There are too many unknowns in your question @philmore 

Let's assume that you have only one PV Array and that your existing Alpha battery has an inverter which can accept the voltage and current ranges which it can produce.

Yes, you could install a DC meter between the PV array and the Alpha. Accrel and Eastron are possible manufacturers to consider. Their products are available widely online, and cheapest from AliExpress.

To comply with submitting data on which your FIT payment is based, the meter must be MID certified (for accuracy). And it needs to keep a record of the totals, possibly aligned with time. It's no good just having a £5 watt-meter like this for example.

Then we need to consider what safety isolation and protection devices you should have before the pair of solar drop-wires enter the cabinet housing the DC meter.

Perhaps you could give us a fighting chance of suggesting a DC meter by posting relevant photos of your Alpha ports, and say what PV panels you've got.

Posted by: @philmore

↑

I want to connect my Pv setup, which is currently AC coupled, directly to my Alpha battery. How can I replace the AC gen meter to retain my Feed in Tariff.  My battery installer said "speak to your FiT supplier". eOn say "we can't advise, speak to your installer."

Is there a DC straight swap meter I can buy?

Can anybody help please

You (or installer or other qualified party who would do the work) is going to have to make a full proposal, draw all the diagrams and then submit it to the FIT supplier who will say yes or no.

I think both of the responses you got are correct - it's not your FIT suppliers problem to tell you how to go about it. Likewise it's not your installer who can tell you what would definitely be approved. Plus many installers would rather stick their head in a blender than deal with all the FIT hassles I think.

@transparent Thanks for the reply. The main problem I had was knowing what make or model of meter would do the job, so thanks for those names. I have a solar array on the roof of a large shed with 2 x 5kw Solax inverters. The batteries are in a plant room attached to the farm house and are connected to the shed via a 10mm 3 core swg cable. The idea is to remove the 2 solax inverters and run DC lines to the plant room. The meter would have to be capable of measuring the pv output prior to the battery inverter. There may be a meter in the battery setup, but if there is I'm not sure if it would comply with the FiT requirement. I wouldn't be doing the work myself, but like to understand what is being done.

The existing system is all Macs, Fit approved and works fine; but my requirements have evolved with the planned addition of an EV charger.

If you've got long DC cables involved in the rework remember to get the DC meters put at the shed end so that you get paid for generation that ends up as cable losses 😉

That's a good idea 👍