Help with design from the batteries up...

[Curmudgeonman]

I'm a noobie to solar and while this is a very, very small project, I want to do it right the first time and not have to back up and punt too many times.

The load is small but the voltages I need are fairly precise... 12V @ 400ma 12 hours a day, six days a week. 24v @ 1A 30 minutes a day, six days a week. (The 24V load is to power PA speakers and there are forty-eight pages during a 12 hour day. Each page lasts about 15 seconds. The pages are approximately two pages every 30 minutes.)

The speakers require the 24V @ 1A. (Four speakers @ 300ma each.) The page controller requires the 12V @ 400ma and is on 12 hours a day. (During the shorter day seasons the hours per day would drop to 8 hours a day.)

This system has been running for a year using two 12V, 12AH gel cell batteries wired in series. (We're using these batteries because they were available/donated.) The 12V equipment is connected to one battery and the 24V equipment is connected to the series config. The equipment will operate at least two to three days before having to charge the batteries.

I want to see what it will take to get a solar setup to power this and not have to be charging the batteries the hard way.

I have a lot of questions such as...
Is it ok to wire the two different voltage sources as it is now or would a charging controller have the 12V and 24V connections to power the equipment.
What type battery config and type is best? Two 12V batteries, one 24V, etc...or other config.

Note: this equipment is out of the weather but will be operating at the outside temperatures. It's in TN so the summers can be warm to hot and the winters mild to 30s and sometimes to zero.

The other forum said to start with the correct battery setup first so I'd welcome any and all help.
Thanks!

[Naptown]

Considering the loads it probably would not hurt the batteries much with the unbalanced load.
Your issue is going to be finding a 24V panel in a small enough size for your existing batteries.
Your total load is just under 70 Watt hours a day. Using 3 sun hours a day for the winter and a PWM controller you would need
70 WH x 2 / 3 = 47W solar panel round up to 50.
You should be using higher amp hour batteries as the charge rate will be about 2 amps or about C/6 where C= battery amp hours.
This may be a bit high for those batteries.

[Curmudgeonman]

Thank you Naptown!

I'm not wanting to use the batteries I have at this time. I just listed what the existing setup is and the loads.

I'll buy whatever battery size you'd care to recommend, panel(s), controller, etc.

I want to do it right the first time and not end up buying again and again learning the hard way.

Please feel free to recommend/list whatever will get this working the best.

Thank you again!

[Naptown]

To do this right
Get 2 50Ah 12V batteries and wire them in series for 24 V assuming flooded batteries. If you go AGM you could reduce these to A smaller size.
Get a small power converter to reduce the 24V to 12V for the controller.
One 72 cell 60W panel will do for the solar panel
Finally a 5A charge controller to finish the equipment list.
You will need some more parts like wiring etc but not knowing distances etc cannot advise at this time

[Curmudgeonman]

Naptown, Thank you sir! I've been looking over the information you provided for the small system.

I naturally have more questions...

The batteries will be in a protected location but subject to ambient air temps. The winter temp in TN can vary to zero for a short while some years. Is one battery desired over another in cold temps?

24V to 12V power converter...I assume that's the same as I call a DC to DC converter...?

72 cell 24V panels seem harder to find. I read that solarpaneltalk.com opted for advertising ads via google advertising because direct supporters were few. I wish that was not the case. I frequent other boards that have sponsors and I try to support them. I'm looking at the ads here from google but if anyone wants to name drop, I will give them my attention.

Distance...everything will be in a 10 to 15 foot location from panel on the shed roof to the equipment below.

Thanks again!!

[Curmudgeonman]

My bad...I do see sponsors listed...

Sunnovations
SolarTown
Centrosolar America

I'll check these first for what I'm looking for!

[russ]

My bad...I do see sponsors listed...

Sunnovations
SolarTown
Centrosolar America

I'll check these first for what I'm looking for!

Thank you!

[marmelada]

Hey Curmudgeonman
DId you get your answers yet?

[Wy_White_Wolf]

Naptown, Thank you sir! I've been looking over the information you provided for the small system.

I naturally have more questions...

The batteries will be in a protected location but subject to ambient air temps. The winter temp in TN can vary to zero for a short while some years. Is one battery desired over another in cold temps?

24V to 12V power converter...I assume that's the same as I call a DC to DC converter...?

72 cell 24V panels seem harder to find. I read that solarpaneltalk.com opted for advertising ads via google advertising because direct supporters were few. I wish that was not the case. I frequent other boards that have sponsors and I try to support them. I'm looking at the ads here from google but if anyone wants to name drop, I will give them my attention.

Distance...everything will be in a 10 to 15 foot location from panel on the shed roof to the equipment below.

Thanks again!!

Zero isn't cold enough to worry about on the batteries. When you start hitting 20 to 30 below zero then start worrying.

AYess that is a DC to DC convertor. One of the problems with the current system is the 12v loads are hooked to only one of the batteries. That's unbalancing then and hard on batteries. The DC to DC convertor will keep the balance.

Yes smaller 24v panels are harder to find. You can wire 2 - 12v panels in series to get the 24v needed.

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