Electrodacus BMS- no contactors?

[CaptainRivet]

Originally Posted by svloki

Thanks Rivet. With this idea- BMV712 as the last resort, would you use the device to trigger based on high voltage to disconnect both busses?


Please see drawing.

High voltage charge bus, low voltage load bus with electrodacus but if you are below 10V or above 14.7V a lot failed and the BMV needs to throw the disconnect hammer now.
The BMV712 as last resort disconnects all means load and charge bus plus inverter/charger like victron multiplus.
Last resort means something is fundamentally wrong and all off till you found the root cause and fixed it and then you can manually switch it back on. A last resort shutdown does never clear itself, never ever.
Curcuit diagramm:
To both busses smart BP 220 remote port goes in series! Onto the extio from electrodacus as well as the BMV712.
So that the BP220 load bus is on the electrodacus closed contact (extio load stays closed till 12.pV in my case, LCV 3.0V) and in series contected als BMV stays closed till 10V contact. Same to charge side.
A smart BP220 cannot disconnect an inverter. The inverter capacitors create so much surge that will fry the mosfets of the Bp220 when starting up

[svloki]

Originally Posted by CaptainRivet

High voltage charge bus, low voltage load bus with electrodacus but if you are below 9.9V or above 14.7V a lot failed and the BMV needs to throw the disconnect hammer now.
The BMV712 as last resort disconnects all means load and charge bus plus inverter/charger like victron multiplus.
Last resort means something is fundamentally wrong and all off till you found the root cause and fixed it and then you can manually switch it back on. A last resort shutdown does never clear itself, never ever.

Thanks, I think I understand. You would recommend connecting the SCR's (or whatever disconnect devices are used) to both trigger from the Electrodacus and the BMV-712? Perhaps use disconnect voltage setpoints like this...

Electrodacus: Low = 10.0v, High = 14.6v
BMV712: Low = 9.9v, High = 14.7v

Again Electrodacus should prevent all this by switching things off long before.

[CaptainRivet]

Originally Posted by svloki

Thanks, I think I understand. You would recommend connecting the SCR's (or whatever disconnect devices are used) to both trigger from the Electrodacus and the BMV-712? Perhaps use disconnect voltage setpoints like this...

Electrodacus: Low = 10.0v, High = 14.6v
BMV712: Low = 9.9v, High = 14.7v

Again Electrodacus should prevent all this by switching things off long before.

Yes both triggers in series so both switch off devices must be on, again double security.
Disconnect voltages I recommend:
Mppt: absorption 13.8V and Float 13.45V
Alternator: cut at 95% SOC or 13.6V
All other charge sources: 14.4V and float 13.45
Electrodacus: undervoltage lock 2.5V low cut off 2.8V=10.32V, end of charge 3.50V =14.2V high cutoff 3.63V=14.52V overvoltage Lock 3.7V or 14.7V
BmV712: low 9.9V and high 14.75V

Yes the MPPT as main charge source are always online and maintain the balance. The rest of the charge sources are steered by the eletrodacus. That's different to what Darcian recommends but like this you get a top balance over time if you screwed that up and keep it.
Below 2.8V is not much capacity left but you stay away from the boarders a bit so devations in measurements don't cause a shutdown. 3.63V so you can do a top balance without shutdown.
Also after shutdown the battery is still in all is in the healthy range, so if you fixed the issue it comes right back online. The locks don't let you connect back online if the battery is that low or high. Only if they don't work the BMV cuts all.
Cells won't be most likely not damaged then but lost some cycle life, cells below 2.5V can be mostly rescued by charging the single cell with 1 till 3A till they are above 2.5V with a little power supply, same overvoltage deplete the single cell till below 3.65V.

[sailingharry]

Originally Posted by svloki

Thanks Rivet. With this idea- BMV712 as the last resort, would you use the device to trigger based on high voltage to disconnect both busses?


Please see drawing.

Some comments:
* Can't comment on the BMV as last resort. But if indeed it can monitor for out-of-spec high and low, and also for imbalance between cells 1&2 and 3&4, then having it open the disconnects would be good.
* You haven't put the 'Dacus to the BP's. That makes the BMV not "last resort" but "primary defense." You also need the 'Dacus in the control circuit for the BP's.
* You have a battery switch before the shunts. If Dacian is correct (I assume he is!), opening that switch fries the 'Dacus. The switch must be AFTER the BP's, and you need two. If you don't care about the ABYC requirement for a physical switch (not an unreasonable decision), you need to satisfy yourself on possible failure modes of the BP -- if they are 100% reliable at opening with the control wire open, then fine, but if they have the ability to fail shut, you have a problem.

