How to unregulate solar panel

[adrian5800 Advanced Member Find all posts View Profile Close adrian5800]

I tested the cranking battery and it was reading 16 volts! I then disconnected the solar panel and the crank battery immediately dropped to the 12 volt sort of range. Why is the crank battery being charged when my solar panel is hooked up and why is it receiving 16 volts?

Because your solar panel is connected to the start battery unregulated

[danestead Junior Member Find all posts View Profile Close danestead]

Are you sure it's a changeover relay you have there? Do you have 2 terminals marked 87 or one 87 and one 87a? The solar panel should be connected to 87a (centre terminal on a changeover relay or normally closed) and the red input to the BCDC is connected to 30, start battery goes to pin 87 - normally open.
So the solar panel is connected to the BCDC until the ignition is on then the changeover relay disconnects the solar and connects to the start battery with the engine running. I'm sure your panel and BCDC are working fine just the relay connections need looking at.
The minimum voltage req by the BCDC should be the Voc (volts open circuit) rating of the panel not the under load figure.

I'm just out at lunch but b4 I left home I checked the relay wires again and I think I have 2 of them around the wrong way. I'll fix it later today and hopefully everything will work. I am a spastic but tbh, the wiring diagram is a little confusing as I think it's drawn upside down. Without reading the terminal numbers it is easy to wire it the incorrect way that I did. There's also 2 wiring diagrams. 1 as part of the 1225 manual and 1 specific to the relay kit 1260. I followed the 1225 diagram and the purple and red wires look the same colour (when printed on my printer anyway) and it doesn't show the terminal numbers on the relay. Anyway, it seems there is light at the end of the tunnel.

[danestead Junior Member Find all posts View Profile Close danestead]

Problem fixed.

I had the 2 wires around the wrong was as I mentioned in the above post. I am now receiving over 20 volts open circuit/input voltage and the redarc is charging the battery. I apologise for my stupid screw up but as mentioned above, it wouldn't surprise me if others had made the same mistake due to the wiring diagrams being easy to misinterpret.

I've now hooked up 2 fridges and I am going to run the battery down enough so that the redarc calls for maximum charging in boost mode (solid boost light). I will then test the charging current of both the Redarc 1225 MPPT charger and also the Projecta PWM controller. I will then know which is better (based on the sunlight at testing). I've been told the Redarc MPPT is not all that efficient and I've also been told that because my solar panel is only 120w, the PWM will charge better than the MPPT. I find that hard to believe based on my reading but the proof will be in the testing in an hour or 2.

Thanks guys for the help and once again I apologise. This is the exact reason I always finish a project like this then tell myself that I will just pay someone who knows what they are doing next time!

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

All good! Don't worry we are all dyslexic sometimes. Fixed!!!!

There is a lot of satisfaction doing this stuff yourself and based on work I have had done in the past at least you can work it out if something is awry.

[danestead Junior Member Find all posts View Profile Close danestead]

I've just compared the PWM vs MPPT output.

It was 5.30pm and it was hard to get comparable readings because in the 3 minutes it took me to change over the regulator, the output would already drop.

Both the PWM and MPPT were putting out within 0.1 amps of each other at around the 2.4 amps mark. I tested the short circuit amperage and it was within about 0.05 of this also. It's worth noting that I got a short circuit amps of 7.45 at midday today, so there is a lot more power left in this panel if the sun is bright.

I'll test again at midday tomorrow to get a more meaningful representation of which regulator is better.

[danestead Junior Member Find all posts View Profile Close danestead]

For those interested.

I've just tested the PWM and MPPT regulators again in 3pm Perth sun.

Projecta stock PWM reg 5.25 amps.
Redarc BCDC 1225 MPPT 5.17 amps.

TBH, all tests I've done at varying times of the day (no clouds or shading on any of my tests), the Projecta PWM reg has put out more amps. Very interesting and that agrees with some of the info I had been given from other people in the know.

I'm a little disappointed in the Redarc unit as it is referred to as a premium product however it just does not come up with the goods in terms of solar for my application.

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

Interesting result, from what I have read MPPT is better in cloudy/not full sun conditions.

