Do I need to consider a 24v battery system

[Tony Wright]

I am still working out the details of my off-grid security camera solar powered system and have a question about the need for 24V batteries. I will be using 24v from the panels, an MPPT controller and cameras that run on 5V (they come with an AC/USB adapter) For batteries I am planning use two 6V golf carts in series so will run 12v to the cameras ending with a 12V/5V converter at each camera. I have no need for an inverter.

Each camera uses abut 200mA so voltage drop at 12V shouldn't be a problem. Am I missing a reason to use 24V batteries?

[PNW_Steve]

How many cameras?

any other loads?

[Tony Wright]

Planning on 4 cameras, max total camera power 10W plus internet hotspot etc, say 20W max to allow for extras but don't need AC.

Tony

[PNW_Steve]

Well....

20 watts at 12v you will be drawing 1.66 amps. You would be using 40a/h daily.

I don't see any significant benefit to a 24volt battery in your application.

[SunEagle]

I agree with PNW_Steve. A 12volt battery system would work.

Based on your load of 20w for 24hours a 12v 200ah battery system should be enough. You will need about 20 amps of charging so with an MPPT CC and about 300 watts of panels. Depending on where you are and the amount of useful sunlight you get in the Winter you might need more than 300 watts.

[Tony Wright]

Thanks for the help

Yes, I was aiming for 225 Ah of batteries but perhaps 500 watts of panels because this needs to be a system designed for winter in Canada at 44 deg latitude.

Tony

[PNW_Steve]

Where are you in Canada that is at 44 Degrees latitude? I am 200+ miles from the Canadian border and I am at 46 degrees.

PVwatts tells me that a 300 watt array should produce about 600 watt hours daily in December and January here. Run the numbers for your location and see what it tells you.

Edit: Time for a geography lesson for me..... Looking at a map, you must be in southern ON or QB.

Honest... I got an A in geography 40 years ago....

[Mike90250]

4 cams, 5V 200mA each = 4 watts. That seems awfully low. 1 watt per cam ?? Am I totally blowing something here ?

[Tony Wright]

4 cams, 5V 200mA each = 4 watts. That seems awfully low. 1 watt per cam ?? Am I totally blowing something here ?

Sorry, the 2.5 watts per camera is correct as measured on a Kill-A-Watt. I used 12V instead of 5V to calculate the amps.
There are also spikes when I activate voice, lights or siren but it is very short time.

Tony

[Tony Wright]

Where are you in Canada that is at 44 Degrees latitude? I am 200+ miles from the Canadian border and I am at 46 degrees.

PVwatts tells me that a 300 watt array should produce about 600 watt hours daily in December and January here. Run the numbers for your location and see what it tells you.

Edit: Time for a geography lesson for me..... Looking at a map, you must be in southern ON or QB.

Honest... I got an A in geography 40 years ago....

The system will be at our summer trailer near Orangeville Ontario

I ran the numbers on the PVwatts for a 300 Watt array using an angle to the horizontal off 60 deg. I assumed the array would be at a fixed fairly steep angle for the winter as I don't want to climb on the roof in the snow. I get 613 Wh daily average for December.so my assumed 500 Watt array sounds conservative. However I notice the PVwatts calculator specifically excludes any reduction due to snow so perhaps I will stick with 500 Watts.. I will make that decision in the spring.

Tony