Solar PV battery options

unkel

I got a rudimentary V2H going from my converted EV. Basically when my home battery is empty on a bad day, I manually connect the HV battery of my car, via a precharge circuit, directly to my PV inverter. Which then thinks the sun is shining and starts producing AC to power my house. Simple, but working great!

daughy

I don't mean to hijack this conversation but I recently had delivered two, 48 volt, 100 amp prebuilt batteries from alixpress.

I have paralleled them, and all is fine.

I have connected them by can to my solis hybrid rhi 48 5k 48ES, after I activated the batteries using user defined it showed me the soc on the hybrid screen, and it matched what the battery screen said, I boiled the kettle to check for outgoing power and the was fine, both batteries worked parallel to eachother.

My issue is using user defined mode as it uses an equalisation voltage, it has a float voltage which is fine, but there lithium batteries so I don't think they should be equalised.

I can I think set the equalisation voltage parameter to 0 amps, but I didn't have time to check that, and also the solis app didn't show the bms, or the soc of the battery..

I could switch battery type to pylontech but I think they use a 15 cells and I have 16..

Any help would be appreciated guys

championc

What type of BMS do you have ? If you went with Pylontech, are you are selecting on the internet is the language that the inverter will expect the BMS to be speaking. All parameters are passed from the BMS - so it will pass 16s.

With a BMS passing parameters to the inverter, it essentially turns the inverter into a dumb box

redmagic68

https://efficienthomesolutions.ie/product/storage-battery-sofar-15kwh-gtx-3000/

what’s the thoughts?

https://www.boards.ie/discussion/comment/119778234#Comment_119778234

I think that's a high voltage battery

redmagic68

Yeah missed that they’re lip instead of lifepo. Not so great after all.

bullit_dodger

https://www.boards.ie/discussion/comment/119776667#Comment_119776667

I'm torn a little bit on that one myself (the V2H bit). I mean I "get it". I get the benefits, and as any regular reader here will know, generally I'm a huge battery proponent - despite FIT, which...... incidentally I've yet to see a penny. No batteries are my friends and I love them :-)

The thing that worries me a little about V2H is the capacity depreciation on the battery which has a direct knock on effect on the range of the vehicle. Sure, for an odd V2H "cycle" that's fine, but as we know batteries have a limited number of cycles and quickening that lifetime will reduce range quicker.

it's not black/white of course. Yes, you will ultimately reduce the range in your car if you were to do this EVERY day, but then again, you are savings yourself wonga. Dunno - it's a hard one to call.

I'd be more inclinded to have a battery for the hosue and a battery in the car and if needed I'd V2H on occasion. is that the "best" way? Hard to say....

Just some musings.....

unkel

You really needn't worry. A LiFePO4 battery has thousands of cycles and can do a million km and then still has 70-80% of the original capacity. Sure if you power your house as much as your car with it, we are still talking a life of half a million km. Is that not enough for you? 😁

"I'd be more inclinded to have a battery for the hosue and a battery in the car and if needed I'd V2H on occasion. is that the "best" way? Hard to say...."

That's exactly my setup. Manually hook up the V2H (takes just a few seconds) on a bad day when my home battery is empty early

the_amazing_raisin

https://www.boards.ie/discussion/comment/119786763#Comment_119786763

It's worth remembering that the typical discharge from an EV battery is a lot higher than what your house would consume. You're talking ~20kW from cruising along on a motorway, or 150kW of you're flooring it

By comparison, everything running in your house might just top 10kW, and typical load would probably be less than 5kW.

And you're limited in how much you can take out of the battery for V2H anyway. The most powerful one I've seen is 22kW, but I'm pretty sure that's 3 phase. So 7kW max is probably all you'll get

The degradation of a battery is partly dependant on the discharge power and depth of discharge

So cycling an EV battery for V2H will degrade it a bit, but the vast majority will be from driving around.

I think the best way to use them is as a supplement to a smaller house battery. You can use the car to store up a load of excess solar for a day or two and if the sun isn't shining for the next couple of days you can use the car to supplement this

noc231073

https://www.boards.ie/discussion/comment/119744349#Comment_119744349

How much are u paying for the 5kwh battery ? And are u buying direct ?

Bif

https://www.boards.ie/discussion/comment/119789890#Comment_119789890

Got my first one with my original install and got my second one from a person who had replaced their Puredrive with a different battery setup.

