MPPT solar controller and LiFePO4 battery for backpacking

[Dave C]

DO NOT USE the GV5 Load Port with your battery. Not going to work with your battery. Use the Load Port on the battery.

This won't work, because, again, the battery's two connectors do not perform separate functions. They're both soldered to the same points. I've tried to make this clear several times. Email Bioenno if you have any questions about this. With the battery connected to the controller via one of the battery's two connectors, the voltage at the other battery connector is equal to the voltage at the load terminals.

[Sunking]

I don't care about a high voltage alarm if my radio isn't connected to the controller's load terminals, but I sure do care if it is connected.

It cannot happen if the radio is connected. The load will keep the controller loaded and regulated.

Maybe I haven't made this point clear. I could just connect the panel after first disconnecting the radio, and connect the radio after first disconnecting the panel. But I'm trying to find out if there's a way to make it safe to leave the radio and the panel connected to the controller at all times in order to maximize both radio availability and battery charging time.

If a TVS diode, which two different engineers have recommended, isn't the right solution, would you please recommend a different solution to keep my radio supplied at <= 15V when the load terminals of the controller are at panel voltage?

I have done that many times. You are not getting it. Your battery is not compatible with the Controller. I gave you the three options. I am Ham Radio Operator and have done radio and telecom professionally for 35 years.

1. Get a battery without a PCM board in it.
2. Raise the GV5 voltage to 14.6 volts so the battery current does not go to Zero and keep the radio connected.

FWIW the zener diode is not a TVSS, it presents a load on the controller. If it is a Silicon Avelanche Diode it presents a SHORT CIRCUIT which takes the voltage to 0 volts when it triggers on.

[Sunking]

This won't work, because, again, the battery's two connectors do not perform separate functions. They're both soldered to the same points.

Same Point electrically but two relays. A HVC relay and a LVD relay in the PCM circuit. They operate independently of each other. That is why the battery has a Charge Port and Discharge Port. Otherwise there would be no ports, just Battery Term Post like any other battery.



Look at the specs

Includes built-in PCM (protection circuit module) which provides balancing of internal cells, and protection from overcurrent, undervoltage (overdischarge), and overvoltage.

I understand what you want to do. You want to FLOAT the battery and leave it connected to the Controller so as to use solar power when available. That is exactly what the GV5 or really any solar controller is made to do. Problem is YOUR BATTERY IS NOT MADE TO DO THAT. You need a LFP made as a Drop-In replacement like I already showed you WITHOUT a PCM. BMS is fine, but not PCM. A Drop In LFP Replacement does not disconnect from the charger. A Solar Controller cannot have the battery disconnected.

[Dave C]

You need a LFP made as a Drop-In replacement like I already showed you WITHOUT a PCM. BMS is fine, but not PCM. A Drop In LFP Replacement does not disconnect from the charger. A Solar Controller cannot have the battery disconnected.

The battery that you showed me was, unfortunately, too big and heavy. This one is the right size and weight, but it has PCB.

Unfortunately, with all due respect, your abrasive delivery and your unwillingness to adjust your course when new or different information becomes available make me question your advice.

Edit: However, you have provided valuable information. Your explanation of the term "float" is much appreciated.

[Sunking]

Here is what is inside your battery. Read the SPECS. If the battery I listed is too heavy/bigg, is because it is a higher capacity battery than yours. Get the right size.

[karrak]

This is why I need voltage suppression, and the 15V value comes from my radio's max voltage rating. I think 15.6V is too high.

Your radio will be just fine. If it has been built to plug into a 12 volt power source like a battery with an attached charger the radio designers should have take into account issues like voltage transients. The voltage figure in the radio operator's manual will be the maximum operating voltage that the radio should operate at. This is less than the absolute maximum voltage at which damage will occur. Also and here I actually agree with Sunking, having the radio turned on and providing a load for the GV5 when the Bioenno's BMS disconnects the battery will mean the GV5 should be able to maintain the voltage regulation.

Simon

[karrak]

Repeatably and you do not even know what you are talking about. That is what happens, and the only way it can happen is when you modulate at 0% which you claim any Controller does. So which is it? If they go to 0% modulation, voltage goes to ZERO. Which is it?

Wrong, yet again. If there is no load on the output of the power circuit in the MPPT controller the capacitors in the output stage of that circuit will hold the voltage at whatever voltage they have been charged up to. With a load on the output the voltage will slowly go down.

When a MPPT controller switches from an absorb voltage of say 14.2 volts to a float voltage of 13.8 volts it should disconnect the solar panels from the battery i.e.modulate at 0%. It then waits for the voltage to drop down to 13.8 volts and then start switching through power from the solar panel to keep the voltage at 13.8V.

[karrak]

If you had the Controller go up to 14.6 Volts, your BMS Vampire Boards would Turn On and Bleed Current, and keep BLEEDING Current until the Sun Quits Shinning. You rGV5 only goes to 14.2 and when the batteries SATURATE at 14.2 volts, all current STOPS. Listen to ole SK, he knows WTF he is talking about.

