48v 36v 12v converter

1

1958 greyhound

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May 13, 2017
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What is everyone using for a 48v to 13.8v converter?
The biggest i find is about 60 amps

I have a 5kw rv set up thats not installed yet.
The motorhome has both 12v and a trace engineering 2500w inverter.

I have 2 options
going to 36v or 48v and using a buck converter for everything.
The inverter draws 275 amps

Or leaving the 4s and only using a buck or multiple bucks on the 12v side and feed the inverter straight off the battery.

If the inverter is 16.5 volts max, i have to confirm this, they made some that were 15.5 max.
 
For large loads, eg > about 20A, step down converters are too lossy.
For 5kW sized inverters you're better at 48V battery for that - your existing 12V inverter will be loosing a lot of efficiency due to those massive currents.
At 48V, the battery pack voltages match better too.
You can use multiple step down bucks, eg to run your 12V lights & electronics, etc
36V gear seems like a less popular option these days.
 
Step down for small Gear. The inverter and big Gear should run on the high voltage. That Will be more economic over time
 
High Voltage and Low Amps = Less losses due to resistance and heat.

I agree with Redpacket and daromer, go 48V, and use bucks for lights and such. Once you get them set, you shouldn't have to touch them again. Use a buck for each circuit to keep the buck from over heating or reaching its max amp output
 
And for good sake turn the converters off when the appliance isnt in use... Otherwise you loose more energy :)
 
If I get a 48V pack, which means 13S, can I plug my 12V electronics/lights appliances directly on 3 cells from my 48S battery ? Will the BMS manage that ?
or, Should I use a converter to step down the 48V of the whole pack to 12V ?
 
NO. You should NOT hook up things in the middle. its better to use a buck converter. You can potentially use an active BMS but in long run its cheaper and more efficient to just run a proper buck converter :)

14s will most likely be better fit for 48VDC. Depending on your gear that is.
 
daromer said:
NO. You should NOT hook up things in the middle. its better to use a buck converter. You can potentially use an active BMS but in long run its cheaper and more efficient to just run a proper buck converter :)
Click to expand...

You mean something like this ?
 
Yeap. The linked is max 100W continues so you are aware of that :)
 
Charlycop said:
daromer said:
NO. You should NOT hook up things in the middle. its better to use a buck converter. You can potentially use an active BMS but in long run its cheaper and more efficient to just run a proper buck converter :)
Click to expand...

You mean something like this ?
Click to expand...

Something like this would be rather more dependable - you also need to ensure whatever that you purchase functions across the full min/max range of your nominally 48v battery (which will likely be nearer to 60v when full)

https://uk.rs-online.com/web/p/isolated-dc-dc-converters/6783672/ - you'll likely not need the isolated version, and perhaps a couple of lower rated units might be advantageous.
 
Sean said:
Something like this would be rather more dependable - you also need to ensure whatever that you purchase functions across the full min/max range of your nominally 48v battery (which will likely be nearer to 60v when full)

https://uk.rs-online.com/web/p/isolated-dc-dc-converters/6783672/ - you'll likely not need the isolated version, and perhaps a couple of lower rated units might be advantageous.
Click to expand...

OK, you mean I should stabilize my output battery pack voltage to 48V, before I plug to my 48V -> 12V buck step down, right ?
 
No, the converter need to work between you max and min voltage range.
 
Is there some way to take multiple splits from the battery isolate with diodes?
 
I could split some of the loads.

The inverter i have is a trace engineering voyager 2500w
I looked today for the max input volts and couldnt find.

The inverters they make have 15.5 or 16.5 max, if its 15.5 its going to blow this whole deal out of the water.

When you price a 3000 watter dc to dc converter that isnt a pos your eyes fall out.
 
1958greyhound said:
When you price a 3000 watter dc to dc converter that isnt a pos your eyes fall out.
Click to expand...

LoL - which is why looking at 48V inverters is much better!

So if you leave the inverter load out of the 12V numbers, how many amps of 12V are you using? or is the above 100-200A without the inverter already (yikes!)
 
I dont know for sure but im going to guess 20-50 amp max.

The problem i have is the new rv is already wired and the inverter is already installed.

So i get a converter or a converter and a dif inverter.
 
1958greyhound said:
I dont know for sure but im going to guess 20-50 amp max.

The problem i have is the new rv is already wired and the inverter is already installed.

So i get a converter or a converter and a dif inverter.
Click to expand...

20-50 A is do-able with converters.

The wiring should not have to change that much.

A big converter > inverter input won't work out well - wasted money & that "i told you"lookfrom the partner will happen!
 
there is way to many guesses here now!

Please DRAW up your current setup exactly how its wired and what devices you have. Then add to the right the new stuff and upload that IMAGE here.


We can just guestimate what you need and want. You dont seem to know your self how much you run on 12V and therefore its impossible for us to tell go 48v.....
 
The questions have already been answered.

Theres no point in me going further with a lithium install in this.
a converter to feed the inverter is just as much money as buying a new inverter.
Since i cant feed the inverter there would need to be lead acid and lithium.

If i was build a system from the ground up i would start 48 volt and use a couple small converters for the 12v stuff
 
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