Midlakelands

https://www.boards.ie/discussion/comment/119790008#Comment_119790008

Hi @Bif

Did you go with the wiring configuration recommended by jonathan earlier? Will change mine to that but first I sent a support message to puredrive just in case there's some weird reason they prefer the one in their documentation.

SchrodingersCat

https://www.boards.ie/discussion/comment/119788687#Comment_119788687

Dont most EV's have a lipo battery, not lifepo, which has a much smaller number of charge cycles compared to lifepo?

Lifepo are typically 5000 cycles whereas lipo in cars is ~1200 cycles. Worst case scenario, if you were using VFH daily you would reduce the lifespan of your cars battery to 3 years, which doesnt even include the additional cycles due to driving the yoke?

Unless im missing something here.

Bif

Hi @Midlakelands. Yip, went with Jonathan’s wiring schematic. Like you I had some doubts based on Puredrive documents and some online videos but speaking to a few people, all confirmed Jonathan’s plan.

bullit_dodger

https://www.boards.ie/discussion/comment/119788798#Comment_119788798

Ahh - I'd be fairly well clued in with the chemistry here. All what you said is true, and I'd also add that it depends a little on the temperature of the battery, where in the SOC that you're discharging/charging from, etc.

No all good points along with unkel's comment about 5000-10000 cycles. What I'm saying is that for fully day-to-day usage, I'm not sure I'd be totally bought into using the car as the storage for the house. Sure, the occasional use (let's put a number on it 2-3 times a month) yeah makes sense. Good thing to do.

The reason I'd personally be slow to use it fully for everyday, is that range of the car is important to me. My old 50Liter Honda Civic I know I could get 319 miles out a fill tank. Less of course if I drove it like the lunatic I was back in my 20's/30's :-) If your using the car everyday, then you will probably reduce range, what 1-2% a year? Sounds about right with 20% reduction in 10 years? That would irk me. I know it would. Illogical? Yes, but it would irk me :-)

That's just me of course - people would be perfectly right of course to use a V2H everyday.

unkel

https://www.boards.ie/discussion/comment/119790910#Comment_119790910

Yes true (lithium ion, not lipo though), but most new EVs coming from China will have LiFePO4 batteries. Also you are overly pessimistic about the life of a lithium ion battery. 1200 cycles does not equal one cycle a day, so a life of just 4-5 years. This cycle figure is down to typically 10% from near full and then at the end of the cycle life, the battery typically still has 70-80% of the original capacity. With average Irish driving mileage this gives a life of about a week per one cycle. Also a home in Ireland uses about 10kWh per day, so even if you got all of that out of the car with say a 60kWh battery, you'd only have a bit over a cycle per week from V2H, both will barely make a dent in the life of the battery really

the_amazing_raisin

https://www.boards.ie/discussion/comment/119790992#Comment_119790992

I don't think you'd be looking at 20% over 10 years from V2H, that would be fairly outrageous

I mean, the old Leafs which are 10 years old now had a worse battery chemistry and almost no battery care and they're only around the 20% degradation mark.

Newer cars have much better battery management, so I wouldn't be concerned about that.

They also generally have controls that won't let you discharge the battery below a certain amount, so unless you're doing 500km per day then range shouldn't be an issue

The other thing to remember is that the buffers on EV batteries are massive. The ID.4 for example has an 82kWh gross capacity, but only 77kWh is available (in fact it's more like 72kWh, the battery reads 0% when there's a few kWh left)

These buffers help absorb any degradation during the lifetime of the battery

You will see degradation, but I still think that 90% of it would be from actually driving the car rather than from using it as a house battery

10-10-20

https://www.boards.ie/discussion/comment/119777305#Comment_119777305

Back to the elephant hiding in the short grass - "I manually connect the HV battery of my car, via a precharge circuit, directly to my PV inverter.".

So how does that circuit look? Where do you link into the main battery DC (800v DC?) and what is a precharge circuit and how is this made safe?

I presume you're starting the vehicle's ignition and then taking a feed off somewhere, but I'm curious as to whether you're going battery DC -> AC 230v -> DC -> inverter MTTP-in to simulate a bank of cells? Or am I overthinking it?

bullit_dodger

You will see degradation, but I still think that 90% of it would be from actually driving the car rather than from using it as a house battery

True again mate - course that's a little dependent on how much you drive. With the WFH these days, I've had my current Beemer reporting that the battery needs charging as it can be 1-2 weeks before I fire it up. So if practically all of your usage of the battery is the house, then it's not going to be driving that's depleting it. Remember here that I'm 30-35Kwh/day in the house, so not your average consumer.

