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16s BMS advise
#1
I am looking for a BMS to run a 16s lithium (~3.7 volt cells) pack

Ideally it could remote trip a breaker/control a relay. But one that breaks the current internally would do if rated at something like 40 amps continuous.

Adjustable voltage cut off would be nice, but not necessary.

This is just temporary to get cell testing done. I haven't managed to find a 16s balance/charger one like you can find for smaller packs.

So I suppose price and reliability would be the highest concern. Any recommendations for a cheap 16s BMS?
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#2
tiny bms https://www.energusps.com/shop/product/t...0a-750a-36 reasonably priced has relay control, external current measurement adjustable voltage cut off, Just waiting for the CT for mine.Total cost for the bms+ wiring+CT +usb cable adapter is less than $300 the seller is on ebay in bc, Canada
later floyd
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#3
Thank you
I was not familiar with energus

I didn't see current transducers on their site. Where/what did you source?
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#4
I bought my ct from Ebay
https://www.ebay.com/itm/LEM-Current-sen...Swjfhcir8H

the CT is on the second page of products
https://www.energusps.com/shop/product/l...-31?page=2

Later floyd
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#5
Another one is Chargery 16T -  https://www.ebay.com/itm/19283853365
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#6
Thanks!

Is this version the same thing, just with the display integrated into the main unit?

https://www.ebay.com/itm/Smart-300A-2S-1...3273995213


I should have specified I was looking for cheap as the highest priority. I need some time to get the factory BMS working and communicating and verify function. I plan to repurpose modules from BMW 740e and hopefully the i3 CAN messaging is similar enough that with some work, I can get something like simpbms working. Or give up and go with a batrium...

Either way something like this might fill in for me while figuring out the rest.
I will have 6 16s modules, so that's 6 separate BMS's. So I would order 5 cheapos to run while testing the 6th module.
https://www.ebay.com/itm/Smart-300A-2S-1...3273995213
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#7
(05-29-2020, 12:50 AM)400bird Wrote: Thanks!

Is this version the same thing, just with the display integrated into the main unit?
https://www.ebay.com/itm/Smart-300A-2S-1...3273995213
I think its the same family but cheaper than mine - e.g. mine is 16TPro and this is 16T?.   Mine came with a shunt and display separated from the BMS box - but your link is cheaper! Here's a pic of what I got (+ sense leads I've already soldered into place) but I don't plan to use the shunt  -  so I like your link better Smile


I have Batrium as my main house BMS - this is my first attempt to use Chargery - e.g. I'm testing it for a 18650 battery for my APC UPS 3000.   There are some good youtubes on it etc and its been around for a while - so I think its the 'real thing'.  

(05-29-2020, 12:50 AM)400bird Wrote: Either way something like this might fill in for me while figuring out the rest.
I will have 6 16s modules, so that's 6 separate BMS's. 
I'm not sure what you need - e.g. are all 6 modules seperate or do they form a battery bank or ?
If its 1 battery bank (of 6 x 16s modules) , you can parallel the balance leads of all 6 modules into just 1 BMS.    This particular BMS puts out 12v for a relay control of the load - so you can by a big relay to cut-off the entire battery.    This BMS does a respectable 1.2a per cell - and it would balance 6 modules in parallel if you weren't in a hurry.
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#8
the smart300a (109 dollars) is the chargery bms16, from the ebay link it comes with the 300 amp shunt. It has all the parts needed except the contactors/relays, on mine I just use the cheap 4 dollar 30a automotive relays.

Since you have 6x separate 16s packs, all you need is one bms and parallel all the packs together, connecting all the balance connecters to each other so the battery will equalize. As long as the batteries are the same voltage when you connect them together it will work.

Chargery is a very good bms, I been using since last year, fully programmable. Will easily handle your 16s pack.
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#9
Yes 6 separate 16s packs. From an EV, just ready to drop in and wire up a BMS


Really? Parallel all the balance leads together and run 1 BMS?

That sounds great!
I had considered this but, my concern was that in the case of a cell failure, I might end up passing current through the balance leads from one module to another. The OE balance leads are tiny and would burn up easily. Then the BMS wouldn't be able to detect the fault and open the contactor/breaker.
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#10
(05-30-2020, 01:00 AM)400bird Wrote: Yes 6 separate 16s packs. From an EV, just ready to drop in and wire up a BMS


Really? Parallel all the balance leads together and run 1 BMS?

That sounds great!
I had considered this but, my concern was that in the case of a cell failure, I might end up passing current through the balance leads from one module to another. The OE balance leads are tiny and would burn up easily. Then the BMS wouldn't be able to detect the fault and open the contactor/breaker.
This topic has come up a few times and (surprisingly to me) a key observation by senior folks is that the 'raw current' will flow thru the charge/discharge wires and not thru the parallel/balance leads except under extreme conditions.  So what are those extreme conditions and and how can you handle them...  that depends somewhat on the type of cells you have.     For example,

- one 'extreme condition' is that the balance leads short-out - this can be handled by using good wire/practices.
- another is you parallel batteries that are wildly different SOC from each other - obviously they should be put in a similar state of charge/voltage before hooking balance leads together.
- another is 1 of the batteries burns up from external fire?  - then temp sensors may be the answer.
etc etc...

You say -  "... in the case of a cell failure, I might end up passing current through the balance leads..".  I'm not sure what kind of cell failure you're thinking of.    An 18650 cell might fail and become a dead short - but fuse wires handle that.   A cell might start self-discharging... but this will be gradual and will pull the others down and the BMS will detect it.   

Can you share the exact cells in your EV batteries?   And maybe more about what you're thinking when you say 'cell failure'?    
There are indeed things to consider - but perhaps it can mitigated with techniques you should do anyway.   

And maybe @Daromer will comment here Smile
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