Would It Be Better and Cheaper?

rss2q
rss2q Solar Expert Posts: 75 ✭✭✭✭
in Advanced Solar Electric Technical Forum #1
Hey,

I have a 36v electric motor that uses 3x 12v batteries hooked up in series to produce 36v.

From looking around, 36v charge controllers are not very common, and some that I have found are outrageously expensive.

Would it be smarter and cheaper to just buy 3x 12v charge controllers, and each charge controller will be wired to one of the 12v batteries?

So basically, each 12v battery will have it's own solar panel/charge controller.

Thanks :D

Also, as for prices that I've found, most 36v charge controllers are $100 and above.
The 12v charge controllers that I'm thinking of using I have found ranging between $15 - $30. I just need basic reliable charge controllers, nothing fancy.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #2
    Re: Would It Be Better and Cheaper?

    About the same price (three controllers * $30 vs $100+ for a 36 volt controller).

    Anyway--Yes it should work with three separate controllers--however, you do have to be careful with both the wiring (no common ground on panel connections) and any signal/other connections (aux contacts, metal box of controllers, etc.) that may now be at 0, 12v, and 24 volts (each controller would have a ground offset which may affect other signals/metal enclosure/ground connections).

    I would go with the 36 volt controller instead and avoid the other issues--Even if you are careful, there is always the chance that you missed something in the 3 controller wiring issues.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #3
    Re: Would It Be Better and Cheaper?
    BB. wrote: »
    About the same price (three controllers * $30 vs $100+ for a 36 volt controller).

    Anyway--Yes it should work with three separate controllers--however, you do have to be careful with both the wiring (no common ground on panel connections) and any signal/other connections (aux contacts, metal box of controllers, etc.) that may now be at 0, 12v, and 24 volts (each controller would have a ground offset which may affect other signals/metal enclosure/ground connections).

    I would go with the 36 volt controller instead and avoid the other issues--Even if you are careful, there is always the chance that you missed something in the 3 controller wiring issues.

    -Bill

    Well this is the only 36v charge controller that I have found and it's a 2-4 weeks wait on it and it's from a company I've never done business with: http://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/MPPT-Solar-Charge-Controllers/Solar-Converters-Charge-Controllers/Solar-Converters-PT-36-5A-36V-MPPT-Charge-Controller/p1380/

    I just wish there were more options as well as affordable options.

    Have you ran across any by chance?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #4
    Re: Would It Be Better and Cheaper?

    I think some of the large MPPT controllers can program 36 volt batteries--but as you say--they are $400-$600+ units.

    The one from Solar Converters Inc. is the only small MPPT unit I am aware of...

    How large of array (or battery charging current) are you looking at?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #5
    Re: Would It Be Better and Cheaper?
    BB. wrote: »

    How large of array (or battery charging current) are you looking at?

    -Bill

    Not much at all since space is very limited, so I will not even come close to going over 3A.

    For the other idea of using 3x charge controllers, I was just going to use 3x 5Watt solar panels that you can get off eBay which I've used in the past. The charging would be slow, but they would still charge the batteries.

    But yes, I'm very limited on space, thus my array is going to be tiny.
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #6
    Re: Would It Be Better and Cheaper?

    those might be amorphous 5W panels and they (Asi) are know to lose power quickly so you might want to go to Mono or Poly Si panels. better production over time... since you are tight on space don't go too cheap.

    cheers
    eric
     
    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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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #7
    Re: Would It Be Better and Cheaper?
    westbranch wrote: »
    those might be amorphous 5W panels and they (Asi) are know to lose power quickly so you might want to go to Mono or Poly Si panels. better production over time... since you are tight on space don't go too cheap.

    cheers
    eric

    Yeah that's the least of my worries at the moment, the biggest issue now is figuring out what route to go for how to charge them up, but I will consider that when I get to that step. :)
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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #8
    Re: Would It Be Better and Cheaper?

    Hmm, I ran into this 36v scooter charger, but it's extremely hard for me to tell from the picture what type of connection is on the other end: http://www.scootercatalog.com/charger-es36v.html

    I'm guessing this will not work, but thought I'd at least run it by you guys.

    I'm hoping to run into another 36v charge controller...searching extremely hard lol.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #9
    Re: Would It Be Better and Cheaper?

    I am guessing that is a 120 VAC Input charge controller.

    There is this 25 amp 36 VDC controller -- $135. Not cheap--but good sized power rating (very old design I think--but would work).

    This sounds like a very small motor battery system--Can you use another voltage motor/motor controller?

    Or, could you use a 48 volt battery bank and get a small buck mode charger to down convert to 36 volt motor bus?

