Bms for 16s

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Chapelier

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Hi

New here and pretty new to the subject too so by all means treat me as an idiot ?

I have 5 bmw i8 packs . Each pack is 16s . I have tested them and each cell in the pack is at 4v so each pack is 64v

Im planning on joining them in parallel for 16s5p

I was willing to buy a batrium but they have said watchmon 4 isnt suitable and their other option only goes to 15s

Im planning to use this for solar storage to charge my electric car in an effort to be 100% environmental in my driving.

Ive spent the last week looking at various bms , cheap ones , expensive ones etc and Im totally lost.

Im assuming the cheapest would be to have Daly or something like that for each pack ?

Im struggling to make a choice as my knowledge is probably not good enough yet. What size bms ? 100a 150a . Im assuming I want a bms where I can choose the minimum cell voltage and maximum?

Am i on the right track or completely out ?

Which Daly might work for this ?
I have also come across Chargery BMS16T

Would that work for me ?
 

OffGridInTheCity

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>I was willing to buy a batrium but they have said watchmon 4 isnt suitable and their other option only goes to 15s
Not sure who 'they said' is - but Batrium will work very well. I use Batrium and I use Watchmon 4 with 84 packs (84 longmons). Batrium wise you could do....
-Watchmon 4 + 16 longmons - note that the longmons don't have to be on the battery itself, you just have to connect + / - from each longmon to each cell. Onereason they are 'typically' place physically near thecells is that they have temp sensors - so can monitor the temp of each cell and for convienence ... but its not functionally necessary.
- Watchmon 5 - this has 16 'longmons' built in - so you just run wires to the cells from the central unit. This is a little cheaper and is less balance power - but it will definately work for your application.

VERY CHEAP SIDE - you could consider something like this -https://www.ebay.com/itm/Ant-BMS-7S-to-16S-17S-to-24S-Lithium-Battery-Protection-Board-Smart-Bluetooth/293651262506?hash=item445efaac2a:g:CB8AAOSwMste~JzP - but I've had mixed results. For example, I made a simple mistake and blew one up. Another burned up an internal resistor for some reason - and the others worked. But they are cheap compared to Batrium and others :)

>What size bms ? 100a 150a . Im assuming I want a bms where I can choose the minimum cell voltage and maximum?
In Batrium you can. Amps - Batrium itself doesn't care about this but tillwill trigger (on events you chose) to send a current to anexternal shunt-trip- which you need to buy. In many our or cases - we use used ABB SACE for higher amps. In my case, I needed 400amp. The amps are whatever you plan to draw from the battery bank... you only need a shunt-trip to handle your largest load. Here's an example of a used ABB SACE -https://www.ebay.com/itm/ABB-SACE-S5-400A-600V-Circuit-Breaker-w-SACE-PR211-USED/202773047200?hash=item2f363727a0:g:wHMAAOSwq7ldcpoh - but you need to pay attention the 'trip voltage' - a lot of use 24vdc models.
 

Cheap 4-life

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I use chargery 16s for my 16s Chevy volt packs. Its working well.
 

OffGridInTheCity

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Cheap4-life said:
I use chargery 16s for my 16s Chevy volt packs. Its working well.
On the affordable side - I have one operating as well - but another burnt up and a 3rd blew up when I somehow touched the temp sensor to a cell in the pack. So I've had mixed results; however,I don't see any for sale right now soI didn't mention it above. I agree it's an alternative and Ilike them - but they can be finicky.
 

Chapelier

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Thanks everyone. Im blown away by the response.

Floydr a couple there I havent looked at so will study them.

Offgridinthecity: I contacted batrium by email and they werent overly helpful. It was actually them that sent me here for advice.

Watchmon 5 Only seems to go to a maximum of 15s which is why they said that wouldnt work but they didnt elaborate on why watchmon 4 wasnt suitable so it is probably because I cant attach them to the cells as you explained. I must admit it was my first choice as once I have done my learning on these batteries Ill probably go on to more expensive ones. For the moment while learning I just want to power my charging of the car but eventually Id love to do the whole house.
You mentioned 16 longmons , I have 5 packs of 16s so would I just buy 80 longmons to monitor the 16 cells in each pack ?

