Using 36 v solar panel with 12 v battery

[SergioS]

Hi!

I successfully mounted my off grid system with 18v panels (connected in parallel) using the Epever Tracer4210AN and connecting to a 12v Li-On battery. When I built the off-grid system I thought I would have to match the voltage of the panels with the voltage of the battery,

I need to change the solar panels and connect to a new group of panels connected in series and parallel. The panels will deliver 36v can I connect this system (12 v battery)?

 

[rmaddy]

If you use an MPPT solar charge controller you will have no issue. You only need to worry about the voltage being similar with a PWM controller.

 

[Don B. Cilly]

Sure. That controller accepts a maximum Voc of 92.
Just make sure you connect your 12V battery before connecting the panels.

 

[Browneye]

Consider getting the RS485 com cable for the Tracer, download the free app to a laptop or tablet, so you can set your charge parameters on the controller. It also provides a neat data logging section when you're connected.

The XT50 remote display unit will also provide for adjusting charge settings.

 

[MichaelK]

Very doable, though you need to pay attention to different numbers now. The maximal amperage is the amperage put out by the controller, into the batteries, and that is 40A. So, whatever combination of panel strings you make, you don't want to go significantly past 40A. You started out with 18V panels? How many? It is easy to parallel two strings of different voltage panels, as long as the string voltages are the same.

So, for example, let's say you put two 18V 100W panels in series, which will give you ~5.5A at 36V. You could then wire one 36V panel parallel to the string of two 18volters because they are both putting out the same voltage. How many watts is that 36V panel? Let's say for example that it is a 300W panel putting out 8.33A at 36V. So, your two parallel strings would be 5.5A at 36V and 8.33A at 36V, for a total of 13.83A at 36V. That is equal to 498W of panels total. 498W/13V charging = 38.3A. So, that combination would be OK for your controller, because the max amperage is less than 40.

Now, what if you have three 18V panels? Three in series would be 54V, so you could not put that in parallel with one 36V panel. You could wire four 18V panels to get 72V, and wire two 36V panels in series to get 72V, but that combination would make 400W + 600W = 1000W total. 1000W/13V = 76.9A, far higher than the max of your charge controller.

 

[camelCase]

It would be best if you posted a diagram showing all the details of your planed changes including model numbers and wiring, etc.

 

[SergioS]

Consider getting the RS485 com cable for the Tracer, download the free app to a laptop or tablet, so you can set your charge parameters on the controller. It also provides a neat data logging section when you're connected.

The XT50 remote display unit will also provide for adjusting charge settings.

Thanks! I bought some time ago but I'm having trouble with communications with the cable. I'll try with a different computer.

 

[Browneye]

Yeah, you gotta get a open com port that works - mine is on 3.

 

[SergioS]

Very doable, though you need to pay attention to different numbers now. The maximal amperage is the amperage put out by the controller, into the batteries, and that is 40A. So, whatever combination of panel strings you make, you don't want to go significantly past 40A. You started out with 18V panels? How many? It is easy to parallel two strings of different voltage panels, as long as the string voltages are the same.

So, for example, let's say you put two 18V 100W panels in series, which will give you ~5.5A at 36V. You could then wire one 36V panel parallel to the string of two 18volters because they are both putting out the same voltage. How many watts is that 36V panel? Let's say for example that it is a 300W panel putting out 8.33A at 36V. So, your two parallel strings would be 5.5A at 36V and 8.33A at 36V, for a total of 13.83A at 36V. That is equal to 498W of panels total. 498W/13V charging = 38.3A. So, that combination would be OK for your controller, because the max amperage is less than 40.

Now, what if you have three 18V panels? Three in series would be 54V, so you could not put that in parallel with one 36V panel. You could wire four 18V panels to get 72V, and wire two 36V panels in series to get 72V, but that combination would make 400W + 600W = 1000W total. 1000W/13V = 76.9A, far higher than the max of your charge controller.

I'm using 4 panels of 100w. They deliver about 5,5 A each. I think passing the max amperage won't be a problem. Thanks!

 

[12VoltInstalls]

Thanks! I bought some time ago but I'm having trouble with communications with the cable. I'll try with a different computer.