[Anthony K Lurker Find all posts View Profile Close Anthony K]

Hi Leigh

As the Managing Director and Owner of REDARC I feel compelled to respond to your comments as have been highlighted to me as inaccurate by numerous customers.

Firstly the statement that you make above is untrue.

REDARC DCDC chargers are designed for use with any brand of panel.

All solar panels produce a relatively high open circuit voltage (OCV) compared to their maximum power voltage (point at which the greatest power is produced by the panel).

The job of the solar regulator is to accept this high voltage on its input and apply an appropriately lower output voltage for charging the battery.

Generally, most 12V nominal panels will have an open circuit voltage upwards of 22V, this will depend on panel construction and cell type.

The maximum power point of the panel is lower than the open circuit voltage but higher than the required battery charging voltage. Maximum power is produced from the panel generally upwards of 16V.

There are two ways that solar panel regulation is achieved:

Pulse Width Modulation Regulator (PWM)

• Connects panel directly to battery through the regulator until required maximum battery voltage is achieved
• Switches panel on and off to control battery voltage from increasing any higher
• Essentially acts as a “brake” between the panel and the battery, to allow the charge from the panel to the battery by limiting it
• PWM is a lower cost device and less efficient than an MPPT regulator
• The panel does not operate at its maximum power point so it cannot deliver the panel’s full potential power capacity

Maximum Power Point Tracking Regulator (MPPT)

• Simulates a load to the panel to hold the voltage and current at the maximum point of the two values multiplied (Power = Volts x Amps)
• The voltage and current from the panel is converted to the required levels for the battery by a voltage converter
• MPPT is a higher cost device and more efficient than PWM. Full potential power can be extracted from the panel and delivered to the battery.

All MPPT regulators, including the BCDC, aim to regulate the panel at its maximum power point at all times. This point will shift with light intensity and panel temperature. It will also be different for different panels.

The difference between the range of MPPT regulators is the speed at which it can track the moving maximum power point, and the efficiency with which it delivers the power to the battery. Additionally the charge profile that the regulator uses to charge the battery will be different.

If a panel does not achieve a sufficient open circuit voltage to engage the MPPT regulator, then there may not be enough power to actually charge the battery. This can be caused by a lack of light on the panel or even a panel or wiring issue. Before the BCDC starts charging from a panel, it is measuring the panel’s OCV. A 12V nominal panel with OCV less than 17.5V is likely to be faulty or in low light.

There are a number of functional observations you will note when testing:

• The OCV of the panel will vary with light conditions, and potentially throughout the circuit if there are high resistance connections (may be within the panel itself, a cell connection for instance). This is measured at the panel, with the panel disconnected
• The most reliable test for a panel is to measure the short circuit voltage. This is usually marked on the panel (as Isc or similar). To measure, connect a (suitably rated) multimeter set to amps connected straight across the panel. A 100W panel in full direct sunshine should measure around 5.8-6A. A panel with joint or wiring issues will measure far less or 0A, even though its OCV may be a reasonable voltage.
• The maximum power point of the panel will be measured when the panel is connected to an MPPT regulator and it is charging
• The turn on point of the MPPT regulator needs to be above the voltage where sufficient power is available from the panel and below the OCV to ensure that it turns on reliably

Specifically regarding the REDARC BCDC MPPT (from the instruction manual):

• The OCV needs to be above 17.5V to begin charging (tested every 100 seconds)
• Charging will not occur if the OCV is below 17.2V (tested every 100 seconds)
• Charging will not occur if the OCV is above 28V (tested every 100 seconds)
• During charging the BCDC will charge until the maximum power point of the panel is below 8V (under load, tested continuously)
• Will regulate at the maximum power point of the panel at all times during charging and apply a 3 stage charge profile to the battery
• Will work with any 12V nominal solar panel that meet these OCV thresholds

Should anyone have a question please do not hesitate to call us on 08 8322 4848 or email us on [email protected] for FREE technical support by our qualified staff.

Best regards

Anthony K

[Symo Advanced Member Find all posts View Profile Close Symo]

Interesting result, from what I have read MPPT is better in cloudy/not full sun conditions.

