By Joe Gresh
I finally made the leap. My solar system went online in 2018 and except for a few snow days has produced reliable power in all that time. We’ve had around 30 power outages at the grid-tied Carriage House (some 5 minutes, some 5 hours) during the same time span.
Initially we went with plain old lead-acid batteries because they were a third the cost of lithium batteries. The lead-acids worked well and since they’ve been around hundreds of years it was easy to predict performance and longevity.
The battery bank started small with just 4 batteries and grew with our budget to 12 total. There are two of the original 2018 batteries still functioning and I’ve replaced three batteries that failed. It’s easy to tell a bad lead-acid in a battery bank: it’s the hot one.
I haven’t been religious about topping up the electrolyte so some of the batteries might have failed due to misuse. Regardless, I’m happy with their performance and the lead-acids did me right.
Last year I noticed lithium batteries dropping in price. They ended up costing the same as the cheap Walmart lead-acids I was using. With new tariffs looming I decided to make the switch. I bought one batch in January and another batch in March, depending on whatever sale was on. My cost averaged around $119 per 12-volt, 100-ah battery. I wasn’t brand loyal, whatever was cheapest was fine by me.
With winter approaching and long cold nights of pipe heaters draining storage I built an insulated box to hold the new batteries. Advantages with the lithium are 16 batteries fit on one shelf, weight is half of lead acid, and there’s no need for a sealed battery box as there’s no acid to leak.
I also took the opportunity to clean up the installation, getting rid of messy-looking jumper cables and replacing them with solid copper buss bars. With everything on one shelf I eliminated several feet of cabling which can only be good.
Lithium batteries need a bit more charging voltage so I cranked up the solar regulator a 1/2 volt or so. I also reset the inverter charger setting to one more like lithium.
The batteries have sat on the shed floor for 6-8 months so when I connected them up to the solar they sucked a steady diet of 55 amps from the sun.
Theoretically I have 19,000 watts of storage now, more than double the 7200 watts of the old, lead-acid battery bank. In actuality it’s probably 80% of 19,000 watts because you don’t want to drain the batteries flat.
Some disadvantages to lithium batteries are they are more affected by cold temperatures (hence the insulated battery box), they are limited to 100-amp output per battery (not a problem as my inverter draws 250-amp max), and I can’t really think of any others.
Time will tell if the lithium batteries last the 10-year claimed life span. I’ve pre-tested each battery’s load capacity and marked the results on top of the battery. I should be able to compare results in the future to see if individual battery performance degrades. All in, I’m happy with the new batteries. Hopefully I’ll have about a 3-day reserve for those snow days.
Oh, and those tariffs? They don’t seem to apply to lithium batteries as you can still get 12-v, 100-ah lithiums for $119 on Amazon.
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What do you power with the batteries, the whole house or just certain things?
It powers a 6000-watt inverter that powered the shed.
I don’t understand your wiring. Perhaps it is just that I have never done multi battery systems.
What don’t you understand?