Battery Monitoring -- How I Done It --

The BM2 v8 custom battery settings, anyone have suitable figures for lithium battery or is the fact that lithium stays high right til it dies not going to work with it?
 
they stay fairly constant over 80% of the range . .

but do drop voltage slighly. . .



eg this vallence sheet.

from 100% full @ 13.25v

it drops to 12.75v by 80% depleted ( or 20% soc)

so thats 0.5v drop. over 80% usage of the battery

after that the voltage plummets.

1658091897070.png


.....




so make up you profile on that assumption.

this is my own discharge testing . . . drawing 50A from the battery.


again you can see it drops about 0.5v from 100% down to 20%.

then 20% down to 0% it falls off the clif.


1658092174724.png


...







....
 
the BM2 is a great voltage logger . . .

but for lithiums, if you want an accurate state of charge meter . . .


you need a current shunt.


see post #2 - Battery Monitoring -- How I Done It --


....



I've tried a few . . but the best one by far is the victron smart shunt ( or BMV712)











1658092335695.png



++++







SmartShunt%20500_nw.png

SmartShunt​

The Smart Battery Shunt​

The SmartShunt is an all in one battery monitor, only without a display. Your phone acts as the display. The SmartShunt connects via Bluetooth to the VictronConnect App on your phone (or tablet) and you can conveniently read out all monitored battery parameters, like state of charge, time to go, historical information and much more.
Alternatively the SmartShunt can be connected and be read by a GX device. Connection to the SmartShunt is made via a VE.Direct cable.
The SmartShunt is a good alternative for a BMV battery monitor, especially for systems where battery monitoring is needed but less wiring and clutter is wanted.
The SmartShunt is equipped with Bluetooth, a VE.Direct port and a connection that can be used for: monitoring a second battery, midpoint monitoring or a temperature sensor.
Models:500A, 1000A, 2000A






1658092382790.png
 
.

im happy to say that Victron has finally sorted there stuff...


now the units have data logging..


via BT only ( not VRM )

but they store up to 180days of data to be reviewed.


and best of all its store in NVM so the data is kept after a power down.



1660113120297.png1660113136167.png



#
 
  • Like
Reactions: mmi
do the FW update for FW v2.41





1660113293706.png
 
  • Like
Reactions: mmi
Just ordered the Victron BMV 712 Smart. Shall probably have some questions once it and my Roamer lithium battery arrives!
 
BM2 data readout . .


i done a Solar job a couple months ago on a family caravan.

twin 100W renogy panels.
Renogy Voyager mppt controller
twin AGM xtreme batterys,
USB + 12v + voltmeter + switch
+ BM2 voltage logger.

+++++++++++++++



first time back, so a good chance to see what the data looks like


++++++++++++++



1663775641568.png

++

2 week plot,


1663775666106.png

+

7 day plot.

1663775686005.png


++



various day plots. . . .

1663775711200.png1663775728576.png1663775738542.png1663775753634.png1663775720770.png


here is what happening . . .


7am - sun up and mttp charger moves to BULK mode charging battery to full by 1030am ( RED )


1020am-1230pm - charger in ABSORBTION keeping battery full. (yellow)


1230pm-630pm - charger in FLOAT - keeping battery topped up till sunset ( blue )

after that the battery voltages slowly drops as the fridge, lights , chargers etc etc use power. . .

untill the next day when the cycle starts again.


1663776035107.png


.






this is the unit i fitted to the battery . .






1663776108960.png


.
 
The BM2 looks great! Can I ask, is that all you need to monitor? Do you need a semi permanent connection to the computer logging the data or does you download routinely? Daily, weekly? Thanks for sharing!

I have the budgets 2 output USB monitor. It has a voyage drop between the battery and the readout, but I know that so can monitor my AGM battery and know the true voltage.
 
The BM2 looks great! Can I ask, is that all you need to monitor? Do you need a semi permanent connection to the computer logging the data or does you download routinely? Daily, weekly? Thanks for sharing!

