How many lith-ion batterys 48v

[Amish David]

I have a neighbor going to build me a battery Bank he's out of state and cannot answer his phone at this time. I'm looking at 3000 milliamp lithium ion batteries. I had people tell me to use 52 batteries I've had people tell me to use 72 batteries I'm looking for a definite answer I'm looking at building a 48 volt 20 to 24a h battery pack. Just wondering how many batteries do I truly need in order to get this correct. Thanking you in advance David

 

[harryS]

In my opinion, you need 91 batteries, if they are 18650 cells.

The round 18650 cells are operated between 3.0 and 4.2 volts, with a nominal voltage of 3.7 volts when half discharged. If you put 13 of these in series, you get 48.1 volts.

Your amp hour number (AH) is determined by how many parallel cells/batteries in each group. Battery capacity is rated in AH. You said 3000 milliamps. The correct terminology is 3000 milliamp-hours, which is the same as 3 AH. If you have only one battery per group, then you have 3AH. Two 18650's in parallel is 6 AH. Three is 9AH and so on. For a 20AH power bank, then you need at least seven of these batteries in parallel.

That's a lot of batteries. How to lower this? Use18650 cells with a higher AH rating. With 3.5AH batteries, you need six in parallel for 78 cells to get over 20AH.

 

[rich c]

There is more to a battery pack than just cells. Most importantly is a battery management system. Without this, you may be creating a fire hazard and charging will need to be carefully watched! From Wikipedia; "It protects the battery from operating outside its safe operation area, monitors its state, calculating secondary data, reporting that data, controlling its environment, authenticating it and / or balancing it".

 

[harryS]

A BMS board is around $10-30. Depends on how much currrent Amish Dave needs to use. The knowledge to select and install it is much more expensive. I assumed his neighbor knows all of that. You also get into chargers, etc.

 

[rich c]

A BMS board is around $10-30. Depends on how much currrent Amish Dave needs to use. The knowledge to select and install it is much more expensive. I assumed his neighbor knows all of that. You also get into chargers, etc.

My concern was that since they were asking about how many batteries to use, I was not sure they knew about the BMS.

 

[Amish David]

My concern was that since they were asking about how many batteries to use, I was not sure they knew about the BMS.

All this is new to me. Thanks guys he knows how to put everything together and how to install the BMS, he's just short on time because he works so much out of state and country. I'm just trying to get the information together so hopefully I can get all the stuff lined out I will check on some higher rate Sony and LG batteries. Again thanks guys