MPPT solar controller and LiFePO4 battery for backpacking

[Dave C]

The battery just needs to stay connected PERIOD. That is what you do not understand. A solar panel and charge controllers are current sources. It requires the battery to turn it into a VOLTAGE SOURCE so the Controller can regulate the voltage. You have been given all your options. Pick one.

1. If it were me I would just connect the radio to the GGV5 Load Port, or Battery Discharge Port, turn it on, leave it on, walk away and call it good. It will work just fine.
2. Get a battery that is compatible and does not disconnect itself from the controller.

Take your pick. It is not that difficult. The resistor idea may or may not work but comes with a catch. It uses precious power you cannot afford. A 12 volt 4.5 AH battery only has 54 watt hours with only 44 usable. If that resistor burns 1 watt, you are using 50% of the capacity of the battery in a day making useless heat. That is on top of what the radio uses. A recipe for a dead battery.

"You have been given all your options. Pick one." What is this, "Kung Fu"?

The way I understand it from Genasun, when charging goes to 0A, the GV-5 goes to panel voltage for a couple of seconds before it settles into CV. If the GV-5 has to go to 0A to keep a drop-in-replacement battery at CV voltage, then even though the battery doesn't disconnect like the Bioenno battery does, it wouldn't eliminate the problem. I'll get a drop-in battery and experiment at some point.

Here's what Elecraft says about over voltage:

The absolute maximum input voltage is 15.0VDC. Any higher than that, or any voltage transients, will likely damage the PMOS switching power transistor that turns on the rig, and the PA transistors. Such damage would not be covered by the warranty.

So you need to do whatever is necessary to prevent more than 15.0VDC from ever being presented to the rig, either when it is OFF or ON. We have seen KX3s damaged if this happens.

It could be done by adding an external voltage regulator between the rig and the battery/solar panel charger, or some type of transient voltage suppressor, or by using a different solar controller that never allows more than 15.0VDC across the battery.

I've decided that I don't want to try floating any battery with this controller. Even with a completely compatible battery, an accident as simple as kicking a battery lead loose would fry my radio. In fact, although it's probably overkill, I might not float any battery with any controller with this radio in the loop.

When I get the controller, I'll experiment with a resistor at the load terminals. I wouldn't connect one permanently, though, because, as you said, it would use up the battery a lot faster.

[Sunking]

"You have been given all your options. Pick one." What is this, "Kung Fu"?

The way I understand it from Genasun, when charging goes to 0A, the GV-5 goes to panel voltage for a couple of seconds before it settles into CV. If the GV-5 has to go to 0A to keep a drop-in-replacement battery at CV voltage, then even though the battery doesn't disconnect like the Bioenno battery does, it wouldn't eliminate the problem.

Then you do not understand what they are telling you, and you might not have framed your question correctly.

If would be Impossible for the GV5 to go to Voc with a battery connected. I have told you this many times. To take that battery from 14.2 volts to 18 volts would require about 50 amps of charge current. It can only go to 18 volts if the resistance is open circuit. I pointed you to a tutorial that explains that. If you had read it you would understand.

But here is the run down. Those battery cells based on their size have an Internal Resistance of roughly .02 Ohm or 20 milli-Ohms each. With 4 in series will add up to .080 Ohms. To take that battery from 14.2 volts to 18 volts would require a charge current of [18 volts - 14.2 volts] / .08 Ohms = 47.5 Amps. To push that much current would require a minimum 900 watts and a controller capable of 50 amps.

If you look at IR curves on Solar Panels will also tell you it is impossible. A solar panel is a Current Source. Maximum current is generated at 0 volts called Isc (curent short circuit) At Vmp current is roughly 80% of Isc. From Vmp up to Voc current goes down to ZERO amps sharply. So even if you had a 900 watt panel with a Vmp at 16 volts, current would drop to zero amps at Voc. You lack of understanding is forcing you to make poor decisions.



Your 28 watt panel on its best day can only generate 2 amps of charge current. That means the highest voltage possible from the GV5 into your battery (assuming it is connected) is = 14.2 volts x [2 amps x .08 Ohms] = 14.216 volts.

[Dave C]

Then you do not understand what they are telling you, and you might not have framed your question correctly.

