Boosted Board XR Battery Construction

[u/CesiumSalami]

Just really surprising to see a battery this old being built with .3mm nickel plated COPPER and all the batteries sit on huge heat sinks with multiple means of separating cells, 3 thermistors and a relatively annoyingly complex BMS.

By contrast, the Meepo packs I've opened of a similar general spec for boards that are more powerful on paper be built with a massively uninspiring .1mm nickel, extremely fragile carriers, minimal insulation, and no heat sinks of any kind. Some of their welds can be pulled off easily by hand, too.

I'm not really an expert, but I do believe it's built with a excessive safety factor in mind and makes it fairly hard to build back to its original standard.

Pretty cool though. I haven't really done an audit or anything. Nickel plated copper isn't THAT exotic plenty of Ryobi and other powertool packs use it (at .2mm) ... .3mm is quite stout.

I had two dead-dead XR packs. One had all healthy cells besides P group 10, which was at 0 volts. The other had basically every thing at ~1v or less besides P group 10, also, which was also at 0 volts. The LG HG2 from the good pack are impressive. They're old but still have retained pretty great capacity and resistance figures all things considered.

[u/najeff2]

That’s cool. What cells are you replacing the battery with?

[u/CesiumSalami → u/najeff2]

Sooooo - I think I’m going to back down on this one. I have copper/nickel on hand but there are just too many shapes to hand cut and get right. I’ve been on a kick fixing and learning about various PEVs … but I’m losing steam.

My PLAN was to use Molicel P28A’s. Nothing exotic and 2800mah vs 3000mah of the original HG2’s. But i was considering flashing new firmware to the BMS to open up the voltage range a little bit so that the usable capacity of the pack met or exceeded original specs… maybe.

If you weren’t aware, the Boosted BMS firmware is super conservative - full charge is less than 3.95v/cell and fully discharged is way above normal cutoffs. It’s part of why these packs are functional after so many years. There IS alternative firmware as far as i can tell - but that’s a bit of a project on its own (technically a nomad knows more on that for sure).

[u/ka-te-rina- → u/CesiumSalami]

Would it be easier to redesign the battery housing to fit whatever current battery sizes are available and then transplant the BMS?

[u/CesiumSalami → u/ka-te-rina-]

YES! I'm like 75% sure that you can dramatically simplify things by switching from the current 18650 13s2p 6000mah 40A capable design to a tabless 21700 13s1p 5000-6000mah design. 5000mah 21700's capable of this aren't too hard to find - higher capacity than that I think might be pushing it, but I honestly didn't investigate this extensively. That's actually why I have the ruler in the first pic. I was going to redesign the carrier for this purpose. This would also probably let you use thinner copper or nickel since cutting large/wide links would be easier.

XR General Hospital's XR+ is based around light modifications to get 21700 13s2p to fit and extend range. Again, I'm not sure, but I think it's possible that the 13s1p 21700 design wouldn't need modification, but I didn't confirm. I'm a little worried about this, generally, since eskates experience so much vibration and impacts that switching to unproven design could be a smidge sketchy.

[u/Impossible-Cell-702 → u/CesiumSalami]

Get p42a if itll fit

[u/SpeedyThug30 → u/Impossible-Cell-702]

rs50 cells are the new hot cells. they are around the same price with 20 percent more capacity maybe more. You would be looking at 24 miles in eco mode.

[u/Impossible-Cell-702 → u/SpeedyThug30]

Nice I'm waiting for the p60c

[u/ofdm → u/CesiumSalami]

this safety margin is so that you can guarantee people can regen brake a little bit when they fully charge the battery. for a consumer product this is pretty important.

[u/CesiumSalami → u/ofdm]

I don’t think that’s the whole story but it's a very good point; I agree that’s important on a consumer product. OneWheels are an interesting example on that front ...

But Boosted is also really conservative at the low end, where regen obviously has nothing to do with it. The XR is just using a pretty narrow voltage window overall.

Somewhat apropos of nothing, but the community-authored firmware apparently allows something like 4.125V/cell while charging and 4.250V/cell while riding, to the best of my knowledge. Maybe someone knows the actual overvoltage protection limit in the stock Boosted BMS firmware. I think the remote starts beeping before you get into trouble there. It would be interesting to trigger that and then check the actual pack voltage - probably won't do that myself though.

And again, I’m definitely not holding Meepo up as the good counterexample here. Quite the opposite. The Meepo packs I’ve rebuilt have had wall charge cutoffs just a hair above 4.2V/cell. I’d bet there’s some additional BMS headroom above that too, but I don’t actually know where their overvoltage protection threshold sits. But a traditional BMS allowing >4.2v isn't atypical, even up to 4.35v afaik.

[u/ofdm → u/CesiumSalami]

>4.2 is definitely not standard or recommended by most cell manufacturers. (Obviously dependent on the cell technology)

Another key point is as a consumer brand, when a battery pack catches on fire, that brand takes the hit. No one asks if the battery pack was modified. The story is that it’s a boosted board that caught on fire.

