24v small lightweight for kayak validation/suggestion

[lopezjo49]

I'm a real noob. Been watching a lot of diy solar vids. I'm looking to make a small 24V (required for motor on yak) around 40-100ah. Should be more than enough for my needs on lake. Not looking for long-term storage. Portable, lightweight but will last me several hours is the goal.

I was thinking 8x 20ah lifepo4 and wanted to make sure I'm calc correctly. If I make the 2x12v (4s) the put them in parallel I should end up with a 24V 80ah correct? @$27/cell about $220?.?. Not including BMS, box, some wire of course.

 

[rmaddy]

Parallel adds the current. Series adds the voltage. So two 12V batteries in series would be 24V. But if you buy 8 cells, why not just build an 8S battery to get 24V? No need to make 2 12V batteries if you want 24V. And 8 20Ah cells will give you a 24V 20Ah battery, not 80Ah.

What are your power needs? A 24V 20Ah battery won't last long depending on how many watts you will be powering with it.

 

[lopezjo49]

Parallel adds the current. Series adds the voltage. So two 12V batteries in series would be 24V. But if you buy 8 cells, why not just build an 8S battery to get 24V? No need to make 2 12V batteries if you want 24V. And 8 20Ah cells will give you a 24V 20Ah battery, not 80Ah.

What are your power needs? A 24V 20Ah battery won't last long depending on how many watts you will be powering with it.

The raw cells state 3.4V 20ah. So I thought make a 24V using 8 cells total as you said. 4S would make them 12V 80ah then putting each in series give me 24V 80ah no?

 

[rmaddy]

As I said, series adds voltage, parallel adds amps. Your 3.2V 20Ah cells in 4S (series, not parallel) gives you 4x3.2V 20Ah = 12.8V 20Ah. In 8S you get 25.6V 20Ah.

 

[lopezjo49]

As I said, series adds voltage, parallel adds amps. Your 3.2V 20Ah cells in 4S (series, not parallel) gives you 4x3.2V 20Ah = 12.8V 20Ah. In 8S you get 25.6V 20Ah.

Oh sorry yes I see now. Thank you. I should prob shoot for the 60ah then. I'm looking for the 24V and between 40-80ah. Thank you for keeping my math honest.

 

[rmaddy]

How many watts does the motor use? How long do you need to run the motor between battery recharges? That will determine how much battery you need.

 

[Rocketman]

Be sure and calculate the weight of all those cells. I made a 12v 50ah battery. By the time you make 60ah 24v - you may longer consider it “small and light”

 

[lopezjo49]

How many watts does the motor use? How long do you need to run the motor between battery recharges? That will determine how much battery you need.

Per manufacture. It's 480w at full throttle, 20A. 200w at 60%. Using 15ah batt you get about 1hr of full throttle per their chart Others that I know have 2x 12v Dakota 54ah are getting more than a day's use. Esp. with it only being used intermittent, on long runs, then I peddle or paddle.

I was looking to see if I can get around the 50ah at 24v for less and smaller than what I see is avail. The most intriguing I've found so far on here is the battleborn 24V 50ah

 

[rmaddy]

24V 50Ah would be 1280Wh. Assume about 80% usage so 1024Wh. If you ran full throttle (480W) that would last 1024Wh / 480W = 2.13 hours. Or you could run 60% (200W) for 1024Wh / 200W = 5.12 hours. Obviously you can get a full day with some intermittent use. So 24V 50Ah seems like a good size. The BattleBorn 24V 50Ah weighs 31lbs.

 

[lopezjo49]

24V 50Ah would be 1280Wh. Assume about 80% usage so 1024Wh. If you ran full throttle (480W) that would last 1024Wh / 480W = 2.13 hours. Or you could run 60% (200W) for 1024Wh / 200W = 5.12 hours. Obviously you can get a full day with some intermittent use. So 24V 50Ah seems like a good size. The BattleBorn 24V 50Ah weighs 31lbs.

Yeah I feel like most of 24V 50ah packages seem to be about 30lbs,. Roypow 24v 50ah also about the same but not sure of the quality. AliExpress is so intriguing but makes me nervous.

 

[Rocketman]

Because you are around water - highly consider that aspect in the battery - sealed as well as possible. (Something I sure you were very aware of).

 

[rmaddy]

Because you are around water -

Since this is for a kayak I would say the water is around them.

 

[lopezjo49]

Since this is for a kayak I would say the water is around them.

Yeah batt is generally put into a battery box that is sealed with a rubberize through connector like sae connector or using something like Anderson sb50 75amp for connector bused on something like a winch. There's a large battery box market for yaks but most are 12V.

 

[mitiempo]

Yeah batt is generally put into a battery box that is sealed with a rubberize through connector like sae connector or using something like Anderson sb50 75amp for connector bused on something like a winch. There's a large battery box market for yaks but most are 12V.

What motor are you using? Minn Kota for example is 12 volts up to 55 lbs thrust - surely you do not need more than that for a kayak?

 

[bgflyguy]

I just saw this after reading this thread. Might be worth some investigation.

SUPER BEAST 24v 48ah 1.23kWh Lifepo4 - 48 HEADWAY CELLS

You get 48 Headway cells plus you get all the 300a busbars, wiring, and cells holders. This is by far the best deal on Headway cells. Now lighter and a little cheaper to ship as well. The modules are confirmed to be balanced and fully functional. This is a pure power module. Connect this one...

batteryhookup.com

 

[lopezjo49]

What motor are you using? Minn Kota for example is 12 volts up to 55 lbs thrust - surely you do not need more than that for a kayak?

Nope. Newport nk-180s. It's 24v. It's about efficiency doesn't really equate to power 12v vs 24v

 

[yakfish]

Nope. Newport nk-180s. It's 24v. It's about efficiency doesn't really equate to power 12v vs 24v

I just purchased this same motor. What battery did you end up going with?

I was originally thinking I'd just buy cells and build my own diy battery in a box, but then acquiring 50Ah cells from AliExpress seemed like a gamble and would take forever... 2 of the Zooms 50Ah 12v batteries.

I'd really like to fit the setup along with a Bluetooth shunt, into a harbor freight/pelican case, with some waterproof ports, to keep all the actual batteries protected and make it easy to mount/unmount/charge, without a bunch of extra wires/shunt and worrying about getting them wet. The batteries are slightly too big to fit in the mid size harbor freight case.

Since I probably would have a hard time finding 8 decent 50Ah prismatic cells shipped to me for much less than the price I paid for these Zooms... I'm considering tearing them down to see if the contents would fit wired in series in there, and/or reconfigure with an 8S BMS. Curious if you or anyone has done something similar.

 

[yakfish]

I just purchased this same motor. What battery did you end up going with?

I was originally thinking I'd just buy cells and build my own diy battery in a box, but then acquiring 50Ah cells from AliExpress seemed like a gamble and would take forever... 2 of the Zooms 50Ah 12v batteries.

I'd really like to fit the setup along with a Bluetooth shunt, into a harbor freight/pelican case, with some waterproof ports, to keep all the actual batteries protected and make it easy to mount/unmount/charge, without a bunch of extra wires/shunt and worrying about getting them wet. The batteries are slightly too big to fit in the mid size harbor freight case.

Since I probably would have a hard time finding 8 decent 50Ah prismatic cells shipped to me for much less than the price I paid for these Zooms... I'm considering tearing them down to see if the contents would fit wired in series in there, and/or reconfigure with an 8S BMS. Curious if you or anyone has done something similar.

Opened it it. Looks quite a bit different than the 50Ah AmpereTime that Will tore down.