If would be Impossible for the GV5 to go to Voc with a battery connected. I have told you this many times. To take that battery from 14.2 volts to 18 volts would require about 50 amps of charge current. It can only go to 18 volts if the resistance is open circuit. I pointed you to a tutorial that explains that. If you had read it you would understand.

But here is the run down. Those battery cells based on their size have an Internal Resistance of roughly .02 Ohm or 20 milli-Ohms each. With 4 in series will add up to .080 Ohms. To take that battery from 14.2 volts to 18 volts would require a charge current of [18 volts - 14.2 volts] / .08 Ohms = 47.5 Amps. To push that much current would require a minimum 900 watts and a controller capable of 50 amps.

If you look at IR curves on Solar Panels will also tell you it is impossible. A solar panel is a Current Source. Maximum current is generated at 0 volts called Isc (curent short circuit) At Vmp current is roughly 80% of Isc. From Vmp up to Voc current goes down to ZERO amps sharply. So even if you had a 900 watt panel with a Vmp at 16 volts, current would drop to zero amps at Voc. You lack of understanding is forcing you to make poor decisions.

[URL="http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja &uact=8&ved=0ahUKEwifv_WD67LMAhVJJiYKHZyCAhwQjR wIB w&url=http%3A%2F%2Fwww.pddnet.com%2Farticle%2F20 10 %2F04%2Fmonolithic-battery-charger-simplifies-solar-powered-designs&bvm=bv.120853415,d.eWE&psig=AFQjCNEGdZb-2cMTZzsHd5UtPyV_pmSjAA&ust=1461984553626143"]

Your 28 watt panel on its best day can only generate 2 amps of charge current. That means the highest voltage possible from the GV5 into your battery (assuming it is connected) is = 14.2 volts x [2 amps x .08 Ohms] = 14.216 volts.

Thanks for all of this information. I will need to go through it a few times to get my head around it.

Here's what I think has misled me to believe that all batteries, including drop-in SLA replacments, would cause Voc in this contoller: I know from this thread that in order to keep a battery at CV, the controller has to eventually stop sending current to it, i.e., it has to lower current to 0A. In my limited understanding, I equated "lowers current to 0A" with "goes to open circuit". Now I understand that a controller could only go to Voc in the absence of a battery; it doesn't do so because of its own decision to send 0A to the battery.

I'm more curious now to test a drop-in battery. But I'll probably stick to my chosen solution, because it virtually eliminates the possibility of over voltage at the radio due to equipment or human error.

You've succeeded in helping me to understand the conditions under which a controller CAN go to Voc. But I still don't understand WHY any controller would allow Voc at the battery and load. I would expect to find Voc at the panel terminals, but not at the battery or load terminals.

[karrak]

I will be interested to see what happens when I test with a resistor. But I don't think a 1W resistor, connected at all times, is a good solution, as it will drain the battery.

I agree, this would only work if you only have the resistor connected when the GV5 is charging. If it was your intention to have the GV5 or for that matter any MPPT controller connected to the battery all the time you will have to check whether or not the controller would draw power from the battery when there was no power coming in from the solar panel.

Is there any LFP battery that would allow a controller to remain at some small current above zero at CV? From what I've learned here, I would say no. If my thinking is correct, then I question Sunking's reasoning that it would be possible to find a battery that would keep this controller from going to panel voltage. Of course, I'm willing to learn if I'm wrong.

This is the problem. Because of the virtually zero leakage current of LFP batteries the current going into a LFP battery will go down to virtually zero if you charge it to a fixed voltage. Now, if as Sunking maintains, no MPPT controller is capable of providing a regulated output unless there is some load on it when the current gets to whatever the minimum that the controller will loose regulation at the voltage will start creeping up as the battery gets to a higher and higher SOC. If this voltage gets too high you will start damaging the battery.

Now, I don't think this is correct. I think that if not all then the majority of MPPT controllers will be able to regulate the voltage without any load so you will be able to charge LFP batteries with an MPPT controller but the issue of whether an MPPT controller is capable of working without a load is something to bear in mind.

The problem with your Bioenno battery is that it will suddenly disconnect the battery from the MPPT controller while there is still current flowing. IMO a well designed MPPT controller would be able to cope with this and only produce a small transient voltage rise that would not be enough to damage equipment connected to it.

Simon

[karrak]

Here's what Elecraft says about over voltage: ...
"The absolute maximum input voltage is 15.0VDC. Any higher than that, or any voltage transients, will likely damage the PMOS switching power transistor that turns on the rig, and the PA transistors. Such damage would not be covered by the warranty."

