Batterybank sizing

[asdex]

Hi, I'm looking at getting new batteries. The batteries I have are actually UPS batteries and not suppose to be for cycling.
I was up at the cabin this weekend and measured the fridge and freezer kWA over 24 hours which were a total of 0.7kWH.
The rest of our thinks I have calculated to be 0.5kWH per 24hrs. I followed though a calculation and got a battery bank size of 375AH. The links to the caculator excel file didn't seem to work.
Does this AH figure seem realistic? The bank is 24 volts and I have allowed 2.5 days reserve.
Thanks

[Mike90250]

For both fridge & freezer to be lower than 1.5Kwh, seems unrealistic. sorry, either it was very cool there, or some other factor was in play. The good energy star fridges are about 1Kwh /day you get into exotic insulation, or special compressors, below .7Kwh each seems difficult.

[asdex]

Thanks for your reply. There are the specs from the fridge and freezer information and my watt meter showed pretty much the same over a 24hour period.

Fridge 231 kWhrs/year@32deg C (0.63kWh/day@32degC)
Freezer 255 kWhrs/year@32degC (0.7kWh/day@32degC)


The temperature was about 16deg C and 32deg C wouldn't be that common here.
Cheers,

[Mike90250]

.... measured the fridge and freezer kWA over 24 hours which were a total of 0.7kWH......

and

Fridge 231 kWhrs/year@32deg C (0.63kWh/day@32degC)
Freezer 255 kWhrs/year@32degC (0.7kWh/day@32degC)

indicates that it was actually 1.33Kwh total - which I find amazing. But still, they are the numbers you measured and want to build your system around.

The rest of our thinks I have calculated to be 0.5kWH per 24hrs.

OK, let's call it 2Kwh daily load. x 5 days, that's 10 Kwh of storage you need, and start the generator on 3rd day - as batteries go below the 50% point
My watt hour spread sheet says you need 8, 6v-200ah golf cart batteries to attain just under 10Kwh of storage


Battery Cost b.jpg

[asdex]

Hi, thanks for the calculation
I would like to avoid parallel connections and I guess your spreadsheet shows two strings of four batteries in parallel to give 24 volts and 400ah.
Therefore the four 6volt 430ah batteries I am looking at should be about right?
I also have a 400w wind generator for windy times of which there are many but won't include that in any calculations.
I hope to not run my generator at any stage as its 6kva and uses alot of petrol. I don't know how long it would take to charge up the batteries.
I have a 15amp battery charger but I think I can also connect a generator though my Outback inverter. Not sure if it acts like a battery charger. Will need to read the instructions.
Cheers,

[Mike90250]

Going with 48V will be the simplest thing, unless you are locked into 24v with existing 24v gear. if so, then parallel banks are your only option, or your 6v 430ah batteries. But the gel batteries will not last very long under Cycle usage, but this is a pretty light cycle, so they may surprise us.

[asdex]

Locked into 24v really with my inverter. Yes I'm thinking seriously about the 430ah batteries while I can afford them and sellingvall my old batteries for scrap means I get one free.
Just need to sort out the charging issue now.

[Logan5]

allowing yourself to be locked into a particular voltage because of your inverter is a fools game. To keep from paralleling batteries you could consider 6X 4 volt golf cart batteries to maintain a 24v system.

[Wy_White_Wolf]

Aren't most L-16s in the 370 to 420aH range? Seems they would be your best choice.

WWW

[Sunking]

Dave at 2 Kwh/day means you need a 10 Kwh battery.At:

12 volts @ 800 AH
24 volts @ 400 AH
48 volts @ 200 AH
A 10 Kwh battery requires a 800 to 1200 watt Solar Panel with MPPT Controller. So at a minimum 24 volt system. Leave the 12 volts for children and their toys. WWW is spot on a perfect job for 6-Volt LR16 cells. I would recommend either Trojan L16P, L16H, L16RE-B, or if cash is tight one of the US Battery L-16's of appropriate capacity. In AZ you should be able to get away with 800 watt panel and with a MPPT controller @ 24 volts is 30 amp controller. DO NOT USE 12 VOLTS.

[asdex]

I guess eventually something locks you in to a specific voltage. I could spend $2000 and change inverters but I like to have a split in case my inverter fails. I have lights and radio on 24 volts plus a spare 24volt pump. I can also easily pick up a new 24volt inverter in an emergency most places as opposed to a 48 volt one which I would have to send away for.

[asdex]

Dave at 2 Kwh/day means you need a 10 Kwh battery.At:

12 volts @ 800 AH
24 volts @ 400 AH
48 volts @ 200 AH
A 10 Kwh battery requires a 800 to 1200 watt Solar Panel with MPPT Controller. So at a minimum 24 volt system. Leave the 12 volts for children and their toys. WWW is spot on a perfect job for 6-Volt LR16 cells. I would recommend either Trojan L16P, L16H, L16RE-B, or if cash is tight one of the US Battery L-16's of appropriate capacity. In AZ you should be able to get away with 800 watt panel and with a MPPT controller @ 24 volts is 30 amp controller. DO NOT USE 12 VOLTS.

This fits my existing system pretty well as I have 1920watts of panels and a Midnite Classic 150. I'll look at the US Battery L-16 but the Trojan are nearly double the price of the Crown I'm looking at.

[Sunking]

No problem with the Crown batteries. Which Trojan L16 are you looking at? There are 5 models.

[asdex]

These are $760 each incl freight:- Trojan L16H -AC 6V 435Ah/20Hrs the Crown CR-430 are $400 incl freight.

[asdex]

Dave at 2 Kwh/day means you need a 10 Kwh battery.At:
. I would recommend either Trojan L16P, L16H, L16RE-B, or if cash is tight one of the US Battery L-16's of appropriate capacity.

The US Batteries here are called Hella Cyclemaster and the L16 420a/h 6v are about $1100 each!.
I'll go for the Crowns I think.

[John Galt 1]

The local solar installer turned me onto Crown batteries. He installed Rolls for years but found that it was very difficult to file a warranty claim so he switched to installing Crowns with no problems the last 3 years.

So I ordered 16 Crown 6CRP525 (L-16 6v 395 amp hr) and installed them 14 months ago. The only problem I've noticed is that they don't fully charge in a reasonable absorb time when using the recommended 58.1 absorb voltage. After much trial and error with my SG meter and 2 calls to Crown tech support I'm currently using 59.1v absorb voltage to get them up to about 95% SOC after a 4 hr absorb.

Thus far I'm happy with my Crown batteries, We'll see if I'm still happy in 7 years but I suspect I will be.