SLA batteries: More system form factors and lithium-based successors

The upgraded SLA (sealed lead acid) battery-based UPS (uninterruptable power supply) now residing in my furnace room has done a great job so far feeding backup power to my two NASs and my key broadband and LAN gear. But what about other, beefier devices in my residence that I also might want to keep running if premises power goes down especially for a lengthy timespan, such as my chest freezer out in the garage? And what about toting a beefy power source along with me on road trips in my camper van, for use in situations where I decide to spend substantial time somewhere far away from conventional sources of electricity?

A couple of months ago, I found my answer, at least for now: the Phase2 Energy PowerSource 660Wh 1800-Watt Power Station, which I picked up on sale for $149.99 plus tax at Meh:

The sold-new model number is P2E660PSS, and here are some specs courtesy of Meh’s forum:

• Provides 1800 watts of peak output power (1440 watts continuous) to run most household appliances
• Features an instant-on UPS for uninterrupted power
• Allows daisy-chaining of unlimited additional batteries for extended device run times
• Includes a built-in solar controller with Anderson connector for connecting solar panels
• Equipped with an LCD power display for quick power and output status
• Designed with built-in handles for easy transport
• 660 Wh battery capacity (12V, 55Ah)
• Outputs: Four AC, dual USB, one 12V DC (“cigarette lighter adapter”)
• Dimensions: 19.9″L x 12.8″W x 8.9″H
• Power source: ‎Solar powered, Battery Powered

Turns out it’s a clone of the Duracell PowerSource 660 1800 Peak Watt Gasless Generator and Portable Power Station, model DR660PSS, which (believe it or not) originally sold for $699.99:

(The “gasless” terminology you sometimes see associated with these units doesn’t reference an absence of gas emissions; instead, it refers to the fact that unlike legacy AC generators, these aren’t powered by natural gas, propane, diesel and and/or standard gasoline fuel sources.)

So why the substantial discount to $149.99? For one thing, Phase2 Energy seemingly no longer exists, considering the company’s DOA website. Duracell doesn’t sell its version of the product any more, either. If I had to guess, based on my research, I’d wager that both are private label retail versions of a design commonly sourced originally from Battery-Biz, but I digress…

Some of the reason for the price reduction may come from bulk coupled with the cost of replacement batteries. One key spec missing from the above bullet list is the P2E660PSS’s weight: 58.33 lbs. Granted, there are “built-in handles”, but unless you’re a weightlifter, “easy transport” is still a stretch. And as this review notes, “the OEM battery, which is Chinese, is very hard to find, and if you can it is really expensive.”

Some of the reason may come from the mixed feedback. Granted, the customer reviews on Best Buy’s and Amazon’s websites were nearly all four- and five-star in nature. But online reviews from knowledgeable enthusiasts, such as this one, were less sanguine:

That said, the reviewer admits that the product is still a good value for what it costs, even at its original $699.99 price tag. And admittedly, his website is titled “Powered Portable Solar,” so he proportionally focused more on the product’s inefficient PWM charge controller circuitry than someone not interested in solar recharging might (he also “dinged” it for its modified sine wave inverter, which is both less output-efficient than the more expensive pure sine wave inverter alternative and whose output may cause problems with particularly picky AC devices). I plan to discuss solar charging both in general and specifically as it relates to my particular device in a planned upcoming follow-on blog post.

That all said, the likely largest reason for the discount-and-demise is that this entire SLA battery-based product category is in the process of being obsoleted by lithium battery-based portable power successors such as those from longstanding companies such as Anker, Bluetti, EcoFlow, and Jackery, plus an increasing number of China-based low-priced competitors. Recent Meh sale examples include this 500W one from Phase2 Energy (who I gather is apparently dumping its remaining closeout product inventory) for $149 refurbished or $199 new:

or this 1200W Energizer-branded one, complete with a separate 200W solar cell, for $599.99:

Why? SLA batteries are bulky, heavy, and have a limited shelf life (something I recently experienced firsthand) along with limited recharge cycle counts ahead of their inevitable demise. On the latter point, the Powered Portable Solar review highlights the 250-cycle lifetime spec for Duracell’s PowerSource 660, which may signify an improvement vs the SLA norm. The product’s internal battery is variously reported as being an AGM (absorbed glass mat) variant (I haven’t taken my device apart yet to confirm), which if true would deliver improvements in metrics such as deep cycle tolerance, charging speeds, recharge cycles, temperature and vibration tolerance, etc. versus conventional SLAs, albeit at an incremental-price tradeoff.

