Electrical monitoring system?

[rdubs]

Hi everyone
2013 SO469.  I want to install a monitoring system which will track how much power is being used by some of the main DC loads, namely the cabin lights, refrigerator, nav instruments and nav lights.  Found a nice monitoring system called the Pico made by Simarine, and you have to route the wiring through some shunts for it to measure current.  All of these loads have wiring go through the main electrical switch panel at the nav station, but the panel uses printed circuitboards and wiring harnesses as opposed to individual wires leading to and from the switches, so I can't just reroute the wires.  Anyone have an electrical monitoring system and if so how did you tap in to the wiring to monitor the current draw?

Here is a pic of the back of the main electrical panel.  I thought about removing the fuses, using a multimeter to figure out which fuse goes with which switch, then run wires to and from the fuse receptacle to go to the monitoring shunt.  But if I knew which wires were which coming out of the harness, that would be safer to tap into.


www.23hq.com/Rdubsdubsr/photo/49088578/original

Many thanks
'Dubs

[vasko]

[vasko]

www.boat-vitals.com/display.html?link=11-101-ec2c284ef0-Celcius-dd_MMM_HH.mm-GPS5

I went for a wireless system custom build and adjustable

[Mistroma]

My boat has a diagram on the rear of the removable access panel and it shows what each fuse covers. The electrical diagrams also give this information, though it's a slow process to work it out initially.

I seem to remember Vasko's system giving very detailed information and also easy to configure and extend. A lot of items will be missed if only connecting via main switch panel, so extra wireless sensors are useful.

I was really only interested in overall amps. in and out. A cheap LED/Bluetooth unit from eBay solved the problem for about £18. I couldn't even buy the slip on sensor for that amount. It covers all charging (alternator, wind, solar, mains) and use (including windlass, engine start, heating etc.) and I could also build a data logger for a few pounds if required.


Battery state from Smartguage plus remote solar and wind charging displays fill in most of the blanks so I haven't felt the need for more detail.

[rene460]

Hi rdubs, the thing about measuring current is that you always need a shunt. All our meters are volt meters, and current is determined from the voltage drop across a shunt. On a multimeter, the shunt is inside the case, even on the old analogue meters.

So, for current sensing you need a shunt, or alternatively these days you can use a Hall effect sensor, which only has to be placed close to the wire, and I believe these things even come in wireless units for locating far from the display.  Some consist of a wire incorporated on a circuit board with the sensor located accurately in the right position.  Probably for calibration, bit it means it has to be installed just like a shunt.  Once you have a shunt or other current sensor you can use whatever display you chose. Clamp meters are also available for low currents these days, but I don’t know how to connect one into a permanent display. Mine has a 4 amp range for small currents.

A shunt has to carry the full current so is best installed by tapping into the existing wiring. It requires some thought as to where to mount it but the wiring from the shunt to the meter carries almost no current so can be cat 5 or other thin multi strand multicore wire. Or use a wireless device. Some circuits might be easier to tap into nearer the load rather than all at the panel. The circuit diagram will help you follow it once you learn to find your way around it.

If you want continuous readout of many different loads, to estimate battery state for example, you need to put in all the sensors as Vasko has done. But if you just want to know what various devices draw, you can put in a single shunt in the earth wire near the battery, to measure the total current, then measure separate loads by turning them on only one at a time, or just not the change as each additional load is switched on. Lights are easy this way, things like a fridge or water maker might require observation over a longer period as the load can vary throughout the cycle.

Rene460

[moonshadow]

I also have a 469 and would like better monitoring. But my needs are simple. All I need to know is when I need to start me generator etc to charge my batteries. With testing my batteries directly I find that the voltage at the batteries is higher than that shown in the Scheiber panel. About 0.4 volts different. Although I can’t fully determine where this voltage loss is occurring, cheap wiring or just usual loads like fridge and freezer etc, tht does not matter to my operational needs. As long as everything is getting the voltage it needs to work all I want to know is when batteries need charging. Since there is a 0.4-0.5 volt difference I have been charging batteries when the Schieber panel reads about 11.7 volts. Does this seem appropriate?
And if I want to get better information on status could I just add one simple sensor/shunt at the main battery breaker and just see total load, usage etc? I looked at some Xantrex units recently that seemed appealing. Any experience? Thanks.

