Solar for my RV - charging problem

RonFitzRonFitz Registered Users Posts: 9
I've installed 185W (2-50w and 1-85w panels) on my RV roof, and using a Morningstar PWM 25A charge controller to charge a Trojan J150, 150 AH Golf Cart Battery. In parallel with the output from the charge controller is a PDI converter which incorporates a 3 stage charger. When connected to 120VAC at a campground or home, the converter is active and charges the battery. When off-grid, the solar provides charging.

Here's my problem: Off grid, the solar charge level never drops below 14.4V. In fact, even on-grid with the solar connected the voltage at the battery is 14.4v. If I disconnect the solar, the converter drops the voltage to a float 13.7v. The specs on the solar charge controler indicate that it too should drop to a float charge level. Could this have anything to do with connecting the output from the solar charge controller in parallel with an inactive converter?

I've already replaced the solar charge controller with a replacement from Morningstar, and have the same issue. I'm about to disconnect the output from the inactive converter to see if that's the problem.

Any ideas.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Solar for my RV - charging problem

    You should not have an issue with shared charge controllers... As you have found, the one with the highest voltage setting "wins". And it sounds like your solar charge controller is the one with the "issues".

    Is this the controller you have?

    Morningstar Dual Battery Charge Controller 25 Amp

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ShadowcatcherShadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: Solar for my RV - charging problem

    On our teardrop I have a 185W high voltage panel a Morningstar MPPT Sun Saver and a Progressive Dynamics converter, so similar but not the same. The PD does not inter fear and according to the techs at Morningstar should not (I asked). You can get the computer interface and be able to monitor and or alter the programing of SunSaver.
  • RonFitzRonFitz Registered Users Posts: 9
    Re: Solar for my RV - charging problem
    BB. wrote: »
    You should not have an issue with shared charge controllers... As you have found, the one with the highest voltage setting "wins". And it sounds like your solar charge controller is the one with the "issues".

    Is this the controller you have?

    Morningstar Dual Battery Charge Controller 25 Amp

    -Bill
    Hi Bill,
    Yes. It's a SunSaver Duo, w/ remote meter and remote temperature sensor.
    My RV was just in the shop to fix a brake problem and while there I had the tech do a load test on the battery. The battery tested bad, which I attributed to overcharging from the solar system. The tech said that it tested at 90 amp hours, far below the spec of 150. The battery was purchased in August. It hasn't seen many cycles. It seems to charge to 13.6v, but under a load of around 3A, it drops to around 12.1v within 15 to 20 minutes.

    Also, the two 50W panels are mono-crystal and the 85W panel is multi-crystal. I don't think this matters, but then I'm not an expert on solar, obviously.

    Ron
  • mike95490mike95490 Solar Expert Posts: 9,359 ✭✭✭✭✭
    Re: Solar for my RV - charging problem

    I think it's unlikely a M.S. controller (and the 2nd one) with only 185W of PV, can damage a 150AH battery. worst it should be able to do, is overcharge it, and you would know that, by having to have added a lot of water. If all the settings are correct.
    Did you disable the Eq setting (if it has one?)
    What are you measureing the voltage with ?

    Never heard of PDI, so, I suspect them :D
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • RonFitzRonFitz Registered Users Posts: 9
    Re: Solar for my RV - charging problem

    MIke,
    The PDI converter is made by Progressive Dynamics Inc. It has an integrated 3-stage charging system called "Charge Wizard" and it's an often recommended converter for RVs. With the converter being used as the charger and the solar charger output disconnected, I'm measuring a float voltage of 13.7 v at the battery terminals. I have a fluke digital meter that I'm using to measure the voltage, and it compares with the readings that I get on the Morningstar Remote Meter.

    The fluid level in the battery is ok, and I haven't had to add any distilled water since the battery was installed in August. I'm going to take the battery back to the dealer where I bought it in hopes of recouping something from the warranty. But, I'd really like to figure out this problem before I replace the battery.

