Solar & battery monitoring

I have used EmonPI for a number of users and the Solar app has been great for monitoring generation v consumption. Last week I had a PowerVault battery fitted and need to make some adjustments to the configuration and from my understanding create my own dashboard as the Solar app will no longer function correctly?

In total, I will need three CT, one for the import/export at the meter, one for the generation from the solar and a third (new) CT for the battery to measure charge/discharge?

Three CT will mean that alongside the emonPI I will need an EmonTX for the third CT?

Are my assumptions correct?


I think the battery charge-discharge will be DC? The solar also?
The CT’s only work with AC.

Blockquote I think the battery charge-discharge will be DC? The solar also?
The CT’s only work with AC .

In my instance, each solar panel is fitted with a micro-inverter and the feed from the roof to the CU is AC. The PowerVault battery takes an AC feed for charging and returns AC for power. It internally has its own inverter from AC to DC.

That would be a rectifier, vice an inverter, would it not?

Yes you will need an emonTX. I’m using one to monitor solar /grid and also a pv3 I’m still trying to figure out how to integrate it with a dashboard to give me an easy to view SOC

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It’s listed as a hybrid solar inverter

Might even be a buck/boost converter?

For AC → DC, it’s a rectifier; for DC → AC, it’s an inverter.
I don’t think there’s a generally accepted name for the combination when both functions are performed by the same unit.

That means it can simultaneously manage inputs from both solar panels and a battery bank, charging batteries with either solar panels or energy from the grid (depending on which is more economical or preferred). Their capabilities may go beyond this – some also handle inputs from wind turbines, generators as well as other power sources.

It’s all a learning curve for me, I do know at the moment it can only be fed via ac as having an ac and dc solar source causes issues(software limitations I believe) I had to ask them and then buy an additional solar inverter for my additional solar I that was added

Probably not.
A B/B converter is a DC to DC device as opposed to the AC to DC device the OP is referring to.

After rectification it’ll have some kind of controller, is the point I’m making.
Could be a PWM charge controller, or buck/boost…

But the point the OP made was with respect to AC getting converted to DC.

It is a rectifier that converts AC to DC yes. I didn’t mean to subtract from that argument, only to add that it’s not just a rectifier at work.

My thought is you added to the argument - a lot of needless confusion.

Fair comment. Sorry.
I wasn’t clear at all!

Thank you to everyone who took the time to answer my query and increase my knowledge


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Hi @PaulBl, I am due to have a powervault 3 installed in a few weeks, and was wondering if you had made any progress on monitoring the battery? Or any other experiences you could share?

Hi Ian,

The PowerVault v3 portal still doesn’t show the amount of charge/capacity of the battery, although this has been a long-standing ask it is still not available. PowerVault say they are working on it but beyond it being a priority no date has been published.

Spending some time with PowerVault portal I can see they have implemented a private API but this is not documented and unlikely to be made available. Another owner who also uses OpenEnergyMonitor products has put together a dashboard for reporting solar generation, battery charge/discharge and import/export from the grid.

As well as a PowerVault owner I also switched to Octopus Agile pricing. It means I can charge cheap, around 5p/kwh during the early hours and then use at peak when cost is 25p/kwh. During the day I manipulate the schedule depending on weather conditions e.g. allow discharge around 07:00-09:00 charge from solar between 11:00 and 14:00, then top up from grid before the cost peaks.


Hi Paul, I am also planning to move to Octopus and buy the cheap energy overnight just like you, and then try to determine hoow much the PV is likely to generate. I suspect that part will be quite some trial and error.
I already have an EmonTX, so I am hoping I can just add one more CT clamp to monitor the current for the battery. Have you had any success with this yet?