Question about battery bank

barenakedfan

Hello all,

I have 5 Kyocera 140W 12V panels.  I will be running these at 12V to the batteries which will be wired to maintain 12 V.

I am placing them on a building that has no power requirements for now.  I plan to use the power I generate with my system then add more as I am able.  For now, I only plan to put 3 light fixtures in the buildings.

I understand that you do not want to run your batteries down to less than 50% and also have a 3 day reserve.

So, my question is this.  How can I determine what the number of batteries to the panels ratio is?  I do not want to put in more AH than the system a can maintain but also want to get the most out of them.  I do have a charge controller already.

I hope this is enough information.

Thanks for any help.

barenakedfan

Sorry, I hit the wrong key.  I have 6 140W 12V panels.

vtmaps

Welcome to the forum,

Usually we design a system starting with the loads.  Then we choose a battery that can handle those loads.  Finally we figure out how large a solar array is needed to keep the battery happy.

It looks like you want to design around a solar array.  That's possible.  I don't have the specs for your particular panels, but I would guess they could put out 48 amps into a PWM  controller, but less than that under typical conditions.   I don't know much about your climate or latitude, so I don't know how many sunhours per day you get.   Your battery will probably be 300-400 amphours at 12 volts. 

You didn't mention what you have for a charge controller, but I am assuming it is a PWM type because you are running your panels at 12 volts.  Depending on your climate, you might harvest more power (and support a larger battery) if you reconfigure your panels and get a MPPT controller.

--vtMaps

barenakedfan

My panels are the Kyocera 140W that I purchased from Arizona Wind and Sun.  My charge controller is an off brand but will support the panels, I verified that prior to purchase. As far as the load, there is only going to be a few lights for now.  Yes, I am going to design my needs around my array.  I found that if i attempt to run my house around my current usage, it would be cost prohibitive to put in a system so I am making the change with what I will have available.  The building is in zip code 31801, Box Springs, GA

I will be using AGM Batteries.  For now, I have 3 125Ah AGM's but will be adding to them.  I just don't want to purchase more than I can use.  I can add panels one a month and a battery the following.   I will go with the same panels because it is what I can afford and have shipped via UPS one at a time.

vtmaps

barenakedfan said:

I will be using AGM Batteries.  For now, I have 3 125Ah AGM's but will be adding to them.  I just don't want to purchase more than I can use.  I can add panels one a month and a battery the following.   I will go with the same panels because it is what I can afford and have shipped via UPS one at a time.

Nothing wrong with planning ahead... but where is this going?  Adding batteries doesn't sound like a good plan.  Actually, you have already mis-spent money on batteries.  Three parallel batteries is NOT an optimal design, especially when they are AGM batteries.   More than 3 parallel batteries is even worse than 3 parallel batteries.   You should have fuses or breakers on each battery, and the batteries should be wired with a bus bar.

With some planning it is possible to grow a system... but the first step is to design the finished system, and the second step is to figure out how to build it in stages.   Please tell us what you ultimately want from the system.    

--vtMaps