Portable battery storage on wheels has become a standard offering from a host of battery system suppliers. Around two dozen companies showcased portable battery options at the 2024 Intersolar North America and Energy Storage North America in San Diego — ranging from the size of a toaster to a large camping cooler.
The appeal of these units may primarily be their portability, to power off-grid appliances while camping or doing remote construction work, but they’re also an intriguing option for homeowners in need of backup power in a pinch.
“One key to portable battery storage value is redundancy and reliability. Portable batteries are often plug-and-play, a much simpler system than grid-tied ESS, and thus have fewer issues. If the grid-tied ESS faces any issues or maintenance, portable batteries can act as a backup, ensuring an uninterrupted power supply,” says Sally Yan, a marketing specialist at Bluetti.
Portable batteries at Intersolar were on display as single units or as stacked systems, typically with three or four interconnected units in said stack. While these units typically cannot be hard wired into a home in conjunction with another vendor’s grid-tied wall battery system, a transfer switch can separate the grid from the battery input. When incorporating portable batteries at homes with solar and/or storage, those proprietary systems would also need to be isolated.
That transfer switch install + portable battery stack is a compelling option for the right customer considering the price. Portable battery units cost roughly half — or less — of what a similarly-rated grid-tied wall storage unit costs, many vendors reckoned.
“In terms of cost, our portable battery is more cost-effective than a grid-tied wall system. For example, our AC300+2*B200 is $4,398, it requires no installation, and this system provides 6.1 kWh, so it’s $0.71/Wh. In contrast, one Tesla Powerwall is $15,367 with installation from an official Tesla installer, and it’s 13.5 kWh, so it’s $1.13/Wh,” Yan calculates.
The Bluetti AC300+B300 unit with 3 kWh sells for $2,600. This combination is expandable with up to four B300 units for an output of 12,288 Wh.
Backup building blocks
Stackability is a major feature of portable systems. For example, the Renogy Lycan Pro model has a 4.8 kWh capacity, but can be stacked with interconnections to provide 19.2 kWh, enough to power critical circuits for days. The unit also provides a range of voltage outputs from 120 V to 500 V, with a maximum solar input of 500 Vdc.
Gotik is bringing its new larger DP6000iL portable to market in February, with the capability of stacking up to 30 units, says Ada Tang. The company’s CP4000iL provides 3.8 kWh and is priced at close to $2,300.
Home use of a portable battery or stack of batteries can help extend the period that energy is available for critical circuits during extended outages. A grid-tied wall mount system may supply power for a day or two, but some outages can last much longer.
Sizing a portable battery or stack is one task that a potential customer must weigh carefully. “They may need to consider the largest rate of power they require, which determines what output a system needs to have,” says Yan. “They need to consider how many days of outages are frequent in their city and calculate how much power they may need to guarantee a normal life during power outages, and this determines how much capacity this system needs to have.”
Some portable battery providers have already reached agreements with the major wall mounted providers, including Tesla and Enphase, so that adding the battery into the wall Energy Storage System (ESS) is not complicated. However not all grid-tied ESS providers are yet willing to “play nice” with portable battery unit providers, one vendor lamented.
Instead, several of these portable battery providers are beefing up their professional battery product lines, to offer solar + storage installers a plug-and-play energy storage system for grid-tied applications. How does that background in the mini, portable power space change their approach? The difference, according to Brian Shircliffe, sales director with Bluetti, is that “scaling up” their product lines (versus other manufacturers needing to scale down) leads to simplicity.
“So, instead of having multiple components that makes sense on a large commercial building or an open field — the inverter, the battery, some switching devices — we were able to miniaturize all that into one unit, with stackable batteries, that is already kitted,’ Shircliffe explains. “You’re able to install it within a very short amount of time.”
On this episode of The Pitch, Shircliffe walks us through the finer points EP900 – Bluetti’s newest system for stationary whole home backup – as well as the virtues of pitching portable batter options to customers.
Second resort storage
Portable batteries can provide backup for customers with no solar or no grid-tied ESS, at a price point that makes them more affordable than the hard-wired alternatives.
“We’ve supplied a lot of our batteries to homes and apartments in Puerto Rico where the grid went down; most of these people had no backup power of any kind,” observed Patrick Heth, the senior sales and training manager at Mango Power.
The rolling Mango Power E offers 3.5 kWh, has 16 different power output configurations to power or charge virtually any device or appliance. Its four AC outlets are each rated for 20 A. The unit weighs in at just over 100 pounds. The lithium iron phosphate (LFP) batteries are supplied by CATL.
Similarly, Anker offers its Solix F3800 portable with an expansion battery to take the 6,000 W output combination to 7.68 kWh. The company also bundles the F3800 with a 400W solar panel, and offers a hybrid 12,000 W wall unit plus two F3800s for 7.68 kW of output, says Adam Weissman, a senior manager at the company.
Portable batteries and EVs may eventually have a full-circle relationship. Portable units may be used to recharge an EV to avoid punitive time of use (TOU) charges, as long as the EV charging rate is within the power station’s output range.
For example, the Gotik portable can provide a Level 1 charge, says Tang. The unit has an LCD screen with multiple analytic monitoring points.
Similarly, an EV can be used to charge either a grid-tied battery system or a portable battery bank, or both. The portable unit also may be carried on board the EV for emergency charging.
Not surprisingly, Nissan and other EV makers have begun to use mostly-depleted EV batteries to create portable batteries. Nissan has sold more than 650,000 Leaf EVs with batteries since its introduction in 2010, according to a company statement.
Portables replacing gas generators
The potential expansion of the portable battery market has yet to be calculated fully. Replacing gas or diesel-fired gen sets at the home or jobsite offers massive potential. Long-time home generator players in Generac and Briggs & Stratton have built robust home energy storage offerings, and a newer player, Instagrid plans to target the jobsite in North America.
“More than 50 million small, non-road combustion engines are built each year – almost all of these should be replaced by battery systems which are lower carbon, lower total cost and create a far better work environment for operators,” says Avid Larizadeh-Duggan, senior managing director and head of Teachers’ Venture Growth (TVG) in EMEA.
Instagrid wants to engineer battery systems to outperform the peak power of gas generators. The company’s Instagrid One is a 3.6 kW system (peak output of 18 kW and 80 A) with a rated energy capacity of 2.1 kWh.
Instagrid just raised $95 million in venture capital for its North American roll out. The round was led by TVG, part of the C$250 billion Ontario Teachers’ Pension Plan, with participation from Morgan Stanley Investment Management’s (MSIM) 1GT climate private equity strategy.
Charles W. Thurston is a freelance contributor to Solar Builder.
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