I want to be able to read the amps of my solar panels.

Thread Starter

twister007

Joined Feb 29, 2012
81
Wow! That meter has it all! And it looks like it would fit it the same hole as my meter!

Pure DC goes thru the wire. I made pulse width modulated controllers but they interfered with my AM radios. This is my best one yet! Voltage variation is not more than .o1 volt. If I calculated right, it will have 60 watts of heat to dissipate at 60 amps. I hope the case will do that without a fan!0214231615.jpg
 

Reloadron

Joined Jan 15, 2015
7,501
I just finished building a 60 amp solar panel voltage controller and I would like to be able to measure the amperage. With the built in volt meter. I can insert a 1 ohm resistor in series but that would waste power and create heat. I have a old 120 v transformer and I was wondering if I removed the winding and passed one output of the voltage controller thru the winding, would I pick up any kind of voltage that would make sense? The controler is pure DC. The volt meter reads down to .01.
Back to the beginning. My assumption was that you wanted to measure DC Current, the output current of a solar panel or solar array of panels. The way this is normally done measuring 60 amps of DC current is using a simple shunt resistor as pictured below.

50 Amp Shunt.png

This shunt happens to be a 50 amp / 50 mV shunt but just as easily could be a 100 amp / 100 mV shunt. Meaning the output is 1.0 mV per amp. The shunt would be configured exactly as drawn in Post #13

I have no idea where you are getting ideas as to lost power or heat generation. A 100 amp / 100 mV shunt will have a resistance of 100 mV / 100 amps = 0.001 ohm, a common off the shelf shunt resistance. Off the boat cheap 100 amp shunt. Then we have the brand name cost a little more shunt. Wither way you end up with a 1.0 milli-ohm shunt resistor.

Personally I would just go with the suggestion by crutschow in post
Depends upon what is going through the wire.

This may also be of interest.
It measures the current, as well as the solar panel voltage and power.
Simple off the boat solution including the shunt for an inexpensive price plug and play solution.

Voltage variation is not more than .o1 volt. If I calculated right, it will have 60 watts of heat to dissipate at 60 amps. I hope the case will do that without a fan!
I have no clue how you are coming up with your 60 watts of heat to dissipate. Things do not work that way. You are not losing or dissipating any power. I don't get that at all but I would run with that solution. It uses a shunt.

Ron
 

Thread Starter

twister007

Joined Feb 29, 2012
81
Back to the beginning. My assumption was that you wanted to measure DC Current, the output current of a solar panel or solar array of panels. The way this is normally done measuring 60 amps of DC current is using a simple shunt resistor as pictured below.

View attachment 287580

This shunt happens to be a 50 amp / 50 mV shunt but just as easily could be a 100 amp / 100 mV shunt. Meaning the output is 1.0 mV per amp. The shunt would be configured exactly as drawn in Post #13



I have no idea where you are getting ideas as to lost power or heat generation. A 100 amp / 100 mV shunt will have a resistance of 100 mV / 100 amps = 0.001 ohm, a common off the shelf shunt resistance. Off the boat cheap 100 amp shunt. Then we have the brand name cost a little more shunt. Wither way you end up with a 1.0 milli-ohm shunt resistor.

Personally I would just go with the suggestion by crutschow in post

Simple off the boat solution including the shunt for an inexpensive price plug and play solution.


I have no clue how you are coming up with your 60 watts of heat to dissipate. Things do not work that way. You are not losing or dissipating any power. I don't get that at all but I would run with that solution. It uses a shunt.

Ron
I was just talking about the controller it's self!
 

MisterBill2

Joined Jan 23, 2018
18,176
It does not make any sense at all that one who can build " I just finished building a 60 amp solar panel voltage controller" does not now how to use an ammeter shunt. In addition, that item in the photo in post#21 does not resemble a 60 amp charge controller, but much rather a meter box. A charge controller has active circuitry that limits battery current and voltage output .
 

