Expert Opinion

[paulmurdoch]

Hello,
I'm looking for some expert opinions and experience from a similar setup for what I'm planning! I purchased 28 LG chem 48V 14s battery modules tested at ~75% of capacity at 2kWh.
My intention is to parallel each battery pack to give a 2S 7P and series 7 modules to give a 14S battery 48V at 15kWh. Then parallel the 4 14S 48V batteries to power my off grid vacation house.
The plan is two fold, 1) to have sufficient power for three days back up 2) to only cycle around 30% of the batteries daily so they last a great deal longer, considering the degradation what the cells already have. Been a vacation property I want to monitor and if needed adjust/remote trip/stop the system in case of an issue. For the breaker I'm thinking about a ABB breaker but I'm torn between buying separate breakers (150A) for each battery bank to enable me to remotely cut off the bank if needed or one large 300A ABB breaker for the parallel battery banks. The other issue I'm pondering is how to remotely monitor and trip/stop the system in the event of a power overload or stop charging in the event of low temperature.
I'm considering two devices either a WatchMon5 with multi mon or a Daly 200AMP BMS connected to a PC with remote access. Any advice for this set up would be most welcome.
Thank you!

 

[Ampster]

I am not an expert by any means. I place a lot of emphasis on being able to remotely monitor my BMS and my inverter. Whether it be from the comfort of my couch or halfway around the globe it has proven valuable. Nevertheless it has made me lazy about setting and verifying the last of my automatic failsafe mechanisms that are available.

 

[MichaelK]

I would be deeply concerned about properly balancing that many parallel battery connections. I now only operate single string battery banks of the desired Ah, but that's me.

 

[Ampster]

I only responded to the remote monitoringissue initially. However @MichealK got me thinking about your pack more. I am not sure I fully understand the module sizes and the flexibility in configuration. For years I used Nissan Leaf modules and paralleled up to 7 modules and put of of those in series for one single pack. It was easier for me to monitor.

 

[DThames]

Did you see the video by David Poz where he disassembled these and showed how the cell pairs could be put in parallel before the series connection was made? I think you are talking about the same used battery that David was showing.

 

[Ampster]

I think you are talking about the same used battery that David was showing.

If that is the case and if these all came out of the same vehicle then they most likely were matched. The use case is off grid and that use may favor redundency. My particular hardware makes it more expensive to monitor more than one pack, but if that can be overcome then two parrallel packs would make sense. As far as overcurrent protection is concerned on a two pack scenerio I would use a large Class T fuse on the common negative and individual circuit breakers on each pack.

 

[snoobler]

Hello,
I'm looking for some expert opinions and experience from a similar setup for what I'm planning! I purchased 28 LG chem 48V 14s battery modules tested at ~75% of capacity at 2kWh.
My intention is to parallel each battery pack to give a 2S 7P and series 7 modules to give a 14S battery 48V at 15kWh. Then parallel the 4 14S 48V batteries to power my off grid vacation house.
The plan is two fold, 1) to have sufficient power for three days back up 2) to only cycle around 30% of the batteries daily so they last a great deal longer, considering the degradation what the cells already have. Been a vacation property I want to monitor and if needed adjust/remote trip/stop the system in case of an issue. For the breaker I'm thinking about a ABB breaker but I'm torn between buying separate breakers (150A) for each battery bank to enable me to remotely cut off the bank if needed or one large 300A ABB breaker for the parallel battery banks. The other issue I'm pondering is how to remotely monitor and trip/stop the system in the event of a power overload or stop charging in the event of low temperature.
I'm considering two devices either a WatchMon5 with multi mon or a Daly 200AMP BMS connected to a PC with remote access. Any advice for this set up would be most welcome.
Thank you!

Not an expert. Not an expert who won't admit I'm an expert (there are a number on this board). At best a hack who knows a little less than he thinks he does. Jack of a handful of trades, master of none, etc.

I'm only halfway through my coffee, a little groggy, and it's also possible that age related cognitive impairment is already here, but I'm having trouble understanding what you plan to do because I can't reconcile the numbers.

You say you have 28 48V 14S 2kWh batteries, so I'm not seeing how you get 48V in any way besides having a 28P 48V bank.

Are you breaking the packs down into components?

Regardless, you need a BMS for each independent string. In the case of the 28 14S batteries in parallel, each battery would need its own BMS.

A batrium system would just need a *mon device on each cell group, which in the case of 28 14S parallel batteries - 392 *mon devices. That should break the bank.

