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Chargery BMS, DCC (Solid State Contactor) thread.

Chargery said:
On BMS program setup menu, can setup "Over Charge P voltage" is OVP setting (HV protection), when any cell voltage reach the setting, BMS will cutoff charge by DCC, "Over Charge R voltage" is the voltage to resume charging, when any cell voltage drop and under the setting, the charging will start again. So when DCC disconnected charging, but the cell voltage drop to the "Over Charge R voltage" setting, the DCC will be connected to charger again, the DCC allow discharging and charging at the same time.

as same as charge protection setting, "Over Discharge P voltage" is UVP setting (LV protection), when any cell voltage reach the setting, BMS will cutoff discharge by DCC, "Over Discharge R voltage" is the voltage to resume discharging, when the lowest cell voltage increase and over the setting, the discharging will start again. So when DCC disconnected discharging, but the cell voltage increased to the "Over Charge R voltage" setting, the DCC will be connected to load again, the DCC allow charging and discharging at the same time.

for BMS, battery has 3 status, storage, charging , and discharging, when battery is in charging and dischaging simutaneously, if charge curren is larger than discharge current, the current reading is positive on BMS, so BMS display battery in CHARGE. If charge curren is less than discharge current, the current reading is negative on BMS, so BMS display battery in DISCHARGE. if charge curren is equal to discharge current or charger and load are turned off, the current reading is Zero on BMS, so BMS display battery in STORAGE.

in DCC, only single SSR , it can receive two signals, one is for over charge protection, another is over discharge protecion, and can cut off bi-directional current. Built-in precharge or predischarge circuit too, don't worry surge current when start to charge or start to discharge. cooling fan is controlled by heat sink temperature, when over 42.5 celcius degree, fan start, under 39 celcius degree, fan turn off. When over 90 celcius degree, DCC disconnect charging or discharging, to prevent DCC from over heating, when under 80 celcius degree, DCC resume charging or discharging automatically.

have a nice day.
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Thank You for answering this Question / Issue Jason.
This raises a Suggestion for the next versions of DCC, Would it be possible to have two LED indicators, Charge & Discharge status ON or OFF. That would help with troubleshooting and knowing what the DCC is being told to do by the BMS at any given time with a quick glance.
 
Steve_S said:
Thank You for answering this Question / Issue Jason.
This raises a Suggestion for the next versions of DCC, Would it be possible to have two LED indicators, Charge & Discharge status ON or OFF. That would help with troubleshooting and knowing what the DCC is being told to do by the BMS at any given time with a quick glance.
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Despite the additional explanations, it is still not clear to me whether indeed in a “common port“/single DCC application, the load/discharge current would still flow even though charging is disabled by the BMS.
 
Pyrofx said:
Only 2 battery lugs. In and out. If it cuts off , off is off. You would need 3lugs to keep charging.
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I thought I saw something about it being bidirectional in which case, charging could work with two lugs as long as the reset on discharge cutoff was appropriate.
 
Pyrofx said:
Come on guys. Basic common sense wiring here. Only 2 battery lugs. In and out. If it cuts off , off is off. You would need 3lugs to keep charging. Charge , battery , inverter. It would need 2 ssr's inside
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I am not trying to fight common sense... I am referring to this post:

https://diysolarforum.com/threads/chargery-bms-dcc-solid-state-contactor-thread.11756/post-141639

which mentions:

Steve_S said:
tim0shel said:
So using it as common port it can actual still allow load but cut off charge and vice versa?
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YES
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I was also wondering how this could be achieved using a single SSR, and this is why I am looking for a clarification.

All I would like to see is a clear, simple statement from the manufacturer such as "Using a single DCC does not give the BMS the ability to provide load current while charge is off (HVD), nor can it provide charge current to the batteries in a LVD condition. Such application requires the use of dual DCC."
 
I'm the dullard here, so I think I'm missing something, but... Isn't the BMS intended to "protect the battery"? In scenarios where you're tripping BMS protections, I'd think you'd want the batteries to be fully disconnected, correct? Other tools in the system, e.g. the inverter/charger & the SCC should be controlling their own charge cycle based on SOC, correct? If you hit the BMS protections, you've got a charge imbalance or a true overcharge/discharge problem that neither of the other two charging devices (or the monitoring system, for that matter) picked up. At that point, the battery says "whoa" and you need to figure out what's up. That's what I'm assuming is going on here, and how I'll put my system together based on that. Teach me if I've said something incorrect.
 
