Solar Power - Charge and Use at the same time?

hunter44102
hunter44102 Registered Users Posts: 24 ✭
in General Solar Power Topics #1
All,

If I have a Solar panel, a charge controller, and a Battery, can I hook up devices to use the battery, even when its charging in the day?

I'm asking because with regular WALL battery chargers, I've been told the following:

"You can destroy the battery if the charger is not a "smart" charger (meaning microprocessor controlled) to avoid getting into a situation where the charger locks up in absorption mode and overcharges the battery. The standard 3 mode charger can not tell the difference between battery charging current and external load current and will tend to lock up in absorption mode when current is going to an external load."

So does this apply to Charge Controllers also? EDIT: The Charge controllers have a LOAD connection. Does this take care of the problem? What if I needed to hook up an Inverter directly on the battery?

Basically, I want a simple system where I can charge the battery and use the energy as needed without anything sophisticated. Can this be done?

I have an ASC 12V 16A charge controller.

-hunter
· Share on Twitter

Comments

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #2
    Re: Solar Power - Charge and Use at the same time?

    Hunter,

    There are several “smart” battery chargers and controllers around that can be fooled when powering loads in parallel with the batteries. For example, the Xantrex TC 20+ and TC40+ battery chargers don’t drop out of absorb mode until one hour after the absorb stage current has fallen below 4 A. As long as the current exceeds 4 A, it won’t drop out of absorb.

    I believe that the Morningstar Prostar controllers won’t drop out of absorb (PWM) mode until the PWM duty cycle has fallen below 30% for an hour or so. See: http://www.morningstarcorp.com/products/FAQ/#float Accordingly, some charge controllers may indeed have the same “problem”.

    I’m not directly familiar with the ASC controllers. However, Major Charge battery chargers use a timer to control the absorb stage.
    Basically, I want a simple system where I can charge the battery and use the energy as needed without anything sophisticated. Can this be done?

    I submit that powering an external load and not influencing the absorb cycle is not a trivial issue, and it will require at least a timer. The Outback MX60 controller’s adjustable absorb cycle can be limited by time or low output current.

    The Morningstar TriStar might be user configurable (via a PC) to time-limit the absorb stage, but I don’t know for sure. You may wish to contact Morningstar’s technical support staff on this issue. Optionally, a TriStar might be able to be configured as a “load controller” and only power your load under specific conditions. See the TriStar manual: http://www.morningstarcorp.com/products/TriStar/info/TS_Manual.pdf

    Finally, the Blue Sky controller’s seem to have some timer and/or aux load control functions. Here’s a link to their model 3024: http://www.blueskyenergyinc.com/pdf/manual%20bse%20sb3024i%20rev%20b.pdf

    HTH,
    Jim / crewzer
    · Share on Twitter
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Solar Power - Charge and Use at the same time?

    as an alternative to buying another controller you may wish to buy another battery and use a heavy duty switch to alternate between the batteries for charging. another switch, but heavy duty like this one http://store.solar-electric.com/basw1300amp.html for switching the loads to the battery of choice. what this does is allow you to charge one battery while using the other. it is dependant upon you to switch the batteries and loads properly, though, as it's not foolproof, but could even be cheaper to do depending on your choices.
    · Share on Twitter
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #4
    Re: Solar Power - Charge and Use at the same time?

    Reading between the lines, as it were, suggests to me that Hunter is trying to make use of available energy that's otherwise "wasted" when his controller is in its absorb- and/or float mode(s). A second battery won't help address that issue.

    HTH,
    Jim / crewzer
    · Share on Twitter
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Solar Power - Charge and Use at the same time?

    righto as a diversion controller also could. i also can say that charging another battery could facilitate the wasted power from the other after it is charged as it is just another load. with that he could just put it to lights or heating elements or whatever instead of another battery once the battery he has is charged. i hope i hit the subject matter here. if not i will reread more carefully.
    · Share on Twitter
  • hunter44102
    hunter44102 Registered Users Posts: 24 ✭
    #6
    Re: Solar Power - Charge and Use at the same time?

    Thanks everyone for all the good information. I will keep studying more about charging systems.

