Victron charge controllers

[Bluedog225]

I’d appreciate any thoughts on whether I should get a single large (450 volt/200 amp) Victron charge controller or several smaller VE.CAN charge controllers.

I’m leaning towards several smaller ones. I vaguely recall someone saying that the lower voltage charge controllers have better efficiency. Better efficiency combined with the greater reliability of multiple controllers would probably push me away from the big controller.

Thanks

 

[cdsolar]

Well, depends on how your combined strings are set up. One combined set of strings per charge controller may allow for expansion of a given string later without reconfiguring the rest. A single charge controller doesn't necessarily allow for that if it is close to its voltage limit.

Be sure that you account for higher voltage in the cold months if that is an issue, with enough voltage rating of each controller to account for the cold voltage increase, regardless if you go single or multiple.

So I would ask you to consider multiple controllers and multiple (combined) strings, each oversized a bit to account for cold weather voltage and later expansion. Multiple strings with multiple controllers means more wiring, so of course you need to make the right decision for you.

 

[chrisski]

I’m not sure efficiency alone would matter. The Victron is a pretty efficient unit.

A lot of things I’ve measured, the actual results of the efficiency is insignificant. Some results of added efficiency can be overcome with a few extra minutes at charging best, or quantified with not even 100 watt hours extra of power.

Higher voltage is better for early production, but when I measured this one day with 900 watts of panels, this got me charging 15 minutea earlier with an insignificant extra amount of power.

Flexible panels were more efficient than glass panels, buit only by producing 7 watts per 100 watts of panels versus 6 watts per 100 watts of panels. Not anything significant.

With a charge controller, it’s hard to see exactly how efficient it is. The are more efficient at certain panel voltages than others. The spec sheet says the 250/100 is up to 99% efficient and the 450/200 is up to 96% efficient, but there is no voltage and amperage chart on either to eleaborate on the “up to” portion of it.

 

[sunshine_eggo]

I’d appreciate any thoughts on whether I should get a single large (450 volt/200 amp) Victron charge controller or several smaller VE.CAN charge controllers.

I’m leaning towards several smaller ones. I vaguely recall someone saying that the lower voltage charge controllers have better efficiency.

I've said this. It's important to point out that these efficiency differences are usually offset by wiring efficiencies, e.g., a 48V system with controller running at about 72Vmp is going to be at maximum conversion efficiency of about 1-2%; however, this may be gobbled up by wiring losses due to lower voltage and higher current. It's often a wash.

The higher voltage MPPT to attempt to minimize conversion inefficiencies in accordance with their anticipated operating voltages, and when one is looking at these higher voltages for longer wiring runs, they often present a notable overall improved efficiency due to reduced wiring losses.

Better efficiency combined with the greater reliability of multiple controllers would probably push me away from the big controller.

Revised for more appropriate context. That's really the only reason, particularly if your wiring runs are reasonable where a 150V controller would suffice.

Thanks

There are a couple of massive advantages of the RS450 controllers.

1) multiple trackers: the 450/200 has four separate 450V/18A in trackers . Each tracker can output a maximum of 4000W with a combined maximum of 11,520W.
2) true galvanic isolation. While it's rare, even a Victron MPPT can fail and short panels to battery, which can be devastating. The RS450 line absolutely, positively can't short the panels to the battery.

The unit can also accept up to 20A Isc and retain reverse polarity protection. If you want to over-panel and are willing to forego reverse polarity protection, you can go to 30A Isc on each tracker.

 

[Bluedog225]

2) true galvanic isolation. While it's rare, even a Victron MPPT can fail and short panels to battery, which can be devastating. The RS450 line absolutely, positively can't short the panels to the battery.

I won’t pretend to understand exactly what this means. And why a fuse wouldn’t protect the system. I’ll research galvanic isolation but, well, I’m not a smart man. ?

But avoiding the risk of a catastrophic loss of the inverter or batteries is a primary concern.

Somebody called seeking higher voltage charge controllers a fetish so I’m glad I double checked.

Thanks Waffleman!

 

[jamiegreen]

I won’t pretend to understand exactly what this means. And why a fuse wouldn’t protect the system. I’ll research galvanic isolation but, well, I’m not a smart man. ?

But avoiding the risk of a catastrophic loss of the inverter or batteries is a primary concern.

Somebody called seeking higher voltage charge controllers a fetish so I’m glad I double checked.

Thanks Waffleman!

Its just.. magic and stuff.
As far as I'm aware it means there are windings used to transfer the power from the solar side to the battery side with no direct connection between the two, minimising damage if a major fault occurred, meaning you wont get 400v of unregulated voltage and current getting sent direct to your batteries, a BMS may protect against this, but not a fuse, as its not over current, its more a case of cooking the batteries if left unnoticed.

I recently thought about either a 250/70 or an RS 450/100, ended up getting the 250. Its 1/3 the price and suits my needs for a 5kw array, sure beats the 150v version, which with panels generally being around 40v OCV, leaves an awkward array if you have an even amount of panels, 2s leaving voltage a bit low for a 48v system, and 4s being too high of a voltage for the controller. so the 250v version solves this for me.

If my system was any bigger I would definitely go for one of the RS models, they look great, I'd probably choose a single unit over multiple smaller ones, especially with the much higher voltage input on the RS models.