can you add more panels/watts to a mppt charge controller than its listed maximum for low light condition?

[Go2Guy]

For example i am using a tracer 40a at 12v mppt,. Its listed maxium is 500 watts at 12 v, i currently own 4 250w panels. if i hooked 2 panels ie 500 watts I get 250-300 watts until its high noon than i get about 450 watts, at arround 9am i only get about 200 watts, however for testing purposes I hooked up all 4 250w panels [1000w] and i was getting close to 400 watts at 9am!!!!!, I obviously was not over loading it because it was not at full sun. . . and i was with in the rating of the unit.

so back to the million dollar question, is there a way to keep a 1000 watts hooked up at all times and have the unit self regulate it down to its maxium of 500 watts that way i get full power all day as opposed to only for a couple hours during high noon . . .I have heard of a couple controllers doing this[cant remember which ones,] its seems counter intuitive to not do this. . .why run only 500 watts of panels and get full power only 2-3 hours a day when i can run 1000w and get close to full power[500w] all day [presuming the unit self regulates] . Is there a way to safely do this?

 

[Ampster]

Over paneling or high DC to AC ratios are common tactics used in string inverters. Some string inverters are tolerant of ratios as high as 1.50 to 1, however it is still important to remain within the current and voltage limits of the inverter. The same is true of charge controllers. The tricky part is estimating those potential panel outputs. It is counter intuitive but there is more danger of over voltage on cold clear days. Too high voltage can kill components designed for lower voltage even though the Amperage is fine. Similarly too high a current can fry connections when voltage is okay.
The way to safely do overpaneling is to carefully calculate those values using the panel specs and the given string configuration and compare them to the limits of the charge controller.

 

[Alphacarina]

The safe way to do what you want is to buy a second Tracer 40 amp MPPT and have two systems charging your batteries - Cost is around $200, which is the same as replacing your current controller after you burn it up experimenting with how grossly you can overload it before it fries

Don

 

[GXMnow]

And maybe I will beat Hedges to this one. You can also have panels at different angles to make maximum power for more time of the day without exceeding the peak power limits. If you parallel a string that is facing 30 degrees east with another string facing 30 degrees west, they will only peak up to about 20% more than one string faced directly at solar noon. But now you have more power for 2 to 3 hours longer in the day. If you have no shading issues in the early morning and evening, you can push it even further. But you do still need to be careful with the input limits of the charge controller. Check the specs carefully. The voltage is always the big no no. Be sure to leave a 20% margin incase of that freak cold wave. On the current side, many better charge controllers can accept a fair amount of over panelling and will just go into current limit at their output. 25% to 50% over panel is safe on many units, but if your battery bank can take the extra charge current, the second charge controller is not a bad idea. With a grid tie inverter, going over panel make much more sense. In my case, I am limited to back feeding just 16 amps to my breaker panel. By over panelling my inverters 25%, I get 25% more power whenever there is less sun than my inverters can convert. There are only a few days where it is sunny enough and cold enough to see my inverters hit their limit. On my near perfect day, I did see them clip at the full 16 amps for about 3 hours. If I had used inverters that would convert the full power, I would have hit nearly 18 amps at solar noon. This is why it is far more common to over panel in a grid tie system, not so much when you are charging batteries. Just make sure you do not exceed safe charging rates.

 

[rickst29]

Depending on the particular model of EpEver Tracer which you have (the "BN"s are quite good, the "AN"s are very bad) .... It might not be at all damaging to over-panel the SCC. But there is also the question of wasted opportunity - can your battery bank and consuming appliances make use of the extra power which the panels COULD provide, between "11 AM" and "2 PM"?

If you can't use the extra power, and you have a Tracer "BN" - you can leave it alone, it will NOT "blow up" when over-paneled by a ratio of 2:1. On my own RV, I have my Tracer "BN" over-paneled by about 20%, but some poeople have gone much higher than that.

In the case of any other Tracer (except the "BN" and the "Trion" - or in the case of being able to actually use additional power into the (RV, Trailer, whatever) - just add another SCC. Even with models which aren't installed on a master/slave control bus, they don't confuse each other too badly during most of "Bulk Mode" charging: They only begin to confuse each other when approaching their decision to "fall back" into Float Mode.