    Here are some questions from my curiosity:

    - Doesn't every car charge the battery and have loads on it all the time? How does it accomplish this without battery damage? Or does it isolate the loads (from the battery) once the car is running?

    - Doesn't a Laptop do the same thing? While the I am typing on this laptop, it is charging the battery (and powering the laptop).

    So I'm wondering how solar charging could be different. The timer method makes sense but I need to understand a little more about absorption before I ask more questions!

    Background info:
    In the summer here in the northwest, we can have up to 14-15 hours of sunlight each day so if the battery reaches full charge after 5-6 hours, there would be a waste of 9 hours unless I can keep using the energy, so thats where it would be nice to just have constant loads and charging so that the least energy is wasted.

    -hunter
    · Share on Twitter
  • System2
    System2 Posts: 6,290 admin
    #7
    Re: Solar Power - Charge and Use at the same time?

    hey hunter,
    the simplified answer is you are absolutely correct with your 2 examples, and i in fact run loads while charging all the time. in fact the website in my tagline ALWAYS is running even while the batteries that run it are charging (even doing eq's). i charge my laptop while charging the solar batteries that charge my laptop.. the bottom line is you just have to make sure you are getting enough current to keep the batteries absorbing, or reaching absorb in a timely manner. for example on a nice sunny morning, if my batteries are relatively charged up (ie: there hasnt been 3 days of clouds to catch up from), i know (from experience with my setup) that i can run my office , website and even charging the laptop and still reach and maintain an absorb stage by the middle of the day. If i did not run loads under the same conditions the batteries would be charged by 10am so you can see i have plenty to work with. on overcast days i know better. on a bright overcast day i might wait until the batteries are in float mode and then turn on the larger loads , allowing the controller (mx60) to run my loads and keep the batteries floating.

    so, if you have adequate charge coming in youre good. im using an mx60 charge controller and im no sure if others work the same way, this is the only one i have ever had- but it is smat enough to allow more power in off the panels when a load comes on to maintin whatever charge stage its at
    · Share on Twitter
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
    Re: Solar Power - Charge and Use at the same time?

    many other batteries are not getting a proper recharge while they allow you to use them while charging. car batteries are always running a deficit and would benefit from a small regulated solar panel to finish off the charging process. car battery charging is a compromise that the auto industry uses and is a cheap way out of paying for a good battery charging arrangement.
    say for example you have a 100ah battery and a charger that gives 6amps. this is a typical value for some automotive chargers btw, but those chargers could overcharge your battery as they usually don't have regulators in them. now let's assume this charger is in its bulk stage and that it will take it to the end of the charge process and stop, which it does not do in reality as other stages of charge exist. this is a fine charge rate as it is 6% and most charging applications should be better than 5%, but in light duty apps even a 3% rate could be gotten away with at times. get into that later if need be. now at that rate of 6amps we're looking at around 17hrs (100/6=16.67) of charge time if we don't account for other true charge stages, losses, and other charge time influences.
    fine you say, but we are also talking about with no loads on it aren't we? now let's put a 4amp load on it from some lights. the lights get 4amps while the battery gets 2amps and this is a 2% rate. that is 100/2=50hrs. many batteries will not charge with that rate in 50hrs due to losses they experience in maintenance charge so this could be 100hrs if at all to fully charge.
    now this time with the same battery and charger rate, a load of 12amps is placed on the battery. the charger will give 6amps to the load, but the battery will also give up 6amps to the load. the battery is now draining and will probably be at the 50% dod mark, we call the depth of discharge, in a bit over 8hrs.
    circumstances differ, but excess power during absorb or float can be redirected when using a diversion controller. it is acting like a switch to automatically pipe the power elsewhere when a certain point is reached. what you'd like to do with that power is up to you. now without a diversion controller in place and plenty of known current flowing i have shown that the excess power could be put straight to other loads as long as the battery continues to get a proper charge current. solar, however, changes and if there isn't a scheme to automatically shut down the excess from going elsewhere during low or no sun periods you will drain power off of the battery. if you are there to do this manually it does work, but missing one time could be costly.
    · Share on Twitter
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #9
    Re: Solar Power - Charge and Use at the same time?
    righto as a diversion controller also could. i also can say that charging another battery could facilitate the wasted power from the other after it is charged as it is just another load. with that he could just put it to lights or heating elements or whatever instead of another battery once the battery he has is charged. i hope i hit the subject matter here. if not i will reread more carefully.

