diy solar

diy solar

Newbie with some issues.

ScottishBadger

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Joined
Nov 19, 2022
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Hi folks, new here, been playing with Solar for a few years. My installation is not typical of a domestic UK installation, which seems to throw most installers....! Sorry if this rambles on a bit, but I'll give an explanation of the currently installed system before I start asking about the issues. I've attached a schematic of what's installed.

The only place I could put panels and inverter when the original system went in was my workshop roof, facing South-East. The workshop is detached from the house, connected to the house Consumer Unit by some 30-odd metres of 32A armourflex cable, suitably buried. 4kW of panels were fitted with a Fronius 3.6kW inverter, roughly 6 years ago, and it all worked fine, feeding back to the house when solar generation was greater than workshop usage. Sadly, the original installer went out of business, no idea why as he was good (and busy!).

About 2 years ago, fed up seeing all my lovely solar dumping to the grid on sunny days I started looking into battery storage - this was incompatible with the Fronius inverter, so I looked at other solutions and settled on a Puredrive Purestore II 10kWh AC. An electrician friend and I both did Puredrive's "Installer course" (a bit of a joke if I'm honest!) and they then sold me a unit which we self-installed in the house. This is in the hallway adjacent to the main Consumer Unit - which we re-wired to split into non-essential and essential circuits to make use of the Purestore's backup power capability, to retain heating, lighting and internet in the event of any power cut. This has worked well, apart from a recent hiccup where it seemed to lose track of one of the batteries SOC. A full reset followed by complete discharge and recharge seems to have straightened it out though, and it's working normally once again. It has issues, but I'll come back to that.....

This year, I decided to add more solar. I settled on 2kW of panel (max roof space available on an outbuilding adjacent to the workshop), facing South-West to catch the late afternoon and evening sun, supplementing the existing 4kW array facing South-East. These were installed on their own Solis 3kW RHI-series inverter, mounted in the workshop alongside the Fronius unit, and again worked just fine. The combined outputs of the two solar arrays feed back to the main domestic Consumer Unit and feed the Puredrive.

I then decided to add more storage. I was met with comments such as "you can't", "Puredrive can't be added to", "It won't work" etc. I tried to explain that any storage added would be out in the workshop, that the existing Purestore would/should simply see it as a "solar" supply on the cable from the workshop, the same as it sees the output from the two solar inverters. I eventually spoke with a company that suggested using a Solis RAI charger and Fox-ESS LV5200 battery, giving me an additional 5.2kWh of storage and it would be configurable to charge from cheap overnight electricity, same as the Purestore. We discussed, and I accepted, that the two storage systems may "fight" each other, may discharge from one to the other, and there would be resultant losses. One theory is that offsetting the "grid setpoint" of the Puredrive system may reduce this to a minimum. The RAI charger and Fox battery were installed last week, alongside the existing inverters in the workshop. The Grid CT signal gets to the RAI via an Acrel meter in the house and a buried Cat-5 cable sending the data back up to the workshop, the Solar CT clamp is on the main workshop power feed cable at the workshop end, so it can measure overall power flow to the house, seeing that as available solar for charging.

What I am now seeing is this - both systems charge overnight as programmed, but the RAI charger is only putting 640W out to the Fox battery, so only giving it 2.5kWh of charge in 4 hours. The BMS settings on the charger are showing 62.5A and the timer charge setting is 60A, so it should be getting 60A, which at 52v for 4 hours is a lot more than 2.5kWh! I am at a loss as to why the charge rate is so low when the settings are all set much higher? Fox-ESS quote a max charge rate of 100A, so I am thinking of going to "User Defined" settings instead of using the inbuilt settings for "FOX" and raising the charge current?

After timer charging has ended at 04:30, the Purestore then seems to continue charging the Fox battery until it is fully charged...... I still have all the energy stored, minus slight losses in conversion going from DC to AC then back to DC again, but I can live with that.

During the day, when a load is placed, the Purestore seems to ramp-up quickest, the RAI playing catch-up until they eventually reach some sort of equilibrium. But when the load is removed, one battery can continue charging the other for a while - no fixed direction of transfer either! The RAI seems to take no notice of the "solar" CT clamp, instead responding mainly to whatever signals it's getting from the Acrel Grid meter. I find this strange, as it should be seeing any incoming power to the workshop as "negative solar" and not trying to charge? I confirmed the RAI's PV clamp was the right way round by flipping it then turning on a heavy load in the workshop - it immediately went into charge mode as soon as it saw power coming into the workshop from the house, so why does it charge from the house battery when the PV clamp is the right way round?

