Battery inverter and immersion heater divert together

[BMcN]

Looking at installing a battery inverter as mentioned in another thread.  At the moment I run a Solar iBoost for the water heater.  Obviously I do not want both CT running together trying to reroute the solar to battery storage and to the immersion heater at the same time.  

 

Has anyone got any experience of running these together?   Does the inverter maybe have an output to say when batteries are full and I could run that through a relay to the iBoost?

 

 

[RichardL]

I have a solic diverter which starts diverting if it sees anything go the grid, and once it starts tries its arm at increasing the diverted power provided nothing is imported from the grid -  i.e. will drain batteries if given the chance.

Anything can start the solic diverting - like a pulse of energy to the grid as something big turns off in the  house.

The easiest option I could see is a timeclock between the solic and the immersion - choose one with a battery backup so it remembers the time. Then the timeclock only allows diversion to the immersion in the afternoon when I'm likely to have solar and stop when the boiler timer is due to top up the water anyway.

Crude yes - cheap and simple - yes.

Edited February 3, 2023 by RichardL

[pudding]

Yeah I've got an iBoost and installed batteries last year. Pure coincidence but my iboost sender died late last year after 7years or so. I've just bought the iboost sender which is supposed to be designed to match a system with batteries in it; it's specified to require 250W export before it will turn on and start diverting to the immersion. So that 250W export requirement is supposed to avoid small temporary spikes in export and the batteries simply powering the iboost immersion. It kinda works, but I still seem to get it turning on and using battery power for the immersion, but I think this is simply because of lag in the system, and the CT coils not being 100% accurate, and I've got a few A2A units in our house and a few other items, fridge/freezer, that may turn on/off and use a few hundred Watts which must be more that the iboost CT coil and 250W can deal with, and just like right now when the sun is down and we have batteries powering the house, as soon as these turn off, the battery inverter will still be sending that power which seems to be detected by the iboost which then turns on for a small while. It doesn't runaway and will turn off after a while, but today, where we've not had any excess solar at all to export, the iboost still says it's diverted nearly 1kW. Obviously it's not wasted energy, but it's not the most efficient use of it. I'm going to do what Richard says above, and sort out some kind of timer so it can only run in the afternoon before sunset and only divert actual excess solar, and not battery power. Simple, and not exactly an elegant solution and it really shouldn't be required, but it'll do the job.

Edited February 3, 2023 by pudding

[BMcN]

It would be nice if they inverter provided a set of contacts to signal when the batteries were full and then a relay could be used for the iboost.  

[RichardL]

1 hour ago, BMcN said:

It would be nice if they inverter provided a set of contacts to signal when the batteries were full and then a relay could be used for the iboost.  

Yup -   +It would be nice if the smart meter did the same! -  but for import/export etc.

Needs a bit of design socialism / interoperability LoL


Thinking on - battery SOC is available in a register - you can get at it and drive a relay -  technically possible

Edited February 3, 2023 by RichardL

[Marvin]

1 hour ago, BMcN said:

It would be nice if they inverter provided a set of contacts to signal when the batteries were full and then a relay could be used for the iboost.  

Hi @BMcN

 

I do not know how an iboost works. We have different equipment installed:

 

We use CT clamp relays as the best fix.

 

When the PV is producing over either 2kW or 2.5kW or 3kW (depending which CT relay clamp is chosen) our 10amp electric vehicle charger energises. When the car is charging the CT relay clamp on tge EV charger cable stops the batteries from charging.

Likewise, when the PV produces over 1.6kW the battery charger energises, but not if the EV is charging.

 

Our Solic200 diverter energises any time there is excess power. Once the hot water tank is up to temperature, during the winter any further energy is diverted to storage heaters.

 

We have not exported any power since October.

 

Good luck

 

Marvin. 

 

[BMcN]

@MarvinWhat are the CT relays you speak of?  What drives the relay?

