Why choose lower capacity Victron MPPT controller?

[MattS]

Hopefully a simple question!

There are obviously a range of Victron MPPT solar controllers, all with different power capabilities. The question is:

Is there a reason to choose a lower capacity controller (e.g. 75V/10A) over a higher capacity one (e.g. 75V/15A) other than purchase cost?

I only have a 30W panel at the moment, so although the smallest would suffice, there is about a fiver different in price between the two. Is there something I'm missing about matching controllers to panel sizes that's important here?

 

[Stemar]

I don't know the answer to your question but, if you haven't done it already, one thing to ask yourself is, What's the likelihood of you ending up with enough panels to overload the cheaper one?

 

[MattS]

I don't know the answer to your question but, if you haven't done it already, one thing to ask yourself is, What's the likelihood of you ending up with enough panels to overload the cheaper one?

Quite unlikely in the near future - and if the price difference wasn't literally £3, I'd just be going for the lower one! But the similar prices made me question whether there's another reason to use a lower one

e.g. if your panel is too small, do the higher capacity controllers not work properly?

Victron Energy Smart Solar MPPT 75V/10A - (12/24V) - Sunshine Solar - 75V/10A - £102.95
Victron Energy Smart Solar MPPT 75V/15A - (12/24V) - Sunshine Solar - 75V/15A - £105.95

 

[RichardS]

Go bigger if the price permits.

Richard

 

[chris-s]

One thing to check is the controller starting voltage particularly with smaller panels. I nearly made the mistake of buying panels that would not have ‘started’ the Victron controller.

 

[William_H]

Yes go for bigger one. However if you have a smaller one it is not possible to "overload" the smaller controller. If you have excess solar panels provided max voltage is not exceeded the controller will only take what current it needs from the panels. So the limitation is the max current out ie 10 amps. To have excess panels simply means you can get max into batteries (10 amps) under more marginal solar conditions. I don't know if small solar array might under some conditions not have enough power to kick start the controller. Conceivable) But then you would imagine a small controller would need just as much power to kick start as a bigger controller. ol'will

 

[lustyd]

Go bigger if the price permits.

Richard

Between those models I'd agree, but through the whole range there are reasons such as physical size and potential heat to go for the smaller one

 

[RichardS]

Between those models I'd agree, but through the whole range there are reasons such as physical size and potential heat to go for the smaller one

But heat produced will be 99% related to input and output voltages and current so, in that sense, independent of the size of controller.

Richard

 

[MattS]

Thanks all - for the extra 3 quid, I went for the 75/15 model!

 

[lustyd]

But heat produced will be 99% related to input and output voltages and current so, in that sense, independent of the size of controller.

Richard

Indeed, but if you fitted a 50A one in a space which has insufficient cooling for a full load then you'd have a problem that two 30A controllers separately located would not suffer from since the heat could be in two or more locations This is a big concern on boats as we're usually cramming them into less than ideal cubby holes. Realistically, physical size is likely the biggest driver once capacity is taken care of, and that will definitely be a bigger consideration for most than cost. The 100/15 and 100/20 are fairly different in physical size, for instance, but again only a couple of pounds difference in cost.

 

[[2574]]

Thanks all - for the extra 3 quid, I went for the 75/15 model!

I hope you went for the Bluetooth version - it's useful to conveniently see solar performance on your phone/Tablet

 

[jwfrary]

Theres a sizing tool on victrons website I reccomend you use that.

What will increase yield is using a higher voltage panel 24v with a 12v system, you will start charging earlier and end later. yield is everything with solar.

 

[lustyd]

Theres a sizing tool on victrons website

I'd be a little wary of their sizing advice. If you do their official training they recommend sizing down the MPPT to reduce cost on the install. For some reason they ignore the extremely small difference in cost when doing so, so you may get a controller which will run 100% during the brighter hours, losing some of the power. This is all explained in the training, which seems at odds with what most people seem to want when speccing one up. I've never seen anyone decide to lose some solar energy for a £10 saving!

 

[MattS]

I hope you went for the Bluetooth version - it's useful to conveniently see solar performance on your phone/Tablet

I did!

 

[MattS]

Interestingly - the 75/10 and 75/15 Smartsolar units both have the same housing, so even dimensions don't appear to be a factor in the £3 price difference in this case!

https://www.victronenergy.com/upload/documents/BlueSolar-&-SmartSolar-MPPT-75-10-&-75-15.pdf