Maximum voltage for BBS02 750W ?

[alexis57]

Hi,

I'd like to know what is the maximum voltage for the BBS02 750W 25A 48v.

For now, I have a 13s 54.6V battery pack but I'd like to increase the voltage of the battery pack by adding another parallel group in serie. Then 14s 58.8V max.

Indirectly, I'll increase a little the range because it'll decrease the current and I now I will need to change the voltage of cutoff for the bafang controller.

For now, the motor is really powerful at the beginning but after the voltage is dropping too fast, with another parallel group, I could stay much longer in a higher power.

Is it good ?
Could you tell me what's wrong ?

Did someone use the bbs02 with a 13s and then a 14s ? Could you tell me the difference you felt ?

Thank you !

 

[cwah]

i did that, works ok but at full voltage it stresses the motor

 

[NeilP]

Hi,

I'd like to know what is the maximum voltage for the BBS02 750W 25A 48v.

As cwah says, higher voltages do stress the motor more, but there is no maximum voltage that will harm the motor. OK, well there is, but we are talking many thousands of volts before electrical failure occurs due to high voltage break down of the electrical insualtion .

The control system is another thing. I have no idea about the controller, and the dashboard display unit..those will be the limiting factors on voltage.

But Higher voltages run at the same current you are currently running at will give more power...and therefore more mechanical stress not he drive train, and also more heat, so 'roasting' the motor and its insulation is then a risk

Power (and therefore heat) = Voltage x Current P=IV

For now, I have a 13s 54.6V battery pack but I'd like to increase the voltage of the battery pack by adding another parallel group in serie. Then 14s 58.8V max.

So not talking of a massive voltage increase, so no major risk, but yes the higher voltage will give more stress

Indirectly, I'll increase a little the range because it'll decrease the current and I now I will need to change the voltage of cutoff for the bafang controller.

For now, the motor is really powerful at the beginning but after the voltage is dropping too fast, with another parallel group, I could stay much longer in a higher power.

So your problem is Voltage Sag after you have been riding for a while ???

increasing the voltage at the start of the ride is NOT the answer

Keep the voltage the same and add another 13 series pack in parallel to your original pack.

So if you have a 5 Ah pack now, maybe make it 10 or 15 Ah.

that will then keep the voltage higher .

Or is it an old battery pack...maybe you need better quality cells ( or greater capacity)...
have you done a discharge test, monitoring the voltage fall the cells?
maybe you have a single duff cell within the packs



I'd try increasing the pack capacity and KEEP 13s as it sounds like your problem is capacity and voltage sag...not initial voltage


What is your pack exactly ...cell type/ chemistry, ah capacity?

 

[alexis57]

But Higher voltages run at the same current you are currently running at will give more power...and therefore more mechanical stress not he drive train, and also more heat, so 'roasting' the motor and its insulation is then a risk

Power (and therefore heat) = Voltage x Current P=IV

As I said, if I increase the input voltage, I will decrease the input current. (I consider same losses with 13s and 14s)

So your problem is Voltage Sag after you have been riding for a while ???

increasing the voltage at the start of the ride is NOT the answer

Keep the voltage the same and add another 13 series pack in parallel to your original pack.

So if you have a 5 Ah pack now, maybe make it 10 or 15 Ah.

that will then keep the voltage higher .

Or is it an old battery pack...maybe you need better quality cells ( or greater capacity)...
have you done a discharge test, monitoring the voltage fall the cells?
maybe you have a single duff cell within the packs

I have a new battery pack 13s4p means 11.6 Ah Panasonic NCR18650PF rank B. No problem with it.
Explain why increase the voltage is not a solution ?

LVC:
13s : 3V*13 = 39V
14s : 3V*14 = 42V
And I decrease the maximum input current of about 2A.

I'm surprised, no one told me about the most important thing in an electronic circuit which is the capacitor's voltage...
I reply to myself, I found the capacitor's voltage is 62V then we cannot increase more than this voltage.
I'd say, no problem for the display or anything else since dcdc converter(s) exists.

My problem is not a capacity problem since if I stop for a small rest, it's ok.
Id say it's more the voltage sag after 1h. With an input voltage higher, this will be solved.

 

[cwah]

increase voltage is POTENTIALLY a solution, if you accept the risk that you may damage the clutch or gear due to additional torque generated at full voltage.

