Battery to Inverter voltage matching

[THUDGUN]

I'd like to build a 48V system, and have ordered an MPPT charge controller/inverter. I'm building the battery packs myself, using 18650 LiIo cells, and am trying to figure out the best configuration for those packs.

With a nominal voltage of 3.6v, going into a 48v system, do I do a series of 13 cells (46.8v) or can I go to 14s (50.4v)? I can't seem to find anything on standard conventions for such an undertaking. I don't want to just do what others are showing they're doing, I want to understand what I'm doing and, hopefully make the best decision for my application.

Thank you kindly

 

[Ampster]

With a nominal voltage of 3.6v, going into a 48v system, do I do a series of 13 cells (46.8v) or can I go to 14s (50.4v)? I can't seem to find anything on standard conventions for such an undertaking.

Either one works if you can find a BMS. I used Nissan Leaf modules which were actually 2P2S so I had to go with an even number of 14 cells (7 modules) I used a BMS designed for 16 but it was easily configured for 13 or 14

 

[THUDGUN]

Either one works if you can find a BMS. I used Nissan Leaf modules which were actually 2P2S so I had to go with an even number of 14 cells (7 modules) I used a BMS designed for 16 but it was easily configured for 13 or 14

Thanks.

Is there a convention, like ~+10%, or would it be buried in some technical chart in an owners manual I'll just have to track down? This is just a fun experiment (making my own battery packs) and will likely try different chemistries and arrangements. Like the 28.8V LG Modules from an EV. 2s would be 57.6V...

I'll be using an active balancer with a monitor instead of a traditional BMS, used as part of regular maintenance. I like feedback in my systems. It can handle up to 24s, so no worries there.

 

[Ampster]

Is there a convention, like ~+10%, or would it be buried in some technical chart in an owners manual

There is no convention but there are specific voltage parameters in inverters that need to be observed. For example the lowest Low Voltage cutoff and high voltage settings are not the same so build your pack to be within your inverter window, also keeping in mind where you expect to stop charging and where you want to stop discharging your cells.

 

[THUDGUN]

There is no convention but there are specific voltage parameters in inverters that need to be observed. For example the lowest Low Voltage cutoff and high voltage settings are not the same so build your pack to be within your inverter window, also keeping in mind where you expect to stop charging and where you want to stop discharging your cells.

Hopefully that detail is in the manual, because all I'm finding on-line is a minimum startup of 44v, where the battery is concerned...

 

[Ampster]

44 volts should work for 13S if you don't want to take the cells below 3.4 volts per cell.