MisterBill2

Joined Jan 23, 2018
18,176
For an education about power losses, use a good digital multimeter and some good, pointy, probes. For a DC circuit set the meter on the 200 millivolt range, and then probe between a connection lug and the terminal while the current is flowing. If the connection is good you will only see a very few millivolts, otherwise you may see quite a few. This is also a way to track down vehicle battery charging problems when nothing else is obvious. a bolted connection that looks solid might drop almost a volt at 20 amps. The 60 millivolt drop at 60 amps is not a problem, the drop at the various connections will be the problem. There is sometimes a real voltage drop between the wire and the terminal in a crimp connection, if it is not done right, or if the terminal was not clean enough inside prior to the crimp.
 
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Reloadron

Joined Jan 15, 2015
7,501
I was just talking about the controller it's self!
What exactly are you wanting to measure? A solar panel controller is:
A solar charge controller is used to keep the battery from overcharging by regulating the voltage and current coming from the solar panel to the battery. It is programmed at 15-A/200-W unit and uses MPPT (maximum power point tracking) to accelerate solar charging of the battery up to 30% per day.
This is my best one yet! Voltage variation is not more than .o1 volt. If I calculated right, it will have 60 watts of heat to dissipate at 60 amps. I hope the case will do that without a fan!
What exactly did you calculate to get those numbers? Something is wrong in all of this. Are you looking at charge / discharge of the battery? Whatever the goal is here I am not seeing it. I thought you were interested in the current from your solar panel or solar array? Now we are into the controller.

This was the first post. Please share exactly what the goal is. If this is all DC let's forget transformers.
I just finished building a 60 amp solar panel voltage controller and I would like to be able to measure the amperage. With the built in volt meter. I can insert a 1 ohm resistor in series but that would waste power and create heat. I have a old 120 v transformer and I was wondering if I removed the winding and passed one output of the voltage controller thru the winding, would I pick up any kind of voltage that would make sense? The controler is pure DC. The volt meter reads down to .01.
Thank You
Ron
 

nsaspook

Joined Aug 27, 2009
13,087
For an education about power losses, use a good digital multimeter and some good, pointy, probes. For a DC circuit set the meter on the 200 millivolt range, and then probe between a connection lug and the terminal while the current is flowing. If the connection is good you will only see a very few millivolts, otherwise you may see quite a few. This is also a way to track down vehicle battery charging problems when nothing else is obvious. a bolted connection that looks solid might drop almost a volt at 20 amps. The 60 millivolt drop at 60 amps is not a problem, the drop at the various connections will be the problem. There is sometimes a real voltage drop between the wire and the terminal in a crimp connection, if it is not done right, or if the terminal was not clean enough inside prior to the crimp.
That's what's I did with my solar energy monitor. High precision and good resolution to see millivolt drops across connections.
The goal is to get repeatable accuracy to 1mV and 10ma from the DAQ system for a precise energy usage and AGM battery SOC/energy storage condition calculation to at least 5% of actual run-time with dynamic load and charging profiles.

The DAQ front-end uses the ADC compute capability of the K42 to background capture and scan (using vector interrupts) all channels with 64 over-samples per channel and one extra bit for a total of 13-bit usable resolution.
1676476391131.png
C:
/*
 * adc channel configuration
 */
#define LAST_ADC_CHAN    0XD
#define ADC_BUFFER_SIZE    16 // MUST BE AT LEAST 1
#define ADC_SCAN_SPEED    200 // sample timer speed in ms
#define ADC_SCAN_CHAN    0b0011110001110111 // convert these analog ports bitmap

/*
 * Normal or high volt channels (bit set)
 */
#define ADC_V_CHAN_TYPE 0b0010000000100000

