Growing pains or not?

TDSolarguyTDSolarguy Solar Expert Posts: 31 ✭✭
Greetings Forum
I don't post a lot on the forum but do read the posts from others and the help folks get from moderators and others. I have learned so much by just reading. I am having growing pains and want to tweak my system. My system is used as a charging station for all my power tools and to run my C-pap machine each night. It has worked out well for me and is very balanced thanks to many on this site.

Earlier this summer I bought a new Worx's cordless lawn mower and everything worked fine on my system. Now that it is getting later into the year and fall around the corner and shorter days with sunset earlier, things are changing. After mowing the lawn last week and waiting the next day in the morning before going to work, I plugged the lawn mower battery into my inverter to recharge it before going to work in the morning. I turned it off when I get home and it was fully charged. 8 1/2 hours later.

I run my C-pap machine during the night as I have always done. In the morning I noticed a yellow LED light on my charge controller battery indicator light at middle capacity. This never happened earlier in the year, I always woke to a green LED light reading of 12.55 or so + or - Before bedtime it would in the high 12 to 13. something. Always a full charge.

Sorry, I don't have any amp battery gauge. Never figured out how to install the cheep Chinese one without a shunt or instructions.

Next, on a weekend I timed how long it took to recharge my lawn mower battery.
5 hours. I think I know what it's all about. I'm short on power going into the battery bank for what Im using . Less sun time exposure for the panel. I'll put the watts up meter to it this weekend after mowing.

Here is what I have now.
100 watt solar panel. 75 Amp 12 volt battery bank flooded wet cell. Morning Star 15 Pro Star charge controller non meter version. Samlex 300 watt inverter. A long 100 foot Mc4 cable to charger. Cant be helped.


I'm thinking about buying a Morning Star MPPT SunSaver 15 AMP charge controller to help with the long line power loss and a better gain of the use of a MPPT controller vs my current PWM controller.
PS. Mowing season is almost over. Do nothing and keep what I have or charge off AC outlet.

Thoughts?

TD Solar guy

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Growing pains or not?

    Your problem is right where you think it is: shorter days + different sun angle reduces the daily 'harvest'.

    A single 100 Watt panel would get you about 260 Watt hours AC on a good day with 5 hours of sun. Shorten that by 1 hour and it's down to 208 Watt hours.

    You say it takes five hours to recharge the lawn mower? There's another problem, as you probably only have five hours of good sun total, much less five hours for using power from. It's like trying to charge twice as much battery in the same time with the same amount of panel; it isn't going to happen.

    Then you say you've got some long wire run between the panel and the charge controller. That will be costing you more power.

    In short you've made the standard mistake of adding more load to a system that is not capable of handling it. When the sun is good and the hours are long it works, but the more marginal the sunlight becomes the less power you have to work with.

    Your single 100 Watt panel is already stretched to recharge a 75 Amp hour battery. It's probably capable of 5 to 6 Amps. That's like being able to replace 30 Amp hours a day, maybe only 25. Depending on how deeply you discharge the battery that could be not enough. If you plan on continuing this way you will need more panel, and possibly a larger battery.
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Growing pains or not?

    A 100W "12V" panel (normally 17Vmp) is roughly 6A max. That's an 8% charge rate for a 75AH battery, which is at the low end of desired but okay depending on loads.

    Switching to MPPT would give you a *little* gain, since it could operate at Vmp instead of Vbatt, but the real benefit of MPPT is that you can run your panels in series rather than parallel to get a higher voltage input - thus less current and less I2R losses in the wire coming down from the panels. You can't do that, of course, with just a single panel.

    You'd get far bigger gains for the dollars spent if you just bought a second panel and parallel it with the existing one.

    Using "ideal" numbers here:

    Switching to MPPT would give you a (theoretical) increase from 13.5V*5.88A = 79.4W to 17V*5.88A = 100W - 20W increase for a $220 controller or $11/watt.

    Or you can buy another panel. A quick browse of the NAWS site finds an 85W 12V panel (Vmp 17.9, Imp 4.84) for $240. Put in parallel with your current panel on a PWM controller it would give 13.5V*4.84A = 65W, or $3.70/watt.

    Granted, very rough numbers, and shipping may be higher on the panel.

