Would be interesting if knowledgeable cruisers could weigh in on these comments from Quora by industry experts. My so called inefficient PWM is via a company that has been in the industry for about 30 years and has an efficiency of 98.5% but the argument appears to be I have used an inefficient system. Appologies if this method of quoting is not appropriate.
, 25 years in the PV industry, PV system designer
and PV system integrator.
The most efficient solar
charging is only obtained when the solar panel, open circuit voltage, (Voc) is matched to the battery voltage. Most people do not know this, so they have to use PWM or MPPT chargers to correct the mismatch and both cause losses in charging.
To charge a 12 volt, Lead acid battery, the Voc of the solar panel has to be between 21Voc and 24Voc. This will charge the battery very efficiently with no losses. Make sure the solar panel maximum amps is no more than 25% of the battery capacity to avoid losses from charging too fast. Use an analogue charger
to avoid the MPPT and PWM losses.
PWM stops the battery from over charging by switching off the current to the battery between pulses of power. The solar panel is still producing power during the off pulse but this power is lost
completely if it does not reach the battery, causing a very inefficient charging. The current from the solar panel varies all day long from zero to maximum current, which only occurs at mid day. Also most PWM chargers use a 24 hour battery charging regime, which is obviously useless when a solar panel only works a few hours a day and gives very low current on rainy days to zero current at night. Losses vary with weather
conditions so I don’t have an average loss.
MPPT should never be used for charging batteries
but since most people use the wrong voltage solar panel, there is no choice but to use the MPPT to correct the mismatch and get a working system. Average 12% losses occur with MPPT chargers, compared to using the correct voltage solar panels
Always use the correct Voc for your battery with a good analogue charger
to prevent losses from MPPT or PWM chargers.
, Have had grid-tied PV since 1999, long before it became fashionable
Because the MPPT is somewhat more complex than the PWM controller, the efficiency of the controller
may be somewhat lower. But efficiency depends more on engineering choices like the switching transistors used, transformer/inductor design, switching frequency and especially the output current. (Efficiency usually peaks at some particular current and falls off below and above that value.)
I think you’re really
after the overall efficiency with which the system converts sunlight to electrical
power. Again, it depends. What is the panel’s peak power point voltage in relation to the required output (e.g., battery) voltage?
If they are already closely matched, a MPPT may not be much better than a PWM controller.
But a panel’s peak power point voltage increases with decreasing temperature, so a MPPT may provide considerable benefit during a cold winter. Also, if you’re discharging your battery at night (as in an off-grid system), its terminal voltage will be relatively low when the sun rises, and a MPPT will provide greater benefits.
Another situation where a MPPT can really help is when an array is partly shaded. Panels include bypass diodes to shunt current around them when they’re shaded. This is primarily a safety mechanism (a panel could conceivably burn up otherwise) but it also lets the array continue to produce reduced power at a lower voltage. If this voltage is below the required output voltage with a PWM controller, you’ll get essentially nothing. A MPPT will adjust to the lower voltage and get as much power out of the unshaded part of the array as possible.
An MPPT also makes it possible to operate the array at a much higher voltage than the required output, acting like a DC stepdown transformer. The resulting reduction in current in the array wiring
lets you use lighter and cheaper wiring and/or decrease wiring losses. With modern panels each typically producing 7 amps or more, and wire runs of tens of feet, this can actually be significant.
, works at Enertech
An Enertech MPPT controller enables the greatest capacity to be gathered. The nuts and bolts of an MPPT Solar Charge Controller
are to streamline the effectiveness of the charge controller utilized in a photovoltaic system.
PWM charge controllers are, basically, a switch that demonstrations between the sun based cluster and the battery and its capacity is to pull down the voltage of the exhibit to close to that of the battery to guarantee that the battery is legitimately charged. The PWM charge controller is reasonable for little frameworks.
MPPT framework is regularly utilized when the PV cluster voltage is generously higher than the battery voltage. It is the best answer to higher power frameworks.
, B.Sc. Electronics
& Physics, University of Edinburgh
You are confusing acronyms, PWM (pulse width modulation) is a technique used in power electronics
for multiple purposes, MPPT (maximum power-point tracking) is used in conjunction with PWM. Losses in PWM for DC/DC conversion on solar panels
will be single
To be fair I posted all the comments.