Newbie system questions

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  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: Newbie system questions

    Your battery bank is fairly small compared to the size of inverter--Although, AGM batteries are usually much better at surge current support--So it will function (more like a UPS setup--lots of power for a short amount of time). With that inverter, you will could flatten that bank in an hour and a half.

    Also, double check the APC inverter/charger's efficiency. Many times, UPS's are not terribly efficient. At lower power levels, the UPS operating power from battery may be significant vs your loads--especially if your loads are only 100 watts on average (i.e., the solar panel+battery end up supplying a good sized amount of power just operating the inverter).

    Trying to find a smaller/efficient 48 volt inverter to match a 100 watt average load may be quite difficult. Usually the higher voltage systems assume larger battery bank/solar array/higher wattage inverters. You might be looking at 10-20 watts of inverter Tare (before AC loads are even plugged in). Also, check if there is a minimum operating load required. UPS systems may turn off is there is less than X Watts of AC power connected (i.e., don't run if there is no AC load. Make sure it will supply your minimum load (100 watts should be OK).

    And some UPS systems need to be plugged into a wall outlet (even if power is dead) to turn on (I think they sense the neutral/earth ground return connection for a safety check). Also, many UPS systems need a manual start up to turn on if there is no AC input power during a "fail over" (i.e., you have to push and hold one or two buttons to start the inverter for a "cold start").

    Is the APC inverter a MSW (modified square wave) unit? If so, double check your loads are OK running on MSW wave forms. Sometimes, small AC to DC plug in converters (cell phone chargers, laptop computer power supplies, portable DVD power supplies, etc.) are not very happy with MSW power and can overheat.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Newbie system questions

    The few times people have "gone negative" on you is to try to prevent you from making mistakes. Battery choice is one of those easy mistakes to make. You admit you've never done any solar power project before. Well, we have. Lots of them. One of the big mistakes people make is trying to use gel batteries. Very easy to fry them on an RE system. Another is sinking $ into AGM's and then - poof! Vent popped; batteries are scrap metal.

    Every solar power system is different. Getting yours "dialed in" will always take some experimentation. It's simply easier and cheaper to do with a set of flooded cells that you can watch electrolyte levels on and measure the specific gravity (no better indicator of charge). They aren't as dangerous as you may have been lead to believe either. I keep mine inside; no problem. I don't think I'd ever get AGM's - and not just because I'm a cheapskate. I don't see any "clear drawbacks" to them, only clear advantages. :D
  • ParticleParticle Registered Users Posts: 20
    Re: Newbie system questions

    Thank you both for the advice. I've yet to purchase batteries, so that is still something for me to think about. No matter what the type, I imagine the first priority is to be diligent. I do intend to be careful.

    There were some questions about the UPS that I'd like to answer. Efficiency over its entire range as a whole could be considered good, but as with all power supplies it's going to suffer quite a lot at small load levels.

    100% Load (1760W) – 94.9% Efficient
    75% Load (1320W) – 94.4%
    50% Load (880W) – 93.3%
    25% Load (440W) – 89.4%
    6% Load (100W) – 70%

    Given that it's available for free, however, I suppose it's a good place to start. Cotek (owned by Samlex?) makes a number of small, 48V, pure sine inverters such as the SK350-148 that I'll be able to pick up for small typical loads if necessary. It's relatively inexpensive at around $150 since it's a lower power model. The 1000W models I had originally been eyeballing were 400-600 dollars.

    Is there any reason to limit a battery bank to a single inverter? If not, I could choose which to use based on the load and have both perhaps. One concern I still have with using a UPS is noise. I don't know how loud this particular model of UPS will be, but I know I've heard other fan-cooled units which were rather noisy.

    The UPS is pure sine wave which is something I've been really trying to hold onto despite the budget. I was concerned about simple power bricks like you mentioned here. I doubt a SMPS would care much, but I'd rather not have to be concerned when considering a given load I'd like to run. It can be cold started as I'm intending by holding the diagnostic button for a few seconds. It will have a periodic beep but that can be disabled as well.

    I've been looking to see if someone makes a power cord that has just a ground wire with a ring terminal or something to that effect so that I can ground the inverter directly and easily. If not, it should still be grounded via the chassis when it's with the other rack equipment. The rack itself isn't grounded, but all other equipment there is which should give it a solid ground path. I'll want to check the inverter chassis with a meter to make sure it and the external ground terminal are bonded though.

    Thanks again, guys.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Newbie system questions
    Particle wrote: »
    Is there any reason to limit a battery bank to a single inverter? If not, I could choose which to use based on the load and have both perhaps. One concern I still have with using a UPS is noise. I don't know how loud this particular model of UPS will be, but I know I've heard other fan-cooled units which were rather noisy.

    There is one reason to limit a battery bank to a single inverter: available power. Otherwise, no. Sounds like you may switch between one inverter and the other, so the over-all power availability isn't much of an issue (yes, some people have two inverters on one bank and run them all the time; the bank has to be large enough to accommodate the full power demands of both inverters).

