Victron mppt sizing

[1967bowesj]

Upgrade time so looking on the victron web site wizard for which mppt, it’s confusing me so need the collective fun advise.

Have two 175w roof mounted panels, which I was thinking the 100/30 mppt but the victron wizard is suggesting the 100/20.
Not wanting the mppt to be flat out all the time in summer so looking for advise.

John

 

[WESTY66]

Upgrade time so looking on the victron web site wizard for which mppt, it’s confusing me so need the collective fun advise.

Have two 175w roof mounted panels, which I was thinking the 100/30 mppt but the victron wizard is suggesting the 100/20.
Not wanting the mppt to be flat out all the time in summer so looking for advise.

John

My very limited knowledge would have me fitting a 100/30 Bluetooth MPPT at least

 

[Carpmart]

100/30 would be my choice… that’ll give you headroom (just about) for another matching panel in the future.

 

[AdrianChen]

I used the spreadsheet version but does the same thing - I have two of the 175 Victron panels (Mono) and like you it recommended the 100/20, but there was a note to say power limiting in low and high temps, to eliminate both of those those it required a 100/50 - cost difference around £130 vs £70.

Doubt in most UK weather it would make any difference, but went for the 100/50 anyway.

 

[Carpmart]

I used the spreadsheet version but does the same thing - I have two of the 175 Victron panels (Mono) and like you it recommended the 100/20, but there was a note to say power limiting in low and high temps, to eliminate both of those those it required a 100/50 - cost difference around £130 vs £70.

Doubt in most UK weather it would make any difference, but went for the 100/50 anyway.

The 100/50 is way overkill IMHO…

^{_{Subscribers  do not see these advertisements}}

 

[1967bowesj]

I find it a bit odd the site down grades the controller, I’d have expected it to go up a size.

 

[Lenny HB]

I have 2 x 175w panels and fitted a 100/30 the 100/20 is only rated at 290 watts of solar. I know you are never lightly to get full power from the panels unless on the equator in June but there is only a few quid difference in price.

 

[AdrianChen]

The 100/50 is way overkill IMHO…

Probably you're right, I played around with the default module temps, and perhaps in winter Norway/Summer Morocco there can be an impact, but doubt I'll meet the extremes in the UK!

 

[Gordo]

PM me if youre after a 100/30 - i just swapped mine for a 100/50 after I’d chosen the wrong one (4x130w panels).

 

[AdrianChen]

I find it a bit odd the site down grades the controller, I’d have expected it to go up a size.

I think 100/20 will be fine, and even if you were in conditions where the "limiting" came in to play, would it be critical?

So the fact that the calculator says accepted on a 100/20 means Victron are good with it, so not downgrading at all.

^{_{Subscribers  do not see these advertisements}}

 

[1967bowesj]

I think 100/20 will be fine, and even if you were in conditions where the "limiting" came in to play, would it be critical?

So the fact that the calculator says accepted on a 100/20 means Victron are good with it, so not downgrading at all.

Must have critical then as you went 100/50, it maybe acceptable to victron but why waste the throttled available solar and limit the potential to store energy.

 

[AdrianChen]

Must have critical then as you went 100/50, it maybe acceptable to victron but why waste the throttled available solar and limit the potential to store energy.

Yes, but things like this just bug me! I had plans to go to Norway, etc so though for the incremental cost why not! From memory when I fiddled with the calculator it was around 1.5amps ish on the low temps, which is the range I was interested in. Would see little or no difference in the UK summer I expect.

I guess it's similar to someone with a small wattage panel upgrading from PWM to MPPT, small gain on a small panel - will it make any difference in practical terms?

At 100/30 it's only the cold element that might clip, so perfect for anyone who tends towards the warmer climate areas so Lenny HB will be fine - and happy he hasn't spent the extra £££. (Got that FB PI working yet Lenny HB?).

 

[Raul]

If it was my choice, with 2x175W panels, I would not hesitate and fit the 100:30. The 100/20 will clip too much.
I know the panels are flat, but, from my experience and my real life monitoring, even flat panels can produce the nameplate value, sometimes even over that if you have a big enough controller. From spring to autumn at-least 2 hrs at noon can give full panel power even on flat roof, so I would go 100/30.

 

[Lenny HB]

(Got that FB PI working yet @Lenny HB?)

Finally got the UART to USB Hub they had been out of stock & printed a case for it, bought a new touch screen went for a 5", got to make a bezel & case for it.
Spent a lot of time play with the waste this week gave up trying to fit an actuator internally my valve was to stiff to work reliable so fitting an external valve. Then back to the Pi.

 

[Raul]

Have a look at PI shop for screen box, sometimes they have this in stock.

^{_{Subscribers  do not see these advertisements}}

 

[Lenny HB]

Have a look at PI shop for screen box, sometimes they have this in stock.

I'm having fun printing my own.

 

[Guigsy]

Counter argument is that if you're managing to max out the 100/20 for an extended period, then there's probably so much sun at the moment that you weren't that empty anyway, so your battery will be full by 1pm. If you had the 100/30, you'd be full by 11:30 instead. So in any reasonable situation, it would be pretty unlikely that you'd get to the end of the day with more Ah in the battery with the larger unit.

 

[Raul]

Counter argument is that if you're managing to max out the 100/20 for an extended period, then there's probably so much sun at the moment that you weren't that empty anyway, so your battery will be full by 1pm. If you had the 100/30, you'd be full by 11:30 instead. So in any reasonable situation, it would be pretty unlikely that you'd get to the end of the day with more Ah in the battery with the larger unit.

Yes and no; is all dependable on the weather, that is not always guaranteed wall to wall sunshine. In the event of having a cloudy day, and sun to show up 2-4hrs, then you want to gobble in as fast and as much you can for that short window of time. In this case the larger controller will win.

 

[Guigsy]

Yes and no; is all dependable on the weather, that is not always guaranteed wall to wall sunshine. In the event of having a cloudy day, and sun to show up 2-4hrs, then you want to gobble in as fast and as much you can for that short window of time. In this case the larger controller will win.

The chances of it being the peak of summer, you're camped up off-grid, you've not moved (so no B2B charging), and it's been really cloudy for days (so your battery is low), then completely cloudless skies for a couple of hours around midday, then going cloudy again... is pretty unlikely.

The reality is that there's only a few quid difference, so yes, I'd get that 100/30 if it were an option. But I wouldn't bother changing if I already had the 100/20.

 

[tonka]

Another vote for the 100/30.
I have 2 x 170 panels and use the 30amp one.

^{_{Subscribers  do not see these advertisements}}