newb thread?

CrankyCoder

CrankyCoder

Member
Joined
Mar 11, 2017
Messages
95
I am pretty new to this. I have probably watched youtube videos and read about stuff alot of you are doing.

Like I said I am new to this. So I figured I would post about what I am trying to do to start down this road, what I have, what my first goals are, ect. I am very open to feedback/suggestions/guidance

Right now I have 61 cells I have recovered (I know, it's tiny). All have 1900mah+

My first goal is to build a 12v pack. This is to run a 12v water pump. (baby steps)

I was thinking of trying to do the 12v packs with 80 cells each, but i am not opposed to doing smaller packs. I figure whatever size I start with I will try to use as I grow the capacity later with additional packs.

Where I am kind of hesitant right now and could use some feedback is the fusing. I like the idea of fuse wire per cell. But not quite sure what configuration I should go with and what kind of fuse to use. Should I fuse each individual 18650? or just each series?

If there is a "hey newb, start here thread" let me know!

Thanks All.
 
Hey!

I would go with 3s. And the number of cells totally depends on your application and what you have.
I have made this video:

Its not 3s but its how i do my smaller packs that contain the outgoing voltage directly on 1 pack. You could apply this to your 3s setup as well.
 
It ultimately depends on your ending usage is going to be.

There are some things that just plain won't run with <11.5V (or thereabouts). You'll rapidly drop from 12.6V to under 12V with usage. Many devices and such will run on the 14V range easier.

DC devices are like AC devices in this since. If the voltage is too low, it will draw more current; which means you'll need heavier wire. If the voltage is sufficient, then it'll run with minimal current and be ok.

I personally would recommend the 14V version as it gives you the greatest stability and longest pack charge life.

If you have a 50Gallon drum with a 1/2" pipe draining it, it will take X amount of time. If you have 100Gallon drum with 1/2" pipe, it'll take 2X time. A 1/2" pipe is cheaper than 1" pipe; and easier to work with.




Ohh, and if you use an inverter, they really wanna work with 14V rather than 12V. A lot of them will actually cut off around 12V to keep from draining the battery behind bounce back.
 
Ah ok! That is helpful. The plan would be that this first pack would be the first in hopefully more that will eventually be my powerwall. An inverter is not in the plan for this first step but definitely long term. So it sounds like going to the 4s might be good.

Is 12v an ok goal here? I have seen some people do 24 and 48v systems, but I know that getting inverters for those voltages can be more expensive.
 
CrankyCoder said:
Ah ok! That is helpful. The plan would be that this first pack would be the first in hopefully more that will eventually be my powerwall. An inverter is not in the plan for this first step but definitely long term. So it sounds like going to the 4s might be good.

Is 12v an ok goal here? I have seen some people do 24 and 48v systems, but I know that getting inverters for those voltages can be more expensive.
Click to expand...

Choosing battery and inverter has more to do with required power. Drawing over 1000W from a 12V battery requires very large (expensive) conductors to handle the current. If you aren't running high-power loads -air conditioners,power tools, etc. - 12V could be a good fit. If you need more than 1000W output, 12V wiring and fuses will not be economical.

1000W might not be the top for 12V. 1000W / 10.5V = 95.2A. 10.5V is used as a fudgefactor, for derating - also the minimumvoltage for LeadAcid. But price a 95A DC fuse or breaker. You'll start to think differently about voltage.
 
Regarding 3s vs 4s. Its just important to check the equipment you are going to use.

And as the other said. If yo ugoing to draw higher current go as high voltage as you can. You save in the end...
 
Another thing to note, is if this will become part of the house setup, where you'll be using mostly AC loads, then you might want to consider 24V battery setup. That way you have 2 110V lines in the house. It's easier and more efficient to convert to 24V to 2x120 (240V) than to convert 12V to 2x120V. Not to mention the loss in heat and the need for heavier conductors.

Yes the inverters will be a bit pricer at 24V, but they will repay their costs through efficiency down the road. The 12V will create a lot of heat wasted; not as much as the 24V setup.

Personally, I'm going to build my system to be a 48V because the initial cost will be lower (except for the inverter), and the wiring will be easier to work with; both charging and using.
 
CrankyCoder said:
thanks skyfridge!

definitely no need for heavy loads right now. But will definitely keep that in mind down the road. When you do need to go to that kind of wattage do you recommend going 24/48?
Click to expand...

There is a rule-of-thumb equation for inverter sizing:
V/6*C, where V is the battery voltage and C is the amphour capacity. I'm not sure if the constant 6 is different for 12V, 24V, etc., and I don't recall where I found it.

It comes down to cost analysis. Get out the spreadsheet, and figure out what it would cost for wiring, fuses, breakers, terminals and other hardware and equipment. The costhe comparison is the bottom line for making that decision.

Also, the equation might be more specific to lead acid. I don't know for sure, but it can probably be used for batteries in general, as a rule of thumb.
 
And we all know that Thumbs Rule!! Because without them, we couldn't work on our powerwalls :p
 
Got it!

For the first pack im going to stick with the 12v.

any recommendations on the battery holders? I am not opposed to printing them since I already have a 3dprinter and LOVE to find excuses to use it.

I had been looking at Paul Kennetts stuff he designed
http://www.thingiverse.com/thing:1729730
and
http://www.thingiverse.com/thing:2076195
since I already have those little volt meters.

I also like the 4x20 setup Peter Mathews does. Any suggestions?

Korishan said:
And we all know that Thumbs Rule!! Because without them, we couldn't work on our powerwalls :p
Click to expand...

Agreed. I like my thumbs!
 
I would go with the 5*4 holders and buy them, But I dont have any 3d-printer :)
 
You must log in or register to reply here.
Back
Top