Solis 3kW AC coupled Inverter & Fogstar 5.12kWh Rack Battery ?

[Joules]

Theyre not daisy chained, theyre in parallel. The outgoing leads are connected to opposite ends of the parallel leads to balance out the small amount of resistance in the leads so that the first battery in line doesnt take the lions share of the work during charging and discharging.

There seems to be a contrast between battery four wire impedance testers and battery banks generally. Surely, it would be better to have BMS voltage sensing wires as is the case for impedance testers to give more freedom to the battery connection method? Guess this tech has yet to arrive.

 

[johnb2713]

There seems to be a contrast between battery four wire impedance testers and battery banks generally. Surely, it would be better to have BMS voltage sensing wires as is the case for impedance testers to give more freedom to the battery connection method? Guess this tech has yet to arrive.

I reality it's not a problem. If it aint broke, dont fix it

 

[bladerunnerpv]

Theyre not daisy chained, theyre in parallel. The outgoing leads are connected to opposite ends of the parallel leads to balance out the small amount of resistance in the leads so that the first battery in line doesnt take the lions share of the work during charging and discharging.

Right, that's why it wasn't making sense to me! Thanks

 

[Oldman22]

Its been a bit of a journey and a steep learning curve with help from members of this forum and others, but at last it looks like I can mostly leave my Solis ac coupled inverter and its gaggle of Fogstar batteries to just get on with it.

Being a self installation I had to apply to my DNO for G99 to cover both the original 2014 3kW FiT PV system and the Solis 3kW so I could export what I needed. That didnt take too long and The export MPAN was pretty quick arriving too.

The Fogstar battery BMS was not as happy to play with my Solis inverter as I would have liked, but with help from Ben at Fogstar and Pace the BMS manufacturers the regular firmware updates ironed out the creases. Being that the end user has full access to the BMS is a huge bonus, firmware updates can be installed in minutes and you are if you want able to view the working parameters of the BMS and see how your batteries are performing.

I was going to put the batteries in a Fogstar cabinet but the garage just doesn't have enough free space for it so they will be as you see mounted just off the floor clamped together as a block. The masking tape is covering the unused ports as it gets quite dusty in there & I've yet to take the protective film from the screens.
I do have a clear plastic cover that will slot over and protect the batteries from getting too dusty once I have them in their final position. Those cable twists are ideal for my clamp meter



With 3 Fogstar batteries I have almost too much summer storage @ 15kWh. Our grid background use is around 250watts at night while day time is 500watts background use. 15kWh is about our average total daily use. The solar in summer months produces up to 21kWh a day but we were almost giving a fair amount away in exports as it couldn't be stored.
That's all changed now, my ability to store and draw on the stored kWh with the help of my new friend Solis has made a real dent in my electricity from the grid consumption.

I am now seeing much less than .4kWh usage most days and less than .2kWh is not uncommon!
It would be hard to get the usage much below that as there will always be a tiny amount drawn from the grid as the home load changes and the Inverter ramps up or down to supply the load from storage.

I moved over to Octopus Flux so I can if need be use the cheaper import period of 2am to 5am to top up batteries as and when needed, winter is coming, days are already getting shorter.
I am also considering exporting to Octopus between 4pm and 7pm to cover the daily standing charge of 47p and put my account into credit.

 

[bladerunnerpv]

So you can now export to grid without MCS involvement?

 

[Oldman22]

So you can now export to grid without MCS involvement?

No, I have a 3kW MCS for my FiT system.

 

[bladerunnerpv]

Gotcha.
note to self : I really must learn to not skim read post before pitching in with comments !
Cool, congrats, hope it pays for itself in good time and the fogs prove reliable

 

[johnb2713]

Its been a bit of a journey and a steep learning curve with help from members of this forum and others, but at last it looks like I can mostly leave my Solis ac coupled inverter and its gaggle of Fogstar batteries to just get on with it.

Being a self installation I had to apply to my DNO for G99 to cover both the original 2014 3kW FiT PV system and the Solis 3kW so I could export what I needed. That didnt take too long and The export MPAN was pretty quick arriving too.

The Fogstar battery BMS was not as happy to play with my Solis inverter as I would have liked, but with help from Ben at Fogstar and Pace the BMS manufacturers the regular firmware updates ironed out the creases. Being that the end user has full access to the BMS is a huge bonus, firmware updates can be installed in minutes and you are if you want able to view the working parameters of the BMS and see how your batteries are performing.

