cheap 200w 24v battery replace/upgrade idea. advice?

[cycleops612]

I t sounds an odd solution, but i wonder.

I have a 200w 24v bike, no doubt capable of 250w.

i also have a 36v bottle 12 ah battery, oldish but fine, just not up to a 350w motor. so am thinking of using it as a handme down on the 24v bike.

natch i keep charging it w/ a 36v charger.

NB - if it works & i can live with200/250w, i should have free~ handmedown batteries for life

SO:

any comments on this as a solution:

Description

200W DC-DC high voltage power synchronous buck module
8-60V wide voltage input, 1-36V stepless adjustable output
The maximum peak output current 15A
Perfect ultra-efficient circuit design up to 94% Low Ripple

parameter:
Name: 200W adjustable synchronous buck module
Type: Non-isolated step-down module (BUCK)
Aluminum housing Size: 70x38x31mm / 27.5 "x15" x12 "
Input voltage: 8-55V (limit 60V, please leave allowance)
Output voltage: 1-36V continuously adjustable (the default output 12V)
Output Current: 10A MAX15A normal
Output power: natural cooling ventilated long-term power 100W
To enhance heat dissipation up to 200W
Such as long working hours, please note left margin and make the heat rise
Operating temperature: -10 to +85 degrees
Operating frequency: 180KHz
Conversion efficiency: up to 94%
Overcurrent protection: Yes (the output current exceeds (15A) current maximum sample protection only)
Reverse polarity protection: (reverse does not burn)

http://www.ebay.com.au/itm/Voltage-Power-Buck-Converter-Step-Down-Module-200W-15A-DC-DC-8-60V-TO-1-36V-12V-/131748054788?hash=item1eaccbc704:g:AF4AAOSwxp9W4REl

(~$10 US)

am currently debating it with some mates by email

re my question:

"could I use 2x converters in parallel to double capacity/halve load?"

His informed response:

"Hard to tell if you can couple 2 together or not, but could be possible with isolating diodes anyway.

Cheap & includes case unlike the $77 (other) one which was open & non-isolated (input & output have common rail), so (the other $77 one) CAN'T be coupled together."

So yeah, for that sort of money and in my situation (maybe not so uncommon, a lotta crap 24v scooters etc out there hardly worth the price of a new battery, but given their modest needs & most soon get sick of the supplied battery), i am seriously considering it, and if so, i really like idea of using 2x convertors.

any comments/advice/debate welcomed.

 

[Peter.bp]

Isn't it better to modify controller to 36V?

 

[cycleops612]

Isn't it better to modify controller to 36V?

tell me more.

I knew you could cheat a bit (as I intended to do, like ~27v), but not that much - ~12v or 50%?

so i can run a 24v motor & controller on 36v? How?

 

[Peter.bp]

First you have to check the power stage of the controller:
Check voltage rating on capacitors, on 24V controller they are probably 35V. These capacitors you'll have to replace with 50V ones.
Check output stage mosfets, if you have something like 75N75, you can keep them as then they're designed for voltages up to 75V.
Check how is supplied CPU and mosfet drivers: you can have only LM7812 for drivers and LM7805 for CPU, you'll need to add serial resistors on positive input of 7812...
If you use regen braking, you'll have to cheat battery voltage on the CPU, it should be somewhere resistor divider, which is used for measuring battery voltage. Easiest way is to connect the controller to variable PSU and measure voltages on pins on CPU. Which ever pin has voltage between 2 and 4V is analogue input. Searching for battery voltage input to CPU is done when the controller has disconnected load as well as throttle input is set to 0V. Variation of voltage on PSU from 20 to 26V should reflect proportionally to voltage variation on battery voltage input pin.

If you don't need regenerative braking, it is much easier as then you only need to adopt voltage regulators for drivers and CPU...

Of course, this task is for person skilled enough in electronics, try to find someone in your area to help you with this if you don't have enough skills for this.

Try to open the controller and take detailed photographs of electronics inside, it should be much easier to see what are possibilities for modification...

Otherwise, maybe it is cheaper just to by another controller for 36V?

 

[Samd]

The standard controller will handle 36v no problem. I've not seen one with less that 52v caps in three years or more...
Although the converter experiment is intriguing it really isnt necessary.

 

[cycleops612]

Your tagline samd, puts the whore before Descarte.

 

[cycleops612]

Guys, before i forget my manners, ta so much. You are wonderful.

I need to put it on the warmer til i get my act together a bit here. I need to do some research, as u say, on what exactly i have e.g.

 

[cycleops612]

One thing tho?

"Up to 94% efficiency" sounds comforting, but pretty meaningless.

Why the big heatsink if so efficient (admittedly just ~1 watt can get hot)?

Can anyone elaborate on this? - what are non/ideal conversion factors affecting efficiency?

Others have said there is a lot of waste heat, & hence power.