Shunt based battery monitor wiring issue

Dzefa

Hi guys,

I got my Aili battery monitor installed (350Amp version) by a RV company as an addition to the solar set up. Link to battery monitor: https://www.amazon.com/AiLi-Battery-Monitor-Voltmeter-Motorhome/dp/B07FGFFHC6?th=1

However, it is not working correctly and I suspect they wired it incorrectly. The following two issues I have isolated:

• The charging Amps are only shown for the current coming in through the Solar power setup. Besides solar I have the option of charging through the engine alternator & shore power inverter charger. Charging through these last 2 options has no impact on the battery monitor screen.
• The discharging amps are added on top of the charging amps. Through my solar panel it shows +13 Amps. When I turn on all my devices the current increases to +20 Amps or so. Whereas it should distract the -7 amps discharge and show a net of +6 amps.

I contacted the company to tell them about this issue, however they have no clue how to wire it differently. Does anyone have any clue what the wiring issue could be? Simple fix hopefully?

Thanks a lot!

mcgivor

Where is the shunt located in the system? 

Dzefa

Hi again McGivor!

Since I do not have a wiring diagram of the whole system, I took a picture and hopefully that can explain the location of the shunt in the system. As I read, all negatives from the battery should go through the shunt. However, in my beginner observation, it seems that this is not the case. For the complete picture:

Charging:

• Solar power
• Engine alternator
• Smart converter/charger shore power

Discharging:

• Smart converter/charger
• Led lights
• 12V plugs
• 12V Fridge
• 12V Fan (2x)
• Water pump
• Diesel Heater
• Thats all I think 🤔 

mcgivor

There should be only a single negative connection from the battery  to the shunt all others go to the other side of the shunt to prevent alternative paths for current to flow, learning through mistakes is the best form of education. Just an observation, all positive and negative charging and dischargeing should be on a single battery terminals diagonally opposite to attain ballance in a parrallel battery arrangement, it appears that this is not the case, but hard to say without knowing where all the wires go in an image.

Dzefa

"There should be only a single negative connection from the battery  to the shunt all others go to the other side of the shunt to prevent alternative paths for current to flow"

So the wire with the green arrow should move there, correct? What about the wires with the blue and yellow dot, are they ok?

Does this also explain why the discharge is added on top of the charge? Rather than taking it as a minus. Or does this have a difference cause?

"Just an observation, all positive and negative charging and dischargeing should be on a single battery terminals diagonally opposite to attain ballance in a parrallel battery arrangement,"

Could be the case, I have no clue Which wires would have to change for this? If this doesnt change, is it a big problem?

Thanks McGivor!

mcgivor

Green arrow wire move to indicated location, blue square is battery interconnect leave alone, the red coming out the wall should go to the near battery, positive interconnect is good. Can't see where the inverter negative leads to but it should go to the same side of the shunt as the green arrow wire

Once the above amendments are made all will be correct, the diagonally positioned negative and positive will reduce the possibility of one battery being favored over the other, so it is important in the long term. Hope I'm deciphering the picture correctly, I'm assuming the red coming out of the wall to the far battery is from the charge controller, am I correct?

Dzefa

Ok step by step I am getting there Thanks!

So the 2 blue wires go to the P side of the shunt.

"the diagonally positioned negative and positive will reduce the possibility of one battery being favored over the other"
Which alterations do I need to make in order to attain this?

"Hope I'm deciphering the picture correctly, I'm assuming the red coming out of the wall to the far battery is from the charge controller, am I correct?"
I think so as well. What is going on exactly behind that little wooden wall over there is a big mystery to me.

"Once the above amendments are made all will be correct"
See the blue lines. Do you think this will also solve the issue of discharged Amps from the battery being displayed as charged Amps on the battery? Right now the fridge drawing 1.5 Amp from the battery is shown as charging 1.5 Amp to the battery. Or is this a different issue?

mcgivor

Yes move the negatives as indicated by the arrows, regardless of where the red coming out of the wall comes from, it should go to the near battery, leaving only the single interconnect on the far battery.

