Hey y’all- New guy here looking to tap into the wealth of battery building smarts on this board. I’m not a esk8r or such but I found this board when I was researching 48v battery packs for my project. Seems like the esk8 battery packs are very close to what I need.
I’m building a portable ventilation system that will be carried into the field in order to cool down small structures for 4hrs at a time during the heat of the day. I’ll use off the shelf 48v DC fans that use 200-300 watts of power. My contract specs my runtime to be 4hrs (max) on one fully charged battery pack so I’m thinking a 12s8p is the way to go. Looks like these are fairly common on this forum.
My question is about selecting details for a custom 12s8p pack. I really don’t need more than 6A of draw but it does have to be continuous for 4 hours before the pack cuts off at low voltage. I won’t need an ESC because the DC fan has it’s own built in BLDC controller and motor so straight 6A @ 48V is all I need. What type of 18650 cell is recommended? Or is 18650 even the right type of cell? Any special BMS considerations?
Lastly but not a deal breaker if not possible, I need to be able to ‘pull’ the battery pack out of the ventilations system so it can be carried back and recharged by itself. I may have to build this myself but hopefully someone knows of a pack system hat is designed to be removed for charging.
A 12s7p with such cells should land you in the 1300wh range, and should definitely deliver over 1200wh of energy since you’re going to be under 1 amp per cell.
Thanks, @Evwan, that’s the kind of info I’m searching for here. I’m open to 21700 or even other types of chemistries (the customer doesn’t care) but I’m just not too savvy on batteries in general. My background is electrical engineering so I follow all the technical discussion but that doesn’t mean I can put together a safe battery pack in my garage (at least not for the time and price I can have one custom made). Any yeah, those Samsung 50E’s are a good price— only if someone here has the materials to make a battery pack for me. Same with those INR21700’s- those seem too good to pass up.
I started with the RC airplane world looking at using 120mm electrical ducted fans (EDF’s) to be the ventilation system but those set ups are mainly for high amperage, short duration flights. I need low amperage, long duration with a LOT of watthours to be the most efficient— y’all seemed to have figured this out already.
@J0ker - I’ll need one or two packs by Mar and if the customer likes the first prototypes after some field test, they’ll order another 4-8 more by the summer. So yes, looking for someone or two interested in participating in this project.
This might be what you need, check the dimensions and form factor. It’s a pretty solid and robust brick, but it’s not designed with inserting/removal in mind. If you want to go with us, leave an order note and i can add some extra FR4 insulation/reinforcement on all sides of the pack to make it more robust for that use. Adding a handle or strap would be up to you.
The fans have an operating input voltage range of 36-60v with 48v being nominal. I’m in the process of characterizing these fans for cfm output vs. power (or v) consumed so I can find a sweet spot that maximizes battery life and design. From the little bit I’ve seen so far, bumping up the v (and amps) past 48v doesn’t add a whole lot more cfm so yeah, I’m sure a 12s battery pack will work for my initial prototypes but I’m not sure it’ll be the optimum solution. Regardless, Duck’s bricks look pretty slick as a good starting point.
@DuckBatterySystems Does your pack have the low voltage cutoff built into your BMS? The fans I’ll use have a built-in ESC without a low voltage cut out so if I’ll need to add another component between the brick and the fan.