Solar PV battery options

Hi all. I have a Solis 6kw inverter and 5 kw puredrive battery. When charging from the grid on night rate what should the Charge Limit and Discharge Limit be set to? Currently at 050.0A for both. Thanks.

Thanks Jonathan. Can you tell me where to find the fill and discharge limits e.g. 20% to 80% or do they exist?

Thanks for the reply. I know there are big savings going down the DIY route but not for me. I am just spot checking the quote on the additional 5KW option.

Hi Jonathan. Thanks again for that. I was wondering can the DoD be adjusted? Like my car, which recommends keeping the battery at above 20% and below 80% when possible to protect battery life. Is it relevant to the PureDrive?

Sound Jonathan. That’s what I’ll do. Thanks again.

A couple of lessons for me. The Seplos BMS has four NTC terminals. I wasn't comfortable extending these cables so measure your battery distances and set your BMS cables to terminate at roughly the same point. I gave too much slack to the cables that were connecting to the furthest cells and this has made my install untidy. I may shorten these at some point. Measure twice and cut once.

It pays to think about the orientation your BMS is going to be in in its final state and plan the layout of your 16/25mm2 cables and the angle of your crimps on them. Seplos recommends 2 (or 3 for the 200A BMS) positive power cables and a single for the negative. I crimped two cables each with 16-6 crimps on the BMS end and one 35-8 each for the battery/inverter ends with the wires from both cables going into the same crimp end. Heatshrink wrap was the business.

I would say there should be some deals on Chinese new year that starts in February.

Hi Guys,

We've just started work on a new build passive house with a very large south facing roof. We have planning permission to have up to about 30-40kW of solar panels on the roof.

My intention was basically to get planning permission to plaster the whole roof in panels and then when it came time to actually build the house see what made sense economically in terms of tariffs etc. Looks like we won't find out for sure with this for another few weeks but it looks like it won't be great.

Previously it seemed as though battery storage (unlike the panels themselves) did not make financial sense but I've been reading here about the AliExpress DIY route with interest, it seems like you can get 10kW of batteries for a bit over 1k which seems great value.

I have a couple of quick questions on the DIY route for anyone that knows their stuff:

(1) How scalable is it? Most of you seem to have gone for circa 10kW of batteries. Is there any reason I could not do this with 30, 50 or more kW of batteries.

(2) How safe is this? My intention would be to have the batteries and inverter for the solar panels in a "shed" (very well insulated garage type room) separate from the main house by a few metre so the batteries would not be in the main house. That said I have 2 relatively young children and I'd be wary of anything that would cause serious harm if someone touched the wrong wire (though I'd have some sort of barrier to prevent access to the batteries). I see a bit of talk of "the whole thing could go on fire" but I'm assuming that's pretty unlikely

(3) The new house will have 3 phase power (partially to facilitate greater export of power) but mainly as we're building a very large house which despite being passive standard will still use a lot of power and be entirely (inc electric cars) run on electricity. Is there any issue with using the DIY battery rigs here with 3 phase power?

(4) I'm not up to date with my battery knowledge. Is there anything coming down the tracks that might drop the price of the standard Powerwall type products significantly in the near future? I'd ideally prefer not to have hundreds of batteries linked together in my shed vs some off the shelf product but at the moment it seems only the former option makes economic sense.

Sorry for the long post and thanks!

1. No limit on scalability. 16 200Ah LifePO4 batteries get you 10,240Wh nominal. You can scale to 32, 48, 64 or more. The battery packs will all operate in parallel so will be at 51.2V nominal.
2. LifePO4 is very safe. No risk of fire. Different chemistry to Li-ion that is used in Teslas and laptops and cell phones. As far as exposed wires are concerned, use the same basic precautions you would use with any electricity wires. Get yourself a case or cabinet to keep the batteries in and use insulated shrinkwrap to minimize any exposed surfaces.
3. No issue with 3 phase but you will need a three phase storage or hybrid inverter. You also need to decide whether you will get a hybrid inverter that connects to both the PV array and batteries or a non-hybrid for the PV array and a separate storage inverter for the batteries. Latter is more flexible, about the same combined cost for non-hybrid+solar inverters as a hybrid inverter but takes up more space. 3-phase inverters are also more expensive that single phase equivalents (but can handle larger arrays). I am not even sure if 3-phase hybrid inverters are easy to procure in Ireland so you may have to go separate PV and storage inverters.
4. Supply is tight right now as EV production ramps up. I don't think battery systems are getting cheaper in the next year or two. A 50kWh storage system (and you most likely won't need that) will be 80 cells not hundreds. Yes it's a large install but you can separate them into 16 cell modules, find or build decent storage cases for them. It's doable.

Likewise if it's not too much trouble! Thank you!!

speaking of youtube and other sites, any good resource for a total novice looking into DIY option?

At moment I am thinking to get a 2.5KwH battery with a PV install, then I do know an electrician who I guess could install or add on more batteries with ease- but I dont want to trouble him to wire the whole setup....

I assume he meant diy battery option. Been reading this thread but mostly lost if I'm honest.

Does anyone have a parts list?

I'd also add some sort of suitable fuse. There's a lot of potential in these batteries so worth investing in a fuse to protect things. Lithium Solar did a good video on the suitable types of fuses that should be used with lithium batteries.

Winnie Wong just broke his heart