ANT BMS. Final answer? Yes, final answer.

[Dzl]

I'm only barely informed, but If there is actually Coulomb counting (which I'm still not convinced there is), I'm pretty sure it would need awareness of current in and current out, if it can't see all current, it can't accurately count coulombs. Right?

BMS like devices that provide cell monitoring and balancing but don't offer disconnect (FET or otherwise)?

This sounds a lot more like an active balancer than a BMS (if all you want is a device to monitor cell voltages and balance the pack). And an active balancer would be a much more powerful balancer than most FET based BMS which often have very low balance current like 35-150 mA. I believe ISDT is the brand that a lot of people here buy, I have no experience.

In my view, if a device cannot act autonomously to protect or manage the battery, it really shouldn't be (and generally isn't) called a BMS. I think it can be part of a broader battery management system, but not a BMS in and of itself.

But I don't think its a good idea to forego a BMS unless you are experienced enough to really understand what you are doing, and will actively and consistently manage/monitor your system, or your system is for learning purposes and you don't mind potentially screwing up.


Edit: There is at least one person here using a BMS the way you are wondering about (balance only--no protection or management), but this person knows the risks, is confident they know what they are doing, and actively monitors their system. I'm not sure what the advantage of this approach is over an active balancer (which would be cheaper and have higher balancing current) or using the BMS for protection and management as it is intended.

 

[apctjb]

This sounds a lot more like an active balancer than a BMS (if all you want is a device to monitor cell voltages and balance the pack). And an active balancer would be a much more powerful balancer than most FET based BMS which often have very low balance current like 35-150 mA. I believe ISDT is the brand that a lot of people here buy, I have no experience.

In my view, if a device cannot act autonomously to protect or manage the battery, it really shouldn't be (and generally isn't) called a BMS. I think it can be part of a broader battery management system, but not a BMS in and of itself.

But I don't think its a good idea to forego a BMS unless you are experienced enough to really understand what you are doing, and will actively and consistently manage/monitor your system, or your system is for learning purposes and you don't mind potentially screwing up.

 

[apctjb]

Appreciate the response.

In my case I will not be around to baby the system which is for a vacation home that I will be absent from 6 months of the year . When I am gone I want to be able to monitor the system and access security cameras via internet. The sole source of charge and discharge current in my system is an all in one inverter which has setpoints which can be set conservatively to protect the battery from under or over charge situations.

The question I struggle with is which is more likely to occur; a failure of the BMS relays or FETS which takes down my security cameras and ability to monitor my home remotely, or a failure of the the all in one inverter that results in an over or under charge situation.

I have zero experience with BMS devices so no idea of how often they fail.

How reliable are these things?

 

[Steve_S]

The question I struggle with is which is more likely to occur; a failure of the BMS relays or FETS

If you built the system properly and used good judgment by using good quality parts/components, you should not have to worry. That being said, if you are frugal in your thinking and underbuilt your system then you could have potential issues. For example, if you are using FET based BMS, and your pulling up to 150A but are only using a 150A rated BMS, it likely will not survive as you are taking it to the edge of the spec, whereas you should be using a 190A rated BMS. Relays/Contactors are rated for thousands of hours of continuous use and again they should have a 25% margin above what is actually going to be pulled. So again, if you are going to pull 150A you should be using 200A Contactors.

Case Point to consider.
If you have a 4,000W Low-Frequency Inverter, that means it could support up to 12,000 Watts for surge. Normally you would work with the 4,000 Watt figure and derive the Max Amps capacity that could be pulled. 4000W ÷ 24V = 166A but at 12,000W that's 500A for max surge.

Longterm operation: You say that for 6 months you re not on-location and want your monitoring. There is no issue with doing that whatsoever, these do not need babysitting services to continue operations. Leaving the SCC & Inverter on (in power-save mode), it will still run your fridge and whatever else that needs to run BUT I would shut down anything that is not essential at the breaker panel, while you are in "holiday mode". LFP does not need watering or maintenance as such, once you have all your settings doe, it is pretty much hands-off.

I depend on my solar system, it is my power source, no grid lines near me and it has to live through -35C/-31F to +35C/95F and humidity levels can be nuts at times, and because I have to depend on it and it must be bulletproof I use a BMS with Contactors and have spare contactors on hand for "just in case"... closest town is 1 hour away, electrical parts 2 hours away, so I have backups for everything due to my remoteness, 3 ways to generate power, 3 ways to get water from my deep well, 3 ways to heat (2 requiring no energy at all).

