Any hints on shunt wiring, please?

[[3889]]

Are you sure that this device can measure from the same source as its power supply? Many require an isolated supply.

Not really sure about anything, TBH. My plan is to power it from the load output on my solar regulator and measure the regulator battery charging output. I'll report back, hopefully tomorrow if I don't fall at the first hurdle in getting it to work at all.

 

[William_H]

I would suggest that this meter does require an isolated power supply to run the meter. ie a 9v battery and switch as in the picture. I say this because your instructions say power supply +ve and -ve as separate wires to the inbut common. This is common for older style Digital volt meter type chips though s0ome modern types cn have the supply negative common to the input negative. If OP wants to run the meter off the ships battery then he needs an isolating power converter. This device switches the battery supply to AC then into a transformer which actually isolates the supply then to a rectifier hence to the meter.
Now a digital volt meter is fairly straight forward the -ve input being connected to ships negative and the +ve metering wire going to the ships +ve. In OPs case to solar +ve which might also be ships battery +ve or he could be wanting to measure solar panel +ve (20v) which may be higher and different to battery voltage depending on style of regulator. He does need to make sure that solar -ve is common to output (battery) -ve. ie no switching done in -ve line just +ve.
Now when it comes to measuring current things get a bit confusing. You are measuring voltage dropped across the shunt. Typically up to 200mv. So for a solar charge current the voltage will drop in the +ve wire with +ve toward the panel(controller) and -ve towards the battery. This means that meter input wires have +ve towards the panel of the shunt and _ve to the battery connection. But wait the meter has a common negative wire for measuring voltage and current. So that common negative wire must go to ships -ve. But the shunt is in the +ve line.
So in this case if I have discerned properly the shunt will have to go in the negative line of the solar panel. So that the volt meter negative which is also current meter negative will go to the panel end of the shunt. The current measuring +ve will go to the battery end of the shunt. NOw this will mean that the volt dropp of the shunt will be subtracted from the battery voltage but this will be a very small error. (depending on current flow). All very complicated for a simple wiring question. (and I may be confused anyway)
good luck olewill

 

[[3889]]

All very complicated for a simple wiring question. ...
good luck

It is for me, certainly, and I'll need it. A switched 9V pp3 for power is an option. Thanks.

 

[Rigger Mortice]

I would suggest that this meter does require an isolated power supply to run the meter. ie a 9v battery and switch as in the picture. I say this because your instructions say power supply +ve and -ve as separate wires to the inbut common.

Unlikely I suspect, as it is being offered for use in a car.
I think the reason for having separate wires to power the meter is more likely to be so that you may use a separate power supply if you are measuring voltages over the specified 30volts needed for the meter itself.

 

[theoldsalt]

Are you sure that this device can measure from the same source as its power supply? Many require an isolated supply.

I also believe that an isolated power supply is required. Yes a separate battery could be used but it can be more convenient to use the single source

If measuring the same source as power for the meter this type of component is required.

http://www.ebay.co.uk/itm/New-High-...ther_Computing_Networking&hash=item45fdda9848

 

[[3889]]

Got it working - reasonably accurate, about 10% over the amperage shown by my multimeter which is good enough for me. Meter is being powered by the load output of this 20A regulator:
http://www.ebay.co.uk/itm/10A-20A-3...158545?pt=UK_Gadgets&var=&hash=item51aba66051
Changing power supply to 9V battery makes no discernible difference to readings.

 

[Richard10002]

Got it working - reasonably accurate, about 10% over the amperage shown by my multimeter which is good enough for me. Meter is being powered by the load output of this 20A regulator:
http://www.ebay.co.uk/itm/10A-20A-3...158545?pt=UK_Gadgets&var=&hash=item51aba66051
Changing power supply to 9V battery makes no discernible difference to readings.

I messed about with one of these "cheap" meters but, after faffing about and confusing myself for a few weeks, I got a NASA BM2 ....... It just works and the bonus is that you get cumulative Ah and a stab at %age SOC.

 

[[3889]]

I got a NASA BM2 ....... It just works

But do they? I would happily pay for the NASA kit but my impression is it provides only an estimate based on the same sort of information my cheapo set up gives, but costs 10 time more and is more complex to fit.

 

[Richard10002]

But do they? I would happily pay for the NASA kit but my impression is it provides only an estimate based on the same sort of information my cheapo set up gives, but costs 10 time more and is more complex to fit.

Instantaneous Charging and Discharging Amps will be as correct as yours. Volts will be as correct as yours. Ah in and out is merely a function of instantaneous x time, so correct.

I said that the SOC is a stab, so you have to use your judgement on this, or ignore it.

I followed the instructions and found it less complex than yours - I have one like yours sitting unused on a shelf. I note the reading on the NASA every time I pass it, (many times a day ).