102V DC to 12V DC converters

[Lemlux]

All DC to DC converters I've seen on ES seem to peak at a nominal input voltage of no more than 72V.

I am powering an ebike with a 32S 15Ah Headway LiFePO4 battery pack. Nominal output is 3.2V x 32 cells = 102.4V and peak output is 3.55V * 32 cells = 113.6V. (cell balancers bleed off individual cell voltages > 3.55V.) System Low Voltage Cutoff is 95V.

My SST50 LED Headlight draw at 3.6V is a max of 6A. Headlight buck circuit control converts input voltage between 6V and 24V to 3.6V at efficiencies declining from 92% at 6V down to 81% at 24V.

LED turn signal draw should be minimal.

Automotive horn (or horn set pair) will draw roughly 20A per horn at either 12.0V or 13.8V.

During a google search for converters that will convert my 32S Headway pack with nominal input voltage of 102V and peak voltage of <116V the following data sheet from a UK firm PDF for a 500W converter and a US firm, Vicor, for 150W or 250W output are the most easily found products I encountered.

http://www.whatpowersupply.com/products.asp?cat=DC%20to%20DC%20Convertor

http://cdn.vicorpower.com/documents/datasheets/ds_150vin-mini-family.pdf

Any other ideas for a non-mainstream DC to DC converter that is likely to be more cost effective that simply carrying a separate 12V battery?

 

[cal3thousand]

If you are using LEDs is it necessary have a 12V circuit? (automotive based LEDs?)

On my High voltage bike, for simplicity's sake, I will use a 3S2P block of 18650 cells with a buck driver regulating the voltage. Should last a week before needing to charge. It's much more simple and efficient versus bringing 24S full pack voltage down that far.

One thing you could consider is tapping a smaller section of your pack to ease the DC-DC conversion. This would be OK, if you are only running the lights on very low draw and keep an eye on it. You wouldn't want that circuit to drag that section out of balance with the rest of the pack by too much. For signaling LEDs, you should be ok. But this is like those BMSes that are using only 1 cell... a bit risky without the proper awareness.

 

[amberwolf]

I have some here that will work at around that level input; not sure if they will go as low as 102V input, though:
http://www.endless-sphere.com/forums/viewtopic.php?p=555639#p555639
EDIT: No, they wont' work:
http://www.endless-sphere.com/forums/viewtopic.php?p=559930#p559930
needs at least 120.9VDC to get 12.00V output.

Your best bet might be 120VAC input / 12VDC output LCD monitor power supplies, as they will probalby run on your pack voltage, and supply up to 3A for most fo the ones I've seen.

 

[skeetab5780]

ya i agree just use an old lcd monitor power supply or a laptop charger, i used a cell phone charger at 20s and it powered the 120 input fine

 

[ohzee]

I can probably get ahold of some old lcd power supplies if your interested in paying the shipping charge.
Will need to check out at work tomorrow.

 

[Lemlux]

Thanks for the ideas and offers.

I've decided to live with a slight weight penalty and to leave my main battery alone.

I bought my first LIPO brick today, a 4S 5300 mAh 40C pack that will power my lights and horns. Haven't yet decided where I'll mount the 4S LIPO pack. Maybe there'll be room in the triangle bag.