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Diode help required (Creating solar and 12v charging cable)

TheOtherShiny

New Member
I think I need more information about diodes... I am a complete beginner!

I’m trying to make a charging cable, combining 45V solar panels (Dual sun FLASH 400W) and 12V car charger.
The Ecoflow Delta only has one XT60 connector, and I don't want to keep changing over cables. Solar charging during the day, 12V at other times.

The "Internet" said it's possible to use diodes to protect a 12v system from 42v. I bought some diodes (10SQ050 10A 50V), but still get 42V after the diode, when I connect the solar panel and check the XT60 connector with my multimeter. The XT60 connector is my 12v input so I want to prevent all reverse current (thinner cable).

Since I am combining cables I want to protect the 12v car circuit from the solar panel voltage.

Solar Panel: https://my.dualsun.com/wp-content/u...lSun-EN-Datasheet-FLASH-400-Shingle-Black.pdf

My questions are:
1) Is my limited knowledge of Diodes correct? I am expecting that after the diode the voltage should be 0V in reverse direction and a slight voltage drop in forward direction). I am not seeing the 0V (using multimeter). I have tried multiple diodes (of same model).
2) Do I need a diode on both negative and positive wires (currently I only have hard wired on positive), but have tried adding on negative by hand to check, but no difference.
3) Since I am combining 12v + 42v in the same cable what is the final output? The Ecoflow Delta has a 10 amp limit on the MPPT controller. So what is the result of: 12v (8 amps) + 42v (10amps)?

I hope I have included enough information that someone understands.


Picture shows: 2 x Inputs (XT60 connector from 12V, PV connector from panel). PV connectors for output
diode.jpg
 
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Externet

Well-Known Member
Hi.
I do not see what diodes can do here or why diodes are in this topic.
You need a DC-to-DC converter that will take the 40 VDC from the solar panel and convert to 13.8 VDC to charge the battery.
Seems you have a panel typically used for roof generation onto an inverter, of 72, 144 cells instead of a ~30 cell used for 12V battery charging.

Look for something like ----> https://www.ebay.com/itm/354325899911
 

TheOtherShiny

New Member
Hi Externet,

Thanks for your reply. Apologies if the question was not clear or if it is at a higher level than normal for this forum. It's not a low level electronics circuit issue.

Anyway,

The EcoFlow Delta is an all in one portable battery station. https://eu.ecoflow.com/products/delta-portable-power-station
It has an inbuilt battery, mppt controller and an inverter. Importantly it has two charging sockets. A C14 (220-240Vac) and an XT60 (10-65V DC 10A max) which allows charging either via solar or car charger.

The problem for me is the single XT60 connector. The unit comes with two (adaptor cables). MC4 -> XT60 and 12v cigarette -> XT60. I would like to charge via solar and car charger, so either:
1) I plug and unplug cables from solar and car charger as required
2) Have a switch to select which charging method
3) Hopefully create a cable to charge at the same time (assuming it's possible, and the unit is not overloaded

In answer to your reply I am not trying to change voltages, just protect one charging system from the other)

Connector is MC4. XT60 is used for smaller voltages and lipo battery packs (for model cars and planes) I believe.

It's not clear to me whether combining these two cables (assuming full solar output) will put me over the 10 amp limit
 
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Diodes conduct when forward biased and do not conduct when reversed biased. I see that you understand this. But it means you will see a small forward voltage, a few hundred millivolts, if you measure the voltage across the diode when it is forward biased. But when it is reverse-biased, you will not see zero. That would mean it was a dead short. You will see whatever voltage would be present in the circuit if the diode was missing completely. In your case, this is the solar panel open-circuit voltage minus the battery voltage. Likely tens of volts.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
The photo appears to show the diodes arranged correctly for the lower connector to be the output and the upper two as alternate inputs.

As long as the voltage from the solar panels is higher than the battery voltage, the battery will not contribute any current as its diode will be reverse biased.
(And presumably by the solar panel output drops below 15V, the current available from them will be pretty low).
 

