adding a 320w panel to a 160w system

[leesmith2097]

Hi

I have 1 x 160w solar panel which is about nearly 9 amps max, the max voltage must be about 18v.

Its connected to a 20amp MPPT and PWM charge controller with a 12v 120ah leisure battery.

The power rating of the cables from the charge controller to the battery are 10 AWG which carry up to 20 amps at a high voltage.

I am abit confused with my current setup first of all so bear with me in terms of all the questions

1) if the battery is 12v but the solar panel is capable of 18v, does that mean it can only charge at a max of 12v x 9 amps = 108watts which means im losing 52 watts in direct sunlight?

2) if I want to add an additional panel which is 320w im assuming I need to add it in a series and consider the max voltage of the mppt / pwm charge controller which I think is 48v. If I did do it in a series i would only get the max amps of the 160w panel because the 320w is 10amps, the 160w panel is 9 amps, but would get the voltage of both which is about 18v + 32v = 50v.

3) im assuming the 320w panel volts would be 35.5v though if you divided 320 by 9 amps would be 35.5v?

4) could I just buy another mppt charge controller to run the 320w panel separately? then connect both charge controllers to the 12v battery? (ive read this would work)

my main concern is all this extra voltage and the battery is only 12v, i want to make the most out of the system.


any assistance with me adding the 320w panel would be great. I am wanting to add another panel, make the most of the amount they can produce and also add an ongrid inverter eventually.

 

[HRTKD]

Your controller is either MPPT or PWM, not both. I have both in my RV, but I know more about MPPT so I'll answer assuming the use of an MPPT controller.

1. The controller will never output more amps than it is rated for. The voltage of the solar panels doesn't matter. The controller converts the incoming volts and amps to values that agree with your battery system.
2. It's up to you to install a controller that won't charge with too many amps.
3. Combining panels of different specifications usually doesn't work out well, especially when they have very different specs. Look up the YouTube videos by the Alt-e store on combining panels of different specs. It's very helpful and explained well.
4. Using a separate charge controller is probably the way to go. But take into account the max amps that the two controllers combined can produce. The caveat to that is that they may not play well together. On my RV, if the 45 amp AC-DC converter is on and cranking, the PWM controller pretty much shuts down (goes to zero amps output). On my LiFePO4 side, I have two Victron Energy MPPT 100/50 controllers and they do work well together.

 

[leesmith2097]

Your controller is either MPPT or PWM, not both. I have both in my RV, but I know more about MPPT so I'll answer assuming the use of an MPPT controller.

1. The controller will never output more amps than it is rated for. The voltage of the solar panels doesn't matter. The controller converts the incoming volts and amps to values that agree with your battery system.
2. It's up to you to install a controller that won't charge with too many amps.
3. Combining panels of different specifications usually doesn't work out well, especially when they have very different specs. Look up the YouTube videos by the Alt-e store on combining panels of different specs. It's very helpful and explained well.
4. Using a separate charge controller is probably the way to go. But take into account the max amps that the two controllers combined can produce. The caveat to that is that they may not play well together. On my RV, if the 45 amp AC-DC converter is on and cranking, the PWM controller pretty much shuts down (goes to zero amps output). On my LiFePO4 side, I have two Victron Energy MPPT 100/50 controllers and they do work well together.

Hi

Thanks for responding

I'm still a little confused

So the mppt controller instructions says it's mppt pwm mode.

I agree it will only charge what the battery can go at that makes sense, but what does it do with the excess volts? Is this why there is load on the controller?

The charge controller i believe can only support 48v max so i Darent add the 320w solar panel to the existing 160w.

The amps on the 160w panel are about up to 9 amps. On the 320w its 10.27 so I would lose an amp putting them in series, but the volts would exceed.

It makes sense what your saying about the max they can both produce. My thought was if they are both 20 amp controllers and like i say 1 panel is 9amps and one panel is 10 amps then this should work ok.

If i found a controller that supported 20 amps and 60v I'd be fine using 1 controller?

