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On-grid domestic battery storage

edited 30 November -1 at 12:00AM in Green & Ethical MoneySaving
1.9K replies 203K views
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  • joefizzjoefizz Forumite
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    I think you misunsderstand,  its not the power levels, its the way induction hobs work.
    Yep I know, I meant the power levels on the hob as in 1-9 ;-)
    At higher levels the switching time between on and off is less and within the battery recognition times so at higher levels the effect is less noticeable. You are correct that at the lower levels by the time its on and off again the battery hasnt had time to respond.
    Ive found that the higher the background load at the time of using the induction hob the better it is with battery use. So for example if the battery is already supplying power then the ramp up time is quicker, its the complete turning on and off of the battery that is the issue, not the extra ramp up/down.
    Try it with a background constant load already on to see if it makes a difference to your setup. Its counter intuitive to save energy you have to expend more ;-)
  • Exiled_TykeExiled_Tyke Forumite
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    joefizz said:
    I think you misunsderstand,  its not the power levels, its the way induction hobs work.
    Yep I know, I meant the power levels on the hob as in 1-9 ;-)
    At higher levels the switching time between on and off is less and within the battery recognition times so at higher levels the effect is less noticeable. You are correct that at the lower levels by the time its on and off again the battery hasnt had time to respond.
    Ive found that the higher the background load at the time of using the induction hob the better it is with battery use. So for example if the battery is already supplying power then the ramp up time is quicker, its the complete turning on and off of the battery that is the issue, not the extra ramp up/down.
    Try it with a background constant load already on to see if it makes a difference to your setup. Its counter intuitive to save energy you have to expend more ;-)
    I wondered whether this was an intentional feature of battery management systems? i.e. it's too damaging to quickly and repeatedly switch between heavy discharge to heavy charging rates. The reason I think this is I've noticed on occasions when I've had appliances on which work in this way, when I switch them off my battery has taken a good while to start charging again - it's as if the system is just waiting for the discharge to start again.    Any body know the answer? 
    Install 28th Nov 15, 3.3kW, (11x300LG), SolarEdge, SW. W Yorks.
    Install 2: Sept 19, 600W SSE
    Solax 6.3kW battery
  • SolarchaserSolarchaser Forumite
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    joefizz said:
    I think you misunsderstand,  its not the power levels, its the way induction hobs work.
    Yep I know, I meant the power levels on the hob as in 1-9 ;-)
    At higher levels the switching time between on and off is less and within the battery recognition times so at higher levels the effect is less noticeable. You are correct that at the lower levels by the time its on and off again the battery hasnt had time to respond.
    Ive found that the higher the background load at the time of using the induction hob the better it is with battery use. So for example if the battery is already supplying power then the ramp up time is quicker, its the complete turning on and off of the battery that is the issue, not the extra ramp up/down.
    Try it with a background constant load already on to see if it makes a difference to your setup. Its counter intuitive to save energy you have to expend more ;-)
    Yeah I understand your theory, that induction is on longer, givinh the inverter more time to respond, but even on the highest setting, it has already switched off before the inverter has caught up, and so does not solve the issue.
    However your theory that it gives you less wasted inverter power.... maybe, though in reality its marginal at best, and also you have now burned the food, it has to be thrown out, and you have to start again using more food and more power, so as solutions go, it's a non starter.

    The lux has 3 stages to ramp rate, and certainly if its already putting out 2kw, its easier to get to 3.4kw, however once again if im using 2kw to get the inverter to respond quicker.... how am I saving money?


