"Mini Monster" 72V 120A 8Ah in a tiny package

SwampDonkey · Aug 15, 2019

I happened to get my hands on a load of Turnigy Lipo cells rated at 8000Mah and 120A discharge. The tabs were copper, so these were perfect for running in packs as they could be soldered quite easily. Im building this pack to run in two ways; through a 50A BMS, and full wide open 120A, bypassing the BMS and running like the large RC packs favored by high power users on a budget.

SwampDonkey · Aug 17, 2019

Coming right along! I went with 8 AWG silicone wire for the 120/160A leads, and 10AWG for the 50A/Charging leads.

999zip999 · Aug 17, 2019

What's it running ? Do these always come with two copper tabs ?

john61ct · Aug 17, 2019

Nicely done

SwampDonkey · Aug 17, 2019

999zip999 said:
What's it running ? Do these always come with two copper tabs ?

Yes, these have copper tabs on all of them. Solder sticks like glue, so putting them together was really easy. I have a Cyclone 4000W Scott Nitrous putting out about 6000W. I had to build another crazy big battery to power that thing. They new one could fit anywhere.

999zip999 · Aug 18, 2019

Are those the ones you have for sale ? Do you want to combine the two with the mini ? How do those 72v 16ah work ? What cells are in those blue packs.

SwampDonkey · Aug 18, 2019

999zip999 said:
Are those the ones you have for sale ? Do you want to combine the two with the mini ? How do those 72v 16ah work ? What cells are in those blue packs.

Yeah, those are the same ones. I suppose I could combine them for a much larger 24Ah battery and only have to charge once every couple of weeks. The blue packs are made with a long block of 12Ah lipos with a much lower discharge than the Turnigy. They were originally used in an EV of some type and came in a hard case. With the case removed I added a 10S 2P 4Ah set of Samsung 2700mAh (20 cells) with its own BMS and wired them in parallel. Each of those halves are 36V. The adapter puts them in series for 72V.

Hillhater · Aug 19, 2019

Im building this pack to run in two ways; through a 50A BMS, and full wide open 120A, bypassing the BMS and running like the large RC packs favored by high power users on a budget.

? Have you tested them ?
What is their rating ?..20C, ?40C ?
Even if these are the 65C rated packs,and they can actually unload at 120A, you can expect serious voltage sag and only a minute or two of run time...even at 50A you will struggle to get much more than 5 mins run time before LVC shut down.

SwampDonkey · Aug 19, 2019

Hillhater said:
Im building this pack to run in two ways; through a 50A BMS, and full wide open 120A, bypassing the BMS and running like the large RC packs favored by high power users on a budget.

Click to expand...

? Have you tested them ?
What is their rating ?..20C, ?40C ?
Even if these are the 65C rated packs,and they can actually unload at 120A, you can expect serious voltage sag and only a minute or two of run time...even at 50A you will struggle to get much more than 5 mins run time before LVC shut down.

Not at all, these are 15C BTW. The pack is done and I'll put some new pics up soon. I have 10gauge wire with an XT60 coming from the BMS carrying 50A, and 8 gauge silicone wire carrying the 120.

Edit: I just took it on a HARD run up some steep inclines. It ROCKS! Pulls insanely hard. Basically as much acceleration as you can handle on my 72V 80A Cyclone rig. Its amazingly light as well. We got a winner!

SwampDonkey · Aug 22, 2019

This thing is pure insanity! 8640W nominal, 13,440W MAX! I threw it in a backpack and charged up the biggest hills I could find on my 7000W cyclone-equipped ride. Its like there's infinite power on tap. It will snap your neck back when already going 30mph. This battery will show you what your high powered rigs will actually do.

Hillhater · Aug 23, 2019

Do you have data logging ?, a Wattmeter ?. Etc
How do you record those watt figures ?

SwampDonkey · Aug 23, 2019

Hillhater said:
Do you have data logging ?, a Wattmeter ?. Etc
How do you record those watt figures ?

