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Batrium bms for 24v modules
#1
I purchased 4 ea. of a 24v volt battery module 250ah ~ . The ones that battery hookup was selling. I plan to run all 4 in Parallel. 100 amp 24v load from an ac unit.
I wanted to get a Batrium bms. Each module has 8 lifeo4 3.2v cells in series.
I would like maximum safety . I would like to monitor each cell.
What Batrium system do I need ? If I went with m7 , would I need an M7 for each module ?
Or should I be looking at something else ?

Thanks in advance.
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#2
Admin, thanks for moving this. Sorry for posting in the wrong section.

Anyone care to comment ?
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#3
You'll need some kind of 'mon' for each cell - e.g. 8 mons per battery * 4 = 32mons To only use 8 mons you'd have to reconfigure the batteries so the cells (in each battery) are hooked in parallel - but from video I've seen that's a lot of work / is probably not a good approach.

As far as the best mon - ask www.batrium.com I'm sure they'd be happy to make a suggestion. But just as an idle thought, standard longmons could be used as they operate on a voltage range - don't care about specific cell other than physical mounting. The standard cable wires are 8" long - so if can mount them within 8 inches of each cell (and 8 inches of each other) in a way that the heat won't burn up anything - it should work fine. It could be that the longmon wires to +/- of the battery can be longer than 8" but I'm not sure at what point the voltage reading would be 'off' - maybe another question to www.batrium.com or this forum.

As a side note, @DavidPoz just did a youtube tearing these packs apart to work on his own BMS wiring - Re-Wiring LiFePO4 Battery. $100/kwh https://youtu.be/aO-DlNrj5SU - might be helpful for your planning options.
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#4
You can possibly parallel all the bms/balance leads together so you only require 8 longmons instead of 32. Just take each balance lead out of each battery and group them together. No reconfiguration of the cells required.
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#5
(11-21-2019, 09:27 PM)not2bme Wrote: You can possibly parallel all the bms/balance leads together so you only require 8 longmons instead of 32. Just take each balance lead out of each battery and group them together. No reconfiguration of the cells required.
Yes - in fact @Daromer has a youtube where he did this and I remember asking about this (concerned about the level of current flow) but the consensus was its NOT high current and OK to do.

So the key question I would ask - is how far can the longmons be and still report correct voltage per cell.  The standard harness is 8 inches - so 12 or 16 inches is probably not a big deal but 24inches or 36inches?  - e.g. these batteries are pretty large and 4 of them could result in very long wiring.    Just don't know how long the longmon leads can be. Maybe if the batteries are stacked vertically and the longmons are in the middle of the stack to minimze distance?
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#6
Thanks for the detailed replies. I did contact Batrium, they cannot offer advice on what I should purchase. They recommended this forum. I did happen to see the David Poz video.
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#7
(11-22-2019, 03:07 AM)Jim-C Wrote: Thanks for the detailed replies. I did contact Batrium, they cannot offer advice on what I should purchase. They recommended this forum. I did happen to see the David Poz video.

I use Batrium and its fantastic for several reasons - one of which is that a longmon can truely can balance up to 500-1000ah cells/packs, has fantastic metrics and options, and is designed at the cell level (not the battery level - e.g. 7s or 14s or 16s). You can add up to 500? (or some huge number) of cells/packs - so you could literally manage 20 of these batteries. My own packs are 260ah each and when I put new packs online (pretty far out of balance from others) they balance within 1-2 days no problem.

Suggestion:
Start with 8 longmons in a mount and wire them up to the battery voltage wires as shown in DavidPoz youtube.   Measure voltage at the longmon and then at the cell directly and see the difference.  Maybe 20mv (nothing) or 50mv?  or even 100mv? worst case.   Batrium reads the longmons (doesn't care about any difference between longmon and actual cell) and you can use the delta to adjust hi/low control voltages appropriately in the interface.    For example, if the cell is 3.10v and longmon reports 3.05v then you have a 0.05v difference - simply set your high/low accordingly

Assuming you get the 1st 8 longmons working - then either buy 24more or parallel in the other 3 batteries and again check for deltas.   If you have $$ I would buy the 32 so you have individual cell info - this will alert you if a particular cell get's in trouble as apposed to paralleling all 4 cells you won't know which one of the 4 is pulling the others down.  BUT - its not wrong either way.

I'm confident you'll find that Batrium will do the job as its the most flexible/adjustable that I've seen out there.
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#8
Okay now we are getting somewhere. Smile Thanks OffGridInTheCity .
I'll purchase 32 LongMon.
Which controller do I buy ? Watchmon4 for Longmon and Expansion ??
I would order the 500 amp shunt . Anything else ??

I promise I ask these same question to Batrium and they wouldn't give me an answer.
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#9
(11-22-2019, 02:13 PM)Jim-C Wrote: Okay now we are getting somewhere. Smile  Thanks OffGridInTheCity .
I'll purchase 32 LongMon.
Which controller do I buy ?  Watchmon4 for Longmon and Expansion ??
I would order the 500 amp shunt . Anything else ??

I promise I ask these same question to Batrium and they wouldn't give me an answer.
This is a complete starter kit - watchmon4 + expansion + shunt + 7 longmons.    https://www.batrium.com/collections/dece...xp-longmon
Then add additional longmons - they sell them in various quantities.

The 'expansion board' is useful to control things - such as your own shunt-trip or cooling fans or other..    You can go without it but then you are limited on external controls - a lot of us go with the flow and include it.

The longmon specs https://support.batrium.com/article/123-longmon show a 2.2v to 5.4v (per cell) operating voltage range - so that should work fine for you.

As far as mounting the longmons - I mounted mine vertically but they can also be mounted horizontally etc...  just need airflow around most of the body of it for heat to escape that's generated during balancing.  They have notches near top/bottom that avoid getting hot that are perfect for twist-ties.   Mine are mounted vertically with twist-ties to the 18650 cell holders...


I should note each longmon is plugged into (chained) to the next and as mentioned the standard cable for this is 8" long - so you should try to mount them within a few inches of each other as practical. For example - in my picture I start the chain at top left row, go horizontally and then jump from 1st row to 2nd row at the right side of the shelf and chain to the left, jump to the 3rd row and back to the right - so the main connection points to the watchmon are top left and bottom right of the battery pack. You want to keep this in mind as you design a battery holder etc.
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#10
Okay , got it . I truly appreciate the detailed response. I’ll add the shunt trio breaker to the list . I’ll
post back when I hook it up .
hbpowerwall likes this post
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