mydesolar avatar image
mydesolar asked

75/15, 100/20 Which for my first sytems Please help


I currently have 2 100 watt solar panels new from Ecoflow, 2-12v 100 ah new batteries from Redodo that I wasnt to use as a 24v 100ah setup. I would like to expland the solar in the future depending on finding cheap panels. This system would be a basic off grid used on a cart at home to power basic items, maybe a fridge in a power outage. Please tell me which solar charge controller and wire size.

I will be using this for a lot of usb charging, lighting and hopefully many other items.

Thank you for your help in advance

charge controller compatibility
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matthias-nagel avatar image matthias-nagel commented ·
The wire size depends on several factors. The current rating which in turn depends on the type of installation, the ambient temperature, insulation material, etc., and the voltage loss. For a rough overview which wire size is rated for what current, see the manual "Wiring Unlimited". But please be aware that this guideline is not a substitute for a professional, licensed electrician. Depending on your jurisdiction there are a lot more criteria for choosing the right wire. Not every kind o wire (in particular insulation material) must be used in every environment. Regarding the voltage loss: I usually try to stay below 3% total loss for the entire installation (i.e. from power creation at the PV panel to the power consumption at the load) and below 1% for a single connection. The voltage loss depends on the material of the wire, its diameter and the *length*. Hence, without details about your installation, there is no definite answer to your question.

Judging from your question, I really recommend you to talk to a dealer and/or a professional installer. This forum isn't really the right place to ask such broad questions.

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Mike Dorsett answered ·

If you are looking to expand the solar system in the future, using cheap panels, then you are unlikely to get modules that are compatible (string wise) in terms of voltage or current.(strings with matched voltages only can be connected in parallel). Also if array orientation changes by more than 5 degrees, then a separate tracker is required. So I think the best solution would be to go for the smallest tracker (MPPT unit) that matches you current modules, and then add another MPPT when you get more modules.

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mydesolar avatar image mydesolar commented ·

Great advice. What wire size would you recomend? Ive been racking my brain going over every detail. I can't wait to get it up and running. Any recommendations for a step down converter, wire and cut off switches? Thank you

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