60v to 48v buck converter for e-bike

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ngant17
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60v to 48v buck converter for e-bike

Post by ngant17 » Jan 07, 2018 6:57 pm

I’m planning to use power tool batteries for my supplying voltage to a new Bafang BBS02 48v kit.

Most of the ones I have are 18vdc and 20vdc. Here are the possible combinations I can use:


3@18v = 54vdc
3@20v = 60vdc

2@18v + 1@20v = 56vdc

2@20v + 1@18v = 58vdc

and finally, 1 battery @ 60v

So I think I’m looking for a buck converter (step-down converter) or a DC-to-DC power converter to step down voltage from 56-60vdc input (supply) to a 48vdc output(load).

I am seeing a DC to DC converter with Input voltage range of 50-72V DC. And Output voltage of 48VDC, Output current 10Amps, Output rated power 480Watts.

Would this be a good fit for the batteries that I want to use with the Bafang BBS02? I want to keep as close to 48vdc on the Bafang so I don't burn up any internal electronics.
Exitor Magna mountain bike, dual suspension, 24in tires
Bafang BBS02 motor 48V / 750W
46T Bafang chainwheel / 20T Shimano SF-1200 single freewheel
KMC Z140 1/2” x 1/8” single-speed chain
60v Greenworks battery / 3 @20v Black & Decker batteries
60V/30A Buck Converter Step Down DC Regulator, by SX Electronics / Aliexpress

mark5
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Re: 60v to 48v buck converter for e-bike

Post by mark5 » Jan 07, 2018 7:15 pm

Don't know about Bafang voltage requirements but the 18 & 20V packs are both 5 cells in series inside. A 12V pack has 3 cells inside. You could run on 13S, 52V, two 18V or 20V packs plus one 12V pack connected in series.

18v vs 20v Lithium Ion Power Tools - The Truth Uncovered by Tools In Action (length: 3m59s)
https://www.youtube.com/watch?v=dBehZbptnCw

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wturber
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Re: 60v to 48v buck converter for e-bike

Post by wturber » Jan 08, 2018 4:02 pm

I'd find out how many cells are in the 60v pack and see if my controller could handle that directly. Alternatively, I'd consider running two of the 18/20v packs in series (probably 2s and 2P or 2s and 3P)and then use a boost converter to bring the voltage up to around 54v (the voltage of a fully charged 48v pack). I only suggest the boost converter because I've been running one for a bit and it has been working fine. The main limit is that it will only supply around 1165 total watts in that voltage range.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
7 x 36v 4.3ah 10s 2P battery packs - Wangdd22 1500W 30A DC Boost Converter delivers 54v and about 1175 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
https://endless-sphere.com/forums/viewt ... =2&t=90369

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ngant17
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Re: 60v to 48v buck converter for e-bike

Post by ngant17 » Jan 08, 2018 8:42 pm

Sounds like an excellent idea. I may end up getting this one, the Wangdd22 1500W 30A DC Boost Converter Step-up Power Supply, as you suggest. Looks very sturdy, a $40 unit on Amazon.

The Bafang electric motor I have is rated at 750 watts, 48 volts. Motor current Limit:25 amps.

Power tool batteries used for this motor will not exceed 10 Amp Hour, they are lithium-ion. Rated watt/hours of batteries will not be more than 100 watt/hours.

OTOH would it be more efficient to use a step down converter?

IDEALPLUSING on Alibaba is listing a 60v to 48v dc dc converter:

Model IPS-DTD60S48
Input rated voltage 60V DC
Input voltage range 50-72V DC
Efficiency 93% (half load) ; 92% (full load)
Output voltage 48VDC
Output current 10Amps
Output rated power 480Watts
Output peak power 125%

Cost is approx. the same as step up unit above.
Exitor Magna mountain bike, dual suspension, 24in tires
Bafang BBS02 motor 48V / 750W
46T Bafang chainwheel / 20T Shimano SF-1200 single freewheel
KMC Z140 1/2” x 1/8” single-speed chain
60v Greenworks battery / 3 @20v Black & Decker batteries
60V/30A Buck Converter Step Down DC Regulator, by SX Electronics / Aliexpress

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ngant17
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Re: 60v to 48v buck converter for e-bike

Post by ngant17 » Jan 08, 2018 9:25 pm

BTW can the Wangdd22 1500W 30A DC Boost Converter be used to step down voltage? The spec sheet suggests to me that it would do that:

Input voltage: DC 10V~60V
Output voltage: 12~90V continuously adjustable

If so, that will be top on the list to finish the bike.

My electrical knowledge is generally confined to 24ac irrigation and some DC latching solenoids. Not much more than that.
Exitor Magna mountain bike, dual suspension, 24in tires
Bafang BBS02 motor 48V / 750W
46T Bafang chainwheel / 20T Shimano SF-1200 single freewheel
KMC Z140 1/2” x 1/8” single-speed chain
60v Greenworks battery / 3 @20v Black & Decker batteries
60V/30A Buck Converter Step Down DC Regulator, by SX Electronics / Aliexpress

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wturber
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Re: 60v to 48v buck converter for e-bike

Post by wturber » Jan 08, 2018 9:28 pm

ngant17 wrote:
Jan 08, 2018 9:25 pm
BTW can the Wangdd22 1500W 30A DC Boost Converter be used to step down voltage? The spec sheet suggests to me that it would do that:

Input voltage: DC 10V~60V
Output voltage: 12~90V continuously adjustable

If so, that will be top on the list to finish the bike.

My electrical knowledge is generally confined to 24ac irrigation and some DC latching solenoids. Not much more than that.
Nope. Output voltage must exceed input voltage. And I'm no electronics expert either.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
7 x 36v 4.3ah 10s 2P battery packs - Wangdd22 1500W 30A DC Boost Converter delivers 54v and about 1175 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
https://endless-sphere.com/forums/viewt ... =2&t=90369

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