I started this discussion about a battery bank I'm building by posting in W0ss' thread, here, but was given the welcome tip to begin my own thread, so pls. bear with me while I try to summarize the early stages of my build.
I'm working on my first battery build for a ~ 3kw solar array paired with a battery charger/inverter (I've not yet determined which one, but am back and forth between a Schneider and a Radian, 4 kw model either way).
The build I'm working on has (3) li-ion LG chem modules, each of which is wired as: (3p 10s) + (3p 8s). I am still trying to decide exactly how to configure the battery bank, but probably want 48V nominal and want to add BMS protection. One possibility is that I remove a few cells from ea. of the (3) (3p 10s) modules and end up with each of the three modules as (3p 16s) with 18 total cells leftover for another project. Maybe, though, I'll keep all 18 groups in ea. module in series and try to find a charger-inverter with a high cut-off voltage - I'm not sure yet, but I just learned that the Radian inverter I was eyeing cuts off at 64V, so either the original module set up (3p 18s) or the Radian inverter would have to change. Any tips/suggestions on this point v. much welcome.
One other detail:
The cells are the LG chem N2.1 60ah cells:
If possible I'd like to disturb the modules as little as possible, so I started by trying to figure out the existing (2) two 8-pin connectors ([1] one of them in the first pic below). By the way, if anyone could tell me the connector part # that fits this, or even how to find the part #, I'd be really thankful. I googled and searched a few forums, but no luck so far.
I started working on the 3p 8s module first, trying to pin out the connector. . . . I guess it makes sense to say first that if anyone has the pin-out for this module or if it has been posted somewhere and I missed it in my forum search, please let me know. I would be very grateful for that info.
For now, I went ahead, using floydR's directions here (thank you), and got as far as what is for me a puzzle with pin2 in the connector on the Left hand side (with the mounting plate on the bottom) of the (2) two 8-pin connectors. The second pic shows my progress so far and also presents my current (sorry, that's got to be an old joke here) puzzle:
each set of (3) parallel cells has ~3.4 V. The trouble I am having with pin 2 is that I am getting only half that voltage when I test pin 2 with several of the the bus bar points, e.g. pin 2 - R side CV1: 1.7V and pin 2 - R sideCV2: 1.8V. It's as if somehow pin 2 cuts one of the cell groups in half, but I am clueless as to how that would work. For me, the mystery deepens when I measure pin 2 - L sideCV1: 3.4V.
Any help appreciated.
I'm working on my first battery build for a ~ 3kw solar array paired with a battery charger/inverter (I've not yet determined which one, but am back and forth between a Schneider and a Radian, 4 kw model either way).
The build I'm working on has (3) li-ion LG chem modules, each of which is wired as: (3p 10s) + (3p 8s). I am still trying to decide exactly how to configure the battery bank, but probably want 48V nominal and want to add BMS protection. One possibility is that I remove a few cells from ea. of the (3) (3p 10s) modules and end up with each of the three modules as (3p 16s) with 18 total cells leftover for another project. Maybe, though, I'll keep all 18 groups in ea. module in series and try to find a charger-inverter with a high cut-off voltage - I'm not sure yet, but I just learned that the Radian inverter I was eyeing cuts off at 64V, so either the original module set up (3p 18s) or the Radian inverter would have to change. Any tips/suggestions on this point v. much welcome.
One other detail:
The cells are the LG chem N2.1 60ah cells:
Max charge full voltage | 4.2V |
Discharge cut-off voltage | 2.8V |
If possible I'd like to disturb the modules as little as possible, so I started by trying to figure out the existing (2) two 8-pin connectors ([1] one of them in the first pic below). By the way, if anyone could tell me the connector part # that fits this, or even how to find the part #, I'd be really thankful. I googled and searched a few forums, but no luck so far.
I started working on the 3p 8s module first, trying to pin out the connector. . . . I guess it makes sense to say first that if anyone has the pin-out for this module or if it has been posted somewhere and I missed it in my forum search, please let me know. I would be very grateful for that info.
For now, I went ahead, using floydR's directions here (thank you), and got as far as what is for me a puzzle with pin2 in the connector on the Left hand side (with the mounting plate on the bottom) of the (2) two 8-pin connectors. The second pic shows my progress so far and also presents my current (sorry, that's got to be an old joke here) puzzle:
each set of (3) parallel cells has ~3.4 V. The trouble I am having with pin 2 is that I am getting only half that voltage when I test pin 2 with several of the the bus bar points, e.g. pin 2 - R side CV1: 1.7V and pin 2 - R sideCV2: 1.8V. It's as if somehow pin 2 cuts one of the cell groups in half, but I am clueless as to how that would work. For me, the mystery deepens when I measure pin 2 - L sideCV1: 3.4V.
Any help appreciated.