quick battery drain in 1500W engine motor

Joined
May 10, 2022
Messages
4
hi forum Guys,

I have following setup:

-Front Motor wheel 1500W engine,48V Brushless Non-gear Hub Motor, 540RMP,35-45NM
-KT 18 mosfet controller
-48v 100Ah battery,3-parallel 13-serie, 18650, 39pcs,Nominale 30A, Momentane 90A,Samsung NCR 18650 35E 3500mA

The issue I have that when switch to health power(750W), battery last only for 10Km, if used on full power(1500W), I can drive only max 5Km.

Is this normal for this battery capacity? Per my calculation, it should have 136,5Ah if all cells charge to full.
 
Cas_blue_pianist said:
-48v 100Ah battery,3-parallel 13-serie, 18650, 39pcs,Nominale 30A, Momentane 90A,Samsung NCR 18650 35E 3500mA
<snip>
Per my calculation, it should have 136,5Ah if all cells charge to full.

Unfortunately, it's not nearly that high a capacity.

You can only add the single 3p together to get the Ah capacity, not all of the cells together. Cells in series do not add to capacity, only to voltage. The single smallest parallel group determines the total capacity of the pack.

So if the cells are 3500mAh, then 3 x 3500mAh = 10500mAh (10.5Ah). That's one parallel group, which is also the capacity of the entire pack, becuase all the other paralleled groups of cells in series with that group drain at the same time at the same rate because they're in series.


To get a 100Ah battery with 3.5Ah cells, that's 100 / 3.5 = 29. So you would need to have every one of the 13 seriesed groups of cells be at least 29 cells in parallel, meaning a 13s 29p battery (which would be huge). That would be a total of 13 x 29 = 377 cells.

To get the 136.5Ah, you'd need 136.5 / 3.5 = 39 cells, for each parallel group. That would be 13s 39p, which makes a total of 13 x 39 = 507 cells.

Assuming 50g per cell (from here: https://www.imrbatteries.com/samsung-35e-18650-3500mah-8a-battery/ ), that's 507 * 50 = 25350g, or 25.35kg (almost 56lbs).


Also note that to get the absolute full 3500mah you have to run the cells from completely full to completely empty, which is hard on them, so they wont' have as long a lifespan; additionally they'll get unbalanced easier, and more often, as they age quicker from this.

Additionally, if your controller has an LVC for a 13s pack, it will shut off before you have emptied the cells, which is normal. So you wouldn't get full capacity of the pack unless you disable this (or it doesn't have an LVC, or the LVC is set lower than the BMS shutoff point and the BMS shutoff point is at the completely empty point of the cells).


It's also harder on the cells to use them near their max current capabilites, though your system doesnt' appear to be doing that.
 
thanks You for this calculation. So in fact, 13 series in 1 row mean that we have total voltage 13*3,7V=48V, which is right with my engine 1500W which support 48V. and capacity is only 3*3500mA, ok. so if I want to have higher capacity and still use 39 cells, I would have to connect them differently, like 5 series with 7 battery which will give me 5*3500mA=17Ah and total voltage of 26V(7*3.7V). so in fact, I would have twice stronger battery with higher capacity but I could use it only for engines with 26V.. I attached what was tested by seller for this battery, however it is in Chine language - do U think U could find out what those nr means? I guess 4952=49V, 1000=1000W, 119,7=11,9Ah?

https://ibb.co/xG1h3sr
 
Connecting them differently won't give you more energy capacity. You have a certain amount of energy stored in the batteries in your battery pack. Changing between series and parallel connections does not magically give you more energy storage, it just changes that parameters of how that energy is delivered.
 
Cas_blue_pianist said:
so if I want to have higher capacity and still use 39 cells, I would have to connect them differently, like 5 series with 7 battery which will give me 5*3500mA=17Ah and total voltage of 26V(7*3.7V).
so in fact, I would have twice stronger battery with higher capacity

Unfortunately, you still don't have any more capacity that way. There is more Ah, but now there is less voltage, so there is less Wh (which is the "real" capacity).

17Ah x 26v is actually *less* Wh capacity (442Wh) than 10.5Ah x 48v (504Wh), so you would get even *less* range than before.

The only way to get more capacity is to add more cells in parallel to every group (row) of the 48v battery.

