I been using lifepo4 almost 2 years, once you go lithium you never go back to lead acid. Safety isnt an issue as long as you don't punctured them. A lifepo4 fire will be as violent as li-ion, I seen it firsthand. But the chance of that happening are about the same as a lead acid exploding, it can happen but its rare. You can improve your safety by use of overvoltage relays/alarms etc.
If you going to use a drop-in replacement and solar, you will need some sort of overvoltage relay, the battery has a BMS which monitors voltage/balancing if it reaches the limits it triggers the BMS to stop accepting current, this doesnt stop the controller from reading the battery. The controller will try to force voltage into the battery creating voltage surges, these surges will destroy anything connected to the battery. I encounter this many times is why I use an overvoltage relay. Lifepo4 and solar, this is my setup. Notice how the relay disconnect the solar panel from controller. You don't want to disconnect battery from controller, that will cause controller to act weird. The overvoltage relay is about 5 dollars, the 30 amp automotive relay is about 4 dollars.
You also will need a coulomb meter, lifepo4 will read 13.1 volts almost the entire time. A coulomb meter counts amps going in/out battery. I use the tk15 (about 25 dollars for 50 amp model), you need something silmilar otherwise you will never know what the battery status is.
Picture of lifepo4 cell that caught on fire, this is a 26650 cell 3.2 volts, drop-in replacement batteries have about 80 of these (or more) in a 4s configuration. I'm not scaring anyone or spreading disinformation, but just pointing out worst case scenario, they do go up in flames like a blow torch. I was removing cell and shorted it out which punctured a hole in it. It didnt just catch on fire by itself. I got 200 of these and I will be using them, they are too powerful not to put them to use. Before like everyone else I thought lifepo4 was safer then li-ion, but lithium is lithium. I treat these same as li-ion. I never had a fire with li-ion and they are more dangerous then lifepo4.
