Hi there I was just looking for information
would it be possible to use 2 DC to DC buck converter both with an output of 30a to convert 2 36v 500wh batteries to 24v and connect them in series to make 48v or the voltage they rest at when fully charged to controller that takes 48v and I assume the 30a together will be 60a. and the controller will only draw what it needs.

 

Also if this is not the right approach what would be ?
kind regards FrankinBiker

 

The power supply you show is a boost. It increases the voltage. I think you want a buck not a boost.
I think you have two 36V batteries.
You want to buck down to 24V.
If you ran the supplies in series, you could get 24+24=49V at 30A
If you ran the supplies in parallel, you could get 24V at (30A+30A=60A)

 

thanks you for your response I believe 30 amps will be sufficient for the motor as I only intend on putting 20 nominal to 25a peek through it.

 

The power supply you show is a boost. It increases the voltage. I think you want a buck not a boost.
I think you have two 36V batteries.
You want to buck down to 24V.
If you ran the supplies in series, you could get 24+24=49V at 30A
If you ran the supplies in parallel, you could get 24V at (30A+30A=60A)

would it be possible to run it in the other direction to drop the voltage like a transformer ? or could I just use a transformer?

 

would it be possible to run it in the other direction to drop the voltage like a transformer ? or could I just use a transformer?

No and No.
Transformers only work with AC, not DC.
You need a buck converter to drop the voltage.

 

No and No.
Transformers only work with AC, not DC.
You need a buck converter to drop the voltage.

thank you so much for the information after a little resuch after the post I can to the same conclusion. I appreciate the support and knowledge.

 

I have come to a better solution I believe
to use prismatic pouch cells to build the battery from scratch at 3.6v and 60ah 60a draw continues over some really thick bus bars using glass fiber board for the end cap and rivnuts for the end tab holders sandwiches between 2 stanlus steal bus bars.
as it's not too expensive to do so that way I can build custom voltage packs to distribute the weight over the whole bike rather than 1 location.

also open to suggestions.

I'm relatively new to this and do understand the dangers but will take every precaution to mitigate the dangers the best I can.
kind regards FrankinBiker

hope this helps other people too

 

correction I mean pouch not prismatic

 

Among the issues you face is that high of current. Sixty or even 30 amps is pretty high current and be it a buck or boost converter it needs to be able to handle the higher current. Additionally the wire gauge used needs considered. Wire gauge "ampacity" figures into the scheme. What exactly is the plan involving a bike? What exactly is the objective? Sixty amp you are looking at AWG 4.0 and 30 Amp you are looking at AWG 8.0 as minimums.

Ron

 

Among the issues you face is that high of current. Sixty or even 30 amps is pretty high current and be it a buck or boost converter it needs to be able to handle the higher current. Additionally the wire gauge used needs considered. Wire gauge "ampacity" figures into the scheme. What exactly is the plan involving a bike? What exactly is the objective? Sixty amp you are looking at AWG 4.0 and 30 Amp you are looking at AWG 8.0 as minimums.

Ron

T
hank you Ron I appreciate the information.
would 4mm stainless steel bus bars be sufficient for the amps passing between the cells.
also is it possible to connect the 2 48v batteries in series and a 3ed in parallel to the 2 in series?
to increase the amps so I can use 2 30a controllers for dual motor and controller

I presume I would have to use the 8.0 AWG wire or higher as I found out the particular cells I found are only 50a.at 50ah.

would it also be safe to say I'll need to increase the AGW of the wire coming from the windings in the motor to 6 AWG or 8AWG if it will fit down the center and I shall be making censor less to fit the wires.

I really appreciate all the information and support you are all showing project.
thank you to all.

 

also I no longer will be using a boost or buck converter and the found were rated at 50a each

 

also I no longer will be using a boost or buck converter and the found were rated at 50a each

The plan is to produce a long range high torque e bike for climbing mountains and as I live in a really hilly and mountainess area.
my motor is gears also
I want to make it 72v in the future by combining my batteries

I am custom building them so I can remove cells to drop them back to 36v over two batteries to make the 72 or possibly leave them at 48 and combined them to make 96v
they will sit on the side in pannier packs in water tight boxes

I also plan to upgrade the motors in the future to handle all the power. I will also be installing hydraulic breaks when it arrives.

 

I also understand the current motor may only take 20 amps at 36/48v and will probably make the 2 side packs 36v and the center back 12v to bring the voltage up to 48v.

 

it's a bafang
BF RM-G060 750D
capable of 1kw nominally I believe
all tho it's marketed at a 750w

 

I remember when my local Harley chapter brought in the first Harley electric bike. While I have no plans for an electric bike I was impressed with the torque and acceleration.

Anyway as to batteries? Identical batteries can be placed in parallel which gives more current or they can be placed in series which gives us twice the voltage. Placing two batteries in parallel we can double the current but placing two batteries in parallel and adding one in series is not a good idea. What you want to do is look at the data sheet for your motor noting the voltage and peak current demand then make up your power supply built around your motor and expected run time. Regardless of battery chemistry we never want to run a battery down below a given voltage point. Additionally as I mentioned, when placing batteries in parallel or series they need to be identical batteries.

Ride Safe
Ron

 

perfect I really appreciate your knowledge
I currently have a scooter that runs a 52v 50a battery with 2 controllers and motors at 25a each
Thank you for answering my battery questions as I was not entirely sure

It probably will be the same answer but if I were to make the capacity of the 12v to be 100ah would that make it possible to connect it to the 2 36v packes in parallel which would also be 100ah combined.

 

It probably will be the same answer but if I were to make the capacity of the 12v to be 100ah would that make it possible to connect it to the 2 36v packes in parallel which would also be 100ah combined.

Yes, that is how it plays out. If I have two 36 volt 50 amp hour batteries in parallel I have a 36 volt 100 amp hour battery.

Ron

 

hey everyone
just another question about the DC to DC booster is it possible to add the in series or parallel to the same control as my battery has 2 output wires?
to increase voltage or amps

 

I wish to step up a battery from 52v to 25a but the booster says 30 but can output 22 constant.