I've decided that I don't want to try floating any battery with this controller. Even with a completely compatible battery, an accident as simple as kicking a battery lead loose would fry my radio. In fact, although it's probably overkill, I might not float any battery with any controller with this radio in the loop.

I would be concerned if the voltage ratings of the components in the Elecraft radio are only 15 volts and if this were the case would be concerned operating it at 14.2V. If a manufacturer states an operating voltage of 15 volts they should have some sort of safety margin, just as someone building a house wouldn't want it teetering on the the edge of collapsing. I would think 5 volts is not an unreasonable bare minimum safety margin for this application. Running components, especially electrolytic capacitors right at the top of their operating voltage range will usually decrease their life span and is to be avoided. Would be an interesting exercise to take one of the radios apart and check all the components in the power input circuit or to talk to one of the design engineers who designed it.

Simon

[karrak]

Here's what I think has misled me to believe that all batteries, including drop-in SLA replacments, would cause Voc in this contoller: I know from this thread that in order to keep a battery at CV, the controller has to eventually stop sending current to it, i.e., it has to lower current to 0A. In my limited understanding, I equated "lowers current to 0A" with "goes to open circuit".

That is the correct understanding. If you look at the situation from the battery's point of view the controller is a bit like a switch between the solar panel and the battery. If the switch is on, or partially on current will flow into the battery. It is up to the controller to regulate this flow to keep the correct battery voltage. When the battery is full there should be no current flow to the battery. As far as the battery sees, the switch in the controller will be turned off, i.e. an open circuit.

Now I understand that a controller could only go to Voc in the absence of a battery; it doesn't do so because of its own decision to send 0A to the battery.

Not quite true. If the battery is drawing zero current the battery voltage will go up to Voc unless the controller disconnects the panel from the battery

But I still don't understand WHY any controller would allow Voc at the battery and load. I would expect to find Voc at the panel terminals, but not at the battery or load terminals.

The controller should never allow Voc at the battery terminals.

Simon

[Dave C]

I would be concerned if the voltage ratings of the components in the Elecraft radio are only 15 volts and if this were the case would be concerned operating it at 14.2V. If a manufacturer states an operating voltage of 15 volts they should have some sort of safety margin, just as someone building a house wouldn't want it teetering on the the edge of collapsing. I would think 5 volts is not an unreasonable bare minimum safety margin for this application. Running components, especially electrolytic capacitors right at the top of their operating voltage range will usually decrease their life span and is to be avoided. Would be an interesting exercise to take one of the radios apart and check all the components in the power input circuit or to talk to one of the design engineers who designed it.

Simon

The minimum voltage rating is 8V.

[Dave C]

If you look at the situation from the battery's point of view the controller is a bit like a switch between the solar panel and the battery. If the switch is on, or partially on current will flow into the battery. It is up to the controller to regulate this flow to keep the correct battery voltage. When the battery is full there should be no current flow to the battery. As far as the battery sees, the switch in the controller will be turned off, i.e. an open circuit.

This makes sense.

"Now I understand that a controller could only go to Voc in the absence of a battery; it doesn't do so because of its own decision to send 0A to the battery."

Not quite true. If the battery is drawing zero current the battery voltage will go up to Voc unless the controller disconnects the panel from the battery

That disconnect would have to be at some low current threshold so the battery never gets to 0A, right?

So for Sunking's suggestion to be a good one, it must be that either: 1) a drop-in replacement battery simulates leakage during charging; or 2) charging current never actually goes to zero with LFP--very close to it, but high enough to let the controller know that a battery is still there. Unless you two agree on this (or someone else weighs in), the only way for me to know would be to test with a battery that has no low current disconnect. Do you agree that as a rule, drop-in batteries have no above-zero low current threshold? Would this be a worthwhile test?

[Sunking]

Dave what Karrak and you are not grasping is a Solar Panel and Solar Charge Controllers are Current Sources. I don't expect neither of you to fully grasp it as neither of you are educated technicians or engineers. Simon Mathews aka Karrak is a Consumer Electronics redistributor aka salesman. Not sure what you do. Point is it takes a battery in this application to turn a Current Source into a Voltage Source.

