Batteries are heavy. Even lightweight batteries, if you have enough of them.
One of the best battery upgrades I ever did was adding a pair of Exide tubular forklift batteries. The problem is, they weigh a little over a ton each. I couldn’t even pick them up with my small tractor so I had to move them on sleds and then work them into place with jacks and levers. I could not even bring them indoors, so they sit outside on a plastic shipping pallet. It isn’t ideal, but it works. Racking systems that use the individual 2v cells are perhaps a better way to go, but I got a deal. Hard to pass up a deal, right? Oh, and outdoors is not a terrible idea for batteries that need ventilation. When I water them, it usually takes about 6 gallons of distilled water. That means that they made a LOT of highly explosive hydrogen which went harmlessly into the breeze.
Lately, my banks of telecom batteries have been in decline. (If you lose a cell in a battery, that bank is going to drag down the others, so it is best to check them individually from time to time.) They are pretty heavy, too. They are about 50 feet back in the Solar Shed, behind the wall of the control room. That keeps cables short, but moving them is an issue. These batteries were sitting on 2×4 strips on a dirt floor, so support wasn’t a problem. You need to keep lead batteries off of the ground or concrete to avoid temperature stratification and the 2x4s were an easy solution. However, 3 of the big 16volt batteries had to go and it took 2 people to get one tipped enough to get the hand truck under it. Yeesh, I was a younger man when they went in there!
The latest upgrade was with the Lithium Iron Phosphate (LFP or LiFePO4) batteries I mentioned in the last post. To put them in the battery room, if you want to call it that, it would be best to get all the lead batteries out and build a floor and an enclosure to moderate the temperature and humidity.
Well first, a lot of the lead batteries are still good, so I didn’t want to mess with success. Second, the new LFP systems are a considerable investment, and the accompanying electronics are a bit more delicate than a lead battery. The best idea was to bring them into the control room.
It is crowded in there with some estate stuff in storage and the cabinets are tall enough that they would block some of the control panel. It finally dawned on me that they would fit behind the chair and sofa on the wall next to the battery room. There are heat and a/c in there, so low humidity and moderate temperatures made this the ideal solution. There was one more detail. Weight.
Each of the LFP cabinets packs twice the usable power of a bank of 3 of those 16v batteries, but weighs only a little more than one of the lead batteries. Still, the LFP is over 300 lbs. and there are 5 of them. The control room/Man Cave has a wooden floor. Did I really want to put 1600 lbs. of weight on a relatively small area?
Batteries behind the sofa offer the added benefit of freeing up some bookshelf space!
I built the floor myself, so I knew what was under there. I did not do an analysis like we did in Statics 101, but I built it to be pretty robust. The idea was not that I was going to put 1600 pounds on it, I just don’t like a bouncy floor! In the end, it worked out.
The point I am trying to make is that you need to think about battery weight and climate when planning your system. Batteries are getting lighter, but they tend to get accumulate over time. A concrete slab or a pallet on dirt are no problem. Off grade requires a little care. My first battery bank was 8 golf car batteries in my attic. It was right next to a load bearing wall, so it was never a structural problem.
Next time, I want to talk about battery cabling. The LFP maker gave specific instructions on that, and we’ll look into why…and a better way.
Oh, by the way, the additional 80 kilowatt-hours now let me do most of my heating with the heat pump instead of the wood furnace! I love it.
—Neal