lorelec
Explorer
Joined 14 years ago
User Profile
User Widgets
All Activity
Re: mppt vs pwm
Salvo wrote: Your logic is nonsense. Not worth bring up. No one in their right mind will use a 72 cell panel in a 12V pwm system. The same rules apply when comparing 400W 36 cell panels using pwm and 400W 72 cell panels using mppt. The difference in gain will be on average only 5%. Higher voltage arrays are virtually all that are being installed anymore -- everyone's doing it. It's getting difficult to even find good 12v panels, at least at a price that's anywhere near the $/watt that you'd pay for higher voltage ones. Gains are MUCH greater than 5% when converting a higher voltage array to a lower voltage bank using an MPPT, versus what you would get with a direct connection or PWM controller. The latter is not even a consideration because the losses would be off the charts. Take a panel with these specs and charge a 12.6v battery with it: Pmax: 185 Watts @ STC Vmpp: 36.0 Volts Impp: 5.15 Amps Voc: 44.8 Volts Isc: 5.50 Amps With PWM (if you don't smoke your controller in the process) you'll have about 69 watts (12.6 * 5.5). With MPPT you'll have 185 watts (36 * 5.15). This is ignoring the effect temperature has, of course. The listed tempco of Pmax is -0.905watt/degC. So assume a 40degC temp rise over STC and you'll lose about 36 watts, which still leaves you with 149 watts. That's 215% of what you'd be getting with PWM. Where are you getting 5% from?231Views0likes0CommentsRe: mppt vs pwm
Salvo wrote: I see no real advantage when using a higher Vmp. Temperature still reduces power by the same amount. 90's thinking still apply. The difference between Vmp and battery voltage is directly proportional to the gain you would expect to see an MPPT controller provide. The greater the difference, the greater the advantage will be for MPPT over PWM. With the higher voltage arrays that are common now, the gain with MPPT could be several hundred percent or more over a direct connect/PWM scenario. The issue here, of course, is that connecting a higher voltage array directly to a lower voltage battery is going to drag the array's voltage down to that of the battery's. A 40v Vmp panel attached to a 12v battery, for example, is going to exhibit a loss in power that is several times lower than what it would be producing at its Vmp. Imagine a 100v array, or 400v array (as is now possible). The 17v Vmp --> 12v battery scenario is old news, and so is the talk of 10% gain (or 8%, if you like to nitpick). Time to let it go.347Views0likes0CommentsRe: mppt vs pwm
Salvo wrote: Right, Don needs to review that thread. I think Rogue dropped his gains after the discussion from 20% down to 8%; but it's been a while. No, it's entirely possible to get 20% gain with MPPT. Much more than that, actually, if you're using an array with a Vmp far above the battery voltage (which only MPPT controllers will allow you to do with any measure of efficiency). If you've been stuck in the boondocks for a long time, you might not realize that the popular thing to do these days is to use panels meant for grid-tie installations -- which do indeed have a higher Vmp than traditional panels meant for off-grid installs. For CONSISTENT gain, with an array that has a Vmp closer to the battery voltage (17v Vmp, for example, with a 12v battery), around 10% is typical when you factor in the effects of temperature on Vmp. This is 1990's thinking, though. Time to move on.273Views0likes0CommentsRe: New controller? Looks like it was added today.
mena661 wrote: PS - If you lose your job because someone else can do it better, just go find something else to do. The problem isn't that people in other countries can do it better, it's that they do it cheaper -- because either their standard of living is much lower than ours, or because they're being exploited...or both. Yes, that's capitalism for you. And it's self-defeating because left unchecked it will eventually drive down wages and standard of living for everyone except those involved in managerial work and some service-oriented jobs that haven't been outsourced yet. That's what the shift toward buying cheap Chinese goods is going to accomplish.448Views0likes0CommentsRe: New controller? Looks like it was added today.
Unyalli wrote: Almot wrote: Intronics and Rogue are probably the only two that are designed and made in the US. I sent an email to Midnight on this and here is the response. ... Although Robin of Midnite is wrong when he says, "No other major manufacturer builds their own circuit boards in the US or Canada or even in North America. They're all built offshore." Rogue builds their circuit boards in Oregon. All of the metalwork and final assembly is also done in Oregon. And Blue Sky, Apollo, Magnum, and Outback (some of their stuff) are "Made in the USA," although I don't know if they have their circuit boards made here. Usually "made" means assembled.448Views0likes0CommentsRe: New controller? Looks like it was added today.
Unyalli wrote: Rogue and Morningstar don't offer battery monitor so they're out. Blue sky is very limited on input voltage especially for an MPPT controller. Just saying it's not as revolutionary as Midnite would like to make you think. It's been done before.117Views0likes0CommentsRe: New controller? Looks like it was added today.
Unyalli wrote: lorelec wrote: Blue Sky has been doing this for a long time with various add-ons to their controllers Which add-ons? Their IPN Pro Remote, which also gives you remote monitoring...which the Kid doesn't even offer. Rogue MPT-3024/2024/3048 and Morningstar TS-MPPT all allow for remote monitoring.117Views0likes0CommentsRe: New controller? Looks like it was added today.
Unyalli wrote: Up until now this was all they knew. Don't forget the ending amps functionality as well. Blue Sky has been doing this for a long time with various add-ons to their controllers (and I think Apollo does, too). And many controllers have the capability of terminating the absorb stage by either time or net current. Rolls recommends timing the absorb stage, and include a calculation in their manual to determine length of time. So long as your battery can hold the absorb voltage for that length of time, you will be very close to 100% SOC. Or so the theory goes.117Views0likes0CommentsRe: New controller? Looks like it was added today.
The biggest catch with the Midnite Kid is that it derates above 25degC, so when things get hot, you're not going to get anywhere near 30A out of it. If you read the spec sheet it says, "Up to 30A amps battery output with low input voltage based off of PV configuration." In other words, the further your PV voltage gets from the battery voltage, the hotter the controller will get and the sooner it will current limit. I think there's been talk of adding a fan to it to keep it cooler. As with any product, research it thoroughly, ask questions, and understand what you're getting before you make your purchase. Also, just because a company is well-known does not mean that its products are flawless. Often it just means that they have more money, better marketing, and a bigger fan base. Again, some research before you purchase may provide some balance.117Views0likes0CommentsRe: Rogue MPPT, 490W and charging mysteries
BFL13 wrote: The controller itself is supposed to go near the batteries, so that often means out of sight from inside the rig. Some have remote displays to handle that when controller is out of sight. Others have the voltage sense wire to handle that too far from batteries issue so you can have the display on the controller inside. Routing the wires from inside to out where the batteries go is a big issue in some Rvs. Once all that is solved you have the temp comp issue where some controllers don't have theirs remoted, so the controller with the temp comp on it, has to go out of sight where the batteries are. So they have another wire for the remote temp so the controller can stay inside but now that wire needs a route. You have to really want to see the display if you want to put up with finding routes for all those wires and having the controller so far from the batteries. I went with the cheap controller out of sight, close to the batteries, and get my display info from the Trimetric mounted inside (it also has that wire routing problem though.) With the 3048, you can place wherever you want. There's remote battery temp sensing, remote battery voltage sensing, and a remote display if you need it. :) The 2024 requires a remote display if you want a display. It was designed to be installed out of the way, more typical of an RV application.357Views0likes0Comments
Groups
Travel Trailer Group
Prefer to camp in a travel trailer? You're not alone.Jan 21, 202544,030 Posts