To me it makes sense to differentiate the two. If you need a battery for the house, get a battery for the house. A good 20Kwh DIY jobbie would see you right.

Again, all good well reasoned points, but if I have an EV (and the plan is to get a 4-series once they come out with a coupé)....I know I'll curse the day that the range drops from 500Km to 499Km.

CURSE THE DAY! LOL

graememk

https://www.boards.ie/discussion/comment/119791204#Comment_119791204

It's the red arrow, bmw conversion, 15ish kwh.

DC batteries in that is about 200v, straight into the inverter.

unkel

That's it. No need to start the car's ignition, I have the HV DC switch in the car off, connect resistor to pre charge the caps in the solar inverter, then switch HV DC on. Then the solar inverter thinks it's a string of solar panels producing power (in the dark 😁) and starts drawing the maximum current it can (11A), and the car's HV battery is drained into the home at about 2.2kW or if more than I need it goes automatically towards topping up my empty home attached battery

First time I tried it seriously, I got the guts of 10kWh into the house one of the very bad dark rainy days a week ago or so. Next day was a fine day and the car's battery was fully filled up again from the sun via the Zappi on eco plus mode

10-10-20

https://www.boards.ie/discussion/comment/119791563#Comment_119791563

Ok, quirky; very interesting solution there.

But you do have a suitable (<20A) breaker on that cable - as close to the battery terminals as possible, right?

unkel

Yes, fuse on the normal HV connection from battery to the car's charger (I borrow this connection for the V2H / have made the charger detachable) and fuse on the pre-charge circuit

the_amazing_raisin

https://www.boards.ie/discussion/comment/119791563#Comment_119791563

That is hilarious, and genius 😂

I was assuming you'd gotten a high power dc-dc converter to convert the HV battery down to 48V, but using the MPPT would work as well

I've seen some 450V MPPTs around, so you could in theory do the same with the Tesla if you were willing to get your hands dirty 😁

the_amazing_raisin

Has anyone bought cells from NKON?

https://eu.nkon.nl/rechargeable/lifepo4/prismatisch/eve-lf280-prismatic-280ah-280a-lifepo4.html

They're a Dutch company form the looks of it. Prices for EVE 280Ah cells are good, almost too good, better than PWOD almost

However, they seem to have good reviews and a lot of them seem genuine, so either they're fairly legit or the review bots have gotten more sophisticated (I'd believe either at this stage)

unkel

Did you see the expected shipping date? 😂 You might have them in March...

unkel

https://www.boards.ie/discussion/comment/119793145#Comment_119793145

Wasn't my idea to use the PV inverter, so I'm not the genius here!

I was pretty happy though that I had a pair of MC4 parallel connectors lying about so I thought I'd share one MPPT between a solar string and the V2H. Might as well as I'd never use the V2H during the day, just at night when there is zero PV output. I also happened to have a perfect length couple of MC4 cables that I had terminated into an XT60 connector (I use those for everything) and I had just made the car's on board charger mobile with the same connector. So it all came together perfectly and the V2H setup didn't cost me a cent. Now that was the part that I enjoyed most 😁

the_amazing_raisin

https://www.boards.ie/discussion/comment/119793235#Comment_119793235

Well, I don't need them urgently, and if it saves a few hundred and I've an EU based distributor to harass when there's something wrong then it seems like a good deal

My guess is they're getting pre-orders in so they can order in bulk and get a discount that way. Seems like a smart way to doing things

unkel

If you've ever seen an aluminium cell like the EVEs up close and a plastic CALB one, you'd probably bite the bullet and spend the few hundred quid extra on the CALBS. These yokes are incredibly sturdy.

But yeah, EU distributor who you pay (with your card) is a good idea. That said, of all the problems I have ever had with parts from AliExpress, they have always paid up in full. AliExpress tends to side with the customer, not the supplier. And because of that, they keep getting me back over for more and more like a proper addict 😁

graememk

https://www.boards.ie/discussion/comment/119793145#Comment_119793145

The solis can work an mppt up to 520v

Not that I'd be tapping into my Niro! 😂