Keep 12v or change to 24v?

[drharris2223]

I currently have 400w of panels on my roof. Not optimal angle. Was wanting to add additional array to face of wall that gets morning sunshine. I find my rover 40 only allows for 560w of panels for 12v and double that for 24v.

I need to get an additional battery but in order to facilitate an additional 400w array what would be recommended for both cost and long term upgradability. A 24v upgrade of my inverter? Or add another charge controller for additional array and keep 12v.

And on that note what would it take to incorporate wind power as well? I would have to get a hybrid controller but would keep everything 12v.

I was under the assumption 24v was better than 12v but from what I see each uses power equally out of a battery bank but running less amps while doing so.

Thanks for input.

 

[rodrick]

How large is your 12 volt inverter do you need to upgrade?

Do you have 12 volt loads ie lights pumps fans ect

 

[Rednecktek]

If you go to 24v you'd need a new inverter at least. If you have any 12v loads you'd have to get a converter to feed those.

With such different angles, the better idea would be to have another controller for your morning sun array and just parallel it in. Let the 2 controllers each try to do their job and they'll work best with their own arrays.

 

[pollenface]

Compare some costs, another charge controller for more solar at 12, or a 24v inverter of your requirements

My 12v system has 1kw of PV split between 2 controllers. My 12v inverter is rock solid so i can't bring myself to make it redundant.

 

[Suijkerbuijk]

Rule is easy .

12 volt inverter optimal vs max 1000/2000 watts.
24 volt inverter optimal vs max 2000/4000 watts .
48 volt inverter optimal vs max 4000/8000 watts.

So wat are you use now vs the future.?
Not forget wat u use you need to stop back in.
From solar to gridd.
So you charger have to charge it back up and needs over power so you can use it on the day to.
All in the 5/6 hours you have max sub light .

Wind power is nice but its only use full in the winter.

This person have test cheap wind energie

 

[pollenface]

Rule is easy .

12 volt inverter optimal vs max 1000/2000 watts.
24 volt inverter optimal vs max 2000/4000 watts .
48 volt inverter optimal vs max 4000/8000 watts.

what rule is that?

My 2000w 12v inverter ticks along just fine, my friends 3000w 12v inverter also ticks along just fine, runs his welder, etc.

 

[Suijkerbuijk]

what rule is that?

My 2000w 12v inverter ticks along just fine, my friends 3000w 12v inverter also ticks along just fine, runs his welder, etc.

Its the rule about the cost of the cable you need .
Not the power use .
If you go to 24 volt the price of the Inverter and the cable go down .
And amps you need to use it.

 

[time2roll]

I would stay with 12v if the inverter etc is already 12v.

 

[pollenface]

Its the rule about the cost of the cable you need .

I know what you're saying, but it's not a rule

The price of the inverter depends on the make/model of inverter and who you buy it from.

 

[Suijkerbuijk]

I know what you're saying, but it's not a rule

No its not you are correct.
More a advice .

 

[Texas-Mark]

Its the rule about the cost of the cable you need .
Not the power use .

Even that is not a good rule. An inverter can be 2 feet away from the battery so cable cost is negligible.

 

[time2roll]

More guideline on a new system than a 'rule' to update existing.

 

[robbob2112]

More guideline on a new system than a 'rule' to update existing.

It is a good rule of thumb to build a system by. If you already have some parts you may be locked in.

 

[drharris2223]

If you go to 24v you'd need a new inverter at least. If you have any 12v loads you'd have to get a converter to feed those.

With such different angles, the better idea would be to have another controller for your morning sun array and just parallel it in. Let the 2 controllers each try to do their job and they'll work best with their own arrays.

I didn't even think about my 12v items. Pump and uv filter.

Probably best to keep 12v it seems. I always had a preconceived notion that 24v was better at using power efficiently but I was wrong.

 

[B-ManFX4]

Forget the cabling - look at the output from your MPPT. The higher the system voltage the more efficient the MPPT is. 12V is stupid if you are trying to run a large inverter AND you are trying to maximize the output from a larger panel array. Look at the power harvesting gains you can realize by increasing your system voltage when using Victron MPPTs as an example:

 

[robbob2112]

I didn't even think about my 12v items. Pump and uv filter.

Probably best to keep 12v it seems. I always had a preconceived notion that 24v was better at using power efficiently but I was wrong.

For your 12v items you use a buck converter to step down to 12v. For being able to catch more power from the sun with a 12/24 SCC 24v is better.

If you have a large 12v draw like an AC would need to look at the current requirements.

 

[Texas-Mark]

If you have a large 12v draw like an AC would need to look at the current requirements.

A lot of people on this forum bag on 12V systems, but a lot of people have no real choice without replacing a lot of equipment. I have two 12V systems and each runs a 3500W low frequency inverter. The one in my trailer runs my 6K BTU AC without issue.

The higher the system voltage the more efficient the MPPT is. 12V is stupid if you are trying to run a large inverter AND you are trying to maximize the output from a larger panel array.

Meh... As noted above, mine work just fine. Am I loosing a few watts? Maybe, but I don't notice it or care. An extra panel or two are cheaper than replacing other things. Of course it depends on what you call "large inverter". There is a limit, but as noted I run that AC for 10 hours a day without any issues.

 

[robbob2112]

A lot of people on this forum bag on 12V systems, but a lot of people have no real choice without replacing a lot of equipment. I have two 12V systems and each runs a 3500W low frequency inverter. The one in my trailer runs my 6K BTU AC without issue.



Meh... As noted above, mine work just fine. Am I loosing a few watts? Maybe, but I don't notice it or care. An extra panel or two are cheaper than replacing other things. Of course it depends on what you call "large inverter". There is a limit, but as noted I run that AC for 10 hours a day without any issues.

For curiosity, how many amps does your 12v ac draw?

 

[Texas-Mark]

For curiosity, how many amps does your 12v ac draw?

32A @ 12V when running. Not sure what the startup is, but the LF inverter does not even blip.

 

[Rednecktek]

Probably best to keep 12v it seems. I always had a preconceived notion that 24v was better at using power efficiently but I was wrong.

Watts in and watts out are going to be pretty much the same nowadays. The biggest advantage is wire size to support an amperage load. If you've already got the fat wires to support your 12v system, they'll be plenty big enough for a 24v system at double the wattage. For starting out from scratch though, copper costs add up quickly.

For your 12v items you use a buck converter to step down to 12v

For converters something to factor in is the complete lack of surge ability. When they say 750w, they mean 750w, NOT 751! Startup surges from any kind of motor have to be accounted for, so you have to get a pretty beefy converter to have enough headroom which gets pricy.

 

[robbob2112]

Watts in and watts out are going to be pretty much the same nowadays. The biggest advantage is wire size to support an amperage load. If you've already got the fat wires to support your 12v system, they'll be plenty big enough for a 24v system at double the wattage. For starting out from scratch though, copper costs add up quickly.


For converters something to factor in is the complete lack of surge ability. When they say 750w, they mean 750w, NOT 751! Startup surges from any kind of motor have to be accounted for, so you have to get a pretty beefy converter to have enough headroom which gets pricy.

Agreed, I was thinking of lights, bathroom fan, tv, etc... not any sort of large load.


with 32a at 12v for the AC it sounds like sticking with 12v is the best bet overall and just have to live with the large currents and wires.

That leaves looking at the SCC and determining what the max load at 12v is. If you want more panels that the current SCC can provide you add an additional one.