 

[schmism]

Did you see the video by David Poz where he disassembled these and showed how the cell pairs could be put in parallel before the series connection was made? I think you are talking about the same used battery that David was showing.

This is what I would be doing (rebuilding pouch cells in parallel then those groups in series for a single 48v battery. (or perhaps 2 complete groups)

so per my attachment. after you re-arrange the cells. that gives you two 7p sets in a case. I'd put each of those sets parallel for 14P-4.2v battery in a single LG case. (you said you had 28 of these) so then stack 14 of those cases in a stack for a 14s stack of 14P cells for one 48v battery. Then do that twice for 2 48v batts of 14p-14s cells

you then need just 2 BMS one for each set of stack of cells.

Assuming each set of pouch cells is ~40ah (per battery hookup) then 14p = 560ah 48v battery stack

 

[snoobler]

Just confirming, with the Batrium, I believe you would only need the single BMS, but you would need 28 *Mon modules.

 

[paulmurdoch]

Gents,
Thanks for all your comments! Yes, I'm talking about the LG chem packs which David Poz did the strip down. Altogether I have 28 modules and like David suggested in his video, my plan was to position the pouch cells in parallel in each module to give a 2S 7P and then stack x7 modules in series to form a 48V 14S and have 4 of these stacks in parallel. However, I really like Scmism's idea of x2 48V 14p 14S.
I also like the added safety of the common class T fuse and separate breakers for each pack. Remote monitoring is also essential for me! So I really need the right system and I'm leaning toward about the Batrium but also looking at Daly options with remote PC access.
Thanks again!

 

[snoobler]

Gents,
Thanks for all your comments! Yes, I'm talking about the LG chem packs which David Poz did the strip down. Altogether I have 28 modules and like David suggested in his video, my plan was to position the pouch cells in parallel in each module to give a 2S 7P and then stack x7 modules in series to form a 48V 14S and have 4 of these stacks in parallel. However, I really like Scmism's idea of x2 48V 14p 14S.
I also like the added safety of the common class T fuse and separate breakers for each pack. Remote monitoring is also essential for me! So I really need the right system and I'm leaning toward about the Batrium but also looking at Daly options with remote PC access.
Thanks again!

3.5-4.05V will keep you in a 20-80% SoC for the most part.

This flavor of lithium does not have the multiple thousands of cycles of life, but are rated in the hundreds. 4.05V peak will push you somewhere around 2000 cycles. If you REALLY want to maximize life, keep it to 3.92V peak. At that level and below charging stresses that degrade the cells are essentially eliminated. I'm not sure where that will put you SoC-wise, but probably around 65%. If you ever need more than that capacity, it's less stressful to take that chemistry to 0% than it is to take it to 100%, but the occasional trips to the ends of the range won't make a measurable difference in the long run.

Lastly, if there's any deviation in the capacity of the 7P cell modules, you should make efforts to make every series element of the packs to have the same capacity. Poz may have mentioned this, but I only watch him from time to time.

 

[Factory400]

Joining the conversation.....interesting configuration and use case.
I like what I see of the Batrium system so far - definitely in consideration for my own similar system.

 

[paulmurdoch]

Hello again and happy New Year to all!
I didn't want to start a new thread so Ive added to my previous.

I'm also putting together a system for my offgrid driveway gate. The gate is over 800ft from the main house, so running a cable isn't really practical. As well as powering the gate and access keypad, I want to be able to monitor and operate the gate remotely. Ive attached a jpg with my wiring diagram and would appreciate any comments. I'm also considering adding a heating pad to the metal box where the batteries will be stored. The temperature will be controlled with a small digital temp switch. The battery bank is a 24V 7S configuration constructed from 18650 cells. The intention is to bury the battery bank box inside an insulated water proof container, the heating pad will be attached to the metal battery box. It gets below zero in winter, so it's a real concern. Any experience/suggestion with this problem would also be appreciated.

For info! If anyone is thinking about a remote gate operating system, which will allow access codes to be changed remotely, I would highly recommend the TTLock app. The keypads which use this software can be found on Ali.

 

[Trev2323]

Awesome Thread I learned some stuff and got confused on the rest. I purchased the same batteries BUT just the Chem packs not in the case. I am putting 14 in parallel to make 1 48v battery with a 100 amp DALY BMS. Anyone know what size fuse or Breaker I should use between the battery and the Growatt 48v 3k? I will use this for some youTube video but Primarily for a back up Generator