Duchess Powerwall build log (56k warning!)

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Duchess

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I am planning on building a powerwall to supplement power to my home during high peak times (15:00-20:00). I am going to pick up some solar panels to help charge during the day and use grid power during non peak times to charge the powerwall.

I picked up some modem batteries a little bit ago when they were on sale at batteryhookup.com. Lets start with these:

1628363989695.png



This should keep me busy for a while. Do you think I will have enough to power my house or should I get a couple more packs?

-Duchess
 

floydR

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If the ones in photo are all you have. 6p x 2600mAh 15Ah@25.2v= .378kWh. You need more cells. A lot more. Probably on the order of 1000 more cells. 7s140p(24v) or 14s70p(48v) plus you extras cells, enough to account for bad cells and an extra 140p/70p pack. That would give you approximately 9kWh of storage.
Start by estimating your usage from 3pm to 8pm Better yet measure your usage.
Later floyd
 
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OffGridInTheCity

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So more cells then..
Yes Sir - agree with @floydR.

Let's say you're house averages 2000watts per hour x 5 hours of your high-peak window. To do this you'll (roughly) need a battery that can supply 10,000wh of power (5 hours * 2000watts per hour).

For battery -> inverter + overall system losses let's use 15%. Also you don't want to do 100% DOD (depth of discharge) so add another 20% so you can stay at 80% DOD. This puts us at a battery bank around 15,000kwh.

OK then, a 15,000kwh battery. That's a 48v @ 288ah +/- a bit. If your cells are 2000mah each, then you'll need 144p * 14s = 2,016 cells. If you did 100ah LifePo4 cells, you would need 16s3p for 48v @300ah = 48 of them.

Now - if you find your consumption is 1000watts per hour x 5 hours - you can just cut everything in 1/2. :)
 

italianuser

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Do you think I will have enough to power my house or should I get a couple more packs?

How @floydR and OGITC say you must know how much power your house needs. Only after knowing that number you can say "ok, a 2KWh battery" or "a 4KWh battery".

To measure how much your house is consuming you could mount an AC energy meter, I bought two of these:

1628509991697.png


https://www.aliexpress.com/item/4000011007083.html

My house uses on average 230-240KWh per month during winter, spring and autumn. That's about 8KWh per day. In summer I use around 30% more because of air conditioners.

Now, after knowing this first basic number (average current usage) I can go and see what peaks of current I have during the day (peak current usage). When the oven is on and maybe some other big load I reach peaks of 3.3KWh for short periods (from 1' to 30-40').

From here you can calculate a possible battery size to power your house and size panels, too.
 

Duchess

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So it looks like I am running around 60amps during the day on average for day to day stuff and peaked at around 176amps this weekend when I was doing stuff around the house. I only have about 2/3rds of the circuits being monitored right now as I am maxed out at 16 CT's with my current monitoring.
 

OffGridInTheCity

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So it looks like I am running around 60amps during the day on average for day to day stuff and peaked at around 176amps this weekend when I was doing stuff around the house. I only have about 2/3rds of the circuits being monitored right now as I am maxed out at 16 CT's with my current monitoring.
60amps at what voltage? 120v? 240v? BTW - that's a HUGE amount of power. I have a large home with many frivolous electrical 'things' running and I'm more in the range of 20a @ 240 as an average.
Note: I don't make the comment above to be critical, but rather to double-check what you might need to give you solid advice. Maybe you could explain in more detail how you go the 60a number.

Let's start with 60a @ 240v.....
60amps * 240v = 14,400w. 14,400w * 5hours = 72,000wh (or 72kwh). For that - your going to need the 2000cells (estimate above) * 7. In other words - in the ballpark of 14,000cells at 2000mah/cell. That's a TON of work to process that many 18650 and would lead to a strong recommendation to go with larger cells such as the 280ah LifePo4 cells @hbpowerwall referenced in this thread - https://secondlifestorage.com/index...et-is-the-best-value-per-ah.11151/#post-77887. This would be on the order of 7 * 16 of them = 112cells... much saner number of cells to process/hookup :)

60a @ 120v...
60amps * 120v = 7,200w. 7,200w * 5hours = 36,000wh (or 36kwh). So it's 1/2 of the above.
 
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Wolf

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So it looks like I am running around 60amps during the day
60amps * 240v = 14,400w. 14,400w * 5hours = 72,000wh (or 72kwh).
My lord @Duchess:whistle: what kind of plant farm are you running? Or maybe a crypto farm?
With every electrical device turned on including my vacuum cleaner, (8) laptops, coffee pot, microwave, AC, and hot tub there is no way I would be pulling 60 Amps especially at 240V. Maybe if I plugged in my MIG welder and ran that at 100% duty cycle and with everything on in the house.
I would bypass 7s and go straight to 14s. Wire size alone for a 60A 240V draw on a 24V inverter is 600A. Thats AWG 400 MCM THHN Copper Wire 0.85" diameter. Even still at 48V you are still taking 300A and AWG 300 MCM Copper at 0.63" diameter.
I think it's time to revisit the BMS and go with 14s. Also you may want to install some energy efficient appliances or maybe turn off a lightswitch or 2.;)
Wolf
 

Duchess

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60amps at what voltage? 120v? 240v? BTW - that's a HUGE amount of power. I have a large home with many frivolous electrical 'things' running and I'm more in the range of 20a @ 240 as an average.
Note: I don't make the comment above to be critical, but rather to double-check what you might need to give you solid advice. Maybe you could explain in more detail how you go the 60a number.
120v. I am getting my readings from an emporia vue 2? So far I have not been happy with it. :|
No farm or anything. My pool pumps and my AC units make up most of the 60amps base load and then add a water heater, clothes dryer and an oven to push that number up. +100amps at least.
I know I am not going to be able to run everything off of the powerwall, especially during the peak summer days but slowly start offsetting that base load, selectively powering things as I grow in battery capacity. Especially the non inductive loads that are easy.
 

