Needed upgrades/repairs off grid system

Newb here but been doing home power for about 9 years. Found this place and think it’s pretty fantastic.. When I started doing the home solar thing there weren’t to many forums that could provide information on solar powered off grid systems. There has definitely been interest in the grid tie systems lately on Southern California.

Anyway the reason for starting this thread is that I’m about to need another set of batteries for the system and am looking for some other things.

Anyway the system,

Single Trace SW4024 mounded on the Trace dual panel. Has breakers for 2 solar panels, main battery breaker, aux 15 amp, and a generator transfer switch.

One solar array, older Zomeworks Tracker, 12 British Petroleum BP90s 90 watts 30 amps peak

One solar array, UF120 Zomeworks Tracker with early start, 12 Photowatt PW1000s (purchased at a discount as they only produce 95 Watts) 32 amps peak.

2 Trace C40 charge controllers

Onan NHD 6500 commercial RV generator configured for LP. Set to auto-start on low voltage.

16 Trojan L16Ps wired for 24 volts.

This system powers a 3000 sq ft home with washer, dryer, fridge, computers and TVs so the system is utilized everyday. The generator typically doesn’t run during the summer but maybe once a month. With the single array, it averaged about 700 hours a year, with 2 it dropped to about 350. It’s got about 4400 hours on it now.

Originally the system only had one solar panel with the BPs and 12 Trojan L16s. Due to a mishap, the batteries were over charged and pretty much toasted.

About 3 years ago I replaced the fans in the SW4024 as one had died and the other was loosing it’s bearings. Found the fans at a surplus supplier and bought a couple extra sets.

I suspect that this time the batteries were not equalized on a regular enough intervals or they are just worn out. Lately 5 batteries have shorted cells and the system is limping along on 2 banks.

OK, now for the questions.

1. What is the probable cause of the batteries demise? Use? Not equalized? Cycle too deep before recharge.. The startup voltages on the inverter were set to 24.6V/24 hr, 23.6V/2 hr, 22.6V/15min starts. Max charge is set to 29V

2. What’s a good replacement battery? “Flooded Wets” seem the preference. Don’t have any problem with another set of L16s.. I found a local place where I can get them for about $320 a piece. Will have 16 to unload. Don’t have to do any new wiring. Would like to have them last longer.

3. I’ve seen the MX60 controller mentioned here as an upgrade to the C40s. With a little luck they might be able to help the panels produce more power. The Photowatts are wired for a max working voltage of 34 and the BPs set for 37. Would I need to wire these for higher voltages or will the controllers work well at these voltages?

4. The Santa Ana winds topped 50 mph during the first night Witch Creek fires started. It blew off the early start loop on the second array. Is there someone that can get parts for these things? Need a new set of balance tubes.

If you got this far thanks..


  • BB.BB. Super Moderators, Administrators Posts: 28,142 admin
    Re: Needed upgrades/repairs off grid system

    Just a couple observations--I think you are one of the experts here now! Nice system...

    The battery life you have (~9 years) and multiple failures--it does not sound bad for a well used system... If the wiring is OK, and the maintenance was not too bad for you--purchasing the same size/type batteries again would probably be a good thing... Your other option would be to purchase larger batteries (forklift or other large cell batteries) that may give you a longer life. But, in any case, put this in a spread sheet and do this on price / year (twice as expensive batteries that last twice as long is a wash--and in the end may cost you more because you had to pay twice as much money upfront--instead of earning interest on it).

    You did not say how you monitored your battery bank (hydrometer or battery meter)--but see if any of these types of battery monitors would interest you. IMHO (In my humble opinion), these battery monitors are the best way to ensure that your batteries are charged/discharged correctly day in and day out (generally, avoid using more than 50% of capacity, and recharging quickly--ideally within one day or so to reduce sulfation problems). Using a hydrometer is a good follow up--but you can't really use it too often (loss of fluid, contamination, just a pain in the butt). Also having an accurate DVM (for voltage measurements) would not be a bad idea just to make sure that everything is charging the batteries correctly.