    Many of the choices depend on how much power you need (peak motor amps/watts; amount of Watt*Hours per day you need to collect; how may days of no-sun for batteries; etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #10
    Re: Would It Be Better and Cheaper?
    BB. wrote: »
    I am guessing that is a 120 VAC Input charge controller.

    There is this 25 amp 36 VDC controller -- $135. Not cheap--but good sized power rating (very old design I think--but would work).

    This sounds like a very small motor battery system--Can you use another voltage motor/motor controller?

    Or, could you use a 48 volt battery bank and get a small buck mode charger to down convert to 36 volt motor bus?

    Many of the choices depend on how much power you need (peak motor amps/watts; amount of Watt*Hours per day you need to collect; how may days of no-sun for batteries; etc.).

    -Bill

    I've actually come up with another solution but need to run it across you all first which may work and be cheaper, but I'm about to crash for the night, so I'll quickly draw up my idea tomorrow and post it.
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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #11
    Re: Would It Be Better and Cheaper?

    Alright I attached a rough drawing of my idea.

    My project also as can be seen will have 2x 12v batteries hooked up in series to produce 24v. I didn't state this at the time because I didn't think it was relevant.

    Anyway, what I think will be easier and cheaper is, hook a 24v inverter to the 2x 12v batteries that are hooked up in series, and since I have a AC charger (basic power brick that came with the motor and batteries) for the 36v (3x 12v batteries) system, I can simply just charge the 36v side from the 24v system.

    So there are two separate systems here. A 24v system, and a 36v system. Since 36v is just a pain in a butt I'm starting to see, and since originally the 36v system was charged via AC, why not just continue to charge it from AC by stealing power from the 24v system via an inverter? :)
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #12
    Re: Would It Be Better and Cheaper?

    If your 36 volt power requirements are not that high--Yes, that would be a good solution.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #13
    Re: Would It Be Better and Cheaper?
    BB. wrote: »
    If your 36 volt power requirements are not that high--Yes, that would be a good solution.

    -Bill

    Alright thanks Bill for confirming!

    While we are on the topic, you wouldn't by chance know of any better 24v inverters for the similar price as this one here would you: http://www.amazon.com/Power-Bright-ML400-24-Watt-Inverter/dp/B000NP0MXC/ref=sr_1_1?ie=UTF8&qid=1307630467&sr=8-1

    This one doesn't appear to be mountable, but I'd like one that is. I'm sure I can make some kinda contraption that can hold it but just checking first.
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  • TheBackRoads
    TheBackRoads Solar Expert Posts: 274 ✭✭
    #14
    Re: Would It Be Better and Cheaper?

    Are you trying to charge a 36V battery bank that runs an electric trolling motor?
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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #15
    Re: Would It Be Better and Cheaper?
    TheBackRoads wrote: »
    Are you trying to charge a 36V battery bank that runs an electric trolling motor?

    It's not a trolling motor I think, it seems it's just a standard induction motor as I can see the rotor, stator etc. inside from the top. But what the battery is powering really doesn't matter, it's the method of how I'm going to charge it is what I am/was concerned about.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #16
    Re: Would It Be Better and Cheaper?

    Induction motors are typically AC powered...

    Normally DC motors have brushes (or possibly VFD electronics to drive brushless motors).

    Regarding the inverter--I have nothing to say... If a MSW inverter will work for your needs--That is a typical price for a low cost inverter (from my little bit of looking around).

    If you are not sure of the difference between a TSW and and MSW inverter... Take a look at these FAQs:

    All About Inverters
    Choosing an inverter for water pumping

    If you need a reliable system for your needs--I would look at TSW inverters (however TSW is much more expensive).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rss2q
    rss2q Solar Expert Posts: 75 ✭✭✭✭
    #17
    Re: Would It Be Better and Cheaper?
    BB. wrote: »
    If you need a reliable system for your needs--I would look at TSW inverters (however TSW is much more expensive).

    -Bill

    Yeah I'm on a budget and can't spit out $100+ for an inverter, so I guess I'll have to go with the MSW. I'll read that article later too.

    Thanks for your help!
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  • TheBackRoads
    TheBackRoads Solar Expert Posts: 274 ✭✭
    #18
    Re: Would It Be Better and Cheaper?
    rss2q wrote: »
    It's not a trolling motor I think, it seems it's just a standard induction motor as I can see the rotor, stator etc. inside from the top. But what the battery is powering really doesn't matter, it's the method of how I'm going to charge it is what I am/was concerned about.

    No I understand what your after, I was just curious as to your load. It was the only thing I could think of that is available in 36V being from the state of 10,000 lakes... or atleast thats what the plates say. haha :cool::p
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