Duchess

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I picked up a dozen of those LiitoKola Lii-500's off Amazon on prime day on sale but wow what a piece of crap those are. I ended up tossing them in the trash since I they are so worthless that I didnt even want to bother returning them. I wanted to smash them into small pieces. Wow I cant believe how horrible those are and would be impossible to be able to continuously test batteries with them.
I have a few ZanFlare units on the way to see I can actually work with those, I have a couple now and seem to work great without going with a opus or a megacellcharger for now.
 

italianuser

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Oh no, what didn't work for you with LiitoKalas? I only have LiitoKalas o_O ok we an agree they are entry level but they do the job of charging and capacity checking the cells...
 

Wolf

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120v. I am getting my readings from an emporia vue 2? So far I have not been happy with it. :|
No farm or anything. My pool pumps and my AC units make up most of the 60amps base load and then add a water heater, clothes dryer and an oven to push that number up. +100amps at least.
OK I am now officially confused? :confused:
120V for pool pumps and AC? Water Heater, Clothes Dryer, and Oven at 120V? That doesn't seem right. Dryers, ovens and water heaters are usually 240V. I am also assuming the same for the pool pumps. The AC I can see at 120 especially if they are window units. But with a pool I assume you have the financial means for a heat pump/ HVAC system, and I'm pretty sure that's 240V.

I have a few ZanFlare units on the way to see I can actually work with those, I have a couple now and seem to work great without going with a opus or a megacellcharger for now.
I have had pretty much all the commercially available charger/analyzers. Zanflare, LiitoKala, Foxnovo, Opus, Skyrc, Vapecell etc.
I liked the (3) LiitoKala and (3) Zanflare so much I gave them away, poor soul, I even paid the shipping. If you are going to process a vast number of cells get the Opus do the fan mod to it/them. If you have the means the SKYRC MC3000 is a very good unit, or get a Megacellcharger. Get a RC3563 or an YR1035+ IR meter with the cell holder to prequalify the cells SOH and you will never look back. Don't waste your time on cheap chargers/analyzers you will only be disappointed.
Wolf
 

Duchess

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Oh no, what didn't work for you with LiitoKalas?

Maybe they would be okay for charging but doing any capacity testing is a joke. you would have to wait until all the cells are done testing all at once before swapping out cells. With the Zanflare ones I can can swap in cells as needed as they complete.

Duchess
 

Duchess

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120V for pool pumps and AC? Water Heater, Clothes Dryer, and Oven at 120V? That doesn't seem right. Dryers, ovens and water heaters are usually 240V. I am also assuming the same for the pool pumps. The AC I can see at 120 especially if they are window units. But with a pool I assume you have the financial means for a heat pump/ HVAC system, and I'm pretty sure that's 240V.
I have 120v split phase service to the house. I have a pool and a spa that are heated but by gas but no gas service to the house. Everything else is 120v+120v
 

Wolf

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I have 120v split phase service
Either you are toying with me, which is OK, or you live in these countries as they are the only ones providing 120V single as a residential service.
If in fact you do then you must have 2 seperate services.
I also have never heard of a 120V split phase which would mean you are splitting 120V into 2 phases and that would be 60V on L1 and L2.
1628788061210.png

Everything else is 120v+120v
So if in fact you live in the northern hemisphere i.e. USA or Canada then you would have 240 Split phase with L1 at 120V and L2 at 120V.
Not trying to be a stickler here but.........
Wolf
 

italianuser

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Maybe they would be okay for charging but doing any capacity testing is a joke. you would have to wait until all the cells are done testing all at once before swapping out cells. With the Zanflare ones I can can swap in cells as needed as they complete.

Duchess
:rolleyes: You can swap single cells as soon as they finish the capacity test (NOR test), without waiting for the other cells. No need to wait for the other cells to complete. That's with Liitokala 500. I know it's an entry level charger but it did a great job testing my 1200 cells. As said in many posts Liitokala is no good for IR testing and discharge is max. 0.5A. A part from that I think it's a good choice for beginners (me!) with a low budget.
 

Duchess

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:rolleyes: You can swap single cells as soon as they finish the capacity test (NOR test), without waiting for the other cells. No need to wait for the other cells to complete. That's with Liitokala 500. I know it's an entry level charger but it did a great job testing my 1200 cells. As said in many posts Liitokala is no good for IR testing and discharge is max. 0.5A. A part from that I think it's a good choice for beginners (me!) with a low budget.
Well sure you can swap out single cells but that would change the parameters of the the other cells when doing so! What a stupid design. If you swap out 1 cell then you have to reset the test (NOR test) for the rest of the cells and start all over with the rest of the cells!! So its either test 1 cell at a time or wait for all 4 to get done. That's dumb.
 
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