Various threads exist here to debate the pros and cons. Note that for small systems under 200 watts, it may make more sense financially to just buy more panel power, than to spring for a costly mppt controller. Click here to go to FVP VoltEdge M24-930ST Starting Marine Battery detail. Pwm or mppt controller choice is up to you. FVP VoltEdge M27-7DC Deep Cycle Marine & RV Battery. However this best-case scenario has some built-in headroom to keep the system from being on the edge spec-wise. This doesn't take into account real-world losses as mentioned above, like from PWM controllers. Pretty close to what they spec.īut you always buy a bit more amperage capability than the panel, so if it were me, I'd choose either a 10A controller, or maybe 15A unit. For quick calculations, just use 18v.ġ40 watts / 18 volts = 7.77 amps. 24M 650 CCA - BAT 8305 online from NAPA Auto Parts Stores. If you say buy a grid tie 60 cell panel which will be about 1/2 the cost of the 140W 12V panel the pwm losses get worse.įor example, in a small system with a 140 watt 12 volt panel, with specs that say it hits about 7.9 amps, is the current flowing through the controller to the battery that 7.9 amps, or is it 140/12, or about 11 amps.Close - you just divide the panels rated wattage, by it's ocv rating, typically in a 12v-nominal system that will be anywhere from 17-21v. Buy NAPA Marine Starting Battery 12 Months Free Replacement BCI No. Same panel with MPPT controller 140/12=11.66 int the battery. Vmp of that panel is about 18V and amps about 7.7 amps into your battery with a PWM controller You will lose approx 30% of the power of the panel with this type of controller With MPPT amps to the battery is W/battery voltage. TimThat will depend on the voltage of the battery and type of controller. Pardon my probably dumb question but I'm getting hung up on this. If you want to hit the sweet spot of a c/10 rate, where the current is equal to the amp hours divided by 10, how do you actually determine the current?ĭo you take the wattage of the panel and divide by battery voltage, or do you take the amps as provided by the panel specs?įor example, in a small system with a 140 watt 12 volt panel, with specs that say it hits about 7.9 amps, is the current flowing through the controller to the battery that 7.9 amps, or is it 140/12, or about 11 amps? Thanks for the good information and advice.Īn additional question I have is choosing the correct sized controller for a battery.
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