Took the Solar Plunge

  • Bought myself 4 Deep Cycle 12V batteries 29DC from Wallyworld for Christmas as a seed for my solar bug.
    So now i bought a cheap solar kit with Poly, instead of Mono(First Mistake, but i like the panel size better)

    RENOGY 100 Watt 100w Polycrystalline KIT with controller and MC4 cables.

    I have no idea what i am powering with it but i took the plunge.
    Right now i have .6 amps x 12hrs  pulling from LV Yard Lights i bought from HomeDepot. I added some electronics to the mix and have an Chinese 160W DC12V-to60V converter for a netgear POE router.

    I am running on batteries while i figure out my total load and test out the solar panel and controller kit.
    Totally backwards I know!!!
    What would be the best battery arrangement for -4 batteries-? -In series- for 48V or parallel@12V or mixed for 24V?

    My depth of discharge is minimal now and i have a battery tender on them until I can mount a panel outside.
    Should I spring for another panel as well??

    What is the definitive way to tell actual Depth of Discharge? Is it voltage?

    I know with cold weather the charts call for severely reduced battery capacity at these extremely cold temperatures??


  • Yeah - With batteries, look at the voltage with no load on it.

    So lets say you have been running lights for an hour.  Soon after turning off the batteries, check the voltage.

    So, something like this:

    10.5 is considered a deep 100% discharge.  With most batteries, like what you bought 20% regularly is about all you can get away with.

    The odds that you got a TRUE deep cycle battery at walmart are pretty slim.

    After you are done killing them, take a look at exide deep cycle batteries (spiral cell)

    You can go 50% discharge on those pretty regularly without hurting them.  This will destroy your walmart batteries.

    If you want bigger, look into rolls batteries.

    Newer Polycrystalline cells are really not bad.  No problems there.

    Charge controller is really super important though.

    What kind of charge controller are you using?

    48v is best.  Higher voltage from the panels means you can run smaller wires to the charge controller without much loss.

    More importantly, you can run MUCH thinner terminals from the battery to the inverter without setting your wires on fire (-:

    Mine is all 12V unfortunately but it was required.  My terminals are all 0 gauge welding terminals basically.

    Even with that they have to be short - 1.5 feet max for me between the battery and the inverter.

    If you can run 48v on the panels, charger and inverter, thats best.

  • my $0.02

    When we build remote sites we always look at powering devices direct with no inverters.  Use the KISS concept. Keep it simple stupid.

    If you have multiple devices that power directly off of 12vdc then stay with 12volts. In our case we have items that we can order with 24 or -48vdc and other devices that do 12 to 24vdc. So we order them all 24v and do it that way.

    Bigger wire costs more but in the long run you will have less to worry about. So don't let wire gauge dictate your decision if your serious.

    Think about efficiency first. The more inverters or regulators you have the faster the battery bank will drain.

    Regulators (to regulate from 24 down to 12) are better than inverters (12 up to 24 or 48 or 120vac.)  24v to 12vdc regulators will generally work down to 17 or 18 volts before having issues. So you can really kill off the battery before losing the 12v supply. Not so good for the battery bank but more time to fire up the generator.

    Fun project!  Good Luck!!  :)

  • The requirement to power all my things directly off 12v is why mine is 12v also.

    However, the second 120v or 210v at high wattage is a requirement, 48v is far superior to 12v.

    So, yeah.  Depends on your needs.

    Most small routers can be powered direct DC straight off the battery if thats all you need.

    This eliminates the need for inverter at all.

    Mine was for backup power for whatever…  Anything.

    I could pull direct DC at 12 or 120v at 3000w.

    My first one was built for camping.  I used it for lighting, running cell phones and laptops and for cooking and making coffee mostly.

    If I were going to power a cabin, I'd definitely go with 48 volts on the DC side and 120v on the AC side in the USA.

    Even with wires as thick as my forearm, the line loss over a long run is tremendous - keep that in mind.

    With 12v systems you really want the panels virtually touching the batteries and the inverter as well if it can be arranged.

    Its not so much about the cost as about the voltage drop at even short distances with 12v systems.

  • Netgate Administrator

    A friend of mine lives off grid on a boat and over a few years we spent some time experimenting with various batteries, solar panels, wind generators etc. A lot of what we learned about solar and wind energy doesn't really apply if you're not in the UK so I'll not talk about that. Two things though:

    1. By far the best way to know what your batteries are doing is to use a proper battery monitor that counts Ah in and out and accounts for charge losses, temperature etc. They are much cheaper than they used to be and tell you WAY more than off-load voltage.

