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Batrium selection woes.
#1
Hi all, I have read most, maybe all of this forum, watched videos until I simply can not go anymore trying to find a logical answer to my question. I will try to convey an overview of where I am at so I can hopefully get someone to help me.  I am trying to choose which Batrium would be the best fit for my system that I am building.   I am leaning heavily on building a 14s 20p battery pack system based on what I saw built by user Owitte's "There's a new wall in Germany!".  I really liked the smaller packs as I was thinking it would be easier to remove a pack to repair a bad cell instead of pulling a bigger pack like most use, in case of a problem.

So I ordered 1600 18650's from the recent modem sale (200 of the 8 cell modem packs), and I have about 300 processed so far with the mah and resistance written on them, average being somewhere around 2300 and 80.   I was going to start making 14, 20 cell packs using repakr, so that I could have a "test" string of batteries complete @48V ready to go for testing purposes.  I am really excited to have something to work with just to make sure that my 9, 250watt used panels that i bought off ebay are working properly.  I have those wired 3 series 3 parallel to a Epever 60A 6415AN (which i need the setup parameters to manually enter for lithium batteries if anyone has done that please let me know what they are because I didnt realize it was not lithium ready when I ordered it, thanks!).  The panels are outputting at 100V usually (36.7 x3) with the partly cloudy days we have been having and should be about 27 amps (8.9 amps each panel).  At this time I have a 5000watt 48v Aims inverter coming in a few days.  I will buy a better quality split phase once I get more experience.

Ok so from what I gather on Batrium's website and YT vids and these forums, The 48V BMS solution Batrium has is the WatchMonPlus (WM5).  But I am seeing information that when I later get all of my cells processed and make the remaining 20 cell packs, and wire them into the system parallel, that the WatchMonPlus will not work.  Or will it?  Can I just parallel in the next 4 strings and it will work? Or do I need to get the Watchmon4 and buy a large pack of Longmons and place a Longmon on each of the individual 20 cell packs?  As I said I have 1600 cells so that will make about 70 packs @20 cells each using 4x5 holders.  So thats roughly 5 parallel "strings" of 14 packs (5x of 14s20p ). 

OR.  Should I scrap the whole 5 strings of 14s20p and just make 1 string of 14s100p and then buy what, a WatchMonPlus?  I am trying to do this without spending unnessecary excess into BMS, and if changing my packs to larger ones is the more practical solution than so be it.

Thank you!
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#2
WM5 and then as you add parallel packs the new add on board
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#3
But when I add more strings in parallel the packs essentially stay the same electrically except for increasing in ampacity right?  A 20P cell becomes a 40P cell with the next string added in parallel, then 60P, then 80P then 100P finally when I add the 5th string.  Each 20P pack is connected together at the lugs making them eventually @100p.  That should still work with just the one MultiMonPlus (WM5), the only difference being is that as I add each 20P pack string, is that each 20P pack is no longer individually monitored, but all the cells as one unit.  Is it as simple as that?  It should be.  Just making sure I understand the concept.  But, if I DID want to monitor each 20P in the 5 total strings I'd have add 4 MultiMons in between the strings.  Either way works just depends on how much I wanna spend.  Right?  !!?
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#4
(04-10-2020, 12:21 PM)Reek Wrote: But when I add more strings in parallel the packs essentially stay the same electrically except for increasing in ampacity right?  A 20P cell becomes a 40P cell with the next string added in parallel, then 60P, then 80P then 100P finally when I add the 5th string.  Each 20P pack is connected together at the lugs making them eventually @100p.  That should still work with just the one MultiMonPlus (WM5), the only difference being is that as I add each 20P pack string, is that each 20P pack is no longer individually monitored, but all the cells as one unit.  Is it as simple as that?  It should be.  Just making sure I understand the concept. 
Yes, its as simple as that.   Balancing will gradually take longer as you increase the number of cells in parallel but if you take care to keep things relatively balanced when you add new packs this should not be a problem.


(04-10-2020, 12:21 PM)Reek Wrote: But, if I DID want to monitor each 20P in the 5 total strings I'd have add 4 MultiMons in between the strings.  Either way works just depends on how much I wanna spend.  Right?  !!?
Exactly. I use WM4 and I'm up to 84 longmons now (84 individual packs). I could combine packs and have less longmons but its easier (for me) to spend $ to add longmons than reconfigure things. I understand the WM5 has something coming that will let you add more than 14 individual packs in the future.
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#5
Got it thank you !!!!

Now, I read that the WM5 can be configured to trigger a relay to shut down a charge controller. How does this happen? I'm assuming that when the charge input to the batteries exceed the set parameters in the WM5, the WM5 will send a trigger to one of the output connecters that I will wire into a relay that will open the circuit between the charge controller and the battery? Or I guess I could also wire the relay to open the charge controller's power input shutting it off, either or, as long as charge current is stopped to prevent overcharging. Is that right?

I'm also assuming that I can set up a relay also to shut down my inverter as well, by disconnecting it from the battery if the battery voltage drops under a set parameter in the WM5 as well to prevent over discharging? Is this how most set it up to handle protecting the battery from over / under voltages? I would assume that the best option is purchasing the expansion board to achieve all of these? Can Im assuming I can use the standard relays that I have as long as they match the voltage triggers?
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#6
You can configure this yes. Just det critical values and then what output to trigger. You can set, min max voltage per cell or pack or current.
Note that this is critical fault protection and this is what all bms systems have or should have.

Charging or discharging limits should be set in the Charger or inverter.
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#7
Well I'm afraid that the current inverter that I have wont "let go" when it's supposed to and therfore discharging my cells under 3.0 Volts, damaging their lifespans.

I have no experience yet, I'm just trying to make sure I have a good working knowledge of what I am doing so I dont find myself ruining expensive equipment, while obtaining said experience =)
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#8
(04-11-2020, 12:08 AM)Reek Wrote: Well I'm afraid that the current inverter that I have wont "let go" when it's supposed to and therfore discharging my cells under 3.0 Volts, damaging their lifespans.

I have no experience yet, I'm just trying to make sure I have a good working knowledge of what I am doing so I dont find myself ruining expensive equipment, while obtaining said experience =)
To me, its important (I would say necessary) in an off-grid system to be able to turn the inverter on/off by battery voltage ranges that you can set independent of the inverter's hard-wired hi/low operating range.  In my case the Midnite Classic charge controller Aux1 relay gives me this capability.    You could also do this thru Batrium if you have the expansion board.  

You can control the Inverter by tapping into its on/off switch or by getting a large amp relay (such as a Gigivac) to turn on/off the DC going to the inverter.
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