I would charge to full and try to discharge to 3.0v the first couple of cycles – that way the BMS readings are closer to accurate — but you’ll learn how much is left at certain voltages ( the BMS is not perfect % reading ) As long as your layers are staying in balance , that’s important — Store the pack with cells at 3.8 - 3.83 – you might have to charge higher for the cells to settle at 3.82 ( don’t use the % reading ) Also set your BMS to balance above storage voltage 3.9 or so — If to low it will make your storage voltage drop — If possible set to balance only when charging
Unfortunately the cells only have a ~5A discharge rate so no bueno. I made sure in my post to only include cells that will meet the discharge rating that the manufacturer says is necessary…but whos to say it actually is…and if they are using cell holders well…then I have my doubts.
Regardless every cell I listed was at least 10A and at least 3000mAh. The 3000mAh cells I listed were often 15A cells and the few under 3000mAh are 20A cells or better.
But yes, BatteryHookup has a little bit of something for everyone.
I wonder what it would be like to use SPIM08HP cells inside that scooter…
I’m a certified diver and I would not risk using these power cells in a scooter while on a dive. I know they are degraded just seeing people post testing results and I simply couldn’t trust them but dang is that tempting to put together a pack of these…maybe order double the amount you need, test them all for capacity and IR and then put the best ones in the scooter after you cycle them 10 times to confirm there’s nothing going on with them
It’s a tricky business, scooters. You want it to be reliable, and to have maximum runtime. But then you also have to balance those things against size and weight and heat management.
The scooters I have (a DiveX BlackTip Tech and the Genesis 2.2) could easily hold way more cells inside the body. But, that would increase the overall weight, which means that once you get it in the water, you would never be able to get it to neutral buoyancy. And, really, you want it to be just a little bit positively buoyant, so that you actually need 1 - 2 pounds of lead added to it to make it neutral - in salt water.
Adding things like lights, nav systems, a compass, cameras, etc, all typically add negatively bouyant mass to the scooter. You take lead out of it to compensate, so it can still be neutral with those things mounted to it.
The scooter designer has to decide how much negative buoyancy they want to be able to accommodate and then design the size of the scooter and the weight of the batteries, etc., to give that much positive buoyancy. If they make it even bigger, it will accommodate more stuff added to the outside, but it will be heavier in its bare form (when lead is added to make it neutrally buoyant in bare form).
And then there’s also the issue of having the battery pack designed so that the batteries can be adequately cool, even when diving in warm water, while running the scooter at full throttle for an extended period. I think the battery cells ideally have some air space around them.
It’s a serious balancing act on the part of the scooter manufacturer. I think the Genesis is very well designed in pretty much all regards. Thus, I am reluctant to upset the balance by trying different battery packs, for example. I don’t have any need for more runtime. It is now neutrally buoyant with 1.4# of lead inside. I’m adding a nav unit with speed sensor, and probably some light mounts. I expect to get it where it is still neutrally buoyant and floats in good trim. Once done, I don’t want to mess with it further. I just want to go play with it!
Ah I was unaware this was made out of 6061 Aluminum. Looking more into the specs and not just the battery this thing isn’t a toy for open water divers this thing is a tool for people with serious advanced certifications like cave diving!
Length – 24.5in (61.7cm)
Max Thrust – over 90lbs (41kg) [400N]
Run Time at Max Speed – 50 minutes
Run Time at Min Speed – 16 hours
Approx. Range at Max Thrust – 2.7mi (4.3km)
Approx. Range at 2 knots – 6.4mi (10.3km)
Approx. Range at 150fpm – 8.7mi (14.0km)
Standard Depth Rating – 660ft (200m)
Optional Depth Rating – 1000ft (300m)
Li-ion Battery Capacity – 850Wh
Battery Voltage – 64.8VDC nominal
Charger Input Voltage – 100-240VAC
Recharge Time – 4 hours
So that’s the specs on the 850wh model. If full throttle depletes the battery in 50 minutes and I did my math right thats a draw of 1020 watts at full throttle. With 72 cells that’s about a 14W draw per cell. Obviously with the larger 144 cell pack that’s only a 7W draw. So either 4A or 2A per cell depending on the battery size you are using.
