Thanks for the detailed description and drawing however it's away over my head i'm afraid. 😬 😬 

HI

Over 3 months ago I get solar system installed with Solis 5Kw Hybrid Invertor with PureDrive ll 5kwh DC battery.

Now I want to add another PureDrive ll 5kwh DC battery, I have contact my installer but they still not in a position as a company to offer additional battery installations. This is still due to supply and demand.

So now I will buying the batter myself but I need help, if someone already get 2 batteries can they be kind to share the picture how they are connected, do I have to buy addition items or will all the items be included in new battery.

Good question @ifty !
Before you splash out cash, let me just run a few points past you...

1: I've looked online, and there are Installation Manuals for Puredrive batteries available to download as a PDF, but they seem to apply to the earlier Model 1, and only cover installation of the first battery. You intend adding a new one to an existing system.

2: The installation manual includes instructions for a mains power connection and placing a Current Transformer (CT clamp) on the incoming electrical supply to the house.
My assumption is that those issues don't apply to you because that's covered by the first battery, which you already have.

3: That still leaves two possible connections required for an additional battery:

• the +ve and -ve cables, capable of carrying 100A or more
• the data communications cable (usually CAN-bus)

I can't tell if these are included with the purchase of an additional battery, or whether they must be ordered as a separate pack.
It's possible that the cable lengths differ for each additional unit which you add, for example.

4: The installation sequence includes changes which must be made to the PureDrive App which controls the unit. At this stage we don't know if those modifications can be made by a end-user, or whether it requires an "Approved Installer" to log in to the PureDrive portal using their special password.

5: Even if there are no mains connections to be made, and therefore no legal requirement for a qualified electrician, you must remember that both the original battery and the new one are live!
The order of connecting the thick battery cables and the sequence to do so, are due to safety... both for protecting the equipment, and the installer, from damage! 😲 
It's possible that PureDrive have implemented mechanisms to prevent novices from attempting this.

For example, if the new battery were 20% 'full', and the existing one is 50%+ full, then there may be a shut-off system to prevent hundreds of amps being transferred between the two battery units when they are connected. It's not just a matter of wiring them in parallel.

I haven't got a PureDrive battery, and I'll be ready to see if another owner confirms or denies the points I've just raised.

@transparent 

Thanks very much for you kind advice and information,

I just spoken to PureDrive and they said

1-you need to check your Serial Number and Firmware of you current battery (PureDrive can provide the Firmware version once they know the Serial number.

2-Make sure once you currently battery have charged between 50 to 60% before you connect both battery

3- Isolate the Inverter 

4 - Fellow the manual instruction to connect batteries as Parallel layout.

5- As my system is only 3 months old, so it should be straightforward to connect and run after that.

PureDrive Battery staff are very knowledgeable and friendly too.

so next will find the Serial number and firmware and then hunt for new battery. 

will keep the post update once i get new battery and setup, hopefully all gone well.

That's a refreshingly enlightened approach from PureDrive.

That strategy will allow their market to continue growing whilst reserving their approved installers to work on new sites.

I must pass comment on you being required to have your existing battery at 50%-60% SoC (State of Charge).

The underlying chemistry of lithium cells makes it very difficult to know the SoC whilst in the broad middle part of the voltage-range.

It doesn't take much of a voltage difference between the batteries to cause some very large currents to flow.

What's the worst that could happen...?

• blow an fuse in one of the battery packs
• the internal Battery Management System (BMS) can throw open the charge relay (or mosFET switches), thereby leaving that battery unresponsive

But if you've followed the instructions from the manufacturer, then we have every reason to suppose that they will assist you to remedy the situation, should it go wrong. 🙂 

I'd also like to learn how they issue Firmware Updates.

It might be possible to do this OTA (over the air) using an internet connection.
But energy equipment which can be upgraded like that is obviously more accessible for hackers to attack, thereby threatening the UK energy supply system.

Some companies have the latest firmware versions on their website for you to download.
You must then attach a laptop with a physical wire to push the new firmware across.
That's obviously more secure.

Other manufacturers will only send out firmware upgrades by email to verified/registered customers.
That can additionally be constrained to only upgrade a unit with a particular serial number.

None of this may matter to you.
But I hope you can see that firmware upgrades are a tricky issue to get right.

Our Smart Meters, for example, cannot be upgraded like this, even if a certified meter engineer is on-site.
Other countries are not so pedantic as the UK.
In time we will find out if our cautious attitude protects us from cyber warfare.

You no longer need to push tanks across a border to bring a Western country to its knees.

@squeakysim Hi, Puredrive themselves say my battery will discharge at a rate of 5kw limited by inverter and or solar generation. I suggest you ask them direct.