Wiring te load on AiLi battery monitor

[agesilaus]

I just got an AiLi monitor and am wondering if I can wire the shunt between the battery and converter, at the converter? It would make placing the meter a lot easier.

[MrWizard]

The monitor meters I used did Not have a plug on the shunt,
Power wires and sense/sampling wires
Are separately hard wired install, No Common Neg on the SHUNT !

I No longer use shunted meters for RV batteries
I use power monitors that have Hall Effect Sensors for D.C. Current
And can be placed in either path of the power circuit without worrying about negative connections
My preferred install is the primary/main positive of the house battery bank

[FWC]

The AiLi (which the OP asked about) only has 3 terminals:


The supply and sense negative are common (P-) and thus can only be installed on the negative.

[BFL13]

Why can't the shunt go on the positive post with the pos wires all on the other end of the shunt, and with the (Trimetric case) two black wires on the outer side of the shunt and the one white wire to the inner(post side) side for measuring across the shunt going to the display as now, and the red wire that goes to the positive now go to the neg instead?

That makes a circuit for powering the display I think. Not sure about the three wires on the shunt location--would they be reversed so the white is now on the outer end and the two blacks on the inner? (to be in the same line up with the current flow)

[FWC]

The AiLi monitor being discussed here, (as well as the various Victron monitors and most others) all use the shunt negative lead as the return for the meter power supply. They cannot be installed on the positive side of the battery.

MrWizard wrote:
Don't know what shunt monitor system you may have had problems with,
But the ones I installed, used separated sensing wires pair (shunt to meter), and meter power wires pair, worked perfectly with shunt in the positive main path,
Power for the meter/monitor should always come from separate wires going directly to the battery, to always supply and isolated power path, even better from a separate power supply and not the battery be measured

[MrWizard]

Don't know what shunt monitor system you may have had problems with,
But the ones I installed, used separated sensing wires pair (shunt to meter), and meter power wires pair, worked perfectly with shunt in the positive main path,
Power for the meter/monitor should always come from separate wires going directly to the battery, to always supply and isolated power path, even better from a separate power supply and not the battery be measured

FWC wrote:
You cannot put the shunt for the battery monitor on the positive terminal of the battery! While theoretically the shunt can go on either side of the battery, practically the shunt is also providing the negative for the power supply for powering the meter itself. If you put it on the positive terminal, and the power lead to the negative terminal you will have provided reverse polarity to the monitor.

Furthermore, if you put the shunt on the positive lead, you have a high common mode voltage, which makes measuring the voltage drop across the shunt more difficult.

[agesilaus]

No they are combined I don't split them.

[BFL13]

agesilaus wrote:
I ordered the meter extension cord, it's out for delivery right now. I'll put the shunt in the battery compartment. I have two banks of 6V, I assume I connect both negative leads to the shunt.

Do you mean you have two separate banks of 6s now and want to keep them separate? You would have to pick which one to monitor. If they are now in parallel, then there is still only the one wire from shunt to neg post.

If those two neg leads are to the frame, they might already be putting the two banks in parallel? What is the set-up?

If you have the two banks sharing all the loads and charging so it is assumed that each does half such as when an inverter has two pos and two neg wires from it, and one set goes to each bank, then I don't know how you would work the shunt in. Some converters have that arrangement too, where the two banks each are supposed to get half the charging amps

[agesilaus]

I ordered the meter extension cord, it's out for delivery right now. I'll put the shunt in the battery compartment. I have two banks of 6V, I assume I connect both negative leads to the shunt.

[FWC]

You cannot put the shunt for the battery monitor on the positive terminal of the battery! While theoretically the shunt can go on either side of the battery, practically the shunt is also providing the negative for the power supply for powering the meter itself. If you put it on the positive terminal, and the power lead to the negative terminal you will have provided reverse polarity to the monitor.

Furthermore, if you put the shunt on the positive lead, you have a high common mode voltage, which makes measuring the voltage drop across the shunt more difficult.

[MrWizard]

It's very common to put the shunt in the negative wire battery connection, But in most cases it is not absolutely necessary,
The shunt is just a measuring point, away to measure amps via a calibrated voltage drop, example 0.01v drop equal 0.01 amps on the meter,
Negative is used most often , mainly because there are usually less connections on the negative post, so usually only one main negative wire has to be moved from battery to shunt, the vehicle frame is the negative BUSS BAR for most wiring, most meters using stunts will work just fine, no problems, connected to the positive post, you just have more wires to move and connect to the other end of the shunt.
I have done this with no problems, when the negative post had clearance problems for mounting a shunt

[agesilaus]

The neg path from battery to converter/DC panel might be mostly frame, so you will need a real wire from the shunt to the battery however long it has to be. (and it has to have the ampacity to carry the total amps of all the 12v loads--not easy to make that long wire that fat)

That answers that, I actually have quite a bit of number 2 cable, might be bigger, but the idea of running that under the frame does not appeal very much. I'll break down and buy the extension cable from the OEM for the meter. Thanks for the helpful replies. Next week starts electrical work week on the RV...heh. Assuming I get mechanical work done before then.

[BFL13]

The battery will be neg grounded to the frame and some things might use the frame as part of their neg paths to the battery.

You disconnect the neg wire from from frame to battery at the battery post and put that wire to the frame on the shunt with the other load wires. But--you could just leave it disconnected from the battery and run another neg wire from the frame by the converter to the shunt.

The neg path from battery to converter/DC panel might be mostly frame, so you will need a real wire from the shunt to the battery however long it has to be. (and it has to have the ampacity to carry the total amps of all the 12v loads--not easy to make that long wire that fat)

It is usually a lot easier to put the shunt close to battery neg post, so the shunt to neg post wire can be short and fat, and the other wires that used to go on the neg post are right there to go on the other end of the shunt.

But then that is why some monitors have such a long wire that goes from the shunt to the display! Finding a route for that wire can be an issue of course. Could mean putting the display in a less convenient spot, but you don't need to see it every minute. (After you have had it for a while it is less of an attraction 🙂 )

[DrewE]

What does the documentation for the monitor say? Often they require the shunt to be on the negative side of the battery, and not the positive.

If you have anything that connects between the battery and the shunt (any loads or ground connections, as applicable), the battery monitor will not be able to see the current that goes through those connections and give erroneous readings for that reason.