Just math 120X72 nominal and 160 X 84 max is what the cells are rated for. It definitely maxxed out my controller and it blows away my much bigger 72V 60A battery. Controller only handles 72V @ 90A or so. Id love to see it actually tested. I'll just say its more than I need.

spinningmagnets · Aug 24, 2019

Do these always come with two copper tabs ?

Inside the cell, the positive cathode is aluminum, and the negative anode is copper. If the negative tab on a given cell looks silvery, it means the copper has been plated to reduce oxidation. If both tabs look like copper, the internal aluminum positive cathode collectors have been bonded to a single copper collector.

j bjork · Aug 24, 2019

Does some of the cells look puffy, or is it just the picture?
How much voltage drop do you have at full power?

SwampDonkey · Aug 24, 2019

j bjork said:
Does some of the cells look puffy, or is it just the picture?
How much voltage drop do you have at full power?

None of them are puffy, they're like bricks. That tape is tight, so it may look weird on camera.And Im not sure about voltage drop since I have no way of measuring it on the bike itself. I would guess none at all. I have several 72V batteries here including another big lipo (limited to 60A) and its easily twice the power.

If Im at 30mph and blip the throttle, it snaps my neck back with acceleration.

spinningmagnets · Aug 24, 2019

It is useful to apply compression to the sides of the flat foil packs....

Hillhater · Aug 24, 2019

SwampDonkey said:
Hillhater said:

Do you have data logging ?, a Wattmeter ?. Etc
How do you record those watt figures ?

Click to expand...

Just math 120X72 nominal and 160 X 84 max is what the cells are rated for. It definitely maxxed out my controller and it blows away my much bigger 72V 60A battery. Controller only handles 72V @ 90A or so. Id love to see it actually tested. I'll just say its more than I need.

Ahh, !.. OK, as long as you are happy with the result.
Just dont kid yourself that you are getting anything like those calculated wattages.
A $25 Wattmeter would tell the real story.

neptronix · Aug 24, 2019

$25 wattmeter would indeed tell us a lot.

Without a measured result ( and OP did not bench test his cells before ), we are lost in the woods as to the real power output.

SwampDonkey · Aug 28, 2019

neptronix said:
$25 wattmeter would indeed tell us a lot.

Without a measured result ( and OP did not bench test his cells before ), we are lost in the woods as to the real power output.

Id be happy to bench test. What would you suggest?

FaceDownWattsUp · Aug 28, 2019

*Throws money at the screen*
Take my money! Take it all!!!

Just how much good it fortune does a barely conscious primate on some insignificant speck of space debris deserve?
First there was fire, then the wheel, and then nonstick frying pans until finally, toiling up from the primordial ooze a fully evolved Swamp donkey, somehow managing to make that slimey and putrid ichor dignified. He wore that rotting plant mass like a dinner jacket and came bearing his miracles of awesomsauce, his gifts of complete badassery.
Amen

SwampDonkey · Aug 28, 2019

FaceDownWattsUp said:
*Throws money at the screen*
Take my money! Take it all!!!

Just how much good it fortune does a barely conscious primate on some insignificant speck of space debris deserve?
First there was fire, then the wheel, and then nonstick frying pans until finally, toiling up from the primordial ooze a fully evolved Swamp donkey, somehow managing to make that slimey and putrid ichor dignified. He wore that rotting plant mass like a dinner jacket and came bearing his miracles of awesomsauce, his gifts of complete badassery.
Amen

I really want to prove that these are every bit as savage as I made them out to be. Ive had quite a few 72V batteries and rigs that can support them, nothing compares. Nothing even comes close.

john61ct · Aug 29, 2019

So precise testing by a dispassionate trusted member is what's called for

SwampDonkey · Aug 29, 2019

john61ct said:
So precise testing by a dispassionate trusted member is what's called for

Well im in an area with tons of ES members, right outside of Seattle (Renton). If someone wants to test this thing out, Im game.

"Mini Monster" 72V 120A 8Ah in a tiny package

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