I have two ARCO M55 solar panels. What do I need to connect to a 12Volt bank of batteries.?
Question:
Answer:
You can buy "Solar Charger Regulators".
I don't.
These chargers limit the charging current to the batteries, so you do not get a full efficiency of the solar panel.
They disconnect the batteries from the user side (the bulbs you use) if the battery voltage goes below a certain level (i.e. below 8V for a 12V battery), so you cannot use all the power available in the batteries, even in emergency.
They introduce, at least, a 0.7V loss (diode forward voltage) between the panel and the battery.
If you have SEVERAL panels and a lot of batteries, use a controller as above.
If you only have one panel, insert a 5A trip fuse in line (in your case: twice the current of the panel), and a 10-20A diode in series between the panel and the batteries (Kathode side of the + of the battery, Anode side of the + of the panel).
Install a voltmeter across the battery.
The fuse will prevent any short or over-charge current.
The diode will prevent the battery to discharge into the panel at night if it is not already protected.
The voltmeter will allow you to "watch" the status.
Your thought of limiting the voltage is useless: should the battery be low, the panel will drop its voltage, limited by the max current.
Should the battery be fully charged and the solar panel at full efficiency, it will just try to charge the battery "more". A bit of bubbles may result, hence the voltmeter to watch over it.
If you want to limit the voltage to 14V, put a 14V Zener (14Vx2.5W!) in series with a resistor of, say, 17V-14V/2.5A or ~1 Ohm, 5W, in parallel with the panel.
ibiblio.org/pub/academic/envir... includes info that suggests the panels (actually called modules) are rated at 12 volts. At less than rated load they will put out a higher voltage, as you have seen.
Connecting the modules in parallel will give you the same voltage output.
Yes you would need something to regulate the output voltage. It will not be cheap.
Whatever you do, don't overcharge the batteries. If they are lead-acid batteries, then make sure the voltage doesn't exceed 14.7 volts, or whatever the datasheet spec says.
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