    You may also wish to buy an identical panel to what you have, or at least one that more closely matches Vmp and Imp, in which case if you in the future decide to go MPPT you could rearrange them in series effectively. You wouldn't want to series your 100W with the 85W I found as you'd be limited to the 4.84A of the 85W thus losing / wasting some of the capacity of your 100W.
  • TDSolarguyTDSolarguy Solar Expert Posts: 31 ✭✭
    Re: Growing pains or not?

    Thanks guys.
    Using more then I have. I'm learning.
    Action plan is now in place. I'll start charging my lawn mower battery on our home AC power. Mowing season is almost over and I'm ordering another 100 watt panel next month and connecting in parallel. Come Spring time I think i'll order a 15 amp MPPT Morning Star controller. I just want one so that I can connect my panels in series rather than parallel and have a better controller.

    If you will please, one other question.
    Would it be overkill to get a Trimetric TM-2025A 12-48 Volt Battery Monitor with such a small system or just buy the add on meter with the Sunsaver MPPT controler? I'm tired of not knowing what is really going on with my battery bank other then voltage.

    Thanks
    TD Solar guy
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Growing pains or not?

    Because it needs to be asked: just how far is it from panel to controller? An MPPT unit is expensive so you need to make sure it is justified.

    The two meters you mention are not comparable. The Morningstar meter tells you what the charge controller is doing whereas the Trimetric monitors all current going in and out of the battery to tell you what the SOC is at any given moment. Personally I wouldn't bother with either on a system this small. To stay on a budget you might consider one of MidNite's educated Voltmeters: http://www.solar-electric.com/mnbcm.html Not as good as a battery monitor but better than a plain Voltmeter.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Growing pains or not?

    Yes, the MNBC would probably identified that you were NOT getting a full charge over time and that your battery may have not been fully charged. A good tool for a small /RV system.
    I have one I use at home for monitoring after recharging my electric-trolling-motor battery which is second hand to me (free) as it would not 'keep' a good charge...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • TDSolarguyTDSolarguy Solar Expert Posts: 31 ✭✭
    Re: Growing pains or not?

    It is about 80 feet away out in my yard on a mobile stand. I got that length as that was close to what I needed to be abbe to move it out to the back end of my property to keep it from my neighbors church building that casts a shadow and blocks the sun on my property. .I have a ground bolted on the side panel with a copper wire for ground and connected to a f15 amp DC fuse breaker in my home before going into the charge controller. I didn't want to go under ground as for code issues and not knowing how or what to do and my wife who will not let me tear into our nice lawn. I know, what a hassle. I am planing to put it on a poll in my front yard next to my home where it will not move and no ones home casting a shadow on it. That distance would be about 60 feet running under the house up through the floor and to the controller. In the end, it's still 100 foot long until It gets on the poll up front. Another project for sure.

    Thanks for the link to the meter Cariboocoot.

    T D Solar guy
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Growing pains or not?

    i'm not sure of what gauge wire you are using, but i would suspect it may be undersized for that distance with you revealing along with a critical other half who delves into the superficial. you may very well benefit putting 2 identical pvs in series through an mppt cc.

    by the way, when not using the inverter make sure it is not powered as it will continue to draw battery power even without loads connected to it.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Growing pains or not?

    80 feet? Argh! Rough calculation: it would need to be 6 AWG to keep the V-drop below 3%.
  • TDSolarguyTDSolarguy Solar Expert Posts: 31 ✭✭
    Re: Growing pains or not?

    Thanks Guys.
    Westbranch, It sounds like a neat setup for a guest cabin. I want a get away cabin when I retire. Neil, I believe the wire is 10 gauge MC4 cable. It works great for the time Iv'e had the system charging all of my small needs even with the power loss in the line. That was one reason I was thinking a MPPT controller after I put my lawn mower into the mix. I do have the inverter off when not in use. I also was thinking along the line of what RandomJoe said. Add another panel. Thanks to all.

    TD Solar Guy
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Growing pains or not?

    just to add, go for another panel since your CPAP is essential equipment. You definitely need more PV if in winter 1 panel will 'just' suffice. What about the 3 day no sun rule of thumb? that is where we plan a battery system to provide for all essential loads for 3 days.
    hth
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • TDSolarguyTDSolarguy Solar Expert Posts: 31 ✭✭
    Re: Growing pains or not?