    Some standard inverters are a bit noisy too. Especially those that don't have T-stat controlled fans. WHOOOOSH! all the time. Very annoying. :p
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: Newbie system questions

    You can have several inverters attached to the battery bank just fine. A small inverter on 100% of the time and a large inverter only when needed (power tools) is certainly doable... You will probably need to add a DC On/Off switch to the input of the standby inverter to make sure you are not simply adding more parasitic loads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ParticleParticle Registered Users Posts: 20
    Re: Newbie system questions

    I've started to buy parts. One of them came in today. I had ordered a PS-15M-48V but a PS-15M-48V-PG was delivered instead. It figures. I'm not sure what difference a charge controller would have internally though for a positive ground system unless the controller itself were to be grounded. Is the charge controller chassis usually grounded (earthed)? I was only planning to ground the inverter.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Newbie system questions

    Usually the negative side is connected to ground along with the cases of the controller and inverter.
    New NEC regs require the PV (+) and (-) to be isolated (GFDI) which is a pain and not necessarily a good thing.
    A positive grounded charge controller may present some problems (I'm not familiar with that particular unit). I'd send it back and tell them to get the order right. Usually you only need to use this with certain panels and/or in telecom installs.
  • ParticleParticle Registered Users Posts: 20
    Re: Newbie system questions

    Slow but sure progress. The seller didn't have any of the negative ground units. He modified his listing to reflect that they're the -PG model instead. He offered to refund the price plus return shipping, but Morningstar offered to exchange it as well regardless of there being no defect. I'll go the exchange route with Morningstar since they're both fully informed and still willing. I managed to get the unit at a great price and would like to hold onto that discount.

    Batteries and panels will come later. Those 190W panels can't be shipped as cheaply as advertised. The company indicated it was a listing mistake. I'm getting a lot of that lately.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Newbie system questions
    Particle wrote: »
    Slow but sure progress. The seller didn't have any of the negative ground units. He modified his listing to reflect that they're the -PG model instead. He offered to refund the price plus return shipping, but Morningstar offered to exchange it as well regardless of there being no defect. I'll go the exchange route with Morningstar since they're both fully informed and still willing. I managed to get the unit at a great price and would like to hold onto that discount.

    Batteries and panels will come later. Those 190W panels can't be shipped as cheaply as advertised. The company indicated it was a listing mistake. I'm getting a lot of that lately.

    Morningstar is a great company: their customer service is second to none.

    As for the your retail experiences ...
    Another reason to buy from our host, Northern Arizona Wind and Sun (http://www.solar-electric.com/); they don't make those kind of "mistakes".
    It's worth an extra dollar to be sure you get the right thing, including a staff of people who know what they are doing.

    And just to reiterate, none of us moderators work for them or are in any way associated with the retail business. There is quite the "arm's length" relationship between the business and the forum. That's why they both work so well.
  • ParticleParticle Registered Users Posts: 20
    Re: Newbie system questions

    Ok, now I'm less impressed. Morningstar replied to my acceptance of their offer with "contact your place of purchase to arrange for product exchange". It's the same guy, so it isn't a case of two reps handling it differently or anything. I could understand them not wanting to do it at the start, but to have offered and now tell me to take a hike does make me agitated.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Newbie system questions
    Particle wrote: »
    Ok, now I'm less impressed. Morningstar replied to my acceptance of their offer with "contact your place of purchase to arrange for product exchange". It's the same guy, so it isn't a case of two reps handling it differently or anything. I could understand them not wanting to do it at the start, but to have offered and now tell me to take a hike does make me agitated.
    I'm confused. Aren't they telling you to take the one you have to where you bought it and they'll give you a replacement? How is that telling you to take a hike?
  • ParticleParticle Registered Users Posts: 20
    Re: Newbie system questions

    You may be missing some pieces of what happened. I'll provide a more verbose timeline below. The events span about a week.
    • I bought a Morningstar ProStar PS-15M-48V charge controller that was being offered at a very good price.
    • I received the charge controller and discovered it was a PS-15M-48V-PG (positive ground version) instead.
    • I emailed the seller and informed him of my discovery.
    • I emailed Morningstar and asked for advice on the implications of mixing a positive ground charge controller with an otherwise negative ground system. To me it seemed like it should work fine so long as the charge controller itself wasn't earthed.
    • The seller replied saying he was sorry and that he would refund the purchase price and also provide for return shipping should I want to send it back.
    • I asked the seller to wait pending a reply from Morningstar. If it would still work for me, I'd just as soon keep it instead of send it back to the seller.
    • Morningstar replied saying that my suspicion was correct--it should work fine if not earthed. Additionally, the rep offered to exchange it for me "under warranty" for a negative ground model if I wanted to so long as I provided the serial number.
    • I replied to Morningstar saying that I appreciated the offer and would indeed like to take them up on it because of the good deal I had received.
    • I emailed the seller telling him not to worry--Morningstar had made an unexpected offer to exchange it for me which would resolve any lingering doubts.
    • Morningstar replied back saying to return it to where I bought it from.
    • I posted here with my miniature rant so as to vent.

