Bms for solar emergency back up

[KSisk]

I am in a bit of a pickle. I am trying to build a 24v emergency solar generator. Due to them shutting the bridges down and getting stranded with no gas or power for a week or more. I have some medical stuff, a modem and router, and charger for my power wheelchair that I need to use.
I have 2 of these battery banks with no bms from batteryhookup.com. 25.9v 32ah 828.8wh SPIM08HP 24v POWER Module https://cdn.shopify.com/s/files/1/2398/3077/products/162358537132153949_5_1080x.png?v=1625886189 I want to run this in a series for 24v 64ah. I would like to use a 24v 7s 100a bms for each pack (Daly or anything you suggest) after buying I thought how can I make it charge the batteries and power the load (inverter) at the same time? It seems that the bms can only do one or the other. Inverter 2000 or 3000w pure sine. Charge controller maybe a 40-60a mppt? Panels thinking (2) 24v 200w?
I can read sematics but can not figure out how to make the bms or something work to protect the batteries (assuming I need one)
Please help

 

[Samsonite801]

The BMS sits in between the battery cells and the charger/loads. There are 2 types of BMS in this regard. 'Same Port' BMS, or 'Separate Port' BMS.

Same Port BMS is where charging and loads are connected to the same B- lead. Separate Port BMS have different port on the BMS for charging only, in addition to the B- lead for loads.

Same Port BMS installations are probably more common. Don't worry, the loads and charger can run on the same port just fine. The charging will supply the loads, and whatever's left just goes to the battery (or the other way around), it all balances out automagically... Voltage flows like water back and forth.

But you do need a BMS. If you have 7 cells, then you need a 7s. Depending on how you wire them, you may need 2 BMS. If each cell gets its own BMS then you need 2 BMS (for example on a 7s2p setup). If you parallel each pair of 2 cells, then you can get by with one (for example on a 2p7s).

I prefer to not parallel cells but rather parallel battery banks, but if you need to save money and only buy one BMS then you can parallel cells if the one BMS has the amps capacity to handle what you need to run through it.

 

[KSisk]

The BMS sits in between the battery cells and the charger/loads. There are 2 types of BMS in this regard. 'Same Port' BMS, or 'Separate Port' BMS.

Same Port BMS is where charging and loads are connected to the same B- lead. Separate Port BMS have different port on the BMS for charging only, in addition to the B- lead for loads.

Same Port BMS installations are probably more common. Don't worry, the loads and charger can run on the same port just fine. The charging will supply the loads, and whatever's left just goes to the battery (or the other way around), it all balances out automagically... Voltage flows like water back and forth.

But you do need a BMS. If you have 7 cells, then you need a 7s. Depending on how you wire them, you may need 2 BMS. If each cell gets its own BMS then you need 2 BMS (for example on a 7s2p setup). If you parallel each pair of 2 cells, then you can get by with one (for example on a 2p7s).

I prefer to not parallel cells but rather parallel battery banks, but if you need to save money and only buy one BMS then you can parallel cells if the one BMS has the amps capacity to handle what you need to run through it.

Thank you
I have 2 individual assembled batteries I just need to add the bms. I am thinking one for each battery that way I can put them in parallel or run them individually.
https://batteryhookup.com/products/25-9v-32ah-828-8ah-spim08hp-24v-power-module.
looking at the Daly 7s 100a bms. I plan to use a 2000w inverter. Maybe 3000w?
This is my first attempt with batteries and also solar

 

[Samsonite801]

Thank you
I have 2 individual assembled batteries I just need to add the bms. I am thinking one for each battery that way I can put them in parallel or run them individually.
https://batteryhookup.com/products/25-9v-32ah-828-8ah-spim08hp-24v-power-module.
looking at the Daly 7s 100a bms. I plan to use a 2000w inverter. Maybe 3000w?
This is my first attempt with batteries and also solar

Yeah I like the idea of 2 BMS and having separate battery banks. I never tried the Daly BMS before, maybe recommend to search here and read other threads on Daly BMS experiences.

Will these banks ever see freezing temps or will they always be in a temp regulated environment? In other words, do we need BMSs which support low temperature charging cutoff for safety? (since we cannot charge lithium below freezing without damage)...

 

[KSisk]

Yeah I like the idea of 2 BMS and having separate battery banks. I never tried the Daly BMS before, maybe recommend to search here and read other threads on Daly BMS experiences.

Will these banks ever see freezing temps or will they always be in a temp regulated environment? In other words, do we need BMSs which support low temperature charging cutoff for safety? (since we cannot charge lithium below freezing without damage)...

I live on coastal SE NC it rarely gets below 40
But they are going to be in a insulated storage room.
The Mppt SCC I like have a low temperature cut off.
I really appreciate any advice you can give

 

[Samsonite801]

I live on coastal SE NC it rarely gets below 40
But they are going to be in a insulated storage room.
The Mppt SCC I like have a low temperature cut off.
I really appreciate any advice you can give

If the room never gets to freezing it's fine, but the SCC should also be good to kill charging (as a safety), just make sure if it has an external temp probe, you put it right on the battery pack, or if the temp probe is built inside the SCC on the main board, then you put the SCC close to the batteries as possible so you can get fairly accurate temp readings.

Or I know on Victrons for example, they have an internal temp probe but if you want more accurate, they have an external probe you can buy to read the temp directly on the battery bank in case the SCC is mounted far away. Not sure what brand SCC you have, but on the Victrons, if I remember right, the internal temp probe only reads once per day, so really with them, one really needs to buy the external one to get realtime temperature monitoring anyways.

If the low temp cutoff temperature setting is adjustable in the SCC, then you can calibrate it (go up or down on it) as needed to reflect a more accurate 'at battery' temperature if you find it is not exactly on par with temp reading right at the battery.

 

[KSisk]

If the room never gets to freezing it's fine, but the SCC should also be good to kill charging (as a safety), just make sure if it has an external temp probe, you put it right on the battery pack, or if the temp probe is built inside the SCC on the main board, then you put the SCC close to the batteries as possible so you can get fairly accurate temp readings.

Or I know on Victrons for example, they have an internal temp probe but if you want more accurate, they have an external probe you can buy to read the temp directly on the battery bank in case the SCC is mounted far away. Not sure what brand SCC you have, but on the Victrons, if I remember right, the internal temp probe only reads once per day, so really with them, one really needs to buy the external one to get realtime temperature monitoring anyways.

If the low temp cutoff temperature setting is adjustable in the SCC, then you can calibrate it (go up or down on it) as needed to reflect a more accurate 'at battery' temperature if you find it is not exactly on par with temp reading right at the battery.

Thank you for all your advice
I have a lot of ? Thank you for helping me so very much