Need some Help.. new battery pulling huge watts.

[Incorp01]

Hi
Need some help.
I have a CYC X1 Pro Gen4.
X12 controller.

Today I fitted a new battery
TFL branded.
48V, 20AH, 40A BMS, Samsung 50E 13S4P.

It’s allowing me to draw almost 4000w.
When testing with my 52V Em3ev battery, it shuts down at the correct ~1900w, so I think the display is accurate.

Faulty BMS?
Will these batteries in this config even allow this kind of draw?

 

[neptronix]

4000w / 48v = 83A.. almost double of what the battery's peak output limit ( 40A ) is.

You need to run a little less than half the power you're trying to pull. If the BMS didn't intervene, your battery pack would catch fire from heat generation, since it can't handle this.

 

[E-HP]

40A is already slightly higher than the max discharge of those cells, so I wouldn’t count on the BMS providing current protection. If you can’t limit via the controller, then the battery is relying on you to do that job.

 

[docw009]

I would assume the display is right, so your battery is putting out 80A momentarily. The 50E has been tested at 20A. See this link. It gets hot really fast.

I've installed a number of small BMS, 15A-20A, for space considerations, They will pass 25A with a 25A controller, so I've always assumed the rating is based on current rating for the MOSFET's. That could be a wrong assumption for bigger units, but I think current limiting is a pretty stiff and expensive requirement.

 

[Chalo]

Bottom line is that BMSes don't usually limit power; they only have a power limit rating. Your controller will have to limit power if your motor system doesn't naturally hit its own limits.

 

[E-HP]

Bottom line is that BMSes don't usually limit power; they only have a power limit rating. Your controller will have to limit power if your motor system doesn't naturally hit its own limits.

I wouldn’t rely on them. I only had a BMS trip once. The current peaked at about double the rating. Is that short circuit protection kicking in, or voltage sag causing the trip?

 

[Papa]

40A is already slightly higher than the max discharge of those cells, so I wouldn’t count on the BMS providing current protection. If you can’t limit via the controller, then the battery is relying on you to do that job.

Humans make mistakes, including me.... so I rely on inline fuse(s) at the supply source.

 

[nicobie]

Me too. It seems that lots of people depend on their BMS (battery murdering systems) when the right size fuse will work.

 

[Chalo]

Me too. It seems that lots of people depend on their BMS (battery murdering systems) when the right size fuse will work.

I find that fuses are the most frequent source of failure in well cared for batteries. I bypass them if they give any trouble whatsoever.

That said, I wouldn't use a battery with a motor and controller system that could exceed the battery's rating. Just like I wouldn't use a motor with a controller that had the power to burn it down.

 

[Papa]

I find that fuses are the most frequent source of failure in well cared for batteries.

Millions of motor vehicles... literally, still employ plug-in fuses. Many of which are plugged into exposed sockets. The 'failure' rate is almost non-existent. I use and recommend enclosed fuse holders to inhibit contact corrosion. Never had a 'failure' in 2 decades of ebike builds.... nor an ebike component loss due to shear stupidity.

That said, I wouldn't use a battery with a motor and controller system that could exceed the battery's rating. Just like I wouldn't use a motor with a controller that had the power to burn it down.

Obviously, many inquisitive individuals who frequent this site, don't posses your electronics savvy - especially when swapping components.

Marine grade fuse holder - 4ga $17 or 8ga $12.

www.amazon.com/New-DS18-Hydro-MFH8-Accessories/dp/B0858F9457?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&smid=AL09J9CKIG9A&th=1

 

[Chalo]

Millions of motor vehicles... literally, still employ plug-in fuses. Many of which are plugged into exposed sockets. The 'failure' rate is almost non-existent. I use and recommend enclosed fuse holders to inhibit contact corrosion. Never had a 'failure' in 2 decades of ebike builds.... nor an ebike component loss due to shear stupidity.

Well, I guess you don't use mini blade fuses in inappropriately high amp values and plugged into very cheap crappy holders, like, well... pretty much all Chinese e-bike battery makers do.