 

[apctjb]

If you built the system properly and used good judgment by using good quality parts/components, you should not have to worry. That being said, if you are frugal in your thinking and underbuilt your system then you could have potential issues.

Agree completely! My challenge at this stage is knowing which are the good quality parts/components and what are realistic design criteria vs those that are at the far reaches of probability. I want a reliable system, and also one that balances reliability with complexity and part count. I do believe that less is sometimes more in system design.

Also good on you for living off grid! I look forward to doing the same (at least half the year!)

 

[Steve_S]

Agree completely! My challenge at this stage is knowing which are the good quality parts/components and what are realistic design criteria vs those that are at the far reaches of probability. I want a reliable system, and also one that balances reliability with complexity and part count. I do believe that less is sometimes more in system design.

Also good on you for living off grid! I look forward to doing the same (at least half the year!)

Unintentional semi-hijack bt here to share the info.

As I stated, I use Contactors, and after having spent "way too much" on testing SSR's and a wide variety of assorted relays & contactors I came down to applying KISS and no longer overthinking it. I use TE/Kilovac EV#00AANA Contactors & also Dongya DHV#00AAANH Contactors. These two are nearly identical in quality, function, capability and they are Energy Savers as well, so very low draw to keep contactor closed. TBH the Dongyas new are 1/4 the price of TE/Kilovac or the Gigavac Contactors and are equal IMO. Now I am running Common-Port configuration with a Chargery BMS , therefore it has allowed me to use ONE Contactor instead of two by utilizing a 2 Channel 12-Volt OptoCoupler which accepts both relay signals and acts on the one active relay.

If you search for recent posts by me (today in fact) I have posted a fair bit of detail on this in other threads. I made recommendations to Emma Chen of Dongya to place an advert into the Commercial Sales sub-forum related to the DHV Series of Contactors wich are Bi-Directional and have the Energy Saver module built-in. NOTE the DH series are Uni-Directional, DHV is Bi-directional.

--- End hijack, further discussion should be in another thread or PM to keep this thread intact and on focus. PM = slow response when I get to it, usually very weird hours.

Hope that helps,
Steve

 

[Ojeysky]

50A at 48V is 2,400W.

It does say 50A:
View attachment 13438

But considering it's common port, I bet it's incorrect. I would test it.

Hi Will, did you get to test out charging above 50A via the ANT BMS? My MPP does up to 80A and I want to know if it's fine to have that charge when occasionally when the sunlight is at its peak

 

[Dzl]

Hi Will, did you get to test out charging above 50A via the ANT BMS? My MPP does up to 80A and I want to know if it's fine to have that charge when occasionally when the sunlight is at its peak

Considering that the specs say 50A, and that if anything, Chinese BMS manufacturers often overstate the specs/limits, I would not push the Ant BMS beyond its 50A charge limit.

 

[Sunny Days]

My ANT bms stops at 50 Amps almost exactly! It disconnects and re connects in about 4 seconds, amps ramp ut to 50 then it disconnects again and repeats over and over...

Wich is a PAIN when used with a Mpp lv2424 al in one! I have about 80 amps from solar and can only use 50 lol! This mpp only has a MAX charge current setting and its Solar + grid total! So if you want Solar to charge at 40 amps that means you only can use 10 amps from grid (if you need grid charging when overcast)

 

[Sunny Days]

Edit deleted

 

[Dzl]

Wich is a PAIN when used with a Mpp lv2424 al in one! I have about 80 amps from solar and can only use 50 lol! This mpp only has a MAX charge current setting and its Solar + grid total! So if you want Solar to charge at 40 amps that means you only can use 10 amps from grid (if you need grid charging when overcast)

Isn't this actually a good thing in your case?

If you can set total charge current to say 45A total that would allow you to prevent the BMS from tripping while allowing the MPP to manage what percent of that 45A is coming from grid and coming from solar.

 

[Ojeysky]

Considering that the specs say 50A, and that if anything, Chinese BMS manufacturers often overstate the specs/limits, I would not push the Ant BMS beyond its 50A charge limit.

I reached the seller of the BMS who claims the BMS can accept charging above 50A. I have adjusted my BMS settings to 60A for a test.

My ANT bms stops at 50 Amps almost exactly! It disconnects and re connects in about 4 seconds, amps ramp ut to 50 then it disconnects again and repeats over and over...