Theoretically you could instead add more series groups (rows) of at least the same number of parallel cells to make a higher voltage battery, but this means changing your controller/etc out to handle the higher voltage, and since you need ten times the capacity you have to get the capacity you're after, you'd need a 500v battery, controller, wiring, motor, etc., and I don't think that's the direction you want to go for this.


The only "simple" way to get the capacity you are after is to basically add 9 more batteries like you already have, in parallel with the one you already have.

Then you'll need to modify your bike to be able to carry a battery that huge and heavy; most likely you'll need to split the battery up into at least two sections and put them in side panniers on the rear. (a single battery that big probably won't fit in any one place on the bike. Even if it does fit it will probably cause you handling problems trying to ride).




but I could use it only for engines with 26V.. I attached what was tested by seller for this battery, however it is in Chine language - do U think U could find out what those nr means? I guess 4952=49V, 1000=1000W, 119,7=11,9Ah?

https://ibb.co/xG1h3sr

The numbers are pretty clearly marked with standard units in the image for the first three things, but the forth and fifth are in another language I don't understand. You would have to ask the person that took the picture to tell you what they mean.

However, the information in the picture is completely useless, because it has no context; it does not show you what is being tested, what tests were run, or what conditions the tests were run under. Without *all* that information, there is no meaning at all to the picture or any of the numbers it shows.

For all anyone (other than the person that took that picture) can tell, someone could simply have wired up the display LEDs to power in a way that lights up just those segments, and it isn't showing any data at all. ;)

The first three:
49.52V
0.0A
100.0Ah

The last two:
119.7
1

FWIW, if they had just run a discharge test on that battery, and gotten 100Ah out of it (impossible, but...) then the voltage would not be 49.52v, it would be below 42v (probably closer to 40v). Similarly, if they had just charged it to put 100Ah into it, the voltage would be about 54v or more. So the 100Ah means absolutely nothing, in relation to the voltage displayed.

BTW, the label on that battery, showing 48v 101000mAh, cannot be true unless that is made of cells nobody on the planet has ever seen. The blurry numbers showing which cell they are appears to say they are 18650 cells, which at most are 3-4Ah; in this case they seem to be the Samsung NCR 25R, which is this cell
https://www.imrbatteries.com/samsung-35e-18650-3500mah-8a-battery/
which has *at best* 3.5Ah, and there appear to only be 3 cells in parallel in that pack, so there can be *at best* 10.5Ah in it.

View attachment samsung_35E[1].pdf
SPECIFICATIONS:

Manufacturer: Samsung SDI
Model: INR18650-35E (35E)
Size: 18650
Style: Flat Top
Protected: NO, UNPROTECTED. This cell is unprotected and intended for use in protected battery packs only and NOT individually or as a standalone product. In order to operate safely it must have additional protection in the form of a PCB (protection circuit board) or BMS (battery management system), which is not included.
Nominal Capacity: 3500mAh
Discharge Current: 8A Maximum Continuous (1C)
Nominal Voltage: 3.6V
Maximum Voltage: 4.2V
Cutoff Voltage: 2.65V
Approximate Dimensions: 18.8mm x 65.25mm
Approximate Weight: 50g
Origin: Republic of Korea, Malaysia, or China
Specification Datasheet: Samsung 35E Datasheet

So either the seller is mistaken, having made a serious math error, or more likely, given the numbers shown on the "tester" plus the labelling, is flat out lying about it, scamming people by claiming ten times more capacity than is remotely possible. They certainly wouldn't be the first seller to do that (sellers of individual cells do this all the time).

Since they are probably lying about that, they are also probably lying about what cells are in there, and it probably does not have those specific cells in it. It is even possible that like other scammers they use random recycled garbage cells to build the packs from; possibly re-wrapped to look like the cells they claim (but since the packs themselves are sealed with wrap, and you'd probably void the warranty (which they probably don't have and likely wouldn't honor anyway) by opening it, they figure you'll never find out how badly they lied.