The characteristic of any Current Source cannot be debated. If you open Circuit a Current Source, the voltage goes to the source voltage. In this case that is your Solar Panel. A solar panel specs tell you exactly what voltages and currents it produces under what conditions. For this discussion Voc demonstrates the fact. Voc = Voltage Open Circuit. Current does not flow in an Open Circuit. The other spec is Isc = Current Short Circuit ot how much current the Current source can supply. Isc is at 0 voltage. You rpanel maximum current is at 0 volts of just less than 2 amps. At Vmp can only supply 1.6 amps.

Solar Charge Controllers are not designed to output Zero Volts and Zero Amps. There is no reason for them to do that. If you want 0 volts and 0 amps, you disconnect the panel. For a 12 volt controller, there is absolutely no reason to design the controller to go below 12 volts. Nor will it output 0 amps at any time because the controller gets its power from the output of the controller. It would be self defeating for a Controller to output 0 anything.

A battery is far from an Open Circuit. In fact it has a extremely low resistance. In your case each cell is approx .020 Ohms, and with 4 in series is a total of .08 Ohms. To change the voltage of the battery by 1 volt up or down requires 1 volt / .08 Ohms = 12.5 amps. Now stop and think about that. The only way you can have 12.5 amps flowing is on DISCHARGGE, and the voltage of the battery would go DOWN. For it to go up 1 volt requires 12.5 amps. Where in the Hell is that current going to come from? It cannot come from the panel or controller.

There is only one possible way for a Solar Panel to output Voc voltage. OPEN CIRCUIT with NO CURRENT. If anyone tells you differently, they have no clue what they are talking about.

[Dave C]

Dave what Karrak and you are not grasping is a Solar Panel and Solar Charge Controllers are Current Sources. I don't expect neither of you to fully grasp it as neither of you are educated technicians or engineers. Simon Mathews aka Karrak is a Consumer Electronics redistributor aka salesman. Not sure what you do. Point is it takes a battery in this application to turn a Current Source into a Voltage Source.

The characteristic of any Current Source cannot be debated. If you open Circuit a Current Source, the voltage goes to the source voltage. In this case that is your Solar Panel. A solar panel specs tell you exactly what voltages and currents it produces under what conditions. For this discussion Voc demonstrates the fact. Voc = Voltage Open Circuit. Current does not flow in an Open Circuit. The other spec is Isc = Current Short Circuit ot how much current the Current source can supply. Isc is at 0 voltage. You rpanel maximum current is at 0 volts of just less than 2 amps. At Vmp can only supply 1.6 amps.

Solar Charge Controllers are not designed to output Zero Volts and Zero Amps. There is no reason for them to do that. If you want 0 volts and 0 amps, you disconnect the panel. For a 12 volt controller, there is absolutely no reason to design the controller to go below 12 volts. Nor will it output 0 amps at any time because the controller gets its power from the output of the controller. It would be self defeating for a Controller to output 0 anything.

A battery is far from an Open Circuit. In fact it has a extremely low resistance. In your case each cell is approx .020 Ohms, and with 4 in series is a total of .08 Ohms. To change the voltage of the battery by 1 volt up or down requires 1 volt / .08 Ohms = 12.5 amps. Now stop and think about that. The only way you can have 12.5 amps flowing is on DISCHARGGE, and the voltage of the battery would go DOWN. For it to go up 1 volt requires 12.5 amps. Where in the Hell is that current going to come from? It cannot come from the panel or controller.

There is only one possible way for a Solar Panel to output Voc voltage. OPEN CIRCUIT with NO CURRENT. If anyone tells you differently, they have no clue what they are talking about.

Yes, I understand this. What is your version of how a controller behaves when the battery's voltage reaches the controller's CV voltage? How does the controller keep the voltage from going higher?

Can you or Simon recommend any books on how an MPPT controller for LFP batteries operates?

[karrak]

I would think 5 volts is not an unreasonable bare minimum safety margin for this application

The minimum voltage rating is 8V.

I think there is a misunderstanding here. By 5 volt margin I meant that all the components that are directly connected to the input power plug should be able to withstand at least 20 volts
without damage. I think the 8 volt figure is the minimum voltage that the radio will operate at.

Simon

[Sunking]

Yes, I understand this. What is your version of how a controller behaves when the battery's voltage reaches the controller's CV voltage? How does the controller keep the voltage from going higher?

