Electrodacus BMS- no contactors?

[sailingharry]

There is a discussion going on at the Electrodacus forum regarding contactors, that is relevant here. Someone came across this vendor:
https://www.egismobile.com/en_GB/sho...ulk-pack-5967?


The specs are remarkably unhelpful. But, it is rated 500A as a battery switch. It uses 3/8 stainless terminal bolts. It has tinned wire. It has a manual override for both ON and OFF. It is about 2/3 the size of the Blue Seas option, and about 2/3 the price. The bolts face out, not down, which works well for my plans. Purchase seems to be only via direct from the manufacturer (in WA). They do seem to have a fairly robust array of products (but all with the same limited information). S&H is reasonable (around $20, IIRC).


I've never heard of them, and can't find them available from any vendor (but Fisheries does sell their 150A solenoid, so they may be a "real company"). The pictures and glossy brochures make it sound at least plausible, if not credible.


Anybody have any thoughts?


EDIT -- it is real, and seems liked. Peter Kennedy (PKYS) sells them, and has even answered a question about them (so he is at least minimally aware of the product). I don't think Peter would sell phony products. https://shop.pkys.com/egis-egis8710-1500b Peter also includes much more detail, including a line that says "Typ Source Current for All Ctrl Lines 10 micro-Amps" implying that the 5A operating current comes from the battery, not the control switch.

[svloki]

Originally Posted by sailingharry

Philosophically, you are of course correct. Practically, it's not a big deal. I'm not even sure that you would find a prohibition in a critical, word-by-word reading of ABYC.


Here's the thing. In a standard install, there is a short battery cable. It goes 6" to a fuse holder input, then to the fuse, then to the fuse holder output, then "onward" (battery switch, etc). The risk exposure is the battery terminal and the entire fuse and holder assembly.


In the plan as envisioned in my head (and parts are coming together), the install is a short battery cable to the shunt. The shunt "out" bolt matches my Class-T fuse. The other end of the Class-T will sit on the contactor. So, the exposure is the battery terminal, the shunt (about 2" square of exposed metal), and the inlet side of the Class-T. A simple perforated plastic shield could be mounted over the shut/fuse assembly.


Reading the above two paragraphs, the increased risk by installing as required by the 'Dacus is the shunt -- and it is immediately in contact with the fuse, so it is basically the same risk as the fuse/fuse holder, just perhaps a few additional square inches of exposure. It is an increased risk, but the delta is small.


I have attached a pic of the shunt I'll be using with 2 Class-T fuses for reference. The shunt itself is the only additional risk over a standard install. The battery cable will land on the bottom right bolt.

Yes, as I mentioned earlier, the risk can be mitigated, and it seems you have a plan to accomplish. All good. What heat load have you estimated at the shunts? I am looking at distances and materials for my setup.

[svloki]

My 75mv shunt at 150a load should only need to dissipate 3.4 watts of heat, if my numbers are correct. I used .15 milliohms resistance.

[sailingharry]

Originally Posted by svloki

If I remember correctly, the old Heart devices used an off the shelf 50mv shunt. Can just cut a copper bar to jump two ends of those. Easy?

Yes, I'm a big fan of bus bars. It's not super easy, but doable.


First is sizing. Wires are sized to not melt the insulation. This is a very constraining criteria, as insulation melts at low temps (boiling water, +/-). Copper itself can take many times that current. Bus bars are sized on desired upper temperature, and there are tables (https://www.copper.org/applications/...us_table1.html) that give limits for sizes and temperature rise. 400A (my fuses) is a beefy bar!


Second is plating. Getting one with factory applied plating (tin is common) greatly reduces the availability. Lead-free solder (for plumbing, at Home Depot) is something like 90% tin. I've had success coating the entire bar with solder, then wiping off all excess. It has held up well.


Third is drilling. Copper is nice and soft, should be easy. It ain't! It grabs horribly.


Finally, availability. When you scratch off plating, it gets a lot easier. I've had success with eBay and Amazon.


But your question. Yes, the Link is just two singles built as one. A bus bar is a simple answer to join two, and much cheaper/easier/smaller and arguably more reliable than a wire. At the $40 I paid for a neatly packaged unit, it reduced complexity, risk, size, and maybe even cost.

[sailingharry]

Originally Posted by svloki

I re-drew things based on that. Still not 100% convinced that a single contactor is not viable. Is the only concern the possible introduction of a slight error in current flow measurement? Maybe I can live with it.