Wich is a PAIN when used with a Mpp lv2424 al in one! I have about 80 amps from solar and can only use 50 lol! This mpp only has a MAX charge current setting and its Solar + grid total! So if you want Solar to charge at 40 amps that means you only can use 10 amps from grid (if you need grid charging when overcast)

Using the BMS app, you can increase the overcurrent protection of the BMS from 50A to a higher number.

 

[Dzl]

I reached the seller of the BMS who claims the BMS can accept charging above 50A. I have adjusted my BMS settings to 60A for a test.

If this were true, why would they state 50A in red in the spec sheet?

For reference, who is the seller you contacted?

It is your decision whether to push it or not, I'm curious to see what your experiment reveals (but since I believe the damage is gradual and over time it may be hard to draw any conclusions) bear in mind that:
1. you are choosing to trust a reseller's opinion over the limit explicitly stated in the manufacturer specifications
2. Chinese products tend to overstate their capabilities/limits, not understate them.

 

[Steve_S]

All BMS' will flip Charge or Discharge ON/Off when triggered, this is a normal cycle, the flipping is to determine if there is still charge coming or descharge being demanded. It's a constant cycling that occurs and is generally not a good thing. The SCC/Charger & Inverter should be cutting off Discharge & Charge prior to the BMS forcing it off (which is supposed to be a Last Resort safety mechanism).

IF you have an Infrared Heat Sensor type monitor, WATCH the BS when it's at 50A and if you push it above Spec especially. FETS don't generally leave any elbow room so I would be Very Leary of doing so, without actually being perched right there, watching & monitoring, espeially with the heat on the BMS.

This is one major pitfall of using FET based BMS' unless you go high end is the Charge Input Limit. Especially whn we have 200AH+ cells that CAN take 1C Charge Rate. More Amps pushed at the battery pack the faster it will charge, the bigger the bank the, more amps it wil need collectively but then the more amps each pack within the bank has to be handled as well. Assume a Bank of 4 packs charging, as they fill and cutoff, the "Last Pack Standing" has to be able to handle the full charge capacity potential of the system,

 

[Ojeysky]

If this were true, why would they state 50A in red in the spec sheet?

For reference, who is the seller you contacted?

It is your decision whether to push it or not, I'm curious to see what your experiment reveals (but since I believe the damage is gradual and over time it may be hard to draw any conclusions) bear in mind that:
1. you are choosing to trust a reseller's opinion over the limit explicitly stated in the manufacturer specifications
2. Chinese products tend to overstate their capabilities/limits, not understate them.

The IC GOGOGO store on AliExpress

 

[Sunny Days]

Personally i Wouldnt go over 50 AMPS! In fact i no longer charge at 50 amps since that is its limit, wich cant be trusted to be able of handling constantly 50 amps.

 

[Ojeysky]

Personally i Wouldnt go over 50 AMPS! In fact i no longer charge at 50 amps since that is its limit, wich cant be trusted to be able of handling constantly 50 amps.

It actually handled it fine, maybe there will be a long term implication on the BMS though not what I will do often

 

[Dzl]

It actually handled it fine, maybe there will be a long term implication on the BMS though not what I will do often

From the tiny bit I've read and recall, that is what I would expect (slow failure over time) if you are just moderately exceeding the rated current. Maybe one of the forum members better versed in electronics and FETs can either confirm or correct me here.

 

[Deleted member 9967]

I read the entire thread and have an observation.

I know of someone that has some batteries in their house in a back room where extremes in temperature are not an issue.
What they did was charge all of the Lifepo batteries up to about 3.65 each.
Then they let them sit in parallel mode for three days.
After this they set them up in series mode and used them daily. No bms, no protections, nothing.

Just used them at night. Charged them in the day.
When the charged sensed they were full, it turned off.
He "resets" the batteries every six months by fully charging them and then letting them sit in parallel again for three days.

He has done this for at least five years now and has had no problems.
Is he lucky?
Or is this viable for most of us?

Thanks guys.
Oh and to refer to an earlier debate here. I choose redheads because I am one LOLOL ?

 

[upnorthandpersonal]

If you know what you're doing and know what loads are on your system and have intricate knowledge of the entire system, you can do that and not run a BMS. This is especially the case if you have very low C rates and know that you won't run into conditions that a BMS is designed to handle such as temperature issues, over/under voltages, etc. Personally, I always use a BMS - not worth the risk not to. If something goes wrong, I want a last line of defense.

Oh and to refer to an earlier debate here. I choose redheads because I am one