That behavior has been tested and confirmed, BTW.

 

[Ampster]

...... It might not be at all damaging to overpanel the SCC. ......
That behavior has been tested and confirmed, BTW.

The way i undrrstand it, Watts are not the issue as much as the specifics of volts and current. @GXMnow explains this in detail above. What were the limits that you were dealing with in Amps and Volts? Good to know some models are more tolerant than others.
My knowledge is primarily from string inverters but the concept carries over. I don't know which charge controllers offer the greatest opportunity so your experience is valuable.

 

[rickst29]

The way i undrrstand it, Watts are not the issue as much as the specifics of volts and current. What were the limits that you were dealing with in Amps and Volts? Good to know some models are more tolerant than others.
My knowledge is primarily from string inverters but the concept carries over. I don't know which charge controllers offer the greatest opportunity so your experience is valuable.

Yes, the manner of his hookup is important. I'm exactly with 'GXMNow', in recommending that Max-PV Voltage (the sum of series-connected panels V(oc)) be held to less than 80% of the maximum rating on the SCC. Within that limitation, however, it becomes a question of power:

Available "Panel Power" which WON'T be sent into the batteries, and isn't consumed as "operating overhead" (i.e., "waste heat") within the SCC must be rejected as input on the PV terminals of the SCC. There are basically two ways in which MPPT controllers can do that:

1. The can switch in to "PWM", leaving the panels MOSTLY disconnected (and wasting panel power) during each ongoing second; and
2. They can intentionally move the Panel Operating Voltage a far distance from V(mp), to a Voltage where the panels don't generate much power.

Some SCC Controller solve the "problem" in both ways. Keep in mind that when the battery bank is nearly full, and accepting only very low current at "Float" Voltage, the SCC must always do that exact same job - leave all of that unwanted power unused, "wasting away" within the Panel Array. Even when the Array is configured at exactly 1.0 of the SCC maximum power capability ("Bulk" charging Voltage * maximum output Watts), the SCC must leave the unwanted power in the Array, whenever the batteries shouldn't be taking it (due to high SOC) or are simply unwilling to take it (due to high resistance).

If you have a residential string Inverter with a fairly "big" battery bank off-grid, your residential SCC must do the same job. With no Grid connection to dump "extra power" into a nearly unlimited "240-VAC battery", your SCC must reject the Solar Array offer of unwanted "input power" when the battery string is "full" (and there are no 120/240V consumers of electric power to use it).

 

[dr.diesel]

I have a touch over 5000 watts of solar on a Victron 250/100 at a 24v battery voltage, almost 2x over paneled.

I can't comment on the Tracer charge controllers but high quality stuff like Victron will limit itself accordingly.

 

[Go2Guy]

wow guys thanks for all the responses i greatly appreciate it. . . I kinda took a leap of faith and tried it, its just about full sun and i was getting about 390-410 watts, I tried hooking a 3rd panel in a string it was a 98 volts open circuit, , this unit supposed to be rated for a 100v, well it errored and gave an over voltage error, so i went full monty and hooked up all 4, 2 panels per string , for a total of a 1000 watts, extrapolating the numbers its likely about 800-850 watts of true power. . wasnt sure if i was gonna see a puff of smoke. BUT IT DIDNT!!!! it is surprisnly handling the loads, and keeping it right arround 40 amps, at 12v, sometimes it goes a little higher to about 41 . i will say the unit is running a tad hot, not to bad, my guess would be about 115-125 degrees . the real question is would it hold up long term, I wonder if there is a current limiting circuit I could put inline to run it like this full time but with out damaging the unit. would be nice to get a solid 40amp from sun rise to sun down. . .

4

 

[rickst29]

Yes, it will hold up just fine. I will presume your controller to be Tracer "BN4215" (because you've got an MT-50 monitor/programming panel). That can handle "1200 Watts" of PV panels, rated at STC, pretty easily. That's actually a "150 Volt" SCC. Are you sure that your SCC is only a 100 Volt model - and what is it? (I'd love to see a picture of the OTHER end of the MT-50 ethernet cable, hint-hint-hint. )

Your "full current" at low Voltage implies LFP batteries. As they become more charged (with a bit more internal resistance), Your controller might be putting more POWER into the batteries at slightly higher VOLTAGE. But, as long as your batteries reach full charge before around 2PM (daylight time) on days with "excellent sunshine", I recommend that you not change anything. If your batteries aren't rnearing 100% SOC by that time of day, then I'd recommend another Tracer - just run 'em in parallel, with dual MT-50s as monitors.

