DC to DC Converters

[eBikeJunkie]

Hey All, I would really like to move my lights over to my main pack for my bike.

My pack is currently: 22s3p = 84~v

I need to get it down to 8.4v

I have seen MANY MANY dc to dc converters out there, but I just cannot seem to find one with an input voltage of 82+V.

Does anyone know where I might be able to find that, or does anyone know how to assemble this if no one makes it?

Thanks in advance!!

 

[ambroseliao]

Look in your junk box for a wall wart with your desired DC output. Many of these can be used with DC just fine.

 

[dnmun]

some people use the AC adapter or charger brick for laptops and other low voltage devices.

you put the DC input to the AC plug according to them but i have always felt it would be better to put the DC directly onto the input capacitors and bypass the rectifier diode bridge.

if you use the DC through the AC plug then only half the rectifier is working so the capacity is cut in half.

 

[eBikeJunkie]

Sorry, I think there is some confusion. I dont want to go from AC to DC... I want to take DC 84V and bring it down to 8.4vDC

I want to use my main pack for the lights instead of using two separate batteries for each, the bike and the light.

Hope that clears it up a bit.

Thanks!

 

[ambroseliao]

No misunderstanding. Some wall warts will work with DC.

 

[eBikeJunkie]

I didnt know that. That would be so cool. I will give that a shot on a couple wall warts I have laying around.
When I hook it up, does polarity matter on the wall wart?

Has anyone run this type of a setup?:

84VDC -> Wall Wart AC -> Output of 8.4VDC

Thanks again!

 

[bigmoose]

some people use the AC adapter or charger brick for laptops and other low voltage devices.

you put the DC input to the AC plug according to them but i have always felt it would be better to put the DC directly onto the input capacitors and bypass the rectifier diode bridge.

if you use the DC through the AC plug then only half the rectifier is working so the capacity is cut in half.

Just to clarify. You can put DC into the AC input of these converters. The internal DC bus will be two diode drops (2 x 0.6 Volts) below the DC you input. The issue is that that input power will go through two diodes (one per leg) at 100% duty cycle instead of alternated between 4 diodes (2 per leg) at 50% duty cycle. Therefore at maximum power the input diodes will be seeing twice the VxI (0.6xI) heating than they would on an AC input. At partial power there should absolutely be no issue. Only at maximum output power MAY there be an issue... but likely not. Hope this helps qualify the risk.

 

[eBikeJunkie]

thank you for clarifying things for sure!!

Just to make sure, but even if this thing goes puff, is there any risk to my pack?

Ill let you know how I make out later on today. I will give it a shot, thanks for the tutelage

 

[steelmesh]

Hey All, I would really like to move my lights over to my main pack for my bike.

My pack is currently: 22s3p = 84~v

I need to get it down to 8.4v

I have seen MANY MANY dc to dc converters out there, but I just cannot seem to find one with an input voltage of 82+V.

Does anyone know where I might be able to find that, or does anyone know how to assemble this if no one makes it?

Thanks in advance!!

Buck It! http://en.wikipedia.org/wiki/Buck_converter

 

[meelis11]

Hi,
does anyone know if LED lights designed for 8.4V lion battery can accept 12V input instead of 8.4V ?
I have this kind of light and 12V DC-DC converter, can I use it or it burns/smokes my led light?

Meelis

 

[eva-michael]

Generally a 72V DC to DC converter can work under 90V. But generally their output will be DC 12V. It's a bit difficult to buy one which is output 8.4V. Check if you light can use 12V. It will probably ok.

 

[steelmesh]

Hi,
does anyone know if LED lights designed for 8.4V lion battery can accept 12V input instead of 8.4V ?
I have this kind of light and 12V DC-DC converter, can I use it or it burns/smokes my led light?

Meelis

This fully adjustable LDO regulator LM350 was for my servo shifter testing here: http://i.imgur.com/PRMzRdH.jpg. I used 12v input for a 8v output to the servo, but can handle 35v input. Gigantic cap for servo surges. Read page six is the diagram I used: http://www.ti.com/lit/ds/symlink/lm350-n.pdf this is as simple an adjustable regulator as it gets and probably not that bad efficiency because of your smaller V drop. Use a heat sink, these will just cut out on you overheat protection.