    If your current charge controller does not have a battery temperature sensor, it would be a good idea to get one (or you may need a new charge controller with the RTS/BTS option).

    You probably are already pretty conservative on your power usage--but getting a Kill-A-Watt meter for ~$30 so you can watch your major power consumers (fridge, freezers, home entertainment, computers/printers/etc.) will help keep your usage from creeping up--and notify you if your fridge/etc. is starting to have problems (i.e., low freon/high energy usage).

    And MX-60 class of controller (MPPT) would be a very nice upgrade to your C-40's... Your Vmp minimums, as long as they are over 33 volts (equalization + 2 volts for controller voltage drop) or so, would work fine with your MX-60's. However, you would probably like to rewire because the MX-60's can controller higher currents than the C-40 (possibly fewer MX units to purchase). The MX-60's can harvest more power than the C-40's--but in warm weather the increases are usually not huge. It is possible (depending on your exact setup) that you can combine to C-40's into on MX-60 (I believe that MX-60 can be set to ~70 amps maximum)

    I have never used (or needed) a tracker in my short "solar lifetime", but ongoing maintenance has always been a big problem. At this point, if you cannot find spare parts for your existing system (or find conversion parts)--you should consider changing it to a fixed mount and adding additional panels (which are, typically, cheaper now-a-days).

    From your experiences, what worked well and what didn't in your setup--you have a large system with "lots" of experiences--I am sure!

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Needed upgrades/repairs off grid system

    i think the same batteries are fine unless you think you need more capacity. more items running could demand more from your batteries making such a move worthwhile and keeping the batteries from dropping below 50% is very important in keeping battery life. i do have to caution you that under your present system of pvs that you are charging at about a 3.9% rate and that is a bit on the low side, but doable if it can be free to charge without loads being present that would drop the charge rate below 3%. this could be problematic for you because that low charge rate represents alot of time in hours for recharging your battery bank. imho your bank may have lasted longer if more pvs were used to overcome the sulphation that most likely occured due to a slow charge rate. any increase in battery capacity will warrant more pvs without question unless you wish to run the genny more often.

    i see the onan supplements some of your power too and we don't know at what voltage you have it set to kickon. that setpoint may be upped somewhat to prevent some sulphation occuring. i do hope you don't have it set too low as 10.5v is considered 100% dod or simply dead. i don't remember the 50% voltage as i use a different type of battery and maybe somebody could chime in with that for you.

    as to an mppt controller you have a large enough system to use one for sure and know that it doesn't make a pv produce more power, but it recovers a small portion of the power normally lost in the act of charging and can be typically around 10%. using the battery temperature sensors also i believe to be a must as the charge voltage of the batteries must be adjusted to help prevent over or under charging. the bts may add a bit of life to your batteries as well. if going with the mppt controller like an mx60 or xw60 the current is set and and don't want to be over 75% of the rated output current (normally up to 48amps input) for the input so this means rewiring the pvs you have for a higher voltage to keep the current within the parameters needed. a 24v pv setup would work with the controller (1 controller needed for all of your pvs btw). you don't have to stop there if you wish as you could wire for 36v as well and the controller will convert this down to your 12v battery bank voltage. the wiring loses can be lessened with higher voltages, but efficiencies for downconverting from the controller will drop slightly the farther up and away from the battery voltage you go.

    i think that covers all except your 4th question. i'm not quite sure what you are saying there. are you talking a wind generator such as the darius? (spelling)

    one more point i forgot about. battery prices have risen sharply so be prepared for sticker shock.
  • System2System2 Posts: 6,290 admin
    Re: Needed upgrades/repairs off grid system

    Bill, Niel

    Thanks for the replies. I’d started to respond to Bill last night and the system shutdown to low battery voltage so I gave up for the night. The circuit breakers had tripped on the generator not sure why but I was trying to get a lizard out from the inside and may have tripped it.. The generator likes to collect mice and lizard and cook em… :blush:

    So 2 sets of batteries in 9 years is OK? Probably would be closer to 11 if I didn’t smoke the first. The system has temperature compensation on the controllers and the inverter when running in charge mode. The issue I had where I killed the first set was that the inverter/charger sensor came off the battery and did not provide an accurate reading of battery temperature. The sw4024 though the battery temps were about 50F (cold day) when they were really about 90F.