 

[Go2Guy]

so i just confirmed i actually do have the AN model . . . its the tracer 4210AN right now its 2, 250w panels in a string, and then when i connected the other 2 it was in a string so it was 2x2 , you saying the AN is a bad scared the crap out of me , not litterly lol but is deffinitley disheartening. ., I tested it and it worked, BUT that definitley does not mean it will hold up, I just wish there would be a way to get its rated current all day but with out frying it, it seem silly to get 34 amps out of a 40 amp rated controller for only 2-3 hours a day when you over panel it and get 40 amps out of it almost from sunrise to sun set. . . .


I like what, GXMnow said when he said point one string , east and one string west, and you will get sort of the same effect but with out over loaing the controller to much. is there a circuit that i can get to limit the input current to the device, so i can run it full power saftley all day?

 

[pollenface]

The safe way to do what you want is to buy a second Tracer 40 amp MPPT and have two systems charging your batteries - Cost is around $200, which is the same as replacing your current controller after you burn it up experimenting with how grossly you can overload it before it fries

Don

best way, in my opinion.

but epever does specify a maximum pv array of 1.5x (780w for 12v/40a).

 

[Go2Guy]

best way, in my opinion.

but epever does specify a maximum pv array of 1.5x (780w for 12v/40a).

Thanks pollen face, didnt not know that, every where i read it says 520 max, but that leads us to our second problem , when these panel companies list power outputs we all know we never get that, its ussualy 70-85% of the listed panel output, so when a charge controller company says 520 max, or 780w max does that mean solar panel advertised number OR does it mean true world out put. . . if it is true world out put, thats good news for me because I was getting about 380-420 watts per string of 2 250w panels so with 2 strings of 2 250w [2s 2p] that should net me 760w-880w real world power which matches your 780w number decently

 

[Ampster]

so when a charge controller company says 520 max, or 780w max does that mean solar panel advertised number OR does it mean true world out put.

As explained up thread, the critical numbers are the maximum voltage and the maximum current. The Watts number is just a calculation. The design has to consider that one cold day that the panels could put out more than the STC numbers.

 

[fratermus]

you saying the AN is a bad scared the crap out of me , not litterly lol but is deffinitley disheartening

The A-series is fine. I have used both the A- and BN-series in harsh duty for years, including substantial overpaneling. I've seen the A pinned to rated output for hours without getting more than a few degrees above ambient according to the temp gun.

The chief spec differences between A/B is the 100v/150v voltage limit and 1.5x/3x overpaneling max (if I am reading the manuals correctly). Most people will not approach either limit, in which case the older A-series will usually do the job at a lower price and with benefit of a built-in display. There is some speculation that the MPPT algo in the A-series is slightly better (less likely to get "stuck" in weird light conditions). I haven't observed stuckness in either controller in my use.

Both the A- and B-series work with the MT50.

it was a 98 volts open circuit,

I wouldn't repeat that experiment. You can seriously overpanel the epever with wild abandon but overvoltage can lead to quick damage. I agree with the 80% of voltage max crowd.

 

[fratermus]

Thanks pollen face, didnt not know that, every where i read it says 520 max,

from page 9 of the manual:

"...in the practical application, the maximum power of PV array shall be not greater than 1.5 x the rated charging power of controller"

Note that max voltage limits are decreased both during overpaneling and in hotter ambient conditions.

 

[squowse]

The safe way to do what you want is to buy a second Tracer 40 amp MPPT and have two systems charging your batteries - Cost is around $200, which is the same as replacing your current controller after you burn it up experimenting with how grossly you can overload it before it fries

Don

Why would it burn up? As long as the voltage limits are respected, the mppt is more than capable of opening/closing the gate to control the current.