I have the budgets 2 output USB monitor. It has a voyage drop between the battery and the readout, but I know that so can monitor my AGM battery and know the true voltage.
yes. . . and a phone or tablet to display it on. .

the unit stores around two weeks worth of data.

the phone APP will sync via bluetooth all the time, so provided the app updates a few times a week you will have an indefinite log.


1663783436813.png1663783445487.png



++++++++++++++++++++++++++++++











++++++++++++++++++++++++++++++++++++++++



have a look back here:




+++++++++++++++++++++++++++++++++++++++++
 
- NEW PRODUCT for 2022/2023 -


Now with BT & APP.

+++++++++++++++++++++++++

TOPDON BT20 Car Battery Tester, 12V Battery Load Tester, Voltage Test, Unlock Cranking Test and Charging Test in App, Cost-Effective Automotive Battery Tester for Cars Trucks SUV ATV Boats Vehicle​











1670168370418.png


About this item​

  • 【An Affordable Car Battery Tester】Features 4 testing modes: battery load tester (range 10V-20V), voltage test, cranking test, and charging test (alternator tester). Load tests batteries safely and accurately. For use with 12V lead-acid batteries.
  • 【Expanded Voltage, Cranking, and Charging Tests】Connect to this car battery tester via Bluetooth to get additional cranking, charging, and voltage testing capabilities. Easily view real-time voltage waveform graphs with data playback functionality.
  • 【Improved Speed & Accuracy】Advanced conductivity testing technology (up to 99.5% test accuracy) quickly delivers results so you can rapidly diagnose and solve battery health problems.
  • 【Comprehensive Vehicle Coverage & Multi-Language Support】Plug & play operation. Simply connect the testing clamps to the battery and you are ready to analyze. This 12V battery tester works on a variety of vehicles equipped with 12V batteries such as boats, motorcycles, ships, and trucks. Also this auto battery tester easily switches between 8 different languages.
  • 【Ideal For Everyone】Reverse polarity and "no spark" protection for extra safety. Long 19.75" clamp leads allow testing from inside or outside the vehicle. A perfect battery analyzer and load tester for small repair shops & car owners alike. Makes a great gift for car enthusiasts.
 
  • Like
Reactions: CAB
also FWIW

a great price on BM2 battery monitor & voltage logger . . . . .










1670168528837.png


About this item​

  • FREE STICKY PAD ✅ Additional Unique Accessory for FREE So You Can Easily Attach Your Bluetooth Battery Monitor to Your 12v Battery.
  • FEATURES ✅ Alternator Output Volt Tester | Access to Historical Data Graphically | Short-circuit & Reverse Connection Protection | 3M Range | Ignition Testing |Charging Testing & More.
  • UP TO DATE ✅ When Car Battery Monitor is Installed, Receive Alerts & Notifications of Battery Condition on Your Mobile Phone when in Bluetooth Range. Simultaneously Monitor Up to 4 Batteries.
  • VERSATILE ✅ Perfect for Camper Van Battery/Leisure and Everyday Vehicles. Compatible with all 12-Volt Car Batteries; Voltage: 6-20V, Connect with Battery Directly, NO CODE, Free App for iOS & Android users IOS: IOS 7.1 & Later & Android 4.3 & Later.
  • EASY TO OPERATE ✅ Connect and Go, Check Battery Condition on Phone App via Bluetooth 4.0 when device is installed. Check Charging & Starting System, List Time of Each Driving.


1670168564068.png1670168575164.png
 
NASA compact battery monitor

I have one of these hooked to two 95 lesuire batteries but the gauge doesn’t seem accurate anyone else use these if so how do you find these
 
Should a BM2 battery monitor be connected directly across the battery posts, or with the negative side connected to a body earth? T6.1, smart alternator, VW original shunt on the negative battery post.
 
Should a BM2 battery monitor be connected directly across the battery posts, or with the negative side connected to a body earth? T6.1, smart alternator, VW original shunt on the negative battery post.
on the posts
 
Thanks @Loz. I thought so, but VW main agent said otherwise ... :rolleyes:
Only the BM2 goes directly across the battery, as you want the accurate voltage without the loss of going over the shunt. ALL other negatives go to the chassis.
 