I'm used to seeing 30A mini blades tucked inaccessibly inside battery cases or else exposed and bedraggled in the discharge leads. And I'm also used to seeing burned sockets with intact fuses in them. That's not helpful to anyone.

If I incorporate a feature whose sole purpose is to make my bike NOT work, I'm going to need a very good reason to do that. So far I don't have a reason that good.

 

[leffex]

If the rating on the bms is 30 what I have seen recently in the specs is that they tripple the short time maximum current draw from what have been only double before to my knowledge. The time and allowance may span from a few seconds to two minutes before it triggersand it can also havr two trigger points and shorter time as amps go higher. Note: This is all assumptions from my experience and reasoning!

I have had auto fuses go or kind of half gonot working properly. Also the auto stic bms function I have had the power cut for about 5 seconds, enough to cut the power on my moped so as to make it work again you would have to wait or disconnect the main fuse to get it going again.

I tweaked the amp settings so that's why I know.

 

[Incorp01]

I would assume the display is right, so your battery is putting out 80A momentarily. The 50E has been tested at 20A. See this link. It gets hot really fast.

I've installed a number of small BMS, 15A-20A, for space considerations, They will pass 25A with a 25A controller, so I've always assumed the rating is based on current rating for the MOSFET's. That could be a wrong assumption for bigger units, but I think current limiting is a pretty stiff and expensive requirement.

Thanks,

How does this work, the link is showing graphs with draw of 10, 15 and 20amps for this cell.
I thought this cell was rated at 9a continuous.

Is there a formula to workout what that equates to like 9amps multiplied by the configuration 13s4p.

 

[rafalg]

Would be a little dangerous to have power cut off suddenly when riding. The controller should limit the current but not cut off completely like the BMS/fuse

 

[Incorp01]

40A is already slightly higher than the max discharge of those cells, so I wouldn’t count on the BMS providing current protection. If you can’t limit via the controller, then the battery is relying on you to do that job.

So, with this pack, is the 4P in 134P, how the discharge amps are calculated?

I think they are rated at 9.8A? So 9.8X4 (39A) should be safe for the cells?

 

[E-HP]

When the pack is new. It won’t be new long if you’re pulling 40A. The BMS will eventually trip, after you’ve abused the cells for a while. I’ve only had a BMS trip twice, and pulling twice the rating. It would run well above the rating when climbing hills for short distances, so my conclusion is the BMS is the last line of defense, with your brain being the first line.

The trade off of using high capacity cells is lower discharge ratings and more voltage sag when pushed. The benefit is high range when used within their capabilities. If you’re plan is to run higher current, then you should choose higher performance cells, with lower capacity/range as the trade off.

If you look at a good pack, like the ones by EM3EV, the BMS is rated well below the discharge capacity of the cells, so it still offers some protection as the pack ages (and definitely doesn’t start out higher than the cell ratings).

 

[docw009]

Thanks,

How does this work, the link is showing graphs with draw of 10, 15 and 20amps for this cell.
I thought this cell was rated at 9a continuous.

Is there a formula to workout what that equates to like 9amps multiplied by the configuration 13s4p.

Samsung says it will pass 9.8 amps continuous and meet the minimum life requirements in the datasheet. Nothing stops it, or any other cell, from going higher. It will get hotter and life will be shorter. Go too high, and it can get so hot that it vents and the CID, current interrupt device under the positive cap, will open, It's interesting that they say 9.8 amps, not even 10.0 amps.

(P number) x (AH of cell) is your formula. Maximum safe current for the cells is 39.2 amps, but it doesn't consider the wiring in your bike or the wiring and nickel strips in the battery.

 

[Incorp01]

Samsung says it will pass 9.8 amps continuous and meet the minimum life requirements in the datasheet. Nothing stops it, or any other cell, from going higher. It will get hotter and life will be shorter. Go too high, and it can get so hot that it vents and the CID, current interrupt device under the positive cap, will open, It's interesting that they say 9.8 amps, not even 10.0 amps.

(P number) x (AH of cell) is your formula. Maximum safe current for the cells is 39.2 amps, but it doesn't consider the wiring in your bike or the wiring and nickel strips in the battery.

Thank you so much for taking the time to explain this to me.
much appreciated.