Theodore Voltaire
1 GW
Albert came back and said they're planning to use 21700 LG M50LT cells. Do you know if they're the same cells in your battery 1abv? The pack will be 20s 8p
E-S Stealth Electric Bike Owners
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That cell is a 10A max discharge cell. Nothing wrong with it, but at only 8P, that pack should only be drawing 80A max. Sure they might be able to do 100A briefly, but calling it 100A capable is a stretch.
There are a few other options with higher discharge rates, but most are lower capacity. The only cell with the same capacity and higher discharge is the new Samsung INR21700-50S (25A). It is however about 50% more expensive, so factor that in, but it would be my cell of choice atm.
Cheers
Also note that using cells at their max rates will generally have significant to high voltage sag, so you don't get as much actual power out as you would if used at a rate that doesn't load the cells as hard. For instance, with a cell that has a lot of sag close to it's max rate, you might get close to the same actual watts out of the battery when drawing 100A from the pack as at 80A, because the total volts would be so much less due to the sag.
If you go to battery testing sites like lgyte.info.dk you'll see charts for various cells that show their voltage sag vs current loading, to get a better idea of what you might want to do for a specific pack usage.
The cell internal resistance is the biggest contributor to this power loss. (also, the power lost in this fashion is retained as heat inside the cells).
If you go to battery testing sites like lgyte.info.dk you'll see charts for various cells that show their voltage sag vs current loading, to get a better idea of what you might want to do for a specific pack usage.
The cell internal resistance is the biggest contributor to this power loss. (also, the power lost in this fashion is retained as heat inside the cells).
Theodore Voltaire
1 GW
Yeah I was just doing research on these cells, and the more I learned about them the less excited I got. They're rated for 14.4 amp discharge, but only up to 77 degrees F. In the summer it doesn't even get down to that overnight. They drop down to 7 or 8 amp over 100 degrees which is where I live most of the time. Even riding at night it's 90 to 100 in the summer. On top of all the manufacturer doesn't recommend them for eBikes. I'm afraid Albert will have to go back to the drawing board.
Just the fact that these guys were recommending these cells make me hesitant to use them.
Thank you for the replies and solid advise CD, and amberwolf.
Just the fact that these guys were recommending these cells make me hesitant to use them.
Thank you for the replies and solid advise CD, and amberwolf.
Nupe I didn't have those mine were Samsung 50 somthin.. Works fine for my bike im still pulling 4500kw so may be different for you.
Theodore Voltaire
1 GW
Sounds like you have the same cells CW recommended, Samsung INR21700-50S with supposedly 25 amp discharge, and I think Alex has them in his wheelie machine too. At any rate they're a good substitute for the LG cells. I ask Albert if he can use them instead, and he said he can, but they're a little more expensive. I'll give these guys credit, they're trying meet my requirements, and responding promptly to my replies.
Question for the brain trust? They're planning to use a 100 amp BMS which I know is leaving some power on the table, but I don't really see myself ever going more than 100 amps, and maybe only 90. My question is, will a BMS of that size be reasonably dependable for a 20s 8p pack?
TV, that cell only became generally available towards the beginning of this year...so not sure if others would have used it before.
As for the 100A BMS, it really depends on the BMS they use. A lot of the generic bluetooth BMS I use are more than capable of exceeding their rated limit briefly, if their config allows and as long as temps are monitored. As with most cheap electronic stuff you generally do want to exceed your general usage levels by a margin.
That being said, with your kind of riding on the street TV, I would have no problems setting it up at the 100A limits. It's us off-road hooligans that generally cook stuff.
Cheers
As for the 100A BMS, it really depends on the BMS they use. A lot of the generic bluetooth BMS I use are more than capable of exceeding their rated limit briefly, if their config allows and as long as temps are monitored. As with most cheap electronic stuff you generally do want to exceed your general usage levels by a margin.
That being said, with your kind of riding on the street TV, I would have no problems setting it up at the 100A limits. It's us off-road hooligans that generally cook stuff.
Cheers
Theodore Voltaire
1 GW
Thanks CD that's reassuring. Yeah, half the time I'm just putting around at relatively low speed. Blasting at full speed is the least kind of riding I do. I'm sneaking up on 70 yrs old, so I don't get too crazy anymore, but here in Dallas on the big streets 35 means 45 to 50 for most drivers. Sometimes I have to deal with that..
They're going to try and find a 120 amp BMS that will fit, but I told them if that's not possible I can live with a 100 amp.
amberwolf, this is my new 80W soldering iron which is similar to the one I borrowed for soldering those big wires on my Kelly controller. Now that I have a little experience I expect to do an even better job on the Nuc.
