I would back off to two panels, until you can afford to get the additional controller. I doubt that the AN can handle it all without suffering an early death - and that's partly we're only in the middle of April, and there are much sunnier days ahead.
can you add more panels/watts to a mppt charge controller than its listed maximum for low light condition?
- Thread starter Go2Guy
- Start date
No, not a PWM (IMO). A "PWM' Controller cannot handle the VOLTAGE of his second pair (two in series with each other). He would have to re-wire in parallel AND he would be "throwing away" considerable power. A bit of math follows:
If his 2x2 array now "tunes in" at about 55 Volts V(mp), his panels likely have V(mp) around 26-28 Volts. Each. But his batteries only want to be charged at something less than 14.5V. In PWM Solar Charging, all the power which the panels offered at Voltage "higher than I want" is left behind, by very rapidly disconnecting and reconnecting the panel array. (So that the average Voltage, over a longer period such as 1/10 of second, is the desired battery charging Voltage).
500 Watts (the total "rated panel power" for the two panels), times 14.5V (the 'accepted' average Voltage), divided by 27V (the required Voltage for the Panels to actually deliver 500 Watts) yields only 268 Watts delivered into the batteries. (Under near-perfect Standard Test Conditions.) 230 watts is wasted via the "disconnected" portion of PWM time. That's 46% wasted, almost half.
And during non-optimal conditions (earlier and later in the day), the VOLTAGE doesn't change very much. It's mostly the CURRENT which goes down, and the amount of waste changes by only a little bit.
Per my previous post, I recommend that Go2Guy leave two panels unused, until he can acquire another MPPT. Maybe this one @ $171, although the Seller is only rated at 89.8% (which is not great, compared to other sellers): https://www.ebay.com/itm/Epever-40A...-Solar-Regulator-Tracer4215BN-CE/324027239727.
With another monitor tossed in the package, this guy would also be good (and I have bought from this guy): https://www.ebay.com/itm/Epever-MPP...0V-Controller-Meter-Tracer4215BN/142623868984
(I'd prefer to recommend a Victron Controller, but the pricing would be prohibitive for this buyer.)
Northernchateau
Solar Enthusiast
Whats the problem of putting the additional panel(s) on a contactor that disconnects them between say 10 and 2 or when ever you feel you will run over power? I am betting that it can also be done with a rasberry pi by setting panel wattage limits.
Although the Tracer "AN" would not be facing any change in Voltage, it would be facing an extremely sudden jump in current. (A lot more sudden than the changes which occur under 'party cloudy' skies.) Bit I love your idea! A rasberry pi, with a bit of programming and pretty big shunt, could do that. And slight variation of your idea is both cheap and easy:
From a 12v-powered timer relay, use another full-time "12V connection" as the switched load. Use that circuit to control a high-current automotive Relays, one on the "PV +" from the second panel pair and the other along the "PV -". (Although they're "12 Volt Relays", the switched POWER lugs are rated for 70V). The "kewl" little lamp indicator also tells you whether it is "on" or "off": https://www.amazon.com/Ehdis-Relay-Charge-Waterproof-Transparent/dp/B01JKU027Q/
With the 4-pin Relay you would set the timer to be active between about 11 AM (daylight time) and 3 PM. With a 5-pin relay, you could also attach the "PV +" into the NC connection (pin 87), and leave the switched pin (87a) unconnected. In that wiring design, the timer would be ACTIVE for 4 hours and pull in the coil (disconnecting the SCC on pin 30 from the "PV +" on pin 87 and connecting it to ... nothing at all.
This would be a good timer: https://www.amazon.com/FAVOLCANO-CN101-Digital-Programmable-Switch/dp/B012FSL2GK/
Northernchateau
Solar Enthusiast
Check out this relay heavy duty 80amp 12v relay
I use them to power big drag racing fuel pump and they handle the start up surge without any problem.
I also unplug my PV when I am working on the system the plug it back in when the sun is on it. Not sure how bad that is on a system but I am thinking if you do 1 panel at a time it should not be that bad.
Thanks for the nomination, but that's pulling really high coil current. It otherwise looks OK (although I didn't see any discussion of max switched Voltage). I prefer my 5-pin nomination, this one: https://www.amazon.com/Ehdis-Relay-Charge-Waterproof-Transparent/dp/B01JKU0730/. By using the 5-pin, the coil is only consuming power for 4 hours per day - to pull the Contactor AWAY from the "NC" Relay position.
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