I was going to put the batteries in a Fogstar cabinet but the garage just doesn't have enough free space for it so they will be as you see mounted just off the floor clamped together as a block. The masking tape is covering the unused ports as it gets quite dusty in there & I've yet to take the protective film from the screens.
I do have a clear plastic cover that will slot over and protect the batteries from getting too dusty once I have them in their final position. Those cable twists are ideal for my clamp meter

View attachment 15612

With 3 Fogstar batteries I have almost too much summer storage @ 15kWh. Our grid background use is around 250watts at night while day time is 500watts background use. 15kWh is about our average total daily use. The solar in summer months produces up to 21kWh a day but we were almost giving a fair amount away in exports as it couldn't be stored.
That's all changed now, my ability to store and draw on the stored kWh with the help of my new friend Solis has made a real dent in my electricity from the grid consumption.

I am now seeing much less than .4kWh usage most days and less than .2kWh is not uncommon!
It would be hard to get the usage much below that as there will always be a tiny amount drawn from the grid as the home load changes and the Inverter ramps up or down to supply the load from storage.

I moved over to Octopus Flux so I can if need be use the cheaper import period of 2am to 5am to top up batteries as and when needed, winter is coming, days are already getting shorter.
I am also considering exporting to Octopus between 4pm and 7pm to cover the daily standing charge of 47p and put my account into credit.

Nicely done, looks a really nice setup I guess at a very competitive cost.

 

[Oldman22]

Nicely done, looks a really nice setup I guess at a very competitive cost.

Yes John, It worked out well with the Solis RAI-3.0KW 48ES 5G AC Coupled Inverter under £680 delivered from TradeSparky https://www.tradesparky.com/solarsp...ger/solis-rai-3kw-48es-5g-ac-coupled-inverter.

Fogstar 5.12kWh rack batteries at £1350 delivered https://www.fogstar.co.uk/products/server-rack-battery-48v-5-12kwh.
Plus say £100 max for electrical interconnect items, more if you don't feel comfortable DIY of course.

On testing I found 1 battery was not quite enough storage to cover 24hrs but 2 would have done the job so I could have got away with £3480 for a 10.24kWh setup with 8yr battery warranty and 5yr Inverter warranty.

​

 

[Oldman22]

So 2 months have gone by since my last post on my installation and its benefits. Octopus Flux export was enabled and in July I imported 56kWh and exported 92kWh with just 1 day when there was so little sun I needed to charge at 2-5am to top up the batteries. July's total cost including the standing charge was just £4

August started badly with no sun for the first few days I had to import 2-5am to charge the batteries for 6 days then it perked up some and I ended up with 28kWh imported and 100kWh exported and my bill for August was nothing, they owe me £3.

Now winter is on its way and I will need to find my way around low PV generation so need to consider daily 2-5am imports at cheap rate rather than occasional ones.

I did try setting the inverter for 2-5am 50A charge (around 3kW) with the batteries at 67% at midnight. By 4.10am the batteries were full 100% but as the inverter was set to charge until 5am the grid covered the house for the remaining period when usually the batteries would have that covered. So there are 2 penalties to pay when grid charging batteries, 1 is the initial hourly rate per kWh and second is the house background usage is going to be fed by the grid for the time set for charging. Luckily the grid charge is lowest cost/unit in this period.

IF the sun shines enough during winter days the batteries should be 100% charged by lunchtime and some export will take place to claw back some of the charging costs and on some days I hope to clear the 46p standing charge too.

Not played with it enough yet to see of its really useful or not but this utility was brought to my attention by @Ronski
https://garydoessolar.com/utilities/dailymodellingutility/

 

[Ronski]

Not played with it enough yet to see of its really useful or not but this utility was brought to my attention by @Ronski

I had a brief play last night, it's interesting, but some of the better features like minimum SOC are only in the subscription version.

 

[Oldman22]

I had a brief play last night, it's interesting, but some of the better features like minimum SOC are only in the subscription version.

At £1.50 a month subscription plus vat minimum, I'm not sure it will be worthy of £21.60 per year. I have short arms and deeeep pockets.

 

[Ronski]

My thoughts as well, I might subscribe for one month and cancel just to have a play.

 

[Oldman22]

https://garydoessolar.com/utilities/dailymodellingutility/
I've now spent a bit of time modeling the outcome of adjusting solar array performance to match my previous history of monthly generation divided by the months days to give a daily average for whatever season is selected. Plus seeing the effect of selection of 5,10 or 15kWh of AC coupled storage with conversion losses of 5% and the use of forced charge 2-5am or not.

My September average generation 2020-2022 is 269kWh so just about 9kWh/day which is 57% for Autumn season in this model with my 2.9kWp array.
Remembering that with such a small array I suffer more than most in Autumn/winter.

