Help with Charge Controller Choice

[robvann]

Hi.. I have attempted to calculate the size of charge controller that I would require but would like some opinion based on my requirements.

I have sixteen 230 watt panels rated at 29.5 v with a rated current of 7.5 amps. They are wired in pairs to double the voltage. (48v under load I think). The battery bank is 48V.

I am thinking of going with the Outback Flexmax 80. Any suggestions or opinions would be appreciated.

Many thanks,
Rob Vann

[Cariboocoot]

Well let's see 16 * 230 = 3680 Watts total. Under most circumstances that would probably run 2834 Watts average. Divide by charging Voltage of around 58 Volts (get an accurate number here) and you get 48.8 Amps of current. In other words it isn't likely you'd need more than a 60 Amp charge controller here. That gives you lots of options including Morningstar, Outback, Xantrex, and Midnight Solar.

Be careful configuring such an array. You really need to know the panels' Voc and Vmp to get it right. 29.5 Looks to be the Vmp, and two in series would then be 59 Volts. That is barely charge Voltage for a 48 Volt system, and once the inevitable system losses are factored in it would not be enough. Certainly not for equalization. So it looks like you need a minimum of three in series. Then you have to watch the Voc which is likely 7 or 8 Volts higher. That means the Voc on a string of three could be 114 Volts. Note that 16 doesn't divide by 3, and if you go four in series the Voc could then be 152 which is over the limit for all the controllers except the Midnight.

But you need specific data for your panels to be sure.

[niel]

with only 2 of those pvs in series you may be undercharging a 48v battery bank at times so the strings need to be larger. 3 in a string would leave out 1 of the pvs as you'd only get 5 strings of 3. with a voc of about 37v (guessing) then 3 x 37v = 111v and is good for many controllers of the better mppt types. to use all of the pvs this means 4 paralleled strings of 4 in series and you are pushing the envelope for many controllers on the top end voltage. 4 x 37v = 148v. the midnite classic mppt controller would work very well i think for this application. if you are uncomfortable using the classic 150 they do have the classic 200 that has a higher operating voltage with a slightly lower current capability. the 200 would work without question, but cold temps could push the 148v higher than one may be comfortable with on the 150 (and nearly all other controllers) even though it would not damage the classic 150 controller with a slightly over 150v condition.

my recommendation is the classic 200 for you with the pvs in a 4 x 4 configuration. maybe boB or halfcrazy can reaffirm my opinion or correct me on this.

[Cariboocoot]

If I understand it right (and I may not) the Classic series is capable of handling Voc of its model rating plus nominal battery system Voltage. That would mean the 150 in this application could take a Voc of 198. As Niel said, the 200 would surely handle it. Even in the Cariboo.

[niel]

coot,
that is how far it can go without damage, but operating is different.
http://www.midnitesolar.com/pdfs/whyHyperVOC.pdf

[halfcrazy]

Niel is spot on there. Go with 4 panels in series and 4 strings and a Classic 200.

[Cariboocoot]

Remember: we do not know the actual Voc of the panels. 37.5 is an estimate I made, not info from the OP.

[niel]

Remember: we do not know the actual Voc of the panels. 37.5 is an estimate I made, not info from the OP.

coot,
i realize that we don't know the exacting voc figure, but it is sure to be in the area of 37 or 38v based on some pvs out there and when it gets cold all bets are off as it really skyrockets in most cases. read the scenario for the example pv with a vmp around 29.6v in the hypervoc pdf for canada. in any case it will exceed the 150v at times depending on what temps are experienced by the op and that would not be desirable to have happen.

[Cariboocoot]

Well you don't have to tell me about cold in Canada, eh?
Fortunately Nova Scotia isn't the Cariboo.

Just like to have the real numbers to show precisely what the situation is in case someone else is reading. We also do not know the capacity of the battery bank and thus whether all 16 panels are needed or if the OP could drop one and still have the power he needs.

Clearly there is no doubt the Classic 200 would handle it. Also that most of the other controllers would not if all sixteen panels are used.

[Dave Sparks]

Two strings of 8 in series into a Xantrex XW -80 -600v an easy installation!