Three Way Charging / Mixing Old and New Tech

[RAW]

OK so I have demonstrated now that the Old Charger on Sylvia is capable of charging all the batteries, albeit slowly

For some reason the BMV battery monitor does not see the battery as charging with this set-up
The delivery from the Old LabCraft Charger coming to the New Alpha AGM 160AH battery is IRO 1.03 Amps
Significantly when I left the Van at the Garage for over three weeks with only Solar available and the inverter turned on, although with no 240V load, I noticed that the Voltage on the front old leisure battery had dropped to around 9.5V and the Alpha AGM was at around 10V and 48% charge capacity
That was how things were before I plugged Sylvia into 240V Household Supply

What I am wondering is if this fairly slow trickle charge to the AGM is going to do the Alpha Battery any harm and whether I should maybe look at an isolated 240V charge Method for the AGM
As Black Friday Sales are ongoing I have found this on Amazon which seems quite good value
CTEK

Also in the Three way department the Solar will charge the AGM fine and also the other batteries, although in the very dark days of Winter in the valley which are now upon us the Solar is doing almost naff all. The Alternator outputs a couple of AMPs in charge when the engine is on and this also can charge all batteries.

Any advice / input appreciated as always

 

[wildebus]

ref this comment "For some reason the BMV battery monitor does not see the battery as charging with this set-up "
as long as all loads/chargers are on the LOAD side of the BMV shunt and the -ve battery connection on the 160Ah battery is on the BATTERY side of the shunt is only connection, then the BMV will see all current into and out of the that battery. It doesn't matter if it is big or small, it will be recorded.

 

[RAW]

s long as all loads/chargers are on the LOAD side of the BMV shunt and the -ve battery connection on the 160Ah battery is on the BATTERY side of the shunt is only connection, then the BMV will see all current into and out of the that battery

Here's a shoddy (NOT BIG CLIVE) drawing of how I think the wiring is (at work at the minute), which would explain why the BMV isn't recording the Charge from the 240V Labcraft charger.

I can't remember how the BMV is but pretty sure only the 160AH Alpha is on the battery side and everything else is on the other side but will check later tonight. Thanks @wildebus

 

[SquirrellCook]

I don't expect it's only me, but it hard to get your head around the idea of a load being on the negative side of the battery. I just keep reminding myself that everything must go through the shunt to be recorded.

 

[RAW]

On a slightly different subject, I discovered today that the Venus OS fails over to different wireless networks seamlessly if it loses the connection, so that's good news.
On the other hand I am disappointed that no-one in the Victron community answered my Question here

 

[wildebus]

Here's a shoddy (NOT BIG CLIVE) drawing of how I think the wiring is (at work at the minute), which would explain why the BMV isn't recording the Charge from the 240V Labcraft charger.
View attachment 1858

I can't remember how the BMV is but pretty sure only the 160AH Alpha is on the battery side and everything else is on the other side but will check later tonight. Thanks @wildebus

Ref your diagram ...
Thinking on how you have said the batteries are located, are you sure about the -ve connection on the old battery?
Excluding the Charger (which you have identified as needing moving), is the only connection to -ve on the old battery the one going to the shunt? There are no 'historical' connections still there?

If there were you would need to connect those to chassis ground so they are on the correct side of the shunt as far as current detection goes.
If you are connecting both (old and new) leisure batteries to the BAT side of the Shunt, then you must remember (you may well have done this, but commenting just in case and for others doing something similar) when setting up the Battery Monitor to set the capacity at the C20 rating of the TOTAL Ah of BOTH Batteries, not just the new one. If you were to only set it at the new one, your SOC reading would be pessimistic and it would tell you the battery BANK state of charge was lower than it really was as it is calculating for a single battery not a pair. (the Current readings are still correct, it is just the SOC maths that goes out of kilter).
Alternatively - and this may be a better option as I think you said you often disconnect the old battery (IIRC?), move the -ve cable from the old battery from the BAT side of the shunt to the LOAD side of the shunt and set the BMV Ah to just the new batteries C20 capacity. This will (if you do disconnect the old battery often) give a better picture for you as the BMV won't suddenly have 50Ah or whatever it is of apparent capacity coming and going and confusing the SOC indication.
This would treat the old battery as a "reverse load" (i.e. a load that is providing power). There is nothing wrong with this and it is no different to the starter battery that will appear just like that whenever the VSR is energised.

end of the day, the BMV is just a monitor and doesn't actually affect how the batteries work, but if the SOC maths is getting confused, you won't be able to rely on the info to see what is going on.

