Building a 280ah 48v prismatic bank: help me choose a BMS please

[hammick]

We have an off grid vacation place. No grid power. I use Schneider Conext equipment with a 5,500 watt inverter and a 60a solar charge controller. Been using lead acid for six years but time to get new batteries. I'm going to order 16 of the prismatic 280ah cells from Deligreen. I've been reading until my head spins about BMS. Though I was sold on the Orion BMS Junior but it doesn't appear to be able to limit current or charging without hooking relay outputs to my charger and inverter. This seems overly complicated and not sure it's even possible on my equipment. The specs of my equipment is listed below. I need a BMS that has over-discharge disconnect, temperature disconnect and over-charge disconnect.

My solar charge controller is 60 amps and I have the ability to customize all voltage settings of bulk, absorb, and float. I can set the amount of time in absorb and I can limit the charge percentage.

I would like to have digital screen for the BMS or Bluetooth. Remote wireless monitoring would be great. But these are not must have options. I can monitor my solar equipment remotely so I can see the state of charge assuming I am able to use my Conext shunt based battery monitor with LifeP04s.

My specs:

Inverter: 5,500 watts continuous output; 9,500 watt surge for 1 minute; 9,000 watt surge for 5 minutes; 7,000 surge for 7 minutes
26 watts idle consumption; 150 amp DC charger that can be set from 1% to 100%


I don't mind spending some money on a quality BMS. Our place will be vacant for several months at a time so I need a quality and reliable BMS.

Thanks.

 

[Dzl]

The max current on the DC side if you want your inverters full capabilities to be available is roughly ~235A @ 48v

With your size system, its possible to get a FET based BMS that can handle that current (Daly for instance), but personally I would be looking at BMSes with either relay based control or direct device control.

These are generally a little more complicated than FET based ('all-in-one' style BMS' like Daly or JBD), but also more advanced and better suited for high power systems.

The two most popular mid range options here in these categories are the Chargery (relay based) and the SBMS0 (direct device control and/or relay based). TinyBMS is another option worth considering, and can be used as a FET based BMS for low current applications or relay based for higher current applications.

On the high end (most people on this forum (It would be fair to call use cheapskates ) can't or won't justify the cost, but for a system like yours, I think you can justify the expense on high end protection, it won't be a huge % of your total system cost) some options to consider are:
123smartBMS
Rec BMS
Batrium
Orion

I've been particularly curious about the 123smartBMS and TinyBMS lately, as well as my current personal favorite the SBMS0 (which is a bit of a niche option but pretty flexible). The first two are European products, the latter is Canadian.

 

[Steve_S]

Orion BMS are Top Quality products and do exactly what they should and very well.
Yes, they use contactors which enable them to handle all manner of loads without issues.
Appreciate, that a BMS is the Last Stop Guard Dog to protect the battery pack. The SCC & Inverter is supposed to disconnect for Low & High voltage situations. The BMS is only supposed to disconnect the battery pack if an Error State occurs, such as Hi/Lo Volts, Hi/Lo Temps or cell failure. Therefor a contactor is used to handle that aspect.

I am a Chargery BMS guy and these BMS' use Relay/Contactors for control as well.

 

[JoeHam]

I've been particularly curious about the 123smartBMS and TinyBMS lately, as well as my current personal favorite the SBMS0 (which is a bit of a niche option but pretty flexible). The first two are European products, the latter is Canadian.

Unless something has changed I think the Electrodaucus is not an option for 48v nominal.

 

[hammick]

Thanks guys. We have never taken anything close to 235a continuous or even surge. I just did a test with my Trimetric shunt monitor. It took the vacuum cleaner, well pump and microwave in addition to regular household stuff running to get to 100 amps. This was with the CC disconnected.

Problem is Schneider has been way behind the game with Lithium support and firmware updates. They are catering to the expensive LifeP04 manufactures for plug and play configuration. They have left the DIY guy high and dry. I can make the solar charge settings work but the only way to hook a BMS with contactors is through the inverter's RPO (remote power off) switch. And that shuts everything down including the charge controller. You must be physically present to power everything back up. The CC must be disconnect from battery and solar to power back up. Not something you want when you are 1,200 miles away for a few months. I guess I could disconnect the communication cord from the CC when I'm not there so just the inverter and other components shut down.

 

[Steve_S]

Schneider is not the only one being a laggard for LiFePO4 Support. My MIdnite SCC has to be Kludged to work nicely and even my Samlex with it's infinite programability does not have a "natural" LFP profile. These are Not Cheapster Value junk either. Even more ironic which has caused me to No Longer Recomend Midnite to anyone is that when I spoke with their Tech Support people, they more or less were not interested in modding the firmware to support LFP, in fact, they told me to go to their Forum and that the users will have the answers. NOT A SELLING POINT, especially for SCC's that sell for $900+

Samlex on the otherhand did mod their firmware and continue to stay on top of it by releasing new updates. UNfortunately, like Schneider, the external controls can turn OFF the entire unit and not just the Inverter while leavig the charger on. I suspect that will be pretty much universal on such equipment.

 

[hammick]

Thanks for the great info guys. I have a call into Orion to speak with a tech. I spoke with the receptionist yesterday and she told me to put it all in an email. Way too much for an email so hopefully I can speak with someone. If I can get by with just a battery disconnect relay I suppose I could figure that out safely.

 

[hammick]

So thinking out loud do I really need a BMS or can I get buy with the custom settings on my inverter and charge controller and just use a battery balancer like the one below?