    2. It is pointless, and in fact worse, to have more battery capacity than you can comfortably charge.
    This is really important. We started off with a set off used fork lift batteries with a combined capacity of ~2000Ah at 12V. Unfortunately there was not a chance of ever putting in a equalising charge at that capacity with the panels we had. Consequently the cells in the battery became progressively more and more unequally charged until some start sulphating and eventually die. This produces an interesting cascade of failing batteries which is not fun and expensive!

    It seems surprisingly hard to find out but it seems your batteries are 125Ah each yes? So you have a 500Ah battery bank but with a 100W panel a maximum charge rate of ~8A. I think you could run into the same issue.  ;)

    Phil is the man to ask about this as he's out in Nepal where many of the installations he has are solar/battery powered. Though Kejianshi also has experience here.


  • I didn't even look those batteries up - They came from walmart which is pretty much all I needed to know…

    These also work well if you need something you can easily order from napa or auto zone:

    But having an actual solar battery is even better:

    Any of the batteries listed above and especially the last one will allow serious daily cycling for years.

    Or...  You can buy a new bank of batteries from walmart every 6 months.

  • Thanks All for Reply's

    So i found this supercheap battery gauge that might work for a small battery bank. S30 dollars ebay. Over 10A load needs shunt. fuel gauge battery monitor/Battery Fuel Gauge SVEB1 for 12V-72V.html

    pdf shows you can set the AMP/HR rate of the batteries.

    My batteries:
    Yes 125ah@20hr each i assume. They are big so AH size doesn't surprise me. I had an 27DC in prior test was 100ah.
    So 4x=500ah at 12V

    Obviously these are walmart batteries and for boats but lead is lead and they got it. If they last 2 years i will be happy.
    I tried going to the local industrial fleet battery dealer(Intestate) and they were clueless. It really blew me away they had no idea what a T105 was and they sell Trojans. I just went the cheap route for learning.

    What about distance. My panels are going to be 70ft. from my batteries. Is this terrible. Where should i put the charge controller, dead in the middle or closer to the solar panels in my cable run? The MC4 cables are 10gauge and seem healthy for 5A from panel max. I see a pigtail for mc4 to branch or Y i suppose for a second panel.. The controller is junky but OK for starter. Can do 12V or 24V.
    Obviously I would like a forklift battery, or RollsSurrette but my yard is shady and I doubt this will go far…Another hobby.

  • Netgate Administrator

    That's the sort of meter I'm talking about. I can't see a price there.
    The charge controller needs to be as close to the batteries as possible unless it has seperate measurement wires to take cable loss into account.
    Are those cable size figures in AWG?


  • Yes sorry 10AWG maybe a 20 foot lead. May get the y-splitter since MC4 is standard. I do see different gauges MC4  like 12AWG but on ebay some are hard to tell.

    Here is the meter no housing

    I think this in the description is quite amusing:

    Percentage of capacity and totem pole

  • Here is the bigger step up circuit i bought for 12V to 48:

    Terminal Blocks on ebay=2 dollars
    Terminal Blocks at Northern Hardware=12 dollars

  • kejianshi: I really appreciate your reply. I posted late about distance. So 70ft. Would see extreme loss that is what i needed to (not)hear. I could mount the batteries on my temp lawn cart to make it heavier but winters are tuff -if i am reading that battery chart correctly. Like 40 percent off the top on really cold nights. So my shed was an alternative but at a distance.

    I was actually thinking of using a lawn/custom pvc cart to temp mount the panels to determine best location for a pole mount. Probably 2 panels. I am fabbing up a mount as they want premium money for steel parts and i am a stainless guy.

  • For small installs that get exposed to weather, I like these:

    Morningstar SunSaver SS-6L-12V 6A, 12V Solar Charge Controller w/LVD (Gen3)

    Its a pulse width modulated charge controller.  I also has a built in conditioning circuit.  It won't raise the voltage above 14.2 volts or so.
    I'm not sure what type of controller you are using but if it goes through the same sort of charge cycle as most of them and includes a desulfication (sp) phase, it will make a mess of your AGM battery in short order.  Its better to use a rapid RF pulse for that.  I've had great luck with these.