 

[wildebus]

On a slightly different subject, I discovered today that the Venus OS fails over to different wireless networks seamlessly if it loses the connection, so that's good news.
On the other hand I am disappointed that no-one in the Victron community answered my Question here

Didn't see that question on the community forum. The answer as far as I am aware is basically no.
With the VE Smart Networking, various information is shared depending on the device that has info (so voltage and temp for the SBS is sent, voltage for the BMV is sent), but because your MPPT has no bluetooth capability without the dongle and the VE.Direct port cannot be shared, it cannot participate in the VE.Smart Network if that port is used for a Venus OS connection and so cannot pick up the voltage or temp info.
(it gets better voltage info another way by turning off every 10 minutes momentarily, but the temp info is out of reach without the SBS)
There is no cross-communication between the hardwired Venus OS world and the wireless Bluetooth Victron Connect world and I am not aware they have any plans whatsoever to do so.
Also right now even for VE.Direct devices connected to a Venus OS system, it is very much a one-way road with the device getting polled for info but nothing* gets sent to the VE.Direct device so it cannot be provided with info or any parameters or settings changed.

*with the notable exception of firmware updates interestingly (which can leave you with the situation of being able to remotely update a device and introduce new features and settings, but not being able to do anything with them unless you are phyisically by the device)

 

[RAW]

As far as I am aware the negative on the Old Leisure battery is connected to the chassis plus has some other cables running from it
I have connected the negative load of shunt to the Old Leisure battery negative
I have connected Positive From new Leisure Battery to Positive on old leisure battery with an on/off switch in between

So I would need to do some serious rewiring I think to make the whole system and BMV monitor work as it should from what you have said above @wildebus, not sure I CBA TBH !!

When the switch is open on positive then the BMV is giving false information maybe on the SOC of the Alpha

 

[wildebus]

As far as I am aware the negative on the Old Leisure battery is connected to the chassis plus has some other cables running from it
I have connected the negative load of shunt to the Old Leisure battery negative
I have connected Positive From new Leisure Battery to Positive on old leisure battery with an on/off switch in between

So I would need to do some serious rewiring I think to make the whole system and BMV monitor work as it should from what you have said above @wildebus, not sure I CBA TBH !!

When the switch is open on positive then the BMV is giving false information maybe on the SOC of the Alpha

if you have the negative on the old battery going to chassis AND going to the battery side of the Shunt, then the BMV is not going to be reading current loads remotely accurately.
As a "quick fix" move the old battery cable from the BAT side to the LOAD side and then at least the currents being read will have some meaning.

 

[RAW]

I am fairly sure the Only cable to battery on Shunt is from -ve on New Battery, will double check later though, thanks

 

[wildebus]

I am fairly sure the Only cable to battery on Shunt is from -ve on New Battery, will double check later though, thanks

ok (your diagram does say otherwise though, hence my suggestion)

 

[RAW]

ok (your diagram does say otherwise though, hence my suggestion)

That's coz I haven't marked the shunt up properly, will check it and post an annotated image when back home

 

[RAW]

Here's the Shunt

It's all a bit of a mess at the moment as not sure where I am placing components etc for final fix
The only cable on the 50MV part is -ve from the Leoch Alpha Battery (new)

ALSO and REALLY ANNOYINGLY I was looking at the BMV settings on the phone app and the Victron Phone App requested that I update the device to latest firmware. Then as soon as the update was complete the BMV read the battery state of charge at 100% when the battery was really only 60 odd %
Below is the VRM setting before I updated the Firmware

Now when I look at the VRM I get

So that's clearly WRONG I would think

This is because of this setting which defaults to on after a FW update (I subsequently turned it off)

I would have thought though that the BMV-712 is a METER, so will it eventually (when?) read the battery SOC at what it actually is rather than a theoretical 100% ?

The whole purpose of what I was trying to do was to isolate the 240V charger, and then see what the BMV read as the SOC of the NEW battery with almost no load and no charge current to it.
The old charger, which BTW I am not thinking of moving, so much as either replacing or possibly just having it dedicated to the one battery (older battery) at the front of Sylvia.
Then maybe having a second charger dedicated to the newer 160AH leisure battery that I could simply plug into one of Sylvia's internal 240V sockets when the van is on EHU

Then just having the switched supply as on when running only on 12V wild camping or when running the vehicle and using the Alternator to charge all three batteries.

At the moment though I am somewhat annoyed at the SOC measurement going to pot due to a Firmware update. That just doesn't seem right at all as with VE SMART networking enabled now the MPPT 100/30 will be receiving information from the BMV on a SOC of 100% when that isn't the case at all !!

 

[wildebus]

That setting on the BMV can be quite frustrating as the default is the reset - it would also reset if the power was momentarily removed as well.
Remember the BMV is a monitor only. it won't affect the charge going into a battery so as soon as the batteries are full (chargers gone to float mode typically) then it will be at the real 100%, nor will the MPPT Controller get any info from the BMV (it is a one-way street, remember).
The SOC is based on the Ah out (which is a calculation of the Current read x the voltage at that time) as a percentage of the Battery Capacity - so if you draw out 16Ah, it will say the SOC is 90% (it won't "correct" itself to the 'real' SOC until you do full charge. You could lower the Ah setting right down to say 40Ah, pull some current and it will drop the SOC rapidly and then you could change it back again. Not tried that and TBH I think it is a bit pointless and would just focus on getting the batteries full again, but it's an option).

