Chargery BMS now with Low Temp Cutoff

[Calothrix]

"If you are not learning you are dying"

Thanks grizzzman.....over these last few months I am definitely NOT dying!

 

[grizzzman]

That's exactly what the RC network do. It's just less efficient than 2 separate coils because you loose some power in the resistor but it's better than nothing. But if the relays have this functionality already, why the question was asked in the first place?



That is the case if you try to push the economy too far, but with a 1:2 ratio only it's pretty safe, even in mobile applications. The G force it would take to open a closed relay, even at half the coil current, would probably destroy a lot of things in your vehicle, including yourself.



Yes. But if there's no power to the relays how your others loads are powered then?

That's exactly what the RC network do. It's just less efficient than 2 separate coils because you loose some power in the resistor but it's better than nothing. But if the relays have this functionality already, why the question was asked in the first place?



That is the case if you try to push the economy too far, but with a 1:2 ratio only it's pretty safe, even in mobile applications. The G force it would take to open a closed relay, even at half the coil current, would probably destroy a lot of things in your vehicle, including yourself.



Yes. But if there's no power to the relays how your others loads are powered then?

If efficiency is what we are after, why not buy a relay that IS more efficient?

 

[Calothrix]

Yes if the fuse block is connected to the battery directly (not recommended for obvious reasons)

Not so sure what the "obvious reasons" are. I'm guessing the major concern would be my DC loads discharging the batteries too low?

 

[BiduleOhm]

If efficiency is what we are after, why not buy a relay that IS more efficient?

Yes, of course, it's the best solution. But my guess is money. and also you need some force and speed to close and open the contact properly so it doesn't arc and destroy itself. And that requires energy so you can't have a super efficient mechanical relay, wheatever you do.

Not so sure what the "obvious reasons" are. I'm guessing the major concern would be my DC loads discharging the batteries too low?

Yep, the BMS will not be able to protect the battery from what can happen from those loads.

 

[grizzzman]

Not so sure what the "obvious reasons" are. I'm guessing the major concern would be my DC loads discharging the batteries too low?

You bypass the BMS, you take your chances of failure.

 

[Calothrix]

If efficiency is what we are after, why not buy a relay that IS more efficient?

$..... A quick search on the Gigavac GV200M that DW SD recommended showed a cost close to $500.00 for 4 of them. Not sure if there are less expensive, efficient AND reliable relays out there?.....will have to ponder the efficiency vs cost thing and make a decision. If I could turn off my bms/inverter when not using any AC loads, and figure out a way to still power my DC loads, while protecting my batteries at the same time?.....now that would be the cat's meow!

 

[tim0shel]

$..... A quick search on the Gigavac GV200M that DW SD recommended showed a cost close to $500.00 for 4 of them. Not sure if there are less expensive, efficient AND reliable relays out there?.....will have to ponder the efficiency vs cost thing and make a decision. If I could turn off my bms/inverter when not using any AC loads, and figure out a way to still power my DC loads, while protecting my batteries at the same time?.....now that would be the cat's meow!

Im confused why you say 4 of them. Reality way I see it you would really only need 1 at most 2. But depending on your charge input you could go with a more standard Relay. Just your main discharge would need the GV200M or similar like this

 

[grizzzman]

Im confused why you say 4 of them. Reality way I see it you would really only need 1 at most 2. But depending on your charge input you could go with a more standard Relay. Just your main discharge would need the GV200M or similar like this

Two battery banks as explained earlier in this thread.

 

[DW SD]

I did not ingest the idea that you had two battery banks.
Is it an option for you to parallel wire the battery banks or cells and then just use 1 contactor? That would eliminate 1/2 of your static loads.

I mentioned this before, but if your inverter is also a charger, it'd be a waste to use one contactor for load and one for discharge. Because one large cable would serve for charge and discharge to the inverter / charger, you'd then need to wire the contactors in series, also for them to be effective in protecting the battery.

 

[Calothrix]

Is it an option for you to parallel wire the battery banks or cells and then just use 1 contactor? That would eliminate 1/2 of your static loads.

Don't know, I will have a 12 volt, 4s2p system and the original diagram that Jason sent me called for 4 relays. From Steve S. response to another question I posed, it is probably best that I have a shunt (and I assume two relays) for each battery pack so I can know better what is happening with each battery and not just the two-battery system as a whole.

I mentioned this before, but if your inverter is also a charger

My inverter is not a charger.

Thanks!

 

[Steve_S]

Don't know, I will have a 12 volt, 4s2p system and the original diagram that Jason sent me called for 4 relays. From Steve S. response to another question I posed, it is probably best that I have a shunt (and I assume two relays) for each battery pack so I can know better what is happening with each battery and not just the two-battery system as a whole.
My inverter is not a charger.
Thanks!