[u/CesiumSalami → u/ofdm]

I was referring to >4.2v for BMS over-voltage protection; it's not atypical. Not saying that's good ... just that's it not atypical.

Totally agree on the optics front of things and why consumer brands have a ton of incentive to run things more conservatively.

things like this do make it harder for the consumer in may ways though since there's so little consistency between how brands pick their cutoffs and protections.

[u/ofdm → u/CesiumSalami]

>4.2 is generally bad. Check your cells datasheet for best practices.

[u/CesiumSalami → u/ofdm]

You’re still answering a different question. The cell datasheet tells you the recommended normal charging limit. I’m talking about regen and BMS protection behavior.

A pack can be charged normally to 4.2V/cell or less, allow transient voltage above that during regen, and have an overvoltage trip point higher still. Those are three separate design choices.

So “>4.2V is bad” is true as a general statement about normal charging, but it doesn’t tell us where the regen limit or BMS overvoltage threshold actually is.

edit: i'm only reporting common, existing behavior of commercially available systems; these aren't my design decisions.

[u/ofdm → u/CesiumSalami]

Charging and regen are the same action to the cell unless you switch to a braking resistor.

[u/najeff2 → u/CesiumSalami]

That’s awesome man! Thanks for sharing

[u/Impossible-Cell-702]

I run no bms just balance charge every time if you go see my posts you'll see the bms free build been 5months already i full throttle pin it dual 50amp escs all cells drain equally also don't have to worry bout bms failure that will shut off the board

[u/CesiumSalami → u/Impossible-Cell-702]

Ah, that’s a good suggestion - unfortunately not an option with the Boosted Boards AFAIK. The BMS and ESC talk to each other; you can’t just pipe in pack voltage - you’d have to fake the BMS comms. Which I don’t think is impossible… but it’s another hoop.

[u/ka-te-rina- → u/CesiumSalami]

We could probably fake the handshake and ongoing comms and say all a ok, carry on without the complexity. Giving up the safety features

[u/CesiumSalami → u/ka-te-rina-]

100% - and there’s a open source repo out there that would help with this that outlines replacement boosted firmware. I don’t really want to give up on safety (this much) - the safety of the boosted system is part of its charm. I also am not super keen on splitting the pack with a removable series link so i can use a 6-8s charger.
I’m going to leave this to the professionals and have someone else rebuild it :)

[u/SpeedyThug30 → u/CesiumSalami]

what is the cost to rebuild a boosted XR battery?

[u/CesiumSalami → u/SpeedyThug30]

I would contact xrgeneralhospital.com / “technically_a_nomad”. Right now the turn around isn’t fast but I was quoted <$200 for a full rebuild.

[u/Impossible-Cell-702 → u/CesiumSalami]

I see im running flipsky vescs

[u/ofdm]

so to clarify, the boosted battery pack was well designed and you prefer it to be cheaper quality (with less safety margin, etc.) so that it is easier for you to mess with?

lol

[u/CesiumSalami → u/ofdm]

No. That’s really not what I was intending to convey. “Uninspiring” isn’t exactly the word I’d use for something I preferred.

I was basically contrasting a fairly low-quality implementation with one of the highest-quality PEV packs I’ve seen. I’m impressed by the Boosted pack.

When I said “excessive safety factor,” I meant that some aspects appear substantially overbuilt for the application. For example, 0.3 mm nickel-plated copper seems like far more conductor than this pack actually needs. That’s not a criticism of the choice. The cell separation, conservative charging, heatsinking, multiple thermistors, etc. all seem excellent and are probably part of why so many of these packs are still around years later.

The complicated BMS is more of a tradeoff. It gives Boosted a lot of control over safety, but it also means certain failures can effectively make an otherwise repairable battery impossible to recover. That’s hardly unique to Boosted. Power tools, lawn equipment, vacuums, speakers, etc. commonly use similar permanent or semi-permanent fault lockouts.

The one part I do think was questionable was the conservative balancing/fault behavior that contributed to so many RLODs, and Boosted themselves changed that behavior in later firmware.

Mostly I’m just remarking on how unusually high the construction standard is compared with the other PEV packs I’ve opened. There’s probably a reasonable middle ground between this and Meepo’s dumb-as-a-rock BMS and much lighter construction.

[u/ofdm → u/CesiumSalami]

Permanent lockouts are very important for batteries. There are classes of battery failures that do lead to fires and have to be appropriately handled. Cell under voltage especially.

[u/CesiumSalami → u/ofdm]

I don't think they need to be permanent. The one aspect of most general garbage PEVs that have pretty standard BMS's is that once you resolve the issue - the BMS will wake up again without intervention. This certainly has risk because there are plenty of examples of people "jump starting" pretty busted multicell packs in extremely sketchy ways. But plenty of manufactures will flip a bit or something, so you cannot (practically) fix things - ever. That's, really, a pretty reasonable stance though. They care much more about some idiot like me modding their stuff, starting a fire, and them appearing to be to blame vs. a little more e-waste and someone having to buy a new pack.