The PRIMARY concern is death to the BMS if the contactor opens. I too would like a single contactor, but have mostly settled on a single contactor by not using the charge shunt (although I'm building to allow that upgrade in the future).


Your drawing shows the BMV with wires to the BPs. Why? The BMS is fully capable of managing the battery.


I even question the BMV. On my boat, I have a legacy battery monitor installed, and will keep it. It is installed at a location that is super easy to monitor as I walk by, and the BMS will be installed in a much less convenient location (aft cabin, floor level). If installing new, the BMV is a very poor return on investment since it provide no value not already provided by the BMS.


Finally, ABYC (if you choose to follow it) requires a battery switch, and I really doubt that a FET based battery control meets that requirement. I really like the idea of an "air-gap" when I isolate my batteries -- not a hope that the silicon is probably working.

[Baronkrak]

Originally Posted by sailingharry

Second is plating.

CastoTin 1 Tin bearing, bus bars, etc. Complete soldering paste, containing alloy and flux. It offers maximum savings by suspending the flux in a colloidal

It also increase the current carrying capacity of the busbar.

[svloki]

I see a lot of people on the DIYsolar forum nickle plating copper busbars. Seems an excellent solution for the long term, although tin is also very good. I made all my own busbars 25 years ago from copper bar stock, it's very easy once you get used to working with copper. Drill press + vise and no worries with "grabbing" Advantage is you get busbars exactly the right configuration and holes.

[svloki]

Originally Posted by sailingharry

Your drawing shows the BMV with wires to the BPs. Why? The BMS is fully capable of managing the battery.

I think of this as a backup to the electrodacus, as that device is designed to keep the system online for as long as possible by switching off sources, I want it to do so. If it fails I chose to have a final protection. Make sense?

[sailingharry]

Originally Posted by svloki

I think of this as a backup to the electrodacus, as that device is designed to keep the system online for as long as possible by switching off sources, I want it to do so. If it fails I chose to have a final protection. Make sense?

Since the 'Dacus also has that functionality (Type 5) with much more detail (it can respond to any single low or high cell), you will have to (or at least should) allow the contactors to be opened by both the 'Dacus and the BMV. This can be done by running the control line serialy. Since you'll also need a manual control, I would see the control wire going BATT+-DACUS-BMV-SWITCH-CONTACTOR.

What cutout settings are you intending to use for the BMV? The 'Dacus disconnects on a low voltage of 2.5V (default, adjustable).

As a curious side note the XD remote battery switch also can be programmed as a LVC -- which allows it to be an additional backup for low voltage (although the lowest setpoint is 11.4 and probably too high).

Note, I'm misusing the word "contactor" to mean any "battery disconnect device" -- the BMV is included, as well as the 7713 or the XD devices, or even the Tyco solenoid.

[s/v Jedi]

A BMV controlling a contactor? I recommend that for only a couple of cases:

- high quality Winston cells without BMS.

- batteries like LiTime that have a BMS without external connections.

For case 1 you simply have cells that always behave well and only a string of cells in series, not parallel. Winston sells such setups as complete batteries too.

What you need is access to the string midpoint. With separate cells this is easy, but with LiTime batteries you need them connected in series (2x 12V in series for 24V etc.). Once you have that, you can connect the BMV to it and configure midpoint monitoring. It them monitors balance and you can set alarms at the mV level and use that to trigger the relay.

Of course this also requires high quality chargers etc. I have seen forum members who just throw a power source at their battery and rely on the BMS doing a HVC to stop charging. Very un-sailor like

I have no experience with the Electrodacus nor REC BMS. I find them very expensive for what they do as the whole detection part is done by a $15 cell monitor and you could wire/adapt its alarm beeper to a contactor to make a functional BMS.

[sailingharry]

Originally Posted by s/v Jedi

I have no experience with the Electrodacus nor REC BMS. I find them very expensive for what they do as the whole detection part is done by a $15 cell monitor and you could wire/adapt its alarm beeper to a contactor to make a functional BMS.

I'm not sure I can agree on the price part of this. The 'Dacus is the least expensive BMS I've found that has external interaction (alarms, contactors, etc). For under $200 USD delivered (including the optional WiFi/USB module), you get a device that gives SOC, has the ability to disconnect loads based on SOC (I intend to shut off inverter at 20% SOC), abiilty to disconnect loads based on CELL voltages (chargers, for instance, normally monitor BANK voltages), all on a nice display with WiFi as backup. While careful (and prudent) setup will have all chargers and loads monitoring voltages (my inverter and fridge, for instance, will turn off at Low Volts, and chargers should be set to stop before High Volt cutoffs), integrating cell level monitoring and protection with a single system is a tremendous value at $200USD. One could argue that even if you are on lead, the 'Dacus is a better value as a simple battery monitor than the BMV.