If you have the option, I recommend returning that pack for a refund, and buying something from a reputable seller. If you really need a hundred Amp-hours (five thousand Watt-hours), you'll either have to build it yourself, or have someone build it for you; I doubt there are any (good) ebike packs already built that large. Alternately you can simply buy ten 500Wh packs similar to what you have (but from a seller that doesnt' lie), and parallel all of them together to get 5000Wh.
 
thank You, that explain in detail where is an issue. In that case, to run longer distance with this engine, I have following choice:
1) expand batterie and uses, as You mention, 6x13 series 3500mA cells to have like 20Ah or like 12x13 series to have 40Ah(which would be huge and add more weight to the existing already 12Kg engine + battery)
2) wait for higher capacity cells
3) sell out 1500W engine and bay new 250W engine - in that case I would get same speed as now when uses health power option - 750W, 25Km/h, which should be good enough to run in the city or even small hills

Saying that(point 3) - when I would use 250W motor, 36V, I could use battery with 4x9 cells 3500mA which give me 14Ah, and consider I would use 250W engine which would be 3 times lower than my current 750W(when used 50% limitation of 1500W), battery should last for 3x times more (+ 2x times more due to higher capacity), so on eko drive, I should be fine to drive 50Km?
 
Cas_blue_pianist said:
thank You, that explain in detail where is an issue. In that case, to run longer distance with this engine, I have following choice:
1) expand batterie and uses, as You mention, 6x13 series 3500mA cells to have like 20Ah or like 12x13 series to have 40Ah(which would be huge and add more weight to the existing already 12Kg engine + battery)
2) wait for higher capacity cells
3) sell out 1500W engine and bay new 250W engine - in that case I would get same speed as now when uses health power option - 750W, 25Km/h, which should be good enough to run in the city or even small hills

Keep in mind that lower wattage will mean lower speeds...so if you just go slower, you'll get that with your existing system, but still have the extra power available if you run into a situation that requires it.

Rather than changing out the system to get lower power, you can just use less throttle. (that's usually what the "eco" modes do--they limit the response of the controller to your throttle input).

If you don't have an actual throttle, and it's all controlled by PAS, then you could modify the controller's shunt (or get a lower-current controller/display/pas) to have a lower maximum power, if the one you have has no settings for this other than the "eco" switch.



Saying that(point 3) - when I would use 250W motor, 36V, I could use battery with 4x9 cells 3500mA which give me 14Ah, and consider I would use 250W engine which would be 3 times lower than my current 750W(when used 50% limitation of 1500W), battery should last for 3x times more (+ 2x times more due to higher capacity), so on eko drive, I should be fine to drive 50Km?


If "4x9" means 4s 9p, (or even 4p 9s) then you have only 4 x 9 = 36 cells in it. So you then have less wh; meaning less range. How much range you get with that depends on your actual power usage to do what you want to do.

(Note also that 36v is 10s. )

I recommend you go to the http://ebikes.ca/tools/simulator.html and play around with various configurations and riding conditions, so you can see what it will take to achieve whatever speed and range you need under your riding conditions (whatever hills, wind, road type, etc).
 
Cas_blue_pianist said:
3) sell out 1500W engine and buy new 250W engine - in that case I would get same speed as now when uses health power option - 750W, 25Km/h, which should be good enough to run in the city or even small hills

Another thing to note, is a smaller motor running within its optimal power band and RPM is more efficient than a large motor running way below its rated power and RPM at low speeds.


Case in point, I have a 3KW Cyclone mid drive, mainly for dealing with Hilly wales. Quite efficient in America for commuting in traffic at 30MPH+

But not so efficient for cruising around the UK at the slow legal speed of 15.5MPH on the flat using only around 250w out of its 3000w capacity


So I'm considering putting the most efficient small 250w direct drive I can find on the front wheel

Plus it gives the small extra bonus of Regen braking and redundant powertrain in case of the failure of one or the other.





As for batteries, I've found building your own using genuine cells from a reputable supplier such as www.nkon.nl
Is a good option.

It's easier than you think, for an absolute newbie there's an intermediate option between buying a prebuilt pack and designing and fabricating one from the ground up.

And that is simply self assembly of a Shark style battery.

One of these with the cell layout and nickel plates already done for you ready to spotweld up: https://m.aliexpress.com/item/4001076311328.html?spm=a2g0n.order_detail.0.0.49d8f19cQVQvOL

(Only rated at 20A so I bought more nickel plates separately and double layered them https://m.aliexpress.com/item/1005003777519383.html?spm=a2g0n.order_detail.0.0.5e6bf19cJwqvTt

You might be better off buying the box with the "no nickel" option and just buying the plates separately, as the plates linked here are better because they have extra tabs that stick out for you to solder your leads onto, so there's no chance of overheating your cells by soldering directly onto them )


You will want these PET plastic insulation washers for the positive ends of the cells rather than the cheap paper ones that absorb moisture and increase the risk of corrosion
https://www.ebay.co.uk/itm/363384074940


And one of these well known and highly regarded BMS units (Battery Management System)
https://m.aliexpress.com/item/32876805034.html?spm=a2g0n.order_detail.0.0.1744f19cir8viX

(I used the 60A version for my 40A rated Cyclone, but be aware that the 60A version is too large for the case so needs to be put into a 80mm heatshrink tube with a silica gel sachet to absorb moisture, then sealed at either end with liquid tape/plastidip. Then secured on the outside of the case with black duct tape and the wires run in through a hole cut into the lower end of the battery, also sealed with liquid tape.

