Big Neil Posted September 7, 2018 Share Posted September 7, 2018 So. for direct comparison lets disregard any systems other than Tesla's own Powerwall 2. Why is it not a good idea, to buy a full battery pack from a wrecked Model S/X, and with the addition of any additional kit required for the home interface, and to hang it on/against the wall somewhere, have that as your battery backup. Never mind about the capacity being way higher, think about maybe future proofing. Link to comment Share on other sites More sharing options...
ProDave Posted September 7, 2018 Share Posted September 7, 2018 Do you care to suggest where such battery packs might be available? Link to comment Share on other sites More sharing options...
Guest Alphonsox Posted September 7, 2018 Share Posted September 7, 2018 Renault are already doing this. i.e. recycling used EV batteries as home energy storage units. https://www.powervault.co.uk/ Link to comment Share on other sites More sharing options...
Big Neil Posted September 7, 2018 Author Share Posted September 7, 2018 24 minutes ago, ProDave said: Do you care to suggest where such battery packs might be available? Well i'm thinking ebay, but anywhere really. I'm just wondering about the thinking people have of it as an option Link to comment Share on other sites More sharing options...
PeterW Posted September 7, 2018 Share Posted September 7, 2018 1 minute ago, Big Neil said: Well i'm thinking ebay, but anywhere really. I'm just wondering about the thinking people have of it as an option I wouldn’t want anything as highly flammable as a Li-On battery pack of unknown provenance in my house.... I understand the logic however I’m not sure how you would get to a product that an insurer would accept as a low enough risk to not cause a massive hike in premium. Link to comment Share on other sites More sharing options...
newhome Posted September 7, 2018 Share Posted September 7, 2018 1 minute ago, PeterW said: I wouldn’t want anything as highly flammable as a Li-On battery pack of unknown provenance in my house.... Yes I can confirm Peter’s obsession with dodgy battery packs! ? Link to comment Share on other sites More sharing options...
Big Neil Posted September 7, 2018 Author Share Posted September 7, 2018 3 minutes ago, PeterW said: wouldn’t want anything as highly flammable as a Li-On battery pack of unknown provenance in my house.... I understand the logic however I’m not sure how you would get to a product that an insurer would accept as a low enough risk to not cause a massive hike in premium. Bloody good points. So it sort of works in principle, but insurance issues.. What do you think about that as a community storage. So lets say a small collection of homes, all with their own solar and battery backups, excess diverted through a system as suggested above. Could be put away from residential property then... Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 7, 2018 Share Posted September 7, 2018 I've built a few electric vehicles, a couple of bikes, a motorcycle and an electric boat. All used lithium batteries, much the same as those in electric cars (including my own). The really important issue is that lithium batteries present a significant fire and explosion risk unless they have a proper battery management system. This is not normally built in to car battery packs as a stand-alone system, it is integrated into the car charger and power control system, so when you get a scrap car battery it will not have the key battery management computer, and if it did, the chances are it wouldn't work as it would not be receiving data from the car data bus. Lithium rechargeable batteries have to be actively managed at the cell level, with the battery management system ensuring that no single cell in the pack either exceeds the maximum allowable charge voltage (to reduce the risk of fire or explosion) or drops its cell voltage below that where the cell chemistry may be irreversibly damaged. I've designed and built cell-level battery management systems, and it's a lot of work to build one for a large capacity pack, especially the testing needed to be absolutely certain that it will manage every cell in the pack safely. Much of the cost of lithium battery packs for home energy storage isn't in the battery, but in the battery management system, including the cell cooling system. For example, if you take a pack out of something like a scrapped Tesla, then you're going to have to find a way to operate the liquid cooling system that's built in to it - the pack just has a couple of coolant pipe connections, for the non-conductive, non-flammable, coolant system to connect to. If you get a pack from something like Nissan Leaf, then you'll have to find a way to make the air cooling system it has work, as that's driven by the battery management system. People have built their own home storage systems, using cells taken from scrap cars, and if you understand the risks and how to design and test a safe and reliable battery management system, and how to integrate that with the charger and inverter needed to make it work in a similar way to one of the commercially available home battery storage systems, then you're probably fine, in terms of getting it to work. Getting your insurance company to accept that it's OK and getting a Part P electrician to accept that it's OK when he/she comes to wire it into your house wiring installation and sign it off may well be a challenge, as any home made unit won't have the appropriate safety approvals. All told, it's cheaper and easier to just buy an approved system, I think. The cheapest systems I've seen are the Sofar ones, which start at about £1300 +VAT for the charger, inverter and a 2.4 kWh lithium battery module (which has a built in battery management system). Link to comment Share on other sites More sharing options...
vivienz Posted December 1, 2018 Share Posted December 1, 2018 Bumping this thread in the light of the current discussion re. Sunamp charging not being what we thought it was. @JSHarris I know that you've been keeping an eye on the price of the Sofar system - any change since your last post on this thread in September? My house will be all electric, too, and the thought of losing PV generation irks me enough to think about splurging some of my contingency fund on battery storage before I blow it on fripperies like new furniture. Thoughts, anyone? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted December 1, 2018 Share Posted December 1, 2018 Funnily enough I've been checking prices again this afternoon, in light of the problems with the Sunamp. Prices seem much the same, with the 4.8 kWh system coming in at just under £2k exc. VAT. Link to comment Share on other sites More sharing options...