    There are 5 dip switches on the controller. The first 2 select the battery type, one for each battery, either lead acid or sealed - lead acid selected. The 3rd selects the priority for charging, e.g., which battery gets the higher percentage of initial charge current. Since I have just the one battery, I left this set to the factory setting, 90/10%. Switch 4 allows setting custom stage voltage levels. I left this with the factory settings of absorption=14.4 v, float = 13.7v, and boost=14.8v. Switch 5 is for fast PWM or slow regulation, also left at the factory setting.

    Ron
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Solar for my RV - charging problem

    Is this a "maintenance free" battery? Is it a deep cycle battery?

    If the battery is not sealed, I would expect if it was damaged by over charging that you would be adding water at least once per month... If you are not adding water every 2-3 months (standard flooded cell deep cycle battery), I would wonder if the battery is possibly being undercharged.

    Is there some automatic/vampire load that may be pulling the battery below 12.7 volts or so, and causing the charge controller to "fall out" of float mode?

    Also, do you have the solar charge controller wired directly to the battery bus with fairly short and heavy cable? If you share the controller to battery bank cable with other chargers/loads, it can cause the charge controller some confusion.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RonFitzRonFitz Registered Users Posts: 9
    Re: Solar for my RV - charging problem

    Bill,
    Thanks for your help. The battery is a flooded deep cycle golf cart battery (trojan j150). I have not had to add water to the battery since installing it in August. So, I'm probably not overcharging.

    The solar charger output is spliced into the #10 wire that it shares with the converter. The distance to from both chargers to the battery is less than 4 feet. I do have a propane detector that is powered full-time from the battery. I not sure what current the detector draws, but I suspect it is very little.

    I just went out to look at the Morningstar Remote meter. It's a cloudy 45-degree day here in NH. The battery voltage as reported by the remote meter is 14.32v. The solar current is 0.10 A.

    I'm going to disconnect the battery from the RV and charge it with my automotive battery charger to be sure that it is topped off, then reconnect it and re-do the measurements. I can also pull the fuse for the propane detector. I will wire the solar directly to the battery as well. Is #10 adequate. #6 is the max size that the charger will accomodate.

    Ron
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Solar for my RV - charging problem

    Sounds OK... Have you measured the specific gravity of the battery bank?

    Should you turn off the propane detector when the RV is in storage? Who will be there to hear it. And where would the propane come from if the master valve is turned off...

    You might want to check the current to the detector... Older ones actually had a hot filament in them to detect combustible gasses (have no clue about current designs).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RonFitzRonFitz Registered Users Posts: 9
    Re: Solar for my RV - charging problem

    Bill,
    I haven't measured the specific gravity. I need to pick up a tool for that, but that's probably a good idea.

    The detector is new, within the past year. I don't have a switch for it, but I can certainly pull the fuse. There's no need to have it on when the RV is stored anyway.

    I'll follow up on getting the wiring changed between the solar charger and the battery, fuse pulled, and top off the battery, then get back to report the results.

    BTW, Morningstar just delivered another (second replacement) SSD25, via UPS. I don't know why they sent this one, but, since it's here, I'll replace the solar charger again, just to eliminate it as the culprit.

    Thanks again,
    Ron
  • ShadowcatcherShadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: Solar for my RV - charging problem

    Rather than use an automotive charger (most are not automatic or regulated) use the PD and monitor the voltage. For those not familiar with RV converters Progressive Dynamics is well respected and it is made in the US. I was concerned about its use of a 15 min 14.4V equalizing period every 21 hours about this with a a Concord tec rep and he is well familiar with the PD converters and liked them for use with their AGM batteries.
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Solar for my RV - charging problem
    RonFitz wrote: »
    The detector is new, within the past year. I don't have a switch for it, but I can certainly pull the fuse. There's no need to have it on when the RV is stored anyway.

    I found it very easy to install a push button on-off switch right next to our RV's propane dectector. If the trailer isn't being used, the detector is off. Even a wife can operate the switch easily, rather than messing with fuses.

    Our detector has an LED so it's easy to notice whether it's on or off.

    Now, the smoke detector is a different story. I moved it from just outside the bathroom because steam from the shower would trigger an alarm. Even on a bedroom wall, shower steam will sometimes cause an alarm. The wife takes the battery out and puts it into a drawer. I'm not comfortable with that because sometimes it doesn't get reinstalled.