An added bonus of these BMS units is that you can monitor the health of your battery cells amongst other things as it connects to an app on your phone through bluetooth)


I highly recommend picking up one of these grounding matts with antistatic wristband to handle the BMS, https://www.ebay.co.uk/itm/294453161431 as I heard from a few places now that they are much more susceptible to damage from Electro static discharge than the PC hardware you may be used to, as PC hardware is designed for installation by home users, wheres BMS are assuming professional installation at a ESD safe area at a factory.

Though don't quote me on that as I have not yet fully researched this...




Then one of these spot welders, one of the best for the price and has worked a treat for me: https://m.youtube.com/watch?v=WxGErteGyZQ&t=1s

(Use eye protection work goggles as there will be sparks and you may be close in with your face to examine the placement as you spotweld)

Paired up with one of these Zeee Lipos https://www.ebay.co.uk/itm/143968625270

The individual spot welding probes that come with it are adequate but I picked up one of these spotwelding pens with springloaded tips that adjust for good contact when you press em down for a spotweld, and it made a world of difference for me....

https://www.ebay.co.uk/itm/403527924629

Perfect spacing every time (after adjusting the angle of the probe ends), no worrying about a tip slipping and coming into contact with the other probe (which makes quite a bang! Also damages the tip and risks blowing a hole through the cell casing... Don't ask me how I Know....)

Plus frees up a hand to hold the nickel plate secure, so no chance of a short circuit between cell groups from it jumping out of place at one end when pressing down on the other end for the first spot weld on that plate...

Springs are a little stiff stock, but the screws that hold the probes from going too far forward can be backed off till the head of the screw is above the plastic, so its the thinner threaded portion that is holding the probes from falling out of the plastic. This loosens the spring tension a little and gets it about right. I replaced the stock screws with longer ones so they can be backed out like that without being near to falling out themselves.

All things considered they made the job of spotwelding so much better that it's now easier for me to do two layers of plate on a whole battery than it was to do one side with a single layer with the old separate probes.



One thing to note, is it's best not to place a spot welding probe on the direct center of the negative end of the cell as this is where the "jelly roll" inside is connected to the outermost casing via a rail that runs the entire length of the 18650 cell.

You don't want to risk damaging that connection by blasting a spot weld right on it.

The positive end is usually fine as there's usually a raised plate separated from the cell itself there.






Other bits and bobs that I also needed....

Connectors
https://www.ebay.co.uk/itm/125154344755?var=426206089245

Wire for discharge leads
https://www.ebay.co.uk/itm/361296232202?var=630634243728

Heatshrink for insulation after soldering connections.
No link for this one as I haven't bought any recently, I'm still working with the bulk supply I bought from hobbyking for RC stuff years ago...


kapton tape is optional, but is a good thing to have around, especially if you have to run the thin BMS balance wires over the nickel in a battery pack, as with time and vibration the insulation of the wires can chafe through and short on the nickel strips.
So best to put some kapton tape between them for more chafe resistant insulation
https://www.ebay.co.uk/itm/373299713754?var=642255724573



I recommend putting an inline midi fuse somewhere on the input leads of your controller, protects the battery in the case of FET in the controller failing closed or dead short.

Something like this: https://www.ebay.co.uk/itm/313160298270

You will probably need a lower amp fuse to match your lower Amp hour battery.

Maybe 30A if you have a 20A limited controller.

Good baseline for your fuse is for your max normal load to be around 75% of the Midi fuse rating as shown here:
https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.littelfuse.com/~/media/automotive/datasheets/fuses/automotive-fuses/littelfuse_automotive_bolt_down_fuse_midi_32v.pdf&ved=2ahUKEwjPrsGlren2AhWMSPEDHYzGAAAQFnoECAMQAQ&usg=AOvVaw1xYzGHesn5EzRA4lDBjvOx

Also make sure voltage rating is sufficient for the voltage of your battery at its max state of charge



Easy enough to solder in line with your wire, then reinforce with a few layers of heatshrink.





