48V to 12v Stepdown converters?

I am researching how to go from my 48V pack down to 12v

My drive system is 48V, but everything else (running lights, headlamps, radio, etc) is typical 12v automotive (actually 13.8v) stuff. I don’t want to carry a seperate battery just for 12v stuff…

I have seen a few 48V/12v DC/DC converters…they run about $124 for 100watts at 88% efficiency. Most are adjustable to 13.2v (12v + 10% boost)

I was just wondering if other people had used these, or had a prefered source. (maybe one that is native 13.8v)

Bob S

If you have not bought a controller yet, i would suggest looking into a controller that has a DC/DC converter built in. Many do. Otherwise, what are you converting? A motorcycle? I hope you arent doing a care with those voltages!

Nope, just Quadracycle. It will weigh in at about 150#'s

I was on planning on using the crystalyte 4840 controller and the Phoenix 900W Hub motor. It is supposedly going to be a “go get groceries cart”…

I figure with 2 x 48V Li-packs (22A-hrs ea. 22Lb’s ea.)I will be able to go just about anywhere I go now, just a bit slower. Top speed will be about 29+ Maybe more with only one rider. The cart has room for two…

But, my wife is going to want headlamps, running lights, a horn and maybe even a radio… ah luxury…

Bob

What is the voltage of each cell? Because if it is a multible of 12, then you can wire the batteries in two ways: Parrallel for the traction motor, and series for the 12v accessories.

Depending of the final configuration it may be a single 48v “Pack” or two “packs” of 24v. I am trying to stay away from individual 12v batteries as then I would need 4 individual chargers, and need to plug/un-plug many connectors each time. I am leaning towords multiples of a 22Ahr NiMh or Li-Poly 48v pack for simplicity. I may start with NiMh until the price comes down further on LifePO4 batteries, but in either case the pack would be 48v with no “taps” at 12v possible.

Bob

What batteries are you using? Have a link? Why would you need 4 individual chargers if you used 12 volt? I think it would uncomplicate things if you were going to go the route you are going. You coudl have a 12v cell system totaling 48v. It would be wired two ways: parallel for driving, and series for 12v. and for charging from a 12v charger.

Sorry for the delay…

Here is the set I am thinking about…

http://electricrider.com/batteries/eon254860.htm

or if I can get something without the blast-box… but finding a 48V Li-Ion has been hard…

[QUOTE=rsisson;869]Sorry for the delay…

Here is the set I am thinking about…

http://electricrider.com/batteries/eon254860.htm

or if I can get something without the blast-box… but finding a 48V Li-Ion has been hard…[/QUOTE]

These are the lithium batteries i am using http://www.gmbattery.com/English/ProductView.asp?ID=92&SortID=101 , and i am using a bms from metricmind.com

here is the DC-DC converter I am using :
http://www.evparts.com/shopping/product_details.php?id=873&product_id=4110

its cheap and it should run my lights…

lights maybe, but deffinantly not lights and radio! :eek:

Nope its a motorcycle, no radio.

Do you have any electronics experience? As in component level? It’s easy to build a regulated dc/dc converter with the 3524 PWM IC and a pair of Mosfets like the IRFz44. About $10 in parts excluding the heatsink. Should be good for about 50a depending on the switching frequency.

I used to build stuff like that all the time… No I watch ebay for a completed one.

I saw an adjustable 48v-12v 50A converter on ebay for about $50. I can’t touch that as it was already in a moisture tight enclosure, and had all the protection stuff built on. All I might do is get a temp controlled computer fan and mount it on the case…

Thanks for the thought though…