Dzefa

Step by step

I added one more arrow, like this it is correct? And the last arrow is to achieve the "the diagonally positioned negative and positive", correct?

I am not sure if your "Yes" above is also in relation to the question of whether it will solve the "Discharge showing as charge issue". Is this the case?

mcgivor

You've got it, as far as I can see, not only will this be the correct configuration it most likely will solve the shunt issue, as everything now passes through the shunt, the added benefit of having diagonal connection is for the most part, circumstantial. Let us know the observations once the changes are made, my day is coming to an end, I'm probably at least 8 hours ahead, so goodnight.

Dzefa

Thanks! I am going to try this out tomorrow and let you know how it went.

BB.

Here is the reasoning and examples of connecting parallel battery strings:

http://www.smartgauge.co.uk/batt_con.html

You might at some point want to build a negative (and positive) common battery bus... You will probably run out of room to stack connections. (negative bus is connected to "Right side"/NOT Battery Side of Shunt).

Here are some Bus Bars (lots to scroll through--Cut wire ends vs bolt up terminated wire ends):

https://www.solar-electric.com/search/?q=bus+bars
https://www.solar-electric.com/midnite-solar-shunt-busbar.html

-Bill

Dzefa

Thanks, interesting read!

Dzefa

@BB. & @mcgivor Thanks guys! I rewired everything how you recommended and the battery monitor is working perfectly now. Thanks for your help!

mcgivor

Good to hear you've accomplished one hurdle, how is the other one posted, the charging questions?

Dzefa

Yes, I am very happy with it, thanks heaps! To test the charging more thoroughly is my next step. However, since yesterday I saw the 13A charge (with the battery at 12.88V) rather than the 2A I saw before, I am more confident about the setup.

For now I am planning to change the "Boost Charge" from 14.6V to 14.4V & change Equalize time to "0" and leave the other charging parameters intact. Or do you have any further recommendations? Below I posted the list.

Another question. Right now the boost charge is at 14.6V. However, when the solar panels are charging the batteries the MT50 display shows 14.8V or even 14.9V. Based on the parameters I would expect that the MPPT keeps the voltage at 14.6V during the Boost/Absorption phase. How come it is higher than that? Is that because the Charge Limit is at 15.0V?

• Batt. type: User
• Batt. AH: 400AH
• Temp comp coeff: -3mv/C/2v (unchanged)
• Rated voltage: Auto
• Over volt Disc. 16.0V
• Charge Limit: 15.0V
• Over volt rec: 15.0V
• Equal charge: 14.6V
• Boost Charge: 14.6V
• Float Charge: 13.8V
• Boost Rec: 13.2V
• Low volt Rect: 12.6V
• Under volt Rect: 12.2V
• Under Volt warn: 12.0V
• Low volt Disc: 11.1V
• Discharge 10.6 V
• Equalize time: 120 min
• Boost time: 120 min

 

BB.

AGM batteries do not like high charging voltage (in general). It causes them to gas (hydrogen and oxygen) out the pressure relief valves and permanent loss of water. Shortening their lives.

Also can cause battery to overheat.

If you hear venting, the batteries are being overcharged.

Bill

Dzefa

@mcgivor Just one more question. From this picture are you able to judge if the shunt is safely installed? Someone commented me that it is not safe right now since there is no fuse on the positive connecting to the shunt. 

Cheers!!

mcgivor

There should be an overcurrent protection device preferably as close to the battery as possible with a rating of 120% of the maximum current carrying capacity of the conductors, on the positive. There may be a breaker on the wall, can't tell definitively by the picture but it appears so, nit pickers my judge that as being too far from the battery, a fuse could be connected directly to the battery terminal to maintain the breaker in it's convenient location, which is what I do.

Dzefa

Thanks @mcgivor !