how to wire battery bank? wire size? log types?

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    It looks like that timer will work (no DC switch ratings?). Set for hours and (7 days * 24 hours/day = ) 168 hour del

    Use a (one or two--For timer and for load) fuse/breaker to protect your wiring from short circuits.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Thank you Bill. 

    If I buy the 6v AGM 210ah batteries (2 of them) and use them for this exclusively fan - then in 4-8months I buy another 4 of these batteries and set up my power system so I will essentially connect together 4 brand new batteries and 2 4-8 month old batteries - is that an issue? 
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    edited October 2020 #64
    Ideally, you want matched batteries (same date/lot, same model, same chemistry, etc.).

    More or less so all the batteries die at the same time and it is easy to jus
    tifyreplacing all at once.

    When you have mismatched batteries, you can end up debugging and replacing part of the bank, and having to do the same thing a year or so later.

    Mixing batteries 6 months apart... Your system will will fine. You will not be able to blame old vs new batteries in the distant future.

    You may have an SG mismatch when the new batteries are installed. But a month or so down the road, they will usually even out as the new batteries cycle.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    edited October 2020 #65
    Perfect thank you Bill. 

    I am now planning the wiring... I will post a diagram for review shortly. I think I will use the bus bars i have: https://smile.amazon.com/gp/product/B07THLYYH3/

    But I need to run a 12 awg from the pos and neg busbars to my fan (and 10 amp circuit breaker on pos) and I will use those connectors you recommended for easy disconnect: https://smile.amazon.com/gp/product/B07V6NJ37P/

    Questions is: what connector do I use between busbar and fan? 5/16 lugs that are made for 12awg? I don't see many... if not then what? 

    Also, this is the 10amp breaker I got: https://smile.amazon.com/gp/product/B000K2K6Y8/

    I just looked at it and it is dc and ac on it? I am confused if this can work in 12v? online people asked if this will work in 12v and were told YES.... the back of those terminals says line and load. 
  • Wheelman55
    Wheelman55 Registered Users Posts: 233 ✭✭✭
    Mini...you are making progress!

    Here’s a link to some 5/16” 12/10 awg ring terminals. https://ceautoelectricsupply.com/product/non-insulated-ring-terminals/

    If you call them, they will install the ring terminals for you, otherwise you’ll need a crimp tool and/or solder.  Personal preference is to crimp.

    Best of luck...
    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Thank you wheelman.

    I will call the person you rec earlier in the post for those battery and charger cables as I will need them anyway once I fully install system. 

    Am I doing an over kill with 12awg for that silly toilet fan? 
  • Wheelman55
    Wheelman55 Registered Users Posts: 233 ✭✭✭
    minisolar said:

    Am I doing an over kill with 12awg for that silly toilet fan? 

    Depends on how long your wire run is from batt to fan.

    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Run will be about 5-6 ft at most... 
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Yes... 12 AWG (good for 20 amps @ NEC) for a fan that draws much less than 1 amp...

    The 12 AWG wire does not hurt... But if the fan ever shorted internally, I would guess that the small wires would ever pop a 20 Amp fuse/breaker... Using a small fuse/breaker at the fan or even at the source of the 12 AWG bus connection would be "safer".

    Fuses/breakers are to protect the wiring--Not the devices/loads. Too much current for a load with small wires could start a fire at the load (if there is a short somewhere at the load).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    edited October 2020 #71
    Another detour unfortunately... 

    I was going to pick up those AGM batteris. The 210ah 6v for $165 each. Turns out they are not $165 but $325.... Spent the last hour finding another source. Best price, surprisingly, is here. https://www.solar-electric.com/upg-gc2-agm-deep-cycle-battery.html

    Free shipping and no tax for 6 of them. But.... I don't want to buy all these before I can set up power system so this I won't buy these for at least 6 months. 

    Another option I thought off. 

    Buy a 12v bilge pump like this one: https://www.amazon.com/YaeMarine-Line-Blower-Electric-Marine/dp/B07S6FVBCL/

    Which draws 2.5 amp on 12v so 30 watt... Then buy a cheap 30 (or larger?) solar panel and connect it directly. While I am in the cabin - just run toilet fan 24/7 off generator then when I leave - connect this one instead. 

    Is that possible? 

    Another idea... Just connect a solar panel directly to the toilet fan? since it only draws 0.21amp I can use a 2.5watt panel?? Maybe a better idea will be to buy a larger (10watt ? 20watt) panel then something in between to protect it from over current? or maybe to insure more run time during cloudy days: get a 50 watt panel and a buck down transformer that will regulate power and prevent my toilet fan from frying? https://www.amazon.com/DROK-Adjustable-Converter-Transformer-Protective/dp/B07JZ2GQJF/

    Or yet another idea.... buy those inexpensive kits similar to this one: https://www.amazon.com/SUNER-POWER-Upgraded-Watts-Crystalline/dp/B07WYZPN2B/

    Then buy a much smaller 12v battery so when I am there: charge battery using genset and use fan 24/7 on genset power. When I leave connect the toilet fan to the 12v battery and panel. I think you calculated that option and it showed 377 watt array which doesn't make sense here for me since this is temporary ? 
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    edited October 2020 #72
    With solar--It is all about the loads... Watt*Hours per day...

