10 Things to Consider When Buying china energy storage products

Main Post #2 - Battery Options - Capacity & Cost

In post #1 I covered the (current!) economic case for solar-free battery storage, as a quick aside I thought it worth mentioning that there is also an environmental case despite the lack of on-site generation.

The UK electricity grid uses a variety of energy sources, some clean/renewable, others polluting/finite. The mix of clean to polluting sources constantly varies, but generally speaking, polluting fossil fuel sources are at a maximum during periods of peak demand (e.g. 4pm to 8pm). By importing the bulk of my electricity overnight, I'll be using a cleaner mix of energy sources and helping to reduce peak demand; wind energy tends to be particularly dominant during the off-peak 00:30-04:30 period:

 (UK Grid Generation for 24 hours 16/11/2022 - 17/11/2022)

Battery Options - Capacity & Cost

I'd like to cover as reasonably close to 100% of my 'peak-time' usage as possible with battery supplied power (that is, everything outwith of the Octopus Go off-peak 00:30-04:30 hours).

My annual house usage is ~3000kWh, which averages out at 8.2kWh/day (EV charging is not included as that will be done off-peak). Some days will be higher, some will be lower, I estimate I'll need ~10kWh of battery storage to safely cover the vast majority of days. It's also considered good practice for longevity not to let lithium batteries discharge below 10% or charge above 90%. Following that guidance, 12kWh of battery storage would look to be the ideal size.

Ideal capacity in hand, my first port of call was to price up 'plug-and-play' branded battery storage. Note that all options also require an inverter to act as interface between battery and grid.

Two of the most commonly recommended brands of battery are PylonTech and GivEnergy. Pricing changes regularly so it's always worth doing your own checks.

PylonTech produce a 5.1kWh peak capacity battery (US5000), I could source two of these for ~£3500 including VAT (note that batteries are VAT free if being installed at the same time as solar panels, not relevent in my case). That would give me 10.2kWh of storage, or 8.1kWh (£432/kWh) usable capacity with the 10/90% rule.

GivEnergy produce a 9.5kWh battery pack for a similar price to the PylonTech option, ~£3600. I contacted GivEnergy to ascertain exactly how much 'peak' capacity was within their 9.5kWh usable battery but they simply repeated that it was possible to discharge 9.5kWh (£379/kWh). Hmm...I suspect their peak capacity will in reality be closer to the PylonTech offering.

Then there's the option that I've settled on. A DIY battery.

So, how does the capacity and cost compare to the off-the-shelf options?

Shockingly well - ~£2633 (broken down during this and a following post) for 14.3kWh of peak storage, applying the 10/90% rule, 11.4kWh (£230/kWh) of usable capacity.   

That's 20-40% more usable capacity at roughly 75% of the price 😯.

A DIY battery is composed of battery cells (that store the electricity), a battery management system (BMS) to monitor and manage the cells, and an enclosure/storage area in which to safely locate the cells and BMS. In this post I will consider only the cells, the other components will be discussed in a future post. There are some other bits and pieces to purchase in order to safely assemble a DIY battery but we've a hefty margin to play with.

Battery Cells

For UK grid-tied domestic energy storage you'll generally opt Lithium Iron Phosphate (LFP or LiFePO4) cells; these are the present industry standard, offering longevity and safety for use in the home.

Most UK on-grid approved inverters (the device that transfers electricity to and from batteries) only work with '48V' batteries. LiFePO4 cells are typically 3.2V each and it takes 16 cells to create a '48V' battery, although in reality 3.2V x 16 = 51.2V (apparently the widespread use of 48V labelling somehow relates to lead acid batteries 🤔).

Cell Capacity

Cells are available in different capacities ranging from 105Ah to 304Ah. To convert Ah to Wh you multiply the Ah capacity by the cell voltage, e.g. 304Ah x 3.2V = 972.8Wh.

Remember, you need 16 cells to produce a '48V'/51.2V battery. When calculating the Wh capacity of multiple cells the Ah variable remains the same but the voltage increases by 3.2V for every 3.2V cell added, e.g. 304Ah x (16 x 3.2) = 15,565Wh = 15.5kWh.