Thanks

Lee

 

[HRTKD]

Hi

Thanks for responding

I'm still a little confused

So the mppt controller instructions says it's mppt pwm mode.

I agree it will only charge what the battery can go at that makes sense, but what does it do with the excess volts? Is this why there is load on the controller?

The charge controller i believe can only support 48v max so i Darent add the 320w solar panel to the existing 160w.

The amps on the 160w panel are about up to 9 amps. On the 320w its 10.27 so I would lose an amp putting them in series, but the volts would exceed.

It makes sense what your saying about the max they can both produce. My thought was if they are both 20 amp controllers and like i say 1 panel is 9amps and one panel is 10 amps then this should work ok.

If i found a controller that supported 20 amps and 60v I'd be fine using 1 controller?

Thanks

Lee

There are a lot of really cheap controllers out there that SAY they are MPPT, but under the covers they're really PWM. It's not necessarily a bad thing (as long as you paid a PWM price and not an MPPT price), just misleading.

Don't worry about the voltage of the panels if you are using MPPT controllers. I have a 12v battery bank and my panels produce 80 volts. The MPPT solar charge controller takes the incoming 80 volts and 9 amps and converters that to ~14 volts and 50 amps. The only time you have to worry about the voltage of the panels is to ensure that you don't exceed the Max PV Input Volts spec of the solar charge controller.

If the charge controller decides that the battery is fully charged then it simply doesn't let any more power come in from the solar panels.

 

[chrisski]

In my signature block you’ll see a link to mismatched panels.

I don’t think what you’re doing will work. At best with two in series, you’ll match the output of a single 320 watt panel. THat link will say what happens when you mismatch wattage and voltage.

The only reason this could work if is both panels were the same voltage (They’re not) and then it could be placed in parallel).

For your controller, if you look at the input voltages for 12 volt and 24 volt, MPPT has a wide range. My 4 MPPTs to start charging have a SCC to battery voltage + 5 volts to 100 volts. My PWM is about 17-24 for a 12 volt system and 33 - 44 volts for a 24 volt system.

If your controller’s input matches what I put for PWM, than it most likely is a PWM SCC, even though the company called itself or that line of SCCs a MPPT. I consider that misleading advertising.

 

[leesmith2097]

That's great advice thanks both.

I'm now questioning if it's a pwm controller because it was only about 10 pounds from China lol. Will that be an issue with the volts? I've attached the tech sheet.

I would be willing to upgrade my battery to 24v system if needed.

I want to get the most out of the 160w panel but also add 320w panel.

The volts is i think around 18v on the 160w panel. The spec of the 320w panel im looking at is here

https://www.ebay.co.uk/itm/Solar-Pa...p2349624.m46890.l6249&mkrid=710-127635-2958-0

Any assistance is appreciated. I thought because both amps are nearly same if i lost an amp because it goes off the lowest I'm happy to have 9 amps instead of 10 and run at 18v plus the new volts which I think is 40v. I don't think the controller would support the that high?

Still confused a little but im sure from that info you can advise ??

One thing I forgot to add was that the amps when charging the battery doesn't ever seem to go higher than 8.6 amps on a sunny day. It runs at 14v x 8.6 amps which is only 120.4w at best from a 160w panel. Surely amps should be higher?

 

[HRTKD]

24v is the Max PV Input Voltage allowed for that controller when used with a 12v battery. If you connect that 320 watt panel (VOC = 40.60) to that controller you will probably fry it. You need a second controller.

The charge rate you're seeing with the existing panel depends on a lot of things. Full sun, angle of panel, latitude, voltage drop through the cables, state of charge of the battery, etc.

 

[leesmith2097]

Thanks.

If I wanted to make the most out of the 160w panel on the current controller I was thinking if I made my existing 12v a 24v battery circuit then the controller can accept between 36v and 48v but im assuming the 160w panel wouldn't be able to produce that and it won't work because its 18v and 8 to 9 amp?