No, an MPPT converts the excess voltage above the battery to amps for charging. That is all, only works when there is more voltage, this only happens with more sun.

If the panels are producing 16v and the battery is bulk charging at 14.4v then the difference 16/14.4 = 1.11 so on a 120w panel the charge amps can go from 5.5A to 5.5x1.11 = 6.1A

The more volts the panels can make, the better off you will be with an MPPT, on cheap panels like mine which produce 16v or less the benefit is nill, my PWM will produce 6.5A, and MPPT will only add 0.5A or so, not worth $300 for that, I'd rather buy 1 or 2 more cheap 120w panels and hook them all to my 30A PWM and take off 15-18A.

The MPPT will only work in bulk stage, so with most people you leave for a trip with full batteries and plug your solar in day one, the solar is going to absorb and float which is high Volts low amps and has no benefit over PWM.

[Symo Advanced Member Find all posts View Profile Close Symo]

Hi Leigh

As the Managing Director and Owner of REDARC I feel compelled to respond to your comments as have been highlighted to me as inaccurate by numerous customers.
Should anyone have a question please do not hesitate to call us on 08 8322 4848 or email us on [email protected] for FREE technical support by our qualified staff.

Best regards

Anthony K

Even still, you'll get more amps from two cheap 120w ebay panels and 1 good PWM, PWM is proven reliable technology and is half the price of MPPT.

1x Redarc BCDC sham device and 1x redarc panel $800-$1000 (total 6-7A total output from one panel)
2xebay 120w panels and 1x quality PWM $400 and 15A output...

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

No, an MPPT converts the excess voltage above the battery to amps for charging. That is all, only works when there is more voltage, this only happens with more sun.

If the panels are producing 16v and the battery is bulk charging at 14.4v then the difference 16/14.4 = 1.11 so on a 120w panel the charge amps can go from 5.5A to 5.5x1.11 = 6.1A

The more volts the panels can make, the better off you will be with an MPPT, on cheap panels like mine which produce 16v or less the benefit is nill, my PWM will produce 6.5A, and MPPT will only add 0.5A or so, not worth $300 for that, I'd rather buy 1 or 2 more cheap 120w panels and hook them all to my 30A PWM and take off 15-18A.

The MPPT will only work in bulk stage, so with most people you leave for a trip with full batteries and plug your solar in day one, the solar is going to absorb and float which is high Volts low amps and has no benefit over PWM.

Based on my real life experience using my panel in shade with both MPPT and PWM, the MPPT charges better. Might be just quality of the unit but that's the result.

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

If I'm reading the reply from Redarc correctly the BCDC can not be used in shade because the OCV drops causing the unit to shut down.

I often camp in shade and my panels keep charging my battery, it's really a must have.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Hi Anthony,

Firstly"• The most reliable test for a panel is to measure the short circuit voltage. This is usually marked on the panel (as Isc or similar). To measure, connect a (suitably rated) multimeter set to amps connected straight across the panel."

I believe you meant "short circuit current" not voltage as above

Secondly:

You stated "REDARC DCDC chargers are designed for use with any brand of panel."

Then "• Will work with any 12V nominal solar panel that meet these OCV thresholds"

So to clarify, your chargers will work with any panel that meets the input requirements of your chargers

Thirdly:

I wouldn't necessarily agree with part of your statement that "if a solar panel that generates an OCV of less than 17.5V is either probably faulty or shade" it would appear your assuming that the panel has 36 cells in series, this may not be the case, in the Projecta blanket mentioned above they use a very compact regulator and they may have intentionally specified that the panel produce less voltage to reduce heat dissipation in the regulator, I have also seen some budget 12V that panels that generate lower voltages than would normally expect to see. A quick check of Ebay shows the first 120W panel listed to have an OCV of 20V, it would be interesting to see what the OCV of this panel would be on a hot sunny day?

Regarding the rest, please don't shoot me I'm only the messenger, it is your customers that are complaining. I have no personal experience with this issue just repeating what has been posted by others regarding the same. The following are a few of post I have come across regarding this issue:

"Hello all,

I have a Redarc BCDC1225 installed providing charge to a battery under the rear seat of my 2013 BT50.