By changing the Ah capacity of your chosen cells you can tailor the battery capacity to best suit your needs. You can also build two seperate batteries and link them together in parallel to add their capacity together but this will not be covered here.

I decided on 280Ah cells as they seem to have the wide availablility and would give me a battery of 280Ah x 51.2V = 14.3kWh peak capacity. Applying the 10/90% rule that gives me 11.4kWh usable capacity. That'll handle my daily usage and builds in a bit of headroom for battery degredation over time and small manufacturing inconsistencies between the battery cells.

Grade A or Grade B?

Grade A cells are cells that meet a range of strict testing parameters and are generally destined for 'high performance' uses. Grade B cells have failed one or more of these tests but can still be perfectly suitable for home energy storage where the demands are relatively gentle. 

This write-up by Fogstar provides opinion on the different grades of cells available:

The REAL difference between EVE Grade A and Grade B LiFePO4 Prismatic Cells

From that write-up and numerous threads over on the DIY Solar forum ( SEE HERE ) I decided quality-controlled 'genuine' Grade B cells would be absolutely fine for my use case. (Also, do you think that branded off-the-shelf battery providers are using premium Grade A 'automotive' batteries when, with good QC and cell matching, the end user almost certainly can't tell the difference between Grades?🤔)

Where to buy?

LiFePO4 battery cells are manufactured exclusively in China and I considered two options for purchasing them:

Option 1) Order from a 'reputable' Chinese reseller (you cannot buy from the battery manufacturer's directly) through Alibaba.com

I sourced quotes from Docan and Luylan, Alibaba resellers considered trustworthy by users on the DIY Solar Forum, they were very similar in price at around £1960 (16 x 280Ah cells) delivered to the UK DDP (i.e. including all import fees/duty). The initial price was significantly cheaper but Alibaba adds both a transaction fee and a payment fee to the quoted cost. Also, prices are quoted in USD and the British pound unfortunately plumetted around the time I was looking to order.

As a side note, Luylan were up front that their cells were Grade B and offered Grade A cells for a more expensive price. Docan claimed their cells were Grade A but it's common practice for even reputable Chinese suppliers to sell good Grade B cells as Grade A. As such I believe I would receive much the same cells from both suppliers. Less reputable sellers may supply used or borderline defective Grade B cells but still advertise as Grade A.

Option 2) Order from a domestic reseller (e.g. Fogstar)

Fogstar is a UK company, they offer 280Ah Grade B cells for £150 incl. delivery. They have seemingly always available 15% off codes on their Twitter/Facebook, taking the price to £128.50/cell, or £2040 for a set of 16. Fogstar have been in the battery business for several years and have an excellent reputation. Also, as a UK company, there are comparatively straight forward options for recourse should the cells prove problematic (ever tried shipping something heavy back to China? 😫).

With less than £100 seperating the two options, I decided it was worth paying a bit extra for the UK based reseller and ordered from Fogstar with delivery expected in mid-late December (in the 3 weeks since I ordered the exchange rate has shifted such that Alibaba is now £200 cheaper so it's always worth getting up to date quotes).

Next Post - Battery Management System (BMS) & storage solution

At the beginning of each year, we pause to reflect on what has happened in our industry and gather our thoughts on what to expect in the coming 12 months. These 10 trends highlight what we think will be some of the most noteworthy developments in energy storage in 2023.

