And if you could switch between 6s X2 in parallel and series for 12s for range or speed, that’d be cool
The problem is: if both batteries get drained differently the vesc doesn’t know about that, it just has the overall cutoff. That’s why I used the lipo voltage warner and will also build something similar for the main battery 
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Fits in my backpack well and having the cord come out of the right side with the cable retractor connected towards the plug seems to work well too for keeping the cable out of the tires when crouched. My wife says it looks stupid so I’m not going to try to get pics. I’ll probably only use it when I really need it.
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I take your point on changing the title, though the original intent was to directly plug a matched 2s battery into the loopkey of my 10s to make a series connected 12s…
This does work but is a shitty and inelegant workaround that if misunderstood could blow some shit up.
The boost converter through charge port is the way I’m headed now.
Thanks @mmaner I missed the posts till now.
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Those are one and the same. Increasing voltage, OR increasing amp hours will increase your range. What actually determines range is the watt-hour rating of the battery which is voltage times amp hours.
People have probably seen people describe their boards as “consuming x amount of watt hours per mile” because that’s a universal range rating. As long as you know the Wh/mi, the voltage, and the amp hours, you can know the exact range.
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I get that, but as the example above. You have a 10s pack, then add 2s to the loop key. You can only add a similar capacity size battery as they have to drain evenly. Its not much watt hours you can add.
But if you connect to the charge port you can add any size watt hour battery.
I’d just like to point out that a battery connected to a loop key port connected in series with the battery is probably MUCH safer than a battery hooked up to a charge port. On a charge port you need to worry about using a boost converter, and worry about unequal discharge of the packs (your boost converter will need to have a low input voltage cutoff)
By connecting pack in series with the loop key port, you only need to worry about three things:
- Your vesc being tuned to have min / max voltages that account for the voltage boost
- Your packs starting at relatively the same capacity (just have a little headroom in the low voltage cutoff)
- Making sure your boost pack has the same rated amp hour rating as your main pack.
As long as you follow those three rules, there is no additional risk (besides having another battery outside of an enclosure, but the charge port method also suffers from this)
On a separate note: Yes, @lrdesigns you’re right about the capacity limit. You should not exceed 12S, so you can only boost voltage so much. But for boards that are running on 8S or less, this is a great method.
That’s not enough, only if use the same cell that was subject to a similar load across its life
Internal resistance changes a lot, they can have the same capacity and still discharge at different rates
That’s why is never recommended to mix new and used batteries
But do like @visnu777 and monitor both internal and external packs and you should be good
Huh… I like the title change, but realized maybe this whole topic could just be range extenders speed boosters or something along those lines. But the title isn’t a big deal, it’s pretty fitting ATM.
Now that we are talking the difference between plugging into the charge port vs loop key (or maybe now that I’ve started paying attention), it seems like both have benefits.
I want to figure out a way to keep my range extender plugged into the charge port, and also have the option to plug in a speed booster into the loopkey port. I am thinking since the loopkey speed booster isn’t connected to the BMS, and won’t be extended by the charger (right?) that it could safely be 1-2P larger than the rest of the pack, or even double, to ensure that it won’t die when the rest of your pack is being charged. Or, would the pack plugged in after the BMS still be charged with the rest of the pack, just not balanced? Then again, all this is making me want to just build a 12-13s 8-9p pack and be done with it.
Hence why I said leave some headroom on the low voltage cutoff
I’m merging conversations here, but headroom for however many S in voltage you are boosting with… ?
I’m going on my third beer, doesnt this defeat the purpose to begin with? I do get this makes sense with differing internal resistance though. Forgive me for combining conversations… I’m asking if you are charging your main pack and not your voltage boosting pack at the same time.
I’m not saying that much, probably 10% of the total pack capacity including the booster would be fine.
Ideally, just stick an RC low voltage chirper on the booster pack.
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Before I go forward, I want to get the community’s thoughts on my plans to see if there are any blatant issues or dangers with what I want to do. I want to do the original range extender this thread was based on (but as a voltage/speed booster) plugged into a loop key, in addition to my current range extender plugged into the charge port.