    You have mentioned several times in the past that you are an engineer,  do I assume that you are a design engineer by trade?
    West central Scotland
    4kw sse since 2014 and 6.6kw wsw / ene split since 2019
    24kwh leaf and Lux 3600 with 17kwh useable storage
  • edited 1 October 2020 at 2:02PM
    SolarchaserSolarchaser Forumite
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    edited 1 October 2020 at 2:02PM
    joefizz said:
    I think you misunsderstand,  its not the power levels, its the way induction hobs work.
    Yep I know, I meant the power levels on the hob as in 1-9 ;-)
    At higher levels the switching time between on and off is less and within the battery recognition times so at higher levels the effect is less noticeable. You are correct that at the lower levels by the time its on and off again the battery hasnt had time to respond.
    Ive found that the higher the background load at the time of using the induction hob the better it is with battery use. So for example if the battery is already supplying power then the ramp up time is quicker, its the complete turning on and off of the battery that is the issue, not the extra ramp up/down.
    Try it with a background constant load already on to see if it makes a difference to your setup. Its counter intuitive to save energy you have to expend more ;-)
    I wondered whether this was an intentional feature of battery management systems? i.e. it's too damaging to quickly and repeatedly switch between heavy discharge to heavy charging rates. The reason I think this is I've noticed on occasions when I've had appliances on which work in this way, when I switch them off my battery has taken a good while to start charging again - it's as if the system is just waiting for the discharge to start again.    Any body know the answer? 
    The lux will switch almost instantaneously (2-4 seconds) from moderate discharge to charge and vice versa, say 1kw or so.
    Takes quite a bit longer to go from 3.4kw output to the same in input and vice versa, id imagine the lower outputs are geared to be more easily switchable. 

    However it takes rather a long time to wake up if its sat doing nothing.

    The sofar I had previously was definitely quicker to wake up from dormant, but slower to switch from charge to discharge and vice versa.

    Both were much faster than the growatt, the ramp rate on the growatt was painfully slow.
    West central Scotland
    4kw sse since 2014 and 6.6kw wsw / ene split since 2019
    24kwh leaf and Lux 3600 with 17kwh useable storage
  • EVandPVEVandPV Forumite
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    However it takes rather a long time to wake up if its sat doing nothing.

    The sofar I had previously was definitely quicker to wake up from dormant, but slower to switch from charge to discharge and vice versa.
    I'm just wondering if the 'grid connect times' in the settings are anything to do with this ??
    The default setting seems to be 30 seconds. Worth trying a lower value ??
    Scott in Fife, 3kwp pv SSW facing, Fronius inverter installed Jan 2012
    7.2kwh Pylontech battery storage with Lux ac inverter
    Raspberry Pi immersion controller
    Raspberry Pi Lux charge controller
    Renault Zoe 40kwh, Zappi EV charger and Octopus Go
  • mickyduck55mickyduck55 Forumite
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    EVandPV said:
    However it takes rather a long time to wake up if its sat doing nothing.

    The sofar I had previously was definitely quicker to wake up from dormant, but slower to switch from charge to discharge and vice versa.
    I'm just wondering if the 'grid connect times' in the settings are anything to do with this ??
    The default setting seems to be 30 seconds. Worth trying a lower value ??

    Play away and let us all know Cheers
    3.995kWP SSW facing. Commissioned 7 July 2011. 24 degree pitch + Solar Immersion installed May 2013, after two Solar Immersion lasting just over the guarantee period replaced with Solic 2000... no problems since
    13 Feb 2020 LUX AC 3600 and 3 X Pylon Tech 3.5 kW batteries added...
  • edited 1 October 2020 at 5:42PM
    EVandPVEVandPV Forumite
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    edited 1 October 2020 at 5:42PM
    EVandPV said:
    However it takes rather a long time to wake up if its sat doing nothing.

    The sofar I had previously was definitely quicker to wake up from dormant, but slower to switch from charge to discharge and vice versa.
    I'm just wondering if the 'grid connect times' in the settings are anything to do with this ??
    The default setting seems to be 30 seconds. Worth trying a lower value ??

    Play away and let us all know Cheers
    Just posing the question here first to see if anyone knows what the setting does.
    I'm not keen on messing with the grid settings without knowing for sure what they mean.
    The Lux documentation on this isn't the best.
    Scott in Fife, 3kwp pv SSW facing, Fronius inverter installed Jan 2012
    7.2kwh Pylontech battery storage with Lux ac inverter
    Raspberry Pi immersion controller
    Raspberry Pi Lux charge controller
    Renault Zoe 40kwh, Zappi EV charger and Octopus Go
  • joefizzjoefizz Forumite
    676 posts
    Ninth Anniversary 500 Posts Combo Breaker
    ✭✭
    Yeah I understand your theory, that induction is on longer, givinh the inverter more time to respond, but even on the highest setting, it has already switched off before the inverter has caught up, and so does not solve the issue.
    However your theory that it gives you less wasted inverter power.... maybe, though in reality its marginal at best, and also you have now burned the food, it has to be thrown out, and you have to start again using more food and more power, so as solutions go, it's a non starter.

