Another Solar Question

[pearley]

I have three 80 watt semi flexible solar panels on the roof wired in series feeding into a Tracer 30 amp MPPT controller. All 3 panels are from the same manufacturer and have the same specification but unfortunately they no longer make the 80 watt version.

 

So, if I want to add to the bank of panels, how close in spec would the extra panels need to be? Could I mix rigid glass panels with the semi flexibles? If I added an extra two 80 watt panels so theoretically giving a maximum of 100 volts and 33 amps would I need a bigger controller given that they are very unlikely to give the maximum in this country.

 

Regards

Pete

[valrene9600]

Interesting question. I have no knowledge but always ready to learn.

Just how much over the stated volts can you go considering our suns likely output.

 

Edit. I mean put through the controller in excess of stated capacity

Edited October 7, 2014 by valrene9600

[matty40s]

if your new panels are the same nominal voltage (ie 12V) the you can add similar in series.

Check whether yout 30A tracer is the 100V max or 150V max one, both are sold sometimes by the same suppliers, and sometimes the wrong ones are sent out.

It is the voltage that is the critical amount, and excess can blow the controllers internal fuses and worse. We are now coming to the time of year when peak voltages start to occur, low temperatures and strong sunshine.

[valrene9600]

Thanks Matty.

I wonder how many folk like me thought the voltage would be highest in high summer.

More reading to do.

[nicknorman]

I have three 80 watt semi flexible solar panels on the roof wired in series feeding into a Tracer 30 amp MPPT controller. All 3 panels are from the same manufacturer and have the same specification but unfortunately they no longer make the 80 watt version.

So, if I want to add to the bank of panels, how close in spec would the extra panels need to be? Could I mix rigid glass panels with the semi flexibles? If I added an extra two 80 watt panels so theoretically giving a maximum of 100 volts and 33 amps would I need a bigger controller given that they are very unlikely to give the maximum in this country.

Regards

Pete

Wiring panels in series, the max power current needs to match the existing panels. As Matty says, you have to be careful not to exceed the controllers max voltage rating taking into account the voltage temperature coefficient. Wiring panels in parallel, the max power voltage needs to match the existing panel string.

[by'eck]

So in essence if the max voltage (panels in series) or max current (panels in parallel) of MPPT controller is not exceeded it will work, but without matching panels not efficiently.

[nicknorman]

So in essence if the max voltage (panels in series) or max current (panels in parallel) of MPPT controller is not exceeded it will work, but without matching panels not efficiently.

Yes - but "not efficiently" might be an understatement especially with panels in parallel. If the max power voltages are significantly mismatched then it might be that the panel with the lower voltage is doing absolutely nothing.

[smileypete]

How many panels would you like to add?

 

What's the voltage and power of the existing ones, also any more info like make & model, Vmp, Voc, Imp?

 

Are the stick on ones likely to be partly shaded from the sun any time by stuff on them or next to them?

 

cheers, Pete.

~smpt~

Edited October 8, 2014 by smileypete

[Alf Roberts]

Perhaps three extra panels in series with the existing panels then 3 strings in parallel would give the best outcome.

 

Though it may be best to get a second controller for the 240W and then use the 30A Tracer for one or two 250W panels

Edited October 8, 2014 by Alf Roberts

[Detling]

You could use a tracer 20 amp for the existing panels and put the new ones through the 30 amp controller, these should work together with no problem. As stated earlier the current from a string of panels in series will be limited to the lowest rated panel in the string, Different panels types will produce different voltages in the same conditions and if you put the panels in parallel the highest voltage panel will power the system and the lower voltage panel(s) will just be ignored.

 

Two controllers onto the same battery bank have the possibility of one 'trumping' the other when the SOC is 90% + as one controller could output say 14.3 volts and cause the other controller to think the batteries are full and stop charging. This depends on the controller program and two from the same manufacturer is probably as close as you will get, remember this will only be an issue for the last few percent of charge anyway.