My current 24v power tool battery swapping mechanism to boost converter (42v 5a) plugged into the charge port works great for my 10S4P 25r 10Ah battery… And I intend to keep this at the same time as having the voltage boost option in the loopkey… I’m assuming this will be fine, charging 10S at 42V while boosting the output of all that with another 2S pack that’s not being charged.
Now, I want to splice a loop key into the red wire that leaves the pack and plug either a loop key or a 2S18P pack of Samsung 30A (6a discharge / charge = 108A, need so many P to not stress the cells and provide at least 80A to match the rest of my 10S4P packs max output) It would be a 45Ah pack based on my testing of each cell.
I would maintain 10S voltage cutoffs and just keep an eye on my 10S batteries voltage via the % lcd on the pack and my power tool range extender’s voltage monitor connected to the 10S pack, and rely on the BMS cutoffs as a fallback if those fail me somehow or I get blackout lazy for some reason (not expecting this…)
I would monitor the voltage/% of the 2S18P voltage boosting loopkey pack separately with another external voltage display, and being 45Ah I don’t anticipate it draining even half before I can fully recharge my main battery with all the external batteries I have. This I think will have the benefit of not needing to charge the “speed boost” pack as much and/or maintain a higher voltage slightly for the duration of my rides.
For charging, I don’t intend to use any kind of BMS, instead have two barrel connectors, or 3/4 bullet connectors and just connect these to contacts in a 3d printed 18650 sized shell that I will simply slot into an 18650 charger to charge the whole pack at 2amps. I’d expect this to take forever, but I’m not trying to buy a fast 4.2/8.4v charger /2S 80A BMS.
Since all the 30A cells are spot welded in 3p groups, I was going to connect 6x 3P groups with 14awg silicone wire, soldered to the nickel strips, and solder 10awg wire for the positive and ground to the entire pack and to connect between the two large P groups.
The idea is that I can carry this pack in a padded 3D printed case that I can clip onto the top of my board, disconnect the antispark loopkey and plug in this pack to the same port to instantly boost from 10S to 12S when someone wants to race or something. Do you all see any issues with any of this? I’m curious how well this will work, or if it will work at all.
As convoluted and crazy as all that is, I’m pretty sure it will all work.
In the spirit of the original post on this thread, I’ve decided to make a 1S voltage boosting pack to get a tad bit higher top speed and maybe a bit more range while I’m at it. I’ve documented the build here: https://www.electric-skateboard.builders/t/the-demonseed-tb-218-tb-6374s-190kv-tb-mounts-chibattery-10s4p-dual-focboxes-superflys/50610/99?u=skatardude10
Bench tested it and it works great. The extra voltage makes my board sound mean and scary. Ahh!! Glad I didn’t boost to 12S, I like my gearing and speed where it’s at.
Boosting voltage this way, instead of capacity, is very dangerous.
I hope you have some way to verify the packs are balanced and know if any P-group falls below a cutoff voltage.
The thing to note here is he did it through a loop key. Making a 10s into an 11s. Junk cells in a giant 1s1p config works I guess. If a cell dies it’s not much of a loss.
If the focbox is not configured, this may cause high voltage cutoff. Future readers beware.
The main packs BMS low voltage cutoff per P group, main pack battery percentage meter, and a secondary main pack voltage/watt meter. So the main pack I have 3 ways to monitor as voltage gets low, and it never really gets too low since it’s always charging.
For the big 1S pack, all the cells are wired in parallel and should balance each other. The packs voltage is monitored with a 1S low voltage alarm set to 3.2v cutoff.
As for my vesc low voltage cutoff, I don’t plan on running the 1S pack when the main 10S packs voltage drops below 36V since I tend to get sag, and don’t want to sag below 28V when the resting voltage reads 39V with the 1S pack, since the vescs low voltage cutoffs are set to 28-30v for 10S.
Good enough, or do you think I’m missing something?
Plugged in, the voltage is less than 12S, 46V both main and secondary battery fully charged. My high voltage cutoff is set to default at 57V I believe.
Pack works. See post on build thread: https://www.electric-skateboard.builders/t/the-demonseed-tb-218-tb-6374s-190kv-tb-mounts-chibattery-10s4p-dual-focboxes-superflys/50610/100?u=skatardude10
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