    Bill, I like the idea of the Kill-a-Watt meter. Definitely need to monitor the fridge. I do suspect that it’s part of the problem, that and the fact that my son likes to gaze at the food (and eat it).:D

    Generally the way I monitor the battery bank is to eyeball the bank voltage and gauge whether current is flowing into the bank or out. Other than that it’s up to the SW4024 to monitor the voltage.

    Niel, I probably wasn’t clear enough on the battery voltages.. The “generator” startup voltages on the inverter were set to 24.6V/24 hr, 23.6V/2 hr, 22.6V/15min starts. Shutdown occurs at 22V. The sw4024 does not monitor current while checking the voltages but uses the above voltage / time to figure out the battery state. While 24.6 is about 65% for 4 L16s in a row. The 2-hour limit would be 30% and 15 minute would be less than 10%. I’m not sure the 2-hour and 15 min are indicators of float voltage but more a loaded voltage and the inverter does not know what the charge controllers are doing during this time. It’s possible to have a static state on the batteries at the lower voltages if the panels are providing power and the inverter is using it. I’m thinking to up the 2 hour and 15 minute voltages.

    Also, since the inverter can charge at the same time say from a low voltage start in the morning. Sun comes up, panels output 60 amps and the inverter is adding another 100.

    The MX60..

    Now if I understand the specs correctly. I’ve got too much current for only one MX60 since the max output is 60 amps and I have the potential for say 62 amps all ready. Niel, I think that I understand how the MX works. It tries to optimize power transfer where the C40 is nothing more than a smart switch.. The C40 lets the solar panels set the current but switches off when the battery voltage gets too high. The MX60 tries to optimize power output of the panels and convert the additional power to current at the battery voltage. It’s not much more than a high efficiency switching power supply. In that way, it does pull more power out of the panels.. I guess I didn’t word it quite right.

    Bill You said there is a potential to use both the C40s and a MX60? Not sure I understand how to hook that up. I may try one on the BP array first just to see how many watts I can pull out. The C40s give a power output on the display. The BPs will max at about 750 (batteries at 27 volts) and 800 photowatts. With these arrays being a 1080 and 1140 watts, I was hoping for more than 10%. Not much though..


    Question 4 was about the Zomeworks track rack. These are non-electronic solar trackers. They utilize Freon in tubes with reflectors at the ends of the racks to track the sun. The early start tube is a tube that hangs down on the West side tube and heats the Freon quicker on the morning so that it can pick up the sun quicker. With the early start tube broke off, I lost the Freon and the tracker don’t. It’s a factory-sealed unit so I expect I’ve got to buy the tubes.

    You are right about the sticker shock. Paid $196 for the L16Ps 5 years ago. Now they range from 300 to 400. :cry:

  • BB.BB. Super Moderators, Administrators Posts: 28,142 admin
    Re: Needed upgrades/repairs off grid system

    There was a typo in my C-40 to MX-60's... I intended to say convert two C-40 arrays into one MX-60 array.

    From the MX-60 manual (PDF file):
    The largest PV array that can connect to an MX60 should have a rated short-circuit current of 48 amps STC (Standard Test Conditions).
    The default charger output current limit setting is 60 amps and is adjustable up to 70 amps. At 70 amps, a 70A or 80A breaker must be used between the battery and the MX60.

