Can I Use a Smaller Charge Controller on this System?

[AgroVenturesPeru]

I currently have a victron 250/100 on my system. The unit needs replacement.

Was thinking about downsizing until I can get a replacement 250/100.

PV array is 4s4p. Highest PV voltage I've ever seen is 190V.

Unfortunately, I think the PV array is the limiting factor here. Since each string is four 400w panels in series I will always need a charge controller with at least 200V capacity. Even if I were to disconnect 3 out of the 4 strings from the MC4 connectors.

Would be nice to get a cheap charge controller such as a 100/85, while the current one is in for service. But is that even feasible?

Here's my stringbox:


And the inside (I hadn't installed the cable gland or the output PV wires yet when this photo was taken:


Also, I have three of these batteries FWIW for the amperage calculations for the charge controller's output:

 

[time2roll]

To use a 100/85 I think you know voltage will need to be cut in half so two max in series. Then 5 or 6 strings in parallel should load it up to 85 amps.

 

[AgroVenturesPeru]

PANEL SPECS:


One string is made up of these 410W panels:

 

[AgroVenturesPeru]

To give you an idea of the options available locally:

Regulador de Carga Solar Digital en Lima Peru - Panel Solar Peru

Los reguladores de carga solar son diseñados especialmente para proteger el nivel de carga de la bateria haciendo que estas te duran mas tiempo. Lima, Peru.

www.panelsolarperu.com

I was thinking about getting the LD Solar MPPT 200/80. Do you think that would be good enough for temporary use (up to one month)?
What other considerations? Should I disconnect a battery and run only two batteries? Not run any demanding appliances like electric oven/ electric stove? What about running this hot water heater daily?


I don't remember what the amperage number (the second number) refers to when talking about a charge controller. For example, in a victron 250/100 I know the first number refers to the max number of volts the charge controller can tolerate from the panels, but I forget what exactly the second number refers to. Is it amps from the panels or is it amps to the batteries?

Everything is victron: cerbogx, multiplus 48/5000/70 inverter. Batteries are the Pylontech US3000 (specs in my post above).
Wondering if there might be compatibility issues since the temporary charge controller would not be victron? If so, how would you configure the system so that everything jives.

 

[740GLE]

What happened to the Victron unit that’s causing you source a replacement?

with 50v VOC I wouldn’t even try two panels in series on a 100v SCC.

How cold does it get where you live?

 

[AgroVenturesPeru]

Here are the specs.

I was talking with a dealer this morning. They have the 80amp version. The engineer on the phone was suggesting I get two of them or disconnect a couple of my strings. Not sure I can disconnect strings without totally redoing my string box (see photo in my first post). Definitely don't want two. Just trying to come up with a temporary solution and spend the least amount of money possible, while waiting for my victron replacement.

 

[AgroVenturesPeru]

What happened to the Victron unit that’s causing you source a replacement?

with 50v VOC I wouldn’t even try two panels in series on a 100v SCC.

How cold does it get where you live?

The coldest I've ever seen is 57F

 

[AgroVenturesPeru]

Here are the specs.

I was talking with a dealer this morning. They have the 80amp version. The engineer on the phone was suggesting I get two of them or disconnect a couple of my strings. Not sure I can disconnect strings without totally redoing my string box (see photo in my first post). Definitely don't want two. Just trying to come up with a temporary solution and spend the least amount of money possible, while waiting for my victron replacement.

More info on alibaba:

Ldsolar 80a 200v 12v 24v 48v Mppt Solar Charge Controller With Wholesale Price - Buy Mppt Solar Charge Controller,Wholesale Solar Charge Controller,Price Mppt Solar Charge Controller Product on Alibaba.com

Ldsolar 80a 200v 12v 24v 48v Mppt Solar Charge Controller With Wholesale Price - Buy Mppt Solar Charge Controller,Wholesale Solar Charge Controller,Price Mppt Solar Charge Controller Product on Alibaba.com

www.alibaba.com

 

[sunshine_eggo]

What happened to the Victron unit that’s causing you source a replacement?

with 50v VOC I wouldn’t even try two panels in series on a 100v SCC.

How cold does it get where you live?

It's broken. It's reading 3V higher than the open circuit voltage measured at the MPPT battery terminals as well as the Pylontech battery and Multiplus voltages, i.e., MP, pylontech and voltmeter say 1 voltage. MPPT says 3V higher.