    The lux has 3 stages to ramp rate, and certainly if its already putting out 2kw, its easier to get to 3.4kw, however once again if im using 2kw to get the inverter to respond quicker.... how am I saving money?


    You have mentioned several times in the past that you are an engineer,  do I assume that you are a design engineer by trade?

    Design engineer was one of the roles in the past, yes. (as well as implementation and test and user manuals, rollout etc)
    Its not a theory, Ive measured it with a fluke meter ;-)
    As I mentioned and it maybe got lost in the noise in the last few posts and in previous posts on this subject, it will depend on your particular system. I dont know anything about the lux but can tell you how the sofar works with the pylons.
    Up to the switchover threshold the switching time is slow. This threshold will depend on your solar output so at this time of year at tea time I can be producing anything from 0 to 600w roughly. So you want to be drawing this plus your inverter switchover threshold before starting anything to do with the induction. One of the next issues you have is, if the solar output is constant, if its moving all the time then your threshold will also vary so your background constant load plus your induction switching may top out your battery supply and you end up drawing from the grid anyway.
    We are talking about induction here but it also applies to the likes of washing machines, dishwashers etc where the load isnt constant and varies with cycle, its just the induction hob duty cycles demonstrate it quicker and if you can hear your inverter switching (as with the sofar) then you can also 'hear' the inbuilt timeouts and safety mechanisms where after a period of switching it slows that all down even further (well the sofar does anyway).
    In retrospect the half and half induction/traditional hob would have been ideal for this sort of thing, the food you want to cook low you put on the traditional hob to get the base load working then use the induction for other things. Of course that might still hit your maximum deliverable load so negate it all anyway.
    You are right, it is marginal. Very marginal and mainly a technical exercise in equipment behaviour. I got my quarterly bill down from just over a fiver to just over 3 quid so it really isnt worth the effort, compared to the benefits of using an induction. Saying that however I use the moka pot less now and use the one shot kettle with aeropress for my morning coffee (when I cant be bothered using the gaggia).
    These posts have been interesting because I didnt know the lux was stepped output, the sofar (as far as Ive tested) is gradual (again caveat, it has been with 4 batteries, 3 or less it didnt appear to be although I didnt measure it in as much detail). Im pleased with the sofar ramp up/down response times but going back to the design aspect, thats where the price differences come in between the likes of the sofar and more expensive options. Of course thats where the price _should_ make the difference but often its the branding, marketing and install and forget that make the difference in price. Its why I constantly refer to 'systems' in the majority of my posts on these types of subjects because how its all tied together is an important driver of behaviour.
  • joefizzjoefizz Forumite
    676 posts
    Ninth Anniversary 500 Posts Combo Breaker
    ✭✭

    Play away and let us all know Cheers

    Just as a follow up to my last post, this is the only way to find out!
    The reason I did all the testing in my previous post was that I put my sofar and batteries in the spare bedroom and people then complained about this loud switching noise all night! So I experimented with base load so that the batteries switched on once when the sun went down and switched off again when the sun came up and not on and off every time the fridge switched on and off, or worse constant clicking between the fridge and two freezers!
  • edited 3 October 2020 at 12:13AM
    SolarchaserSolarchaser Forumite
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    edited 3 October 2020 at 12:13AM
    joefizz said:
    Yeah I understand your theory, that induction is on longer, givinh the inverter more time to respond, but even on the highest setting, it has already switched off before the inverter has caught up, and so does not solve the issue.
    However your theory that it gives you less wasted inverter power.... maybe, though in reality its marginal at best, and also you have now burned the food, it has to be thrown out, and you have to start again using more food and more power, so as solutions go, it's a non starter.

    The lux has 3 stages to ramp rate, and certainly if its already putting out 2kw, its easier to get to 3.4kw, however once again if im using 2kw to get the inverter to respond quicker.... how am I saving money?


    You have mentioned several times in the past that you are an engineer,  do I assume that you are a design engineer by trade?