Not my version, it is simple Ohm's Law and physics, current comes to a stop, and voltage holds at the set point. All batteries have what is called self discharge. The controller will hold the voltage at set point, and the only current flowing is the self discharge current of the battery.. Now if you have a load turned on, like your radio, it will be Self Discharge Current plus the Load Current. If the load current exceeds what th epanels can supply, the battery supplies the power.

Can you or Simon recommend any books on how an MPPT controller for LFP batteries operates?

No such book exist in that context. Now you can read up on Buck Converters and application notes from IC manufactures. The king of battery IC's is Texas Instruments, If you look back I gave you a link to the most popular TI IC used in MPPT controllers, and there are dozens of designs out there on the internet with the chips. However here it is again a 24/12 volt, 20 Amp MPPT controller using a TI MSP430F5132 controller IC. Take note of what the description is telling you in the TEST REPORT. What Simon does not understand the output never goes to 0% because the circuitry uses 10 ma from the output. Anyone who has electronic design experience knows you cannot power anything with ZERO VOLTS, AMPS & WATTS. Thus the output never goes to ZERO. That tells you Simon Mathews is a pretender.

What sets any solar charge controller apart from say any AC powered source is the Buck Converters power source. Solar is from a Current Source of unknown power at any given time. For an AC power source is a Stiff Voltage Source like from a battery or generator with unlimited power. A 30 amp AC charger can supply 30 amps forever and can regulate voltage from 0 amps to full rated amps. A battery can take as much current as the source can provide. It is that difference in a power source that makes them react differently.

There is no mystery to charging batteries. It does not matter what the battery type is, they all charge the exact same way. All it takes is an understanding of Ohms law and DC 101 circuit theory. There is a great book on batteries. I call it the Battery Bible. It covers every battery types and its characteristics. It is titled HANDBOOK of BATTERIES 4th edition is the latest. You can find free copies of the 3rd edition in PDF if you click the link I just gave you which is still valid today. It is written by David Linden and Thomas Linden. I know David as he chairs IEEE-450 and 455 committee which I was a contributing member before retiring. All you gotta do is read 1400 pages. Start with Chapter 34 as it is the shortest and easiest to understand chapter in the book (Lithium). Nothing to it as they are the easiest battery to charge. FWIW the most complicated and difficult battery to charge in NiMh followed by NiCd, and Pb. The book covers every battery chemistry there is.

I use to work in Telecom for 30 years for a major telco and have installed thousands of DC battery plants. After being laid off in 2003 I started my own engineering company doing the same work for more money, an dhave built over 200 Off-Grid Battery systems at remote cell sites, and some large grid tied systems for Walmart and DOD.

Back to Current Sources. Makes no difference is the Current Source is from a Voltage Source or Solar Panel, if you open the load, the voltage goes to the source voltage. A Solar Panel is a Current Source and the controller has a huge capacitor at its output. Your own eyes have seen what happens when the battery is disconnected. Your eyes are not lying to you.

[karrak]

That disconnect would have to be at some low current threshold so the battery never gets to 0A, right?

So for Sunking's suggestion to be a good one, it must be that either: 1) a drop-in replacement battery simulates leakage during charging; or 2) charging current never actually goes to zero with LFP--very close to it, but high enough to let the controller know that a battery is still there. Unless you two agree on this (or someone else weighs in), the only way for me to know would be to test with a battery that has no low current disconnect. Do you agree that as a rule, drop-in batteries have no above-zero low current threshold? Would this be a worthwhile test?

I will use an analogy of filling a bottle with water from a tap where the water supply is the solar panel, the tap and the person turning the tap on and off is the solar controller and the bottle is the battery.

When we start filling the bottle we turn the tap on full. The amount of water flowing into the bottle is limited by the pressure of the water and the resistance to the flow caused by the friction in the pipes and tap. The water pressure is equivalent to the solar panel voltage and the resistance to the water flow in the pipes is equivalent to the resistance of the circuit and internal resistance of the battery.

As the bottle gets nearly full the water starts to fill the neck of the bottle and as the neck is smaller than the body of the bottle the water level starts to rise more rapidly. At this point we slow down the flow of water by turning the tap partly off. When the solar controller reaches its CV point it starts limiting the current going to the battery so the battery voltage doesn't go too high.

When the bottle is full we turn the tap completely off to stop the flow of water. If we are too slow at turning the tap off the bottle will be overfilled.

