Solbian solar math?

[Skipper]

My Chinese 100w panel puts out 17.8v. The Genasun 140w controller pipes it down to 13.6+, for about 7.35 amps max charging.
However, a Solbian panel I'm looking at for additional installation is rated at 60w, but only 7.1v.
Does a Genasun 65w MPPT controller transform it up to 13.6+ volts?
So it has high current, around 8.5a, at the panel but the controller brings it down to 4.4a at 13.6+ volts for charging?

Is there a minimum input voltage that the controller can handle? There's nothing in the specs, only max voltage and min battery voltage, not any min panel voltage.
Or does it go by max amps? The 65w controller manual says 5 amps max, but is that out or in?

How many question marks is that?
:-D
Found nada on Google.

 

[dlochner]

Is the panel you're looking at the SXp60?

I don't think the Genasun controller can raise the voltage. If it could do that, then the amperage would be decreased, but the wattage would remain the same. It's that old Ohm's law business.

You might be able to put 2 of the Solbian's in series, that would double the voltage with the amperage remaining constant. Series circuits add voltage with constant amperage, parallel circuits adds amperage with constant voltage.

Have you contacted either company's tech support?

 

[walt]

According to the Genasun GV 5 manual, it says the input (solar) voltage range is 0 to 27 volts. Does that mean it will convert the 7.1 volts panel power to battery power.. dont know but seems the manual would imply it does but seems odd to me.

However, a lot of MPPT controllers require the panel voltage to be a little higher than the battery voltage. I have a Victron MPPT controller that doesnt even turn on until the panel voltage is something like 5 volts above the battery voltage and even after turn on, the panel voltage still needs to be somewhat above battery voltage.

You have the conversion correct where the MPPT controller preserves power (V*I) from input to output (with a small conversion loss). So for the low voltage panel, the current in the wires between the panel and the controller is HIGHER than for a higher voltage panel of the same power. Power loss in wires is proportional to the square of current (ie, I*I) so in order to keep the wire diameter as small as possible, you are better off with higher voltage panels. Try running the numbers for the wire gauge in the run from the panel to the controller for the low voltage panel vs the higher voltage panel and you can see for yourself.

 

[Bob J.]

Genasun does has a "boost" mppt controller that takes a lower voltage & boosts it to higher voltage but that's not what you have. The problem is the amp output gets reduced in the conversion with a boost controller as Dave mentioned.
Why not bag the the Soliban & get another panel with a nominal 12 volt output?
Just need to be sure your existing controller can handle the voltage/amperage.

 

[Skipper]

Is the panel you're looking at the SXp60?

I don't think the Genasun controller can raise the voltage. If it could do that, then the amperage would be decreased, but the wattage would remain the same. It's that old Ohm's law business.

You might be able to put 2 of the Solbian's in series, that would double the voltage with the amperage remaining constant. Series circuits add voltage with constant amperage, parallel circuits adds amperage with constant voltage.

Have you contacted either company's tech support?

Yes, SXP60. Haven't bought it yet. Researching.
I thought maybe they assumed a person would connect in series, but that means I'd have to buy 2 panels
:-|
Makes no sense.
My goal is to get at least one impervious panel, and to up my power to surplus capacity (from 100w now to 100+60w, with independent controllers for each panel delivering to independant switchable batts) in the event of cloudy days, periodical larger power use, etc.
My Chinese Grape Solar has had no problems, and runs the boat to fully charged by 2:00pm in summer SoCal sun when cruising or anchored (otherwise I'm on shorepower and panel is stowed below), but I've read about bubbling and shorting in the version I have. Maybe I have a good one; who knows.
If I have to spend $700 on Solbian, I'll make do with the Grape, and maybe add a 50w Grape flex for $155. I think they worked out the bugs on them. Still, if could get a Solbian 60w for $320, would opt for that.

I haven't contacted Solbian. I contacted SBO Global Boat Support

 

[Skipper]

According to the Genasun GV 5 manual, it says the input (solar) voltage range is 0 to 27 volts. Does that mean it will convert the 7.1 volts panel power to battery power.. dont know but seems the manual would imply it does but seems odd to me.

However, a lot of MPPT controllers require the panel voltage to be a little higher than the battery voltage. I have a Victron MPPT controller that doesnt even turn on until the panel voltage is something like 5 volts above the battery voltage and even after turn on, the panel voltage still needs to be somewhat above battery voltage.

You have the conversion correct where the MPPT controller preserves power (V*I) from input to output (with a small conversion loss). So for the low voltage panel, the current in the wires between the panel and the controller is HIGHER than for a higher voltage panel of the same power. Power loss in wires is proportional to the square of current (ie, I*I) so in order to keep the wire diameter as small as possible, you are better off with higher voltage panels. Try running the numbers for the wire gauge in the run from the panel to the controller for the low voltage panel vs the higher voltage panel and you can see for yourself.

My thinking as well.

 

[Skipper]

Why not bag the the Soliban & get another panel with a nominal 12 volt output?
.

Might have to.

 

[Bill Roosa]

I'm sure that the manual would indicate a "boost" capability if it had one. That is electronically possible (boost/buck converter)+(mpp controller) but those use a DC to AC to DC type conversion and are pretty noisy around radios as the frequency jumps all over the place and you can't apply the normal capacitor/inductor filters to that type of circuit and still have it work correctly. Every one of these I've researched is a buck (down) converter+mpp which require a voltage higher than the battery operating voltage to work.

 

[Maine Sail]

The small Solbians require a Genasun boost controller such as the GVB-8... The B=Boost....

 

[Brian D]

To me, that panel seems like nothing more that a cell phone solar charger. Capable of charging 4 phones (2000mah/phone). That is just me reading the specs. That 7.1v would drop to 5v under load.