 

[GXMnow]

Why would it burn up? As long as the voltage limits are respected, the mppt is more than capable of opening/closing the gate to control the current.

The problem on some MPPT controllers is the way the MPP search algorithm works. On many of the cheaper units, they slowly increase current draw then monitor the voltage and calculate the power. If the power went up, it increase the current again then checks the voltage etc. At some point, the increase in current will cause more voltage drop and then the power actually drops. Then it backs off the current to the discovered "Maximum Power Point". During this search time, there is a chance the maximum power might be exceeded. If it happens for a few seconds, it is probably not a big deal, it dials back the current to what the controller can handle. As long as the solar can't produce more than 1.5 times the constant rating, the search system and current limit are quick enough to protect the device. But if you have far too much solar coming in, the step size of the search might pull enough power to fry the DC to DC converter electronics. If the unit has a very fast search and test routine, it will be able to handle more over current without damage. If they built it to handle more current, it would be sold as a more powerful unit. The cheaper the unit, the less over head it can handle, for even a few seconds. A very high quality unit, can probably take 200% for a bit as it finds the the limits, and then dials back to the set battery current or the device long term limit.

 

[rickst29]

Thanks pollen face, didnt not know that, every where i read it says 520 max, but that leads us to our second problem , when these panel companies list power outputs we all know we never get that, its ussualy 70-85% of the listed panel output, so when a charge controller company says 520 max, or 780w max does that mean solar panel advertised number OR does it mean true world out put. . . if it is true world out put, thats good news for me because I was getting about 380-420 watts per string of 2 250w panels so with 2 strings of 2 250w [2s 2p] that should net me 760w-880w real world power which matches your 780w number decently

They are advertised at "Standard Test Conditions", which means extremely bright sunlight under moderate temperatures. If your panels are rated honestly (and many are not), then you should size for the rated output - because someday in June, the sunlight will be perfect. The "BN" can happily ignore "extra power" up to almost 3x of its maximum power handling - but I don't know exactly how bad the "AN" controllers are. My only Tracer experience is with "BN and "Trion". There seem to be a lot of problem reports about the "AN" series within this forum, especially regarding the new "big" ones.

 

[Go2Guy]

They are advertised at "Standard Test Conditions", which means extremely bright sunlight under moderate temperatures. If your panels are rated honestly (and many are not), then you should size for the rated output - because someday in June, the sunlight will be perfect. The "BN" can happily ignore "extra power" up to almost 3x of its maximum power handling - but I don't know exactly how bad the "AN" controllers are. My only Tracer experience is with "BN and "Trion". There seem to be a lot of problem reports about the "AN" series within this forum, especially regarding the new "big" ones.

on a 20 foot cord to 12 awg cord from panel to mppt i got a max of 445 watts a couple weeks ago on hot and dry panels. now i am on a 150foot 10awg cord and am peaking at about 420 with wet panels, but its averaging 380-390 watts, [ 50v 7.8 amps] , 10awg is rated for 30 amps but i guess because its such a long run, i am still getting line loss. today during test, sunlight was absolutley perfect, [ i am brown skinned and ussualy never burn in the FL sun BUT today just being out there from 10a-12a i burnt my shoulders, this litterly only the second time in my entire life that i got sun burn . so i take it with the sun being so dam perfect with I will not exceed about 400 watts off of 2 250 watt panels. . .
the problem is:
I cant wire 3 in series as it will over voltage and
- if run 2 250 panels, I average 250 watts during non peak with 380 during peak hours only[3-4hours] OR
- if I run 4 250w panels [2s 2p] that brings me to [380x2] 760w-820w [410x2] max that is a little over 1.5x . . . and im running it hard

do you think that will be okay. At this point it seems i really should of got the BN because then i could off wired 3 in series and it would been perfect also it supports that 3x over paneling. . . it definitley does run hot with 4 panels hooked up, they say a human can handle 140F for no more than 5 seconds, with that in mind i would guess it was at 130 degrees, this kinda concerns me . . .
im forced to choose between over paneling and running it really hard OR running 2 panels and getting about half the total kwhrs for an all day average. [cant afford another one right now] with all 4 i was getting about 450 watts at 5PM which to me is freaking sweet] sorry i ramble