Cabling looks right. You ideally would lower the Ah setting to whatever the 160Ah battery is at C20 rating (145Ah or so I would guess?).

 

[RAW]

That setting on the BMV can be quite frustrating as the default is the reset - it would also reset if the power was momentarily removed as well.
Remember the BMV is a monitor only.

Well that's more than a little frustrating. To me this means that everything is theoretical from the BMV and it has no REAL way of measuring SOC or anything else, as you have mentioned before, it is all decided based on the Maths.
So then it seems pointless in many ways because surely you would want to know what the SOC of your battery ACTUALLY is rather than THEORETICALLY might be.
To that end I decided this morning to look at the bar monitor on the Edecoa and I see this


So that confirms that the SOC of the battery is actually likely around 60% to 70% and not 100%, what the BMV was reading before it did the reset on Firmware. Note to self, refuse any firmware updates unless the battery is at 100%

To my mind that means you will never be able to determine accurately the SOC of your battery with Victron equipment unless you know 100% that your battery was 100% Full when you started to monitor it.

My next thought on this cloudy day is what is happening with the Victron Charge Controller and I see there it is in a bulk charge state.
Why then, when everything is connected in a Victron SMART network is the MPPT unable to tell the BMV that the battery is not 100% charged ?
I guess this is because of the "one way street" in communication that you mention

Thinking through this then. How can I determine what the SOC of the Battery actually is without another way of measuring it?
This then means that in order to have a battery in a good condition if there exists non-standard installations like mine, you would need a decent intelligent charger thrown into the Mix as well. More money to Victron.....
Instead of buying some more Victron kit I decided to get a cheap Chinese charger that's currently on Sale at Amazon and should keep the LEOCH in good condition in the Winter months when the solar is poor
This one

At this point I am left wondering: what is the point is of having the BMV in my situation??

Moving on.
I left the Old Labcraft charger simply charging the single 70AH Leisure battery in the front of the vehicle overnight and the voltage went from around 12.5V to 13.5V indicating that it is probably now fully charged.

I thought then what does the charger deliver to the LEOCH now the Front battery is fully charged

Almost 3 AMPS, which is OK. Means that if the LEOCH gets down to 50% or so then it would take just over a day to charge and is a lot better than the one AMP i was getting when I first plugged Sylvia in.

Then on the last point

lower the Ah setting to whatever the 160Ah battery is at C20 rating (145Ah or so I would guess?).

This had not dawned on me before, or had got past me, so I changed the settings in the BMV to reflect that and your guess is 100% Correct according to the Datasheet here


Thanks for the help again David (@wildebus)

 

[SquirrellCook]

Unless I've got the wrong end of the stick, surely the BMV has to learn?
You have to tell it the parameters it's working with.
Then when you've been through some full charge and partial discharge cycles it will learn and give useful information.
Also I'm not sure which battery you are trying to monitor within your array.

 

[RAW]

Unless I've got the wrong end of the stick, surely the BMV has to learn?
You have to tell it the parameters it's working with.
Then when you've been through some full charge and partial discharge cycles it will learn and give useful information.

Maybe, unless you somehow reset the device either through Firmware update or removing the power then everything learnt will be forgotten and you start from scratch. Seems more than a bit backwards to me.

 

[SquirrellCook]

Maybe, unless you somehow reset the device either through Firmware update or removing the power then everything learnt will be forgotten and you start from scratch. Seems more than a bit backwards to me.

I'm must admit it caught me with my pants down when I installed my last BMV. I wasn't prepared for the updates, it seemed like I had no or little warning about the effects of what it was doing. I was right on the limits of my wifi too.

 

[SquirrellCook]

Also I'm not sure how you would clear all collected data, say after doing an upgrade. Under those conditions it would be nice to start fresh.
I have some rubbish info on my first BMV from when I was trying to figure it out.

 

[RAW]

Also I'm not sure how you would clear all collected data, say after doing an upgrade. Under those conditions it would be nice to start fresh.
I have some rubbish info on my first BMV from when I was trying to figure it out.

Do you mean the data that exists on the Bluetooth application or on the VRM Portal or both ?
Anywho, on BT app there is a setting reset to default which I think clears all the data, however make sure you BACKUP YOUR SETTINGS first before resetting.
Then on the Portal, I don't know, can't seem to find it.
Interestingly now on the Portal the Battery is seen to be charging but why ?
How does the BMV detect charge current ?