    And even if you have 62 amps off output (or input), and the limit is set to 60 amps--how often would you get the maximum amperage (hours per day, or minutes just a few times per month/year). I believe the MX-60 simply limits excess current to the 60/70 amp limit--no damage will occur if the array is slightly oversized in current/power. The savings in not purchasing a second controller to gain that extra 2 amps is pretty expensive...

    You can connect the MX-60 in parallel with the C-40 (for example, running to arrays with different voltages/current panels, or fixed vs tracking arrays). Just properly connect both to the battery bus and each will manage the batteries to the their particular programed set points (just like the generator/battery charger does too). Depends how closely you can match voltages and/or currents between the different brands/models of solar panels as to the question is this a one or two controller solution.

    Do you have utility power available--or are you off-grid by choice, or by the fact that it would cost too much to run utility lines to your home?

    If you have utility lines available (at potentially reasonable prices), you could see if grid-tied solar would be a cost effective option (vs battery replacements and fuel costs for the generator).

    Working the pricing out--I usually come somewhere to $0.25 per kWhr (with CA rebates, down towards $0.15 per kWhr) for grid tied, and probably $1.00 per kWhr (huge number of assumptions made--both assuming retail prices, labor, etc. fuel/battery replacement costs, etc...)... Running a Grid Tied system with a small battery/generator backup system may be more cost effective (even with charges for utility connection) than maintaining a pure off-grid system... Just a suggestion/question.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Needed upgrades/repairs off grid system

    there is no need to go over the set current of 48amps as all that is needed is to rewire the pvs for a higher voltage since it is not voltage limited to 12v. i do believe they state that due to nec rules and yes the adjust for 70amps out will also adjust the input max to 56amps and is still too far above to use the pvs in a 12v arrangement. it isn't that the controller can't handle it, that i agree with you on.
  • System2System2 Posts: 6,290 admin
    Re: Needed upgrades/repairs off grid system

    These are good suggestions.. FWIW, I see 32 amps on the one array pretty often. and 30 on the other not so much but I probably need to go in and clean the panel connections. Now assuming I can get say, 10%, more power out with the controller. Would that mean that I'd get say 35 amps out of one and 33 out of the other at 27 volts? Also since the panels are on trackers they see peak probably for 4 hours on a clear day. If the voltage drops to say 25 while the clothes washer is running or the batteries are low in the morning say at 10am does the current go up even higher?

    Neil, Not sure whaty you mean about 12V. Do you mean 24V. This is a 24V system.. When it was installed I had someone else do the system and the first question I aked was why they didn't use 48 volts. The builder was more comfortable with 24 over 48 and mumbled something about GFI. If the Trace ever rolls over and dies. I'll probably go 48V.

    When it's all said and done I'll be paying probably somewhere between 50 cents to a dollar a KWH. I don't have access to the grid and don't get the California rebates. Just ordered 16 more L16Ps...:cry:

    I expect I will try the MX and see how efficient it cam make the panels. I'd be a little concerned about running the thing at it's max rating though,,, but then I guess that's what warrantees are for.

    This is all good stuff. I appreciate your time.

  • BB.BB. Super Moderators, Administrators Posts: 28,142 admin
    Re: Needed upgrades/repairs off grid system


    The MX-60 is just a buck converter (type of switch mode power supply) that drops the input voltage down to the battery voltage, and inversely increases the current (basically Vmp*Imp=Vbat*Ibat less a few tens of watts for power supply overhead and other losses).

    So, how much you can gain really depends on the Vmp (Voltage Maximum Power) of your solar panels vs battery voltage...

    For example, assuming Vmp=17.5 volts per panel @ 5amps (and assume the MX-60 has 15 watts of tare losses--probably close enough for this example)...

    2 x 17.5 volts * 5 amps - 15 watts tare = 160 watts available power from panels

    160 watts / (28.2 Vbat + 2 volt controller drop) = 5.3 amps using the MX-60 or about a 6% gain...