    Since that time, however, I replied to Morningstar reminding them of their offer and that I expected them to honor it. They replied back and apologized, saying they had neglected to refer to the previous messages (where they had offered). The return was again offered provided I gave them address information and such. I gave it to them. Now I wait to see what happens.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Newbie system questions

    only thing that bothers me would be the return to the seller as i'd have thought it should be sent back to morningstar.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Newbie system questions
    niel wrote: »
    only thing that bothers me would be the return to the seller as i'd have thought it should be sent back to morningstar.
    Is the seller local? If so and if it were I, taking the wrong one back to the seller, getting the correct unit on the spot, and letting the seller deal with all the shipping and receiving would be the way I would prefer to do it. If the seller is on line, though, I'd just as soon deal with Morningstar directly, though I don't see a whole lot of difference.
  • ParticleParticle Registered Users Posts: 20
    Re: Newbie system questions

    The replacement from Morningstar arrived today. It even came with a pre-paid return label which is handy. I don't have batteries or panels yet, but it should power up with 15 VDC so I'll play with it a bit later.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Newbie system questions
    Particle wrote: »
    The replacement from Morningstar arrived today. It even came with a pre-paid return label which is handy. I don't have batteries or panels yet, but it should power up with 15 VDC so I'll play with it a bit later.

    Whoa.
    What do you mean "it should power up with 15 VDC"? Do NOT put a power supply on either the input or output. If you don't have batteries for the output, leave it alone. If you don't have panels for the input, don't put any other power source to those terminals.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Newbie system questions
    Particle wrote: »
    The replacement from Morningstar arrived today. It even came with a pre-paid return label which is handy. I don't have batteries or panels yet, but it should power up with 15 VDC so I'll play with it a bit later.

    the return label i would imagine is for sending the old one back and is not a handy option.

    as you were advised, do not test it by methods it was not designed to work under.
  • ywhicywhic Solar Expert Posts: 612 ✭✭
    Re: Newbie system questions
    Whoa.
    What do you mean "it should power up with 15 VDC"? Do NOT put a power supply on either the input or output. If you don't have batteries for the output, leave it alone. If you don't have panels for the input, don't put any other power source to those terminals.

    Listen to the above and I'll add this as well..

    OP.. You do understand the 15 # in the model number means upto 15 amps of panels coming in correct..

    You do understand if you do not have a battery to PROPERLY test it you may ruin it..

    You got the correct unit now leave it be to you get the other components..

    Nothing to really play with on that unit..

    Please read the manual again as well.

    If you have a battery bank please note you should connect the battery side 1st.. hooking anything to the SOLAR/PV/IN first may/will cause a short and fry the new unit..

    Please read the manual again as well. << doubled for emphasis..
  • ParticleParticle Registered Users Posts: 20
    Re: Newbie system questions

    You guys are panicking about nothing and sarcastic insults certainly aren't necessary. Yes, I know the 15 in the model number is a reference to how much current it can regulate. I also understand that "Minimum Voltage to Operate: 15V" means the unit's electronics are capable of operating at >= 15VDC. It isn't going to charge or discharge under those conditions, especially when I'm hooking up neither a load nor power source. All I did was hook it up to a 24V battery source that's too small for use as an actual battery bank so that I could see and interact with the interface. It's quite capable of sourcing the 28 mA needed by the unit's electronics, however. That's what I consider playing, and there's absolutely no danger in having done it.

    ---

    Niel, I consider it handy because generally RMA service requires the customer to pay for their own return shipping. I was pleasantly surprised to see the prepaid label, so I'm not sure what you're upset about.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Newbie system questions

    Particle;

    There was no panic nor any sarcastic remarks. Just sound advice about not connecting a charge controller in any way it is not intended to be connected. This includes what you seem to have done: connect the input side to a 24 Volt source. Connecting a controller's input to anything, even panels, without batteries connected to the output is a bad idea. If your controller is now ruined, don't say you weren't warned. If it isn't, consider yourself lucky.

    You come here seeking advice from people with experience. You get that advice. If you don't heed it there's nothing we can do about that.
  • ParticleParticle Registered Users Posts: 20
    Re: Newbie system questions

    Again, that's not what I did. I connected the battery terminals to batteries. What is the big deal? There isn't one.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Newbie system questions
    Particle wrote: »
    Again, that's not what I did. I connected the battery terminals to batteries. What is the big deal? There isn't one.

    Your post was not at all clear about what you were going to do or had done. Lots of people make such vague posts and it turns out they've done something very wrong. We have to err on the side of caution.
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