[MalcolmP]

Nov 29, 2018 12:04:46 GMT moonshadow said:

..... With testing my batteries directly I find that the voltage at the batteries is higher than that shown in the Scheiber panel...

When I first fitted solar panels to my 39i I also installed a victron bmv monitor. It does need a shunt which it comes with plus you may need a short jumper cable made up to extend the earth.

The victron which measures at the shunt/battery connection always reads 0.5v higher than the Schreiber, so confirms your findings

If you fit a shunt so that you can measure amperage, which is really valuable, do check if there are any additional earth braids going to any of the housebank batteries. I found an extra one that went to the engine from a different battery terminal. You need all the earth's on the same shunt to measure total current draw.

[rdubs]

Nov 29, 2018 10:28:00 GMT rene460 said:

But if you just want to know what various devices draw, you can put in a single shunt in the earth wire near the battery, to measure the total current

Hi Rene460
Thanks much for the input.  I will definitely do this, install a shunt on the main earth wire to capture total draw.  That Pico system I am looking at has a 500 amp shunt which is more than enough to handle the 12V loads, even with an electric winch on high speed or inverter going.  The only downside is that the larger the shunt capacity, the less accurate it is at measuring smaller currents.  That is why I wanted to install the small 25 amp shunts on the DC loads which are almost always turned on, like the fridge and the nav instruments and cabin lights.  A 25 amp shunt would measure that draw much more accurately than a 500 amp one.  So I was trying to figure out how best to wire these small shunts into the existing wiring on the back of the panel, ideally without having to cut into any wires which can't be easily removed if someone wants to undo the modification.  So I think I will end up with 1) a main 500 amp shunt on the battery ground cable, and 2) inserting fuse blade connectors into the fuse receptacles and running wires from that to some mini-shunts.

But if anyone can think of a different or better way to wire in a shunt to these small DC loads I am all ears.

EDIT: What would be amazing is if anyone knew where to buy the male and female wiring harnesses which plug into the circuitboard.  Then I could just plug my own custom harness in to the factory one on both sides and run the shunts through the connecting wires.  Having a devil of a time trying to find those harnesses though.  They are the ones labeled J1 and J3 in the first picture above.
 
Best
Dubs

[rdubs]

Nov 29, 2018 12:04:46 GMT moonshadow said:

I also have a 469 and would like better monitoring. But my needs are simple. All I need to know is when I need to start me generator etc to charge my batteries. With testing my batteries directly I find that the voltage at the batteries is higher than that shown in the Scheiber panel. About 0.4 volts different. Although I can’t fully determine where this voltage loss is occurring, cheap wiring or just usual loads like fridge and freezer etc, tht does not matter to my operational needs. As long as everything is getting the voltage it needs to work all I want to know is when batteries need charging. Since there is a 0.4-0.5 volt difference I have been charging batteries when the Schieber panel reads about 11.7 volts. Does this seem appropriate?
And if I want to get better information on status could I just add one simple sensor/shunt at the main battery breaker and just see total load, usage etc? I looked at some Xantrex units recently that seemed appealing. Any experience? Thanks.

Moonshadow
That is odd, my electrical panel seems to show a good voltage.  At least what I think is a good voltage, it shows the battery floating at 13.6 volts (which is right for me having set the dip switches to AGM battery type), and after I turn the charger off the voltage settles down to about 12.7-12.8 which is a full charge for a 12V battery. 
Oddly though, on my chartplotter, when I go to the diagnostic and look at DC input volts, there it reads about 0.5 volts less than true battery.  So not sure what is going on there.

Either way, for your needs you may want to look at the Pico battery monitor system by Simarine, the same one I am about to get.  However all you would need is the main battery shunt, you wouldn't need the small branch shunts in addition that I am gunning for.  Pico sells a kit for 300 EUR that comes with the monitor display plus a 300 amp shunt.  
www.simarine.net/product/pico-one-package/

I plan to buy the kit that has the mini-shunts but also includes a 500 amp shunt just to be safe.  I'm not sure what wattage the electric winches take but I want a nice margin of safety in case another big load is running as well.  This one is 500 EUR.
www.simarine.net/product/pico-blue-package/

Check the pricing on Amazon as well, it is pretty good especially on the Blue package, it sells in USD what the amount is in EUR.