 

Tracer controllers are rumoured to be happy with a slight overload in watts/amps terms but to die instantly if over voltage is applied. I have 300 watts connected to my tracer 20 amp unit an it has survived the summer well max current seen has been 17.7 amps but I don't sit and watch it. The panels are fixed flat so won't get to max output unless I move a long way south or tip the boat at silly angles.

 

Max voltage out of a solar panel occurs at peak sun level when the panel is cold, not an easy combination anywhere but a cloudy morning after a frosty night with the sun bursting through near midday in April/May is probably about the worst.

[Alf Roberts]

 

Tracer controllers are rumoured to be happy with a slight overload in watts/amps terms but to die instantly if over voltage is applied. I have 300 watts connected to my tracer 20 amp unit an it has survived the summer well max current seen has been 17.7 amps but I don't sit and watch it. The panels are fixed flat so won't get to max output unless I move a long way south or tip the boat at silly angles.

 

 

Myth. This, from the Tracer 4210/15 manual;

 

Protections, Troubleshooting and Maintenance 5.1 Protection

 

·PV Overvoltage

If PV Overvoltage occurs, the array will remain disconnected until the voltage falls safely below the maximum rating.

 

My understanding if over current is the same (flattening the bell curve) but the warranty says it's not covered - though over voltage is not mentioned.

[pearley]

if your new panels are the same nominal voltage (ie 12V) the you can add similar in series.

Check whether yout 30A tracer is the 100V max or 150V max one, both are sold sometimes by the same suppliers, and sometimes the wrong ones are sent out.

It is the voltage that is the critical amount, and excess can blow the controllers internal fuses and worse. We are now coming to the time of year when peak voltages start to occur, low temperatures and strong sunshine.

The manual states 150 volts.

Perhaps three extra panels in series with the existing panels then 3 strings in parallel would give the best outcome.

 

Though it may be best to get a second controller for the 240W and then use the 30A Tracer for one or two 250W panels

No room for panels that large. That is why I was hoping to stick with 80 watt panels has I can fit them on the roof box.

 

The existing panels are not shaded in any way, provided I don't moor under trees. I'm trying to get the spec of the existing ones from the supplier. Otherwise I'll have to unscrew one from the roof as I'm sure there is a sticker on the back.

[smileypete]

Well maybe get another 3 panels of the same voltage (Vmp), put them in series, then combine the two 'strings' in parallel. If there's not space for 3 more panels then plan B could be to get two more of the same voltage say, then put all 5 in parallel.

 

Vmp means voltage at max power, and shouldn not be confused with Voc which stands for Voltage open circuit. Make sure that the Vmp of old and new panels match within a volt or two, should be quite doable if the existing ones are a common voltage like 18V Vmp.

 

cheers, Pete.

~smpt~

Edited October 8, 2014 by smileypete

[pearley]

This is what I've found so far:

 

Power max: 80w

Open circuit voltage(Voc): 20.7V

Optimum power voltage(VMP):18V

Short circuit current(Isc): 4.95A

Max operating current(IMP): 4.45A

tolerance:+_5%

Maximum system voltage:600V

[Alf Roberts]

Maybe this wants its own thread but I've been playing with the Tracer's night mode. I have set up a two way switch so I can connect one of my lighting circuits to the tracer load output. If I'm away I can set it to switch that lighting circuit on ( obviously with a number of LED lights switched on). It comes on for 5 hours after sunset and 2 hours before sunrise so the boat seems occupied.

 

I could even envision a radio or TV too.

[matty40s]

Maybe this wants its own thread but I've been playing with the Tracer's night mode. I have set up a two way switch so I can connect one of my lighting circuits to the tracer load output. If I'm away I can set it to switch that lighting circuit on ( obviously with a number of LED lights switched on). It comes on for 5 hours after sunset and 2 hours before sunrise so the boat seems occupied.

 

I could even envision a radio or TV too.

I have been recommending people that I install for that this is the only logical use of the load function on the tracer and similar controllers.