/*
 * current sensor configuration
 */
//#define BAT_100A // USE the 100A honeywell sensor for battery current, reduces range but has better data within that range
#define NUM_C_SENSORS    3
#define ADC_C_CHAN    0b0000100000000011 // 5 volt hall current sensor bitmap
#define ADC_C_CHAN_TYPE    0b0000000000000001 // 0 - 100A, 1=200A or battery 100A type if BAT_100A is defined
#define ADC_C_CHAN_MPPT    0b0000100000000000 // 0 - 100A mppt channel
//
typedef struct C_data { // real calculated variables
    float calc[ADC_BUFFER_SIZE];
    float c_load, c_bat, c_pv, c_mppt, v_cc, v_pv, v_bat, v_cbus, v_bbat, v_temp, v_inverter, v_sensor, v_cmode, bv_ror, bc_ror;
    float p_load, p_inverter, p_pv, p_bat, p_mppt, start_power;
    float t_comp, esr;
    float bank_ah, dynamic_ah, pv_ah, loadah, dynamic_ah_adj, dynamic_ah_daily, dynamic_ah_adj_daily;
    float bkwi, bkwo, pvkw, invkw, loadkw;
    uint16_t runtime, soc;
    bool update;
    hist_type hist[1];
    float load_i1, load_i2, bv_noload, bv_one_load, bv_full_load;
    bool day, dupdate;
    time_t day_start, day_end, day_update, updates;
} C_data;
https://forum.allaboutcircuits.com/...c-controlled-battery-array.32879/post-1448225
https://forum.allaboutcircuits.com/...c-controlled-battery-array.32879/post-1513872
 
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Thread Starter

twister007

Joined Feb 29, 2012
81
For an education about power losses, use a good digital multimeter and some good, pointy, probes. For a DC circuit set the meter on the 200 millivolt range, and then probe between a connection lug and the terminal while the current is flowing. If the connection is good you will only see a very few millivolts, otherwise you may see quite a few. This is also a way to track down vehicle battery charging problems when nothing else is obvious. a bolted connection that looks solid might drop almost a volt at 20 amps. The 60 millivolt drop at 60 amps is not a problem, the drop at the various connections will be the problem. There is sometimes a real voltage drop between the wire and the terminal in a crimp connection, if it is not done right, or if the terminal was not clean enough inside prior to the crimp.
Very interesting and good to know!
 

dcbingaman

Joined Jun 30, 2021
1,065
Victron SmartSolar system provides the entire communications protocol for their devices. Not what I am use to seeing, typically companies keep the protocol as proprietary but not Victron. If you want to make your own custom application, you can get all of the information (current, power, voltage etc.) from their devices using a simple UART protocol. Just something to keep in mind.
 

nsaspook

Joined Aug 27, 2009
13,087
Victron SmartSolar system provides the entire communications protocol for their devices. Not what I am use to seeing, typically companies keep the protocol as proprietary but not Victron. If you want to make your own custom application, you can get all of the information (current, power, voltage etc.) from their devices using a simple UART protocol. Just something to keep in mind.
They make great stuff. I 'borrowed' some of their H protocol ideas for my solar monitor data structures.

C:
    /*        hist[x].h[x]
     *        h0    Real Ah usage this cycle
     *        h1    Total charge cycles into at least boost
     *        h2    Current lowest discharge,
     *        h3    PV ah total
     *        h4    Batt W out 
     *        h5    Batt W in
     *        h6    Real Ah usage 
     *        h7    Batt Voltage full load
     *        h8    Batt Voltage one load
     *        h9    Lowest ESR
     *        h10    Highest ESR
     *        h11    Total charge cycles into float
     *        h12    Total kWH in
     */

    typedef struct hist_type {
        int32_t pv_eff, tot_eff; // pv generation eff factor, total system eff factor
        uint32_t ttg_t, updates;
        time_t pclock;
        float peukert, cef, peukert_adj, cef_calc, cef_save;
        int16_t h[HPARAM_SIZE]; // h[6]=cumulative battery Ah cc and inv (real),h[0]=cumulative battery Ah cc and inv (p_adj)
        uint16_t rate, udod, bsoc, bound_rate, bound_factor, samplei, sampleo, ah, drate, esr, rest_rate, rest_factor, esrp;
        uint8_t version;
    } hist_type;
[/quote]
 

drjohsmith

Joined Dec 13, 2021
852
What voltage do you have out of the panels ?
mine seem to run at around 400 to 700 volts, depending upon the best operating point,
thus low current , low voltage drop, low wastage.
I'd not put a USB connected meter on that ! you need isolation,
 

dcbingaman

Joined Jun 30, 2021
1,065
They make great stuff. I 'borrowed' some of their H protocol ideas for my solar monitor data structures.