    That is not much gain, but remember that Vmp is very temperature dependent, and Vmp drops as temperature rises--so it is possible that your current drops on hot days with cool batteries because the panel Vmp voltage is not high enough to charge (or equalize) your battery bank. With PWM chargers, your only choice is to raise the voltage (different panels or put a pair in series--which in itself is a waste of almost 50% of the potential panel energy...

    But to finish the question, assume your Vbatt is 25 volts...

    160 watts / (25.0 Vbat + 2 volt controller drop) = 5.926 amps

    Or, almost a 19% increase in current over the 5 amps Imp that a PWM converter can supply.

    When you look at solar panels and the voltage range that Vmp can transition over (-0.0444 V/°F for a BP 80 watt panel I could find the specs. for)--or the difference between 77F cell temperature (at STC) and the 168 °F cell temperature on a hot day no wind (maximum guess) drops your 17.6 Vmp to (-4.04 volts) 13.56 volts

    2x13.56=27.12 volts maximum Vbatt (round 100F day, no wind)--probably less than you really want to charge your battery bank too (29 volts max from your first post)...

    So, ideally you put, at least, 3 BP90 panels in series, maximum available voltage to your battery is assumed to be:

    3*13.56 - 2 volt MX-60 drop = 38.7 volts (plenty to charge the battery). Using 5 amps as a nice round Imp number (just to be consistent with above example):

    13.56 volts * 3 panels * 5 amps * 93% eff = 189 watts

    189 watts / 29 Vbatt = 6.5 amps (charging your battery to 29+ volts available on a very hot day--when stock array could only charge to 27 VDC before the current drops to zero amps).

    And, just to close the example, assuming a cool day (77F panels with default 17.6 Vmp, 5 amps and 93% efficient MX-60 charge controller)

    17.6 volts * 3 panels * 5 amps * 93% eff = 245.5 watts
    245.5 watts / 29 Vbatt = 8.4 amps on cool day (windy, below 70F)...

    For me, it is wanting a Solar Array to provide "full power" over a wide range of temperatures that keep sending me back to the conclusion that for any system over 400 watts should be an MPPT type system for optimum performance... In hot climates, standard "12 volt" solar panels just don't have enough head-room to supply batteries (and wiring losses) with optimum current--and in cool climates/days, the extra voltage is totally wasted with PWM controllers.

    (for smaller systems, less than 400 watts, the energy lost in current MPPT charge controllers breaks even or even consume more energy than the MPPT function can wring out of the panels--assuming that Vmp on a hot day is still sufficient to charge the battery bank).

    Am I getting a bit repetitive here or is this helping to keep things clear? :cool:

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • halfcrazyhalfcrazy Solar Expert Posts: 718 ✭✭✭
    Re: Needed upgrades/repairs off grid system

    i think i would raise the generator start voltages. letting it set at 24.6 for 24 hours may be the early demise of the batteries?
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Needed upgrades/repairs off grid system

    i did suggest that to him already. i do thoroughly agree it could be raised a tenth of a volt or 2. i think i gave the example to him before of a dead 12v battery being at 10.5v and a 24v battery is dead at simply twice that or 21v.
    sorry about the 12v thing as i get mixed up on what i type sometimes when focussed on other particulars. now the problem is the current and your installer was refering to the system at 48v being in the "high voltage catagory" and thus nec rules, but fear not as with an mx60 reset for 70amps and your pvs wired for 36v you should be good to go i would think. you would have more current manuvering room if wired for 48v, but seek the advice from your installer on all of these proposed moves if you can. gfi's aren't necessarilly a bad thing either and some lightning protection devices are good to have too, but i don't know exacting circumstances for your system from a brief encounter over the internet. i just throw possibilities out that may or may not be good for you. you ultimately decide and are responcible for your decisions. if all this on the requirements for 1 mppt controller is too much of a pain for you, you can bite the bullet and opt for 2 mppt controllers with associated accessories like mate and hub or the equivalent from other companies. it costs more, but the pv system stays the same and is expandable.
  • System2System2 Posts: 6,290 admin
    Re: Needed upgrades/repairs off grid system


    I figure the MX60 was a buck converter only set up to maximize VxI in to deliver max current (or what ever is programmed).. I assume that what MPPT is..