Don't get me wrong -- this is NOT a $200 install. You'll need contactors, fuse blocks, big wires, little signal relays, buzzers, terminal strips, etc, etc, etc. All done it will be... if you have to ask, buy a kayak.

[CaptainRivet]

Originally Posted by sailingharry

Yes, I'm a big fan of bus bars. It's not super easy, but doable.


First is sizing. Wires are sized to not melt the insulation. This is a very constraining criteria, as insulation melts at low temps (boiling water, +/-). Copper itself can take many times that current. Bus bars are sized on desired upper temperature, and there are tables (https://www.copper.org/applications/...us_table1.html) that give limits for sizes and temperature rise. 400A (my fuses) is a beefy bar!


Second is plating. Getting one with factory applied plating (tin is common) greatly reduces the availability. Lead-free solder (for plumbing, at Home Depot) is something like 90% tin. I've had success coating the entire bar with solder, then wiping off all excess. It has held up well.


Third is drilling. Copper is nice and soft, should be easy. It ain't! It grabs horribly.


Finally, availability. When you scratch off plating, it gets a lot easier. I've had success with eBay and Amazon.


But your question. Yes, the Link is just two singles built as one. A bus bar is a simple answer to join two, and much cheaper/easier/smaller and arguably more reliable than a wire. At the $40 I paid for a neatly packaged unit, it reduced complexity, risk, size, and maybe even cost.

Save yourself all that work. Buy used (or new but ther is no value in new) NH disconnect knifes.
Depending on NH class they are 5x10 (nh0), 5x12 (nh1), 6x15(nh2), 8x35(nh3) or 9x45mm(nh4) in 99% Cooper silver plated. If the silver is black that's just optical and doesn't affect contact resistance. Use silver cutlery polish and they are like new in 5min.
Then drill holes and cut threads as you need.
Cheap top notch material, cannot buy anywhere better and not even standard tin plated copper bars for the money these cost used.
I pulled for test purposes 500A over the 6x15 NH2
bar which is rated for 250A (also due to busbar calcualtor) and it got 10 degrees above ambient as max after 20min. So even a 500A @13v rating they would pass.
Same I tried with 500A the 5x15 tin plated cooper busbar from bussmann, reach after 3 min 20 degrees above ambient and 4 min 35 above ambient and stopped test.

[CaptainRivet]

Originally Posted by sailingharry

I'm not sure I can agree on the price part of this. The 'Dacus is the least expensive BMS I've found that has external interaction (alarms, contactors, etc). For under $200 USD delivered (including the optional WiFi/USB module), you get a device that gives SOC, has the ability to disconnect loads based on SOC (I intend to shut off inverter at 20% SOC), abiilty to disconnect loads based on CELL voltages (chargers, for instance, normally monitor BANK voltages), all on a nice display with WiFi as backup. While careful (and prudent) setup will have all chargers and loads monitoring voltages (my inverter and fridge, for instance, will turn off at Low Volts, and chargers should be set to stop before High Volt cutoffs), integrating cell level monitoring and protection with a single system is a tremendous value at $200USD. One could argue that even if you are on lead, the 'Dacus is a better value as a simple battery monitor than the BMV.


Don't get me wrong -- this is NOT a $200 install. You'll need contactors, fuse blocks, big wires, little signal relays, buzzers, terminal strips, etc, etc, etc. All done it will be... if you have to ask, buy a kayak.

1000% agree. Finally someone here realize what extrem high value this BMS delivers.
As it actually uses in 90% the internal remote of devices the invest in contactors/relays is minimal.
You use rj45 cables where you cut connector of as twisted pair remote cables which also act as fuse, each contains 4 pairs so you can switch with one rj45 cable 4 devices, some resistors and optocopplers boards to multiply the 6 output steering ports called EXTIO and that's basically it. As cut off relay on the hot side where its not possible to cut low side of device a smart battery protect, normally only 1 for the legacy main positive cable to switchboard is needed and if you have MPPTs 1 additional (Darcian don't recommend this but i do because MPPTs can when defect route full panel voltage through and cannot be cut by remote in this case) that cuts them on the hot side in desaster.
That's it on the BMS side, without battery protects about 100Euro extra for the average 300A max system where the main part are the 2 shunts.
Then comes thick cables/fuses etc that you have in all installations.