I can set my CC so it doesn't charge the battery more than a certain voltage. I would make sure that it is at a lower voltage when the place is vacant. I can set the inverter's LVCO (low voltage cut off) as high at 48 volts. So I am really only missing low temperature disconnect. Schneider could easily add a setting to not allow charging below a certain temperature. Hell I can add up to 4 temperature sensors to my batteries for redundancy. But Schneider will never do that so I would have to use the aux function of the CC to power a high amp 12v battery disconnect relay. The aux function has numerous selection to activate the relay including specific battery temperature. My only concern is if the relay disconnects when there is full sun hitting the panels. Will this fry my CC? Trying to get the answer to that question. Now I have certainly disconnected the CC to battery breaker before I disconnected the CC to panel breaker (before I knew better) and it didn't hurt my CC but not sure if that has ever happened when it was cranking out big amps to the batteries. I would hope my $600 CC is protected in some way.

Or maybe keep it simple and just insulate my battery box in the winter. The batteries are in our insulated garage. I've never seen it get colder than 37 degrees but it's Montana so anything can happen. We have a thermostat controlled propane ceramic heater in the garage that I could reluctantly leave on in winter when we are not there. I already have a propane stove in the living area that I leave on and can control wirelessly with my Iphone. I could add one of those wifi thermostats to the garage heater. Lot's of options I guess.

Or I could just keep my Trojans and use them when the place is vacant. I guess redundancy is good when you are off grid.

So what are your guy's thoughts on just a balancer?

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[Dzl]

Unless something has changed I think the Electrodaucus is not an option for 48v nominal.

Oops you are correct, forgot we were talking 48v, SBMS is not an option, I think all the others I mentioned (apart from JBD and SBMS) are an option at 48v.

So thinking out loud do I really need a BMS or can I get buy with the custom settings on my inverter and charge controller and just use a battery balancer like the one below?
...
So what are your guy's thoughts on just a balancer?

The role of a BMS is to protect and manage your battery packs at the cell level, no other component can take its place fully. You can control battery bank level charge and discharge logic with your chargers and load control devices (AC + DC LVD) but none have cell level awareness and therefore cannot take actions to protect your battery pack based on cell level issues. This is why its important to have a BMS.

People sometimes choose to forego a BMS partially or fully, but those people should (1) understand the risk and additional responsibility (2) have higher risk tolerance (3) use conservative charge/discharge settings (4) have enough experience and knowledge to understand what they are doing (5) and know that they need to be more active in the management of their system, since they are foregoing automated protection. If you forego a BMS you are the BMS.

To me, a BMS is a no brainer as a default since it doesn't need to be a huge % of the total system cost or need to be complex, and it provides meaningful protection and peace of mind (and I don't trust myself enough to not screw up or be forgetful).

 

[hammick]

Oops you are correct, forgot we were talking 48v, SBMS is not an option, I think all the others I mentioned (apart from JBD and SBMS) are an option at 48v.



The role of a BMS is to protect and manage your battery packs at the cell level, no other component can take its place fully. You can control battery bank level charge and discharge logic with your chargers and load control devices (AC + DC LVD) but none have cell level awareness and therefore cannot take actions to protect your battery pack based on cell level issues. This is why its important to have a BMS.

People sometimes choose to forego a BMS partially or fully, but those people should (1) understand the risk and additional responsibility (2) have higher risk tolerance (3) use conservative charge/discharge settings (4) have enough experience and knowledge to understand what they are doing (5) and know that they need to be more active in the management of their system, since they are foregoing automated protection. If you forego a BMS you are the BMS.

To me, a BMS is a no brainer as a default since it doesn't need to be a huge % of the total system cost or need to be complex, and it provides meaningful protection and peace of mind (and I don't trust myself enough to not screw up or be forgetful).

Thanks. I assuming a good BMS will shut down charging if one cell gets beyond a set point and not just try to burn off the high charge? Obviously my CC will just see the total pack voltage and can't detect a runaway cell. A quality balancer will keep the cells in balance but can't shut down charging if there is a runaway cell. Do I have this correct? So the BMS is there to prevent a fire and/or damage to other cells if one runs away?

Thanks.

 

[Dzl]

Thanks. I assuming a good BMS will shut down charging if one cell gets beyond a set point and not just try to burn off the high charge?

Correct. Over and Under voltage protection/disconnection, is a core feature of a BMS (and probably the main thing that differentiates a balancer from a balancing BMS).

Obviously my CC will just see the total pack voltage and can't detect a runaway cell. A quality balancer will keep the cells in balance but can't shut down charging if there is a runaway cell. Do I have this correct? So the BMS is there to prevent a fire and/or damage to other cells if one runs away?

Kind of, yes. A balancer will try to keep the cells balanced but if it cannot and there is no BMS, there is no second line of defense. The larger the cells the more pronounced a mismatch will be and the harder a balancer will have to work to compensate. I don't remember what cells you have but people have been reporting some not-small imbalances/mismatches with the 280 EVE cells. So even with an active balancer shifting energy on the fly, having a BMS that can step in if the cells do not remain adequately balanced, or if a cell develops a more severe problem, is good insurance. At least that's how I see it--but I'm far from an expert.

 

[ghostwriter66]

I am a Chargery BMS guy

You ARE the Chargery guy!!!

 

[100kwh-hunter]

@hammick,
Yes you will need a bms.
If you need a balancer(active or passive) then it would be wise to check the health of your cells or manually connect in parallel balance them.
A balancer is a welcome device, yes, but it must not run/work much.
My two cents.
Best Igor