    The morningstar MPPT controllers are also great.

    As for you distance problem, its best to collocate the batteries and panels (or close as possible).  How cold will it be getting?  Or how hot?

    Also, lead isn't lead…  Quick talk about differences.
    First lead purity - The solar type are super pure lead and the batteries are designed with low internal resistance so thay can accept charge at a very high rate, discharge at a high rate.
    Lead plate composition - Solar batteries plates are smooth and can endure very very deep discharge often.  Starting batteries are not smooth.  They have spongy like surface and are really only meant to be discharged 5% or so.  Most deep cycle batteries you get at a place like walmart are not very smooth plates and won't take many discharges especially beyond 50%

    Lastly, plate thickness.  True quality deep cycle batteries have very super thick hard plates.  This keeps the material from shedding away from the plates during deep cycling.  So the difference here is the quality batteries can endure greater than 50% discharges for years and years (thousands of discharges) while a average department store deep cycle battery might endure 50 or 60 deep discharges at most.  So later do keep that in mind.

    With the batteries you have, I'd recommend not testing them too much.  I'd try to keep the cycling light.  Say 20% or less which might be easy enough since you have a pretty large bank.

    I have not tested LIFEPO4 much but the thing I like about those is the cycle life and that they can be cycled to nearly 100% without killing them.
    The thing I don't like about them is the charge control and discharge control mechanisms that you need with the battery.  It limits how many AMPS I can pull off the battery safely and the rate I can charge at.

    As for the batteries and COLD weather, this is much easier problem that very hot weather.
    When you are charging batteries, they heat a bit, so if you put an insulation jacket on the batteries they should be fine.  This is especially true for AGM.  They do well in cold weather when insulated.  If you throw up 3 more solar panels, you will have enough for your batteries.

    I charge at 10 amps but My batteries can take as much as 50amps per each 50AH battery.  Exide batteries can really take a beating.  In some cases I have 4x as much solar panel as you charging 1/8 the battery.  I do prefer to have a very large battery bank when possible though because it prevents you from having to deeply discharge the cells.

  • What about the backside's of the panel?? I work on boats and that open back just don't cut it. Was thinking of enclosing it with some sheetmetal to help reduce the "Sail effect" That 1.5" Lip is unsat design in my opinion. The cheap panels i got really need angle re-enforcements in corners for me to feel confident about them withstanding 100mph winds..Flimsy lightweight aluminum it seems. I may do some bracing as well where the pole mount meets the back.
    Is tracking worth it??

  • No tracking.  I wouldn't even say "tracking" and "100 MPH wind" in the same sentence.

    I'd say mount the panels either flush with some other sturdy rigid surface or box them in so that wind cant get under them to create lift.

    Where EXACTLY are you mounting the panels and why EXACTLY can't the batteries be mounted very close to them?

    I've built south facing solar generators that are mounted on a wooden "wedge" of about 26 degrees sitting directly on the ground with the batteries under the panel and the whole box anchored for exactly same reasons - To keep the wind from carrying it away, to keep all components close and make cleaning snow off the panels easy.

    Generally there is no advantage in raising the panels other than to keep clear of shadows if they exist or to avoid flooding damage.

    Elaborating on the length of wire run.  The high voltage AC side can be long.  70 feet is ok.  Only the low volt DC wiring must be kept short.

  • Yea anything is possible but you are correct. Stabilizing that weight would need a mighty positioner at 100mph. Truthfully i thought about a ground hugger but i dunno if i like it. I may mount more equipment on the pole. And yes i could build the battery boxes right onboard for stability. I liked the variable angle is why i chose the pole mount. I am not married to it. I was planning on mounting some other gear onboard like a weather station(weewx) and antennas.

  • Weather stations can still be mounted on poles even if the solar, battery and inverter are on the ground.

    People mount solar panels in the air all the time and get away with it, but 100mph wind….  Sounds like recipe for disaster.

    So, I'm a tiny bit confused.  Is this going to be on a boat or a yard?

  • Smallish Yard just a home project…
    I appreciate your system sizing advice. So you saying roughly one 12V-125ah battery per -100W/5A max@17V/12V panel? or 4 panels for 500ah of battery? All roughly.
    I don't plan on inverters. Just DC loads... I seriously eyeballed the 200W class panels by the big names. I just want to experiment for now.
    I may just use an old lawnmower deck for temp mounting of batteries and panel.
    And i just pulled the 100mph figure out of the air. My point was i want something sturdy and not blowing away at 70mph gust.
    Thanks for the great advice.

