PowerLio
New member
- Joined
- Nov 1, 2017
- Messages
- 12
Hello everyone. I am in the process of building my first battery pack and I need some help to answer my questions.
So first, what is my project? My project is to build a very small powerwall with a capacity around 200Wh to power a little cabin (very little house with no electricity, water and even no cellular network lol) to power some lights with solar 30W solar panel to charge it (small power because we dont stay more than 2 nights up there).
So I have the choice between Lead-Acid 12V 17 Ah which is cheap and 18650 cells which interest me a lot.
Firstly, I decided to do a 3s7p build but reading the forum I learned that we cant use it for 12V systems then I decided to make a 7s3p system but that brought questions:
1. What is the interest of having more in serial than parallel? I mean what if I build a 1s21p?
2. Ive seen a lot of 3s BMS on Aliexpress (same on ebay) and since 3s is useless what is the utility of them? same with 5s: these are very very cheap like 3 each but what is the utility of them, can I make a 5s system and use it as 12V with a converter?
3. Another BMS question: on a small system like mine is it useful?
Majority of Aliexpress 7s (and 3,4,5,14 s) BMS have too high overvoltage protection, too low overdischarge protection and 4.2V balancing parameter (and low current balance around 50-60ma most of them) so what if I dont wire a BMS? Ive searched a lot on Aliexpress but I dont find any BMS with good settings.
4. Safety concern: I really want this system to be safe since I will not be everyday. So, I really want to find a good BMS but at a fair price compared to the size of this system.
For more safety I thought of putting a switch on the solar panel to stop the charge when Im not there, but it loses the interest of being fully charged when I come. Am I crazy to want to build a system like that and leaving it alone? Will Lead acid battery be more safe or the danger is the same?
Im sorry for the long post and if my questions are not very smart Im new to this.
By the way please excuse and correct me if you want my English
So first, what is my project? My project is to build a very small powerwall with a capacity around 200Wh to power a little cabin (very little house with no electricity, water and even no cellular network lol) to power some lights with solar 30W solar panel to charge it (small power because we dont stay more than 2 nights up there).
So I have the choice between Lead-Acid 12V 17 Ah which is cheap and 18650 cells which interest me a lot.
Firstly, I decided to do a 3s7p build but reading the forum I learned that we cant use it for 12V systems then I decided to make a 7s3p system but that brought questions:
1. What is the interest of having more in serial than parallel? I mean what if I build a 1s21p?
2. Ive seen a lot of 3s BMS on Aliexpress (same on ebay) and since 3s is useless what is the utility of them? same with 5s: these are very very cheap like 3 each but what is the utility of them, can I make a 5s system and use it as 12V with a converter?
3. Another BMS question: on a small system like mine is it useful?
Majority of Aliexpress 7s (and 3,4,5,14 s) BMS have too high overvoltage protection, too low overdischarge protection and 4.2V balancing parameter (and low current balance around 50-60ma most of them) so what if I dont wire a BMS? Ive searched a lot on Aliexpress but I dont find any BMS with good settings.
4. Safety concern: I really want this system to be safe since I will not be everyday. So, I really want to find a good BMS but at a fair price compared to the size of this system.
For more safety I thought of putting a switch on the solar panel to stop the charge when Im not there, but it loses the interest of being fully charged when I come. Am I crazy to want to build a system like that and leaving it alone? Will Lead acid battery be more safe or the danger is the same?
Im sorry for the long post and if my questions are not very smart Im new to this.
By the way please excuse and correct me if you want my English