David S said:
I'm the dullard here, so I think I'm missing something, but... Isn't the BMS intended to "protect the battery"? In scenarios where you're tripping BMS protections, I'd think you'd want the batteries to be fully disconnected, correct? Other tools in the system, e.g. the inverter/charger & the SCC should be controlling their own charge cycle based on SOC, correct? If you hit the BMS protections, you've got a charge imbalance or a true overcharge/discharge problem that neither of the other two charging devices (or the monitoring system, for that matter) picked up. At that point, the battery says "whoa" and you need to figure out what's up. That's what I'm assuming is going on here, and how I'll put my system together based on that. Teach me if I've said something incorrect.
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I'm right on the same page as you. When this thing shuts off, I'll dig out the chargery display and the massive pile of printed instructions and figure out what went wrong and how to make it turn on again :D. This whole setup is a 'last-resort' shutoff in my opinion, that in an ideal situation, never really has to do anything because the SCC and inverter and balanced cells are doing their jobs correctly.
 
David S said:
I'm the dullard here, so I think I'm missing something, but... Isn't the BMS intended to "protect the battery"? In scenarios where you're tripping BMS protections, I'd think you'd want the batteries to be fully disconnected, correct? Other tools in the system, e.g. the inverter/charger & the SCC should be controlling their own charge cycle based on SOC, correct? If you hit the BMS protections, you've got a charge imbalance or a true overcharge/discharge problem that neither of the other two charging devices (or the monitoring system, for that matter) picked up. At that point, the battery says "whoa" and you need to figure out what's up. That's what I'm assuming is going on here, and how I'll put my system together based on that. Teach me if I've said something incorrect.
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You are ENTIRELY CORRECT !

Some folks for some strange reason think the BMS should be doing all the controlling of everything and make it the boss. An entirely RIDICULOUS NOTION and comletely the wrong way to look at BMS'.

A BMS has ONE JOB, to protect the cells / pack that it is controlling, NOTHING MORE. Some added Passive or Active Balancing but that also has NOTHING to do with controlling externals.
 
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Steve_S said:
You are ENTIRELY CORRECT !

Some folks for some strange reason think the BMS should be doing all the controlling of everything and make it the boss. An entirely RIDICULOUS NOTION and comletely the wrong way to look at BMS'. I am positive some Lurker will slam me for it but that only exposes their own ignorance. Go ahead and BASH away I don't give a flying hoot.

A BMS has ONE JOB, to protect the cells / pack that it is controlling, NOTHING MORE. Some added Passicve or Active Balancing but that also has NOTHING to do with controlling externals.

BTW: If I sound Crusty on this, it is because I have been attacked for it, I know a lot more than many and less than many others and probably have forgotten more than many will ever learn. There isn't much room for Alt Realities or Non-Thinking when it comes to electricity and systems.

Lastly, yes I am getting frustrated, a bit fed up & pissed off with stupid. So I've backed off many things but am ready to OUT morons with a giant FU and let them go back to where they were banned from.

If someone piles on all sorts of advice and has no "About my System" pages or descriptions & photo's of what they've done, have or are running, take it with a COW LICK of Salt and engage Critical Thinking + Common Sense. Opinions are like A-Holes, everyone has one, as a friend from Texas says a lot to remind folks.
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In my world, this is "Defense in Depth". We want layers of protection around these critical, and potentially dangerous, systems. We want those layers to be discrete, with only awareness of issues being made available to higher or lower level layers. Interconnecting these layers introduces opportunities for failures across layers, which is bad.
 
Pyrofx said:
Come on guys. Basic common sense wiring here. Only 2 battery lugs. In and out. If it cuts off , off is off. You would need 3lugs to keep charging. Charge , battery , inverter. It would need 2 ssr's inside
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It would not require 3 lugs .... It would only require 2 unidirectional SSR's in the case. The battery would be wired to one lug and charge and load to the other .... If you shut off the load SSR current would still be allowed to flow into the battery Thru it's SSR... and the other way around ...... BUT, as Jason explained, there is only one bi-directional SSR in the DCC so this is NOT the way it works.

Independent control of charge and load will require 2 DCC's.

I'm not sure why @Steve_S refuses to correct his answer to this question .... but instead is angry at people who want to use the Chargery in ways that don't suit him. I'm sure all us Chargery users are grateful for the tremendous amount of work Steve has done improving the documentation and working with Jason to bring other changes to the product that will be very good for us and for Chargery ..... but .... I don't think the kind of outburst in post #48 has any place here.
 
David S said:
I'm the dullard here, so I think I'm missing something, but... Isn't the BMS intended to "protect the battery"? In scenarios where you're tripping BMS protections, I'd think you'd want the batteries to be fully disconnected, correct? Other tools in the system, e.g. the inverter/charger & the SCC should be controlling their own charge cycle based on SOC, correct? If you hit the BMS protections, you've got a charge imbalance or a true overcharge/discharge problem that neither of the other two charging devices (or the monitoring system, for that matter) picked up. At that point, the battery says "whoa" and you need to figure out what's up. That's what I'm assuming is going on here, and how I'll put my system together based on that. Teach me if I've said something incorrect.
Click to expand...

Your not wrong, but your also not totally right.