  • My cousin did a tracking unit that only utilizes freon gas and properly placed "exposure tubes" and air shocks from a vehicle. Got it from "Popular Mechanics" magazine from the 70's  He uses it to this day and for the last 25 years.

    It supplies 30 amps in the top of the day and supplied their family of 4 off grid all this time till the kids moved out.

    Luckily he messed up the gas and the panel makes it way back to the east overnight and is waiting for the sun first thing.  Id love to find that article.

    He is on top of the hill and the wind has never been an issue.  I suppose he got lucky.

    Deka makes terrific solar batteries as well.

  • You have to measure the current coming off your panels to know what you are getting.

    A 100w panel in full sun at the equator will probably get you 100w or 8 hours or so.

    In some northern place, it may only put out 30 or 50 watts and may not get many hours of sun.

    So, you have to figure, up north you will need 2x the panel (at least) as panel advertising my lead you to believe.

    You only get a few hours of sunlight - So, lets say for instance its 4 hours average for your place.

    So you discharge 24/7 but only charge for 4.  so your charge rate needs to be 6x higher than your average load.

    Not only that you vane to compensate for load.  A great lead acid battery only stores about 60% of what you put into it.  40% may be lost.

    So you have to take your original calculation of 6x the load and multiply by x 2.

    So, if you average load was 10w you would need about 120w input during your 4 hours of sun to keep things working well.

    So yeah - More panels.

  • Deka  - I've heard good things but have never used them.  No experience with those.

    Good thing is I'm pretty sure what you have, if you add abit more solar panel, will easily run a small 10w pfsense (-:

    (The above comment is a blatant attempt to prevent deletion of thread due to irrelevance to pfsense boards)

  • Thanks for every-ones advice. I'm sure the Renogy panel i got probably only work half their rated capacity, I saw Amazon writeups stating their inefficiency. For $150 for the kit it was worth it for me just to learn with.

  • Netgate Administrator

    When we looked into sun tracking most advice (and our own conclusions) was that it's cheaper and far more reliable to just add panels. My friend adjusts the angle of his panels a few times a year manually. Never tried a maximum power point controller, kept meaning to bulid one.

    This is general discussion:

    Feel free to talk about anything and everything in this board.



  • I need to build another big one soon.  I'm thinking that in the Philippines I can totally disconnect from the grid if I want - At 25 cent per kw/hour it should be nearly three times as economical as in the USA.

  • Would you build an array with a "Branded panel", Hoping in 20 years they will still be around to honor warranty? Or would you go generic.. Like you said earlier Poly looks to getting better.

  • Great question.

    I like reliable name brands.

    My Astro panels are like new and its been a long long time.

    I think kyocera might be a good compromise between efficiency/price/quality.

    I'd bet they will keep working for decades unless someone hit them with a baseball bat.

    If you don't mind spending a little extra, With BP Solar you can't go wrong.

    I'd probably go with the Kyocera cells myself though.

  • Netgate Administrator

    We used BP Solar panels but only because my friend already had them. They must be at least 20 years old and have fallen off thd boat or been hit by stuff countless times, still going strong.


  • Yeah - My kids used to walk and play on my panels in the back yard  - I wish I'd taken pics.  Its near 20 years and they are still going also.

    The frames, glass and backing are as important as the cells themselves.

  • "pfsense" doesn't occur anywhere in this thread.  Perhaps it belongs elsewhere.

  • @gonzopancho:

    "pfsense" doesn't occur anywhere in this thread.  Perhaps it belongs elsewhere.

    General Discussion
    Feel free to talk about anything and everything in this board.

    seems to be the right place  ::)

    I probably could power my pfsense box with a panel and a few batteries.

  • Ive thought many times of powering my pfSense (used the correct stance there see that) box and data center with a solar solution. My cousin also needs a pfSense box and probably would not see any drastic reduction in current to the battery letting it run all day. They have more sun throughout the year than I do as Im im near Seattle.  Im thinking of building him a pfSense box that runs on 12vdc so that the solar array could keep his pfSense router live and filtering all the bad stuff the new Centurylink DSL connection he has to his place has to offer out.

    pfSense mention count- 4

    ;D ;D ;D :o

  • I have multiple Alix 2D13 pfSense running 24/7 from solar+battery feeding 12V DC direct to the appliance.