Cheapforlife: thats good to know , I have one in my AliExpress basket as a possibility. Do you have one for each pack ?

Again thanks for all the help. I appreciate helping newbies can be a thankless task sometimes!!

Picture of 1 of 5 batteries

image_wooysn.jpg
 

daromer

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The reason they state longmons isnt the best choice is since you have a shared loom. If you can put wires to each battery without sharing the wiring with each longmon you can still use them and yes unless you plan on hooking each of them up together you need 80 longmons. So you basically have to scrap current wiring and put out 2 wires for each longmon instead of what you have today with 1 wire for each cell. You need 2 since each longmon connect there.
they should also sit fairly close to the cell so you should not extend the wiring 1 meter and such. Thats why they arent the best option.

Beware that you also need inverter/charger that can tolerate that voltage. 16s Liion is the high range and not all cheap systems like it.

Btw DIY BMS also have somewhat the option like Batrium have if the cost of going 80 mons is an issue.

I use Batrium btw but have tested many others. Currently im working with a new system with DIY Bms.
 

OffGridInTheCity

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If you join the cells in parallel "Im planning on joining them in parallel for 16s5p..." then you onlyneed 16 longmons (for Batrium). As @Daromer pointed out - you do have to have a + and - for each longmon to each set of parallel group ofcells... but if you're going to parallel the cells then take this into account and wire it so you have tap wires coming off forlongmon use. And will have to be watchmon 4.

I didn't realize WM5 is only 15 cells in series - weird as I saw it was more than 14 (in youtubes) and just assumed it would do 16 for LifePO4. But yep, its only 10-15 cells per description here -https://www.batrium.com/collections/centralise-supervisor/products/watchmon5-exp (My bad for referencing for 16s). I wonder why they limited it to 15... and not 16 so LifePO4 (48v nominal)could be an alternative use?

TMI... :) Another thing to consider in relation to BMS is how you like to monitor things. It ranges from Android appsto internet/PCsto custom code. For me, I like to see stats/details of what's happening without custom code.But others just want it to work quietly and not bother them. I choose Batrium exactly because its internet (wifi) and PC (windows) and has excess detail on all aspect. Don't mean to push Batrium... you may be the 'don't bother me type' and in that case somethingthat 'just does the job' may be all you need.
 

daromer

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They didnt limit it. The Common size is 14 and they use built in chip that is 10-15. Thats the Common size chip you find for balancing ;) just look at Texas. Next step is alot higher
 

Chapelier

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OffGridInTheCity said:
If you join the cells in parallel "Im planning on joining them in parallel for 16s5p..." then you onlyneed 16 longmons (for Batrium). As @Daromer pointed out - you do have to have a + and - for each longmon to each set of parallel group ofcells... but if you're going to parallel the cells then take this into account and wire it so you have tap wires coming off forlongmon use. And will have to be watchmon 4.

I didn't realize WM5 is only 15 cells in series - weird as I saw it was more than 14 (in youtubes) and just assumed it would do 16 for LifePO4. But yep, its only 10-15 cells per description here -https://www.batrium.com/collections/centralise-supervisor/products/watchmon5-exp (My bad for referencing for 16s). I wonder why they limited it to 15... and not 16 so LifePO4 (48v nominal)could be an alternative use?

TMI... :) Another thing to consider in relation to BMS is how you like to monitor things. It ranges from Android appsto internet/PCsto custom code. For me, I like to see stats/details of what's happening without custom code.But others just want it to work quietly and not bother them. I choose Batrium exactly because its internet (wifi) and PC (windows) and has excess detail on all aspect. Don't mean to push Batrium... you may be the 'don't bother me type' and in that case somethingthat 'just does the job' may be all you need.