Externet

Well-Known Member
If that portable battery station has a connector that accepts 10 to 65 VDC input; you need nothing to connect such unit to a 12V battery or to a solar panel that yields 40VDC but not both.
If the charging method switch is part of the Ecoflow controls, select depending what source you connect.

If what you want is to have both permanently connected and not select the switch for the working source or swapping cables, you must use the DC-to-DC converter and leave the switch in 12VBat position.

40VDCSolarpanel----------->DCconverter---------->12Vbattery------------->Ecoflow--------->Itsoutletsofchoice

That way no matter what supplies the Ecoflow, it will always be 12VDC from the battery being charged or not by the solar panel at that moment.

Be aware that 12VDC to supply 1KW; the current would be 83 Amperes which I doubt that connector XT60 can handle. Is there a battery inside the Ecoflow ?

Having the diodes as seen on your image will not allow the battery at XT60 to receive charge from the solar panel.
 

TheOtherShiny

New Member
Thank you so much for your time and help on this.
The photo appears to show the diodes arranged correctly for the lower connector to be the output and the upper two as alternate inputs.

As long as the voltage from the solar panels is higher than the battery voltage, the battery will not contribute any current as its diode will be reverse biased.
(And presumably by the solar panel output drops below 15V, the current available from them will be pretty low).
I'm pleased the diodes are the correct way. Thanks for the confirmation. The second statement is interesting and maybe problematic. I hoped that the Ecoflow would charge via solar during the day and then at night the 12v input (car cigarette charger) would take over. But I have tested at night (no sun) and the PV circuit is still 45V. If this is the case (and from your statement) the 12v input will never contribute. I will test this, but I don't want to connect it up until I am sure that the 12v circuit is protected
 
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TheOtherShiny

New Member
If that portable battery station has a connector that accepts 10 to 65 VDC input; you need nothing to connect such unit to a 12V battery or to a solar panel that yields 40VDC but not both.
If the charging method switch is part of the Ecoflow controls, select depending what source you connect.

If what you want is to have both permanently connected and not select the switch for the working source or swapping cables, you must use the DC-to-DC converter and leave the switch in 12VBat position.

40VDCSolarpanel----------->DCconverter---------->12Vbattery------------->Ecoflow--------->Itsoutletsofchoice

That way no matter what supplies the Ecoflow, it will always be 12VDC from the battery being charged or not by the solar panel at that moment.

Be aware that 12VDC to supply 1KW; the current would be 83 Amperes which I doubt that connector XT60 can handle. Is there a battery inside the Ecoflow ?

Having the diodes as seen on your image will not allow the battery at XT60 to receive charge from the solar panel.
Thank you for your time and help also you are helping me to think through this.

Yes there is a battery in the Ecoflow and an inverter. The solar panel is 400W. The input XT60 is actually a car cigarette charger so not receiving charge from the solar panel is exactly what I want! :)

I believe that the Ecoflow can charge at higher rates on solar than with 12V. If I reduce the solar down (which I understand makes it completely safe for what I want) then I reduce the higher rate charging capability. Which I would like to avoid, but might be the compromise.
 

TheOtherShiny

New Member
Diodes conduct when forward biased and do not conduct when reversed biased. I see that you understand this. But it means you will see a small forward voltage, a few hundred millivolts, if you measure the voltage across the diode when it is forward biased. But when it is reverse-biased, you will not see zero. That would mean it was a dead short. You will see whatever voltage would be present in the circuit if the diode was missing completely. In your case, this is the solar panel open-circuit voltage minus the battery voltage. Likely tens of volts.

So this means that my logic and use of multimeter is incorrect? (caused by lack of knowledge)

I used the diode setting to check the orientation, a few millivolts one way, 0 the other.

Indeed I am picking up the open-circuit voltage on the reverse side, I thought this was a problem with the diode but it seems this is normal from how you describe (how diodes work)
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
So this means that my logic and use of multimeter is incorrect? (course by lack of knowledge)

I used the diode setting to check the orientation, a few millivolts one way, 0 the other.

Indeed I am picking up the open-circuit voltage on the reverse side, I thought this was a problem with the diode but it seems this is normal from how you describe (how diodes work)
It's simply your 'reading' of the meter that is at fault - the meter won't be reading '0' - it will be displaying an over-range indication.

