I have a small basic 12V inverter charger setup with a Lifepo4 battery. I would like to add 200W of solar panels to my setup. Can it be done?

The inverter charger has no other connections other than AC and DC in and then AC out

Please help?

Edited January 16, 20232 yr by Eish
typo

You would need to have a small Solar charge controller, which you would then connect the panel to, and the battery you're using on the UPS to. The panel would then help to recharge that battery much quicker than the UPS does.

Thank you very much!

So my idea is to connect 4 x 70W Mono panels in parallel via MPPT (or PWM) controller to the battery. 

• Maximum Power Voltage: 18.31 V.
• Maximum Power Current: 3.83 A.
• Open Circuit Voltage: 22.65 V.
• Short Circuit Current: 4.04 A.

Please confirm this will work with my battery in parallel connection?

5 minutes ago, Eish said:

Please confirm this will work with my battery in parallel connection?

that would depend on the charge controller you'd have to get, but yes, in theory with a half way decent charge controller, 4 of those panels in parallel you should be able to get probably 20A or so of charge current into the battery when the panels are seeing good direct sunlight...

7 minutes ago, Kalahari Meerkat said:

that would depend on the charge controller you'd have to get, but yes, in theory with a half way decent charge controller, 4 of those panels in parallel you should be able to get probably 20A or so of charge current into the battery when the panels are seeing good direct sunlight...

FMI, would the charge controller be connected directly to the battery? Thus in parallel to the charger, and thus also sharing the load when there is no grid but there is PV available?

15 minutes ago, Bobster. said:

FMI, would the charge controller be connected directly to the battery? Thus in parallel to the charger, and thus also sharing the load when there is no grid but there is PV available?

Yes, there should be no problem with this...

Thanks guys, you have been awesome!

I ordered the panels and MPPT. This is the MPPT. I hope it's ok, I don't know the brand. My budget is very small so this was about all I could afford.

https://www.sustainable.co.za/products/epsolar-xtra-3210n-30a-12-24v-mppt-charge-controller-with-lcd-display?_pos=3&_psq=mppt-30a&_ss=e&_v=1.0

Features

Advanced MPPT technology & ultra-fast-tracking speed is up to 99.5 % guaranteed.
Advanced Display unit XDS2 for easier functionality
Maximum DC/DC transfer efficiency is as high as 98 %,full load transfer efficiency is up to 97.4 %.
Wide MPP operating voltage range.
Low temperature protection and self-activate function for lithium battery charging.
Limit charging power & current overrated range.
Real-time energy statistics function.
Multiple load work modes.
Comprehensive electronic protection.
Compatible with lead acid and lithium-ion batteries.
Over temperature protection and power degrading in higher temperature.
Optional LCD display units (XDB1/XDS1/XDS2) and accessories.
High quality and low failure rate components of ST or IR to ensure service life.
Isolated RS485 communication port with 5V/200mA protected output, with standard Modbus protocol.
Monitor and set the parameters via APP or PC software.
Dustproof and waterproof design with IP32 protection class.
CE certification(LVD IEC62109,EMC EN3/1-6-61000).
Electrical

Model: XTRA 3210N
System Nominal Voltage: 12/24VDC Auto
Rated Charge Current: 30A
Rated Discharge Current: 30A
Battery Voltage Range: 8～32V
Max. PV Open Circuit Voltage: 100V
Max. PV Input Power (W/V): 390/12 or 780/24
Equalization Voltage: Sealed(14.6V); Flooded(14.8V); User(17~9V).
Boost Voltage: Gel(14.2V); Sealed(14.6V); Flooded(14.8V); User(17~9V).
Float Voltage: Gel /Sealed /Flooded(13.8V); User(17~9V).
Grounding: Common negative grounding.
Self-consumption: ≤35mA(12V); ≤22mA(24V).
Discharge circuit voltage drop: ≤0.23V.
RS485 interface: 5VDC/200mA (RJ45).
LCD backlight time: 60S (Default).

 

On 2023/01/17 at 2:32 PM, Eish said:

Max. PV Open Circuit Voltage: 100V

with this and your solar panels having

On 2023/01/17 at 9:56 AM, Eish said:

Open Circuit Voltage: 22.65 V.

you can run the 4 solar panels in series and have

On 2023/01/17 at 9:56 AM, Eish said:

Maximum Power Voltage: 18.31 V.

times 4 = 73.24V and however many amps coming into the MPPT and thus have less cabling... and the charge controller would happily buck that down to 14-odd V to charge the battery, you must check on the recommended Voltages for the battery and program the charge controller with those...

Thanks Kalahri Meerkat for your reply.

if I connect in series, the amps going in will only be about 4amps . I always thought that the higher the current going into the battery, the faster it charges? That's why I want to do the parallel connection to ramp the amps up to about 16A.