Why in God’s name are they forcing you to use the NCR18650GA? You could get much cheaper cells with 3000mAh or more that have at least a 5A discharge rate. Now I would only advise doing that for the 144 cell pack. For the 72 cell pack a 4A draw on a “10A” cell is the sweet spot. It allows you to go full throttle until the battery dies and the cells should only heat up to about 40 Celsius and I’d imagine there’d be some cooling effect of the water on the aluminum case.
Here’s a graph showing 4A discharge
Don’t get me wrong, I understand the manufacturer is being extra cautious by choosing what most people agree is the best 3500mAh cell (although the differences between it and the LG MJ1 are minor ever since the MJ1 got a slight tweak a few year ago)…but they’re using cell holders so I just have trouble taking that seriously. Don’t get me wrong, its amazing that they want to make this user serviceable but Jehu Garcia did a few videos on what the limiting factor was for his PCB powerwall design (this battery pack is probably directly inspired by Jehu’s design)…and that limiting factor is how the cells are attached. Keystone cell holders all the way! Even though they are pricey. And for anyone reading this the newer Keystone cell holders that have silver contacts have more resistance than the gold colored ones. I bought some of the new ones just to test that.
Honestly this is my worst YouTube video on my channel because its 26 minutes of me rambling and not having all the stuff I wanted to test…maybe I should redo it.
But you get to see just how bad the cheapo cell holders are compared to the Keystone…and even then the Keystones add enough resistance that any sort of “power” cell can never actually be used as a power cell because there’s too much resistance in the leaf springs.
Check out how hot the el cheapo cell holders get
So anyways now that we’ve identified the actual specs of the motor inside (based on hopefully accurate battery information) it leaves the door open to someone NOT being boxed into NCR18650GA’s. There’s nothing about the cells that make them all that much different from LG MJ1’s…Samsung 35’s have an 8A max discharge rate but in the 144 cell battery that would be fine, in the 72 cell battery…meh I’d rather an actual 10A cell. But this really opens up the possibility of using the new Vapcell 4000mAh cells…
That is once someone does a full life cycle of them and we see they are good for several hundred cycles with a normal degradation curve…and then wait another year to make sure no one has any random defects or anything. Obviously being well past the 120’ limit of open water diving takes using lithium ion cells safely into a whole new realm. Although I do wonder what the additional pressure would do to a cell down at say 300’ if it were to go into thermal runaway and then be ejected outside the aluminum housing (that part is totally hypothetical)
First, so, yes, that’s me. 100 meter full trimix Open Circuit and CCR and full cave Open Circuit and CCR. And yes, this is not a scooter that really makes sense for the average open water diver to buy. I also have a Dive-Xtras BlackTip scooter. That is the scooter for an open water diver. But I digress…
That is great analysis!
This scooter is meant to be able to convert back and forth between 850 and 1700 W-Hr. I suspect the manufacturer specs the cells they do for a couple of reasons. One, they want to use the same cells in both battery packs, to facilitate switching between small and large packs and also supply logistics. And, two, this is meant to be the BEST scooter on the market. Using cells that are deemed “the best” seems like a requirement for two reasons: One is pure marketing. “We only use the BEST components.” And, two, they don’t want to ever see someone posting online about how they had a scooter failure 10,000 feet back in a cave and then saying “they cheaped out on the cells in this battery pack. We probably wouldn’t have had this failure if they had used NCR18650GA cells instead of trying to save a few bucks with these other cells.”
Also: The current version of this scooter sells for $10,650. The batteries used cost $700 - probably less when purchased in the bulk that the manufacturer does. If some other cell is HALF the cost, it’s only going to save $350. I’m guessing the real world savings would be way less than that. I don’t see the manufacturer having much incentive to worry about saving that much money on an $11K scooter. Not when that little bit of extra money allows them to say “we only use THE BEST.”
Also also, I don’t know what the consistency is on the less expensive cells. I got 147 of these NCR18650GA and 144 of them were at 3.50V. 3 were at 3.51V. That is some pretty amazing quality/consistency, in my book. That consistency probably allows the manufacturer to build whole battery packs without bothering to test individual cell voltages before installing. Just the time savings on that would make up for the extra cost.
The user manual for this scooter has a couple of power graphs. Basically, it shows the scooter burning about 1150W at full throttle. But, at normal cruising speeds, it’s only using 150 - 300W. They claim that the scooter will run at full throttle from fully charged to fully depleted (well, 15 or 20% or something like that) with no problems. But, the reality is that the scooter has so much thrust, it’s pretty dang unlikely anyone will ever really be running at full throttle for very long at a time. And it basically has the most continuous thrust of any consumer-spec scooter on the market.