I am presently in combat wth the Relay & Delay board section of the manual... geeez, what a mess... My chinglish decoder ring overloaded ! ;-) but I'm getting there. I am also waiting on more detail & technical info from Jason as there are too may "blanks" that need to be addressed. I'm also doing several new images which should help folks a lot more (well I hope anyways) because images are much easier to grasp concepts with. This is a MUCH BIGGER project that envisioned. Also the source docs are in MS Word with MS imbedded graphics.. I use LibreOffice (says the former Microsoft Core Systems Engineer) and so the DOCX got a tad mangled in conversions... major ughness.

ON Config & Topology for it. Chargery BMS' are designed to be used either as "Common Port" or "Separate Port" modes. This was done to support use in EV's and to allow maximum flexibility overall for as many use cases as possible. This has it's Pro's & Con's and a dash of compromise mixed in. In the majority of "Residential" type configurations, the Common Port mode is used because there is a Solar Charge Controller, an Inverter/Charger and possibly a 3rd backup charging system (AC->DC-Charger). Given that charge & discharge come through the same common DC lines both the Charge & Discharge relays have to be on that same common (+) line and the Shunt on the common (-) DC line. That having been said there are various ways to wire this but it becomes much more complex to make a hybrid Common/Separate schema & not entirely practical one at that.

Separate Port mode is more suitable to EV use and for separated / isolated systems, where the load may be a motor rather than an Inverter and the charging is done via dedicated high amp charger unit and with supplemental charging such as regenerative braking. By splitting out the Relay Controls to handle this it allows for all the components to be wired in and managed correctly. Additionally, the Delay Board is designed more for the use of a Separate Port configuration and even allowing for "small discharge" and "large discharge" relays as well as the charging relay, with settable delay extensions for such uses. It's not a usual item for a fixed system like a house / cabin in Common Port configuration. I personally got them to have them available "just in case" I hit an unexpected wall with my build out, I figured that an extra $4.50 was worth it just for peace of mind in case I needed them. If the delays boards would have been expensive I would not have gotten them, or just one.

Lastly on the Relays again. The Relays sold by Chargery are good, heavy duty contactor relays and again, they are aimed at the EV / Vehicular application. Remember that an EV uses a LOT of juice and is typically recharged by an external source every day / evening. In that sort of application the extra juice these relays burn off is not that significant in the grand scheme of things. Unfortunately in a non-EV application like a House, RV/Camper or Boat, these relays use "too much" power over a 24 hour period. While not huge and which can be put back during daily charging by Solar it's still wasted power that will add up over a few dark & dismal days. To that end, I am waiting on more info from Jason in regards to SSR's (Solid State Relays) which use considerably less power to keep the latch closed, of course they are more costly. I've also forwarded the idea that Chargery should offer SSR's as well as the traditional electromechanical contactor relays currently offered. So that is being worked on and we will see soon how that could work out. It would be ideal if Chargery could offer the SSR's at a respectable price for a respectable quality relay.

For simple clarity. Each BMS requires ONE Discharge Relay and ONE Charging relay. Skipping either disables the ability to control that function and that is plain and simply dumb ! These are the ON/OFF for charging & discharging. The relays handle the High Amperage use that FET based systems cannot. TBH, over 150A a FET based BMS is in deep iffy territory. The few that do go 150A and above have heat sinks ,sometimes active cooling and more features for safety & protections and they also cost a heap load more in general, as a result not that common.

Hope this answers some questions
Steve

 

[DW SD]

I decided to draw a quick schematic of how I wired my load / charge disconnect relays (IE. Common port configuration). A picture is worth 1k words, right?

Admittedly, my handwriting could use some improvement. Functionally, this is identical to having two contactors wired in series (any fault condition will interrupt charging or loads) But, the Bosch cube relay is much cheaper and also uses modest power (2W @ 12V) like an expensive GV200M.
Note, pins 85 / 86 are the trigger pins controlling closure of the solenoid contacts.
Hope this helps someone.

Steve,
Your modification of the instructions will be very helpful. I appreciate the investment of your time all over this forum.
Cheers,
Doug

 

[BiduleOhm]

@Steve_S you do realize that this BMS + SSR is exactly the same than having a FET based BMS? but it'll be more expensive and take more space than the classic BMS... Everything you have against FET BMS you can also apply it to SSR as they are MOSFET based (for the DC versions, for the AC versions SCRs or triacs are more common).

 

[Capt Bill]

Thank You, I need to study this before I order my BMS for my first 24v LifePO4s ever. I am also tooling up to test and balance my batteries before I put em online to my solar system. Thanks for the lesson and that drawing. I will come back to re-read and letthis info. sink farther in soon.