* As I commented up thread, there is benefit to using both shunts and getting the magic of that. But it isn't cheap -- you need two shunts, you need two contactors, you need two battery switches (although you could use a 7713 or a XD and get both the 'Dacus control and a real battery switch), and you need the big wires/lugs or bus bars to connect it all.

[CaptainRivet]

Originally Posted by sailingharry

Some comments:
* Can't comment on the BMV as last resort. But if indeed it can monitor for out-of-spec high and low, and also for imbalance between cells 1&2 and 3&4, then having it open the disconnects would be good.
* You haven't put the 'Dacus to the BP's. That makes the BMV not "last resort" but "primary defense." You also need the 'Dacus in the control circuit for the BP's.
* You have a battery switch before the shunts. If Dacian is correct (I assume he is!), opening that switch fries the 'Dacus. The switch must be AFTER the BP's, and you need two. If you don't care about the ABYC requirement for a physical switch (not an unreasonable decision), you need to satisfy yourself on possible failure modes of the BP -- if they are 100% reliable at opening with the control wire open, then fine, but if they have the ability to fail shut, you have a problem.

* As I commented up thread, there is benefit to using both shunts and getting the magic of that. But it isn't cheap -- you need two shunts, you need two contactors, you need two battery switches (although you could use a 7713 or a XD and get both the 'Dacus control and a real battery switch), and you need the big wires/lugs or bus bars to connect it all.

Correct about BPs connecting to BMS, if used with BMV the remote line must be connect in series to BMs and BMV
Yes correct switch must be after fuse.
Use NH fuses which act also as disconnect switch. If your load/charge is below 150A use a for each bus a trip coil breakers which are fuse, BMS disconnector and manual disconnect switch in one. Saves connection and fialure point plus money.

[sailingharry]

Originally Posted by CaptainRivet

Also after shutdown the battery is still in all is in the healthy range, so if you fixed the issue it comes right back online. The locks don't let you connect back online if the battery is that low or high. Only if they don't work the BMV cuts all.
Cells won't be most likely not damaged then but lost some cycle life, cells below 2.5V can be mostly rescued by charging the single cell with 1 till 3A till they are above 2.5V with a little power supply, same overvoltage deplete the single cell till below 3.65V.

This is a benefit I see in using the 7713 or the DK over the BP or a solenoid. The remote battery switch style disconnect has a manual override, both OFF and ON. The OFF is great for a non-negotiable power off when doing service. The ON allows an override of the BMS. If you have a severe low voltage event, you can ensure that the solar (or other source) is providing power, and "force on" the contactor, or you can likewise override it to allow bleeding down an overcharge event. Otherwise, it requires some sort of jumper approach. Of course, this is a once-in-a-lifetime event, so major planning for it is overkill.....

[CaptainRivet]

Originally Posted by sailingharry

This is a benefit I see in using the 7713 or the DK over the BP or a solenoid. The remote battery switch style disconnect has a manual override, both OFF and ON. The OFF is great for a non-negotiable power off when doing service. The ON allows an override of the BMS. If you have a severe low voltage event, you can ensure that the solar (or other source) is providing power, and "force on" the contactor, or you can likewise override it to allow bleeding down an overcharge event. Otherwise, it requires some sort of jumper approach. Of course, this is a once-in-a-lifetime event, so major planning for it is overkill.....

The SMART BP65/100/220 has
A) via BT connect app a manually override, you don't even have to creep down to batterie or locker to switch it off/on physically. That why I use sometimes 2 or even 3 x BP65 instead a BP100 or a 220, you can switch the individual devices off like instead 1 BP 220 disconnects all each 50/100 gets a BP65. Depends how you want it. I prefer switching 3 smaller load then one big, the more current the more switching is an issue...generally above 100A.
B) its own overvoltage protection (its a battery protect thats switchable via remote). It's fixed at 16.0V or 29V(24V system) a bit high but better then nothing compared to all other, so actually a 3rd desaster cutoff independent form BMS and BMV. That also works well just for eg a defect MPPT goes haywire and sends panel voltage, the BP switched the MPPTs off and avoided a blackout shutdown in my buddy boats dacus installation. Voltage rises quickly when MPPT does that and BP is faster then BMS which has a 3sec delay so that charge peaks don't cause a cutoff/blackout. Same in my installation DVCC was not properly working (shut it off and use BT sync and see no difference at all) and suddenly out of the blue all 4 MPPTs raised output voltage, the BP220 overvoltage protection cut them off before they would have cause a full blackout.
C) a voltage meter means you see the voltages at the contact in the BT connect app, tremendously helpfull for troubleshooting.
D) no mechanical parts so cannot wear out like relays or trip coil breaker(much less then relay)
One important remark: you hear and read BPs fail and are unreliable, that not correct if you spec and use it properly. it's a mosfet device and there is no peak rating at all means you need size it so total current incl surge and peak is below the rating. I stay away from the edges and leave at least 10%, mostly 20% room, means BP220 I run and spec to 180A, exception with hard limit device max 200A eg 4x MPPT 50/100 as the MPPt limits output so you cannot run outside specs.
Like this I never had a BP fail on me till today.

