Mark's 12v powerwall

Mark Daniel Olsen

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Joined
Jun 12, 2017
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18
So i saw tesla's powerwall and thought that i could help my dad in his offside garden where he only has a gas generator to power his little house and machinery.
I pitched the idea and he liked it so the plan is:

Build a solar powered battery as cheap as possible (while not burning the house down)
He wants a 10 amp circuit inside the house to power phone chargers, lights etc. and something that could charge small diy EV's like a garden tractor, later if this is successfull. the amp and volt of that depends on what connector and charger i can get at the time of creation.

his is in the garden about 8 months a year where he uses electricity about 6 hours a week, so the capacity dont exactly need to be big right now. but because of the small roof (the house is only 6m2) it should be capeable of getting power enough between each use and store it.

He has no idea of anything about electronic but the basics about changing a socket, (which we have to add)

So currently me, my dad and his friends are scavenging our local trash site to get as many laptop batteries as we can, and from our experiance they are often fine batteries, just the computer had been trashed by the owner.

So here is the small amount of 18650's which we have gotten, and my friends dad says he have some laptop batteries at his home.


image_mbbzjo.jpg



So what i want to know, how many volts should i make the system, currently i'm thinking about 12, 24 or 48. the capacity can be changes at any time because we are going to mount the wall outside the house (in dry conditions)
 
Welcome!

If he only going to power low voltage devices like phones and other it might be good to actually go for 12V based system. Batteries can be either 12/24/48 but it will require adapters if so.
You will save energy compare to having any AC inverter going 24/7. if so only use that in need.
For lights use leds that work with the Voltage of the battery :)
 
For phone chargers, laptop, etc, you can use buck converters for dc/dc conversion. it's more efficient as you don't need to run an inverter to convert your 12/24/48v to dc and have to phone/laptop charger converting it 5 or 19v dc.
Or as daromer said use 12v system and use car adapters who are working with 12v input.

You can even charge you garden tractor's 12v battery with dc to dc charger but you need a >12v battery or a voltage step up converter.
 
sounds like i should be using 12v then. thanks for the help :)

I think i am gonna wire 4 cell's in series and make 12v outlets instead of the 240v my dad and i have talked about. for the easy of it, and wire a single 220 from the car inverter we have lying around if he need that for something.
 
Just beware of that 12v need tp carry some more current for same watt so you have thick enough wires and dont forget fuses and you are good to go :)
 
So from the Danish name Olsen, and Offside garden = Kolonihavehus i take it you are Danish?

If so please do tell about your results sourcing batteries for reuse :)

Note: I'm just looking because I found the site and find it an interesting concept, but I am not planning to build anything :rolleyes:

Regards
Hanssing
 
I talked with my dad about the 12v packs and he liked the idea of how big it could be and said he wanted the packs to be hidden behind a thick old picture frame with some cardboard printed picture in the front.

i tried to lay all the batteries we have collected (still not tested) 4x10, (+ - + - x10) and said it could be that thin and now he is looking for a frame so we can have the batteries inside the house instead.


image_bqvkon.jpg


i actually forgot about the higher amp so thanks for the reminder :) i think i want to keep the 10a limit, and the fuses are easy to come by so that is perfect.

Quick tip for those who did not know, (i figured out while measuring) 18650 batteries have their dimensions in their name, 18mm for the diameter and 650mm for their height :)
 
I am setting up my "power wall" for my RV to power lights and fans (low current). I have 4 solar panels that I am going to run in 2 sets of 2 so 2s 2p. they are 21V solar panels so 42V to the charge controller then to a 7S bank. The Charge controller I was going to use died on me so I am looking at the MPT-7210A to replace it and get MPPT features. Then from the Power Wall which will be 21-29V step down to 12V with a buck converter.
 
With 10A limit and 12V it is 120W max, maybe too low charge the ev garden tractor, even to use with other tools. It is a good idea to redo the installation with 12 bulbs and other stuff, you will save the cost of inverter, but maybe you can't find tools to work at 12 dc.

About the panel size and battery size you must calculate your needs, 120 cells of 2200 mAh in series of 3 are a battery of 12v (really 9v to 12.6) with 88 Amph +- 1Kwh.

So once you know what energy you want to store calculate the cells, and the energy to store depends of the days you want to have to ensure you won't run out of power with some cloudy days and at winter that there is less hours of sun.

So sum the comsumtion of the tools and ev, multiply by hours running a day, multiply by days to ensure and some will recommend the amount of cells, amount of panels if you says the place you live.

Regards
 
I live in denmark, i just want to have the power needed and happily alot more. as long as my dad can charge his phone and drill as it is now, he is happy.

about the 10a limit, i only want that inside the house, the outside amp limit is to be whatever is needed at the time of expansion. to electric everything. but for the time being he just want to stop the waste of gas to power a single thing (which uses a lot less power then generated). In theory, just for the saving there he could just use the generator to charge the packs and power the charger.

About the drill and other tools, i want to use the 12vdc -> 240vac inverter my dad have laying around. or take out the ac->dc converter inside the chargers and have a voltage regulator in between. but currently we are just focusing about the wall.

He have a single solar panel out there, but he don't know anything except it generates power for the aircondition which is not working. so next time i am out there, i will measure the voltage and amps it gives and try to see if it can be used.

But as long as there is space, there is space for expansion :D
 
If you're going to be running mostly 12V setups (and that would be 4s, not 3s), then to convert to 240V, I would recommend having 2 packs connected in series to get your 24V which is easier and less waste to convert to 240V.

And, with some diodes (or transistors of sufficient strength), you can have 2 packs that are connected in series and connected in parallel. The diodes just keep both circuits separate. But I would not do this without low blow fuses just in case something fails.

I'm guessing your lights are going to be LED's which are 12V. That's a great option as there are plenty of those available and cheap to come by without having to change anything to work with your setup.

Welcome to the World of Powerwalls! :)
 
Korishan said:
If you're going to be running mostly 12V setups (and that would be 4s, not 3s), then to convert to 240V, I would recommend having 2 packs connected in series to get your 24V which is easier and less waste to convert to 240V.

And, with some diodes (or transistors of sufficient strength), you can have 2 packs that are connected in series and connected in parallel. The diodes just keep both circuits separate. But I would not do this without low blow fuses just in case something fails.

I'm guessing your lights are going to be LED's which are 12V. That's a great option as there are plenty of those available and cheap to come by without having to change anything to work with your setup.

Welcome to the World of Powerwalls! :)

i would stay with the 12v for the conversion simple because, it is so rarely the 240vac would be needed. its for a coffee machine or something like that if we are inviting family/friends out there, which only happens monthly or so.

if we needed that power more often i would have considered 24v or 48v. but as it stands after the recommodation i think it is going to work out :)
 
Yeah go with 12V. There is also 12v coffee machines :D
 
So it's time for an update.

i finally got my cell holders and have tried to arrange 100 cells so my dad can see how big a pack could be. (4x5 packs)
we are currently waiting for the nickel wires and BMS we have ordered. so we can test it.


When he saw the small packs and i toldl him how it could be done we ended up making 1 big back of 100 cells, (4*25)
 
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