I am interested in getting two of these Canadian Solar 400W Super High Power Poly PERC HiKU and connect them in series to get 90+ voltage but i see that the open circuit voltage is 47.2 V on the datasheet, my controller has max input of 90v, my questions are as follows:

 

• Will it do harm if i exceed max voltage by 5v when i have these in series?
• Will it be better to connect them in parallel for more Amps?

Yes you will damage the controller, there is by all accounts no leeway.

On the other hand for the controller to function it probably has to exceed the highest charging voltage by 5v +.

So if you have a 48V battery, two panels in parallel would mean the voltage is not high enough.

7 minutes ago, phil.g00 said:

Yes you will damage the controller, there is by all accounts no leeway.

On the other hand for the controller to function it probably has to exceed the highest charging voltage by 5v +.

So if you have a 48V battery, two panels in parallel would mean the voltage is not high enough.

I highly doubt that there exists a charge controller that supports 48V but will only have a max input voltage of 90V

 

Edit: Like in the Victron world you only start to get support for 48V from the 150/x MPPT chargers, which gives you 150V input voltage.

The 100V models only go up to 24V

Edited December 13, 20187 yr by PJJ

Thanks Phil, what happens if i step down the series input voltage to something maybe 80v? 

1 hour ago, 175SBU said:

I am interested in getting two of these Canadian Solar 400W Super High Power Poly PERC HiKU and connect them in series to get 90+ voltage but i see that the open circuit voltage is 47.2 V on the datasheet, my controller has max input of 90v, my questions are as follows:

 

• Will it do harm if i exceed max voltage by 5v when i have these in series?
• Will it be better to connect them in parallel for more Amps?

Which controller It is? Battery bank is 48 ir 24 V?

Yes,  given a 48V battery and the voltage limit you claim that would work.

 

I believe that it all depends on your mppt device.

Many of them will allow an overrate of 15 to 25%, but that is always a risk.

If memory serves me right,  @plonkster might also comment here, as he has on numerous occasions to my recollection explained this type of Over Voltage.

1 hour ago, Riaanh said:

Many of them will allow an overrate of 15 to 25%, but that is always a risk.

Power... not voltage.

Most devices stop charging before you reach the maximum voltage. Some will attempt to protect themselves by shorting the panels (so your Isc better be below what the controller can handle). As an example, a Victron controller might be rated for 150V, but by 145V it has already stopped charging. The maximum voltage rating is an absolute maximum... once you get there you are technically already in trouble.

What you can do is put 20% (or so) more power on the MPPT (in other words more strings in parallel). The MPPT simply limits it to the max it can do, so you get a longer flatter power curve. But you should probably limit the amount of oversizing to no more than 25%, and if you are concerned about heat (like our friend TTT) then don't do it.

Edited December 13, 20187 yr by plonkster

I have 2 x 100Ah batteries in parallel, the controller is non branded chinese SCM12/24v 30A  with input 18-90v. 

Then you only have a 12 or 24 battery, you only have to exceed your battery charging voltage by 5V+.

So panels in parallel are acceptable.

Well, we should know if battery bank is 12 or 24 V. If it is 12 V, it would be a pity install a pair of pannels because you are going to take advantage of only 420 w(+-), 14 V*30 A..

Also, controller could be damaged if you install 800 Wp to a 12 V battery bank.

Edited December 13, 20187 yr by Javi Martínez

Using Victron as an example, they have these 3 titbits in their docs that is rather important to note. Goes for all controllers, at least the ones I have used over the years.

The Rated charge current (1) is the max battery charge current the controller can supply, T&C's apply, that you can limit with the setup configuration.

The Nominal PV Power is a very good guidance between 12/24/48v - with the 20-25% over sizing based on that.

