Leaving the BMS at home

[iamasalmon]

So I’m putting this here because I believe there is merit to this approach but since I’m just hacking away in my garage, maybe someone else has a better way. I’d like to create discussion around this topic, so please chime in with any experience you have.

I lurked for a long time here and other places before I charged headlong into battery making. I have professional experience with electronics, specifically running them in the ocean, down to depths of up to several hundred meters. After soaking up what information I could find, I decided I would try and route the balance leads off the board and be rid of the onboard BMS altogether.

I’m not going to cover the actual battery building here, but other threads have done better than I ever could.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=68005

Parts:
40 30q’s (±$150, depending on market conditions)
7 Pin waterproof connectors male/female panel mount ($35 or less/pair)
10 ft 12g silicone wire series connections, discharge leads ($11/10ft red+ 10 ft black shipped)
10 ft nickel strip ($5 shipped)
14g charge leads ($5)
20g silicone wire balance leads ($14/20’ spool)
JST 2.0 connector and crimps ($35/kit)
Adhesive Heat shrink tubing, assorted ($15/box, enough for several more projects)
60/40 electrical flux core solder ($10/spool)
Fish paper ($10)

Total just under $300 if it’s your first battery, after buying the spot welder and the soldering iron. I had some of this stuff already, so actual cost was lower.

My first board, I would simply open the enclosure to charge through the JST connector. If you run your boards with lipo packs, you’re probably doing this too. I basically built 2 5s 3p packs and wired them in series for a 10s 3p. I’d have to take it all apart to charge. Not the most elegant, but it worked, and more importantly, I found out that I freaking love commuting on a esk8 and it was very practical way to get around when combined with the trolley system here in San Diego. I present Frankenboard :

The second battery was much more refined in that the balance connections were routed off the board. Basically just routed the balance wires through a waterproof 7pin plug. I’ll post a link but others have found arguably better or undeniably cheaper plugs.

For this one I routed the balance wires and the leads for the series switched series connection into the deck and out a wooden panel. I did this to keep the enclosure free to pop off whenever I needed to dig into it.

Very scientific way of testing the water resistance of the assembled board.

not done here, but I have some lessons learned if you’ll take my word for it while I salvage my pics

pros

1. great way to get more info from the battery pack.
2. If you already have a hobby charger, it’s probably cheaper.
3. Leaves more room for batteries
4. Fewer failure points onboard

cons

1. very tricky soldering work involved. that middle pin is hard to solder without touching the neighboring pins.
2. Relatively inconvient to charge. Either charge one side at a time (safe) or charge both sides at the same time with two separate chargers. Duo chargers do not work, I killed 2.
3. The jst end of the charging adapter can be finicky, especially if cheaper wire is used. I’ve had to fix that part every few months for a cable that was made with fake silicone wire. Another one I made for a 12s (2x 6s in series) I made with nice wire and corformalled the crap out of it and it hasn’t broken yet…

more to come
(PSA: save your esk8 pics to the forum before your phone dies on you and takes them all with it )

[Agressivstreetlamp]

Sooo one 6s chargers and you’re charging half the pack at one time?

[iamasalmon]

yeap. ever since I smoked my duo by plugging both sides in without severing the series conmection. poof.

Untill then charging both sides on the duo charger worked great

now if I want to charge both sides at once, I need to get another charger out. then the series connection can be closed, no worries

[glyphiks]

You can get this charger which will do 2 x 6-12s batteries at the same time

http://www.ultrapower.hk/page9?product_id=126

I just did a trampa 12s8p liion as a single pack and routed a massive balance plug through the monster box

A lot of fiddly soldering and crimp work because I wanted the battery to be removable from the monster box and also needed to make an adaptor to suit the charger. But it’s an excellent charger and I really like this solution.

You can get smaller ports and plugs like the GX20, but they would definitely be harder to solder

My next approach will be for my Madness build, already have a BMS and charger for it, so I will combine those two together with a gx20 port.