• Lithium-ion battery pack prices remain elevated, averaging $152/kWh. In 2022, volume-weighted price of lithium-ion battery packs across all sectors averaged $151 per kilowatt-hour (kWh), a 7% rise from 2021 and the first time BNEF recorded an increase in price. Now, BNEF expects the volume-weighted average battery pack price to rise to $152/kWh in 2023. Lithium and nickel prices will also remain high in the coming year, given the uncertainty surrounding China’s reopening post-Covid Zero policy and the continued disruption to metal supply chains caused by Russia’s war in Ukraine.
• Volatility in supply, demand and prices continues, although lithium prices may start easing with new supply. In the second half of 2022, battery metals were buffeted by events around the world: Russia’s war in Ukraine intensified, China’s battle with Covid wouldn’t go away, inflationary pressures built and fears of recession grew. Yet a rally in metals prices persisted throughout most of the year, and the long-term outlook is bullish (despite signs that a short slowdown in metals demand may be imminent). While we’ll be watching all battery metals in 2023, we focus here on lithium, given its price throughout the second half of 2022.
• Announcements from a large battery maker and a two- or three-wheeler manufacturer give sodium-ion batteries a boost. Sodium-ion batteries, still in their infancy, are beginning to scale up. An alternative to lithium-ion batteries, sodium-ion battery technology offers could alleviate battery-market pressures — and potentially push down costs — as soon as 2026. For 2023, we speculate that at least one major battery manufacturer will come out with a significant sodium-ion battery product roadmap announcement. In addition, we think that two major energy storage system (ESS) products will be launched and that at least one large-scale two- or three-wheeled-vehicle company will announce a vehicle model powered by sodium-ion batteries.
• Solid-state batteries progress, with new announcements potentially adding more than 40GWh. Solid-state batteries have become the most promising technology for pushing cell-level energy density up to 500 watt-hours per kilogram and driving battery prices down in the second half of the decade. Several leading battery manufacturers, like LG Energy Solution, CATL and SK, as well as startups like Solid Power, Prologium and Quantumscape, have laid out clear roadmaps to commercialize solid-state batteries within this decade.
• US Inflation Reduction Act guidance is released, leading to more than $80 billion in new investments for the battery supply chain. The Inflation Reduction Act (IRA) was signed into law by US President Joe Biden on August 16, 2022, injecting at least $369 billion into the country’s clean energy economy. With a good chunk of cash going to the power sector and electric vehicles, the law represents the largest effort yet to strengthen the battery supply chain in the US. Under the ‘Advanced Manufacturing Production Credit’ and ‘Clean Vehicle Credit’ sections, the law introduced a variety of credits to support the domestic supply chain, from raw materials to battery cells, modules, electric vehicles (EVs) and energy storage.
• A weakened battery position forces the EU to rethink incentives. As the North American battery supply chain enjoys an IRA boost, European battery players will likely pressure the EU to offer new incentives, too. BNEF will be watching for the EU’s response, which may include new subsidy schemes for domestic manufacturing and ‘buy European’ requirements for local content. Facing waning enthusiasm for local battery-making, Europe will be under pressure to loosen state aid rules (EU competition rules that restrict subsidy spending at a country level rather than through the EU), ease permitting and potentially allocate additional EU funds toward the battery supply chain.
• As policies regulating raw material origination take hold in the EU and US, the Chinese battery supply chain devises creative workarounds. Chinese companies will be closely watching the rollout of IRA guidance, with a special eye to the regulation of critical minerals and battery components — and the definition of ‘foreign entities of concern.’ Ford and CATL are rumored to be considering building a battery manufacturing plant in Michigan, US, in a complex arrangement that would allow the facility to reap tax benefits while respecting the terms of the law. (Ford would own the facility while CATL would operate it.) Such creative workarounds will become increasingly likely among Chinese companies, especially among those that are interested in expanding into the US.
• Energy storage system costs stay above $300/kWh for a turnkey four-hour duration system. In 2022, rising raw material and component prices led to the first increase in energy storage system costs since BNEF started its ESS cost survey in 2017. Costs are expected to remain high in 2023 before dropping in 2024.
• The energy storage system market doubles, despite higher costs. The global energy storage market will continue to grow despite higher energy storage costs, adding roughly 28GW/69GWh of energy storage by the end of 2023. In gigawatt-hour terms, the market will almost double relative to 2022 installations. (In October 2022, BNEF estimated 16GW/35GWh would be installed by the end of the year.)
• Pumped hydro makes a comeback, attracting more investment than other long-duration storage technologies. Despite long lead times, BNEF is taking a stance that investors and policymakers will be banking on pumped hydro energy storage in 2023. We speculate that this may lead to more committed investments towards pumped hydro than for other long-duration energy storage technologies this year.