need guidence

System

I am very happy to be on this site . very informative and good people.
I have just up graded my system with 2 more panels, and a new magna sine inverter charger. and also 8 more 370 amh 6 volt batteries. heres the problem the inverter charger is 24 volt. my existing system is 12 volt. do I go up and change the panels to 24 volt? or continue to wire the new ones at 12 volt ?and buy a new 24 volt inverter and also a new charge controller,as the one I have is only 25 amp.I have total 620 watts of power in my panels and 8 ,370 amph If I leave it 12 ,would that be to much batteries ,for the panels to charge ? if I go to 24 volt do I loose amh? I am not sure what to do. I must clarify that this new system was a friends, who went to hydo and gave me the new stuff. there is also a morning star 30 charge controller in the box upon further inspection.also what does it mean that I must have 5% to 10% of the total amph in panels to fully charge my batteries? I hope this makes sense to somebody .so I can resolve my problems.

mike95490

Re: need guidence

nocita1 wrote: »

I hope this makes sense to somebody .so I can resolve my problems.

What are the problems you are having ? or just questions?

I prefer to use the higher voltages, so I'd opt for 24V battery bank, and to charge it, you need to wire panels to produce at least 30V @ max power. This is where MPPT charge controllers can help out.

System2

Re: need guidence

mike90045 wrote: »

What are the problems you are having ? or just questions?

I prefer to use the higher voltages, so I'd opt for 24V battery bank, and to charge it, you need to wire panels to produce at least 30V @ max power. This is where MPPT charge controllers can help out.

these are just questions. already have 360 watts at 12 volt. just recived this other package of magna sine inverter charger and 2 more panels kc 130 and also 8, 370 amp/h batteries I want to know if 24 volt is better? and if so why?if I change to 24 v I won't have to buy a 24 volt inverter and new charge controller .but not sure how to do it.

Thanks

BB.

Re: need guidence

If I understand your questions correctly...

First, Watts (power) is P=V*I... So, if you have a pair of 12 volt x 100 Amp*Hour batteries:

two batteries in parallel=> 200 Amp*Hour @ 12 volts
two batteries in series=> 100 Amp*Hour @ 24 volts

So--related to power, both setups have exactly the same amount of power:

200AH*12v=2,400 Watt*Hours of storage
100AH*24v=2,400 Watt*Hours of storage

The reasons to choose 12 volt or 24 volt (or 48 volt) battery bank:

1. Choose 12 volt for lower power systems (less than ~1,000 watts), short wiring runs, and/or if you need 12 VDC for your loads. 12 volt appliances/devices are usually less expensive vs 24 volt units.
2. Choose higher voltage battery bank if you need more power (~2,400 watt max for 24 volt system) to keep the maximum current to 100 amps or so (P=24 volts*100 amps=2,400 watts). Also use higher voltage bank if you have to send the DC voltage/current longer distances (lower current allows you to use smaller wires--plus your 24 volt devices will typically allow larger voltage drops to load... 12-10.5 volts is 1.5 volt drop on 12 volt systems. 24 volt system down to 21 volts supports 3.5 volt drop).

For larger TSW inverters--there is usually not much of a price difference for units that run at higher voltages.

For Charge Controllers--typically they are rated at maximum output current... So a 60 amp controller will support P=60A*15V=900 watts for a 12 volt bank, but at 24V P=60A*30V=1,800 watts; and a 48 volt would be 3,600 watts of solar panels (so charge controllers are much cheaper "per watt" with higher voltage battery banks.

If you have a 12 volt system and keep going larger (more watts/current)--you probably will end up some day going to a 24 or 48 vdc system (and need new controller$/inverter$/etc.).

There is no right or wrong answer--you need to work out your power needs and see what makes the most sense for you.

-Bill

hillbilly

Re: need guidence

Bill painted it out pretty clearly I think. I'll just comment that you need to consider what your wires can handle, both ampacity, but also voltage drop. You might be able to use the same wires that you have for your 12V system, and run more "watts" through them if you up the voltage to "24V" (nominal), and thus keep the amps lower. I don't know what you've had for wires, but you can use the sticky here to check out Voltage drop and get an idea if you need to add more wires or not. Did you say that you have a 24v inverter/charger already (sorry this part was hard to understand)? If so, it will only work on a 24V battery bank so your decision is either change voltage or change inverters to a 12V. In adding all that stuff, it seems to me that most likely upping your system voltage to 24V makes sense (especially if you have a 24V inverter).
Did we miss something, or was this what you were wanting to know?

BB.

Re: need guidence

This is the Excel based voltage drop calculator that Hillbilly was referring too.

Another issue to think about--the whole question of the cheap MSW (Modified Square/Sine Wave) vs the TSW (True Sine Wave) Inverters.

For a small system--most people purchase the MSW inverters because they work OK on 80-90% of the AC appliances out there...

However, as the systems become larger and you start putting more "sensitive loads" on your AC power (refrigerators, battery chargers for power tools, TVs, Radios, cell phone chargers, computers, etc.)--then you probably will need to look at using TSW inverters (which are not cheap at all.

You can read about the MSW/TSW inverter issues here:

All About Inverters
Choosing an inverter for water pumping

There is no one right or wrong answer--but, unfortunately, spending more $$$ usually gets you closer to your "perfect" system.

-Bill

ehorn

Re: need guidence

nocita1 wrote: »

...also what does it mean that I must have 5% to 10% of the total amph in panels to fully charge my batteries? ...

FLA (Flooded Lead Acid) batteries require Boost or equalization charging. This involves short periodic overcharging, which releases gas and mixes the electrolyte, thus preventing stratification of the electrolyte in the battery. In addition, boost charging also assists in keeping all batteries at the same capacity. For example, if one battery develops a higher internal series resistance than other batteries, then the lower SR battery will consistently be undercharged during a normal charging regime due to the voltage drop across the series resistance. However, if the batteries are charged at a higher voltage (the idea behind the panel % factor), then this allows all batteries to become fully charged and equalized.

Best wishes

n3qik

Re: need guidence

nocita1 wrote: »

just recived this other package of magna sine inverter charger

The real answer is what the voltage of the magna inverter is. If it is 12V, then you are stuck at 12V unless you want to by another inverter.

Could you list the Mod. # of the charge controller and inverter???