 

[chevymike]

@Calothrix If you are doing a 4s2p system, then it does treat each set of 4 batteries as an individual pack. In this case you would want to run 2 BMS's. You should be able to use the reply outputs from each BMS to connect to a single pair of relays so if any one bank is out of limit, it will shut off whichever circuit is out of limit. I would likely use diodes from each BMS to prevent any back feed from one to the other via the relay circuit.

That said, based on Will's info/recommendation he has done in some of his videos, you might want to consider a 2p4s system. This will only use one BMS and one set of relays. True it does not monitor each individual cell but if you have high quality cells and have balanced them, it seems there is no issues with this. Cuts costs and possible troubleshooting issues but does lack some redundancy.

My plan is to use option 2p4s as it is the simplest, cheapest and all my batteries spec exactly the same (voltage, age, etc).

 

[Steve_S]

@Steve_S you do realize that this BMS + SSR is exactly the same than having a FET based BMS? but it'll be more expensive and take more space than the classic BMS... Everything you have against FET BMS you can also apply it to SSR as they are MOSFET based (for the DC versions, for the AC versions SCRs or triacs are more common).

If the BMS get's cooked, your down till it's replaced. If the SSR get's cooked, you can easily replace it, even with a mech temporarily or even bypass it in an emergency situation and your still going. I have nothing against FET equipment but it does have it's limits and little tolerance when taken out of spec. Where do most "classic" BMS' fail ? Consider as well the Orions, TinyBMS, ElectroDacus and others that make use of relays, when and where appropriate.

 

[BiduleOhm]

If the BMS get's cooked, your down till it's replaced. If the SSR get's cooked, you can easily replace it, even with a mech temporarily or even bypass it in an emergency situation and your still going.

You can also easily by-pass a FET based BMS.

I have nothing against FET equipment but it does have it's limits and little tolerance when taken out of spec. Where do most "classic" BMS' fail ?

Yes but that's because they use components sold in back alleys, design for the normal case (or even best case) and have zero margin (or even negative margin). If you design for the worst case, add some margin on top and use top tier components the FET based solution will outlast any mechanical relay (even so I love mechanical relays).

Consider as well the Orions, TinyBMS, ElectroDacus and others that make use of relays, when and where appropriate.

Don't know about the Orions and TinyBMS but the SBMS0 uses the DSSR20 which is a SSR.

 

[Calothrix]

Thanks guys, good discussion. Judging by the looks of it, I'm guessing this BMS recommended by Will (credit to Will for below images!) is FET based:



Will shows how you can wire the 100A version in parallel below but they also make a 120A version:



I would only have two batteries instead of the three depicted but if I used two of the 120A version BMS for a total of 240A, would that be sufficient for my 2200 watt inverter? 2200W/12V = 183A.....so it looks like the 240A would cover the continuous wattage but is it good enough for surge wattage?

Also, Will's diagram only shows how the discharge side of the equation is wired. Would I also have to buy two more of these BMS (likely the 100A version) for the charge side of the equation (I'm charging from my alternator, not solar panels)? Thanks!

 

[Steve_S]

Thanks guys, good discussion. Judging by the looks of it, I'm guessing this BMS recommended by Will (credit to Will for below images!) is FET based:
~snip
Will shows how you can wire the 100A version in parallel below but they also make a 120A version:
~snip
I would only have two batteries instead of the three depicted but if I used two of the 120A version BMS for a total of 240A, would that be sufficient for my 2200 watt inverter? 2200W/12V = 183A.....so it looks like the 240A would cover the continuous wattage but is it good enough for surge wattage?

Also, Will's diagram only shows how the discharge side of the equation is wired. Would I also have to buy two more of these BMS (likely the 100A version) for the charge side of the equation (I'm charging from my alternator, not solar panels)? Thanks!

Yes FET based and ok.
120A BMS is a better bet in general terms... more elbow room the better.
These are "Common Port" therefore they take charge & discharge through the same common battery lines. There is no need for more that that. Well fuses on the batteries but that should do It for the basics.
NOTE that his diagram shows a BUS Topology, meaning that the wires from packs are equal in length and go to a (+) & (-) bus bars / load distribution points, then to load (inverter). This helps keep balance and equilibrium for loads. (basically)
! Charging from Alternator has caveats, this has been gone over at length in various threads.

BTW, just in case, this is a Chargery BMS thread

 

[Dzl]

@Steve_S you do realize that this BMS + SSR is exactly the same than having a FET based BMS? but it'll be more expensive and take more space than the classic BMS... Everything you have against FET BMS you can also apply it to SSR as they are MOSFET based (for the DC versions, for the AC versions SCRs or triacs are more common).