If my batteries are 75% full at midnight and I force charge at 25A for 3hrs or 50A for 1.5hrs (only full hours can be modeled at selected kW rate) to get 100% batteries by 5am then it suggests with my moderate house usage of 10kWh/day that the batteries should at the next midnight be within 1% of the previous day end figure.
The model summary suggests my import cost will be 86p, export revenue 54p so creation a loss of 28p/day on average for September, plus 46p/day standing charge which sadly is not in the model, though I expect you can set up a custom usage profile to the value of 46p daily to add it into the calc's.
So a modeled average of 74p/day costs for me in September is £22.20 for the month. I have been assuming (without the model) that my Autumn costs should be around £1/day and worst weeks in winter £2/day so its looking like the tool may have a use, even if its a "what if" generator of outputs.
Remembering that the same month without solar or batteries would cost me around £118 puts it into perspective.

 

[Ronski]

The thing that confuses me is if I set the solar to 0% (its a really bad day!), don't force eport and only import off peak, it says I have a loss of £2.57

*Profit calculated as follows:

Expenditure
Imported Energy: £4.73
Starting Battery Energy: £1.79 (5.8kWh valued at a default import rate of £0.31 per kWh)**
Total: £6.52

Income
Exported Energy: £0.00
Ending Battery Energy: £3.95 (12.79kWh valued at a default import rate of £0.31 per kWh)
Total: £3.95

Loss
Total Expenditure - Total Income = £2.57

** This is treated as an expenditure (an investment if you like) as it could be lost by the end of the day.

But thats not the daily cost, the daily cost is £4.73.

Now I'm guessing that because I end the day on 44% SOC it see's some of it not used, but stored so in theory the next days charge won't be as much. I think I really need to use the pro version, to model it better.

 

[rich1]

Great post Oldman22, gives me some confidence buying my batteries from Fogstar. Just got to decide if I want their ready built unit or a SEPLOS kit... £2k for the 15kWh SEPLOS vs £4k for the Fogstar 15kWh rack.

 

[Oldman22]

Great post Oldman22, gives me some confidence buying my batteries from Fogstar. Just got to decide if I want their ready built unit or a SEPLOS kit... £2k for the 15kWh SEPLOS vs £4k for the Fogstar 15kWh rack.

If you are confident enough or have a mate who will assist you in the build I would go for the Seplos kit, that way you know exactly what you are getting inside and out and saving a big chunk of money too. That's what I would do if I had to start again, you just need the confidence to go for it.

 

[Mcskippster]

Hmm, always interesting to see others views.
I would not go for seplos and select a pace based bms probably from orient power eu and pay the premium.for the Jakkipper battery but that's not a kit.

It's good to have different knowledgeable varied opinions.

Andy on YouTube the off grid garage has some more recent videos on Seplos BMs everyone may wish to review.

If a diy battery build I would still personally select the pace bms based in Andys knowledge and possibly also add an active balancer although the pace BMS are doing OK at present.
I will add with the exception of the BMS choice the kits do look nice products.

I may as @Oldman22 said if I had a timemachine have origonally bought the seplos kit.
Now i would be looking to build soemthing diy like seplos with pace bms or if money coudl stretch sell on the seplos from the kit and get a pace bms.

I will also add Andy has a recent video on seplos where he tries some fixes sugested by viewers for the Seplos BMS, i.think the summery was he thi ks it shoudlnt be required but the solutions worked.

Also as a counter to my Pace bms preference maufacturers are generaly improving each new release of new bms and tou should check the version as they cannot yet be updated and flashed, it will be nice when they all can.


I agree Frogstar is not on my list for rack batteries and there are other posts on the subject.

 

[rich1]

If you are confident enough or have a mate who will assist you in the build I would go for the Seplos kit, that way you know exactly what you are getting inside and out and saving a big chunk of money too. That's what I would do if I had to start again, you just need the confidence to go for it.

Well I've got an HNC in Electronic Engineering and I've just started College (as a very mature student ) to do my City&Guilds Electrical Installation level 2. I've read and watched a load of stuff about the in's and out's of batteries so I think I'd be OK with the kit, especially as SEPLOS quite a common kit and Ben seems to be very helpful. I have a mate who's a fully qualified spark/solar installer too.

Not 100% decided on which inverter to go for yet. Thinking of a SunSynk 8kW unit. Most issues all seem to be about comms/protocol issues between BMS and the inverter, once you know you have decent cells installed.

How easy was doing the G99 yourself?

 

[Oldman22]

Well I've got an HNC in Electronic Engineering

How easy was doing the G99 yourself?

Well confidence abounds then

I found using Smart connect to UK power networks fairly straightforward. I did lots of detailed drawings of my mains connections, existing and new equipment etc but I seem to remember having a snag that was my new inverter didnt seem to be on the approved list, it in fact was but the search didnt find it. Once that was sorted it took just a couple of weeks and another 10 days for the export MPAN to get approved.