    I think I understand the numbers but I do wonder where the 2 volt drop for the inverter came from that you add to the calcs when doing effeciency calcs. Is it a fixed loss or just what the MX60 needs as supply voltage to run? You'd hope it's not diode losses and that Outback used synchronous driving of mosfets to minimize switching losses. The buck needs some sort of higher voltage to do anything as it's driving current from source to load through an inductor (IIRC). Looking the MX60 manual and it states that peak effeciency for the MX60 with 26.5 output is 40 volts. It does make sense to wire the arrays to a higher volage from a IR loss point of view.

    "Or, almost a 19% increase in current over the 5 amps Imp that a PWM converter can supply."

    I assume you mean "that a typical charge controller can supply", I assume PWM is a switching controller.

    It's does seem worth while to boost the wired output of the PV arrays.

    One thing the MX60 manual says is that the max array power for one MX60 should be 1600 watts. Still sounds like trying to run 2220W worth of panels might be stressing things a little..

    I appreciate the calcs on the panels. I'm not sure I'd should be concerned about temps when hot (maybe I should) as the batterys seem to stay up during the summer when it's hot and sunny. They seem to reach the float voltage during the day. Only gets over a 100F maybe 2 weeks out of the year.. The more inportant issue to me is that during the winter days are shorter and available charge time is less. In fact it might be worth while to start the genset periodically to ensure the batteries reach full charge.

    Another issue is that the photowatts and BP run at slightly different voltages. The BP has a vmp of 18.5V @ 4.9A and the photowatts are 17V @5.6A. I'd guess some power may be lost but maybe not much. The photowatts are currently wired so each panel outputs 34 volts so I'd have to reconfigure them to output 17.

    Currently I see about a 2 volt drop from a photowatt panel to the charge controller with the controller reading 25amps output. There's 50 watts up in heat.... :roll: Double the voltage, half the drop. 25 more watts..

    I will boost the gen start voltages when I install the new batteries and run a full charge into them once installed. I suspect that due to the up in battery bank from 12 370 AH trojans to 16 390 ah trojans that output impedance of the bank is lower so the 16 actually reached a lower state of charge than the 12 before the gen set ran.. Expensive mis-calc on my part.


    You bring up lighting supression. I don't see any evidence of such devices on the current system. Wounder what should be added and how effective it is.

    Thanks for taking the time to add more examples. I think I've got it but this head can be a little thick.

  • BB.BB. Super Moderators, Administrators Posts: 28,142 admin
    Re: Needed upgrades/repairs off grid system

    I don't have an MX-60 controller--but I just estimated that you need 1-2 volts of forward bias to get current flowing through (any) controller... If you have equal voltages on both side of a controller--no current can flow (with switched or buck converters).

    PWM controllers are switched--but don't have any energy inductors as in the buck/boost/buck-boost topology (that I have heard of--I have not taken any apart--so that is a guess on my part). So, PWM, at maximum current flow are just a closed switch (100% on). And, from the little I have seen, is the typical type of non-MPPT charge controller (other than the very small charge controllers which may be an analog 3-terminal type regulator).

    Once the charge controllers start to regulate (cutting back on voltage/current to the batteries because they are getting full)--A PWM or MPPT type controller will be using less than full power from the panels and the differences in power/efficiency to the batteries becomes a don't care.

    From what I have read here (mostly from Solar Guppy), MPPT algorithms vary across manufacturers... Some just assume a certain voltage drop from Vopen-circuit, others adjust current up and down and find peak power every few-15 minutes... And others yet (typically, Grid Tied inverters) are supposed to continuously adjust for maximum power from the panels.

