48v to 12v step down converter?

midijeep · July 2016

I want to run directly off my 48v battery bank , four 12v LED lights. I will put a load center with breakers between the battery bank and lights. The wiring coming off the load center is 10 gauge wiring, which is going to each of the lights.
I am in need of some advice to step down the voltage from 48v to 12v.
I am looking at these two converters and a load center panel:

Load center panel
http://www.backwoodssolar.com/six-circuit-load-center-kit

and

Dc to Dc converter #1
http://www.ebay.com/itm/like/391501899600?lpid=82&chn=ps&ul_noapp=true

and

Dc to Dc converter #2
http://www.backwoodssolar.com/ppt12-48-10-r12-step-down-converter

Do you have any recommendations or advice?

Thanks
Bj

mike95490 · July 2016

the Golf Cart DC Converter 48V to 12V Step Down VOLTAGE 20 A
likely has too much overhead and no attention to efficiency
The backwoods model is way too expensive

What is the amp load of your LED lights when all are turned on ? You only need a DC-DC converter that can supply 130% of that
here's a site with a lot of choices
http://www.digikey.com search for DC-DC and they have 10,000's of them Narrow down the values you need.

midijeep · July 2016

Total amps with all led lights on will be 5 amps at 12v

jonr · July 2016

Be sure that it can handle the maximum voltage that your bank will ever see (when equalizing). Ie, much more than 48V. I'd get one speced for 10A - this should provide good heat dissipation and be close to peak efficiency.

westbranch · July 2016

Are you going to have point-of-use converters , using 48V to the point of use or are you going to down convert and send 12 V to point of use? The latter is far less efficient in wire losses than 48V...

midijeep · July 2016

westbranch said:

Are you going to have point-of-use converters , using 48V to the point of use or are you going to down convert and send 12 V to point of use? The latter is far less efficient in wire losses than 48V...

I'm not sure? How would you wire/put together the more efficient method?

westbranch · July 2016

you 'send' 48 volts to all points of use and then change to 12 volts , but remember that you will have add: PV in voltages up into the 80+ volts range! during Absorb and EQ times. add: And that the Cc will output to the max V set for these stages , which can upset your inverter or whatever that is a '48 V' device.

oil pan 4 · July 2016

Holey crap. I thought 48v banks only equalized at like 64v max.

The simplest cheapest thing I can think of is wire each light to a 12v battery. Just make sure you turn them all on and off at the same time.

This is one of the draw backs of 48v, not much is made to directly run off 48v.

BB. · July 2016

Is the 48 volt system driving some other (much larger) loads?

Will you have 120 or 240 VAC voltage available (i.e., an AC inverter that is already running 24x7)?

If so, perhaps you would just wire out the AC power to the LEDs point of usage--And use AC rated LEDs? Can be cheaper for 120/240 VAC LED bulbs, and it is much cheaper/easier to run your AC power much longer distances with much smaller AWG wiring.

-Bill

midijeep · July 2016

For my setup I have:

Grid-tied System with battery backup (48v bank)
SMA SunnyBoy 3000TL-US-22
SMA Sunny Island 6048
Midnite Solar E-Panel
Midnite Solae Autoformer (gives me the 240v)
48v Battery bank

The room is already wire with AC lighting but when that goes down I want to have the DC lighting to take over by running them directly off the 48v battery bank. All the solar equipment is in this room. From what I understand using the SMA equipment, I have no choice in what voltage to run the battery bank. It has to be 48volts.

I would like to place a DC loads center between the 48v battery bank and 12v LED lights for safety and maintenance.

There will be no other loads on the 48vDC to 12v DC other than the LED lights.

Brock · July 2016

I had some small 12v loads (routers, ooma and a laptop) and I ended up using an old 12v battery and a morningstar charge controller (rated for 6 amps I believe) I had sitting around. Then I just connected the charge controller to the 48v bank (on the solar input) and the other side to the small 12v battery and let it do it's thing. The nice part was the small 12v battery acted as buffer and an additional backup beyond the inverter.

But I ultimately changed to what Bill suggested and went to 120vac to 12vdc route and just used the inverter to power the loads, less work, less wiring, less battery to maintain, but it was redundant backup.

jonr · July 2016

> The simplest cheapest thing I can think of is wire each light to a 12v battery. Just make sure you turn them all on and off at the same time.

Or if "all on" is too inconvenient, buy a series battery bank equalizer (about $55 for 4x12V batteries). Cheaper than some DC-DC converters (and probably beneficial even without uneven current loads).

Yet another option is to look closely at the LED drive circuit. They are current controlled, so if the components can tolerate 48V (nominal), it won't hurt the LED. Even a LED driver designed for 120VAC might run fine on 48V DC (it's typically rectified then buck converted).

westbranch · July 2016

Made an addition to clarify my previous post, sorry for any confusion.

midijeep · July 2016

I found some 48v LED lights. Instead of stepping the DC voltage down from 48v to 12v to power the lights, would coming directly from the 48v battery bank to the DC load center, then to the 48V lights be a better option?

westbranch · July 2016

That would probably be the most efficient way to do it. Now you will need CB's , switches etc to handle 48 Volts or higher..
.
Are those LED's able to handle the Absorb and EQ voltages if they were turned on during those charge phases?

vince · July 2016

I am running some several dc-dc (10A) converters to run 12 and 24 V lights, pumps and appliances from my 48V bank. No problems handling the 60V max. and the output of the converter is very stable regardless of the input which may range from 49 to 58V.

midijeep · July 2016

Could you give the make/model of the converter you are using?

vince said:

I am running some several dc-dc (10A) converters to run 12 and 24 V lights, pumps and appliances from my 48V bank. No problems handling the 60V max. and the output of the converter is very stable regardless of the input which may range from 49 to 58V.

jonr · July 2016

Interesting, I took a standard 120VAC Cree LED lightbulb and applied 30VDC and it worked fine.

vince · July 2016

I got the converter from ebay http://www.ebay.com/itm/DC-DC-Step-down-Module-48V-to-24V-10A-240W-Car-Power-Supply-Inverter-Converter-/181571959289?hash=item2a468839f9:g:YwgAAOSwr81UUEfm

midijeep · July 2016

vince said:

I got the converter from ebay http://www.ebay.com/itm/DC-DC-Step-down-Module-48V-to-24V-10A-240W-Car-Power-Supply-Inverter-Converter-/181571959289?hash=item2a468839f9:g:YwgAAOSwr81UUEfm

Did you put fuses between the battery and lights?

vince · August 2016

No, the transformers have build in protection and the wiring could handle the load

48v to 12v step down converter?

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