They're going to try and find a 120 amp BMS that will fit, but I told them if that's not possible I can live with a 100 amp.
amberwolf, this is my new 80W soldering iron which is similar to the one I borrowed for soldering those big wires on my Kelly controller. Now that I have a little experience I expect to do an even better job on the Nuc.
The BMS current limit should be lower than the cells can take.
The BMS is intended to protect the cells; it's the reason to use one, so all of it's limits should be such that the cell limits are never exceeded (preferably such that the usage never comes near the cell limits, with the BMS shutting off output if they do).
The BMS's FET rating should be MUCH higher than the system will use, so that you have plenty of current capability for surges, spikes, etc (such as charging caps in the controller at connection or power on, which is a VERY high current for just a moment), with no risk to the FETs.
(when BMS FETs do fail, they usually fail shorted, stuck on, so that the BMS cannot protect your cells against overcharge, overdischarge, overcurrent, etc., and it is a silent failure, so you do not even know this has happened until something severe enough happens to the cells that it affects the ride enough for you to notice).
The *controller* has a current limit that must be below what the BMS limit is, so the controller does not trip the BMS or attempt to overload the pack / cells. If it is a controller capable of more than that, it needs to be programmed not to do so. Then the controller will simply limit current once that has been reached, and the system continues to operate at that limit.
If you depend on the BMS's current limit to protect things, then everytime you hit it you will lose all power. Can make riding suck, and under street / traffic circumstances could be fatally dangerous.
The BMS is intended to protect the cells; it's the reason to use one, so all of it's limits should be such that the cell limits are never exceeded (preferably such that the usage never comes near the cell limits, with the BMS shutting off output if they do).
The BMS's FET rating should be MUCH higher than the system will use, so that you have plenty of current capability for surges, spikes, etc (such as charging caps in the controller at connection or power on, which is a VERY high current for just a moment), with no risk to the FETs.
(when BMS FETs do fail, they usually fail shorted, stuck on, so that the BMS cannot protect your cells against overcharge, overdischarge, overcurrent, etc., and it is a silent failure, so you do not even know this has happened until something severe enough happens to the cells that it affects the ride enough for you to notice).
The *controller* has a current limit that must be below what the BMS limit is, so the controller does not trip the BMS or attempt to overload the pack / cells. If it is a controller capable of more than that, it needs to be programmed not to do so. Then the controller will simply limit current once that has been reached, and the system continues to operate at that limit.
If you depend on the BMS's current limit to protect things, then everytime you hit it you will lose all power. Can make riding suck, and under street / traffic circumstances could be fatally dangerous.
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That soldering iron is the newer model of the one I use for hefty connections, etc. Just make sure you always let it heat up to temperature first before touching it to the stuff you need to solder, and once one thing has been soldered, wait until it has reached full temperature again before going on to the next one.
Theodore Voltaire
1 GW
I think Albert said the 100 amp BMS can handle a 300 amp surge for very short duration. The battery pack works out to 200 amp on paper, with 360 amp short term ability, again on paper. I'll need to keep these things in mind when I get around to programming the nuc.
Theodore Voltaire
1 GW
I'm very lucky to get this kind of high level assistance. I don't want to start naming names because the list is long, but you guys know who you are, and I thank you all.
I've personally seen where a controller (BAC4000) did not react quick enough to protect a battery pack hence when Amberwolf says that the controller should be set lower than the BMS he is 100 percent right. That way you have double protection.
Theodore Voltaire
1 GW
I've known to consider this when setting the LVC, but it's never been a issue for the max current until now. I'll keep this in mind when I get around to installing the nuc.
Theodore Voltaire
1 GW
I know how much you guys love dirt. I don't always make videos riding on dirt, but when I do, I do it with one hand.
Theodore Voltaire
1 GW
Rix
100 TW
Thats very un TV like.
Theodore Voltaire
1 GW
Do you ever look for any gold nuggets out there?
Theodore Voltaire
1 GW
Since the side covers don't say B52, I'm guessing either the side covers were replaced, or it's the very first B52 Model, probably early 2014. B52 should also have Magura MT5 brakes.
Is it just me or does that screen look misaligned and the buttons smushed over? I would be asking about that.
shap08
10 mW
- Joined
- Sep 16, 2019
- Messages
- 26
I think its a shadow. It has pretty low KMS for such an old model, he still wants $7,000 for it.
Battery would be coming up to 10 years.
Is that USD or AUD? If AUD that isn't too bad. If in Australia I can build you a replacement battery.
Cheers