Also if you are Autistic like me, and extremely fussy about getting the details right, you can use one of what I use to check and ensure all the cells in a parallel group are similar in internal resistance.
https://m.aliexpress.com/item/4000080760970.html?spm=a2g0n.order_detail.0.0.3feef19cHssIGj

The importance of which is explained here: https://www.sciencedirect.com/science/article/abs/pii/S0378775313019447

If you don't already have a soldering setup, what I use is a weller 80w
https://www.ebay.co.uk/itm/384885709079?hash=item599cf9d917:g:FuUAAOSw3X1ifUUy

And this solder is excellent
https://www.ebay.co.uk/itm/144124119919
It's an eutectic alloy, with a sharp transition beween liquid and solid.

Good for a beginner as it is more resistant to being disturbed from movement as it cools and solidifies causing a "dry joint", as well as having one of the best Rosin flux already included running through its core to help it "wet" onto the surfaces being soldered, helping result in a physically and electrically good shiny solder joint.

You can also save some money in the long run by doing what I did and buying a 1lb roll of it for around £40
https://www.amazon.com/Kester-24-6337-0010-Rosin-Solder-SPOOL/dp/B00068IJWC/ref=sr_1_51?crid=9J3R5ZU2XAGH&keywords=63%2F37+%22kester%22+solder&qid=1652632400&sprefix=63%2F37+kester+solder%2Caps%2C209&sr=8-51

Should last you a lifetime.



Or if you are in the North wales area...
I could help put it all together for you
😉👍
 
thx Gorillazilla, that is definitively something I need to consider, at least I would have trusted source, the only constrain I see at the moment is time.. as now, I am moving all my spare time to music :)

Another thing to note, is a smaller motor running within its optimal power band and RPM is more efficient than a large motor running way below its rated power and RPM at low speeds.

Yes, I think I might test lower power motor as it might be enough and give me longer distance, lower weight.

this is my current setup BTW:

https://ibb.co/BN6qjYq

As U can see, 48V 1500W motor is big with weight 11,5Kg, compare to 36V 250W motor 2.78Kg

RPM: 48V 1500W:540RMP
NM: 48V 1500W: 35-45NM

RPM: 36V 250W:320RMP <--------- this is consider to be the same or even more compare to when run 1500W motor with 50% limitation(750W)
NM: 36V 250W: 35-45NM

Additional issue I found that I can not lift it up when drive in front of obstacle. The reason I bought this motor for front was that I wanted to disassemble this in quick way and mount old wheel back, to convert this quick to an old non electric bike - however there is too much wires to unplug, and might be better option to fit motor at rear wheel with lower weight and leave it forever.
 
Cas_blue_pianist said:
thx Gorillazilla, that is definitively something I need to consider, at least I would have trusted source, the only constrain I see at the moment is time.. as now, I am moving all my spare time to music :)

Another thing to note, is a smaller motor running within its optimal power band and RPM is more efficient than a large motor running way below its rated power and RPM at low speeds.



As U can see, 48V 1500W motor is big with weight 11,5Kg, compare to 36V 250W motor 2.78Kg

Yeah that motor is a little overkill, though saying that, the leaf motor 1500w turned out to be quite efficient even at low speed

Generally a very efficient motor overall

You could get a £10 watt meter and put it between your battery and controller and get some real data on the power draw at different speeds so we can figure out if it's really worth the effort of fitting a different smaller motor

https://www.ebay.co.uk/itm/234513830713
 
Hi
An alternative watt meter
https://www.aliexpress.com/item/1005003713078282.html?spm=a2g0o.order_list.0.0.b49118028fRtdS
Not as high a wattage but you would never get close anyway.
Geoff
 
Cas_blue_pianist said:
The issue I have that when switch to health power(750W), battery last only for 10Km, if used on full power(1500W), I can drive only max 5Km.

Your battery is barely sufficient to run a 750W motor, so at 1500W you are discharging way beyond the capability of the pack. Batteries have a much lower capacity/range if you discharge beyond their specs, and you will likely damage the cells, even though you have good quality cells. You need to treat your pack better, regardless of what you decide.
 
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