    A 2.5 Watt small computer DC fan vs a 30 Watt boat bilge blower--10x more current, 10x larger system.

    A bilge blower is going to have more air flow against higher backpressure... Not a bad thing for venting your throne.

    You have to decide the mix/match of small fan vs blower...

    You can get a 50 Watt or larger solar panel and run the blower for 3-6 hours per day (need larger panel to get fan spinning in the morning---Solar panels have zero surge current capabilities). There are devices called Linear Current Boosters (LCBs)--But these things can be very expensive (>>$200) and are not that common... The are MPPT type controllers, take the high voltage/lower current of the panel (especially in the morning) and down convert to low voltage/high current to start the motor (more or less, DC motors need higher current for starting torque).

    Regarding the 377 Watt panel--That was because you originally wanted to run the small fan for 10 days without sun (between your weekend trips?)... So that made for a larger battery bank--And the 10% suggested rate of charge for that large bank. If you back down to 2 days storage and 50% max discharge--That would be a smaller bank, and a smaller panel for 10% rate of charge...

    Of course, with the larger bank and array, you can always use the electricity for other things... A very common setup is to use a small(er) battery bank + array system, to power lights at night/cell phone chargers/etc. (quiet time). And run the genset when the loads are greater during the day (and perhaps run some charging current back to the battery while the genset is running anyway).

    I may have missed something--But sometimes you have to go back to your requirements and recalculate if you have changed the requirements (less than 10 days, larger blower wattage, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    Sorry Bill. I did jump from a few ideas here. 

    You are right - running the toilet fan, off solar directly without battery, which only draws 2.5 watt is the best way... I do not want to damage it from the solar voltage fluctuations. I emailed the company about the voltage range of the fan and let's see if they know 

    If I want to have the fan to run as much as possible while I am not there directly off solar - then I am better off with a larger panel right? like a 50 watt? but then that panel will send too much power to the fan and can damage it right? is it possible to put something in between to prevent it from damaging the fan? Or am I better off just getting  a smaller panel? 
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Once you have the minimum Wattage panel to run the fan... Then that is it. You can run a 150 Watt panel (with correct voltage) and the fan will not be harmed. The larger panel will give you more hours of running per day (more morning/evening time). You can even get two panels... Face one south east and the other south west to try and get closer to sunrise and sunset (virtual tracking).

    The problem is the working voltage of the panel.. The typical "12 volt" panel has a Vmp (voltage maximum power) of ~18 volts. And your fan is probably designed for 12 volts +/- 10% (13.2 volts max)... So a standard solar panel could run too much voltage to the fan--Solar panels have an output voltage of something like +/- 20%... (voltage goes up in subfreezing weather).

    Getting a larger 24 volt fan and running it on ~18 volts or less (down to 14.4 volts or so on a very hot day)--It will not damage the fan.

    People of put drop resistors or diodes to drop the voltage. And some probably just run them and see what happens.

    Or you can even get a small Buck rMode (voltage reducing) power supply... There are lots of these on Amazon and eBay:

    https://www.amazon.com/s?k=dc+buck+module&crid=3UJX7NULQ79EI&sprefix=dc+buck+mo,aps,255&ref=nb_sb_ss_i_1_10

    There are lots of these for $15 or so (or less)...

    It really depends on how much you want to experiment... Solar Panels are not "batteries". They are current sources and can have very weird effects when connecting loads (or DC converters) that expect a stable "battery type" power source....

    There seem to be a few more inexpensive MPPT type DC converters out there:

    https://www.amazon.com/Voltage-Controller-Panels-Step-Down-Charging/dp/B07KDQ9F1S (listed for battery charging and some very poor English in the product description--No reviews).

    May work better/less possible issues with Solar panel and a DC fan... 

    Unfortunately, you may be stuck with trying several options (spend some time and $) to get something working for your needs... I don't have anything to add (have not tried any of these DC converters--Just links, I am not recommending anything above from my experiences). 

    How far do you want to go down this path (discussion wise).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Another way, is to use a simple Zener Diode to prevent the voltage from rising too high.   It needs to be  rated at 1/2x the power of the PV panel.  So if you have a 100w "12v" (18V really)  panel, and use a 14V zener, you need at least 50w of diode and heat sink - the z diode will be dissipating 20W and you need some headroom to get rid of heat.    But it's simple, just a diode and heatsink.

     With such a small load of fan, you may need close to 90W of dissipation, I'm not sure how things tilt in the I-V curve of the panel with large panel, small load, partial voltage.....

    ( 100w panel  @ 18V = 5A.   Diode dissipates 4V @ 5A = 20W heat )
    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 ,

  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    edited October 2020 #76
    Bill your idea of 24v pc fan is a great idea. That way I can hook it up to a panel and I will be all set.... 