The coldest I've ever seen is 57F

I'm going to go on record with those panels:

4S needs 250V
3S needs 200V
2S needs 150V

57°F is more than enough to push panels over 50V busting MPPT Voc.

Buy a 250v controller or modify your array for a lower voltage controller. Period.

 

[740GLE]

It's broken. It's reading 3V higher than the open circuit voltage measured at the MPPT battery terminals as well as the Pylontech battery and Multiplus voltages, i.e., MP, pylontech and voltmeter say 1 voltage. MPPT says 3V higher.




I'm going to go on record with those panels:

4S needs 250V
3S needs 200V
2S needs 150V

57°F is more than enough to push panels over 50V busting MPPT Voc.

Buy a 250v controller or modify your array for a lower voltage controller. Period.

Any idea at how it failed?

How’s lightning protection on the system?

 

[sunshine_eggo]

Any idea at how it failed?

I've been helping him for some time via PM. The Voltage reported by the MPPT is "drifting". According to VRM, back in November, the difference was only 0.7V.

There are no other identifiable issues with the unit. A > 1% deviation in measured and reported voltage makes the unit eligible for warranty replacement.

How’s lightning protection on the system?

No idea. I'll leave that to @AgroVenturesPeru

 

[AgroVenturesPeru]

It's broken. It's reading 3V higher than the open circuit voltage measured at the MPPT battery terminals as well as the Pylontech battery and Multiplus voltages, i.e., MP, pylontech and voltmeter say 1 voltage. MPPT says 3V higher.




I'm going to go on record with those panels:

4S needs 250V
3S needs 200V
2S needs 150V

57°F is more than enough to push panels over 50V busting MPPT Voc.

Buy a 250v controller or modify your array for a lower voltage controller. Period.

Buy a 250V controller it is!
Not going to modify the wiring of the array.

Is it possible to exceed a panel's open-circuit voltage somehow? I was of the understanding that Voc was the absolute maximum voltage that a panel can produce.

Still, I agree it's not a good idea to get close to the 200V limit on one of these charge controllers, especially not on a chinese cheapo unit. Those voltages are likely way overstated, and the product subject to failure at much lower voltages.

 

[AgroVenturesPeru]

Hey @sunshine_eggo what do you think about getting a victron 250/70? There's a distributor with one of those in stock. Also another distributor has the 250/100, which is what we're leaning towards. Still trying to somehow get a reimbursement for the purchase at the end of all this instead of an extra unit.

I think it would be harder to resell a used 250/70 than a new, factory-sealed 250/100.

 

[time2roll]

Is it possible to exceed a panel's open-circuit voltage somehow? I was of the understanding that Voc was the absolute maximum voltage that a panel can produce.

Yes anything colder than the standard testing temperature will increase voltage. My first comment was based on the "never above 190"

See temperature coefficients in the panel specs.

 

[sunshine_eggo]

Buy a 250V controller it is!
Not going to modify the wiring of the array.

Is it possible to exceed a panel's open-circuit voltage somehow?

Yes. anything below 25°/77°F.

At 57°F, your 4S array will be at 206V per specs.

I was of the understanding that Voc was the absolute maximum voltage that a panel can produce.

All panel specifications are at standard conditions.

Still, I agree it's not a good idea to get close to the 200V limit on one of these charge controllers, especially not on a chinese cheapo unit. Those voltages are likely way overstated, and the product subject to failure at much lower voltages.

Not on ANY unit. The only ones with an exception that I know of are Midnite Solar. They have a HyperVOC mode where they have a safety buffer based on battery voltage, i.e., a 200Voc controller on a 48V battery will be okay up to 248V, but it will not produce any power if voltage is above 200V.

Again, I don't care who makes it. Don't even think about pushing the Voc limit.

Hey @sunshine_eggo what do you think about getting a victron 250/70? There's a distributor with one of those in stock. Also another distributor has the 250/100, which is what we're leaning towards. Still trying to somehow get a reimbursement for the purchase at the end of all this instead of an extra unit.

I think it would be harder to resell a used 250/70 than a new, factory-sealed 250/100.

The 250/70 has a 35A PV input limit, and your panels are over 40. This is a soft limit, but if you accidentally reverse your array polarity, the unit will be damaged. Below 35A, and the unit can protect itself. For that reason, the minimum size is a 250/85 with a 70A PV input current limit.

If you can swing a 250/100... might as well. Either way, it's a lot of money, and I would discourage resale and retain anything you get as backup.