In detail.:
Only thing a BP cannot do is surge, in BP manual stands no.big inverters, no mator loads. yes if the surge is below the rating of BP it's ok eg my 12V watermaker runs at 30-45A and surge is max 150A+30A for other loads so a BP220 fits. that's why as load disconnect I use a relay for the inverter (which in 95% surge is higher then BP rating) IF necessary and a BP for the rest of the loads.

Victron,Studer,Mastervolt,Schneider inverters the internal shutoff via BMS function is vastly superior to any relay cutting hot side so I rely in the million user tested cutoff function instead introducing as weakest link a cutoff relay. In case the inverters DC side mosfet or transformator shorts out the internal device fuses cut it off, so nothing can happen here.
My cheap boost inverter EDECOA has a disconnect relay as thats good chinese budget quality but it's internal electrical design+fuses is not tested and grid certified, my Multiplus has no disconnect contactor at all as the disconnect features are super relaible.

[s/v Jedi]

Sellers stating their Eve cells are grade A and matched…

Most of the time they are used, refurbished with fantasy QR codes and of course they ain’t matched in the technical sense of the word… probably matched for the same color wrap or specially for your order or other BS.

Real matched cells come from the same production run, with sequential serial numbers and a test report confirming the same internal resistance graph over SOC curve.

You get that with Winston. All my Winston cells have sequential serial numbers and stay balanced by themselves.

About taking battery banks offline: no, I don’t do that every time I go ashore. I do it when I stay away from the boat for a couple of nights or more… whenever we prep the boat for us being away for a bit. We learned to do that the hard way, after multiple times returning to the boat finding damage from lightning strikes either directly or in neighboring boats.

Here is my new small battery to do this. At less than $300 better than insurance for the big batteries

[donradcliffe]

I've given up trying to follow this, and skipped to the end. I firmly believe in KISS, and none of these system are simple. I do have one question.

Do any or all of these low voltage cutoff systems protect against simple neglect? It is a very real probability, when someone walks away from the boat for a year or more. Is the battery completely isolated, or are there parasitic drains which will eventually destroy it? I have seen it happen with a professionally installed Mastervolt system.

[s/v Jedi]

Originally Posted by donradcliffe

I've given up trying to follow this, and skipped to the end. I firmly believe in KISS, and none of these system are simple. I do have one question.

Do any or all of these low voltage cutoff systems protect against simple neglect? It is a very real probability, when someone walks away from the boat for a year or more. Is the battery completely isolated, or are there parasitic drains which will eventually destroy it? I have seen it happen with a professionally installed Mastervolt system.

Indeed, people forget the BMS and even a BMV consumes energy from the battery.

So no, they don’t protect against that. A BMV uses very little energy but some BMS’s do and they should be disconnected if possible.

[sailingharry]

Originally Posted by s/v Jedi

Indeed, people forget the BMS and even a BMV consumes energy from the battery.

So no, they don’t protect against that. A BMV uses very little energy but some BMS’s do and they should be disconnected if possible.

I have a suspicion, based on turning on cell phones that have been in a drawer for years and still at 50%, that you can manage this. You need to remove 100% of all loads and sources, which basically means an air gap. If the battery is open-terminaled, and sitting at 75% when you disconnect, you should be good for several years -- and that is massively better than an AGM, which is probably toast by then (interweb indicates AGM self-discharge at 1-10% per month based on condition, so assume 25% per year leads to a flat battery at year 4 and unknown sulfation issues by year 2 -- flooded are even worse).



Of course, this solution comes with it's own downside. I have a friend who had a vandal break into their boat, leave the hatch open, and rain first drained the battery and then did so much water damage that the boat was totaled. There is a Saga 43 that had a similar fate -- water down the mast (and perhaps other minor sources) drove humidity so high that the entire interior of the boat is a rotted shadow of its former self. Literally beyond repair -- it will take removal of basically all wood to begin a rebuild. So if you intend the boat to have zero power for years, you'll need a solution to interior water. A garboard drain is an excellent solution.

[CaptainRivet]

Originally Posted by s/v Jedi

Sellers stating their Eve cells are grade A and matched…

Most of the time they are used, refurbished with fantasy QR codes and of course they ain’t matched in the technical sense of the word… probably matched for the same color wrap or specially for your order or other BS.

Real matched cells come from the same production run, with sequential serial numbers and a test report confirming the same internal resistance graph over SOC curve.

You get that with Winston. All my Winston cells have sequential serial numbers and stay balanced by themselves.