On 2023/02/01 at 11:42 AM, Eish said:

if I connect in series, the amps going in will only be about 4amps

not with a buck converter type MPPT charge controller, it'll take the 70-odd Volt by 3.8Amp around 266W and bring that down to, let's assume around 14V and thus 266W/14V=18A or so, the conversion ain't 100%, so you need not parallel up the panels, since the charge side specifies

On 2023/01/17 at 2:32 PM, Eish said:

Max. PV Open Circuit Voltage: 100V
Max. PV Input Power (W/V): 390/12 or 780/24

the 18A is based on great sunshine and the panels facing the sun directly...

however, if you want to parallel up the panels, I don't think there's a problem with this, just a whole lot more copper from the panels to the MPPT to cater for the higher current...

Edited February 2, 20232 yr by Kalahari Meerkat
however

Thanks for your reply Meerkat! The learning curve is steep. Fortunately my current runs are short so parallel is not that expensive, I have the cable already. However, I wish I knew this earlier. 

@Kalahari Meerkat I have decided to follow your advise and do the series installation, reason being, is that now I do not have to move my inverter and battery. Unfortunately, that meant I had to buy extra cable, R550 later, considering the all benefits, this is a win-win situation.

Update to follow and again, thank you for pointing out that MPPT controllers can use low amperes and convert that to high. 

18 minutes ago, Eish said:

Update to follow and again, thank you for pointing out that MPPT controllers can use low amperes and convert that to high. 

No worries, the series install saves on copper, but plenty of "low voltage" MPPTs and inverters are still around, usually topping out at 145V or less, but even these, obviously buck convert down to 12 or 24 or 48Volt range, depending on the design and battery Voltage supported. The higher Voltage inverters with built in MPPTs usually run up to 400V, but some even more, like 600V, this then means 6kW can be done at 600V with 10A or so, that makes the copper cabling a lot thinner/less costly, as opposed to running at 80V and needing to support 75A or so...

Anyway, good luck cabling up your panels...

Thanks for the info Kalahari Meerkat. The series connection worked a charm! Much neater and less wires.

I bought MC4 connectors to connect the panels to the MPPT, only to find out yesterday when I had time to do the work, that the MC4 connectors I bought did not have the metal male and female lugs supplied. Being a Saturday, the place I purchased it from was closed, I scrambled to find new ones with the lugs. The learning curve has been steep. (But enjoyable, with thanks to this forum and it's members!) 

I will have time tomorrow to finish the cabling and test the setup, just in time for a 3 week away-from-home mission. However, I will leave the system disconnected when I am away so I can properly monitor it when I am back home though. 

But, I digress ... my MPPT controller has an earth screw connection. Do I just connect an earth wire from the battery cable there?  

Edited February 26, 20232 yr by Eish

31 minutes ago, Eish said:

Thanks for the info Kalahari Meerkat. The series connection worked a charm! Much neater and less wires.

I bought MC4 connectors to connect the panels to the MPPT, only to find out yesterday when I had time to do the work, that the MC4 connectors I bought did not have the metal male and female lugs supplied. Being a Saturday, the place I purchased it from was closed, I scrambled to find new ones with the lugs. The learning curve has been steep. (But enjoyable, with thanks to this forum and it's members!) 

I will have time tomorrow to finish the cabling and test the setup, just in time for a 3 week away-from-home mission. However, I will leave the system disconnected when I am away so I can properly monitor it when I am back home though. 

But, I digress ... my MPPT controller has an earth screw connection. Do I just connect an earth wire from the battery cable there?  

Based on the bit I have seen one does not earth the DC side. This is for panels as well as battery. 

Would like to hear if I have it wrong? 

Thanks for your reply Scorp007. Perhaps an AC earth point?

The manual only says "Grounding - Common Negative"

 

Edited February 26, 20232 yr by Eish

10 minutes ago, Eish said:

Thanks for your reply Scorp007. Perhaps an AC earth point?

The manual only says "Grounding - Common Negative"

 

The MPPT gets DC in and DC out. Should a fault be present then the DC system then gets earthed via this earth point. 

Thanks, I also works to read the manual 🤣

 

Step 3：Grounding XTRA N series is a common-negative controller, where all the negative terminals of PV array, battery and load can be grounded simultaneously or any one of them will be Figure 2-2 Schematic of wiring diagram 11 grounded. However, according to the practical application, all the negative terminals of PV array, battery and load can also be ungrounded, but the grounding terminal on its shell must be grounded, which may effectively shield the electromagnetic interference from the outside, and prevent some electric shock to human body due to the electrification of the shell. CAUTION: For common-negative system, such as motorhome, it is recommended to use a common-negative controller; but if in the common-negative system, some common-positive equipment are used, and the positive electrode is grounded, the controller may be damaged.

28 minutes ago, Scorp007 said:

Based on the bit I have seen one does not earth the DC side. This is for panels as well as battery. 