The parts that are rather serious:
1) The absolute max VOLTS, to not exceed that ever, this case below is 150v.
2) The part one must be very aware of to never exceed, same as the volts ... is point (2). For that see (3) 

Over sizing is very good for non-optimal situations, winter months, just steer clear of exceeding the volts and the max PV short circuit current of the controller/s at all times ... and feel the temp of the controller. Heat and electronic parts do not like to be in the same enclosure. Just common sense. :-) 

4 minutes ago, The Terrible Triplett said:

feel the temp of the controller

Something else occurred to me this morning: the smaller controllers have a plastic case. The larger ones is die-cast alluminium. Of course the larger ones will feel warmer... the heat from the heatsink is partially transferred to the front of the case.

I ran a 100/15 (plastic case) at 50% oversizing for about two months. Not nearly enough to state that it won't have a shorter life, but I can say that as hot as it got, it only derated its power by about 5% and never felt like it was too hot too touch.

That makes me wonder to what extent you need to be concerned with the die-cast cases. A heatsink at 60 °C or 70 °C is no reason for concern.

Nevertheless, I will concede that leaving margins is always a good idea. Generalisations just don't sit well with me, and "never oversize in Africa" is one such generalisation :-)

2 minutes ago, plonkster said:

... "never oversize in Africa" ..

Not me who made that generalization although I did ask for ""Africa" because a few Victron parts are going up into Africa, as well as in and around Postmasburg. And it is hotter there than my Cape Town braai room at 30°C.

I will get a fish tank thermometer, keep it cool, then slap it onto the controllers casing on one of the nice piping hot days and see what the actual temp is on the die-cast aluminium casing. 

Will still add a fan though ... the power is for "free" IF the controllers casing gets really hot. :-) 

8 minutes ago, The Terrible Triplett said:

I will get a fish tank thermometer, keep it cool, then slap it onto the controllers casing on one of the nice piping hot days and see what the actual temp is on the die-cast aluminium casing. 

That would be a nice result!

In theory MPPT makes work solar pannels to higher voltages to reduce current, if it is necessary,  so we could think we can add the power we want without consequencies. But it is not true at all, because MPPT effieciency get worse with higer voltages in solar pannels. Also, if MPPT is oversized will work more time giving the peak current, with more time with high temperatures, reducing its lifespan.

On 2018/12/13 at 1:21 PM, plonkster said:

That would be a nice result!

Ambient temp is 31°C.

Batteries are at ... that spike yesterday evening!

Batts are in a wooden box ... at the time of the controller temp, they are 33°C.

 

And the controller temp.

Note: Cannot go above 50°C ... it is way over 50°C as I cannot keep my hand on the MPPT at all.

 

Any better idea to measure the temp?

I'm using a fan ... "finish and klaar". With fan it sits on a cool +-30°C.

I touched my 150/35 yesterday afternoon. It was doing 25A at the time, so around 70%. It was uncomfortable to touch, as in, after a few seconds it starts to burn your hand. Of course the 100/15 never felt like this (plastic case), so at least it shows my thinking about the diecast case is accurate: It is probably taking up some heat from the heatsink.

22 minutes ago, The Terrible Triplett said:

Any better idea to measure the temp?

Cheap thermocouple multimeter :-) I wish I had one...

9 minutes ago, plonkster said:

It was uncomfortable to touch ...

For the record: I don't doubt the controllers can take it, not for one moment. If it was an issue, they would have fans.

What I don't like:
It is a fact that the controller is mine, therefor all the parts inside it are mine too.
And I don't like electronic parts I own getting piping hot. 

Just to be clear. :-) 

EDIT: And they are installed in boats and ships, where ventilation can be a challenge.

Edited December 17, 20187 yr by Guest

10 minutes ago, plonkster said:

Cheap thermocouple multimeter :-) I wish I had one...

Look at www.Banggood.com for under R250 - I'll spend R250 on a nice fan on a timer. :-) 

I have Canadian KuMax 350w panels right. 6 of them.

This is the best they have given me to date, a whopping 2752w ... I'm impressed.

And highest volts ever: 135.97