 

[meelis11]

Generally a 72V DC to DC converter can work under 90V. But generally their output will be DC 12V. It's a bit difficult to buy one which is output 8.4V. Check if you light can use 12V. It will probably ok.

How can I check if LED light driver supports 12V? Should I open it to see driver chip or something?
DC-DC converter is 15-55V input, 12V output, 3A max
LED light is "CREE LED XML XM-L T6 LED 1200Lm Bicycle Light Bike Lamp HeadLight headLamp Set"
I am using 12S LIPO: about 48V

 

[teklektik]

does anyone know if LED lights designed for 8.4V lion battery can accept 12V input instead of 8.4V ?

LED light is "CREE LED XML XM-L T6 LED 1200Lm Bicycle Light Bike Lamp HeadLight headLamp Set"
I am using 12S LIPO: about 48V

Both Lyen and cell_man sell this converter. 3A rating.

I would recommend the Lyen/cell_man unit which has a good input voltage rating for your pack, adequate current, and can be dialed in to exactly the voltage you need.

As to whether the light will work on 12v or not - it sort of depends on how the light is built. At the end of the day, the LEDs are rated by current not by voltage so there is a fair probability that the light contains a constant current supply that can handle the small voltage swing of a known battery type (8.4 lion) - hooking it to 12v will probably not hurt the LEDs - but the regulator may overheat... So - open it up, put you finger on the regulator device and plug it into 12v - if you get burned PDQ, turn it off. On the other hand, if you open it an find only a resistor, just recalculate the value for 12v and replace it.

 

[meelis11]

does anyone know if LED lights designed for 8.4V lion battery can accept 12V input instead of 8.4V ?

LED light is "CREE LED XML XM-L T6 LED 1200Lm Bicycle Light Bike Lamp HeadLight headLamp Set"
I am using 12S LIPO: about 48V

Both Lyen and cell_man sell this converter. 3A rating.

I would recommend the Lyen/cell_man unit which has a good input voltage rating for your pack, adequate current, and can be dialed in to exactly the voltage you need.

As to whether the light will work on 12v or not - it sort of depends on how the light is built. At the end of the day, the LEDs are rated by current not by voltage so there is a fair probability that the light contains a constant current supply that can handle the small voltage swing of a known battery type (8.4 lion) - hooking it to 12v will probably not hurt the LEDs - but the regulator may overheat... So - open it up, put you finger on the regulator device and plug it into 12v - if you get burned PDQ, turn it off. On the other hand, if you open it an find only a resistor, just recalculate the value for 12v and replace it.

9W powerleds are not driven by just resistors. I am sure that there is constant current driver (It has 3 brightness modes and strobe light)
I may test it by using variable DC-DC buck-boost converter I have - gradually turning more voltage and measuring drivers temperature. Cannot use that buck-boost converter on my bike - it cannot handle 50V input, but should be good to test led driver input voltages.

 

[docnjoj]

My Magicshine works fine on 12 v from a Lyen converter.
otherDoc

 

[cal3thousand]

does anyone know if LED lights designed for 8.4V lion battery can accept 12V input instead of 8.4V ?

LED light is "CREE LED XML XM-L T6 LED 1200Lm Bicycle Light Bike Lamp HeadLight headLamp Set"
I am using 12S LIPO: about 48V

Both Lyen and cell_man sell this converter. 3A rating.

I would recommend the Lyen/cell_man unit which has a good input voltage rating for your pack, adequate current, and can be dialed in to exactly the voltage you need.

As to whether the light will work on 12v or not - it sort of depends on how the light is built. At the end of the day, the LEDs are rated by current not by voltage so there is a fair probability that the light contains a constant current supply that can handle the small voltage swing of a known battery type (8.4 lion) - hooking it to 12v will probably not hurt the LEDs - but the regulator may overheat... So - open it up, put you finger on the regulator device and plug it into 12v - if you get burned PDQ, turn it off. On the other hand, if you open it an find only a resistor, just recalculate the value for 12v and replace it.