I agree with you, but I think you are undervaluing the value of modularity/replaceability/configurability. An all in one BMS has its benefits (simplicity, space efficiency, maybe electrical efficiency(?) or cost(?) IDK), but a BMS that outsources switching to relays allows the user to decide what is right for them, and to easily replace relays in the case of failure or in the case of their needs changing. I don't think one model is definitively better than the other, they just have different advantages and disadvantages.

Don't know about the Orions and TinyBMS but the SBMS0 uses the DSSR20 which is a SSR.

I think Steve was just pointing out that there are many BMS' that take the approach of outsourcing switching to external devices (relays or otherwise).

 

[BiduleOhm]

That's not what he said, nor what was the original debate but, yep, I agree with what you said; modular is very often the best solution

 

[Dzl]

That's not what he said, nor what was the original debate but, yep, I agree with what you said; modular is very often the best solution

Yeah the modularity thing was just what popped into my head when I was thinking through the pros and cons of each approach

 

[Calothrix]

BTW, just in case, this is a Chargery BMS thread

Thanks for the reminder Steve.....I'm drifting off topic! Well, now back to that Victron Wiring Unlimited document you recommended to swell my brain a little more.....Chapter 4.2 Busbars!

 

[Craigmck]

I am presently in combat wth the Relay & Delay board section of the manual... geeez, what a mess... My chinglish decoder ring overloaded ! ;-) but I'm getting there. I am also waiting on more detail & technical info from Jason as there are too may "blanks" that need to be addressed. I'm also doing several new images which should help folks a lot more (well I hope anyways) because images are much easier to grasp concepts with. This is a MUCH BIGGER project that envisioned. Also the source docs are in MS Word with MS imbedded graphics.. I use LibreOffice (says the former Microsoft Core Systems Engineer) and so the DOCX got a tad mangled in conversions... major ughness.

ON Config & Topology for it. Chargery BMS' are designed to be used either as "Common Port" or "Separate Port" modes. This was done to support use in EV's and to allow maximum flexibility overall for as many use cases as possible. This has it's Pro's & Con's and a dash of compromise mixed in. In the majority of "Residential" type configurations, the Common Port mode is used because there is a Solar Charge Controller, an Inverter/Charger and possibly a 3rd backup charging system (AC->DC-Charger). Given that charge & discharge come through the same common DC lines both the Charge & Discharge relays have to be on that same common (+) line and the Shunt on the common (-) DC line. That having been said there are various ways to wire this but it becomes much more complex to make a hybrid Common/Separate schema & not entirely practical one at that.

Separate Port mode is more suitable to EV use and for separated / isolated systems, where the load may be a motor rather than an Inverter and the charging is done via dedicated high amp charger unit and with supplemental charging such as regenerative braking. By splitting out the Relay Controls to handle this it allows for all the components to be wired in and managed correctly. Additionally, the Delay Board is designed more for the use of a Separate Port configuration and even allowing for "small discharge" and "large discharge" relays as well as the charging relay, with settable delay extensions for such uses. It's not a usual item for a fixed system like a house / cabin in Common Port configuration. I personally got them to have them available "just in case" I hit an unexpected wall with my build out, I figured that an extra $4.50 was worth it just for peace of mind in case I needed them. If the delays boards would have been expensive I would not have gotten them, or just one.

Lastly on the Relays again. The Relays sold by Chargery are good, heavy duty contactor relays and again, they are aimed at the EV / Vehicular application. Remember that an EV uses a LOT of juice and is typically recharged by an external source every day / evening. In that sort of application the extra juice these relays burn off is not that significant in the grand scheme of things. Unfortunately in a non-EV application like a House, RV/Camper or Boat, these relays use "too much" power over a 24 hour period. While not huge and which can be put back during daily charging by Solar it's still wasted power that will add up over a few dark & dismal days. To that end, I am waiting on more info from Jason in regards to SSR's (Solid State Relays) which use considerably less power to keep the latch closed, of course they are more costly. I've also forwarded the idea that Chargery should offer SSR's as well as the traditional electromechanical contactor relays currently offered. So that is being worked on and we will see soon how that could work out. It would be ideal if Chargery could offer the SSR's at a respectable price for a respectable quality relay.

For simple clarity. Each BMS requires ONE Discharge Relay and ONE Charging relay. Skipping either disables the ability to control that function and that is plain and simply dumb ! These are the ON/OFF for charging & discharging. The relays handle the High Amperage use that FET based systems cannot. TBH, over 150A a FET based BMS is in deep iffy territory. The few that do go 150A and above have heat sinks ,sometimes active cooling and more features for safety & protections and they also cost a heap load more in general, as a result not that common.

Hope this answers some questions
Steve

well said

 

[tim0shel]

FYI the Pelican micro 1020 fits the display perfectly