how do I know its a 24 volt panel.

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Kappy
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how do I know its a 24 volt panel.

Post by Kappy »

I've been looking looking at adding some extra 24 volt panels.

Currently I have 600 watts of 24 volt panels ,below
DSC_0174.JPG
Some advertised are a tad confusing
250w 24 /12v solar panel, just add PMW or MPPT regulator 15 amps 12v and 8 amps 24v to charge what ever voltage, we sell the whole range of factory seconds and new in solar panels and batteries 176L x 100w x 4cm 15 kg
TN250M-60 (480x640).jpg
or
Topsola.jpg
Just asking
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Re: how do I know its a 24 volt panel.

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K
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JohnM
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Re: how do I know its a 24 volt panel.

Post by JohnM »

From what I can see, all the above panels are 24v with an MVP of around 30v whereas a 12 v Panel would have a MVP of around 18v.
I would endeavour to match your existing panels even to brand, if you intend to add them in the same array, this would probably be a bit excessive, and probably just matching, Current, Voltage and short circuit current, would be sufficient, but this can lead to panels that are a different physical size. which in my mind suggests different statistics, (regardless of what is written) I believe there are different ways of measuring the output, based on the temperature of the panels. used by different manufacturers.
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Re: how do I know its a 24 volt panel.

Post by Greynomad »

Easy:
1. Stick the panel in a sunny spot.
2. Take the black lead and stick it in your left ear.
3. Take the red lead and stick it in your right ear.
If you get a tickle, it's 12v.
If you get a migraine, it's 24v!
:lol: :lol: :lol: :lol:
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Re: how do I know its a 24 volt panel.

Post by BruceS »

Good to see you're feeling much better Ray!!
I have 48V & tried your method ............ got raced off into the bedroom.... thanks!!!
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Re: how do I know its a 24 volt panel.

Post by T1 Terry »

OK, the first label, Suntech, are household grid connect type panels, the second 2 labels identify them as 24v panels. A 12v panel will have Vmax (Vmp) of around 17v or even 16v, the voltage open circuit (Voc) will be around the 20vdc mark.
The first lot of panels will require an MPPT controller, they will need to be in parallel as the combined voltage of all the panels in series will be to great from the controller (3 x 45.5v = 136.5v) unless you have a controller rated at 150v/30 amps. If you have, then you can still use the panels you have and try running a second controller for the other panels, maybe they won't fight.......

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Re: how do I know its a 24 volt panel.

Post by Kappy »

T1 Terry wrote:OK, the first label, Suntech, are household grid connect type panels, the second 2 labels identify them as 24v panels. A 12v panel will have Vmax (Vmp) of around 17v or even 16v, the voltage open circuit (Voc) will be around the 20vdc mark.
The first lot of panels will require an MPPT controller, they will need to be in parallel as the combined voltage of all the panels in series will be to great from the controller (3 x 45.5v = 136.5v) unless you have a controller rated at 150v/30 amps. If you have, then you can still use the panels you have and try running a second controller for the other panels, maybe they won't fight.......

T1 Terry
Are you saying a combination of 3 Suntech and maybe 3 others won't work together.

I have to get a new controller or 2. and believe MPPT is the go

If the Suntech is a household grid connect type panels, does that mean its not usable on an RV?

I'm contemplating 4 of these 185 watt panels seem a little more compatible with the Suntech I already have.
185 watt panels.jpg
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Re: how do I know its a 24 volt panel.

Post by T1 Terry »

If you really want to use these panels you will need to go MPPT, but either controllers that are linkable in a master/slave combination or a very high input voltage and high output current (amps) as individual low cost MPPT controllers will not work together on a single battery and most definitely will not work together on a lithium battery unless you add some sort of interface to fool the controllers into thinking they see a much lower battery voltage than they would see if connected the normal method.
As an explanation of why this happens, each controller must know the solar input voltage and the battery voltage, either via a look up table or via a calculation the controller determines the best combination to use in an attempt to create the best charging balance. To get a true solar voltage the controller must disconnect the battery to see open circuit voltage to determine that it should turn on, no point in turning on when there is no sun. Then it must disconnect the charging and read the settled battery voltage to determine what the ratio between solar voltage when loaded to battery charging voltage should be, no point in aiming for 14.8v if the battery is at 11v. Once the unit is operating it will continually test for the best solar loaded voltage within its operating parameter and checking the battery disconnected voltage to see how the charge curve is progressing and make the necessary adjustments. Here lies the problem, each controller can only turn its own charging off if it is not linked to the other controller, so the controller testing battery voltage sees the voltage on a charging battery, not a battery at rest, then makes the incorrect calculation because the input information was wrong. Eventually one controller will see a battery voltage it determines is a fully charged battery voltage and drop into float mode, the other controller will see a lower voltage when sampling and take over....... half the solar charging capability just shut down for the day. The old trick was to drop a load on the battery so its output voltage dropped below 12.4v and the controller would go back into float. Lithium batteries will not drop their voltage that low unless they really are flat, they will hold better than 13v during normal operation, the controller sees this as fully charged and remains in float mode.
With programmable MPPT controllers silly return to boost voltages can be established, fine for a continuously loaded system but death for a lithium battery system parked up at home without being used.

If you thought the 12v PWM control system was too complex to get your head around, you have a world of pain ahead of you if the plan is to go 24v lithium using MPPT controllers....... or big $$ for controllers that can actually work together, over $1,000 each and then add the network hardware and software required.
The MPPT choir sing a tune that all is well, anyone who has the knowledge to actually test how their system is operating will tell you they have realised the error of their ways and either spent mega $$ to utilise the $$ they have already spent on the solar, or were fortunate enough to be able to rewire their solar and return to PWM control.

T1 Terry
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Re: how do I know its a 24 volt panel.

Post by SteveW »

Bloody Hell. When my time comes I'll be going to the expert - the expert who knows what he is doing. AGMs are going on for 4yrs and still OK so you will be able to finish Rustic Inn before I come knocking.

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Re: how do I know its a 24 volt panel.

Post by T1 Terry »

SteveW wrote:Bloody Hell. When my time comes I'll be going to the expert - the expert who knows what he is doing. AGMs are going on for 4yrs and still OK so you will be able to finish Rustic Inn before I come knocking.

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As long as they still do what you want done there is no point in changing to lithium, unless weight is the issue. As for having "Rustic Inn Perfection" finished, well... maybe :lol:
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