Would like to hear if I have it wrong? 

I tend to agree with @Scorp007 for 12V equipment you don’t need an earth connection as there’s no danger of electrocution at that kind of voltage. Leaving the whole system floating (not earthed) has the potential benefit that a short of any one part of the system to earth won’t cause a problem.

Edited February 26, 20232 yr by TaliaB

7 minutes ago, TaliaB said:

For 12V equipment you don’t need an earth connection as there’s no danger of electrocution at that kind of voltage. Leaving the whole system floating (not earthed) has the potential benefit that a short of any one part of the system to earth won’t cause a problem.

Why would it not be OK on a 24V system? 24V is below the level of danger but then the PV input could be 100V for a 12/24V controller as in this case. 

My reasoning a floating DC system does not need to go back to ground. Once one of the sides are grounded current can go through you to ground and that is the danger. As long as you don't touch both polarities at the same time. 

Edited February 26, 20232 yr by Scorp007

4 minutes ago, Scorp007 said:

Why would it not be OK on a 24V system? 24V is below the level of danger but then the PV input could be 100V for a 12/24V controller as in this case. 

My reasoning a floating DC system does not need to go back to ground. Once one of the sides are grounded current can go through you to ground and that is the danger. As long as you don't touch both polarities at the same time. 

It is what i just said?

On 1/16/2023 at 3:25 PM, Eish said:

I have a small basic 12V inverter charger setup with a Lifepo4 battery. I would like to add 200W of solar panels to my setup. Can it be done?

The inverter charger has no other connections other than AC and DC in and then AC out

Please help?

Yes, it is possible to add solar panels to your existing setup with a Lifepo4 battery and inverter charger. However, you will need to make sure that the solar panels you choose are compatible with your battery and charger, and that you have the necessary components to connect them.

Here are the steps you can take to add solar panels to your setup:

1. Check the specifications of your Lifepo4 battery to make sure it can handle the charging voltage and current of the solar panels you want to add. Also, check the specifications of your inverter charger to make sure it can handle the charging voltage and current from the solar panels.
2. Choose a solar panel or panels that are compatible with your battery and charger. Look for panels that have a voltage and current output that matches the charging specifications of your battery and charger.
3. Purchase a solar charge controller that is compatible with your battery and charger. The solar charge controller will regulate the charging voltage and current from the solar panels to prevent overcharging your battery and damaging your charger.
4. Install the solar panels and solar charge controller according to their instructions. You will need to connect the solar panels to the solar charge controller, and then connect the solar charge controller to your battery and charger.
5. Monitor the charging process to ensure everything is working properly. You should see the solar panels charging your battery and the inverter charger converting the battery power to AC power.

Remember to be cautious and follow the instructions carefully when making any changes or modifications to your electrical system.

1 hour ago, TaliaB said:

It is what i just said?

I tend to agree with @Scorp007 for 12V equipment you don’t need an earth connection as there’s no danger of electrocution at that kind of voltage. Leaving the whole system floating (not earthed) has the potential benefit that a short of any one part of the system to earth won’t cause a problem.

Edited 1 hour ago by TaliaB

I read only 12V thats why I added 24V.

On high voltage equipment (i.e. mains) earthing is a vital protective measure.  A person touching a live part will cause a fault current to flow to earth/ground which can then be detected by the earth leakage protection device.

However, it is ALWAYS a good idea to earth electric equipment, even low voltage 12V / 24V stuff.  With low voltage it is not for safety but to prevent, or at least **reduce**  noise radiation.   All chargers, inverters, etc. use switch-mode power supplies that typically switch at around 40 kHz or higher.  The switching devices produce a lot of switching transients (harmonics) that radiate EMF/RFI noise which can cause noise interference on audio equipment, noise on video, and could (potentially) even effect digital communication and processing.  (The noise can stretch into the many 100s kHz and MHz regions.)  A certain amount of switching noise will also be carried by input (battery) and output DC/AC wiring, and the house wiring then acts as a massive antenna for this noise.  This is normally referred to as "dirty" electricity.  Such radiation could also be detrimental to human health, although nobody wants to believe it....

Equipment is normally enclosed in steel enclosures or aluminium extrusions.  Due to the various holes for connectors, fans, cooling slots, etc. these enclosures are not perfect Faraday-cages, but still help substantially to prevent the equipment from radiating.  To do so, the metal enclosure should be tied to ground.  A true Faraday cage will do it's job even when electrically floating,  however, due to interconnects and stray capacitance it just works much better when a reasonable low impedance earth is provided.

Most power electronics, as indeed any modern electronics, use negative earth.  However, with power electronics, the lazy designer, or budget conscious, often place the shunt resistor (to measure the current) in the negative output line.  Even if you measure with a multimeter, it will seem that input and output negative terminals are linked, when in fact, there (might) be a 0.1 ohm (or lower) resistor between these terminals....