[iamasalmon]

heck yes, I would love one if those. I saw that when you posted in the battery builder club thread and suddenly believe in true love

buuuut… an Imax B6AC is 30 sheckles and works fiiiiine…lol

I went with the split pack method because of how easy and cheap it is to get 1-6s chargers

also, I had to find a connector that was less than the thickness of the enclosure so the smaller plug fit better

[tipsy]

Did that on my board with a GX20, it’s not too hard to solder as long as you start with the middle pins, TS80 with the pointy tip works great for that.

Wanted to eliminate a failure point from the board, but ironically, my D140 arrived semi-dead.

[itsrow]

@tipsy

my D140 arrived semi-dead

Round of applause for Bestech QC everyone, not 1 mistake in 10 years.

[iamasalmon]

Update with salvaged pics (first post)

Also, I lurked around and found @visnu777 's beautiful builds

Grunstern

Grünstern - MOV-E shortboard, 12s3p NESE, Hummie Hubs, Hammock baseplates

Balance charge cables ready: [15607636248045770843406203491834] Now it’s basically ready to make it beautiful again I’m planning on replaceing the lid with something more Haya-Style, since its really tight with the NESE even though I removed 1mm from the original design.

and Blutstern

Blutstern - Rocket longboard, 10s6p, 4WD 58KV China Direct Drive

This time I use these with 12 pins In the Grünstern it is the 12 poles version from here: https://www.bulgin.com/us/products/range/circular-power-connectors/400-series.html plus a QS-8 for the main power lines. The new one is much bigger (more than double the size, looks like a electric car charger connector in small) but it is capable for 10A in the 12pin version. This battery is so huge I’ll never need the expansion pack, which was the reason for the big QS-8 on Grünstern, so I can use…

Question for @visnu777: Do you have the same charging cable for the two boards? Same charger? I’d love to hear more about your experience with this type of charging since you’ve been at this longer

[visnu777]

(Left side 10s (12pin, WF28, https://www.amazon.com/gp/product/B07B9RWDF6/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1) cable for the Blutstern, on the right the new Grünstern connector for 12s (14pins, SP28, https://www.aliexpress.com/item/32763647138.html?spm=a2g0s.9042311.0.0.bcbd4c4dxv000G)
I use the Graupner Ultramat 18. It is currently shipped for repair but overall I love it. I drive it with an external power supply with 3.8A@12s charging current. Recently I ordered an active balancer out of curiosity since balancing with the Ultramat takes some time

[iamasalmon]

What balance charger are you using?

[visnu777]

Preparing for a group ride later, carefully monitoring the cells manually.

[moon]

Bump. Charging one side at a time doesn’t sound terrible tbh

[javand]

Yeah I mean, I’d attach balance leads (jst) for a balancing board, but personally I don’t even plan to keep a charging/discharging BMS on my setup. It’s a waste of space and another failure point especially if you’re letting it handle discharge current, and none of the chicom BMSs are up to the discharge amperage we’re running, long term at least.

I always charge my packs with CC/CV power supplies externally. Balance as needed, separately. You can get some pretty large buck, or boost modules in the 1500w range (Chinese 1500w, so lets say 1000w to be safe) for around $25 all day long. Monitor it with a DMM until you know it’s safe, and worst case, use a high voltage, regulated bench PSU to top up. All that may sound convoluted, but trusting a Chinese BMS with all aspects of your pack’s management and safety sounds fuckin insane to me.

[moon]

Balancing board like this?

Active balancing boards

I just found this https://s.click.aliexpress.com/e/UWolwyK According to the specs this board start to balance the cells as soon as they get out of balance. So even if your board is not on the charger it will always be balancing. What’s your thoughts about it? Calling the bms master @b264 as well, your opinion is highly appreciated

[glyphiks]

I’m doing this for my demonseed battery. To use the dual 12s balance charger for a 13s pack. Not finished it yet, but there is no reason it shouldn’t work.

Its quite a bit of extra cabling and the way I am setting it up, i should also be able to use a 13s brick charger for when I’m on the road.

Once it’s all complete I’ll update here, but this is where I’m at so far…

6s6p and 7s6p 30q.

