12v MPPT and 24v MPPT vs 24v PWM Test
Got a chance to try out comparing amps to the battery using MPPT vs PWM on a 24v battery bank and comparing those with the usual MPPT on 12v with my 230w panel. The bank is four 6s, so it was easy ...
Forum Discussion
westend wrote:BFL13 wrote:westend wrote:
Amps to the battery with MPPT is whatever it comes out to be when you divide the output watts from the controller by battery voltage. Lower Vbatt, more amps. Higher Vbatt, fewer amps.
How are you establishing "...watts from controller..."?
My controller displays all at once, battery voltage, amps to the battery, and watts. The watts shown is the product of the other two. I have confirmed the displayed volts and amps separately with both Trimetric and multi-meter so I know the controller display is accurate. (The controller does not display input volts, amps, or watts)
I also measured the input volts and amps to the controller with a multi-meter to get the input watts. The output watts is about 5% less due to the controller efficiency being around 95% according to my results. (That 95% is with 24v panel and 12v battery)
I'm not disputing your test results, they are what they are. I'm just curious if your controller displays amps to battery, why do you have to do a mathematical conversion to establish amps to battery while using MPPT and not with PWM?
Sorry, I get the question now. I do not do a math conversion to get the amps, but am just pointing out that the output amps is what you get by dividing the output watts by the battery voltage of the moment. So the amps is sort of what is left over, not a direct amount you get like the watts and volts.
The controller display actually shows the "solar amps" to the rig, not all of which goes to the battery so I gave that the wrong name, but it makes no difference when calculating controller output watts.
The Trimetric only shows amps to the battery so you don't always see the same number as the solar display's amps which can be more at times. Inserting the multi-meter in the path as an ammeter alters the R on the path some, and could mess up the amps reading, so a clamp-on meter is an advantage, but I don't have one.
Both my MPPT controller and my PWM controller display the "amps to the rig" and the battery voltage. The MPPT controller also shows the output watts. The PWM one shows the volts and amps which you can multiply to get the watts.
