Getting doubble the discharge rate from a battery combiner off AliExpress with 2 ebike batterys with individual bms

[Salih44]

So i have 2x 48v 15ah ebike batterys with 25a bms on each i wonder if i can use an 40a controller with a battery combiner off aliexpress which can support up to 40a

Here is a link for the product :

https://aliexpi.com/0VA

 

[neptronix]

If it hits each battery with 40A for some milliseconds in kind of a checkboard pattern of drawing from each battery..
it may work, depending on the surge/pulse rating of your BMS ( can it handle a 40A pulse? )
But that pulse rating may be more like 30-35A

if it draws equal power from both batteries continuously then you are in luck, it'll definitely work

 

[Salih44]

If it hits each battery with 40A for some milliseconds in kind of a checkboard pattern of drawing from each battery..
it may work, depending on the surge/pulse rating of your BMS ( can it handle a 40A pulse? )
But that pulse rating may be more like 30-35A

if it draws equal power from both batteries continuously then you are in luck, it'll definitely work

Thanks and how many amp controller should i get for a 1000w hub motor build with theese chineese batterys?

 

[E-HP]

So i have 2x 48v 15ah ebike batterys with 25a bms on each i wonder if i can use an 40a controller with a battery combiner off aliexpress which can support up to 40a

Here is a link for the product :

https://aliexpi.com/0VA

Reading the description, it looks like these would be the equivalent, but with no box:

https://www.aliexpress.us/item/3256806667274442.html

Mod Edit: Edited link to remove tracking information.

 

[Salih44]

Reading the description, it looks like these would be the equivalent, but with no box:

https://www.aliexpress.us/item/3256806667274442.html

Hi, so i heard that those are really dangerous and you never should use them thats why i bought the battery discharger but if you please can explain more about them it will help me a lot.

Mod Edit: Edited link to remove tracking information.

 

[neptronix]

Thanks and how many amp controller should i get for a 1000w hub motor build with theese chineese batterys?

If that's a direct drive motor, it should be ok to take 40A peaks no problem. But it probably can't do this sustained, like when climbing a hill.
Your limit on that is heat. Without a temperature sensor, you test this by hand:
if the motor becomes too hot to leave your hand on for a few seconds, that's too hot. Adjust amps downward until it stops being that hot in your most intense situation ( for example climbing a big hill )


The batteries? you'll probably never see a spec sheet of whatever random Chinese cell you have in there.
Therefore you need to find out what they are capable of.
It's quite likely that they're barely capable of driving the existing motor at 25A. But you may have got lucky and they can do 30A.

You need a multimeter or power display of the realtime watts and volts to determine how many volts of drop you have from 0 throttle to 100% throttle while crusing.

Some people use a cycle analyst standalone, others get a cheap $25 power meter from hobbyking.

On a 15ah 48v battery, i recommend not exceeding 3v of drop and consider 4v a hard limit ( because you're creating a substantial amount of heat )

So basically adjust amp upwards until you see a max of 3v drop while cruising.

 

[E-HP]

Thanks and how many amp controller should i get for a 1000w hub motor build with theese chineese batterys?

Well given that there is no information available about these chineese battery’s, except that they are two 48v 15Ah batteries, then hers a ballpark guess.
Based on observation and owning a pack with generic cells, most of them use cheap cells (they call A grade) with 2100mAh to 2600mAh capacity. The cells can output about 5A per cell peak with a lot of sag, but 4A is probably better for useable continuous current. This is when the pack is new. It’s all downhill as far as both capacity and output current is concerned as the pack is used and ages, so you have to account for that as well.
The combined packs, IF paralleled to allow combined current output might be good to 45A or so, or less depending on age, but only half that if it’s an ideal diode circuit that doesn’t allow parallel discharge.

PS. If it’s one of those blue batteries then there’s too much fake info to be able to estimate the capability.

 

[Salih44]

Well given that there is no information available about these chineese battery’s, except that they are two 48v 15Ah batteries, then hers a ballpark guess.
Based on observation and owning a pack with generic cells, most of them use cheap cells (they call A grade) with 2100mAh to 2600mAh capacity. The cells can output about 5A per cell peak with a lot of sag, but 4A is probably better for useable continuous current. This is when the pack is new. It’s all downhill as far as both capacity and output current is concerned as the pack is used and ages, so you have to account for that as well.
The combined packs, IF paralleled to allow combined current output might be good to 45A or so, or less depending on age, but only half that if it’s an ideal diode circuit that doesn’t allow parallel discharge.

PS. If it’s one of those blue batteries then there’s too much fake info to be able to estimate the capability.

so yeah i checked the battery pack which was not 15ah but actually 13ah (labeld as 15ah) and the cells in them are peak 7.5a which are like +- 1 year old and i have found a 30a bms battery which is really 13s 6p and 15.6ah so im going to go with 30a controller i guess

 

[Salih44]

If that's a direct drive motor, it should be ok to take 40A peaks no problem. But it probably can't do this sustained, like when climbing a hill.
Your limit on that is heat. Without a temperature sensor, you test this by hand:
if the motor becomes too hot to leave your hand on for a few seconds, that's too hot. Adjust amps downward until it stops being that hot in your most intense situation ( for example climbing a big hill )


The batteries? you'll probably never see a spec sheet of whatever random Chinese cell you have in there.
Therefore you need to find out what they are capable of.
It's quite likely that they're barely capable of driving the existing motor at 25A. But you may have got lucky and they can do 30A.

You need a multimeter or power display of the realtime watts and volts to determine how many volts of drop you have from 0 throttle to 100% throttle while crusing.

Some people use a cycle analyst standalone, others get a cheap $25 power meter from hobbyking.

On a 15ah 48v battery, i recommend not exceeding 3v of drop and consider 4v a hard limit ( because you're creating a substantial amount of heat )

So basically adjust amp upwards until you see a max of 3v drop while cruising.

Hi, so i found an 30a bms battery and i think i will go with an 30a controller motor is hub motor btw and I will switch one of the 25a batterys with 30a battery and i think that that combo deffinetly can handle 30a with a balanced discharger thanks