Ok so now Im a little confused. Each pack has 16 cells making up 64v I was planning on paralleling the whole pack lets say For simplicity 64v 20ah with the other 4 packs so it would be - 64v 100ah battery. Im not changing any wiring in each pack. I had assumed I would just parallel one pack to the next and the next and I would need to monitor each cell so 16 cells x 5 = 80 longmons . Maybe (very possibly) Im misunderstanding something as I saw someone else say 16 but I dont see how if you group cells together in parallel and monitor them with 1 longmon how would you guarantee that all the cells stayed at exactly the same voltage ?


daromer said:
The reason they state longmons isnt the best choice is since you have a shared loom. If you can put wires to each battery without sharing the wiring with each longmon you can still use them and yes unless you plan on hooking each of them up together you need 80 longmons. So you basically have to scrap current wiring and put out 2 wires for each longmon instead of what you have today with 1 wire for each cell. You need 2 since each longmon connect there.
they should also sit fairly close to the cell so you should not extend the wiring 1 meter and such. Thats why they arent the best option.

Beware that you also need inverter/charger that can tolerate that voltage. 16s Liion is the high range and not all cheap systems like it.

Btw DIY BMS also have somewhat the option like Batrium have if the cost of going 80 mons is an issue.

I use Batrium btw but have tested many others. Currently im working with a new system with DIY Bms.

Thanks for the reply daromer.

I was planning on using Victron which I think will work.
I had a quick look at diybms bit my head started to hurt :) Ill take another look tonight but I can afford the batrium if need be. 80 longmons or 16 ? :)
 

daromer

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You need 80 mons if you dont plan to connect each pack together. but thats very small packs per longmon... 1 longmon can easily handle 100Ah pack but you need to rewire. Neither less you need to rewire to use a longmon on it since they should not be used with shared wiring

Shared wiring is when 2 mons share the same wire to one battery
+ for one mon and negative for the other...

Dont forget that with the batrium you need the shunt and a breaker with trip function as well for it to become a complete bms. Advantage is that it can talk to some victron gear.
 

OffGridInTheCity

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>Ok so now Im a little confused. Each pack has 16 cells making up 64v I was planning on paralleling the whole pack
I see. When you wrote 16s5p... this implied to me that you were planning to parallel the16 cells of each battery. Instead, it sounds like you plan to have 5 batteries of 16s1p in parallel.

Again, @Daromer had it right then as5 batteries of16s1p is 5 x 16 = 80 longmons. At 1 longmon per cell, Batrium is waymore powerful than you need - but that's not a bad thing functionally, just very expensive -https://www.batrium.com/collections/cell-monitor/products/longmon-100x:)

@DavidPoz did a customchevy batttery bank in 14s1p * 5? (several)'batteries in parallel'.Each 14s1p had it's own (cheaper) BMS + circuit breaker and they paralleled to an overall bus.He used the phone / android BMS path. If you go to 15:26 on this youtube you can see the end result on his phone -https://youtu.be/XGLs9-nIOjw - followed by a recap showing the gang of circuit breakers and overall + / - If you look this at this youtube and a little earlier youtubes you can see the overall details of design. It might be inspiring for your situation.
 

daromer

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I have paralleled my LiFepo4 packs to so that i dont had to have several 100s of longmons. But you need to think ahead when doing it.
 

Chapelier

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Again, @Daromer had it right then as 5 batteries of 16s1p is 5 x 16 = 80 longmons. At 1 longmon per cell, Batrium is way more powerful than you need - but that's not a bad thing functionally, just very expensive - https://www.batrium.com/collections/cell...ngmon-100x :)

@DavidPoz did a custom chevy batttery bank in 14s1p * 5? (several) 'batteries in parallel'. Each 14s1p had it's own (cheaper) BMS + circuit breaker and they paralleled to an overall bus. He used the phone / android BMS path. If you go to 15:26 on this youtube you can see the end result on his phone -
- followed by a recap showing the gang of circuit breakers and overall + / - If you look this at this youtube and a little earlier youtubes you can see the overall details of design. It might be inspiring for your situation.


O.K so I think yes . I guess that is a major lack of understanding on my part. I thought my 16s with 5 battery packs paralleled together made it a 16s5p.

I believe you are saying for it to be a 16s5p Id have to parallel each individual cell in each pack to the other 4 packs ?

The idea was to parallel the whole packs , I.e go from the positive terminal of the pack to the positive of the next pack etc and same with the negative

So I guess doing it my way will need 80 longmons , and the other way only 16 but what really screws my mind is that I thought the longmon balanced each individual cell to the right voltage and what I dont get is if you have say 1 cell from each pack in parallel with 1 cell from each of the other packs how I appreciate the voltage stays the same across the 5 cells and it balances that but how would you know if one of the cells was at a higher voltage than the others or am I overthinking this ?