I've seen my motor struggling slightly at full voltage on 14s, which didn't happen on 13s... and it still work fine.

Unfortunately, there is a risk of rapid wear due to the motor being use over its specification, and the risk is that it may results in some damaged parts in your motor in few months time.


ps: I damaged 3 geared motors already due to abusing them over their specification. They all died respectively within 1 year, 3 months and 3 months.

 

[NeilP]

As I said, if I increase the input voltage, I will decrease the input current. (I consider same losses with 13s and 14s)

Yes I did see that but just wanted to make sure. Some people do not understand that basic relationship

So your problem is Voltage Sag after you have been riding for a while ???
increasing the voltage at the start of the ride is NOT the answer

I have a new battery pack 13s4p means 11.6 Ah Panasonic NCR18650PF rank B. No problem with it.
Explain why increase the voltage is not a solution ?

Well if you increase the voltage it is sort of a solution, but you still have the voltage sag , and you then risk damage to the gear train.


With even a new small Ah battery pack like you have made with B grade low C rating and quite 'saggy cells'
https://endless-sphere.com/forums/viewtopic.php?f=31&t=61608&start=25#p959214

You are always going to get this at the end of charge.

Giving greater capacity will lessen the effect. as will a pack made from better cells

I'm surprised, no one told me about the most important thing in an electronic circuit which is the capacitor's voltage...
I reply to myself, I found the capacitor's voltage is 62V then we cannot increase more than this voltage.
I'd say, no problem for the display or anything else since dcdc converter(s) exists.

No one told me lots of things..I read it all or found by reading the forum my self. If everyone told you everything there is to know about e-bike batteries in one hit, you would not take it all in any way. I mentioned it and you found out more, that is good.

My problem is not a capacity problem since if I stop for a small rest, it's ok.

To me stopping for a small rest and giving the cells a chance to recover and cool down is a perfect indication of a capacity , "C" rating and cell quality issue.

What is the max amp draw from the battery pack?

If the spec I read here: correctly, then your pack max rating continuous is 40 amps. So from my own personal experience with packs over the past 4 -5 years, for good cell life and reduced heating i'd not be wanting to draw more than 10 continuous with occasional peaks to 20 or 30 max. And even then you are runnign at quarter of max rated. Too high in my experience for a reliable pack

For instance my pack on my bike is 20s4p nano Tech lipo. So that is nominal 72 volt 20Ah pack. I charge to 83v. According to the Hobby King Spec they specify 25 C continuous, 50 C burst, which gives 500 continuous 1000 amp burst.
I run at peaks of about 140 amps. If I wanted to go higher I'd think seriously about adding more parallel to keep the cells very much under rated.

At a guess ..what are you running current wise? 10-15 amps? hopefully not a lot more. That is 50% C rating capacity ..the cells are going to get warm..and performance will decrease as IR rises.

Id say it's more the voltage sag after 1h. With an input voltage higher, this will be solved.

but you will still be getting the voltage sag, just starting at a higher voltage. Still putting the cells under the same load.

I have a pack here, also 48/50 volt...12 series Lipo Zippy 5000 5ah packs 'Only 20C rated" I'd not use them on a high power bike
it is 12s2p, 10 Ah capacity ..so 200 amp 'advertised continuous' . Max I have controller set to is 25 amps, so that is one eigth of advertised rating.
I'd not want to draw much more out of it and keep it reliable.

Small low grade cells , small pack , you will get voltage sag. and the only real way out , if it were me is greater capacity or better cells.

 

[alexis57]

I won't change my battery pack, Panasonic grade B are well enough for ebike. (I can ride more than 20km without pedaling at 40km/h all long)

The max current for my battery pack, I think 40A.
I don't get more than 20A (even if the controller is set at 25A), saw with an amp clamp and oscilloscope.
In continuous, I'm at a little more than 10A in average.

With 36°C outside, wet the battery doesn't go higher than 42°C, even if I go fast during long time without pedaling.

Of course I'll get the voltage sag but increasing the voltage makes decrease the current and then increase the capacity. (ok not as much but still)

I know it's not the best solution but this solution still decreases the voltage sag. (R*I)
I will also change the mosfet with better mosfets to decrease the heat and the loss.