    In our previous trailer I installed a mini-toggle switch on the smoke alarm. That worked but was easily forgotten when the switch was 'off'. I was hoping for a better solution from members here.

    Phil
  • RonFitzRonFitz Registered Users Posts: 9
    Re: Solar for my RV - charging problem

    I'm beginning to suspect that I'm undercharging the battery. Reading some of the other posts in the beginners area about battery size and and pv calculations, I'm concerned that a 150 ah battery may be much more than I should have. Here's my system.

    2-50 w Ramsond mono 12v nominal panels
    1-85 w Solartech multi 12v nominal panel
    connected in parallel, fixed mounted flat to the roof of my RV

    #10 wire approx 12 ft to the Morningstar Sunsaver Duo PWM charge controller.

    #10 approx 4 ft to the Trojan J150 150 ah battery.

    The RV sits unobstructed by trees, etc. at 1100 ft elevation, but the days are getting shorter here in NH.

    I'm still working on system changes mentioned earlier, but still thinking about other causes.

    Ron
  • SevenSeven Solar Expert Posts: 292 ✭✭
    Re: Solar for my RV - charging problem

    Tough questin to answer. You should be seeing between 9.9a and 11.8a of charging current with your current system. That is below the 10% (rough) guideline, but it is above the 5% minimum. How many times has the battery gone dead? If the battery has a problem then your system won't be able to charge it. Not having to add any water seems like undercharging, but without knowing what loads you are putting on it, it is tough to say. If you are getting the battery down close to 12.0v(or less) on a regular basis then you would definetly be undercharging with your system because it would take a couple of days to get it back where it needs to be. If this happens, then it means that your battery could be staying below the 13.6v for prolonged periods, causing an early death. That would explain why it takes such a short time for the voltage to drop. Sulfation doesn't allow the plates to keep a deep charge.
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Solar for my RV - charging problem

    Using PV Watts for Concord NH with solar panels mounted flat to your roof:
    1      1.96     
    2      2.84     
    3      3.80     
    4      4.84     
    5      5.68     
    6      6.08     
    7      5.99     
    8      5.30     
    9      4.08     
    10      2.77     
    11      1.85     
    12      1.52     
    Year      3.90
    
    You are looking at ~1.5 hours of full sun equivalent per day here... Current into your battery bank would be approximately:
    • 185 watts of panels * 1/17.5 volts Vmp = 10.6 amps Imp
    • 10.6 amps * 1.5 hours of sun = 15.9 AH per day of charging current
    Using a generic voltage drop calculator, 10 gauge, 4 feet 10.6 amps gives you:
    • 10 awg; 4 feet one way run; 10.6 amps => 0.26 volt drop
    That is is a bit too much drop. At full recharging current the controller will mistakenly believe that the battery is ~0.26 volts higher than it really is... It will cause the charging system to cut back on the maximum charging current sooner than you would like--and probably making your battery slower to recharge and tossing away power in the middle of the day.

    Normally, I would be suggesting shorter/heavier wire to reduce the voltage drop to ~0.05 volts maximum (or at least 0.10 volt drop).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RonFitzRonFitz Registered Users Posts: 9
    Re: Solar for my RV - charging problem
    Seven wrote: »
    Tough questin to answer. You should be seeing between 9.9a and 11.8a of charging current with your current system. That is below the 10% (rough) guideline, but it is above the 5% minimum. How many times has the battery gone dead? If the battery has a problem then your system won't be able to charge it. Not having to add any water seems like undercharging, but without knowing what loads you are putting on it, it is tough to say. If you are getting the battery down close to 12.0v(or less) on a regular basis then you would definetly be undercharging with your system because it would take a couple of days to get it back where it needs to be. If this happens, then it means that your battery could be staying below the 13.6v for prolonged periods, causing an early death. That would explain why it takes such a short time for the voltage to drop. Sulfation doesn't allow the plates to keep a deep charge.
    Thanks again for the feedback.
    The system was installed in August, panels mounted, new battery, solar charge controller installed. Since then, I've camped a few times, but always with 120vac hook-up, so I really haven't depended on the solar much, except for when the RV was parked at home, disconnected from 120. I've been trying to make the camper independent of the grid for future expeditions. The battery has never been discharged below 12.2V, although it has, when parked at home, spent quite a bit of time depending solely on the solar for charging. Hence my suspicion of undercharging and possible sulfation. The fact that it quickly drops to 12.2V suggests that that's probably the problem with the battery.

