yeah the converter is not a terrible idea but in order to deal with similar power levels, it would really need bigger components. Not quite sure why raphael seems to want to make everything so small? But for looking into usb3 a converter will probably be needed, and some smarts… There are ofc other ways to get the same function but it’s always nice to have a brain box in there somewhere.
Also, in this size, balancing cells is for sure something that battman could do but in order to deal with the heat, it could take a looong time for an extreme case. Though i don’t see this as a problem, since it can keep doing the balancing and protect the cells at the same time, so even if you plug in a pack that has one cell at 0% and one at 70%, charge for an hour and go riding? it’s only managed to balance a bit say it’s at 100% and 35%, the charge will stop at 100% and the ride at 0% for each cell respectively. After, the balancing continues so the next time it will have sorted it.
I considered using one or more of those TP4056 modules. The issue with using more than one is that they have a common ground on the input and output sides, which means each module would require an isolated power source unless the individual cells of the battery can be separated while charging. (And if I use 3s or 4s lipo packs to construct my 12s battery, there’s basically no way I can isolate all the cells from each other.)
This was what led to my idea that I could use one module and cycle between individual cells. But I’m not sure if there are any easy ways to make that happen automatically…
Just use a DC DC step up module to 50V.
Lets say you use a 5V 1A charger, that would lead to less (cause of the losses) then 50V 0.1A. This could be done easily but is very slow!
Are there any 12s BMS or balance chargers that can be set to only draw 0.1A?
Also to be fair, many USB power supplies are able to supply 2A or more of current. Computers aren’t the only power sources with USB ports. But even charging at just 5 watts overnight, that would still add about 2 miles of range. Considering I live within a couple miles of several friends’ houses that I stay the night at, this still seems like a useful function to have for me.
OP noted that in the first post … and those of us that want this are okay with that … or may even prefer it…for reasons outside the scope of this thread.
Who cares how slow it is. We’re talking about how to make it happen …
Fair enough. My personal needs might have skewed the usefulness of this charge speed, as my work trip in one direction is a bit over 7 miles, so it just wouldn’t have made sense to me, but now that you mentioned your scenario with a bit more detail. I can start to see why you could get actual use out of it.
The other factor nobody considers is multiple boards. What if I have 5 boards ready to go and I want to slow-charge the one I just got back on over multiple days? The OP noted in first post that “slowness” is not what the thread is about, but more so how can this be accomplished. There are so many off-topic reasons. Solar charging. Compatibility with everything else that uses USB. Availability of charging locations.
Are you implying you will let your board charge during the night while you are asleep ? If the answer is Yes, you may be put yourself and your friend’s house at risk, fire risk.
Well, there is slow, like the op noted, and then there is slow. Like i stated above, in order to comply with usb 2 specs, it might take more than a week to charge a 400wh board.
(And while it might be nice to get enough juice to get home again, somewhere i’d guess if it’s close you might have the capacity to make a round trip anyways and if it’s long you could bring your normal charger… But thats beside the question )
if you just want to charge your board, one of these boost converters will probably get you close. Though i’m not quite sure how they would perform with such a big voltage boost, or what they would do with such a limited current input to such a “high” output current. But assuming you find a module that does manage to produce the voltage you need then my guess is that it will just work. Otherwise it’s pretty simple to create a constant current circuit.
This is also assuming that you first do some testing to verify that you wont burn up the usb you connect to and that you have a BMS… though the bms is more a style point here, since the actual chance of the battery getting full are slim. But it should nonetheless be there.
But still, if you want to be able to charge anywhere, id probably go for supporting most 12-24V wall warts instead, it’s almost the same circuit and odds are that it will get you ALOT more charge.
I’m certainly no electrical engineer, but could you use one of those, plug it into the wall and connect say 3 usb cables from it to something that combines the power output from those 3 cables? So assuming you then get 30W, based on your previous statement of 5Wh achieving (approx) 0.5KM/0.3m every hour, this could do something like 3.0km/1.8m every hour.
Above is assuming 100% efficiency though, however even if i halved those numbers it’s still viable for charging at work as part of a commute.
I also think i could probably find a larger watt USB charger, however the ones above are cheap and compact.
The beefier A-type -connectors can usually deliver rated maximum of 2.5 Amps, so you would still be at 12.5W and not sure if the ports could be paralleled up, but then you would have to make a custom USB cable anyway that could handle the current.
The biggest limiting factor with using normal USB to charge is the low voltage that needs to get boosted very high, but USB type C connector with PD would start to make sense, but needs communication ICs to be able to charge at higher voltages. And of course an USB PD capable charger, which then I would already ask why not carry a dedicated charger for the board? Put a 5V buck regulator on the board and charge your USB devices from that
I have a scenario in my head that you need to help make happen…
I get into work on my board, everyone looking dreamily at me wishing they skated in.
Then i ask to “borrow” USB chargers off people, claiming i forgot mine.
I combine them all in my PC and maybe the one next to mine (he’ll never know).
I can then charge the board back up enough to razz around the park at lunch, harassing dogs and such.
Yeah sure i can do that with a charger, but the stupid ponces need a sticker on the brick that says it’s passed a safety test, and the guy that does that isn’t in till August or something.
Make this thing Muff master Simos, you know you want to.
Yeah, that’s kind of my thoughts aswell… If anyone wants to try charging from one usb, then by all means get a boost converter like the one i linked above. Same problem with the high current usb chargers like @riva_00 linked. Sure it can be done, but then you’d need to bring that charger instead. If you want portable, something like this is also pretty small. And slowish. you could go for one with even lower current too if you can find one?
For the single cell chargers like the one @lrdesigns showed, the question is not only if you have different chargers, you also need chargers that have an isolated ground, otherwise it will cause a short anyways. BUT, if you wanted to go down that slightly silly route or ten chargers, you could also just series them to get one 50V, 1A source and (maybe) add some current limit in order not to overload them. But for cheap(also for not-so-cheap) usb chargers it’s very common that they drop in voltage under load, meaning that the current would regulate itself. That would be one UGLY usb cable though! And you’d be pretty guaranteed to fry something sooner or later when you plug it into the wrong port.
Btw @riva_00, would they not be more upset if you plug in a wire mess diy abortion of a usb charger than if you just smuggle you normal charger in?
Sure, except that USB C with PD brings with it completely new can of worms to contend with and we still need to most likely boost the voltage higher for +6S packs. PD is a pain to implement, because it needs PD specific implementation and communication between charger and load.
Well, if we’re talking a custom board then might as well support PD… the code and ics used in the tindie boards looked simple enough, outside of that that is needed is to be able to set charge(if thats desired to be a feature) current and a enable signal to the boost circuit. Maybe it would even be possible to have a usb3 PD charger with support for snail charge on usb2?? THAT would be COOL.
i looked at the tps43060, looks nice except for the package… any reason you chose that over others? Switching regulator design is certainly not my expertise but it’s pretty damn interesting