    Design engineer was one of the roles in the past, yes. (as well as implementation and test and user manuals, rollout etc)
    Its not a theory, Ive measured it with a fluke meter ;-)
    As I mentioned and it maybe got lost in the noise in the last few posts and in previous posts on this subject, it will depend on your particular system. I dont know anything about the lux but can tell you how the sofar works with the pylons.
    Up to the switchover threshold the switching time is slow. This threshold will depend on your solar output so at this time of year at tea time I can be producing anything from 0 to 600w roughly. So you want to be drawing this plus your inverter switchover threshold before starting anything to do with the induction. One of the next issues you have is, if the solar output is constant, if its moving all the time then your threshold will also vary so your background constant load plus your induction switching may top out your battery supply and you end up drawing from the grid anyway.
    We are talking about induction here but it also applies to the likes of washing machines, dishwashers etc where the load isnt constant and varies with cycle, its just the induction hob duty cycles demonstrate it quicker and if you can hear your inverter switching (as with the sofar) then you can also 'hear' the inbuilt timeouts and safety mechanisms where after a period of switching it slows that all down even further (well the sofar does anyway).
    In retrospect the half and half induction/traditional hob would have been ideal for this sort of thing, the food you want to cook low you put on the traditional hob to get the base load working then use the induction for other things. Of course that might still hit your maximum deliverable load so negate it all anyway.
    You are right, it is marginal. Very marginal and mainly a technical exercise in equipment behaviour. I got my quarterly bill down from just over a fiver to just over 3 quid so it really isnt worth the effort, compared to the benefits of using an induction. Saying that however I use the moka pot less now and use the one shot kettle with aeropress for my morning coffee (when I cant be bothered using the gaggia).
    These posts have been interesting because I didnt know the lux was stepped output, the sofar (as far as Ive tested) is gradual (again caveat, it has been with 4 batteries, 3 or less it didnt appear to be although I didnt measure it in as much detail). Im pleased with the sofar ramp up/down response times but going back to the design aspect, thats where the price differences come in between the likes of the sofar and more expensive options. Of course thats where the price _should_ make the difference but often its the branding, marketing and install and forget that make the difference in price. Its why I constantly refer to 'systems' in the majority of my posts on these types of subjects because how its all tied together is an important driver of behaviour.
    Hahaha, as seems to be the case lately,  you have picked me up wrong.
    You assume I'm asserting that yours is only a theory and you have to prove it correct, in fact I'm saying its a theory that is disproven on my hobs and my lux by the ramp rate. 

    I'm not commenting on your system, how could I?

    You being a design engineer makes so much sense, as a final test, install and service engineer (various roles over 20 years) I have often spoken at length to design engineers about their designs and theories, and how to modify them to exist in the real world.

    As I've had the sofar and now have the lux (anyone want a sofar thats gathering dust in my garage?) I can tell you that the sofar ramps faster if its already outputting as I'm sure I've said previously,  and of course with different induction hobs I'm sure that they will switch on and off at different points... no need to bring out the fluke, you can easily hear the induction hob clicking on and buzzing, and clicking off to silent.
    So if you have a longer "on" time and a faster ramp rate, its possible that its worthwhile on your setup.
    Its not on mine, I've proved that.

    The sofar is a faster response inverter imo, and I really liked it.
    It suffers from two problems in comparison to the lux.
    1. Output, 70a vs 60a both charge and discharge 
    2. The lux software/app is an actual handshake  where you can actively influence the inverter, rather than a report of information like the solarman

    You know that I've had batteries for a while now, so surely you know.... that I know... how a battery inverter works based on loads, but you explain it anyway, this perplexes me.
    I initially thought that this was to impart wisdom over lesser beings, but I dont think its done deliberately to annoy, and so I wonder now, as I have a friend with it, Aspergers? (Or perhaps just the problem of text vs actual conversation)

    Believe it or not. The sofar also has a 3 stage system as well, id guess most inverters will have something similar, this lists charging only, but im certain ive seen a graphical illustration of the 3 stage output.
    West central Scotland
    4kw sse since 2014 and 6.6kw wsw / ene split since 2019
    24kwh leaf and Lux 3600 with 17kwh useable storage
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