What you have articulated is one valid and legit approach to battery protection. Basically if anything goes wrong, a manual reset will probably be required, requiring human intervention (and thus awareness of the problem). This is one use case for common port BMSes (though most people just use common port because they are deadset on high current 12v systems and need a cheap way to do that).

However the downside (also upside depending on your perspective) is their is no automated recovery. If a common port BMS cuts everything due to a low voltage condition or a low temperature condition, the system has no way to recover from this without the user intervening. In some cases this is what you want, in other cases this could be viewed as an inconvenience or a problem.

I think at the end of the day it all depends on your model and use case. The BMS should not be the first line of defense and should seldom or never trip in most designs, however with the cheap high capacity grey market cells everyone is buying its not so unlikely that cells voltages will discharge irregularly towards the lower knee and in some cases might trip the BMS LVD before the pack level Inverter LVD. Low temperature disconnect would be another example of when you might want to design separate controls for charging (~0*C) and discharging (can handle much colder).

edit: I love that term/concept you referenced in your last comment "defense in depth." Never heard that before.
 
Dzl said:
Your not wrong, but your also not totally right.

What you have articulated is one valid and legit approach to battery protection. Basically if anything goes wrong, a manual reset will probably be required, requiring human intervention (and thus awareness of the problem). This is one use case for common port BMSes (though most people just use common port because they are deadset on high current 12v systems and need a cheap way to do that).

However the downside (also upside depending on your perspective) is their is no automated recovery. If a common port BMS cuts everything due to a low voltage condition or a low temperature condition, the system has no way to recover from this without the user intervening. In some cases this is what you want, in other cases this could be viewed as an inconvenience or a problem.

I think at the end of the day it all depends on your model and use case. The BMS should not be the first line of defense and should seldom or never trip in most designs, however with the cheap high capacity grey market cells everyone is buying its not so unlikely that cells voltages will discharge irregularly towards the lower knee and in some cases might trip the BMS LVD before the pack level Inverter LVD. Low temperature disconnect would be another example of when you might want to design separate controls for charging (~0*C) and discharging (can handle much colder).

edit: I love that term/concept you referenced in your last comment "defense in depth." Never heard that before.
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100% understood and agreed. The idea of automated recovery fits into the "DiD" model as notification of state across layers. The challenge here is that something has to be able to rectify that circumstance in an automated fashion. It's unclear to me how a passive BMS does that, particularly at the cell or supercell level unless it has the ability to set its cell charge levels automatically. If you cut power at the batteries, the BMS may be the only thing that HAS power available to it so, in that case, it's the only thing that could feasibly resolve the condition. This is particularly challenging when you consider applications where a human may not be onsite, but again, if the batteries are panicking, maybe a human needs to check.
 
For my application, a common port configuration just seems .... illogical.... no, I don't have pointy ears.

Why would I want to disable charging if I have a LVD? I'd really like to get the pack charged back up as soon as possible.
Why would I want to disable load if I have a HVD? Seems like bleeding off some of that charge would be a good idea.
I don't understand why there are 2 low temperature disconnect setpoints ... one for charge and one for load .... if both are to be disabled at the same time.
 
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Bob B said:
For my application, a common port configuration just seems .... illogical.... no, I don't have pointy ears.

Why would I want to disable charging if I have a LVD? I'd really like to get the pack charged back up as soon as possible.
Why would I want to disable load if I have a HVD? Seems like bleeding off some of that charge would be a good idea.
I don't understand why there are 2 low temperature disconnect setpoints ... one for charge and one for load .... if both are to be disabled at the same time.
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Perhaps there are two setpoints because this BMS can run with either a common or separate port (with a 2nd DCC).
 
" if any warning events triggered on BMS, the DCC don't charge or discharge," That is a quote from Jason's post.
 
I do have one concern about using SRRs is that they fail closed (conducting) and since the BMS high/low disconnect is the final "oh crap" line of defense and if the SSR had failed you wouldnt know it until you needed it to disconnect and it didnt happen.

Having said that, 'Quality' SSRs are ultra-reliable and can last decades if not abused. I dunno... the power usage is a non-issue for me since it's dead easy to rig up a Resistor/Capacitor circuit to greatly reduce a contactor coils power usage. I think somebody already mentioned Gigavac - they make awesome contactors and they dont break the bank either.

BTW, you can make a dead simple precharge circuit by jumping the input and output of a relay with a 1.3-1.8 megaohm resistor (depending on system voltage). Its resistance is so high that it won't allow the inverter (or whatever) to turn on but they will keep capacitors mostly charged and it's less than a watt usage.
 
The only way for a mosfet to fail shorted is by over current (most likely you short the battery cables) and I will always recommend a fuse in addition to the BMS; it will take care of that problem in case it happens ;)

A 1 M resistor is far too high, it'll never charge the inverter caps (too much leakage), let alone if there's other loads. at the same time.
 
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