On two meters here, one displays '0L' the other displays '1.', neither displays zero, which would make no sense.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
hoped that the Ecoflow would charge via solar during the day and then at night the 12v input (car cigarette charger) would take over. But I have tested at night (no sun) and the PV circuit is still 45V. If this is the case (and from your statement) the 12v input will never contribute. I will test this, but I don't want to connect it up until I am sure that the 12v circuit is protected

If you leave the 12V input disconnected but with everything else connected - and no sun - what voltage do you get at the Ecoflow input?

Without actual loads connected, a digital multimeter may be reading from minuscule leakage currents that would have no effect with all parts connected.

If you get little or no voltage at the Ecoflow input, then try connecting something as a load at the 12V connector - a resistor, 10K or so, or a a low power filament lamp, and see what voltage you get across it with the solar panels producing a good output?
 

Tony Stewart

Well-Known Member
Most Helpful Member
I hope you do not destroy your equipment. We don't have enough info to judge that.
You should specify the example model of your equipment and show the link to the user manual that defines each port.

Normally I would expect your battery charger to be protected so you could just put it across the battery and it won't draw any power if the PV+MPPT + Battery Charger (EcoFlow) should also be protected.

Adding a diode will reduce the 12V charger voltage, which might be acceptable if you do not expect a full charge. So this is sub-optimal. They use dual Power FET's for this purpose with a steering circuit for selecting the source.

AFAIK https://www.ecoflow.com/us/support/download/index The manual is somewhere near there and they ought to have this cable you need.

There are Pb, Lithium and NiMH different types with MPPT controllers and chargers which independently optimize the voltage on the PV and the battery.

Diode "OR" logic means the higher voltage becomes the source.

You cannot "simply diode OR" 45V and 12V together on the same wire and expect MPPT PV charging.

More details are needed.
 
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TheOtherShiny

New Member
I'm not plugging anything in, unless I'm sure what I have is correct! :) And that is my responsibility to decide.

I did not expect this thread to be so thorough, but I guess the devil is in the detail! Here is a link to the manual. Car charger supports 12VDC and 24VDC.

Delta 1300

You cannot "simply diode OR" 45V and 12V together on the same wire and expect MPPT PV charging.

Am I trying to achieve the possible then? An off-the-shelf cable is not available, perhaps for this very reason.

I was trying to ensure that nothing was damaged before testing to see if it would work. You already seem to know the answer....


More Info:
Battery Info
Cell Chemistry NCM

Over Voltage Protection, Overload Protection, Over
Temperature Protection, Short Circuit Protection,
Low Temperature Protection, Low Voltage Protection,
Overcurrent Protection
 

Tony Stewart

Well-Known Member
Most Helpful Member
I see the DC input charge port is 10A max at high voltage (up to 65V) and 8A max at low voltage (down to 10V) So one must decide how much switch loss is acceptable to protect each source.

I assume the car charger is Fuse protected for >=10A and the DELTA will not demand more than 8A at car battery voltages.

I do not see any reverse voltage protection for the PV panel at night when the PV output is lower than the car charger. I assume that is the diode you are using which should be rated for 15 A to 25A for lower temperature rise than a 10A diode operating at 125'C

Both sources will need 15A to 25A diodes and common cathode dual diodes do exist.
These are the specs from your link.

Input Ports
AC Charge AC Input Voltage 100-120V~ 50Hz/60Hz X-Stream Fast Charge 1200W Max
Solar Charger 10-65V 10A, 400W Max
Car Charger Supports 12V/24V Battery, 8A max or < 120W from 12.5V Car

I don't know if your car charge cable is coming from a car battery charger from AC or from a car. I hope the DELTA will pulse and measure the DC Input port for MPPT optimal impedance matching to transfer maximal power. (or some other algorithm) You should call the DELTA tech support to confirm all these assumptions.



I would expect if your Car charge cable is actually AC to DC charger input, that using this is less optimal than the X-Stream Port which has a capacity of 1200W

Summary

I would not use the car DC port unless this is a van that drives around with a PV power panel on top.

