Problem with low voltage from charge controller

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Plowman
Plowman Solar Expert Posts: 203 ✭✭✭✭✭
in Solar Beginners Corner #1
Howdy all, this is my first post here but I've learned a lot from reading this board.

I've got a very small off-grid 12V system consisting of the following:
--Two Trojan T-105s (new as of 2 weeks ago)
--One Dmsolar 158W 12V panel
--Cheap no-name Chinese 10-amp PWM charge controller
--Honda EB3500 generator
--Iota IQ4 45 amp battery charger
--Sima 150W cigarette plug type inverter
--Watts Up and Kill-A-Watt meters

I'm living on a somewhat isolated spot on the farm I work on, no grid access, so I use this system to run pretty much everything at the moment. I'm only drawing roughly 20 amp-hours per day from the batteries (measured with Watts Up between battery and inverter). I've been using the gennie and an old Sprinter battery all winter, I just installed the solar panel and Trojans last week.

Here's my problem. Using the Watts Up meter over the last week, I've only seen 13.0-13.6V or so coming from the charge controller (the meter is installed between CC and batteries). At first I thought this was just a float charge because my batteries were full. I used a hydrometer to measure them 4 days ago and state of charge was indeed at 100%.

Today I take a hydrometer reading and they're closer to 75%, but voltage from the charge controller is only 13.2V or so despite decent sunlight. I disconnected the charge controller and fired up the gennie and the voltage immediately jumped above 14.5 when I plugged in the Iota. After 20 mins it steadied out around 14.1.

So it appears to me the charge controller is not working correctly. Or maybe some other problem? The panel is undersized for the batteries, but my understanding is that the voltage should still be well above 14 if the batteries' SOC is 75%, but the amps will be low due to the undersized solar panel. Is this right?

I plan on expanding the system later this year and getting a Tristar TS-45 or a Xantrex C40. Maybe I should move this purchase up the priority list? Or should another solar panel be at the top of the list?
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #2
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    Re: Problem with low voltage from charge controller

    Welcome, sad to say but I would bet on the CC being a dud unless you can change the charging settings to be like the iota.
    Can you afford a Morningstar SS-10 Solar Charge Controller 10 Amp, 12 Volt
    http://www.solar-electric.com/ss-10.html

    It will handle the ~ 9 - 10 amps and do a much better job on the charge side. http://lib.store.yahoo.net/lib/wind-sun/sunsaver.pdf
     
    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
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #3
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    Re: Problem with low voltage from charge controller
    westbranch wrote: »
    Welcome, sad to say but I would bet on the CC being a dud unless you can change the charging settings to be like the iota.
    Thanks for the welcome. The charge controller is somewhat programmable and I think I've deciphered the Chinese-English pidgin that the directions are written in---I checked the settings last weekend and it should be right for the Trojans but I might try jacking up the voltage settings to see if anything happens.

    I got the panel and controller last year and my recollection is that it regularly charged above 14V with my old Sprinter AGM. It's been knocked around a bit and stored in less than ideal conditions in a move I made since then, maybe it was damaged.
    Can you afford a Morningstar SS-10 Solar Charge Controller 10 Amp, 12 Volt
    http://www.solar-electric.com/ss-10.html

    It will handle the ~ 9 - 10 amps and do a much better job on the charge side. http://lib.store.yahoo.net/lib/wind-sun/sunsaver.pdf
    Right now I'm comfortable making another $200-$300 investment in my system, which I'm thinking I'll either spend on either a Morningstar PS-30M or PS-45 controller. By summer I'd like to get at least 2 more panels, maybe 3. And maybe two more Trojans.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #4
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    Re: Problem with low voltage from charge controller
    Plowman wrote: »
    Here's my problem. Using the Watts Up meter over the last week, I've only seen 13.0-13.6V or so coming from the charge controller (the meter is installed between CC and batteries). At first I thought this was just a float charge because my batteries were full. I used a hydrometer to measure them 4 days ago and state of charge was indeed at 100%.
    Sounds like at this time they were in float or close to it.
    Plowman wrote: »
    Today I take a hydrometer reading and they're closer to 75%, but voltage from the charge controller is only 13.2V or so despite decent sunlight. I disconnected the charge controller and fired up the gennie and the voltage immediately jumped above 14.5 when I plugged in the Iota. After 20 mins it steadied out around 14.1.
    Sounds at this point they haven't gotten out of bulk.
    Plowman wrote: »
    So it appears to me the charge controller is not working correctly. Or maybe some other problem? The panel is undersized for the batteries, but my understanding is that the voltage should still be well above 14 if the batteries' SOC is 75%, but the amps will be low due to the undersized solar panel. Is this right?
    NO!

