SubnetMask
1 mW
- Joined
- Apr 17, 2020
- Messages
- 19
I'm fairly new to to the lithium pack building 'scene', although I've been working with electronics for many years, so the basics are pretty simple. Building a 7s4p pack in the simplest of layouts, 7 long by 4 wide, is, well, simple. But I'm faced with a pack that I want to build where I'd like to build a 7s4p pack that I can't fit a 4 wide pack in. Originally, I was going to make a 7s3p pack (because that's the 'p' I could fit in the simplest layout), but I got to thinking that I'd like to add more runtime, so enter 7s4p (The application is a 24v 120W scooter that originally had a pair of 12v 4.5Ah SLA batteries in series - a 7s4p would roughly double the runtime of the original SLA batteries). My plan for the pack is, as usual, a 7s BMS to prevent over discharge and be an additional layer of protection against over charging, but the layout of a 7s4p pack in a 3 high layout took me 'a bit' to figure out, which is where my question comes in. I started with a monochrome 'drawing tablet', which I couldn't get figured out, so I broke out my daughters crayons (lol) to add color, and came up with this:
Of course this may be a case of 'ask six people, get eight answers', but is there anything 'inherently wrong' with what I came up with? I'm not terribly worried about current as based on my calculations, at 24v, the 120W motor would pull 5A at most, which is right at the amp limit for the cells I'm using (I'm planning on using LGABB41865 for this pack), meaning a 7s1p pack could 'technically' do it (but with half the runtime of the original 4.5Ah SLA batteries), but a 7s4p pack would be running at around 25% of its 'rated max current', so far from risky. Just wanted to run it by the experts here to make sure there wasn't something 'dumb' about how I laid it out that was either 'really dumb' or simply could be improved upon.
Of course this may be a case of 'ask six people, get eight answers', but is there anything 'inherently wrong' with what I came up with? I'm not terribly worried about current as based on my calculations, at 24v, the 120W motor would pull 5A at most, which is right at the amp limit for the cells I'm using (I'm planning on using LGABB41865 for this pack), meaning a 7s1p pack could 'technically' do it (but with half the runtime of the original 4.5Ah SLA batteries), but a 7s4p pack would be running at around 25% of its 'rated max current', so far from risky. Just wanted to run it by the experts here to make sure there wasn't something 'dumb' about how I laid it out that was either 'really dumb' or simply could be improved upon.
