Are Plug-and-Play batteries a good idea?

Are Plug-and-Play batteries a good idea?

The following was written for the trade magazine “Inside Clean Energy” but published here for the benefit of our visitors…


The residential battery market is developing rapidly and although there’s no central data, anecdotally, it would seem sales are buoyant and growing. Industry giants such as Tesla, LG and Sonnen are leading the way although barely a day goes by without product launches from new entrants. As the residential solar market has struggled this year it has certainly been helpful to have the opportunity to sell these products that help existing customers get more from their solar PV systems. However there is the risk that a lack of understanding of the capabilities of these products, or inappropriate use of common phrases when explaining them, could lead to accusations of misselling by customers who feel they’ve been misled. One such concern is the use of the phrase “plug-and-play”. This article discusses what that means in practice, particularly consumers’ interpretation of the phrase, and seeks to avoid the term’s misuse.

Firstly it is necessary to differentiate between manufacturers’ use of the term plug-and-play when promoting their product to installers and installers’ use of the term with consumers.

Manufacturers use the term with installers to convey products that are easier and quicker to install which means the installation can be systemised and ultimately scaled more easily, more efficiently and therefore more cheaply. This is legitimate as the installer should be competent enough to understand this and the limitations.

For consumers the phrase can be taken differently so we need to understand what the phrase means to them. Furthermore, given there are products in development that are aiming to be plug-and-play in the consumer sense then:

  • Is this a welcome development for battery storage products?
  • Is it realistic given the technical considerations?
  • Where would that leave competent installers?

So, what would be a consumer definition of “plug-and-play”? In my opinion, a reasonable definition in terms of an electrical product, is describing a consumer product that can be plugged into a standard socket outlet and does not require the services of a competent person (with the relevant skills, knowledge, expertise and training) to specify, design or install it. Once switched on it should be obvious to the consumer that the product is providing the “service” the consumer expected when deciding to buy it. So, for example, a consumer purchases a high-definition television and when switched on, the consumer can clearly see that they’re getting a high-definition picture and not a blurred low-definition one (eye-sight permitting of course).

Such products should also be inherently safe, and certified as such, without the need for any modifications to the electrical installation.

Is this a welcome aspiration for battery storage?

As many commentators have stated our energy system is evolving from large centralised generation with a complex transmission and distribution system to conduct that power to where it is used. The future is an increasing proportion of decentralised generation based on variable renewables balanced with batteries (mobile and stationary) and demand management enabled by a smarter grid. This is an exciting future and one my company Poweri is actively pursuing in any way it can. As far as I’m concerned any development that makes that future more accessible (cheaper and easier) to energy users is, in theory, a welcome development as it gets us there faster.

What about the technicalities?

So, although in the grand scheme, cheaper and easier to install battery storage systems might be a good idea, is plug-and-play as defined here appropriate given the technical considerations? Clearly d.c. coupled systems should never be promoted to consumers as plug-and-play as they will always require a competent person to specify, design and install, but what about a.c. coupled systems? The first consideration always has to be safety especially given the definition suggests the battery system is not connected to its own dedicated final circuit. I’m not a qualified electrician so don’t have all the answers but I know enough to pose relevant questions and most of these apply to products intended to give power during a power cut i.e. island mode (and there are some in development which a quick Google search will reveal):

  • How would such a system differentiate between loss of the Grid and the plug just being pulled out of the socket so that the plug-pins are not live?
  • How would G83/2 compliance be achieved principally in terms of loss of grid and protecting engineers working on the network if there’s no relay between the consumer unit and the incoming supply?
  • Would fault protection (RCD) on the ring-main still function correctly in island mode?
  • What are the implications of a loss of earth during a power-cut where a TN-C-S or TN-S system? An earth electrode may be required.

So that’s just some of the safety considerations I can think of but even systems not designed to operate in island mode, only ever in parallel with a Grid supply, will need to be notified to the Distribution Network Operator under G83 or even G59. Will consumers be able (or even want) to do this and be aware that, if they don’t, a DNO would have the right to disconnect?

Another obstacle could be the visibility of the “service” (functionality) provided by such products. Theoretically they could have smart-phone apps to check they are working or to alter settings. That is fine but I don’t need my iPhone to check my TV is working or is giving me the picture quality I expected (hence the earlier analogy). Nor do I need my iPhone to know my kettle, iron, fridge or radio etc. are working either (although I might be able to control them in the future). Given useable battery capacity, battery chemistry and inverter power output are important considerations when deciding on the best battery storage system in a given situation (i.e. load profile and size of PV system); getting it wrong will lead to consumer dissatisfaction (and perhaps complaint). If and when they do notice on their app that the system isn’t fully powering their tumble drier and washing machine at the same time (through a 13Amp plug!) or the battery only lasts until 6pm then they might be a little dissatisfied. A conscientious installer would take all of this into account in the specification and sale and be careful to ensure their customers’ expectations are not unrealistic.

Where does that leave conscientious competent installer?

So, to summarise, battery storage systems might one day be available as off the shelf plug-and-play consumer products sold by Currys or Amazon and this might be a good thing if they can fully address all of the issues discussed here (and there’s probably more). Until that time (which might be some years away yet) there should be a rosy future for conscientious competent installers to correctly specify and install battery systems giving their customers a valuable service.

If you are currently selling battery storage systems to consumers as plug-and-play then:

  • At worst, you risk being accused of misrepresenting the product (especially if you’re also claiming it provides power during a power cut) and/or poorly specifying it
  • At best, you risk devaluing your own expertise along with the value you add as a company and that’s bad business.

Author: Chris Roberts, Poweri Services Ltd

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