Solar Project

[Donald Bitterman]

I am putting together a solar/battery system.  My goals are to learn solar/battery systems better and to build a system that I would eventually build out to an off grid system using recycled resources at all steps feasable.  My electrical usage is low (avg 25/month electrical/10 gas per month through the year) so this is not a finacially viable project, but I'm still doing it for the learning, fun, and reliability when the grid is down (in CA so this happens increasingly frequently).

I am going with 18650s, but if I were starting anew I would just go with LiFeP cells but I am too far in it to back off now.

What I have assembled so far:

1.  ~1,800 18650 LiCoCl cells from tool packs, laptop batteries, etc. (~200 sorted for voltage bleeders, high internal resistance, capacitance, etc.).  ~5% are rejected

             all holders needed

              capacity tester/charger.

2. 1x Electrodacus SBMSO

3. 1x Electrodacus DSSR20 w// diversion

4. 1x DEXT16

5.  2 enclosures (surplus MCC Cabinets)

6.  1x Inverter, 1,100 W @ 24VDC->110 VAC (https://www.solar-electric.com/exxp24vol11w.html).  I am not sure if this will work with this system, but I have it for free.

Photo Links:

https://photos.app.goo.gl/H62SPHu9HSWasbtaA

System Overview

Solar Panels considering purchasing

mockup layout of electrodacus and inverter hardware

I have a few questions:

1.  Would the sunpower solar panels depicted above work for this application?  I see in the manual about cells on the PV panel, but I am not clear on what this actually means or how to determine this based on the part number, etc.  The voltage is 40Vmp/47.7Voc which I think meets the specs on page 4 of the manual

      If I can get these at 0.47/w is this a good dea;

2.  Is there a general consensus on the best make/model of shunt, breakers, etc.

3.  I am trying to figure out how to match the size of the battery vs the solar array.  An suggestions on this front.  This is me being a bit lazy and I need to do more research on this, but wanted to still put it out there to see what comes back.

[Dacian Todea]

Inverter seems top have a toggle switch on the front and if that is the case then it will work you just need to open and solder two wires in parallel to that switch to allow the SBMS0 to control ON/OFF the inverter.

PV panels will work but they are not the best choice as they are 72 cell panels. The DSSR20 can handle 3 of those panels in parallel.

I assume you will be building a 7s battery.

1. Those are old 72 cell panels made with 5" cells. For old panels the price seems a bit high but not sure about your location. Normally you will find new 60 cell panels for same price.

2. Any shunt will work but here is a link to some recommendation https://groups.google.com/g/electrodacus/c/ReL-z6vGFdw/m/vsmKm0grAQAJ

3. 0.2C is about the ideal ratio so for say a 200Ah (usable battery capacity) you will want 40A PV array.  But it will depended on you building the pack properly and those used cells are not the best option. They have the worse value possible. 

[Donald Bitterman]

Dacian,

Thank you very much, sorry for the delay.  I am still digesting your response and doing a bit more research.

1.  Solar cells:  It looks like there are some 60 cell panels available locally for less.  I am going to wrap up design prior to buying panels.  So far it has just been scrounging for what is free other than your gear, and the cell pack accessories.

2.  Shunt:  Thank you, I will get that ordered and enroute ASAP

3:  Batteries:  The 18650's are free, but the holders and fuses are not.  Time is a factor, let me digest this a bit.  I read your response from a year+ ago on second life storage.  buying LiFe batteries just seem so expensive /kw-hr, let me quantify it with cost including some reasonable number for time.  I am a bit stubborn so need a bit of time to get past the sunk cost already dumped into breaking packs and sorting so many 18650's.