    Another battery would no doubt be another load. Whether it would be a practical load is another matter. For example, it would be only be 80% - 90% efficient. Also, once the charger hits the absorb stage with battery #2, then Hunter would be right back to the original problem of finding a way to put the unused energy from the PV array to good use.
    -  Doesn't every car charge the battery and have loads on it all the time? How does it accomplish this without battery damage? Or does it isolate the loads (from the battery) once the car is running?

    Car batteries are generally called SLI, or starting, lighting and ignition, batteries. They are built to deliver short bursts of high current (porous plates, lots of surface area), as opposed to deep cycle batteries which are designed to deliver low current over a long period of time (dense plates). The no-load voltage on a starting battery typically doesn’t fall very far, and the alternator’s regulation voltage typically doesn’t exceed ~13.7 V, so there’s little danger of “overcharging” the car battery. In short, apples and oranges, and this is why automotive charging systems typically are not particularly effective at correctly charging deep-cycle batteries (i.e., RV applications).
    -  Doesn't a Laptop do the same thing? While the I am typing on this laptop, it is charging the battery (and powering the laptop).
    Laptop batteries are typically NiMH or Li-ion, not deep-cycle lead-acid. I’m not familiar with their behaviors, their charging algorithms, nor their chargers' levels of sophistication.
    So I'm wondering how solar charging could be different.    The timer method makes sense but I need to understand a little more about absorption before I ask more questions!

    Background info:
    In the summer here in the northwest, we can have up to 14-15 hours of sunlight each day so if the battery reaches full charge after 5-6 hours, there would be a waste of 9 hours unless I can keep using the energy, so thats where it would be nice to just have constant loads and charging so that the least energy is wasted.

    A noble concept, but not quite in tune with reality. You may have 14-15 hours of daylight in the summer, but, compared to the mid-day Sun, the sunlight is not particularly intense in the morning or late afternoon, so potential output from a PV array varies during the day. Check the tables below for accurate insolation data for your area. But, you're on the right track: bulk charge the batteries in the morning with little or no ancillary loads, and then apply "diversion" loads in the afternoon while the charger is in absorb mode and there's other unused energy available from the PV array.

    http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/state.html
    http://rredc.nrel.gov/solar/pubs/redbook/

    HTH,
    Jim / crewzer
    · Share on Twitter
  • sv_makai
    sv_makai Registered Users Posts: 9 ✭
    #10
    Re: Solar Power - Charge and Use at the same time?

    While cruising and living off solar only we used the process outlined above and found after 3 years the batteries were performing as expected. We were always charging and using at the same time. A boat can have some pretty extensive loads placed on the banks.

    Our process was to let the bulk charge bring the bank up to 85% (9ishAM) before using heavy loads, such as water maker, washer, etc. The fridge and freezer we on demand 24/7. We generally tried to complete the heaviest useage by 12-1 to insure that we could bring the batteries up to full charge and float and keep our water tanks topped off. This ensured that we were getting a complete full charge daily.

    If the overnite usage was lower and the bank charge completed earlier we would divert some of the extra charge by turning down the fridge or freezer temps or running the WM. Mid-late day was when the fridge/freezers worked the hardest as the temps were the highest in the caribe. Bringing the temps down reduced our night time usage as the units would not be drawing on the battery banks until the inside temps came up to the normal levels. Basically we would store the excess electricty in the freezer. This would reduce our overnite usage as we would reset the temps when the sun started to drop off. Our goal was to always have a float charge on the batteries by days end.

    Every 3-4 weeks we would equalized the batteries (liquid) to ensure their longevity and efficency.
    · Share on Twitter
  • hunter44102
    hunter44102 Registered Users Posts: 24 ✭
    #11
    Re: Solar Power - Charge and Use at the same time?

    I've learned a lot of good ideas so far. Thanks everyone.

    So far I like the Diversion controller idea like the Xantrex C60:

    "The C Series automatically directs extra power to a dedicated load such as an electric water heater and ensures batteries are never over-charged"

    · Share on Twitter

Categories