Dreadnaught Posted December 1, 2018 Share Posted December 1, 2018 (edited) Amazing isn't it! One spends about £2,000 + VAT plus to store about 80p's worth of electricity and the economics can make this worthwhile. Edited December 1, 2018 by Dreadnaught Link to comment Share on other sites More sharing options...
vivienz Posted December 1, 2018 Share Posted December 1, 2018 Where do we stand on the VAT? I presume that it can't be reclaimed? Link to comment Share on other sites More sharing options...
vivienz Posted December 1, 2018 Share Posted December 1, 2018 2 minutes ago, Dreadnaught said: Amazing isn't it! One spends about £2,000 + VAT plus to store about 80p's worth of electricity and the economics can make this work. Principles can sometimes be costly things to hold. 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted December 1, 2018 Share Posted December 1, 2018 5 minutes ago, vivienz said: Principles can sometimes be costly things to hold. They can indeed! Looking at the (somewhat scarce) data that's available, it seems that a ten year life is a reasonably good bet, so that's probably around 2500 to 3000 cycles in practice (winter not being great). Clearly the sums don't quite add up, as 2500 cycles at a notional 80p per cycle (ignoring round trip losses etc for simplicity, and assuming that electricity prices don't increase over the next 10 years) gives a nominal return through life that's around the same as the capital investment (exc. VAT). However, what are the less tangible benefits worth? For me, having the ability to run some limited stuff during power cuts would be very useful (we had another three hour power cut last Thursday, for example, and will get several more through the winter, I'm sure). Hard to place a value on this, though. There's also the "feel good" factor of using more of the energy you generate yourself. Impossible to pin a value on, but nevertheless something to be considered when making an investment, much like the make, model and colour of car one decides to buy. I think the price of these system is so close to break even as to probably be worth the investment, given that I believe we are likely to see a significant increase in electricity price over the next 10 years. That alone may well tip a battery investment over into being profitable, who knows? 3 Link to comment Share on other sites More sharing options...
vivienz Posted December 1, 2018 Share Posted December 1, 2018 (edited) @JSHarris - where have you seen the best price for the Sofar system? I notice that the VAT rate on batteries is 5% when paired with a new solar PV installation. So, if I do this now, before my PV system is commissioned, I will only pay 5% rather than 20% if I do it as a retro-fit. Is this correct, anyone? Edited December 1, 2018 by vivienz Link to comment Share on other sites More sharing options...
Jeremy Harris Posted December 1, 2018 Share Posted December 1, 2018 16 minutes ago, vivienz said: @JSHarris - where have you seen the best price for the Sofar system? I notice that the VAT rate on batteries is 5% when paired with a new solar PV installation. So, if I do this now, before my PV system is commissioned, I will only pay 5% rather than 20% if I do it as a retro-fit. Is this correct, anyone? Think Renewables have the best prices I've been able to readily find online: https://www.thinkrenewables.co.uk/sofar-ac-battery-storage I'm pretty sure that your interpretation of the VAT rules is spot on, 5% if installed with PV, 20% if installed later. Link to comment Share on other sites More sharing options...
ProDave Posted December 1, 2018 Share Posted December 1, 2018 43 minutes ago, JSHarris said: Think Renewables have the best prices I've been able to readily find online: https://www.thinkrenewables.co.uk/sofar-ac-battery-storage I'm pretty sure that your interpretation of the VAT rules is spot on, 5% if installed with PV, 20% if installed later. But if installed in a new house before completion, whatever you pay should be reclaimable? Link to comment Share on other sites More sharing options...
newhome Posted December 1, 2018 Share Posted December 1, 2018 19 hours ago, vivienz said: So, if I do this now, before my PV system is commissioned, I will only pay 5% rather than 20% if I do it as a retro-fit. Is this correct, anyone? So I think the 5% rate is for those in existing homes having solar PV and batteries supplied and fitted as a package. If your PV man is fitting to your home and supplies and fits the battery too then it should all be zero rated as a new build. If you are buying a battery in as supply only it's not 5%, you will need to pay 20% VAT but then the full 20% will be reclaimable via the reclaim scheme. If you 'retrofit' after you've put your claim in then you are stuck paying the 20% VAT. Make sense? The 5% rate isn't applicable for new builds, it is a concession made for specific energy-saving materials and heating equipment being installed into existing homes. See VAT notice 708/6. The same installation into a new build should qualify for zero rating. https://www.gov.uk/guidance/vat-on-energy-saving-materials-and-heating-equipment-notice-7086 Link to comment Share on other sites More sharing options...
vivienz Posted December 1, 2018 Share Posted December 1, 2018 Splendid! Thanks's both! Link to comment Share on other sites More sharing options...
mvincentd Posted December 2, 2018 Share Posted December 2, 2018 I have a good friend with a business supplying and fitting Sofar (he's a bit more commercial than domestic orientated). I've just checked with him if he could do a special deal for build hub on a pooled order for several systems. I told him you've already identified sub£2000+vat for 4.8kw, supply only. He said by all means collate a total order requirement and he'll better that, but it will be fairly marginal as thats already a very tight price. If this is of any interest let me know. 1 Link to comment Share on other sites More sharing options...
Big Neil Posted December 4, 2018 Author Share Posted December 4, 2018 On 01/12/2018 at 17:58, vivienz said: umping this thread in the light of the current discussion re. Sunamp charging not being what we thought it was. What where who when???? What current discussion? Link to comment Share on other sites More sharing options...
vivienz Posted December 4, 2018 Share Posted December 4, 2018 2 hours ago, Big Neil said: What where who when???? What current discussion? Check out the Bulging Sunamp thread. Link to comment Share on other sites More sharing options...
vivienz Posted January 15, 2019 Share Posted January 15, 2019 (edited) I'm going to place an order for my batteries very soon but want to be absolutely certain that I can claim back the VAT in due course, along with everything else that's going into the building. I'm going to order them myself rather than source them via my PV supplier as that system has already been installed and paid for. Can anyone point me in the direction of the section of the VAT reclaim regs that confirms that I can do this? Thanks! Edited January 15, 2019 by vivienz Link to comment Share on other sites More sharing options...
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