There is an issue with virtual/assigned ports with the newer smoke and mirrors windows shystem. I had a problem and a wiser than me member helped me solve it in that thread. I gave up on being a neo-hacker 20 years ago when I matured enough to realize I didn’t have to conquer everything to be a man… ?‍

 

[Don B. Cilly]

Actually - I have a 30A Tracer3210AN - I could never get the USB cable to work either.
I got the little WIFI box, and that worked.

[EDIT] Actually, the little box only has a phone app for it.
I happen to really dislike pocket computers, especially if I have to type anything in them. I use scrcpy, have the phone screen on the big monitor, and use my full keyboard and mouse with it.
-

 

[MichaelK]

I'm using 4 panels of 100w. They deliver about 5,5 A each. I think passing the max amperage won't be a problem. Thanks!

Is that actually true? In your first post you stated "change the solar panels and connect to a new group of panels connected in series and parallel. The panels will deliver 36v".

This suggests to me that you could either be removing the 18V panels and replacing them with an unknown number of 36V panels, or alternatively adding new 36V panels along side the original panels. Both are still doable, but with caveats mentioned above.

Do you actually mean that you want to re-wire your existing panels to a 2S2P configuration? As camelCase mentions, it would be best if you actually diagramed what is it you are trying to accomplish, so we can best answer your questions.

 

[SergioS]

Thank you all! The system is working well!

 

[SergioS]

There is an issue with virtual/assigned ports with the newer smoke and mirrors windows shystem. I had a problem and a wiser than me member helped me solve it in that thread. I gave up on being a neo-hacker 20 years ago when I matured enough to realize I didn’t have to conquer everything to be a man… ?‍

Thanks! I've tried in different ways but coundn't solve it. I've ordered another cable. I'm gonna try again with the new one.

 

[PVorBust]

Thanks! I've tried in different ways but coundn't solve it. I've ordered another cable. I'm gonna try again with the new one.

How did you go with the new cable? There are some quirks if you are still having problems.

A good start is the OEM serial driver in place of the MS driver

EPSolar AN series to RS485 to Ethernet

I only need ~20’ of distance or so and I’ve got recycled Ethernet cable that is at least that long, so I’m trying to understand whether Ethernet cable can be repurposed for RS485 and what’s needed to do that as easily and cheaply as possible… Yes it should work as long as the cable is still...

diysolarforum.com

for your settings, follow this and make sure "RS485" is checked.

EPSolar AN series to RS485 to Ethernet

I think that might be from the Renogy MT-50 manual ~ My understanding is that they are different and incompatible devices on a number of levels - despite sharing the same name. Ah! that would explain the weird pin numbering in the Renology manual I'd completely failed to notice they are...

diysolarforum.com

 

[SergioS]

How did you go with the new cable? There are some quirks if you are still having problems.

A good start is the OEM serial driver in place of the MS driver

EPSolar AN series to RS485 to Ethernet

I only need ~20’ of distance or so and I’ve got recycled Ethernet cable that is at least that long, so I’m trying to understand whether Ethernet cable can be repurposed for RS485 and what’s needed to do that as easily and cheaply as possible… Yes it should work as long as the cable is still...

diysolarforum.com

for your settings, follow this and make sure "RS485" is checked.

EPSolar AN series to RS485 to Ethernet

I think that might be from the Renogy MT-50 manual ~ My understanding is that they are different and incompatible devices on a number of levels - despite sharing the same name. Ah! that would explain the weird pin numbering in the Renology manual I'd completely failed to notice they are...

diysolarforum.com

Hi!
It took some work to configure but I managed to end up connecting with the new cable.
Thanks!

 

[PVorBust]

Hi!
It took some work to configure but I managed to end up connecting with the new cable.
Thanks!

Excellent. Good to hear.

 

[rin67630]

Hi!

I successfully mounted my off grid system with 18v panels (connected in parallel) using the Epever Tracer4210AN and connecting to a 12v Li-On battery. When I built the off-grid system I thought I would have to match the voltage of the panels with the voltage of the battery,

I need to change the solar panels and connect to a new group of panels connected in series and parallel. The panels will deliver 36v can I connect this system (12 v battery)?

You should put the 36V panels in parallel and the 100W 18V panels in pairs/series to make 36V too.
36V is ideal for a 12V battery with an MPPT controller.
Do NOT use a PWM controller, just dump what you may have.