Is this wise? Making a battery without BMS?

[Clarson]

I stumbled across this video:

he is using a shunt instead of a bms, is this a wise decision? Can a shunt be used to substitute a bms if you balance the cells?

 

[Quattrohead]

No because you don't know what each individual cell is doing.
It's okay for a quick test if you are there the babysit them but for a long time use, absolutely not.

 

[kommando]

Its wise until it goes bang.

 

[Steve_S]

NO it is extremely FOOLISH to build a Lithium Based battery without a BMS !
The BMS not only manages the cells & balances them IF IT HAS BALANCING CAPABILITIES.
It's also the Emergency Brakes for Over/Under voltage conditions which can harm the cells that could result in worse failures.

Passive Balancing by a BMS only wastes Voltage from Hi Volt cells and this only works with perfectly matched & batched cells under and lower capacity cells typically below 100AH.

Active Balancing by a BMS will move voltage from High Cells to Low Cells when conditions require it, which keeps cells balanced internally within the pack.

A BMS also controls the amount of Amperage going out & coming into a battery. For example a 100A BMS allows for 100A discharge and allows for 50A charge (LFP has 1C Rate discharge & 0.5C charge rate).

 

[Alkaline]

I love the title of the Video "They Fail" the only fail is the builder! No bms and no balance, this is the problem with diy everyone thinks they are an expert when in reality they are a n00b.

 

[upnorthandpersonal]

he is using a shunt instead of a bms, is this a wise decision?

Heck no. Shunt doesn't know anything about cell voltages.

 

[upnorthandpersonal]

He claims EV battery packs don't have balancers. He's never looked into this, because I can tell you: they do. Which is one of the reasons Tesla tells you to charge their LFP models to 100% so they can balance them.

 

[chopper]

NO it is extremely FOOLISH to build a Lithium Based battery without a BMS !
The BMS not only manages the cells & balances them IF IT HAS BALANCING CAPABILITIES.
It's also the Emergency Brakes for Over/Under voltage conditions which can harm the cells that could result in worse failures.

Passive Balancing by a BMS only wastes Voltage from Hi Volt cells and this only works with perfectly matched & batched cells under and lower capacity cells typically below 100AH.

Active Balancing by a BMS will move voltage from High Cells to Low Cells when conditions require it, which keeps cells balanced internally within the pack.

A BMS also controls the amount of Amperage going out & coming into a battery. For example a 100A BMS allows for 100A discharge and allows for 50A charge (LFP has 1C Rate discharge & 0.5C charge rate).

I want to thank you for all the information you have provided on this forum. I have been saving to my reading list for future reference the conversations pertaining to my planned application of LA to Lithium
Now a question if you would, I have a Schneider XW6848-X (as I understand does not control charge voltage precisely enough for lithium) and 2 600-80 charge controllers. This system is for stand by only the solar array 11kw is shared with a grid tied system via a transfer switch.
Will a BMS cover the deficiencies of the XW6848X and if so which BMS would you suggest?

I am sorry to read of your health issues and truly hope a miracle comes your way.
Thanks
Wayne Cook

 

[timselectric]

Old school diy EV conversion batteries were built without BMS's. Mainly because they were hard to find and very expensive.
The trick was that they bottom balanced the pack and limited the charging voltage. (Which limited the capacity)
It worked, but they knew that there was no protection system.
Now, it's easy to get any BMS configuration for a fair price. So, it's not recommended to take that risk.
A BMS gives you the protection system. And increases the usefulness of your battery.

 

[Steve_S]

The Schneiders can use a "user" profile which will handle LFP just fine. Remember that LFP is the "closest cousin" to Lead Acid with a similar profile, except LFP does NOT use Equalization like lead does. It's simply 2 stage charging CV-CC & CV-VC.

Have a look at this resource I made a while back.
Luyuan Tech Basic Lifepo4 Guide V1.0A
Then grab this chart & the update one...
General LiFePO4 (LFP) Voltage to SOC charts/tables 12/24/48V

For BMS, I am a JKBMS user and happily recommend them. There are the Standard Versions that support up to 200A, Active Balancing with Bluetooth, RS485/Can connections. They are just releasing the new JKBMS with Inverter Interface, these are more advanced and have many extra features, They are more costly of course and the firmware is getting ready. These have the advantage that there is also PC Software, their Firmware can be flash upgraded and still have BlueTooth app as well.

I can recommend a Very Well Known Good Vendor who can supply your cells testers, BMS' etc...
BTW: It is cheaper to get everything from 1 vendor if possible, because they can include the small bits into the main packaging, saves on the "per box min fee + Weight" that adds to S&H really fast.

Note to get a proper quote with shipping etc, you must open a chat/messenger session. Be clear & concise about what you need and even if it's not listed on their site, ask...

Shenzhen Luyuan Technology Co., Ltd. - Lifepo4 battery, LTO battery

Shenzhen Luyuan Technology Co., Ltd., Experts in Manufacturing and Exporting Lifepo4 battery, LTO battery and 612 more Products.

szluyuan.en.alibaba.com

As a side note: I have several packs in a bank now using the older JK, I am replacing my entire fleet with the new Inverter Models and adding 2 more 280AH packs with these same BMS'.

