keeping the solar backup power alive - battery change out
I put in Solar electric when I bought this house 26 years ago, so I have a 26 year old solar system. In retrospect, I should have bought nickel iron batteries at that time ( if they were even available, I didnt hear about them back then) But, I didnt. So while my inverter runs great, it was time to get new batteries. My last set were damaged in the fire here 3 years ago, so while they were actually very long lived batteries, one of them, so one third of my storage, died in the power surges in the fire and since they dont make those any more, I wanted more backup power, you cannot combine different battery types in the same battery bank. The partially broken set at this time is only a bit over 4kWh of power, which is ok for some locations, but for this location, I could not keep the internet box, a few lights, and the refrigerator going for more than 2 days, which is not enough. Last January was the first time in my 26 years here that I had to throw away all my refrigerator food.
I ended up getting 3 new batteries as part of my post fire rehabilitation work on my place, finally, and money is still a thing and I am already 62 years old, so, I still do not have a set of nickel iron batteries, but I have a very nice set of lithium iron Phosphate (LiFePo) batteries made here in California that should, barring any natural disasters, be the last batteries I have to buy.
[Skip this paragraph if you dont care about different lithium batteries - First, not all lithium Ion batteries are the same, not at all. The realy common ones used in consumer products and most electric cars have cobalt in them and other chemical differences. Mining cobalt is realy bad, first, for the environment, and also for the peoples health who are "mining" it, with no worker protections. Those other realy common Lithium batteries have problems with thermal runaway conditions and starting realy bad fires. You can imagine that in the fire zone as I am, I dont want any batteries like that in my garage. I would go back to lead acid batteries before I installed a power wall. Realy. ( For other reason besides fire though that I wont get into right now. I know that Tesla and others are switching to some degree away from the lithium cobalts) So, the ones I have use common ores, are safer, but the production is very high tech, not something for a power down world, we need to go back to using very few batteries and for when needed, use nickel iron as high tech production goes away in the future. The other reason I got the brand I bought within the offerings of LiFePo I could find is that some are cheap imports, and I want mine to last. Mine are made in california. I did find a small company I liked, and I do trust their import suplier, but they were optimized for cold locations. My battereis will run in temperatures well over 100'F, and I do not need a built in heater for the winter. So, do your research if you decide to have some battery back up power for our "transition time" . A last reason why I would bother with batteries at this time, is that I already have alot of sunk costs, a system that already exists, so all I needed were batteries. ]
This is my first time changing out the wires in the DC disconnect box myself and not hiring and electrician. The batteries are different enough that they use different wire diameter, and the new ones have built in circuit breakers and didnt need the old fuses. I realy, realy took my time with this. I turned off the entire solar system, thru the bypass breaker fro the house circuits, and left it off for 3 weeks while I slowly unconnected and reconnected. I triple checked that this was so, I confirmed with a voltmeter in a few locations, after waiting a few days after turning it off in case of any stray charge kept by a capacitor or something before I even checked with the voltmeter. But, once it was confirmed completely off, I slowly proceeded.
Here is my system with the old batteries. That photo shows the cover off the disconnect box with all the 48V DC connections for the system.