Battery Monitoring Cheapskate

DougH

I've just been using an Epever solar controller monitor to keep an eye on our solar battery bank voltage. 

I know... not very accurate since voltage drops significantly under load.  But I figured if the Epever display stayed above 12.0V even under load for the battery reading I'd probably be well above the 50% depletion level on a four battery solar bank.  But I've been tempted to do a better job with all the recent battery monitoring threads.  That's the problem with this forum...  it always costs me money.  

So I finally picked up one of these cheap $28.99 multimeters:

DROK DC 0-300V 200A

https://www.amazon.com/dp/B07B4CWKRJ

It only comes with a six inch set of wires to the power connections and a Hall sensor.  No shunts to wire.  So I connected the red & yellow leads together, then ran that line, the black line and the three Hall sensor wires through an 18AWG six foot long set of wires.

Then I put the sensor around the positive leads from solar controller to the battery and the lead from the battery to the inverter fuse.



They barely fit in the sensor.  There's a slight load from the monitor, but you can always run a switch to turn it off and it will retain its stored settings. 

With the inverter off and only two batteries connected (250Ah), the charging current from the setting sun was properly negative... 



And then once I turned on the inverter (that powers the whole camper) and waited a while for the converter to settle down it showed a net positive draw on the batteries from the converter, lights, Jensen, etc... 



...and the capacity remaining eventually dropped in the right direction from 250Ah to 249Ah.

It may be off 0.1 or 0.2A resulting in integration errors, but you can set the battery bank size, the voltage at which it should clear any integration errors and consider the battery full, along with a few non-audible alert voltage and current levels.

Now I just have to get some wood to build a small box that matches the back cabinets to mount all the weather and power monitors / switches into...

pthomas745

I have no idea how this works but it looks great.  I'm always amazed by the expertise and creativity of Tab owners.

DougH

Me neither.  Maybe it's just a Fluke.   

I am envious of all the bluetooth 712 folks though.  Next thing you know, when finishing up a morning walk we'll cross a predetermined geofence with our phones to turn on the inverter that warms up the espresso machine.

DougH

Hmmm...  a new wooden enclosure similar to the cabinets (once varnished) for the power meters looks tolerable for now, but it's tempting to borrow the pocket storage design element from the 400, and build a platform from the 320 window to the rear cabinets to stow the power monitors and switches along with extra knick knacks.

So eventually this... 


...needs to look more like the back of something like... 


...and we can always find a use for the extra storage.

Cbusguy

If you search amazon long enough and want to invest the time there are a huge number of chinese knock offs of more expensive solutions.   youtuber will prowess showed a $30 shunt meter very similar to the victron.   Here is a link to it. Doesn't have bluetooth,  but honestly it doesn't need it.      

@DougH nice job on the finish install.   do all of the display light time out and shut off?

DougH

@Cbusguy ; The Epever MT50 monitor times out (a bit too quickly); the DROK does not (a button turns light on/off). 

Thanks for the link... you would think Victron would sue such a similar knock-off.  I did follow Will Prowess's suggestion for a Giandel 2200W sine wave inverter instead of the better rated $500-800 inverters for that power level...  so far so good.  My motivation for a more generic multimeter and different approach than a single shunt setup was to simply monitor charging (with inverter off) and depleting (at night with no moon) currents or net current during the day while seeing all the numbers on one screen.  Guess that's also the advantage of the Victron BT app though...  seeing everything at once. 

Missing on the DROK screen is an intelligent prediction of time remaining to 50% AGM bank remaining and an auto-inverter cutoff option.  Can't expect too much for twenty bucks though.

With the air conditioner running with other appliances I can see up to 40A, but the LG 6500BTU unit I'm using cycles the compressor even if it's 90F in the camper and the thermostat is set for 60F.  More frequently, if it's not 100F outside with camper in direct sun, the compressor is only on less than 50% of the time.  So with 375Ah bank that's maybe eight hours of cooling if it's not too hot, but with a longer recovery with only 200W on the roof.  Still, it would be nice to see a 15 minute window averaged current used to predict time remaining (although typically I've never run the A/C more than a few hours).

Cbusguy

@DougH I received my cheapo victron clone.   Now I just need the contactors to finish up so I can get the solar on the roof and the off grid power installed in garage.  I have all this stuff piling up for the install

DougH

Sometimes spring projects are almost as much fun as the camping they lead to..