Anyway, I'm gonna use another parallel pack (its only 4 18650) to try and I'll see the result with oscilloscope and feeling.

Thanks !

 

[NeilP]

42 for battery pack ! Yikes,

Got CA temp sensor on mine, never seen more than 30 deg C

if you have the cells, then no harm in trying.

If you did the power limiting via a CAV3, then you could set a wattage limit and not a current limit, so as the pack voltage drops, current will increase.

 

[NeilP]

With regard to current figures, and your packs rating

At 20 amps, that is 50 % of amp draw capacity.

I'd personslly not run a pack of that size and C rate at 10-12 amps peaks and 7-8 continuous, and then not have the voltage sag.

Another thought, do you have a CELLLOG data monitor?
Might be worth doing a run with a pair rigged up, maybe one parallel cell group is a bit poor?
Just because they are new is mo guarantee.
I just had HobbyKing replace 2 duff packs that arrived last week. Each pack had duff cells

 

[alexis57]

42 for battery pack ! Yikes,

Got CA temp sensor on mine, never seen more than 30 deg C

if you have the cells, then no harm in trying.

If you did the power limiting via a CAV3, then you could set a wattage limit and not a current limit, so as the pack voltage drops, current will increase.

Are you serious ? What you said is totally silly...
You should explain me how a battery pack could be lower than 30°C if the outside temp is over 36°C. So far, A battery pack is not an air conditioner...

Where is your temp sensor ? on the surface ?! I have two temp sensors INSIDE the pack. You should think more and explain what you're measuring because for now it's not comparable. If I measure the temperature of the surface, I'll got the same or almost than the ambient temperature.

If you look at the topics of ES, many guys used the exactly same battery pack. I don't know why I won't use 20A, it's exactly in the rating of the PF Panasonic cells, even lower. 5A for a PF cell is great.

As I said, the voltage sag comes only at the end, after 20kms.

 

[NeilP]

Outside air temp 36 .. Shit that is hot. If we see 28-29 it is the best we get here in summer.

Sorry, my mistake, forgetting hot/tropical countries , which is bad of me since I have lived in Africa (Uganda,DRC etc)
My temp sensor in centre if the pack. Made of 8 x blocks of 10 series Nano Tech Lipo

 

[NeilP]

With regard to amps bring drawn,
To me using those 18650 cells is rather like getting a 50cc motorcycle and tuning the frock out of it, rumming it at 10,000 rpm, rather than just gettimg a bigger more powerful motorbike.

Running little cells at near max spec is likely to give issues.

If lots of others are using the same packs as this, and not complaining of voltage sag issues, it does then point back to one of my very first comments about an iffy cell.
Even building your own new pack, with new capacity and IR matched cells , (that you have checked yourself, ) does not guarantee that after a few cycles, a cell won't go bad, bringing the rest of its parallel group cells down with it,
A rest then gives it a chance to recover.

Unless you have done a cell voltage data logging run with Celllogs or similar, you have no way of knowing for sure that it is not a single cell group dropping 'off the cliff' early

 

[KINNINVIEKID]

I ran my BBS02 at 14S and it was constantly skipping in the top 2 gears(out of 8 ).
As soon as I went back to 12S it ran perfectly in all gears again.
I run pairs of 16Ah Multistars and can pull 15.8Ah out of them and they still pull as well as when they are freshly charged.

 

[NeilP]

I run pairs of 16Ah Multistars and can pull 15.8Ah out of them and they still pull as well as when they are freshly charged.

The power of even low C rate Lipp compared to a small parallel pack of individually gutless little 18650's. !

 

[cwah]

I ran my BBS02 at 14S and it was constantly skipping in the top 2 gears(out of 8 ).
As soon as I went back to 12S it ran perfectly in all gears again.
I run pairs of 16Ah Multistars and can pull 15.8Ah out of them and they still pull as well as when they are freshly charged.

What do you mean by skipping the top 2 gears? You mean it was stuck?

So you can also confirm that the BBS02 can't handle 14s?

 

[PerryAJ]

14s is perfectly fine for the BBS02. Em3ev sells their battery packs by default in 14s configuration. As usual, run in the right gear and don't push the setup too hard.

Lipo is fine, preferred in some high current applications, but the reality is that decent 18650 packs are more than enough for this kit for many people. They will last more charge cycles than a lipo setup while also being (generally) less susceptible to ballooning and imbalance. Both are great choices, but give or take depending on the application.