About taking battery banks offline: no, I don’t do that every time I go ashore. I do it when I stay away from the boat for a couple of nights or more… whenever we prep the boat for us being away for a bit. We learned to do that the hard way, after multiple times returning to the boat finding damage from lightning strikes either directly or in neighboring boats.

Here is my new small battery to do this. At less than $300 better than insurance for the big batteries

Your statement about EVE was true 3 to 4 years ago. With EV crises stocks are full and you mostly get real grade A.
For.europe eg www.nkon.com when they state it's grade A then you get all docs as well like with winston, only difference resistance is not measured over whole curve because EV doesn't do that.
2nd offgrid garages Frankenstein battery proofs you can nail together the biggest junk cell and still get a relaible working battery, just need a BMS with a good active balancer which you get from JK starting at 60Euro for the 100A 4S version.
Winston are top notch, no question but the EVE or Calb got so good that they are for 95% of users fully sufficent.
There are some exceptional cases where a winston is still the top choice but these got much smaller.

Don't get why you buy a 24V 50AH litime with a basic BMS when you can make out of 8x50 or even 100AH EVE, CALB, lishen cells and JK inverter BMS a battery that costs half, delivers 1/3 more and has a top notch mosfet BMS. You preach one thing but do the opposite. For the prices LI-TIME sell their batteries these must also be rejected/grade B cells, so no better then what you can buy anywhere.

Yes your 24V litime was a test, take an EEL 24V KIT with JK BMS, order 8x EVE at nkon.com and you will see ypu get for 40% less money a better battery with a much better BMS then your Li-time.
And if it's an shore and emergency battery take 18$ LTO SCIB cells from.batteryhookup.com and for a1/3rd of the money you have 500% times more robust battery that doesn't need a BMS at all, a 15$ active balancer is enough, that can be even discharged to 0V and charged again so if no shorepower and no sun over long periode, as soon as it's fixed you battery will charge and work again, forget that with any lead or other lithium chemistry.

[CaptainRivet]

Originally Posted by s/v Jedi

Indeed, people forget the BMS and even a BMV consumes energy from the battery.

So no, they don’t protect against that. A BMV uses very little energy but some BMS’s do and they should be disconnected if possible.

Yes true people forget that.

That's why take an LTO with an active balancer, no BMS or BMV needed, just an active balancer which doesn't consume energy. That why I have them as backup and starter. They can take the full charge of my install. As all charge sources configured for lifepo4 the LTO gets max 85%SOC even if charge sources doesn't shut off or stay in bulk.
so the only that could harm it is an MPPT going haywire and put full panel volatge through...the BP220 is preventing that and switch them off without a BMS or BMV being present as LFP is offline

When I leave the boat for longer I flip the switch so all goes to LTO, unplug the BMS and pull the main battery fuse of the LFP bank which is discharged before to 75% SOC.

[s/v Jedi]

Originally Posted by sailingharry

I have a suspicion, based on turning on cell phones that have been in a drawer for years and still at 50%, that you can manage this. You need to remove 100% of all loads and sources, which basically means an air gap. If the battery is open-terminaled, and sitting at 75% when you disconnect, you should be good for several years -- and that is massively better than an AGM, which is probably toast by then (interweb indicates AGM self-discharge at 1-10% per month based on condition, so assume 25% per year leads to a flat battery at year 4 and unknown sulfation issues by year 2 -- flooded are even worse).

Of course, this solution comes with it's own downside. I have a friend who had a vandal break into their boat, leave the hatch open, and rain first drained the battery and then did so much water damage that the boat was totaled. There is a Saga 43 that had a similar fate -- water down the mast (and perhaps other minor sources) drove humidity so high that the entire interior of the boat is a rotted shadow of its former self. Literally beyond repair -- it will take removal of basically all wood to begin a rebuild. So if you intend the boat to have zero power for years, you'll need a solution to interior water. A garboard drain is an excellent solution.

We have had reports on the forum from members with destroyed batteries showing this isn’t true. When you take cables off the terminals you still have the internal BMS connected and draining the cells.

[sailingharry]

Originally Posted by s/v Jedi

We have had reports on the forum from members with destroyed batteries showing this isn’t true. When you take cables off the terminals you still have the internal BMS connected and draining the cells.

Hmm... another down-check for drop-in batteries. I wonder if high end (Victron, for instance) have a work around?


I've pondered on a DIY build if the LVC should also isolate the BMS. My choice of BMS (the Electrodacus) won't tolerate that, but I think others would. The thought is that when the LVC trips, you are very low and it's not much more to damage. A side benefit is that if the BMS is unpowered, it requires manual intervention to light the system back up (and if the LVC trips, you have problems that need a human to evaluate).