Thank for prompt replies.Sunder wrote: ↑May 08, 2018 7:41 amOh, I skimmed your link. I thought those were SLAs you were replacing. My bad.
If you were going to spend nearly $900 on that, I have a better way to spend your money:
3 lots of these: www.aliexpress.com/item/5pcs-Lithium-ti ... 78708.html = $264
These are genuine 12Ah, not 12Ah SLA replacements, so to build an equivalent one (5 cells) you're looking at 144wh instead of their 100wh.
Add one of these for safety - www.aliexpress.com/item/Customize-LTO-b ... 27973.html = $155
2 hours of soldering one lazy Sunday afternoon, and Bob's your uncle, and you can go electrified cycling with him.
For $419 - half of what you were going to pay, you get a battery 44% larger, and you can configure it however you please to get it between the triangle.
The balancing loom is usually included, but the charge and discharge wiring, you usually make yourself. It's always a good idea to individually charge and balance the batteries before assembly. The best way to do that is to put them all in parallel, and charge to 2.8v, and leave them there for a few hours. Simple and quick.sysrq wrote: ↑May 08, 2018 4:55 pmhttps://www.aliexpress.com/item/Customi ... 0.0.W9mVJO
I wonder if all the necessary wiring is included?
Hehe... "Back in the day" when I got out of high school pedaled a bike 1000+ miles in just over 6 days. Was "pedaling my butt off", eating four meals daily and still losing weight. Current rolling on a recumbent, but the force against aero grows as speeds increase? ... and not in a linear way, but increasing...@LockH - A bit overkill? I've done 100km in 3 hours without ANY power assist. Sure that's when I was training 3 x weekly for a triathlon, but with 350w, 80km in 3 hours is not granny cruising, but you won't exactly breaking a sweat.
Probably will use some voltage regulator. https://electronics.stackexchange.com/q ... le_rich_qa How powerful the charger should be in this case?Sunder wrote: ↑May 08, 2018 5:52 pmThe balancing loom is usually included, but the charge and discharge wiring, you usually make yourself. It's always a good idea to individually charge and balance the batteries before assembly. The best way to do that is to put them all in parallel, and charge to 2.8v, and leave them there for a few hours. Simple and quick.
Doesn't need to be exact, as long as it's over 2.65 or so, and preferably under 3.0v. Use a hacked USB charger with constant attention if you have to.
Getting away without some filling material like epoxy or something more appropriate to save weight would not be the best idea. Used to build some battery packs while working as a service technician for walkie-talkie company, not sure if I would do it again lol.Sunder wrote: ↑May 08, 2018 5:52 pmI'm also personally not a fan of punched holes alone in anything that moves. Fine for stationary applications. Fine if you have a piece of copper and some washers stiffening up the connection... But just the nuts and bolts straight through a thin tab, when your bike is bouncing up and down? I have zero proof it's not good enough, but there was one guy here who lost a battery after only a dozen rides, took it apart, saw the tab torn and blamed the assembly method. Again, zero proof that was the cause... But just common sense to me says I'd rather do it better. Stiffen up the join with something.
As far as I know almost any linear or non-linear power supply can be used in this case, it's just a matter of right voltage. Could grab any hefty transformer lying around and add some bridge rectifier with capacitor while monitoring the current.Sunder wrote: ↑May 08, 2018 5:52 pmAs for that charger... It's 2A. 0.16C... It'll take you 6 hours to charge from flat. These babies can take 10C, or less than 6 minutes charge.
Sure, you're not going to carry around a 120A charger, but 2A? You're buying a Ferrari, and insisting it stays in first gear. 350W discharge, ~80w charge... On batteries that can easily do 20-30x that rate.
Have only done 130km in about 5 hours on regular basis. Now aiming for e-assist in order to keep up against headwinds and hills while reducing dependability on weather.
15 cells x 12Ah x 2.4v nominal = 432whsysrq wrote: ↑May 08, 2018 7:57 pmHow long would it take to charge with this one?
https://www.aliexpress.com/item/420W-42 ... autifyAB=0
Probably an hour at least.
Will see.Sunder wrote: ↑May 08, 2018 8:13 pmFor initial balancing, doesn't have to be powerful at all. You just want to make sure all cells are at the same SOC.
Difference between 2.6 and 2.8v on most LTO is 5% SOC, so anything over 2.65v is fairly close. But if you try to balance it at 2.4v, you could be at 80%, or you could be at 20%, too hard to tell.
That's a rally high voltage pack there. Aren't transformers a bit too heavy to take on board? There could be some SMPS based lightweight ultrahigh switching frequency chargers.
Probably will have to wait for dedicated LTO charging stations.Sunder wrote: ↑May 08, 2018 8:13 pmMy main concern though, was current limiting. A normal wall socket can do 2.4kw. A 15A socket (common in shopping centres and stadium etc) can do 3.6, while a proper car charger can do 6.6kw. The battery I'm building has such a low internal resistance, it will soak up any of those, and more, meaning I'd trip the fuse/RCD if I don't limit current.
Probably not fully qualified to come up with the right answer in this case. There is no way of getting more power than it's available. Even when using light bulb trick it will have to be big for this application. Soft start circuits could be used if there are some current surges.
Even for LTO charging with low C rate will increase it's lifespan.Sunder wrote: ↑May 08, 2018 10:11 pmI was thinking the transformer would be fist sized, but now looking at the current I want, yeah, that's not going to work. To get to the currents I want, not only are they heavy, they're pretty expensive too.
My application is a motorcycle, not an eBike, hence the high power/voltage.
I currently have two high quality Meanwell SMPS delivering a total of 600w built into the bike. But SMPS isn't cheap, and get pretty big for the kind of power I'm thinking of too.
That's not a real issue. At the fastest a standard power point can deliver, I would be charging at 1/10th of what the LTO cells could safely take.