Power converter

[Swgraham2]

I have a 480 watt solar array and a 24 volt battery bank and a 12Volt inverter. I’ve watched Will’s 12V Vs 24V comparison YouTube video several times and understand that I need a ~$40 converter.

Can someone recommend one please? Or will this Amazon converter work? https://a.co/d/guRvvhc

Gratefully
Steve

 

[v_green57]

You really shouldn't run a 12V inverter off a 24V battery system via a DC-DC converter. Unless it is very small.

Bad stuff can happen.

Far better to get a 24V inverter. Or reconfigure your battery bank to 12V.

Now, there will likely be some responses like "I am doing/have done it and it works!" but it still is not a good idea.

 

[Swgraham2]

All my stuff runs off 12V though. Laptop, TV, etc. I don’t have 24 volt appliances. What runs off 24volts?

 

[Rednecktek]

All my stuff runs off 12V though. Laptop, TV, etc. I don’t have 24 volt appliances. What runs off 24volts?

Not much until you get into marine stuff where 24v is pretty common, but being marine stuff is also $$$$$ for the privelidge. I would lean towards reconfiguring to a 12v setup, especially if all your stuff is 12v already. You can get converters, I have a couple myself from a 24v project, but when it says "300w" on the converter, it really means "299w MAX" and there's no surge capacity.

The only thing a 24v system buys you is lower wire and fuse sizes. It is nice if you run a mostly 120v setup and only need a little 12v through a converter, but if (like me) you have significant 12v DC loads then the cost and hassle of large enough converters is outweighed by the cost of the heavier wire and breakers.

If you do decide to add in a converter, I have been happy with my 60a Uxcell version that is currently in use at camp.

 

[Bud Martin]

All my stuff runs off 12V though. Laptop, TV, etc. I don’t have 24 volt appliances. What runs off 24volts?

What are the power requirement of your loads?
So you have 12V Loads + you also need 12VDC to 120VAC inverter to run AC Loads?

 

[Swgraham2]

Thanks, Green57. Can you clarify last sentence, first a paragraph? “Unless it is very small” what is “it” referring to? Thanks

 

[Swgraham2]

What are the power requirement of your loads?
So you have 12V Loads + you also need 12VDC to 120VAC inverter to run AC Loads?

Correct, I currently convert 12VDC to 120VAC through a 12V 1,000 watt inverter. I recently grew my array to 480 watts so I need need to reconfigure my 12volt bank to 24 volts.

 

[RCinFLA]

Take the money you will spend on a 24v to 12v DC-DC converter and put it toward a 24v 1000 watt inverter.

Even if you buy a DC-DC converter large enough to handle that much power you will be taking the additional idle loss of each device and efficiency loss of each device.

 

[timselectric]

I don't understand why you want to convert your battery to 24v, if everything else is going to stay 12v.

 

[v_green57]

Thanks, Green57. Can you clarify last sentence, first a paragraph? “Unless it is very small” what is “it” referring to? Thanks

Inverters can throw interesting surges and other stuff that could:

kill a DC-DC converter
cause it to shut off
other undesirable behavior

Inverters assume they are always connected to a battery bank, with its ability to supply almost infinite current for short durations. DC-DC can't do that.

Also, as RC noted, you'll be giving up another 5% or so in efficiency losses. The inverter itself will be around 5% as well.

I get what you need to do as I am running a 24V battery bank with two travel trailers at my boondocks site. The 12V lights, furnace, etc. in them are nice and efficient and make sense for me. But I have an old DR1524 24V inverter for my minimal AC requirements. I run the 12V stuff off a Samlex 30A 24-12 DC-DC converter.

24VDC battery makes wiring easier, as you probably already know.


'

 

[v_green57]

Correct, I currently convert 12VDC to 120VAC through a 12V 1,000 watt inverter. I recently grew my array to 480 watts so I need need to reconfigure my 12volt bank to 24 volts.

Ah, so you ran into the 40A limit of your charge controller...

 

[timselectric]

Just get a bigger, or second charge controller.
No need to complicate the system and lose efficiency.

 

[v_green57]

Just get a bigger, or second charge controller.
No need to complicate the system and lose efficiency.

Yep, I believe this is the right answer, now that we know what triggered your question and that we were correct about that.

Two (hopefully identical) CC's work extremely well if they are hyper-adjustable (voltages can be tweaked down to 0.01V).

I have been using two EPEVER 4210's this way. The 50A+/higher V versions didn't arrive for several years so this was my method to get 80A of charge current.

You need to spend a few days adjusting charge voltages such that they max out charge current and then both go to float at about the same time. I have one of mine set to hit Float 10 min. before the other, which helps when both of them have the same amt. of panel attached.

 

[Swgraham2]

I don't understand why you want to convert your battery to 24v, if everything else is going to stay 12v.

my MPPT is a 20amp 12/24 volt. My array is 480 watts, don’t I need 24volt to handle all that solar panel wattage?

 

[Rednecktek]

my MPPT is a 20amp 12/24 volt. My array is 480 watts, don’t I need 24volt to handle all that solar panel wattage?

Either that or a 40a SCC, or 2x 20a SCC's, or a 60a SCC. You've limited yourself by having such a small SCC. So yes, you could get 480w by going to a 24v system, but with so many 12v loads it just adds complications down the line.

 

[timselectric]

don’t I need 24volt to handle all that solar panel wattage?

No
Just a large enough 12v charge controller, or a second one.

 

[Hank Waconda]

On one of my arrays I run 2-200 24dcv panels in series into a 3210an charging a 12dcv 570ah battery bank and it does well. The dc to dc conversion work really well this way with the MPPT scc's.