I put ~50V (12S;HOC) into one of these things and some component popped with some fury. Sounded like a little firecracker. I bought 2 from Lyen, but I'm a bit nervous to try it again. I will test it on 6S first to see.

I think I'm going to research the suggestion to hook the DC straight to the input Caps of an AC/DC walwort.

 

[meelis11]

My Magicshine works fine on 12 v from a Lyen converter.
otherDoc

Tested today, my light is also happy with DC 12V - tested it with adjustable DC-DC converter - went slowly up from 8V and nothing did not feel that it wants to go hot and burn. Stopped in 12.2V, no need to test higher limits and risk burning my light regulator. It works also when only 3V is used, but is showing red led instead of green when input is under 6V. So no LVC built in, only red indicator light that it is time to recharge.

So probably any switching power supply/adapter works that outputs 5V, 9V, 12V or anything between and in label is saying AC 100-240V - DC 48V should be ok too, tested my lights charger and output voltage was in spec. It was without load, loaded test was not done because adapter and light are both using male jacks. Probably work, but I have 12V DC-DC converter already bought for powering light from 48V battery.

Meelis

 

[dehoov]

So is it not logicval to suggest that using the wall wart that came with my mitcross lite as DC to DC woudl be the right thing to do?

 

[cal3thousand]

So is it not logicval to suggest that using the wall wart that came with my mitcross lite as DC to DC woudl be the right thing to do?

Try it out

 

[LSBW]

I use old IBM T40 laptop power supply. Cost is free, well at least for me, or $7-10 on fleebay.
Works from my 80 v battery, and stable at as low as 70 volts.
Good for 16 volts and 3.5 Amp
IBM FRU # 02K6815

 

[spinningmagnets]

I was recently going over Teklektiks build. He used a Thunderstruck DC-DC converter, Green Galaxy 36-72V input, 10A 13.5V output, 120W.

This allowed him to use 12V lights and other components, a huge variety of selections.

http://endless-sphere.com/forums/viewtopic.php?f=6&t=36959&p=536905#p536878

 

[alsmith]

I got a couple of PSU's with 12V and also a 5V output which is handy, originally for external hard drives.

 

[dehoov]

So tried out a bunch of wall wart applicaitons for a few different lights last night. I even managed to get my 10 year old NiteRyder Strom HID to operate (battery died three years ago) - albeit not with (as I had hoped) the original wall wart but with (as a post above had also tried) a 12v 2A external hard disc drive psu. The 13.2v 2A original psu for the Storm did fire up the HID, but got hot and shut down after a few minutes. The 12v hard drive psu doesn't get the HID quite as bright as factory, but still probably over 1000 lumens, and stayed cool for a half an horu before I shut it down.

The Cygolite 400 mitycross (another dead battery light) works fine off the original psu - I think, but did not have it on for more than a few seconds. Going to take some voltmeter readings tonight and see if it stasy stable. Running off 48volt battery. Any concerns abotu drawing too many amps for these types of lights?

 

[Xrain]

Here are some options for the OP:

http://www.mouser.com/ProductDetail/Mean-Well/SD-150D-12/?qs=sGAEpiMZZMtwaiKVUtQsNRU%2fEBWfzYNE4JWrTd3p8HA%3d
http://www.mouser.com/ProductDetail/Mean-Well/SD-100D-12/?qs=sGAEpiMZZMtwaiKVUtQsNRU%2fEBWfzYNEdi1Mo6yaa1Q%3d
http://www.mouser.com/ProductDetail/Murata-Power-Solutions/RUW15SL12C/?qs=sGAEpiMZZMtwaiKVUtQsNcVRxBxOL%252bzaT%2fhewjQhzs4%3d

Didn't know what your current consumption was going to be so I gave a few options. I like the murata a lot if all you need is 15W, it's nice and compact and takes voltages from 16 - 160V.
Bit on the high side of things $$$ wise, but hey at least you have a better chance that it wont catch on fire...

Once you are at 12V there are a ton of DC/DC converters to get you to 8.2V.