Successor devices are generally based on LiFePO₄ (lithium iron phosphate) battery technology. How’s this translate in terms of comparative product specifications? Take, for example, the Bluetti AC18O, which I randomly selected from a Google search results list based on its similar-sounding 1800-W AC output (although note that for the Duracell and Phase2 Energy devices, this is the peak spec with 1440 W as the continuous-output counterpart, whereas the Bluetti AC180 specs 1800 W continuous and 2700 W peak):

The Bluetti 180’s weight—35.3 lbs—is nearly half that of its SLA precursors, although it’s a tad bit larger volume-wise: 13.39” x 9.72” x 12.48” (some of which, in fairness, is taken up by its higher 11-total output count; four pure sine wave AC, one USB-C, four USB-A, one 12V DC, and an integrated wireless charging pad). The internal battery capacity is 1,152 Wh. It touts 3,500+ recharge cycles to 80% original capacity, recharges to 80% in 45 minutes with a 1,440-W AC input, and offers a 5-year warranty (versus 2 years on the Duracell, and Phase2 Energy’s no longer around, of course …ironically, I’d discovered the company’s DOA website when I went online to register it for extended warranty coverage purposes).

So, what are the tradeoffs? Upfront cost is one big one. The Bluetti 180 is currently selling (as I type these words on July 14) for $999 on the manufacturer’s website, although Amazon currently has it listed for $450 less ($549) as a pre-Prime Days promotion. A lot of that price differential comes from the cost variance between relatively the new LiFePO₄ and mature SLA battery technologies. That said, of course, a LiFePO₄-based power station will last quite a bit longer than its legacy SLA-based precursor, thanks to the significant variance in recharge-cycle capabilities, but the upfront sticker shock factor can’t be dismissed, either.

One other key difference between SLA and LiFePO₄ (and other lithium-based technologies, for that matter) involves their varying instantaneous-power responses (something that I also recently experienced firsthand). As “narfcake” noted in the Meh forum discussion on the Phase2 Energy PowerSource 660Wh 1800-Watt Power Station:

The caveat is that LiFePO4 is usually just rated for its output – expect a 50Ah battery to max out at 50A output. AGM/SLA are capable of outputting much higher currents (with diminished runtime), hence tiny 8Ah batteries in a UPS being able to crank out 1200+ watts, which is 100+ amps.

Such instantaneous-spike support is also beneficial, for example, with refrigerator and freezer compressor motors or any other device with higher-than-nominal startup power needs.

In closing, while we’re comparing different battery technologies, a few words on LiFePO₄ versus the other lithium-based approaches I’ve already alluded to are probably in order. The list of alternatives begins, I suppose, with the disposable (non-rechargeable) lithium metal cells used, for example, in my Blink security cameras. But given that the applications we’re covering in this post all fundamentally rely on batteries’ recharging capabilities, the primary alternatives are lithium-ion (Li-ion) and lithium polymer, more accurately stated as lithium-ion polymer (Li-Po), a Li-ion derivative which uses a semisolid (gel) polymer electrolyte instead of a liquid electrolyte.

Lots of online resources exist, with varying emphases, accuracies and vested interests along with breadth and depth of detail, in striving to compare these three rechargeable lithium-based technologies. LiFePO₄ batteries are generally understood to have the highest cycle counts, for example, translating into long life, and are also comparatively immune from thermal runaway and overheating. But they’re the most expensive of the approaches on a cost-per-capacity basis, likely in part because they’re the least mature of the three. Li-Po seemingly has the highest charge density and can also be molded into a variety of flexible form factors, but is prone to swelling along with fire and the like, therefore requiring careful handling both while in use and in storage. And Li-ion, perhaps the most mature of the three approaches, is in many respects an intermediary step between the other two from various evaluation factors’ perspectives.

That all said, as I’ve mentioned before, I’m not a power engineer, so my understanding of these evaluation factors (and how each technology stacks up against them, both now and as they further mature in the future) may be incomplete compared to the knowledge base of at least some of you. As always, therefore, please sound off with your thoughts in the comments!

—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

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