I have tried connecting 120w Projecta folding panels (unregulated) to the Redarc but get no charge. Read the manual and says needs 17.49v is this correct? My watt meter indicates 17.29v so is the solar not giving enough oomph?

Are there any implications if I was to connect regulated solar direct to this battery?

Cheers
JonnyB"

"Get the Projecta reg and connect direct to your battery per the instructions, oh and don't share an earth, make sure the panel input is its own floating earth

If I had the choice I would not have the redarc at all, expensive paperweight"

"The bottom line is, they are designed to use redarc panels, anything else is a lottery. Since disconnecting mine and installing the projecta my batteries are back to 13.8 and floating before 11am under a polycarbonate roof. In the same conditions when the redarc actually worked a bit the max I got was 13.2, which slowly deteriorated to not charging at all.

Expensive paperweight for solar purposes without redarc panels, would not buy again"

"Quote from: oldmate on January 05, 2016, 06:55:28 PM

My solar works fine in my redarc 1240. Projecta 120w blanket.

And mine did also for a while, then after a few months, nothing."

"Did you talk to Redarc about it? Warranty??

Yep, no warranty unless using redarc panels"

"My panel isn't projecta, but yes it dipped below the minimum voltage and stopped working after 3 months.

Works perfectly with the projecta charger though

They don't have to say that, because they do work with other panels, just not mine, or a few other LCT customers, and others. But they "definitley" work with Redarc panels "

"Ok, so finally rang Redarc and after consulting two of her colleagues was told that yes 17.50V is correct and that a 120 watt panel should be putting out around 20-22V up here in our NT sun.

I mentioned that the glossy said solar input of 9-32V and things went very vague and decided to leave it there after being told that my panel must be faulty.

I was using an unregulated Projecta folding 120w panel from Jet, does 20-22V sound right?

JonnyB"


As you can see there is a lot of debate regarding your mppt charger, I will also point out that there are a lot of post by others indicating that they have had no issues and the chargers work fine, a mixed bag to say the least.

Your glossy for your charger 40A charger states:

DC input voltage range 9V-32V (9V-28V for Solar)

Without having read the user manual my interpretation of the above would be that the unit will operate on any supply voltage within the range of 9V-28V and I'm sure most others would agree with me. Maybe more detail should be provided in the glossy as per the user manual?

It is good though to see the mnaufacturer addressing concerns about his product, perhaps you can provide some detailed infromation regarding the following:

What are the exact input conditions that must be meet before the charging will start charging, you have indicated 17V approximately but is there a minimum current the panel must be able to supply at this voltage for the charger to trigger, ie what load does the charger apply to the panel when determining the minimum voltage input is available?

Personally I would have thought the charger would do a check of available power output from the panel rather than voltage and as long as there is sufficient "power" available to use for charging start charging regardless of input voltage. In the case of the Projecta panels above it seems in some cases even under bright sunny conditions the panels don't generate the required 17V+ to trigger the charger yet when used with their own regulator quite happily charge at 8 amps plus. I have one of the solar blankets mentioned above and over the next few days will do some testing to see what voltage the blanket does actually generate under various conditions.

Regarding mppt chargers being more efficient, maybe when used with high ouput panels with good head room, but with regards to 120W and smaller panels I have found through personnal experience that good quality PWM regulators provide more charging current than good quality mppt chargers when running off the same panels under the same operating conditions.

Cheers
Leigh

[Symo Advanced Member Find all posts View Profile Close Symo]

Based on my real life experience using my panel in shade with both MPPT and PWM, the MPPT charges better. Might be just quality of the unit but that's the result.

Yes, because as long as there are more volts on the panel the MPPT will convert them to amps, the PWM will not. This not a case of MPPT is better in the shade, but MPPT is better as long as you are bulk charging stage and there are excess volts at the panel, irrelevant if where you hide your panel.


Sent from my iPad using Tapatalk

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

The panel could also affect the results, if the panel has plenty of volts to trade then yes, some smaller panels though may not have sufficient "head room" to allow the mppt to function at peak efficiency.

Personnaly I too have found with small 120W panels in overcast and hot conditions, that my PWM's regulators provides more charge current than my mppt charger.