My friends on the fantastic youtube channel Sailing Zatara just installed this Pico system on their 55' catamaran and they love it.

EDIT: More to the question you asked, that Pico system uses some pretty advanced logic to compute the state of charge of the batteries, which it reads out in percentage.  It's more than just an amp-hour counter, it also uses some other inputs.  But that would definitely tell you a realistic charge level and thereby when to recharge.

[rdubs]

Update: I found the tech specs for the Pico shunts.  I was looking for the sensitivity to test my theory about the smaller shunts being more accurate / better resolution.

It looks like the big 300 amp shunt has a resolution of 0.01 amps.  The bigger 500 amp shunt has a resolution of 0.02 amps.  The accuracy is 0.6%.  Those resolution numbers are incredible sensitive.  Surprisingly, the resolution of the small 25 amp shunts is still only 0.01 amps, the same as the 300 amp shunt.  The 300 amp shunt can sustain a peak one-minute load of 400 amps, which is 4.8kW, and I can't think of any combination of loads which would draw that might for that long.  So I think I may go with the 300 amp shunt to get started and maybe install the small branch monitoring 25 amp ones later if I can figure out a good way to wire them in to the back of the panel.

[ohana]

On my 439 I fitted a battery monitor system last year . My goal was to know the status of charge of the house, engine and bow thruster batteries. I fitted a master volt system which is designed for 3 battery banks. It monitors voltage only for engine and bow thruster but this is ok as measuring voltage on a battery bank which is at rest gives a good indication of charge. The house bank has a current measurement and volt measurement, and the master volt gives overall info for the house batteries including total ah used, % used etc. The shunt is situated on the -ve side at the battery so records all current in and out. I can check current draw at any time but this is of course a total of all consumption (not individual unit consumption) and if charger / engine is on, just net flow in or out of batteries. But it gives me battery charge status at any time which is what I really need.

[vasko]

just FYI - I spent a lot of time investigating and improving my battery/electrical monitoring system ...

and as a simple statement I can assure you that all battery monitoring that are on sale currently have only two real measurements and the are the voltmeter and ampermeter - which are already on you boat installed by the manufacturer.

any battery bank states etc. are so useless and wrong that you better not look at them at all.

as for technology - the shunt is really outdated technology and the precision is awful - and remember a bigger is the shunt as worse the precision is ! 

if you do want the latest technology then it is actually a HALL sensor and not only the sensor is important but the ADC also - most ADC's are 10bits (and more likely 8 bits) which in reality with 200amps shunt will lead to about 1-2 amps precision and everything else is "guesstimate"

if you really want a good battery monitoring system - you need to write some simple code yourself ( or copy paste from github) 

use a good HALL combination with HALL sensors - e.g combine 5,10,20,50, and 200amps sensors and us the one that the current fits in it as a lower it is the precision is better. and use a ESP32 board which has a 12bit ADC in it and enough analog pins to connect multiple HALL sensors.  The total cost will be about £20 to £50 depends on the amount of sensors you connect. ( 1 sensor is about £5 and a board with Wifi, BLE, OLED screen, LoRa and ESP32 is about £15.

good sensors :

www.allegromicro.com/en/Products/Current-Sensor-ICs/Fifty-To-Two-Hundred-Amp-Integrated-Conductor-Sensor-ICs.aspx

[vasko]

A very simple and secure way to judge the state of chgarge of your bank is the amount that goes to the bank from the alternator if under 10amps you are almost fully charged - under 5amps can be considered full charged and under 1amp you need to stop charging 

[rene460]

Hi Vasko, that is certainly an interesting device.  I am totally with you on the 12 bit ADC, that would give a lot better resolution.

The main issue with shunts as I see it is the balance between the voltage drop across the shunt with the current being measured, and the ADC resolution.  With a good ADC I guess either shunt or Hall effect would do, following your guide line of the lowest rating to do the job.

For real accuracy, I would guess you would need to do a test calibration, whichever device you use, but I see what you mean about preferring the Hall effect device for small currents.