If the tap is leaky and cannot be turned completely off and the bottle doesn't have any leaks the bottle will overflow. If the bottle has a leak in it (this equates to a Lead Acid battery) the bottle will not overflow if the leak is larger than the water leakage from the tap.

If we get a kink in the tube going into the bottle while the water is still flowing the water pressure in the pipe will very quickly rise to the pressure of the water supply. This would not happen if we could instantly turn the tap off. This is what happens with the solar controller when the battery BMS disconnects the battery. Now if we have a leak in the pipe going to the bottle or a pressure relief valve on the pipe that will let water out when the water pressure rises too high we won't have the problem with the water pressure getting too high. It is not too hard and doesn't add much extra cost to the solar controller to add the extra circuitry and/or software to stop the charging voltage from rising too high.

I hope this analogy has been useful. As far as I can see Sunking either doesn't understand the basic principles of MPPT controllers or he is just trying to make it all sound too complex for anyone else but himself to understand. Maybe it is a combination of both. As I have said before, the devil is in the detail and there is allot of complex detail that an engineer has to know if they are designing this sort of equipment. Hopefully the fundamental principles can be understood by people like you who are prepared to ask questions and learn something new.

Simon

[Dave C]

Sunking, if I understand you correctly, you're saying that at CV, current comes to a stop, and voltage simply remains at that voltage ("set point" is s new term which I think equates to CV voltage). My question is what keeps it there? I think you must mean that either: 1) the set point is equal to the "full" point of the battery, so that the system comes to some sort of equilibrium with no current flow; 2) the controller actively sets current to 0A; or 3) self discharge makes it so that current flow never stops. If the CV voltage of a controller is 14.2V, and the saturation point of a 4-cell LFP is 14.6V, then if there was such a thing as "equilibrium" in an electrical circuit, then the system couldn't be at equilibrium at 14.2V, right? If the controller actively stops the flow, then by Simon's illustration, the "pressure" on the controller would be panel Voc, right?

[Dave C]

I will use an analogy of filling a bottle with water from a tap where the water supply is the solar panel, the tap and the person turning the tap on and off is the solar controller and the bottle is the battery.

When we start filling the bottle we turn the tap on full. The amount of water flowing into the bottle is limited by the pressure of the water and the resistance to the flow caused by the friction in the pipes and tap. The water pressure is equivalent to the solar panel voltage and the resistance to the water flow in the pipes is equivalent to the resistance of the circuit and internal resistance of the battery.

As the bottle gets nearly full the water starts to fill the neck of the bottle and as the neck is smaller than the body of the bottle the water level starts to rise more rapidly. At this point we slow down the flow of water by turning the tap partly off. When the solar controller reaches its CV point it starts limiting the current going to the battery so the battery voltage doesn't go too high.

When the bottle is full we turn the tap completely off to stop the flow of water. If we are too slow at turning the tap off the bottle will be overfilled.

If the tap is leaky and cannot be turned completely off and the bottle doesn't have any leaks the bottle will overflow. If the bottle has a leak in it (this equates to a Lead Acid battery) the bottle will not overflow if the leak is larger than the water leakage from the tap.

If we get a kink in the tube going into the bottle while the water is still flowing the water pressure in the pipe will very quickly rise to the pressure of the water supply. This would not happen if we could instantly turn the tap off. This is what happens with the solar controller when the battery BMS disconnects the battery. Now if we have a leak in the pipe going to the bottle or a pressure relief valve on the pipe that will let water out when the water pressure rises too high we won't have the problem with the water pressure getting too high. It is not too hard and doesn't add much extra cost to the solar controller to add the extra circuitry and/or software to stop the charging voltage from rising too high.

I hope this analogy has been useful. As far as I can see Sunking either doesn't understand the basic principles of MPPT controllers or he is just trying to make it all sound too complex for anyone else but himself to understand. Maybe it is a combination of both. As I have said before, the devil is in the detail and there is allot of complex detail that an engineer has to know if they are designing this sort of equipment. Hopefully the fundamental principles can be understood by people like you who are prepared to ask questions and learn something new.

Simon

That is a great analogy.

Still not sure what would happen if the GV-5 were paired with a battery that has no low current threshold, and not sure how to easily identify that kind of battery. Will pursue this if and when I have time.

Many, many thanks to you and Sunking for taking the time to answer my questions.