I'll look to buy a second controller / replace this one.

Do you recommend a MPPT controller over PWM?

Shall I look to replace mine and join the panels in series?

 

[chrisski]

If you want to maximize both panels, you need to get a second SCC, this time a real MPPT controller to tie in that second circuit.

EPEVER makes a more affordable, but Renogy has them also. I use Victron for my MPPT.

The reasons you can’t tie the two panels together as is in the same circuit are in the “Mixing and Moatching Solar Panels Link.” You can, but the results would be wasteful.

Even if your SCC is a PWM, you can hook a second MPPT controller to the battery. Provided your battery max charging amperage is not exceeded, you can add to either SCC with a like panel at a future date. I have three MPPT SCCs on my system.

Guy on a different forum had his trailer solar “Professionally Installed.” Turned out the installer put a smaller helper panel on his system. It was mismatched like yours are. His power production improved when he disconnected the smaller “helper“ panel. That and a few other problems with that installation, he is suing the installer.

THere are times when panels can be mixed together with no consequences, but basically panels need to be reallly close specs to eachother. Most panels marketed as ”100 watt 12 volt” panels can be mixed in series or parallel with little to no real loss, maybe 5%.

EDIT: DON’T PUT THESE PANELS IN SERIES OR PARALLEL ON THE SAME SCC WHETHER PWM OR MPPT. I really think if you do the math, your 320 watt and 160 watt panel in series will make 320 watts total, not 320+160=480 watts.

 

[leesmith2097]

Hi Chrisski

Thanks for the reply.

I did the maths

If you work it out it would go off the lower amp in series so i would lose an amp.

160w / 9 = 17.7v
320w /9 = 35.55v

Total = 53.2v x 9amps = 337.66watts

I'll buy a seperate charge controller lol your right

So to make the most of the 160w panel should I put a 24v system in? Will that get more from the solar?

Will the solar charge it being that the solar only produces like 18v?

 

[chrisski]

Good think about that second SCC is once those panels have been up for a while, if you are not happy with the charging of the battery, you can add a more panels in series or parallel.

Also, mine is a mobile installation and one of my three SCCs is for ground portable panels. Because I point and angle these to the sun three times a day, the SCC that has the portable panels puts out more than the other two combined despite it being less than half the watts.

That second SCC gives you many options.

 

[leesmith2097]

That sounds good.

I just need to make sure I get the correct mppt then? I think what I have is an mppt but im not sure of the difference. If i bought a pwm by accident would this still work as a 2nd one? Whats Scc stand for? Solar charge controller?

So to make the most of the 160w panel should I put a 24v battery system in? Will that get more from the solar panel? Will the solar charge the battery being that the solar only produces like 18v?

I do have another seperate question, do you have experience in a tie in grid inverter that will charge my battery but also put back into the grid?

Thanks for your help

 

[HRTKD]

SCC = Solar Charge Controller. Acronyms used in the forum can often be decoded using this document.

PWM or MPPT will work as long as the Max PV Input Voltage of the solar charge controller is greater than the Voc of the solar panel.

I don't think going to 24v is going to do you one bit of good at getting more out of your 160 watt panel. If you're not maxxed out already in a 12v system, then a 24v system isn't going to do any better.

 

[leesmith2097]

Thanks

Only thing that confuses me is that the charge controller will only charge the battery at 14v, its a 20 amp mppt but if the solar panel max amps is lets say 9 amp then it isn't going to produce more than 14v x 9 amps = 126 watts out of the 160w panel.

If the panel is 9 amps and your telling the controller to charge the battery at 14v then missing those extra volts the panel produces if its rated at 17.7v 9 amps.

Increasing it to a 24v circuit would allow up to 24 volts as the panel produces 17.7v, that correct?

I hope that makes sense.

 

[HRTKD]

You have a piece of crap PWM controller disguised at MPPT. Don't expect MPPT results from it.

