May 20, 2022

Upgrading Our Solar Set-Up

One of the things I've regretted about our solar set-up is not spending more on batteries. It made sense at the time, because we were looking to stretch our limited budget as far as we could. However, our battery bank isn't large enough to power the freezer and fridge for more than a day and a half without sun. Fortunately, we usually have the grid to plug back into, but the primary reason for this small system is to preserve food in our hot climate if the power is out for an extended period of time. 
In the back of my mind, I've thought that if we were ever able to utilize our remaining two solar panels, we could use the original battery bank for those and invest in a larger one for the fridge/freezer set-up. Now that we finally have those panels up, that's what we decided to do.
Ordering batteries off the internet is the most expensive option, so we went back to the same folks who sold us our first set of batteries. Originally, we got 6-volt golf cart batteries. With the help of the sales guy, we were able get industrial 6-volt floor scrubber/sweeper batteries.

 Our six golf cart batteries are 235 amp hours each, with a total of 705 amp hours for the battery bank. These floor scrubber batteries are 330 amp hours each, so we can increase our electricity storage quite a bit. Of course, more amp hours meant they are more expensive, and it took some discussion to decide on how many. Pairs are required for solar wiring, and six would give us approximately 990 amp hours. But eight would give us 1320 amp hours!

 For technophiles, here's how that works:

Wiring components in series increases voltage.
Wiring components in parallel increases amperage.
Our system is small, so 12 volts is perfect. To create a 12-volt system from 6-volt batteries, we connect pairs of batteries in series (connecting negative terminals to positive). That increases voltage.

6 volts + 6 volts = 12 volts 

To increase amperage, we connect the pairs in parallel (connecting all the negative terminals together, and all the positive terminals together). That increases amperage.
330 amp hours x 4 pairs = 1320 amp hours
The result is a 12-volt, 1320 AH battery bank.
For a visual example of how the wiring is done, here is our original battery bank. The blue is series wiring (neg to pos). The green is parallel wiring (neg to neg and pos to pos).
Diagram from Solar Pantry Project: Batteries

Anyway, even though the money had been earmarked for this purpose, it's still difficult to make expensive purchases because we do it so rarely. Finally, Dan asked what would give me the most peace of mind, so we got eight!

Batteries do have a lifespan, which was something to consider when making this switch. We've taken good care of our first battery bank by regularly checking the specific gravity and water level of each cell, plus not discharging too deeply. So we should still get quite a few years out of the old bank.

Now that we have the batteries, the next step is to build a box to house them. Dan's working on that.


Ed said...

I too struggle with large purchases but rarely regret them.

Leigh said...

Ed, we find it to be the same, I think because such purchases are carefully thought out. It's those impulse buys that are the problem!

Boud said...

I think there's a lot of risk in an expensive purchase, where you can't afford an expensive mistake. It's enough to give you pause. That said, I've never regretted the "buy the best" the times I've done it. So there's that.
Also thank you for the lesson in battery use and pairing. Always learn something here.

tpals said...

My batteries are dying. I can only run off the solar panels when the sun is hitting them. It helped after our recent storm to run the fridge and freezers during the day, but I really wish I could afford to replace them.

Leigh said...

Boud, I've always said that the blessing of being poor is that I can't afford to make mistakes! I agree with "buy the best" or in this case, buy the biggest.

Tpals, I'm sorry to hear that and fear we'll be in the same boat some day. And the price of batteries is (of course) going up. It's worrisome.

daisy g said...

I don't understand the math, but it sounds like a great upgrade! ;0D
Let the sun shine in!

Leigh said...

Daisy, the math is electricity stuff, which I confess stumped me profoundly for the longest time. It's difficult to understand (and remember!) definitions for things that can't be seen, such as voltage, current, and power. One of the reasons I put it in my blog posts is for a record and a reminder!

wyomingheart said...

Wow! That is such a great purchase, and you are correct! Peace of mind, INDEED! Great post, Leigh!

Leigh said...

Thanks, Wyomingheart!

Toirdhealbheach Beucail said...

Leigh, from an inexperienced opinion, I think going with eight makes the most sense if for nothing else, the piece of mind. As Ed said, in larger purchases such as this or ones that will essentially be long term purchases, I have rarely regretted spending the extra money.

Cederq said...

Off topic Leigh, I sent a pic to you and didn't know if you received it. I took your email off of your profile and it had a weird prefix ******@, was that the right email? You may have my email address when I comment if you would prefer a little privacy.