SnackMasterX
New Member
- Joined
- Jan 5, 2020
- Messages
- 14
Near the end of last year, I bought some raw cells from the BLS store along with a Daly BMS, but I just wasn't satisfied with the overall result. A lot of over-thinking later, I decided to design my own battery cap, attached images to this post.
So this was the 2nd revision, and I'll be redesigning it again based on more considerations (BMS placement) and how this will all fit together. I'm unsure if the final version will have this semi-universal fit for 2x2 configuration. I just don't like the open channels between cells that don't connect, even though there will be a lid that will stop anything from shorting the terminals. In the next version I'm going to start testing mechanisms to secure the cells in place, but not sure of the best way forward on this part quite yet.
I haven't designed the lid yet, but but here are some requirements:
Must secure BMS in place.
Must have zip tie points for cable management.
Must have mounting positions for distribution blocks.
Must either reuse original distribution block cover, or design a new one.
The distribution blocks will be for converting the 8 AWG wire from my BMS into 4 AWG. This is purely convenience, but when I'm done maybe we can sarcastically call it art.
So a big thing for me was that I wanted to do per-terminal temperature monitoring, along with ambient temperature monitoring. The distribution blocks are supposed to be good for up to 150 amps, and I'm sizing my system for 80 amps per battery max. This is due to current and final expected sizing of the system. I'll use a Teensey to put some logic between the temperature sensors and the BMS. Goal being the BMS can do BMS things if an individual terminal is getting too hot, or maybe the cells still haven't warmed up compared to ambient yet after a cold night due furnace failure.
Or who knows, maybe we want to add a heating pad that would turn on if the cells are getting too cold. Maybe we want a fan that will kick on if cells start getting too hot compared to ambient? The potential is there, just not planned yet
My immediate next steps on this are trying to figure out the best placement for a JST-XH in the battery cap. This will connect to the terminals for balance leads, along with the temperature sensors. My dream is that I'll somehow be so good at math, that I can just solder some JST-XH connectors to a prototype board, and it will just sit down and magically plug into all 4 cells. Idea being the balance leads will route to the BMS (I just wanted a 5 pin to 5 pin connector instead of a mess of wires) and temperature sensors to a Teensey.
So this is just a single pack, but I want to have multiple packs built exactly like this. Now I'll need to find a way of connecting the Teensey's, and having them all communicate with a raspberry pi (up for discussion on this if you have better ideas, I was thinking a pi zero w) for metric tracking/reporting on each pack, down to the individual cell. I'll use the Teensey to read data from the BMS for really anything I can read from it, also report temperature to the BMS directly. I've considered adding cell internal resistance testing/monitoring, but I'll leave that up for debate.
I also want to figure out how to get current monitoring into this for things like:
Amps coming in from the solar array.
Draw or charge from inverter/charger
Usage of overall 12v system
Shore power usage, when connected.
Your imagination is the limit here. These are just a few things I can think of.
UI design is not my thing so I'll wait and dred this when I get closer to not being able to avoid it.
My long term plan is to get this all build out, then share the code/design so everyone else can replicate this in their own setups. This is just a small piece of the puzzle that I'm focusing on right now.
What do you think so far?
Any suggestions or feedback?
What other features would you love to see in this?
I'll post project updates periodically. Let me know your thoughts and questions though!
So this was the 2nd revision, and I'll be redesigning it again based on more considerations (BMS placement) and how this will all fit together. I'm unsure if the final version will have this semi-universal fit for 2x2 configuration. I just don't like the open channels between cells that don't connect, even though there will be a lid that will stop anything from shorting the terminals. In the next version I'm going to start testing mechanisms to secure the cells in place, but not sure of the best way forward on this part quite yet.
I haven't designed the lid yet, but but here are some requirements:
Must secure BMS in place.
Must have zip tie points for cable management.
Must have mounting positions for distribution blocks.
Must either reuse original distribution block cover, or design a new one.
The distribution blocks will be for converting the 8 AWG wire from my BMS into 4 AWG. This is purely convenience, but when I'm done maybe we can sarcastically call it art.
So a big thing for me was that I wanted to do per-terminal temperature monitoring, along with ambient temperature monitoring. The distribution blocks are supposed to be good for up to 150 amps, and I'm sizing my system for 80 amps per battery max. This is due to current and final expected sizing of the system. I'll use a Teensey to put some logic between the temperature sensors and the BMS. Goal being the BMS can do BMS things if an individual terminal is getting too hot, or maybe the cells still haven't warmed up compared to ambient yet after a cold night due furnace failure.
Or who knows, maybe we want to add a heating pad that would turn on if the cells are getting too cold. Maybe we want a fan that will kick on if cells start getting too hot compared to ambient? The potential is there, just not planned yet
My immediate next steps on this are trying to figure out the best placement for a JST-XH in the battery cap. This will connect to the terminals for balance leads, along with the temperature sensors. My dream is that I'll somehow be so good at math, that I can just solder some JST-XH connectors to a prototype board, and it will just sit down and magically plug into all 4 cells. Idea being the balance leads will route to the BMS (I just wanted a 5 pin to 5 pin connector instead of a mess of wires) and temperature sensors to a Teensey.
So this is just a single pack, but I want to have multiple packs built exactly like this. Now I'll need to find a way of connecting the Teensey's, and having them all communicate with a raspberry pi (up for discussion on this if you have better ideas, I was thinking a pi zero w) for metric tracking/reporting on each pack, down to the individual cell. I'll use the Teensey to read data from the BMS for really anything I can read from it, also report temperature to the BMS directly. I've considered adding cell internal resistance testing/monitoring, but I'll leave that up for debate.
I also want to figure out how to get current monitoring into this for things like:
Amps coming in from the solar array.
Draw or charge from inverter/charger
Usage of overall 12v system
Shore power usage, when connected.
Your imagination is the limit here. These are just a few things I can think of.
UI design is not my thing so I'll wait and dred this when I get closer to not being able to avoid it.
My long term plan is to get this all build out, then share the code/design so everyone else can replicate this in their own setups. This is just a small piece of the puzzle that I'm focusing on right now.
What do you think so far?
Any suggestions or feedback?
What other features would you love to see in this?
I'll post project updates periodically. Let me know your thoughts and questions though!
