Different battery sizes

Wondering if anyone has a system with multiple batteries of different capacities.

I have a single 8.2 kWh and an AC3 inverter and wondering about adding an additional 5.2 kWh battery. I wouldn't add another 8.2 kWh as then I can't charge them to full in my 4 hours of Octopus Go.

In the brighter months 8.2 is plenty, but in the winter the extra capacity would mean more days without running out of cheap overnight electricity.

How well does the system work with different battery sizes?

I am actually looking at adding the 9.5kw to my 8.2. All I know is the larger battery will be primary and the smaller moved to slave. As for how well work together, not sure. But for me I am on Go Faster 5 hour with an AC3 so I will not be able to fully charge them but there are other perks for me. Currently generating 40kw a day so if I can store more I can dump more into the EV overnight. When the EV finally arrives sometime in 2122.....

So I will also be interested in answers to this one!

I see where you are coming from and I would agree that bigger is always better, but I was trying to increase capacity for a more minimal cost (means I'll get it past the budget holder easier too!).

Currently on temporary EV but should be getting the permanent one in June...fingers crossed.

Mind if I ask what the cost of a 5.2kw installed is? Lets say 4.6kw too ;-)

Another reason I wont consider the smaller batteries is you do not get their full capacity which adds value to the larger as well plus throughput limited warranty.

No ideas on cost yet as I still need to ask my installer...and if we're going to be correct it's 4.6 kWh not kw!

I was planning to ask for quotes at the various sizes and take it from there.

😀

Well if it helps as a starting point adding a 9.5kwh to my system will cost £3200. That is fully installed with an estimate install date of end of August at the earliest depending on availability of gen 2 kit.

Seems like a good price as the one place I can see a price for the 9.5kWh battery online is £3225 just for the battery. I might just have to settle for what we've got especially as I've spent money on Ripple already too.

I need to stay off this forum as it always makes me want to get more kit. 😆

I am on the waiting list for Project 3 for Ripple..... But yes I know what you mean!

Also, when our EV comes I'll technically have 73kWh of battery storage outside the house.

I went a convoluted route but pretty much doubled my storage (i'm on the old 6.5kWh usable GE battery) and also doubled my discharge rate on the Hybrid (so now it does 5kW instead of 2.6) for <£1600.00 by grabbing most bits from eBay.
3x 2.4kWh Pylontech's (80% DOD)
1x DC-DC Charge Controller.
Hard to explain how it works so see here
Couldn't get the maths to work back then for another 8.2 as that was pushing £2.5k+ on it's own.

Sounds like you probably have a lot more electrical know-how than me but it's certainly an interesting addition.

I am electrical biased in my job but this is all off the shelf plug and play stuff (literally - plug you PV string into it & connect +/- to the batteries)
So it's not too onerous to do. And it's all DC, so no form filling, DNO involvement or certs etc...

hoggy So you just plugged the goodwe gw2500-bp straight into the givenergy hybrid inverter? Can the Pylontech batteries still charge from the grid OK with that config?
If so, you have given me something else to think about playing with 🙂

derekfairweather
Yes just put it inline on the PV string before the GE one and it's none the wiser.
It has another CT which clamps next to the GE one so it sees the same, therefore once the GE battery is full (or your PV is beyond your battery charging capability) it starts siphoning off power from the PV string into the Plyon Batteries.
Works other way around if you start pulling from the grid it injects additional "fake" PV into the string to either boost whatever PV you already have or can even create "fake" PV panels in darkness. (Your graphs look a bit weird with PV at midnight though!)
I use it primarily for peak load as it responds 2nd to the GE inverter.
The only problem is there is no AC connection at all, so you can't force charge them (Although I can't see why you can't just use a standalone 10A charger on them if you really wanted to? It's just a battery stack at the end of the day provided you can set the voltages and disable the output while your charging it to stop a feedback loop.)

Well as my EV has been delayed, not just delayed but the order status has changed to NO ETA. I have ordered a 9.5kwh battery to be added to my AC3 and 8.2kwh batt. Estimated install is end of August, however supply issues etc also mean my 3kw solar panel installation for next Thursday might not happen, so I expect August for the battery is also highly unlikely! If I get it though I will let you know how it all works :-)