What is the Max Power capacity of Rich (Renogy,etc) MPPT?

[unsubscribed]

So, I know that the Rich Solar 20 MPPT can handle a maximum of 20 Amps. So, in theory, since it has a max input voltage of 100 volts, it should handle 2000 Watts of solar power. Right?

But, the Victron brand of MPPT's - which, arguably are much more robust products - are not rated for I x V = max power.

For example, to my surprise, my SmartSolar 150/35 can only handle 1000 W of solar, and that is only when I'm using a 24 Volt battery bank. They derate to 500 W for a 12 V system. (To be fair, Victron does publish this fact in their data sheet. I simply assumed it could handle 5250 Watts of power. (150 V x 35 A.) Which, now that I write this, does seem rather unbelievable.)

But I cannot find anything in the Rich Solar MPPT manual about its max power capability. I suppose I would expect its max power capability to vary with battery bank voltage too, like the Victrons. But again, nothing that I can find.

Has anyone maxed out a Rich Solar 20 MPPT? Or its equivalent?

 

[snoobler]

You don't understand the ratings.

The "20" or "35" are CHARGING currents, i.e., that's the maximum current they can supply to a battery. They're not "derating" it. They're limited by the charge current. Victrons additionally have a PV input current limit that must not be exceeded. In your case, it's 40A.

35A * 28.6V = 1000W.

150v isn't a realistic operating voltage. You need to allow for cold weather voltage effects, and you use Voc for this limit, not Vmp.

Let's say you put 6 100w panels in series. This would have a Voc of 132V. Your peak operating voltage would be around 105V, so realistically, 105V * 40A input = 4200W (6S7P array) - the array could be this large ("over-paneling" the charge controller), but it would only use 1000W. However, it would maintain 1000W for as long as a 4200W array puts out 1000W or more - almost all day vs. only putting out 1000W at solar "high noon".

The rich solar has a 20A limit regardless of voltage. Assuming it's calculated to the same peak on a 24V battery: 20A * 28.6V = 572W

When a PV input current limit isn't published, you assume it's the same as the output. Some units tolerate exceeding this value, others don't.

 

[BlueFox]

It's 20A output current, so at 12V that's 240W, 24V is 480W, and so on.

MPPT controllers where the solar panel input is higher voltage than the battery bank are buck type converters, so the output current will be higher than the input current.

They also have a maximum input voltage that you need to stay under as well.

 

[unsubscribed]

@snoobler and @BlueFox Thanks. You're exactly right. I made a noob mistake by thinking that the 20 A rating was for the input current. (In my defense, an understandable mistake, since the first number in my Victron MPPT is for the Input Voltage.)

Looking back on it now, I should have made the connection that the 35 number was was 35 A Out, since the MPPT software defaulted to 35 A for the max battery charging current. Now the different power ratings at the different battery voltages make sense. (I should have noticed that they were multiples of the battery voltage.)

So now I see that I should have paid a little more for the Rich Solar 40, as my 20 unit cannot even handle two of the new 330 W units that I recently bought.

When will making mistakes end? This is turning out to be an expensive way to learn.

 

[BlueFox]

@snoobler and @BlueFox Thanks. You're exactly right. I made a noob mistake by thinking that the 20 A rating was for the input current. (In my defense, an understandable mistake, since the first number in my Victron MPPT is for the Input Voltage.)

Looking back on it now, I should have made the connection that the 35 number was was 35 A Out, since the MPPT software defaulted to 35 A for the max battery charging current. Now the different power ratings at the different battery voltages make sense. (I should have noticed that they were multiples of the battery voltage.)

So now I see that I should have paid a little more for the Rich Solar 40, as my 20 unit cannot even handle two of the new 330 W units that I recently bought.

When will making mistakes end? This is turning out to be an expensive way to learn.

It's definitely an easy mistake to make, I imagine most of us have gotten confused by current ratings at some point!

As far as your 20A controller goes, you could probably resell it easily enough, or if it's still in the return period send it back and maybe pay a small restocking fee depending on the retailer.

 

[snoobler]

@snoobler and @BlueFox Thanks. You're exactly right. I made a noob mistake by thinking that the 20 A rating was for the input current. (In my defense, an understandable mistake, since the first number in my Victron MPPT is for the Input Voltage.)

Looking back on it now, I should have made the connection that the 35 number was was 35 A Out, since the MPPT software defaulted to 35 A for the max battery charging current. Now the different power ratings at the different battery voltages make sense. (I should have noticed that they were multiples of the battery voltage.)

So now I see that I should have paid a little more for the Rich Solar 40, as my 20 unit cannot even handle two of the new 330 W units that I recently bought.

When will making mistakes end? This is turning out to be an expensive way to learn.

Consider that at 660W, you're only over-paneled by about 100W (@24V). It's unlikely you'll miss that much.

If it makes you feel any better, I made a much more expensive mistake. When configuring my system, about a year before I found DIY Solar, I selected a 150/100 for my 6kW of 72 cell panels. At 48V, the controller is good for 5800W. Well, I planned for 3S6P. I didn't account for the cold temperature affects on panel voltage. I was way too close to the 150V limit. If I rewired for 2S9P, I would be over the 70A PV input limit. My choices were get a second charge controller or upgrade to a 250/100 for $900. Lazy won. I left the panels 3S and bought the 250/100. Did sell my 150/100 for a decent price, so it could have hurt worse.

 

[unsubscribed]

Thanks for that. It eases the pain of my ignorance.

 

[snoobler]

If it helps more, this is my second system... I spent about $700 on a small 24V system before I moved up to 48V...

And I bought $2700 worth of solar panels planning to do grid tie on the house BEFORE I did the research and discovered how horrible it is with my utility.

Now I have 10kW more solar than I planned for at the off grid ranch...