  • Sounds reliable  (-:

    Compared to a UPS, how much power does that use?  Bill every month?

    How well does that pair up with the "low power pfsense" that people love so much?

    Sounds like a marriage made in heaven to me.

  • Thought about mounting a panel on the roof of my SUV and have my pfSense mifi in a nema4x enclosure with external antennas and a couple of 12VSLA's.
    Project Codename:pfRoofrack

  • @Phishfry:

    Thought about mounting a panel on the roof of my SUV and have my pfSense mifi in a nema4x enclosure with external antennas and a couple of 12VSLA's.
    Project Codename:pfRoofrack

    We have electric rickshaws nowadays in Nepalgunj, Nepal. Maybe I should start pfRickshaw project to keep people online and protected during their rickshaw rides  :P

  • Netgate Administrator

    I know I've asked you this before Phil but I can't remember your reply.  ::)
    Since you have significant real world experience of this could you put some numbers on it. For example, given that the Alix box consumes ~5W (maybe less when idle?) what size panel and battery do you consider sufficient for continuous running? How many hours of sunlight does that require? Do you use a charge controller of some sort to keep the battery equalised?
    These things vary substantially depending on where you are or course but some numbers would be very useful for anyone else considering this.


  • I was able to buys a Optima blue top marine battery. It can be use to store energy produced by solar panel. Can anyone confirm this.

  • Netgate Administrator

    You can store energy in any battery, that's pretty much what defines a battery.  ;)

    But that looks like it's designed as a starting battery and would not be well suited to deep cycle work like a solar install.
    Edit: But it looks like I can't read a website! See below.

    This thread is in general discussion but this is not the right forum to be asking about batteries in general.

    Please keep discussion here to running pfSense hardware from a solar install (or related).


  • Optima blue top marine battery

    Lots of experience with those - Yes you can use those and they last forever if charged properly.  Over-voltage murders them though.

    And you can cycle them hard and they have a very fast charge rate.

    Been using those for many years.  I charge mine with morningstar sunsaver charge controllers attached to 12v 100w solar panels.

    Pretty easy and very reliable.  Relatively cheap for small systems.

    As far as estimating how many PFsense boxes you can run on them, lets say you get 6 hours of direct sun in a day with 200 watt panel.

    1200 watt/hours

    if pfsense were using 5w continuous for 24 hours per day thats 120 watt hours…    So, with ideal conditions you could run 10.

    Conditions are never ideal and I like to leave a big cushion, so I would only really depend on it to run 5 - with a very good battery.  Possible with a 100amp hour battery, but 200 would be better and last alot long since it wouldn't be discharging so deeply.

    There is a pretty big loss when charging lead/acid batteries.  Its generally thought that they are 85% efficient.  I'd bank on 60%

    Meaning you need to build your system at least 50% bigger in terms of both solar cells used and battery used than you will think by doing simple watt/hour and amp/hour math.

    For a single pfsense box:

    So, in a place with lots of light, like Hawaii, a single 40 or 50 watt panel and a single 20 amp hour battery should work fine.

    If its a northern place and not as much sunlight and frequent clouding you probably want to go with a 100w panel and at least a 50 amp hour battery unless you like having dead batteries and pfsense offline.  I would always plus-size solar.

  • Optima brand has been sold many times over the years.  For a while they came out of Mexico and reports are that 48% of the cells were bad. Now the label states Johnson Controls.  They did Navy Base security here for a while.

    Either way Ive had a number of Optima battery's go bad on me over the years prematurely and will never buy one again.

    Look up Deka Battery's made by the East Pennsylvania Battery Company.  I bet your battery bank lives much longer.  I tend to use 4XD banks in some of my remote sites and they seem to never go bad.

    C&D is another remote site battery company we use which do well in the longevity department.

  • If your batteries are going bad you are probably floating them at too high a voltage or running a desulphure cycle thats too aggressive for that type a battery.

    Wet cell batteries are far more tolerant of crap controllers and people who do crazy things.  You can go that route if you have doubts but they do need maintaining.

    That said, Deka is well known and reliable.  I personally won't touch gel-cells and only recommend AGM.

    If Optima has started making crap batteries I wouldn't know…  Seeing as how all mine are a couple decades old at least and have never failed, thus no need to buy new ones lately.

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