The 20 amp rating on the solar charge controller is the MAXIMUM that it will ever produce. It will NEVER make those kinds of amps with the 160 watt solar panel you have. You would have better luck launching a Titan rocket with a bunch of bottle rockets taped on the outside.

Going to 24v would be like changing the 4 cylinder engine in a Ford Pinto with a 12 cylinder Jaguar engine, but keeping the existing air intake, fuel system and spark plugs (four of them).

You can't make a silk purse out of a sow's ear. You have low end equipment that isn't going to mix well with higher end, newer equipment.

 

[leesmith2097]

Thanks for your honesty, I was unaware until you have told me.

Would this be an ideal replacement for the piece of crap I have?

MPPT Solar Charge Controller 12/24V 30/50/70A Battery Regulator Dual USB 5V B WS | eBay

Find many great new & used options and get the best deals for MPPT Solar Charge Controller 12/24V 30/50/70A Battery Regulator Dual USB 5V B WS at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

Also for the 320w solar panel would this do the job if I got the 30 amp one?

 

[Whinny]

Your 160 watt panel will not charge a 24v battery-it only puts out 17.7 which is considered a 12v panel. Your inexpensive PWM controller will work fine with it, a true MPPT might gain you 10-15% depending on conditions.
The eBay controller you linked appears to be PWM- a true MPPT will cost closer to this.....but a 30a one would be better for your panel....

SRNE SR-ML2420 20 Amp MPPT 12V / 24V Solar Charge Controller | eBay

Maximum solar input: 260W @ 12V (520W @ 24V). Suitable for 12V & 24V battery systems.

www.ebay.co.uk

 

[HRTKD]

Thanks for your honesty, I was unaware until you have told me.

Would this be an ideal replacement for the piece of crap I have?

MPPT Solar Charge Controller 12/24V 30/50/70A Battery Regulator Dual USB 5V B WS | eBay

Find many great new & used options and get the best deals for MPPT Solar Charge Controller 12/24V 30/50/70A Battery Regulator Dual USB 5V B WS at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

Also for the 320w solar panel would this do the job if I got the 30 amp one?

I can't figure out from the specifications what the Maximum PV Input Voltage is. Maybe it's there somewhere, but I didn't spot it. That's an important detail.

 

[JWLV]

I think the best way to describe the difference between PWM and MPPT in layman's terms is this:
PWM: Voltage in = Voltage out.
MPPT: Voltage in = whatever voltage you set it up for (12v, 24v, 48v).

What that means is if you are using a PWM controller with a 24 volt panel, your battery needs to be 24 volts as well. You cannot use a 24 volt panel and a 12 volt battery with PWM.

If you use an MPPT controller, your panels can be any voltage (within the range of the MPPT controller - usually between 25-100 volts), and your battery can be 12, 24, 48, or whatever the MPPT controller supports. As long as your panel voltage is higher than the battery voltage, it'll work fine. MPPT will convert the extra voltage to usable current to the battery.

 

[leesmith2097]

Thanks JWLV

The current controller I have allows me to set the volts for charging.

I'm assuming for that 320w panel I'll need a 30amp controller? I'm also assuming using a 30 amp charge controller that supports a 12v battery means it will work at 10.6v? or could I use a 20 amp controller as long as it supports the vault which is 320 / 20 = 16v? if this is the case I can pick a few of the cheap controllers from ebay.

If it has to be 30 amps then I will just need to make sure the cable supports 30amps at 10.6v?

what confuses me is the volts can be higher on the solar panel than the battery, but does it mean that it will just reduce the volts to 12v and push more amps when it hits the charge controller to charge the battery? which is why I would need a 30 amp controller?

I know this is cheap but im assuming this would work?

30A Amp 12V/24V Solar Panel Regulator Controller Battery Charger PWM Dual USB UK | eBay

Find many great new & used options and get the best deals for 30A Amp 12V/24V Solar Panel Regulator Controller Battery Charger PWM Dual USB UK at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

Thanks

Lee