So, I think the losses from using non-welded batteries are totally acceptable and a good tradeoff for the end user being able to swap cells on their own.
I put a full set of batteries in this one for $700. In comparable scooters from other manufacturers, that all use proprietary battery packs (i.e. spot welded), a pack with comparable energy can run up to $5000. There is one company making scooters in the same ballpark of price range and intended use. They use Dewalt power tool batteries. Their “biggest” model will accept 4 x Dewalt FlexVolt 12 A-Hr/18V batteries. They are $250 each, so $1000 will get you about half the capacity that I have in the Genesis for $700.
I really do not have any idea how it would go to be at 300’ and have one of the cells in the scooter go into thermal runaway. It would still be 1 atmosphere of pressure inside the scooter (until the hull is breached and floods). I imagine a fire would consume all the oxygen inside the scooter pretty quickly. I don’t know how lithium fires work. But, unless the reaction is producing its own oxygen to sustain itself, I would think it would burn itself out before it breached the hull or melted the sealing O-rings at either end. So, from the diver’s perspective, hopefully it would just stop running and leave a major mess to discover after getting out and opening the scooter.
My expectation is that these cells will last me at least 5 years. Could even go 10. At that point, if it costs me another $700 to put in all new “best” cells, I’m okay with that!
Howdy, folks. I have a follow-up question on this.
The XiaoXiang BMS app on my iPhone shows what appears to be buttons at the lower left that say “batt off” and “batt on”.
I’ve been afraid to touch them for fear of effing something up that makes me have to disassemble the whole pack.
Can anybody confirm what those do?
Specifically, this battery pack has a charging lead that doubles as an On/Off switch. It has 4 pins. I can connect the charger/power supply to it to charge. Or, I can install a cap that makes some connections (inside the cap). Without the cap on, the scooter won’t run - but I can still talk to the BMS via Bluetooth.
When the scooter is stored, I’m supposed to remove that cap from the charging connector to stop parasitic drain on the battery. Meaning, it only has the parasitic drain of the BMS. I guess the motor controller creates additional drain when the charging connector cap is installed.
I’m wondering if I can use the Bluetooth app to do the same thing as removing/installing the charging connector cap. I.e. if I tap on “batt off”, is that going to cut all power to main output leads? And then I can still go in at any time and top on “batt on” to turn it back on?
Does anybody know? Is this the kind of thing where only the manufacturer of the battery pack could really say for sure?
It would be great if I could leave the cap on the charge connector on at all times, to protect the 4 pins there.
Yes – you can turn the BMS Off and back ON with the App — All that charging cap you speak of is doing is connecting 2 pins together that normally have a On/Off switch connected to — Yes there’s still a Parasitic Drain even when it’s off – I don’t think it’s that much --Just monitor it to be safe
I also emailed the manufacturer to ask the same question. And, I was pleased and surprised to get an answer back last night.
They say that the BMS MOSFETs will leak a bit even with the BMS off.
So, if the battery pack is connected to the motor, then I should still take the charging cap off, to disconnect the motor, even if the BMS is off.
So… there you go.
Thank you again for all the help!!
There are companies that recycle the metals from Lithium batteries. Maybe you can find one close to your location.
Thank you for that.
So, I gather there is no monetary value in cells like these junk 18650s?
Nothing like when I was a kid and we could pick up glass bottles and turn them in for 5 cents a piece or anything like that?
Assuming the US is same as UK, probably not. A lot of the value comes from the ability to store energy and as these are shot, and possibly dangerous to charge, there’s not much use for them.
I don’t think anyone is offering to pay for scrap lithium ion cells (yet), unlike Pb-acid, which is widely recycled. I’ll be pleased to be corrected though.
There’s a lot of noise made about e-waste but no real solutions, a deposit scheme might not be a terrible idea…
To me – They’re a Hassle to get rid of – Not every place is eager to take them
In San Francisco people can leave batteries in plastic bags on top of their weekly garbage can and the garbage company will take them. A number of local hardware store will also take them.
Imagine the guys faces when there’s a bag of 144 cells on top of the garbage can!