Should a BM2 battery monitor be connected directly across the battery posts, or with the negative side connected to a body earth? T6.1, smart alternator, VW original shunt on the negative battery post.
Technicaly VW are correct, and nothing should go on the NEG battery post.

But as @Loz says going direct across the battery is fine as the BM2 is so low power that it's draw on the battery is negligible over the time the van is parked (unless it's layed up in storage for long time, in which case use a chassis NEG).

I had mine direct across the battery for a year or so, however I have now moved it over to a chassis NEG by using my own fusebox next to the starter battery.


More info here.








.
 
Cold weather, Lithium batteries, Victron Shunt and a false SOC reading.. . . . Cold weather GOTCHA to be aware of.


we`ve had a recent cold spell in the UK, and down to -5C in London, which only happens a few times of year.

i love it as its a great opportunity to test cold weather performance of all this tech. .

in this case the awesome ROAMER SB230gen2. -



in particular the cold weather protection that kicks in below 0C. . .



+++

here we can see its 634am in the morning (18/1/23) the battery is -2c and its showing "charging off"

this is the expected mode of operation where the battery will allow outgoing power, but is actively blocking any incoming power.


1675879448538.png

here you can see the "UTC/1" alarm - that shows the battery BMS is blocking any charge power.

1675879577620.png

the battery BMS was showing 99% SOC . . . which had slightly drifted from the true battery reading of 93%,

this drift is caused by the battery BMS not detecting all of the low power draws (below 500mA) . . . this is normal for nearly all lithium battery's, infact the ROAMER is one of the better ones, detecting power draws down to 500mA.

but the true battery SOC can be monitored with a Victron shunt . . . . (which will monitor down to 0.1A / 100mA)

the Gotcha is what happened next . . .


while watching the reading the Victron shunt just jumped from 92% SOC to 100% SOC. . . right in front of my eyes.


hold on - whaaaaaaat ?


it can be seen here:

you can see the temp is still below Zero, so the battery is blocking any incoming charge. (so there is no way the SOC should increase at all)

but you can see the shunt SOC data suddenly jump from 92% - 100% SOC instantly .?

1675879891824.png

the reason for this is the way the Victron shunt is programmed to detect the 100% SOC point. . .


we can see the ROAMER battery internal voltage is 13.26v . .


1675880053708.png

but with the engine running. . . the Renogy DC-DC charger is putting out 14.4v to try and charge everything up. . .

1675880110256.png

checking the Victron settings. . . we can see that the trigger point is 14.2v for 60seconds with less than 3% tail current . . .

so at this point the shunt assumes that battery is FULL and not accepting any charge. . . . because its detecting the 14.4v on the battery terminals, and not seeing any power going into the battery.

but in reality . . . the battery IS NOT charged, its just protecting itself by blocking the charge power. . . due to the cold temp conditions.

so the 100% SOC reported by the Victron shunt is false. . . .at this point.

you can see the point when the SOC jumped from 92% to 100% here ( while the temp is below 0c):

1675880336695.png
and here:

1675880367805.png



+++++++++++++++++++++



so what now?



well once again we can see how battery BMS and SHUNT SOC readings can fool you. . .

on this occasion due to cold weather. . .


this fix is simple, and the same as the BMS DRIFT issue i highlighted before. . . - just fully charge the battery.


as with the BMS drift. . . . even though the battery is showing 100% soc, it will accept a charge - untill its full.


if you have a Victron charger that meters charged power you can use that to quality the amount of BMS drift. . .





+++++



so if its cold. . . . . or the vans been sitting for a while don't 100% trust those SOC readings . .

get the battery charged up again and your good to go.. . . . . . even though that charge may take a bit longer than expected.


1675880635600.png



related - BMS XMAS DRIFT



#
.
 
Last edited:
Back
Top