    It could be working properly, You have a panel that can produce maybe 8 amps(VMP on these DMSolar panels is around 19V), and likely producing closer to 6 amps on an PWM charge controller in the heat, and your drawing roughly 20 amps (not sure how your concluding this or at where your measuring, produced AC wattage doesn't include inverter inefficiency perhaps 80% so you might be drawing 25 amps off the battery bank. What's the weather been like? a little cloudy lately?

    The progress of voltage when charging batteries should be a gradual increase in voltage in the bulk stage until the battery reaches 80-90%, then an absorb stage when the voltage is maintained at a safe level while the batteries 'top off' while in this stage the batteries slowly absorb less and less amperage until topped off. then the charge controller reduces the voltage to a float level. There is great info in the Batteries FAQs!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Problem with low voltage from charge controller

    I don't think anyone has mentioned it specifically but those Trojans are 225 Amp hours and are not going to be properly charged from a single 158 Watt panel. You need about 400 Watts of panel to do the job. If you don't keep them up with the gen & Iota they will be money down the drain soon. And use a hydrometer to check the specific gravity; don't try to guess state of charge based on Voltage.

    Needless to say that no-name controller has to go. You've spent good money on those batteries and need to protect the investment.
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #6
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    Re: Problem with low voltage from charge controller
    Cariboocoot wrote: »
    I don't think anyone has mentioned it specifically but those Trojans are 225 Amp hours and are not going to be properly charged from a single 158 Watt panel. You need about 400 Watts of panel to do the job. If you don't keep them up with the gen & Iota they will be money down the drain soon. And use a hydrometer to check the specific gravity; don't try to guess state of charge based on Voltage.
    I mentioned it at the end of my overly long initial post. The too-small panel shouldn't affect the charging voltage, though, should it? Won't it just limit the incoming amps?

    My plan is to get two more panels, which would give me 474W, but can't really afford it for another month or so.
    Needless to say that no-name controller has to go. You've spent good money on those batteries and need to protect the investment.
    Agreed. I've decided to get a Morningstar PS-30M. I need a better controller and a better meter, and the PS-30M seems to fit both bills. It also looks like I can attach my computer to the PS-30M and download data, which will be really helpful in learning how to properly manage my little system.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Problem with low voltage from charge controller
    Plowman wrote: »
    I mentioned it at the end of my overly long initial post. The too-small panel shouldn't affect the charging voltage, though, should it? Won't it just limit the incoming amps?

    If the panel's Vmp is above 17.5 it should be sufficient to reach proper charging Voltage.
    But the charge controller may be interfering. Trojan recommends 14.8 Volts for Absorb on these batteries, and the controller may limit the Voltage to less than that (as well as having o temperature compensation).
    My plan is to get two more panels, which would give me 474W, but can't really afford it for another month or so.

    Good. In the meantime an occasional full charge from the Iota is in order.
    Agreed. I've decided to get a Morningstar PS-30M. I need a better controller and a better meter, and the PS-30M seems to fit both bills. It also looks like I can attach my computer to the PS-30M and download data, which will be really helpful in learning how to properly manage my little system.

    The PS-30 is a good controller, but it has the Voltage limit problem. The setting for flooded cells is only 14.4 which is insufficient for the Trojans. It does have an EQ setting of 14.9 so you could get away with it by doing regular corrective EQ's.
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #8
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    Re: Problem with low voltage from charge controller
    Cariboocoot wrote: »
    The PS-30 is a good controller, but it has the Voltage limit problem. The setting for flooded cells is only 14.4 which is insufficient for the Trojans. It does have an EQ setting of 14.9 so you could get away with it by doing regular corrective EQ's.
    Dang it. Any other suggestions for charge controllers and meters within the same price range?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: Problem with low voltage from charge controller
    Plowman wrote: »
    Dang it. Any other suggestions for charge controllers and meters within the same price range?

    Not off hand. You may have to spend $40 more and get the TriStar 45 if you want Absorb at the recommended 14.8 Volts. http://www.solar-electric.com/trts12vochco.html
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #10
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    Re: Problem with low voltage from charge controller

    What about that new Kid Controller? I know it's MPPT but might be worth it?
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
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    Re: Problem with low voltage from charge controller
    jcheil wrote: »
    What about that new Kid Controller? I know it's MPPT but might be worth it?