Thanks for the link to the video. Ill take a look at that tomorrow.
 

OffGridInTheCity

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Excellent questions - so I did some drawings to try to help the discussion :)

Here's a couple of drawings illustrating 16s5p (16 longmons)vs 16s1p * 5 (80 longmons):

image_ymhetr.jpg


image_dvcyjw.jpg



>I believe you are saying for it to be a 16s5p Id have to parallel each individual cell in each pack to the other 4 packs ?
Yes. The top drawing above.This is 16 longmons and cost effective (save $1000) if using Batrium.


>The idea was to parallel the whole packs , I.e go from the positive terminal of the pack to the positive of the next pack etc and same with the negative
This is 16s1p (1 battery) with 5 of these in parallel. This is 80 longmons. The 2nd from the top drawing above.

>".....[size=small]and the other way only 16 but what really screws my mind is that I thought the longmon balanced each individual cell to the right voltage and what I dont get is if you have say 1 cell from each pack in parallel with 1 cell from each of the other packs how I appreciate the voltage stays the same across the 5 cells and it balances that but how would you know if one of the cells was at a higher voltage than the others or am I overthinking this ?[/size]

[size=small]When cells are in parallel (e.g. via the sense leads) they will all have the same voltage all the time - they keep each other the same. So 1 longmon willlower the voltage of the 5 cell(s) in parallel at the same time. A single longmon is very powerful compared to other BMSs - and can easily handle 5 of your cells in parallel. 16 longmons - 1 for each group of 5 cells with parallel sense leads - are controlled by the Watchmon supervisor... to keep all 16 groups of 5 cells in balance.[/size]

*The next question is... won't the sense leads *burn up* under load?. The load current will not flow thru the sense leads. The load will flow thru the battery cell to cell serialization connectionswithin each battery and the external parallelbattery wires (e.g. the heavy red/black on the drawings).

The sense leads will keep each group of 5 cells in almost exact unison of voltage... all the time... and so the current flow is small. The only time you could get a spike of current thru the sense leads would be the 1st time you hook up the cells together... so you want the 5 batteries to be near the same voltage before you connect parallel sense leads. After that - they will never be out of sync again :)
 

daromer

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You have 5p16s if you dont interconnect. 16s5p if you interconnect them all ;)
 

Chapelier

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Thats brill. Very clearly explained . A picture really is worth a 1000 words :)

Thats totally sorted out my misunderstanding. O.k so I can see that the batrium is probably overkill but Ill still probably go that way.

Im not sure how easy it would be to rewire the packs to 16s5p. I certainly dont think they will dismantle easily ...

Im ok with spending a bit more on the longmons , its not like I have any other hobbies :) my wife might be a bit annoyed though If she finds out :)
 

daromer

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I would not go 80 longmons for 20Ah cells.. Its better just to rewire it properly if you ask me.
 

OffGridInTheCity

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You know.... hooking up 80 longmons is 80 x 2 = 60 wires between longmons and the cells. Plus you need to hookup the daisy-chain for the 80 longmons to the supervisor. Not sure its any more work to parallel the individual cells out to 16 longmons and you can save $1000. The key thing I find helpfulis to identify the cells and their + / - (s) and then work up a diagram (pencil + paper is fine) and then wiring should be straight-forward.

I found this BMW i3 Battery Module 'closeup' youtube -https://youtu.be/w61o8vPF9AY I couldn't find an i8 youtubes but maybe its similar? / pull of the top and you can see the cells and trace the wiring harness and then use the sense lead wiring harness to branch/extend out+ and - as needed. Or use a volt-meter to measure the sense leadwiring harness to find 0 -> 4v, -> 8v, -> 12v ... etc.
 

Chapelier

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O.K yes I am here to learn so Ill follow your advice and start studying how to re-wire them .

Ill go ahead and order the watchmon 4 and 16 longmons so Im ready . Thanks for pointing me in the right direction. Im sure Ill be back for more advice soon :)
 
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