    I am thinking this one: https://www.amazon.com/GDSTIME-80mm-25mm-Brushless-Cooling/dp/B00N1Y3T9G/

    or a larger one and more pwoer 24v like this one: https://www.amazon.com/Wathai-120x120x38mm-120mm-Industrial-Cooling/dp/B07PQXSSDN/

    I then buy a high watt (100 watt? 50 watt?)?

    Mike: I didn't see your post. That sounds good as well. It cost about the same as the fan but saves me the work of setting up a second fan. 

    Is the heat an issue? I could install it on the outside of the cabin... temp there during the day now are about 40-50 and it will go down and down obviously .... Can you give a ling to the right diode assuming 100 watt panel? 
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    edited October 2020 #77
    mike95490 said:
    Another way, is to use a simple Zener Diode to prevent the voltage from rising too high.   It needs to be  rated at 1/2x the power of the PV panel.  So if you have a 100w "12v" (18V really)  panel, and use a 14V zener, you need at least 50w of diode and heat sink - the z diode will be dissipating 20W and you need some headroom to get rid of heat.    But it's simple, just a diode and heatsink.

     With such a small load of fan, you may need close to 90W of dissipation, I'm not sure how things tilt in the I-V curve of the panel with large panel, small load, partial voltage.....

    ( 100w panel  @ 18V = 5A.   Diode dissipates 4V @ 5A = 20W heat )
    What about  these as combo?

    https://www.amazon.com/Adjustable-Converter-1-25-36v-Efficiency-Regulator/dp/B079N9BFZC/
    https://www.ebay.com/itm/Mighty-Max-100-Watt-Solar-Panel-12V-Poly-Off-Grid-Battery-Charger-for-RV-100w-/392993993697?_trksid=p2385738.m4383.l4275.c10

    Then I use the regular toilet  fan which is 12v 2.5 watt and adjust the current perfectly on this buck down. 


  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    The zener diode is a "brute force" method.  Dumb, simple. But it generates heat, and may need a bit of design refinement.  if you can find a prepackaged buck/boost that will work with a PV panel  (varied volts, varied amps) and restart each morning, go for it.

    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 ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Your Amazon link:

    https://www.amazon.com/Adjustable-Converter-1-25-36v-Efficiency-Regulator/dp/B079N9BFZC/

    Can work... Here is where it gets a bit "dicey" and why it is hard to say if any specific DC to DC converter will work...

    When the sun rises, the load draws more current/power than the solar panel can take. And the DC to DC converter will "collapse" the solar panel output from Vmp~18 volts to near zero volts as it tries to draw more current than the panel can supply (little sun on panel)--There is no damage, but the controller can get "stuck in a rut"... Remember Power=Voltage*Current... When the DC to DC converter has collapsed the solar panel to near zero volts, the power is near zero from the panel, even as the current rises (zero * any number still equals zero). So it is possible for the DC to DC converter to "clamp" the solar panel voltage very low (maybe 4 volts in the above link)--And it will take more current until the controller can get enough power from the 4 volts * available current to start the fan motor...

    Since your fan motor power is so low--Chances are that with any 20 Watt panel or more will force the DC to DC converter + fan to start without too much issue...

    There can be other issues too... Some converters have a safety mode that when they get an input or output voltage fault, the turn off and will not run again until the input power is turned off and back on again. Have no idea if these converters will do that--It is just one of the fun things you may find out when setting up your system.

    Most converters assume they are connected to some sort of battery pack/bank. Solar panels that have "brown out" as sun rise/sets can be "confusing" to a DC to DC converter not designed for solar.

    These are certainly cheap enough to try and see if they work... And there is a good chance they will work well.

    The solar panel from eBay looks fine (Vmp~18 volts--Good for 12 volt battery charging). I don't do much on eBay--Know nothing about seller or panel mfg... Always check shipping costs (zero in this case)--Very inexpensive 100 Watt panel--And packing/shipping solar panels is not cheap either.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    edited October 2020 #80
    Thanks Mike and Bill. 

    I heard back from the toilet company. They said the toilet fan voltage range is 5v - 13.8v.

    Does this help us in figuring out?


  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    minisolar said:
    Thanks Mike and Bill. 

    I heard back from the toilet company. They said the toilet fan voltage range is 5v - 13.8v.

    Does this help us in figuring out?


    Great - that means the fan will self start at a very low voltage, so a small 20-50w range panel would be good. Going larger is not likely to be of much help.  But there is still the issue of a "12v" panel being designed to produce 19V and your fan needs no more than 14v
     You may have to trial and error several dc-dc converters to get what you want .
    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 ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Or just get a 24 VDC fan and skip all the other stuff for direct solar panel -> fan connection (i.e., only drive fan when sun is up):

    https://www.amazon.com/s?k=24+volt+dc+fan&ref=nb_sb_noss_1

    Note that high RPM fans can be kind of noisy... (if close to living space).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolar
    minisolar Solar Expert Posts: 158 ✭✭
    alright done. that is the easiest. 24v and 100 watt panel. Thanks bill