victron mppt controllers

[bob golding]

have been looking at these as they good like a very good deal. £90 for a 15 amp mppt controller is a good deal compared to other mppt  controllers. anyone had one for a while? i am slightly confused about  what happens if you exceed the rating. i am unlikely to have that happen in the winter,but  i cant seem to get a answer from any of the suppliers. the standard answer of course, is buy 2.  i know  that but would still like to know how they handle overloads. anyone know?

[Flux]

The Victron Blue Solar 15A unit is a nice one and very good value for money.

It handles 200W of solar wirh  a 12v battery and is best suited to  a 24v panel ( 72 cell). It will handle up to 36v nominal in.

It will also work on 12v with a nominal 12v panel ( 36 cells) but I wouldn't use it that way.

It does current limit sharply at 15A and gets rather hot when current limiting, probably ok short term but can't be good long term.

In poor light conditions you can run up to about 300W of panel but under good conditions it will be close to current limit with 200W. It is a 200W device and if you have too many panels I would run 200W via the controller and any excess direct.

There is a bigger one that I wouldn't touch, it uses the same voltage panel as the battery ( 36 cell at 12v or 72 cell at 24v) this is not then best way to run things and does nothing for the cable I^2R drop and doesn't give the best match.

I would buy more than one 15A unit rather than any of the more expensive 30A units at a far higher price. When you get over 40A then is the time to look at Morningstar, outback or classic,
where you can justify the cost but for the small end I like the Blue Solar 15A. I really have no idea what the Chinese things are like , some may be ok, othere are certainly crap and until you get it you have no idea what you will end up with.

Flux

[bob golding]

thanks flux. i am using 24 volts so should be ok up to 400 watts. i have never seen more than 8 amps with the panels connected directly to the batteries so should be ok. i am planning to use 2 of them as  i add more panels. so the heatsink absorbs the excess power then?  i am still using the morning star ts45 in diversion mode so i don't overcharge the batteries.

  morningstar are sending me a replacement controller. cant complain about there customer support. still a bit puzzled as to why they keep blowing fets. the fets are ir fb4321s so should be well within thier specs. 85 amps 150 volts max so even derating them 50% they should be ok. will replace the fets on the faulty one and keep it as spare. not that i would trust it for unattended long term use.