C:
    /*        hist[x].h[x]
     *        h0    Real Ah usage this cycle
     *        h1    Total charge cycles into at least boost
     *        h2    Current lowest discharge,
     *        h3    PV ah total
     *        h4    Batt W out
     *        h5    Batt W in
     *        h6    Real Ah usage
     *        h7    Batt Voltage full load
     *        h8    Batt Voltage one load
     *        h9    Lowest ESR
     *        h10    Highest ESR
     *        h11    Total charge cycles into float
     *        h12    Total kWH in
     */

    typedef struct hist_type {
        int32_t pv_eff, tot_eff; // pv generation eff factor, total system eff factor
        uint32_t ttg_t, updates;
        time_t pclock;
        float peukert, cef, peukert_adj, cef_calc, cef_save;
        int16_t h[HPARAM_SIZE]; // h[6]=cumulative battery Ah cc and inv (real),h[0]=cumulative battery Ah cc and inv (p_adj)
        uint16_t rate, udod, bsoc, bound_rate, bound_factor, samplei, sampleo, ah, drate, esr, rest_rate, rest_factor, esrp;
        uint8_t version;
    } hist_type;
[/quote]
Nice. I just purchased a system from Victron that I am adding to a closed in trailer that I am converting to a camper. I plan to talk to the system and make a linear heating system that uses a fuzzy logic controller to run the heater when sufficient battery is available, sufficient sun, temperature etc. Nice to see you have used this companies equipment. I was pleasantly surprised to learn they offer their protocol for free.
 

nsaspook

Joined Aug 27, 2009
13,087
Nice. I just purchased a system from Victron that I am adding to a closed in trailer that I am converting to a camper. I plan to talk to the system and make a linear heating system that uses a fuzzy logic controller to run the heater when sufficient battery is available, sufficient sun, temperature etc. Nice to see you have used this companies equipment. I was pleasantly surprised to learn they offer their protocol for free.
I have diversion logic that will run the inverter battery down to a preset SOC level then transfer the AC load circuits back to grid power. That set-point decision is much easier if you don't use flooded lead acid batteries.
 

MisterBill2

Joined Jan 23, 2018
18,176
For heating that trailer, solar hot water will be more effective during daylight, at least. But that is off the main topic here. In engineering everything is a tradeoff: cost versus efficiency is often what it gets down to. If our electrical power grid were upgraded to 95% efficiency probably we cold not afford it.
So collecting high accuracy data will be an interesting way to see just how much you save versus paying for the local power company to deliver power. In sunny areas it makes sense especially if the utility does not provide reliable service. In my area the sun does not provide enough sun- watt hour days to be cost effective much of the year.
 

MrAl

Joined Jun 17, 2014
11,389
I just finished building a 60 amp solar panel voltage controller and I would like to be able to measure the amperage. With the built in volt meter. I can insert a 1 ohm resistor in series but that would waste power and create heat. I have a old 120 v transformer and I was wondering if I removed the winding and passed one output of the voltage controller thru the winding, would I pick up any kind of voltage that would make sense? The controler is pure DC. The volt meter reads down to .01.
Hi,

I think someone already mentioned you can use a current shunt and appropriate volt meter to measure the current. A current shunt typically has very low resistance so you dont loose much power at all, it will be very insignificant i assure you.

You can also use a ready made hall effect current sensor.

Clamp on ammeters use a transformer metal core to increase the concentration of flux which is then sensed by a hall effect device in the air gap. The internal circuit then generates a DC current in a feedback winding on the same core that exactly counters the flux generated by the test current. When the hall effect device senses zero again the right current is flowing through the feedback winding and then the measured current is proportional to the number of turns of the feedback winding and the feedback current needed to counter the test current. This technique allows measuring DC current with a transformer core and a sensor and some circuitry and the feedback winding. It can also sense AC current but usually the frequency is limited because the feedback has to continuously adjust to match the flux generated by the changing test current.

Many people just use a low value resistor and an amplifier then run the output to a analog to digital converter.
 
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