Begginers Guide to Processing 18650 Cells | Cell Database


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Watson Expedition
#1
I'm still a few weeks out from starting my build, but I figured I'd go ahead and start up a thread since I took the first $ plunge today and bought my donor batteries, and I'm about to submit purchase for the trailer, as soon as we can agree on windows.  This project is now officially green-lit.

I am building a custom RV using an aluminum car hauler as a base unit.  The goal is to be a fully off-grid self-sustained energy setup.  Current plan is:
  • Nine Panasonic N330 solar panels for 2,970 watts of solar wired in 3p3s to keep the wire runs efficient (see below for a rough initial layout mockup).  2s would have been ok (ish) too, but would have prevented me from having the 9th panel.  1s would require wire too large with losses too high imo, unless I mounted the charge controller in the ceiling, which I don't intend to do
  • Battery pack configuration of 300p13s for a total of 3,900 cells.  At 2.2Ah per cell, this looks like 31,746Wh nominal.  These are new cells, purchased from alarmhookup on eBay:

    .jpg   ebay-LG-batteries.jpg (Size: 15.42 KB / Downloads: 207)
  • The 13s configuration is due to the DC air conditioner requirements.  It has a max voltage of 54v, which would be 4.15v per pack in a 13s configuration.  If I were to do 14s, the air conditioner would not run at the higher charge states
  • The least important draws shut off first:  44v for the air conditioner, 40v for the inverter, 35v for the 12v DC line for lights and so on.  At 3v per cell that would be 39v, so the inverter and 12V DC should almost never shut off unless I hit low voltage protection
The solar panels will almost totally cover the roof, so I won't be able to have any skylights, roof vents, or roof mounted air conditioning.  The mini-split will be mounted either on the tongue or on the bumper:
   
Jimlun and BlueSwordM like this post
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#2
This is quite a nice setup with minimum number of panels used... similar as what you have in mind. Just look at the generated current from the solar controller...

https://www.youtube.com/watch?v=edndBejb6FA
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#3
(08-15-2017, 11:59 PM)Dan Lim Wrote: This is quite a nice setup with minimum number of panels used... similar as what you have in mind.  Just look at the generated current from the solar controller...

https://www.youtube.com/watch?v=edndBejb6FA

Yeah that's interesting. I haven't picked a charge controller yet, but I was hoping my choice of a 48v battery bank would simplify my setup. It seems most everything is rated in amps, and 48v will run 1/4 the amps of a 12v setup. My gut was a Victron, but I've not made up my mind yet. I'm a bit worried that company's products are overpriced.
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#4
(08-16-2017, 12:16 AM)Travis Watson Wrote:
(08-15-2017, 11:59 PM)Dan Lim Wrote: This is quite a nice setup with minimum number of panels used... similar as what you have in mind.  Just look at the generated current from the solar controller...

https://www.youtube.com/watch?v=edndBejb6FA

Yeah that's interesting. I haven't picked a charge controller yet, but I was hoping my choice of a 48v battery bank would simplify my setup. It seems most everything is rated in amps, and 48v will run 1/4 the amps of a 12v setup. My gut was a Victron, but I've not made up my mind yet. I'm a bit worried that company's products are overpriced.

Sounds good.

Re the victron, I have their 12v 800va inverter, whilst I think their products are fine I do consider them overpriced.
Have you looked at the PCM60X, I have one of these and seems solid for the money
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#5
The panels I have will be 2,970 watts total, which at 48v would be 61.9A, a bit over that PCM60X.  Plus I'm going to shoot for a 3s3p config, which would be 210 open circuit volts coming from the panels (over the 150 rating on the PCM60X).

These high limits is why I was eyeing the SmartSolar MPPT 250/85.  I think the Midnite Solar Classic could fit the bill too, maybe an Outback?  Not sure... this is the area I know the least about so I still have a good chunk of research to do.

Thanks for the tip on the PCM60X!
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#6
(08-16-2017, 02:36 AM)Travis Watson Wrote: The panels I have will be 2,970 watts total, which at 48v would be 61.9A, a bit over that PCM60X.  Plus I'm going to shoot for a 3s3p config, which would be 210 open circuit volts coming from the panels (over the 150 rating on the PCM60X).

These high limits is why I was eyeing the SmartSolar MPPT 250/85.  I think the Midnite Solar Classic could fit the bill too, maybe an Outback?  Not sure... this is the area I know the least about so I still have a good chunk of research to do.

Thanks for the tip on the PCM60X!

Yes will too. Back to the drawing board
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#7
Based on reply on other forum post, parallel-first wiring will work well, but diodes are important.  I'm not sure the best solution for this, but I have found this diode with MC4 connectors:

http://www.win-solarllc.com/index.php?pa...Itemid=113

This seems like a very expensive solution.  With 1 per panel, that's almost $300 just for diodes!

I'll keep searching for alternatives, but knowing there's at least this option is good.
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#8
You can always make your own blocks. You just need to get large diodes and connect them in parallel (say, 2 or 3 of them) to share the loads. If you get ones big enough, then only 1 would need to be used.
Here's an example of a set: https://goo.gl/LdjLqN (eBay)
And not sure where you are, but here's one from the USA: https://goo.gl/sdb7xh (eBay)
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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#9
(08-21-2017, 03:49 AM)Korishan Wrote: You can always make your own blocks. You just need to get large diodes and connect them in parallel (say, 2 or 3 of them) to share the loads. If you get ones big enough, then only 1 would need to be used.
Here's an example of a set: https://goo.gl/LdjLqN  (eBay)
And not sure where you are, but here's one from the USA: https://goo.gl/sdb7xh  (eBay)

Gotcha, yeah I think the $$ on the one I linked was for the ease factor, MC4 connectors and all ready.  Just need to whip up some connector ends and housings and save a ton of $$.

If connecting this in line with the solar panels, what should the amperage rating be?  The Panasonic panel I'm looking at would have a current of around 6A, so the 10A rating could handle a single panel's output.  With a 3p3s configuration, would that mean there's a potential of two times the single panel amperage for feedback?  Seems like I'd need a 12A+ diode rating perhaps?

This looks promising: http://www.ebay.com/itm/20A-MC4-in-line-...Swsg9ZkZjM

I'm dense -- the current rating is the forward current rating. Still should probably be 3x the single panel rating, or 18A (for a situation where 2 out of 3 panels are shaded, if all 3 of a parallel string are shaded, there's no saving it unless I add in bypass diodes). So 20A would work well.

At this point... it's getting complicated perhaps trying to keep it all on a single charge controller. It might still be worth it, but maaayyybe not. I should investigate options for multiple charge controllers.
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#10
That inline one looks nice. Definitely a lot cheaper than that other one you posted.

Personally, if I was going to go that route with diodes on the panels, I'd go full out on it. So, there'd be bypass diodes on the panels for the shaded cells, and there'd be bypass diodes between the panels. That way you could get the most out of it as possible.

However, the one thing you really need to worry about when it comes to diodes is the forward voltage drop. Each diode in series will drop the voltage a certain amount. So, if you build these, you need to check the datasheet on the diodes so you can get the least amount of drop-out.
That's when you 'really' start to see if it's really worth the time, money, effort of doing it in the first place, or just put up with a little shading for short period and let the unit bounce back. Although, you will still need a certain amount of diodes regardless. It's a balancing act when you get to this level.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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