    And, considering Bill's input regarding voltage drop and shorter hours of full sun, it looks like I have a couple of options for correcting the problem. The battery has to be replaced for sure... probably drop down to a group 27. Then to avoid problems with a new battery, it looks like I should upgrade the wiring between the solar charger and the battery and/or upgrade the solar charge controller to an MPPT and re-structure the panel layout to connect the panels in series, thus avoiding the need to increase the gauge for the wire run from the panels to the charge controller... probably all of the above.

    Ron
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Solar for my RV - charging problem

    At least, shorten the wiring (move the controller) closer to the battery bank. For 10 AWG wiring:
    • 4 foot run * 0.05 volt drop / 0.26 volt drop = 0.77 feet = 9 inches
    So for a 0.05 to 0.10 volt drop, you are looking at a 9" to 18" maximum run using 10 awg wiring.

    The wire run from the roof to the battery bank is less critical--But as you can see, high current (even 10 amps) at 12 volts is very difficult to send any distance without using crazy heavy copper cabling.

    I hate to see you speeding a bunch of money on new hardware (99% of us here are, first and foremost, cheap), but telling you to add a Battery Monitor (close to ideal), or getting a DC AH/WH meter (only one direction--not battery meter), or even a DC Clamp Meter (good for debugging, no time measurements for AH/WH) is a bit spendy. (in order of my preference).

    But, without knowing the details of your loads (how many amps * how many hours) it is difficult to know the best way to proceed.

    Usually, you don't need to much power for floating a battery in storage (around 1% of battery AH rating). Unless you have loads (like the propane alarm) drawing too much (or even the AC shore power unit discharging a bit when no AC power).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RonFitzRonFitz Registered Users Posts: 9
    Re: Solar for my RV - charging problem

    Here's what I have for loads (w/specs) when I'm camping off-grid:

    12v Norcold DC0040 fridge - spec'd at 2.7/1.35 amps (I suspect that it's 2.7 when running and the 1.35 is in consideration of a 50% duty cycle. So, 1.35a x 24 = 32.4ah - Probably somewhat less in the cooler weather.

    Atwood 8012 II furnace - Fan for propane furnace (when it's cold) 1.8 amps (I suspect that, depending on the outside temperature, the cycle time will be in the range of 60% running, or worst case approximately 12hrs x 1.8a x 0.6 = 12.96 ah, but obviously 0ah in the summer.

    All lighting is LED. Estimated draw is about 3-4 ah worst case.

    12V Water pump, runs only on demand. Worst case, perhaps another 2 ah.

    Propane detector. ??

    Worst case, roughly 50 ah/day. To keep within a 50% DOD, that calls for a 100ah battery, right? And it also means that I should be able to replace 50ah during the day, hmm. I'm not sure this is doable when the weather is colder with the space on the roof. It's not a huge camper.

    Ron
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Solar for my RV - charging problem

    Yep, you pretty much have it down. Add 10 to 20% to your AH used to make up for battery losses...

    Some folks have a pair of 135 watt panels they can stake 50 feet or so from the trailer to get more power and/or better sun.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RonFitzRonFitz Registered Users Posts: 9
    Re: Solar for my RV - charging problem

    I think I have a good handle on what's going on. The bad (well not really that bad) news is that winter camping is not in the cards with the existing panels/layout. The good news is that with about 4 hours of sun, e.g. April - September in NH, and some conservative use of heat, I can be somewhat independent. I'm still going ahead with upgraded the wiring and a shorter the route between the charge controller and the battery. I will probably replace the battery with another 150, and eventually upgrade the charge controller to an MPPT. I expect that the cost will come down a bit over time.

    I can always bring my little Honda 2000i for backup re-charging. It works well, but even as quiet as it is, it still makes noise.

    Thanks for all of your help.

    Ron
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