Hope it helps, Good Luck

 

[400bird]

I have a Schneider XW6848-X (as I understand does not control charge voltage precisely enough for lithium)

What is the -x ? I've never heard of that model and neither has Google.
Whoever told you the voltage control was just as informed as the YouTuber above. It's nonsense, the XW6848 works well with lithium, plenty of us here are using it.

Will a BMS cover the deficiencies of the XW6848X and if so which BMS would you suggest?

You need a BMS no matter what inverter you use. Even one with imagined deficiencies ?

 

[chopper]

What is the -x ? I've never heard of that model and neither has Google.
Whoever told you the voltage control was just as informed as the YouTuber above. It's nonsense, the XW6848 works well with lithium, plenty of us here are using it.


You need a BMS no matter what inverter you use. Even one with imagined deficiencies ?

Sorry my mistake I inserted the X instead of a + no way to make a large + to match the numerals the 6848+ was produced after the XW6848 was discontinued and now the XW6848 Pro is current production.
I am really surprised at your sarcasm as both timselectric and Steve_S are some of the most knowledgeable and helpful people on this forum.

My information concerning voltage control comes from very good sources on the NAZsolar panel forum from people who work with Schneider equipment. Maybe I am misunderstanding the issue of the voltage problem being in the communication capabilities of the discontinued XW's.

If it works for you it's great.

wayne

 

[400bird]

Sorry my mistake I inserted the X instead of a + no way to make a large + to match the numerals the 6848+ was produced after the XW6848 was discontinued and now the XW6848 Pro is current production.

Understood, I wasn't sure if the X was an overseas model or maybe just something I've never heard of.

I am really surprised at your sarcasm as both timselectric and Steve_S are some of the most knowledgeable and helpful people on this forum.

Not sure what your getting at, they both told you to use a BMS and neither said the XW wouldn't work with lithium.

My information concerning voltage control comes from very good sources on the NAZsolar panel forum from people who work with Schneider equipment.

What did they say about going without BMS? Based on the fact that you came here to ask, either you didn't like the answer or they shouldn't be trusted. Maybe both, maybe neither.

Maybe I am misunderstanding the issue of the voltage problem being in the communication capabilities of the discontinued XW's.

Some people preach BMS communication and some don't care. There are benefits to having comms, but in my opinion it isn't the a vital feature. I've got comms, but still use voltage based controls.

If it works for you it's great.

There's plenty of experience here to say that it does work well, not just me.

 

[chopper]

Understood, I wasn't sure if the X was an overseas model or maybe just something I've never heard of.

Not sure what your getting at, they both told you to use a BMS and neither said the XW wouldn't work with lithium.

What did they say about going without BMS? Based on the fact that you came here to ask, either you didn't like the answer or they shouldn't be trusted. Maybe both, maybe neither.

Some people preach BMS communication and some don't care. There are benefits to having comms, but in my opinion it isn't the a vital feature. I've got comms, but still use voltage based controls.

There's plenty of experience here to say that it does work well, not just me.

Thanks for your reply as it clears up a lot. I did not have any intensions of no BMS it's just what kind and which balancing system and will it work well with my system.

There was no recommendation to run without a BMS however there is strong recommendations to replace the XW+ and since mine is for backup only I can't justify that, so you are correct I didn't like that. These recommendations were in discussions with other members none direct with me I really don't know enough about the subject to ask inteligent questions.

I very well may be incorrect and hope so, it has been my understanding (assumption) that without the control of the Insight Home you have to stay away from upper and lower knees and forfeit a lot of capacity in order to prevent shut down or damage to batteries. Would appreciate if you could advise or elaborate on this and finally could you tell what BMS and balancer you use.

To clear some things up I am lost when it comes to the bms comms does the BMS control the XW charging process or the charge controllers (600-80) or they actually control the whole charging process within itself, hopefully the latter
Thanks for responding as it has opened up some possibilities.

Wayne

 

[upnorthandpersonal]

It's been ages since I did anything with XW+ and their charge controllers, but doesn't it allow to set the cut-off voltage at 48V at the low end, and 57V at the high end? Even without any communication, those are perfectly fine margins. There isn't much energy below 3.0V per cell and you don't really need to go above 3.5V for the same reason. Put a JK BMS (has active balancing, don't go for the comms version) on the battery and it should be good to go.

Am I missing something?

 

[chopper]

It's been ages since I did anything with XW+ and their charge controllers, but doesn't it allow to set the cut-off voltage at 48V at the low end, and 57V at the high end? Even without any communication, those are perfectly fine margins. There isn't much energy below 3.0V per cell and you don't really need to go above 3.5V for the same reason. Put a JK BMS (has active balancing, don't go for the comms version) on the battery and it should be good to go.

Am I missing something?

You are not missing anything other than my lack of experience and understanding of all the communication talk.

Your answer is what I am looking for.

Thanks Wayne