I also don't know how your DELTA software works but it should choose all the current available from the DC port (green energy ?) before using AC port if the OUTPUT side demand needs power. So the diode is not necessary.

I would expect there is a software setting to limit capacity to 80% so that you can get 800 full discharge cycles of life near / at full 100% charge due to the excess voltage used. So a float charge level of 80% is perhaps optimal

Life is reduced by spending time > 80% capacity during CV mode charging and also < 20% capacity (unless deep cycle type) and over temperature.
 
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rjenkinsgb

Well-Known Member
Most Helpful Member
You cannot "simply diode OR" 45V and 12V together on the same wire and expect MPPT PV charging.
You can feed the "Ecoflow Delta" unit with that setup, though, to continue to put some charge in to it.

The same two pin XT60 DC input can accept anything from 12V to over 60V.


ps. TheOtherShiny - you can get extra XT60 connectors very cheaply on Amazon or ebay etc.

I use those (and XT30 & XT90 types) for all sorts of low power DC gear.
eg.


Please do the test I suggested in post #12?
 

TheOtherShiny

New Member
I assume the car charger is Fuse protected for >=10A and the DELTA will not demand more than 8A at car battery voltages.
Correct. Fuse is 10A
I do not see any reverse voltage protection for the PV panel at night when the PV output is lower than the car charger. I assume that is the diode you are using which should be rated for 15 A to 25A for lower temperature rise than a 10A diode operating at 125'C
I thought the diode provided reverse voltage protection.
I don't know if your car charge cable is coming from a car battery charger from AC or from a car. I hope the DELTA will pulse and measure the DC Input port for MPPT optimal impedance matching to transfer maximal power. (or some other algorithm) You should call the DELTA tech support to confirm all these assumptions.
From a van.
Summary

I would not use the car DC port unless this is a van that drives around with a PV power panel on top.
It is a van with PV on roof.
I also don't know how your DELTA software works but it should choose all the current available from the DC port (green energy ?) before using AC port if the OUTPUT side demand needs power. So the diode is not necessary.
Not in the manual but on the website FAQ. AC or DC it states:
"DELTA will prioritise AC charging, and default to DC charging when AC charging is not used."
I would expect there is a software setting to limit capacity to 80% so that you can get 800 full discharge cycles of life near / at full 100% charge due to the excess voltage used. So a float charge level of 80% is perhaps optimal

Life is reduced by spending time > 80% capacity during CV mode charging and also < 20% capacity (unless deep cycle type) and over temperature.
There is a new model Delta 2 where they have changed the battery type, boasting 6000 cycles.
 

Tony Stewart

Well-Known Member
Most Helpful Member
Warning Will Rogers!

You can use 10A on a 10A diode ONLY if you use a heatsink clamp to the body otherwise it will melt the wire insulation or at least burn it. I estimate 125 to 175'C junction temperature at 9 Watts on the R-6 axial case with a cooler case temperature of 2.5'C/W *9= 22'C below the above. One lead will be closer to the junction temperature than the case.

Normally these must be in forced air, clamped to a sink or thermally protected. This may cause some PVC outgassing. (chlorine) not good when charging at max current.

1666119863840.png


Some 15A diodes are 0.5V @ 10A (Schottky) , Silicon Diodes are usually near 1V +/-0.1 nominal (not worst case) The above one is not yours but same R-6 case type and will dissipate about 9W = 10A * 0.9V .


This tells me the diode may operate but at reduced lifetime and would burn your finger easily.
1666120521374.png


This is why I said you must consider a 25A diode or the proper dual FET steering switch. or a dual TO-220 15A to 25A Diode (with a heatsink to metal chassis and electrical grease and elect. isol. pad)

This reminds me when I used a similar diode to charge my frozen battery with a toaster in series. and I let the diode sizzle in the snow on the Neutral side near ground voltage. with 14V on the battery and hot on the toaster side with jumper wires. It took me 15 minutes to start my MGB convertible in the late 70's to get to work. at -30'C in Feb in Winterpeg.
 
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