You don't know if that is how it works. Bioenno has stated that the balancing works on both charge and discharge so maybe they are using the difference in voltage between the cells as a trigger to do the balancing. If they are using a fixed voltage to trigger cell balancing, you don't know what that is. It might be higher than 3.65V

[karrak]

Here is what is inside your battery.

You don't know that. Have you taken a Bioenno battery apart?, the circuit you have shown is from a different manufacturer.

[karrak]

Unfortunately, with all due respect, your abrasive delivery and your unwillingness to adjust your course when new or different information becomes available make me question your advice.

Edit: However, you have provided valuable information. Your explanation of the term "float" is much appreciated.

I agree that some of the information that Sunking provides is useful, but there is so much that is just plain wrong. This might be OK if Sunking would accept when he is wrong, learn from his mistakes and be prepared to listen to what others are saying, but in the year that I have been writing on this forum I see no evidence of this or that he is prepared to change.

The problem is that if Sunking is challenged in any way the treads where he is being challenged just degenerate to the point where it is hard to extract any useful information from all the dross, so the useful information is lost. Maybe this is his strategy, I don't know.

Simon

[Dave C]

Your radio will be just fine. If it has been built to plug into a 12 volt power source like a battery with an attached charger the radio designers should have take into account issues like voltage transients. The voltage figure in the radio operator's manual will be the maximum operating voltage that the radio should operate at. This is less than the absolute maximum voltage at which damage will occur. Also and here I actually agree with Sunking, having the radio turned on and providing a load for the GV5 when the Bioenno's BMS disconnects the battery will mean the GV5 should be able to maintain the voltage regulation.

Simon

This is good news, and the fact that you two agree on this is a help. I'll confirm with Elecraft. But before I trust my radio to this setup, I'll test with a resistor.

[Sunking]

Wrong, yet again. If there is no load on the output of the power circuit in the MPPT controller the capacitors in the output stage of that circuit will hold the voltage at whatever voltage they have been charged up to. With a load on the output the voltage will slowly go down..

Complete rubbish. If you had really every built a MPPT controller, then you know they all use a Constant-On-Buck Converter. Just about every MPPT Controller including the GV5 uses a TI LM5019MR 100V, 100mA Constant On-Time Synchronous Buck Regulator. Go look at the data and application sheets. None of the Buck Regulators made by TI or Fairchild are capable of 0% On Time. There is no need to. Read the Control Overveiw:

The LM5019 buck regulator employs a control principle based on a comparator and a one-shot on-timer, with the output voltage feedback (FB) compared to an internal reference (1.225V). If the FB voltage is below the reference the internal buck switch is turned on for the one-shot timer period, which is a function of the input voltage and the programming resistor (RON). Following the on-time the switch remains off until the FB voltage falls below the reference, but never before the minimum off-time forced by the minimum off-time one-shot timer. When the FB pin voltage falls below the reference and the minimum off-time one-shot period expires, the buck switch is turned on for another on-time one-shot period. This will continue until regulation is achieved and the FB voltage is approximately equal to 1.225V (typ)

It is a plain as the nose on your face. Read it, MINIMUM OFF-TIME. That means never goes to ZERO

[Sunking]

Dave what you need to understand about Karrak is he is here only for one purpose and one purpose only. To harass me. He has admitted so in writing. Go look for yourself. Page 3 midway down.

the only reason I am posting on the other forum is to counter the gospel according to Sunking

Now ask why the mods allow him to stay? He even starts threads to harass me.

[solar pete]

I had a look, seems to me you two have different opinions, thats ok with me. Dont see why you cant argue nicely, cheers.

[Dave C]

Gentlemen, thank you. You've been extremely generous with your time and expertise. It would have taken me a very, very long time to get to the required information without your assistance.

You've helped me to make a decision about the controller and battery. Now I have one more set of project-related questions that's not specifically within the scope of solar power.

I would like to add a digital panel meter to monitor either voltage and current or just voltage. Is it advisable to monitor current? If so, should I monitor the charge or discharge side? I think charge current would be more variable so of more interest.

I'm looking at this panel multimeter, which requires a separate 4.5 ~ 30V power supply. The meter's negative power lead would connect either to nothing or to a "buck circuit (module) negative". Would the controller be the buck circuit they're referring to? Instead of connecting to a buck circuit, should the power supply's negative terminal be wired to the meter's common ground?

Measuring just voltage would be easier with a meter that requires no additional power supply.

[Dave C]

Dave what you need to understand about Karrak is he is here only for one purpose and one purpose only. To harass me. He has admitted so in writing. Go look for yourself. Page 3 midway down.

Now ask why the mods allow him to stay? He even starts threads to harass me.

I see that this is difficult for you. None of us are above this kind of conflict. Personally, faith in God and prayer help me to deal with life's difficulties better than I would otherwise. I wish you peace and security to deal with the challenges that face you.