I have just installed a BMV 700 and after syncing twice the battery % starts at 100% and constantly drops.
My smart charger is powered and shows stable activity.
My question is this. My house battery negative cable is in series - connected to - the cranking battery with the shunt inserted in-line right next to the house battery terminal.
Is the cranking battery causing the system to see the discharge, but not the recharge?
Here’s the progression: house battery terminal - cable - BMV 700 shunt (inserted in correct direction) - cable - negative terminal cranking battery. (The positive follows a different path with two separate lines out - one from house and one from cranking batteries.
So - my set-up complies with the diagram which has the BMV 700 shunt attached right next to the house battery with that negative cable going to the cranking battery.
The following was the set/up when I purchased the boat:- the house negative cable attached to the cranking negative and then on from there.
However, the Bavaria wiring diagram shows the cranking battery negative going to the house bank and the final cable leading out from the house bank. I’m not sure if the battery order in negative cable makes any difference.
The only other thing I can think of is that the BMV 700 has only one input on set-up - that’s the batteries’ amp hours. I have two house batteries each with 140 ah - I assume I input to the BMV 700 set-up - 280 ah (2x 140 ah)? Is that correct?
Best to give a screenshot of the BMV battery settings.
And voltage set points of your charger.
Also the house battery has not been properly cross diagonally wired for even charge/discharge currents.
1 battery will work harder than the other, and fail early.
Thanks @water_rat for your observations. I’m really keen to hear about the way that the house batteries are cross diagonally connected. I purchased the boat in March and this is what I inherited.
From the photo I uploaded can you tell me how the house batteries should be configured? I appreciate the help.
Hi Water_rat - I finally understood (duh) - the positive should go to one battery and the negative to the other - instead my set-up (inherited) was both connected to one of the house batteries - many thanks.
I have rectified that (which will help my battery longevity) and reset everything, but my BMV 700 is still counting down to zero capacity (it reached zero overnight before the battery lead swap this morning but clearly the house batteries were not discharged).
What else can I check? Somebody mentioned in the chain here (I can’t find it now) what charger I have. I have a ‘Sterling Power Products - Advanced Digital 4 Step Switch Mode Battery Charge /Power Pack’ which looks pretty basic and looks as though it was probably installed new by Bavaria in 2005.
I have emailed Sterling Power to request the voltage set-points.
This is what I see in setup and because there are 70 settings I’ve given only the first 30 or so, as other than 01 - 280Ah, these appear to be all set Factory Defaults.
01 BATTERY CAPACITY - 280 Ah
02 CHARGED VOLTAGE - 13.2V
03 TAIL CURRENT - 4%
04N CHARGED DETECTION TIME - 03
05 Peukert exponent - 1.25
06 Charge Efficiency Factor - 95%
07 Current threshold - 0.10A
08 Time-to-go averaging period - 3 minutes
09 Zero Current Calibration - Zero
10 Synchonise - SYNC
11 Relay Mode - DFLT
12 Invert Relay - OFF
13 Relay State - OPEN
14 Relay Minimum Closed Time - 0 minutes
15 Relay off time - 0 minutes
16 SoC Relay - 50%
15 Clear SoC Relay - 90%
18 Low Voltage Relay - 0V
19 Clear Voltage Relay - 0V
20 High Voltage Relay - 0V
21 Clear High Voltage Relay -0 - OV
22 Low Starter Voltage Relay
32 Alarm Buzzer - On
Is the charger permanently charging the battery. If so there should be a continuous flow of current into the battery apart from when you draw a large load and the charger can not supply this. What amps is the device showing is flowing and is it positive or negative.
A couple of thoughts, is the shunt connected the right way round, if the wrong way and on continuous charge it would slowly show a decline. It looks correct.
Is the charger negative somehow connected to the battery negative so the charge current is not counted, passing via a chassis ground. Once again, the only negative connection to the battery is the shunt and everything else (all loads, all chargers, chassis ground, starter battery) is connected to the system side of the shunt. It looks correct.
Have you done a proper zero current calibration per the manual.
The settings look OK, the only thing you could change is increase the charged voltage to 0.2V below absorption once you find out the absorption voltage, but this should not cause your problem.
Good morning everyone - have set the correct cable configuration (diagonal cross connection) the unit seems to have reset itself and appears to be behaving now.
Last night before bed it appeared to be showing a (slow) discharge % (declining). This morning I woke-up and checked the unit and it is set to 100% (no dropping %) and showing what appears to be nominal numbers for a house battery pair connected to the charge on shore power. the overall state is 100% - Voltage 13.2V - 1.26 Amps (changing as I write due to varying loads on the battery) - 14 W (changing as I write due to varying loads on the battery) 0.0 Ah.
Does that look correct? If you can let me know what you think so I can start to trust the instrument.
Also I checked the history and here’s what I saw (last sync was yesterday after correcting the incorrect battery cable connections - cross diagonal):
A Deepest Discharge -0.4k Ah
B Last Discharge - 0 Ah
C Average Discharge - 0 Ah
D Number of Cycles - 2
E Discharges - 1
F Cumulative Ahs - 925 Ah
G Lowest Battery Voltage - 0.00 V
H Highest Battery Voltage - 14.7 V
I Days Since last discharge - 0
J Number of automatic syncs (when state of charge drops below 90% before s sync occurs) - 2
L Number of low voltage alarms - 0
N Number of High voltage alarms - 0
Total energy drawn from battery - 12.3 k Wh
S - Total energy absorbed by battery - 450 Wh
I trust that all makes sense and many thanks for your help if this is now working correctly.
Much appreciated pwfarnell - I can start to trust the instrument from here on.
Now I just need Victron Sales to answer a question IO sent days ago about buying and adding a battery temp sensor the BMV 700. They apparent to have conflicting information on their site that the temp sensor they show only works on the BMV 702 and 703? The manual shows that it can be fitted to any of the lower-end BMVs.