    Hello all
    Based on all input from all, I came up with an action plan.
    Shorten the wire run. Less power loss. I need to move my panel up to the front of my home. This would cut the distance to about a 55 foot run.and keep the V drop down and longer sun exposure time with no shadows.

    MPPT controller.
    Maybe. I tend to want the Sunsaver 15 amp and would be able to connect in Series with another panel.

    Another panel. Yes. I'm ordering another 100 watt panel.

    Battery: This is a new idea. Good or not?
    I'm looking at two AGM 12 Volt batteries @ 50 amp each sold at our local Les Schwab store.They are the blue top ones made by OPTIMA. Are they deep cycle worthy of Solar? I Would connect them up in parallel to keep at 12 volts. My understanding is that a MPPT controller would be able to charge these batteries from two panels connected in series. My inverter is a 12 volt. Don't want to get a new inverter for 24 volt battery bank.
    I do know I would like to go to an AGM battery but they cost a lot for shipping over the internet.

    Unknown to you guys is that I am venting my wet cells batteries through a window that is framed in with plywood. It has a 4 inch aluminum dryer tube from an igloo cooler where my batteries are venting to the outside I would love to get rid of all that setup.
    Am I all mixed up? I hope not.



    Thanks so much.

    T D Solar Guy
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Growing pains or not?

    Let's see, right now you've got 75 Amp hours @ 12 Volts and not enough panel to recharge it.
    The solution to this is not to increase the battery bank to 110 Amp hours.

    If you add the second panel and an MPPT controller you'll have enough power on a good day for 128 Amp hours @ 12 Volts. But do not add the extra battery capacity first!

    Also, I think the Optima yellow top is the closest to a true deep cycle. That's probably written down somewhere. I also think they're a lot of money for experimenting with solar, but they're probably a lot cheaper down there too.

    Battery shipping is expensive due to the weight. In the case of AGM's it should be cheaper because they weigh slightly less per Watt hour equivalent and they are not classified as hazardous because they can not spill.

    In my opinion the second panel will make the biggest improvement for the money.
  • TDSolarguyTDSolarguy Solar Expert Posts: 31 ✭✭
    Re: Growing pains or not?

    OK. I'm ordering the extra panel Wednesday. I heading out to Home dept to check out a pole to place in my front yard. I am blessed to be able to do these things now. It wasn't always so. Empty nest now and older paid off cars and no debt. Wife and I both work full time and are Dave Ramsey followers. God bless you guys for the help.

    T D Solar guy
  • TDSolarguyTDSolarguy Solar Expert Posts: 31 ✭✭
    Re: Growing pains or not?

    Hey Westbranch.
    Yes my CPAP is essential equipment. Whats funny is that I am an average weight guy. I'm not overweight. The Doc says that he sees a few of us now and then. I have a cheep gas generator from Bimart. I use it whenever I go camping and Elk hunting. Keep a 5 gal can of gas at all times. I ran over to Les Schwab a few minutes ago and ordered the Yellow top OPTIMA AGM battery. They only had one in stock and they are ordering another one for me. I'm going to add the MorningStar MPPT 15-AMP Controller to the panel order to save on shipping. Getting the meter also. While I'm at it, might as well order the PV poll side mounts as well. Might as well bundle it all together. Oh, and the MC4 connectors to make a series connection for the panels. Wow, this takes a lot or stuff and research. Fun though. It reminds my of all my reloading stuff I got over the years.

    T D Solar guy
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Growing pains or not?
    TDSolarguy wrote: »
    ...Wow, this takes a lot or stuff and research. Fun though. It reminds my of all my reloading stuff I got over the years.

    T D Solar guy

    Think of Renewable Energy as Energy Reloading?
    SMA SB 3000, old BP panels.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Growing pains or not?

    you should ask them if they are getting more than one in as it would be nice to have 2 from the approximate same batch rather than one older that was laying around and one new one. see if they will allow that exchange on the older one already in your possession if they are getting in more than 1.
  • TDSolarguyTDSolarguy Solar Expert Posts: 31 ✭✭
    Re: Growing pains or not?

    Thanks Niel
    My reading of hundreds of posts paid off. I learned about that issue from this site. The battery I have is stamped 9/12. Yep, it's fresh and the new one coming better be. I'll make sure of that but will call them tomorrow morning to make sure. Going to ask if they will sell my old ones on consignment for me, Thanks for the heads up Niel.

    T D Solar guy
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