    Regarding panel temperatures--Those "low" voltages are certainly worst case that can be expected from very high ambient temperatures and poor air circulation and a guess on the panel model number/Vmp and show how an MPPT type charge controller can support a wider range of environmental conditions--if you don't need it--that is wonderful.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,009 ✭✭✭✭
    Re: Needed upgrades/repairs off grid system
    bwoltz wrote: »
    Currently I see about a 2 volt drop from a photowatt panel to the charge controller with the controller reading 25amps output. There's 50 watts up in heat.... :roll: Double the voltage, half the drop. 25 more watts..

    Uh, that's double the voltage, half the AMPS.
    I'm afraid the charge controller will always have loss, it's an active device inline with your main current flow.
    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

    gen: ,

  • System2System2 Posts: 6,290 admin
    Re: Needed upgrades/repairs off grid system


    Thanks for the additional info.. I suspect that some of my confusion is based on how the terms are used in respect to solar systems as opposed to general eletronics. I would have thought that MPPT could be called a PWM controller since it is more than likely using pulse width to set the current. In general, switching power supplies have a PWM controller and inductors or transformers. In led or motor control PWM typically don't need and inductor though motors are inductors of a sort. In solar systems PWM can imply a current spiking to help with plate sulfation, maybe some other applications also. Thanks again.

    You are right, I was carrying the theory a little further,doulbe the voltage, half the amps, half the IxR drop. All controllers will have a loss, the better ones should have less. Resistance and diodes are not your friends here...8)

  • BB.BB. Super Moderators, Administrators Posts: 28,142 admin
    Re: Needed upgrades/repairs off grid system


    Same confusions that I had when I first started looking at Solar a few years ago... Some of this is probably caused by marketing types "updating" their charge controllers by updating their glossies. 8)

    In reading around (like LED Flashlights), PWM seems to now indicate, for the most part, must a switch opening and closing--and this does save some power losses (and controller heating vs analog pass transistor simply dropping voltage and generating local heat), most often you have to read further to really understand the details of the hardware inside.

    For example, flashlights are even now using the term "regulated" when, it appears that they are using open loop PWM (switched, no inductors) to just adjust the light levels by changing between 100%, 50% and 25% duty cycles. Not what I would have called regulated--but it is still within the dictionary definition.

    There are few MPPT type, wide input voltage range, solar charge controllers like the MX-60 out there for battery systems. Xantrex has introduced their WX-60--but it sounds like their are still having production issues at the moment.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Needed upgrades/repairs off grid system


    I went to the sponser and bought a MX60 and temp sensor for a good price. Talked to the guy about replacing the gas cartridges for the Zomeworks track rack and he called Zomeworks and got a price of $1000. :cry: He can sell me a complete track-rack for $1400.

    Batteries not in yet.. I've been looking into installing the MX60 on one array but the Trace wiring is a little different. The C40 charge controllers don't have a breaker between the output to the batteries (thay actually go directly to the inverter side of the 250 amp disconnect. Need to add a 60 amp DC breaker to the output of the MX60. I've got a location for the breaker but need to find a Heinemann CD series breaker.

  • System2System2 Posts: 6,290 admin
    Re: Needed upgrades/repairs off grid system

    With the help of my son, we replaced the batteries the day before thanksgiving. System runs much better. Genset only runs a after a coupla days without sun. Today I added the MX60 to the BP array without any mods. Finished at about 3:30 pm and the system are already putting out about 40% more power in the low light. I may buy another for the Photowatt array but will need to rewire the array as their working voltage is only about 34 volts where the BP were good at 37 which is the minimum recomended by Outback. I'd bet the power is at least equivilent to fixing the tracking and for less $$$. It will be interesting to see what the BPs put out on a clear day with the MX60.

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