The ElectrodacusBMS is more value and the same high quality then a BMV712 and who doesn't need the ve-direct to report into victron Venus OS is better off with an ElectrodacusBMS doesn't matter which generation.
It's completely programmable for max. 8 cells and max 32V battery voltages so it can be used for any type of battery from lifepo4 over LTO till sodium.

[sailingharry]

You are a frequent advocate for NH fuses, and they look pretty slick. Unfortunately, they are virtually non-existent in the US.


As an aside, AIC ratings appear to be important (I'm still not completely convinced that 12V provides enough EMF to maintain an arc on a blown fuse). But, DC ratings are impossible to obtain. The Blue Seas Class-T has a nice DC rating, but that exact same fuse in the commerical/industrial arena only has an AC rating -- where did Blue Seas get that? I'm not saying it's made up, but it's not readily available.


My fuses are Class-T, but Class-T is a set of standards, not a single standard. My Class-T are physically double the size of the Blue Seas Class-T, and they are rated at 200KV (AC). I can't find the DC rating, but I can't see how it can be less than the Blue Seas. But the frustrating thing is that virtually no one makes DC AIC ratings available, and those that do only show it for high DC voltages (125, or higher) and AIC ratings at lower voltages have to be even better. Pretty sure those NH fuses don't have a published AIC rating for DC (they certainly have an AIC ability, and it may well be better than Class-T, but it's not tested/calculated/published).

[CaptainRivet]

Originally Posted by sailingharry

You are a frequent advocate for NH fuses, and they look pretty slick. Unfortunately, they are virtually non-existent in the US.


As an aside, AIC ratings appear to be important (I'm still not completely convinced that 12V provides enough EMF to maintain an arc on a blown fuse). But, DC ratings are impossible to obtain. The Blue Seas Class-T has a nice DC rating, but that exact same fuse in the commerical/industrial arena only has an AC rating -- where did Blue Seas get that? I'm not saying it's made up, but it's not readily available.


My fuses are Class-T, but Class-T is a set of standards, not a single standard. My Class-T are physically double the size of the Blue Seas Class-T, and they are rated at 200KV (AC). I can't find the DC rating, but I can't see how it can be less than the Blue Seas. But the frustrating thing is that virtually no one makes DC AIC ratings available, and those that do only show it for high DC voltages (125, or higher) and AIC ratings at lower voltages have to be even better. Pretty sure those NH fuses don't have a published AIC rating for DC (they certainly have an AIC ability, and it may well be better than Class-T, but it's not tested/calculated/published).

Yes i am aware in US NH is not well known and used. NH is everywhere in europe as used by state and authorities for grid use. I advocate because you get bulletproof continuously retested massivly overspeced top notch hardware for a very low price. There are also no fakes as it's simply impossible to safe anywhere money in producing them and they are heavly controlled.
Not only the fuses itself but also other NH stuff can be well repurposed for eg busbars.
I can convince you an arc can happen with 12V...I burned a car down and was standing 2m away from the fuse seeing it with my own eyes when an internal shorted 400AH 12V lithium bank arced a 15kA class T fuse. Assume we overloaded the bank or an internal cell defect caused this chain event..the bank didn't catch fire itself, it got quite hot and a lot gas from the blown valves but no fire. but the arced fuse sends all into the cars wiring and the burning wires cause the car to burn down.

NH are tested in DC for all, part of the certification for grid use. You find the ratings in the certification document which is 25% derating in AIC and one NH voltage class down. So the AC 400V 630A with 120kA is also verified DC with 300V with 630A and 100kA AIC. It's not printed into datasheet as they wanna sell their much more expensive pure DC fuses which are the same the grid one just with different print and different gas inside as the low voltage DC doesn't need that expensive gas the grid versions have. Don't know if the class T was a fake but from the arc i suppose the 15kA rating was correct, it was much more that simply bypassed it. I come from car stereo competition and that car had class A amps which draw immense current. That's where we tested a lot and also abused a lot install equipment and batteries. That's why I know their real limits.

AIC is more or less independent from voltage, totally for the 12 till 48V in boat DC use. from around 400V on there is the voltage component that the power can travel around the fuse through the air and basically bypass by arcing the fuse and not go through the fuse where inside a gas and quarts sand is extinguishing the engery. That's why NH3 and Nh4 are have also a longer ceramic body to enlarge the distance and prevent an arc bypassing the fuse.