19 volts  the MPPT charger can make something out of.  But if your panel caps out at 20 volts when it is cloudy or raining it is not giving your controller much to make anything in return as it might be putting out 12-15 volts.

 

If I had multiple panels that were around 18-22 volts I would have wired them up in Serial to increase the voltage and sacrifice amps, this would do much better in low light conditions.

 

I have found these panels have been working out really good and have yet to use the trucks alternator to do any help charging.  I do have the very inefficient Dometic 130 liter DC refrigerator.  But I really like the large freezer space.


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Patrick

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#53 GeezerMike

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Posted 15 February 2020 - 02:41 PM

Here is a piece of information about a Zamp solar setup that is implied, but it is not stated directly.

A Zamp PWM Charge controller combined with a 160 watt Overland solar panel only puts out 80 watts on a perfect day. Replace that (or any) PWM charge controller with an MPPT charge controller and it will allow the solar panel to produce 160 watts.

A solar panel on a perfect day pointed directly at the sun at that time is a variable power generator from 0watts to Max watts dependent on the voltage it is connected to. As an example, for maximum power, the Overland 160watt panel needs to be held at 27.3 volts to produce its maximum power (Vmp in specs). A Zamp (or any) PWM charge controller holds the panel at battery voltage, roughly between 12 and 13 volts, or roughly half the voltage needed by the Overland 160 to produce 160 watts.

The way to calculate the wild-asp maximum output of a solar panel using a PWM charge controlker is to multiply the maximum current output of the solar panel (Isc) which for the Overland 160 watt is 6.27 amps (generous) and multiply that by the battery voltage (I’ll use a generous 13volts), which results in 81.47 watts output max(no way it will get that high).

An MPPT charge controller can get more power out of a solar panel by using an expensive internal DC-to-DC converter to increase the voltage seen by the solar panel to hold the solar panel at maximum power voltage (Vmp) which results in maximum power amps (Imp). For the Overland 160 watt panel, Vmp=27.3 volts, and Imp=5.86 amps, to get watts 27.3x5.86=163 watts.

When do you use an PWM controller? When your panel maximum power voltage is close to 13volts like tiny foldable portable panels. OR you are very very very poor - MPPT controllers are a lot more expensive than PWM. You can get a good PWM for $25. A good value MPPT will cost $80, but $180++ is more realistic.

I have read here about some setups and recommendations that show a good understanding. I only wanted to put in some practical context.
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