Rene460

[vasko]

the idea is to install multiple HALL sensors with different amps current used on a boat varies greatly - e.g. from 120-180amps fo rthe windlass to some small current for lights and navigation... e.g. you need a precise measurement for small currents and not so precise for big currents - example

you install two hall sensors one after other 50amps and 200amps -you start measuring the current from the 50amps and it it is =50amps ( e.g. >= 50amps)  then you measure the current on ten 200amps one and get the result of it - thsi way you have 4 times better resolution for up to 50amps and average after that...

the actual issue is that to measure everything on a boat is quite a big task - you have multiple battery banks e.g. main - bow thruster, watermaker etc. and I do not want cables everywhere - e.g. you go wireless , after that you need micro computers to any of teh measuring points .. and in the end it becomes very complicated and advance system and the current consumption of the measuring system itself become  important....  and in the end you return to a  simple volt meter and ampermeter...

this is my system - but I took it off after a year of running... as decided that a simple volt and amp meters is enough - I just put additional volt/amps meter is some places to be able to see for example my 3500W inverter with aircon connected to it or coffe machine how much roughly it consumes  

this was my system :

github.com/vtomanov/merix

[Mistroma]

Nov 30, 2018 2:29:20 GMT vasko said:

just FYI - I spent a lot of time investigating and improving my battery/electrical monitoring system ...

and as a simple statement I can assure you that all battery monitoring that are on sale currently have only two real measurements and the are the voltmeter and ampermeter - which are already on you boat installed by the manufacturer.

any battery bank states etc. are so useless and wrong that you better not look at them at all.

as for technology - the shunt is really outdated technology and the precision is awful - and remember a bigger is the shunt as worse the precision is ! 

if you do want the latest technology then it is actually a HALL sensor and not only the sensor is important but the ADC also - most ADC's are 10bits (and more likely 8 bits) which in reality with 200amps shunt will lead to about 1-2 amps precision and everything else is "guesstimate"

if you really want a good battery monitoring system - you need to write some simple code yourself ( or copy paste from github) 

use a good HALL combination with HALL sensors - e.g combine 5,10,20,50, and 200amps sensors and us the one that the current fits in it as a lower it is the precision is better. and use a ESP32 board which has a 12bit ADC in it and enough analog pins to connect multiple HALL sensors.  The total cost will be about £20 to £50 depends on the amount of sensors you connect. ( 1 sensor is about £5 and a board with Wifi, BLE, OLED screen, LoRa and ESP32 is about £15.

good sensors :

www.allegromicro.com/en/Products/Current-Sensor-ICs/Fifty-To-Two-Hundred-Amp-Integrated-Conductor-Sensor-ICs.aspx

I really thought your system was well thought out but overkill for me. I see that you came to the same conclusion after having fun with the build.

I wouldn't say it's true that all battery monitoring gear is useless. I find that Smartgauge is pretty good. It only gives %SOC based on HF pulsed Voltage measurement, no current measurement at all. It has no idea of actual capacity (e.g. 200 or 400Ah) is only reports n% of actual capacity. You get very accurate Voltage readings from two banks and SOC from one. I did find a white paper somewhere covering the technology I think they use.

It isn't perfect and tends to give 100% too early when charging. However, it rapidly drops to correct reading when discharging. I don't find this a big problem as all I really want to know is how low the batteries are before charging and how full they are each evening. I'm not on shorepower and Smartgauge SOC doesn't affect solar input either, so fairly accurate SOC during discharge is all I need. It does usually tie up pretty well with temp. compensated SG SOC.

The cheapo eBay Bluetooth/LCD monitor works well for me. It gives domestic battery Voltage, A, W, Ah & Wh in/out for about £18 and no shunt. No fun building it though, so I might add some data logging via Bluetooth & Arduino already installed. No brainer when comparing with expensive "marine" units doing much the same for much more money.

Where did you source the Hall effect sensors? Only units I came across needed to be fitted inline (Hall effect part was on the board). I had been looking for something to just slip over an existing wire (that's what the eBay module uses).

[vasko]

I use hall sensors from aliexpress but the inline one are more accurate...

If you use development board try
: Heltec LoRa 32, - has wifi, ble, LoRa , OLED and 2 core 32 bit CPU plenty of RAM ...

If you want low consumption use Feather 32u4