    It's $285. Probably not worth it.
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #12
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    Re: Problem with low voltage from charge controller
    Cariboocoot wrote: »
    Not off hand. You may have to spend $40 more and get the TriStar 45 if you want Absorb at the recommended 14.8 Volts. http://www.solar-electric.com/trts12vochco.html

    I was considering one of those, looks like that's what I'll have to get. Without the meter it's in the same price range as the PS-30M. I have my panel mounted on a cargo trailer, in which I have the gennie, batteries, etc. There's room enough on the roof for four 158W panels, which would be perfect for the 45 amp controller.

    Don't think I can afford to buy one with a meter, I'd rather put that money towards more panels, so I'll have to figure something else out in the mean time. Maybe a cheap voltmeter on the battery + a clamp meter to occasionally measure incoming amps? My Watts Up meter only has what looks like #14 wires, not big enough to use between the charge controller and batteries with more than one 158W panel.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
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    Re: Problem with low voltage from charge controller

    Maybe a MidNite battery meter http://www.solar-electric.com/mnbcm.html and some diagnostic tools in case the meter says something's wrong?
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #14
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    Re: Problem with low voltage from charge controller
    jcheil wrote: »
    What about that new Kid Controller? I know it's MPPT but might be worth it?

    I looked at those, be nice to have MPPT but with the price differential between it and the Morningstar PWM units, I could almost buy another panel.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
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    Re: Problem with low voltage from charge controller
    Plowman wrote: »
    I looked at those, be nice to have MPPT but with the price differential between it and the Morningstar PWM units, I could almost buy another panel.

    Yes: the MPPT type controllers don't really come into their own until you get over 400 Watts (when you can buy GT style panels at about half the cost of standard panels and the $ difference on the panels pays for the more expensive controller).
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #16
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    Re: Problem with low voltage from charge controller
    Plowman wrote: »
    Don't think I can afford to buy one (Tristar 45) with a meter, I'd rather put that money towards more panels, .

    You can always purchase the meter for it at a later time. I've done that.
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #17
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    Re: Problem with low voltage from charge controller
    Plowman wrote: »
    Right now I'm comfortable making another $200-$300 investment in my system, which I'm thinking I'll either spend on either a Morningstar PS-30M or PS-45 controller. By summer I'd like to get at least 2 more panels, maybe 3. And maybe two more Trojans.

    Careful - Flooded batts like to see anywhere from about C/12 minimum current to about C/8 max, where "C" is the 20hr ah rating. Too low a current, and the electrolyte stratifies. Too high, and damage occurs. Page 12 of the T105 users manual shows the cycle, and mentions using anywhere from 10 to 13% of total capacity.

    So yes, you need more panel, but if you just tack on more batteries, you can easily slide under the C/12 typical minimum to prevent electrolyte stratification unless you plan your panel needs right.

    The amount of panel power you need also depends on the solar insolation hours at your location. These differ from just sunrise-to-sunset hours!:

    http://www.solar-electric.com/solar-insolation-maps.html

    Ie, in Alaska you may need 10 times the panel power you'd need in Arizona! Calculating this means figuring out how much power you draw from the system daily, and figuring out if you have enough time and panel wattage to actually charge the batteries, and not just cycle them at a low state of charge all the time.
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #18
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    Re: Problem with low voltage from charge controller
    PNjunction wrote: »
    Careful - Flooded batts like to see anywhere from about C/12 minimum current to about C/8 max, where "C" is the 20hr ah rating. Too low a current, and the electrolyte stratifies. Too high, and damage occurs. Page 12 of the T105 users manual shows the cycle, and mentions using anywhere from 10 to 13% of total capacity.

    So yes, you need more panel, but if you just tack on more batteries, you can easily slide under the C/12 typical minimum to prevent electrolyte stratification unless you plan your panel needs right.

    The amount of panel power you need also depends on the solar insolation hours at your location. These differ from just sunrise-to-sunset hours!:

    http://www.solar-electric.com/solar-insolation-maps.html

    Ie, in Alaska you may need 10 times the panel power you'd need in Arizona! Calculating this means figuring out how much power you draw from the system daily, and figuring out if you have enough time and panel wattage to actually charge the batteries, and not just cycle them at a low state of charge all the time.

    Yeah, after thinking a bit more about it I don't think adding more batteries will work. I only have room for four 158W panels, not enough to reliably charge four T-105s. Three panels + my two T-105s seems like a pretty good match. That would be C/8.9, or 11.3% of battery capacity.

    Back to my OP, I just ordered a Morningstar TS-45 charge controller to replace my cheap Chinese controller. Next step is to get two more panels.

    Thanks everyone for the help.
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