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jfrohoff avatar image
jfrohoff asked

Is it OK to put more thann 30 amps into SmartSolar 100/30 from panels?

Hello all, I have 4 100 watt Renogy 12v panels setup as 2S, 2P into a 100A Lithium (will upsize to two later this year). I want to purchase a 100/30 Smart Solar MPPT. due to very low radiance during winters up here in Seattle I will only harvest .5 KWh/day based on the Victron Calculator, but three times that, or more during summer (about 28A if full power, which will likely never happen). Can I add another 200 watts (2S) to boost winter output even even if full power into the controller exceeds the 30 amp max output current during summer? or do I need to buy another MPPT? With two MPPT I could exceed max 30A recharge C rate, so not preferable. Thx.

@jfrohoff

MPPT Controllers
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seb71 avatar image
seb71 answered ·

What's the Isc for those 100W panels?

Can't be very high, so 3 strings (of two panels each) in parallel should be OK.


Also what's the Voc? If you get 6 of those panels, you might be able to put 3 in series, so only 2 strings in parallel.


In both cases make sure that the new panels are identical with the old panels.


Also take a look at your price difference between SmartSolar 100/30 and a SmartSolar 150/35. The 150V limit of the second one allows more flexibility if you want to upgrade to bigger panels.


Note:

You can limit the charging current from the MPPT settings.

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jfrohoff avatar image jfrohoff commented ·

Whoops! First time on forum and I accidentally posted my reply as another answer - didn’t initially notice the comment icon.


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jfrohoff avatar image
jfrohoff answered ·

Thanks. Isc is 6.1A. Voc is 21.7v.

I wanted to add more panels due to minimal winter radiance, yet don’t want to overpoer the controller during summer. I’ll be ok with the voc since I need to go with 2S strings based on the panels I have so as to not mis-match. But if I exceed 15 amps input on the 75/15 on a very sunny day will it safely handle it? From what I read in the manual the “15” in 75/15 means the max battery charge output current, but does that also apply as a never-to-exceed value in the panels input to the controller? thx

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seb71 avatar image seb71 commented ·

In your first post you said you want to get a SmartSolar100/30.

Now it's a 75/15?


Maximum input current (max Isc of the PV array) is listed in the MPPT datasheet.


Do not put different PV panels on the same MPPT charger.


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jfrohoff avatar image jfrohoff seb71 commented ·

Thx @Seb71. Sorry for being confusing. I already own a 75/15. After more research I thought I will need to switch to a 100/30 for a larger array. I think you answered my question and it tells me the solution … “ Do not put different PV panels on the same MPPT charger.”. I’ll go ahead and purchase a 100/30 or 150/35 for my second string (2 x 100 watt glass Renogy panels) leaving room for some expansion and keep the first 200 watt 2S string (2 x Renogy flexible 100 watt) on the 75/15. Though I will still need to limit max charger output amps if using both strings until I can buy a second battery. I know the flexible panels will have a short lifespan. Portability is critical for at least one string due to the application. I’ll read the data sheet again for max MPPT input current limits; missed it on first read. Thx.

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jfrohoff avatar image jfrohoff seb71 commented ·

The isc and voc I gave you are for the 100 watt flexible panels.

I read the controller spec sheet again as recommended. The footnotes contain the info I was asking about.

“1a) If more PV power is connected, the controller will limit input power.” (Obviously wasting power, not good)

“2) A PV array with a higher short circuit current may damage the controller.”

@Seb71 Your answer of putting different panel model strings on different controllers appears to be the best solution.

i obviously need to do more research on handling strings of panels with different specs.

Thx.

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seb71 avatar image seb71 jfrohoff commented ·

“1a) If more PV power is connected, the controller will limit input power.” (Obviously wasting power, not good)

When the Sun is covered by clouds or in an less than optimal position relative to the PV panels or when the panels are hot, they will not produce at their nominal power. So a certain oversizing of the PV power is OK.

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Unlike the PV array maximum voltage (Voc), which if surpassed guarantees that the MPPT will be damaged, the PV array Isc current limit is not so problematic. PV modules do not "push" current into the MPPT. So having a PV array with a nominal Isc higher than the maximum from the specifications does not mean you will certainly destroy the MPPT.

But oversizing the PV array by a reasonable amount also keeps the PV array Isc under the limit. So usualy that's not a problem.

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