My monitoring software for the Purestore (Victron) is very good, I can access more data and graphs than I know what to do with and this is where I can monitor the incoming "solar", with the added side bonus of being able to see how much power the workshop (and charger) is consuming due to the fact that the Purestore's solar clamp reads negative-PV when power is flowing to the workshop at any time when workshop consumption is greater than solar production. This has really confused Puredrive's "tech's", they cannot get their heads around a "negative PV" reading, telling me it is impossible, haha.

The monitoring software for the Solis is, by comparison, useless. I have to go up to the workshop and stand next to the charger to connect to it via the App on my phone, I can't monitor it from within the house, as I would like to. I'm not clued-up sufficiently to start playing with some of the equipment I've read about so far on this forum! The Solis RHI inverter has a "data logger" attached but it has never been accessed by me in any way and to be honest I've no need to - it produces whatever it produces, I've no need to see exact figures. Would this data-logger be compatible with the RAI charger and could I then connect to wifi (strong wifi in the workshop) and access the info that way, from PC software in the house instead of a phone App?

The issues.
1. Power transfer between storage systems. Not a major problem, more of an annoyance really, as I still have the power available for use.
2. RAI not charging the Fox-ESS LV5200 at a high enough rate on timer charging, with charge current set correctly.
3. Connectivity for monitoring what the RAI charger is doing remotely by PC, not a phone App!
4. Purestore - when charging, the internal temp of the inverter within the unit goes through the roof and the inverter trims back charge current to limit temp rising further. With the outer cover off the unit, it runs a whole 30 degrees cooler - shockingly poor design with nothing to remove internal case air except two pathetic small louvres and the inverter is mounted so high its air outlet is only 6mm from the top of the case, restricting airflow! As soon as it's out of warranty, case fans will be added!

If anyone can shed any light on the first three issues, offer advice or solutions I'd be most grateful, thanks. And if you stuck with this to the end, thanks for your patience!
 

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I wonder, to get around the air movement issues and not invalidate any warranties. Would it be possible to install a Pusher Fan at the bottom and a Puller Fan at the top (Computer type Box fan with ball bearings, not sleeve bearings) that only use a minimal USB power supply ?

Example from AC Infinity link below, I use a dual system with the "Controller 2" unit that has the temp sensors as well. These are NOT Computer Fans, they are diecast aluminium with ball bearings as completely silent ! The use very little power as well and quite reliable. NB I am not sure if they have power adapters for UK but I believe that any AC to USB adapter could be used or even a DC Stepdown converter to USB from you battery could be employed. You only need 6.5V/13W to operate a dual system & controller.

Links here: https://acinfinity.com/quiet-usb-fans/
Turbo Fan Power Adapter: https://acinfinity.com/component-usb-fans/ac-infinity-turbo-fan-power-adapter/
CONTROLLER 2, INTELLIGENT THERMAL FAN CONTROLLER, SINGLE ZONE: https://acinfinity.com/component-co...telligent-thermal-fan-controller-single-zone/

They are also Very Cost Effective (as in not expensive) compared to many other similar products made by other.

I cannot offer much feedback about the products that you are using as I am not familiar with them (I'm Canadian btw).
Current Sensing Clamps ARE direction sensitive, this is not new or unusual, they will indicate Positive for incoming & Negative for outgoing power but their accuracy can vary and they can pickup incorrectly if too close to a magnetic field and DC can be notoriously bad for that.

CONSUMER UNIT ? That term is not something I am used to. Make, Model & links to units would be helpful.
 
Hi Steve. The term "Consumer Unit" in the UK, is the unit that the mains power comes into within the home, after the power supply company meter. It contains circuit breakers or fuses (older and less common) for all the circuits and feeds within the home.

Appreciate your thoughts on the cooling issue, I was considering a single fan at one of the louvres on the side of the case, possibly attached inside with thin strips of sticky-backed hook & loop velcro, to avoid modifying anything. I had initially considered a computer fan and temp sensor/control, just to promote some airflow.
 
Ahh ok, we call that a LoadCentre (Mains Panel) with the primary main input breaker from the meter and the breakers to feed the circuits.

The AC Infinity stuff is top notch and they have smaller 40mm fans to 140mm ones. They are not plastic sleeve bearing junk like the A-Typical PC fans.
 
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