A little over two and a half years ago, I bought a Monoprice PowerCache 220 (Item #15278) to help store power generated by my cheap Harbor Freight solar array and also to utilize that power by the way of AC inverter and USB power converters. When new, the PowerCache was quite capable of gathering up the day's solar generation and using that energy to charge various battery-powered devices around the house. Up to and including charging an Apple MacBook Air (2014).

I expected this battery to wear down, I just didn't know how quickly. Battery University has a capacity loss chart, but that is for lead acid batteries held on standby for long periods of time (like in an UPS) showing the capacity would fade to about 85% after two and a half years. However, this battery was cycled on a daily basis for most of the past 2+ years. And while the charge controller does perform an occasional top-off charge, it's probably not as much as the battery desires.

As a result of this stressful usage pattern, the battery inside my PowerCache 200 has degraded to a point where it could barely hold enough energy to charge a cell phone. That by itself was not a disaster, as I had anticipated battery degradation and was prepared to revive the machine with a new lead-acid battery. Unfortunately the machine has developed another problem: the thermal protection system has gone amok. Within five minutes of the PowerCache starting up (when everything is still room temperature) the "overheating" warning triangle starts blinking and soon the thermal protection routine kicks in and shuts everything down.

So instead of shopping for a replacement lead-acid battery for the PowerCache 220, I started looking at replacing it entirely. I was pleasantly surprised to see that the cost of lithium based batteries have dropped significantly within the past two and a half years. As of right now, lead-acid based systems are still cheaper, but the price premium for going lithium-ion is now small enough to convince me to make the switch. I'll pay a little extra, but I'll get something that's far smaller and lighter. Thus I bought a Paxcess Rockman 200 Portable Power Station (*) to see how it handles my usage scenarios.

[UPDATE: I opened up the PowerCache 220 with the intent to fix it, but things took an ugly turn and ended up as a full teardown.]

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.