[Marvin]

Hi @BMcN

 

I looked up an iBoost. Its exactly the same as a solic200 except the CT clamp on our Solic is hard wired.

 

Here is one example of an adjustable relay clamp.

04K-SD-NO-AL Normally open-type current sensing switch current over-limit output closed switch signal.

The power passing through the hole in the clamp drives the CT to switch. making some kind of magnetic field? I don't know...

 

On 03/02/2023 at 16:29, BMcN said:

Looking at installing a battery inverter as mentioned in another thread.  At the moment I run a Solar iBoost for the water heater.  Obviously I do not want both CT running together trying to reroute the solar to battery storage and to the immersion heater at the same time.  

 

Above I assume you are meaning CT clamps.

 

You have to have a bit of thought about the system....

Firstly you are dealing with two different types of equipment using electricity 2 different ways:

Heating element are resistive loads

Battery chargers are inductive loads

 

As far as I understand, a pure heating element will run with less than full power, only taking longer to heat up, but a resistive load needs all the load to work properly.

 

So the iBoost using the CT clamped will monitor excess loads being produced and will divert any amount of excess load to a heater and it will work.

 

However, as far as I understand, a battery charger (say 240V AC to 12V DC) will not work without the full load being supplied.

 

The bonus about the CT clamp above is that it will trigger a switch inside that will connect the 2 terminals, depending on how much power is running through it but just like a normal CT clamp it is not connected to the mains power.

 

So what we did was set the power requirement on the clamp to the minimum house running amperage plus the amperage required to charge the batteries, and fixed the clamp on the positive from the PV. This meant every time the supply from the PV went above what the CT clamp was set to the charger would come on.

 

Your iBoost would still work as it monitors any excess to the grid. (usually on the wire from the consumer unit to the main meter)

 

What happens to your excess power when the hot water is fully heated?  

 

[Christiano]

I have a battery and Solar iBoost.

 

Initially we had a nightmare of iBoost draining the battery but we got it sorted. The way to sort it was to extend the positive wire to the iBoost from the consumer unit and route it through the battery’s CT on the power in cable, with the direction of current flow in the iBoost cable in the opposite direction to the direction of the power in. 

 

Since doing that, it’s all worked really nicely, I can’t remember if I had to change the threshold on the iBoost, but I think it’s still at the default.

[Marvin]

19 minutes ago, Christiano said:

I have a battery and Solar iBoost.

 

Initially we had a nightmare of iBoost draining the battery but we got it sorted. The way to sort it was to extend the positive wire to the iBoost from the consumer unit and route it through the battery’s CT on the power in cable, with the direction of current flow in the iBoost cable in the opposite direction to the direction of the power in. 

 

Since doing that, it’s all worked really nicely, I can’t remember if I had to change the threshold on the iBoost, but I think it’s still at the default.

Hi @Christiano

 

Interesting. It sounds like an iBoost is more complicated (technologically advanced) than a solic.

 

Unfortunately our solic is in a different building from the batteries and our battery system is off grid. 

Edited February 6, 2023 by Marvin

[Wil]

I had a Solic, then got my Tesla batteries. Couldn’t get them to play nicely together, so took the Solic out of circuit and now use a ‘smart relay’ to close the contact on the immersion when the batteries are nearly full and the sun is shining. This mean batteries take solar priority and then once nearly full, the immersion takes full whack until the solar input drops (say below threshold of the house). The Batteries allow for sun dropping behind a cloud and also allow the immersion to take full 3kW even if solar only producing 1kW. Then set a low limit on the batteries when it drops the immersion again.

 

It’s a bit of a bodge and would be far better to get the Solic to ‘see’ the battery- something like Christiano has done but I couldn’t work it out!!

 

 

[joth]

If you have a ASHP, you may do better to remove the iBoost solar divert completely. Run the ASHP at times of max solar and rely on the battery to smooth out the supply to it, and you'll get the benefit of the ASHP cop.

(With current pricing plans, where import is only twice the price of export, this logic can now apply even without a battery)