No controller to quick charge a battery

[mep1811]

In testing my 100 panel I see 6.34 AMPS from the controller going into my battery. Without the controller I see 9.44 AMPS. Quite the difference.

I was thinking under ,controlled conditions, charging my batteries directly from the panel at a higher amperage when they are very discharged. I would monitor the voltage periodically to ensure they don't overcharge.

Am I right in my assumption? Thanks

 

[dwh]

Can't comment on assumptions - not enough info. See amps how? Multi-meter inline? What voltages?

First describe exactly *why* there is a difference.

 

[mep1811]

I used a Fluke Multimeter. Voltage with the controller is 14.09 Voltage with 6.34 amps . Voltage from the panel is 19.22 with 9.44 amps.

 

[dwh]

You are measuring from the solar panel, through the meter and back to the panel, so you are seeing 19v and 9a - by bypassing the battery.

But there is no chance the battery is actually seeing 19v...so it won't be seeing 9a either.

Measuring a charging loop at different points (thus bypassing various sections of the loop) will result in different readings.

But only the readings taken at the battery are valid. All the rest are just different ways to "be wrong, with confidence".

 

[dwh]

When a solar panel is connected to a battery directly, the panel operates at battery voltage.

Even if you bypass the battery and see 19v at the panel, that has nothing to do with what is happening over on that other loop where the battery is.

So if the battery is at 14v and the solar panel is directly connected, the panel is limited to operating at 14v. That is not the optimum operating voltage (Vmp), so it does not produce max power - only 6a in your test.

Bypass the battery and you get to see what the *potential* of the panel is - 9a. Well, it would be 9a if it were allowed to run at its optimum voltage.

But that would overcharge the battery, so you add a charge controller to make sure the battery voltage never reaches 19v. Of course the problem is that the solar panel will never operate at 19v either, so it will never produce its full rated output because it never actually operates at Vmp.


MPPT was invented to solve that problem.

 

[dwh]

MPPT splits the charging circuit into two separate loops - solar loop and battery loop.

By doing that, the solar can be allowed to run at optimum voltage (Vmp) without being limited by the battery. Then the solar side voltage gets down converted to battery voltage on the battery side loop.

So you end up getting both full power out of the solar, and the most amps into the battery - by operating the two separate loops each at its most efficient voltage.

 

[jonyjoe101]

6.34 amps is good for your 100 watt panel. 6.34 amps x 14.09 volts gets you 89 watts. You never going to get the full 100 watts, you only get that at the factory where they test the panel using special gear and methods.
If you took the 9.44 amps x 14.09 you would get 133 watts, which is more than your panel is rated, even mppt won't give you more than what the panel is rated, but it will get you close.