[SoCalLA]

I really like this. There is a simplicity to it, even though it involves more effort to charge your packs. I have used lipo packs in the past. And once you get accustomed to the process of charging, and get over the fear of starting a , it’s not a big deal at all. One other thing I like about it… I am a bit OCD. And whenever I’m using a pack with BMS, I always have the concern looming in the back of my mind: Is everything balanced? The way you are doing it, you pretty much always check the balance plug on a multi meter prior to charging. At least I do. And if a cell is a little off…easy fix. I usually just run a balance charge at about .5 amps, and things usually get back in line.

[javand]

I’ve only used the larger format ones, there’s a lot of new “active” balancers that use capacitors etc to transfer energy from one cell to another, instead of just burning it off through resistors. Some are better than others, and some aren’t even legit, but yeah, definitely my preference when possible.

I’ve got some larger ones I use for powerwall packs, that has Bluetooth and an app that lets you monitor the cells remotely and set various parameters, similar to this one: https://www.aliexpress.com/item/4000252216391.html?spm=a2g0o.productlist.0.0.1b9868fey52JKK&algo_pvid=2f6b3e64-f498-4730-a613-fe1721efa7f6&algo_expid=2f6b3e64-f498-4730-a613-fe1721efa7f6-11&btsid=0be3764515940162149588706e3309&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

[javand]

Yeah I agree, I mean, the RC crowd is already used to independently charging their packs, we’re using much of the same setup caveats, pack design strokes, etc, even down the XT connectors. Not a lot of standalone balancing chargers for packs of our voltage but, really no reason to rely on them.

I use modules like this: https://www.amazon.com/gp/product/B06ZZG2GPR/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

and this:
https://www.amazon.com/Voltage-Converter-DROK-Regulator-Transformer/dp/B076TTBKFG/ref=sr_1_4?dchild=1&keywords=1500W+30A+DC-DC+Boost+Converter+10-60V&qid=1594016676&sr=8-4

(both can be had cheaper on AliExpress or eBay, run roughly $20 each)

Keep XT60 and XT90 connectors on everything, and I can charge any packs, either from my large 48VDC off-grid packs that I use to power my cabin, or through various large power bricks, or server DC power supplies when I’m at my workshop in town, can be set to any voltage and current within the ranges easily, and work great if you de-rate them by 20-30% total wattage. 3D Print some cases, I keep certain ones set at certain voltages and amps, and they can run CC/CV directly to your pack through the same XT connector you have hooked up to your VESC, or a separate one if you prefer.

There’s tons of tutorials on youtube etc on connecting to Server PSU’s in series, floating one, and bam, you’ve got a high current 24v supply you can boost easily to charge these packs (or you can make a 36v one, etc), and others for anywhere from $20-40 total, and they’re top quality, reliable, high efficiency units built to last and manufactured en masse, for that industry.

Let the balancer do it’s job, occasionally, when necessary. Let the VESC handle discharging high currents as it’s designed to do, and if there’s some other scenario you’re concerned about it’s easy to integrate on it’s own, although adding so many component points of failure along the high current path, which is potentially tougher than the terrain and vibration on some.

I know nobody wants to be careless about battery safety, I agree we shouldn’t, but I wonder how many setups end up going up in smoke because of the BMS’s and other stuff people have crammed into their enclosures between the pack and the VESC in that high current path, not able to actually handle it long term and thus being the cause of the pack meltdown when it’s supposed to be keeping it safe.

I think in this regard we’re better off looking to the EV and high end car audio scene, and how they handle high currents safely, because we’re way more in that territory than RC, drones, etc IMO.

[glyphiks]

This balancer looks interesting. Do you know if it will work with a pack with wildly out of balance cells?

[javand]

Should definitely, although if somethings crazy crazy; like one cell is at sub-cut-off or showing almost no voltage, I’d revive it manually using regulated bench PSU and set the initial CC charge to like 100ma or something real low to start, just connect directly to that cell on both ends if you can reach it, get it back above normal cutoff voltage before running a full balancing cycle.

I’ve had great luck reviving cells that way, although if you’ve got one that’s constantly falling low, you may want to do a full bottom balance, and top balance cycle. Sometimes you may even need to overcharge a single cell relative to the pack to get it to even out, sometimes, you just gotta amputate and replace it though.