 

[KINNINVIEKID]

I ran my BBS02 at 14S and it was constantly skipping in the top 2 gears(out of 8 ).
As soon as I went back to 12S it ran perfectly in all gears again.
I run pairs of 16Ah Multistars and can pull 15.8Ah out of them and they still pull as well as when they are freshly charged.

What do you mean by skipping the top 2 gears? You mean it was stuck?

So you can also confirm that the BBS02 can't handle 14s?

Skipping means the chain is jumping out of the teeth,this causes the cassette to wear out in no time at all and,if using a cheap chain) is a major cause of chain snapping.
14S is the maximum LiPo config you can use with the 48V BBS02.

 

[cwah]

On 14s, when I start from stop at full power, the gear make strange noise and feel like it's slipping a bit.

I had the same issue with my 2 other bpm who gave up after 3 months. That's why I am a bit worried

 

[wompus]

While not really recommended, I run my BBS02 at 15S. I'm using drill batteries and they are 5s, so until I rip them apart and build my own pack 15S it is. It may not be ideal or idiotproof but it works fine for me. I have >500 miles on this configuration so far. Fully charged off the Dewalt charger my pack is ~61.9V. I was hoping that this would make the controller happy since I had read about he 62V cutoff, but it gives me an error code until the voltage is 61.5-6V (all according to my cheap inline power meter). I either bulk charge to 61.5V now or use resistors to drop the voltage down when coming off the dewalt charger.

You can definitely damage the system at 15S and 25A. I learned the somewhat hard way by stripping the plastic gear inside...oops. I think i pulled somewhere around 1450 watts at the time. Again according to my cheap and who knows how inaccurate power meter. After that issue, I have kept it at PAS7 or below and have not had any more issues in >450 miles. I try to keep my Watts below 1KW but that isn't always the easiest to control.

No comments on battery quality from me though. I have been pretty happy with 3s2p 4AH drill battery setup. I can get about 7AH out of it before the bike is noticeably slower.

Edit: if the batteries are fresh and you push the throttle from a stop it jitters a bit and doesn't seem happy. Solution for me was....don't do that.

 

[popeonearope]

I live in europe where 250w is the maximum so I'll be ignoring that and getting a bafang 750w mid drive.

I'll be fitting a a nicola 4 cargo bike to carry 3 kids to school, including a fairly steep hill but I don't need huge range. I'll have a roller brake nexus 8 hub on the rear wheel.

Can anyone please help me pick a battery (budget is not a constraint). I'll need 48v I guess but should I just go for the highest samsung amps I can afford (say 22)? or will that put more strain than is necessary on the motor / be much heavier? from em3ev.com

thanks very much.

 

[spinningmagnets]

High-current cells are very expensive right now, and it is the controller that limits the max amps that are sent to the motor. If you are truly limiting the programmable controller to a 25A maximum, then you only need a battery pack that is rated to provide 25A. As an example, the small 5P triangle pack with 25R cells can put out 100A. The "25" means that the 25R cell has 2500-mAh per cel of capacity.

Since budget is not a constraint, you have the freedom to spec a long-range cell (high mAh per cell). I own a triangle pack from em3ev that I have been very happy with. It uses the Samsung 29E cell. The "29" means that each cell has 2900-mAh per cell of capacity. Soon, some E-bike battery suppliers will start using one of the new 3200-mAh to 3500-mAh cells that are just now reaching the Vape market, but...I have not seen any being made with those yet.

 

[alexis57]

I see.

Since I failed to sell my 52cells rank B I bought, is it possible to add another serie group or two to a pretty new "used" pack (maybe 5 cycles) with a different rank ?
13s4p => 13s5p or 13s6p
I still have space in my bag for adding 2 maximum.

And yes, since its really hot these days I maybe use my bike more like a 50cc than a bike...
After 2hours and 20kms, the motor is pretty hot, the humidity and 36degC dont help lol

I will decrease the max current for the summer. It still should be really great to ride.

Thank you !

 

[amigafan2003]

62v or higher triggers the high voltage error on the display and the system won't run.

I ran my 48v500w bbs02 on 15s lipo with cells charged to 4.1v no problems.

 

[Samd]

62 volts