Steca Solsum 6.6F charge controllers

Iceni John
Iceni John Solar Expert Posts: 103 ✭✭
edited December 2017 in Caravan, Recreational Vehicle, and Marine Power Systems #1

I recently got two of these small charge controllers for my bus's two Group 31 starting batteries, with each one connected to one battery.   They are powered from the bus's 2kW of PV panels, with each one fed by four panels through a 7.5A fuse.   Steca's instruction sheet says that they should be powered by a maximum PV current of 6A  - my setup is obviously a little bit more than that!   The problem is that one CC always blows its 7.5A fuse, and the other CC is boiling the battery with almost 16V.   Evidently I'm simply overpowering them.

So, is there a current limiter that will limit each of these CC's input power to just 6A?   How else can I use these little CCs with my bus's panels without overloading them?   I REALLY don't want to have to install one or two small PV panels just for them.

Thanks, John     

40' Crown bus with 2kW of tiltable panels on the roof:

Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

Southern California

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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited December 2017 #2
    The array is way, way oversized for both the batteries and the controller's, it's no wonder they are having problems, assuming 1 Kw per controller there is a potential of ~80A at 12V in perfect conditions. It would be prudent to reconsider the whole setup, it is potentially hazardous and a fire risk, please protect yourself and disconnect what you have. Design a system that is ballanced with all the safety features required, people here can help but I'm afraid what you currently have is simply not safe, just trying to help, not being negative.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #3
    Why are you trying to charge the starting batteries this way? If these batteries aren't running any other loads than originally intended you shouldn't have to have a daily charge cycle on them.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    #4
    littleharbor2 said:
    Why are you trying to charge the starting batteries this way? If these batteries aren't running any other loads than originally intended you shouldn't have to have a daily charge cycle on them.


    One of the start batteries has the engine's ECM permanently connected to it, and it will slowly drain the battery, especially after several weeks of non-use.

    John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    #5
    mcgivor said:
    The array is way, way oversized for both the batteries and the controller's, it's no wonder they are having problems, assuming 1 Kw per controller there is a potential of ~80A at 12V in perfect conditions. It would be prudent to reconsider the whole setup, it is potentially hazardous and a fire risk, please protect yourself and disconnect what you have. Design a system that is ballanced with all the safety features required, people here can help but I'm afraid what you currently have is simply not safe, just trying to help, not being negative.

    Yes, I well know that!   This is why I was specifically asking whether there are current limiters that I could use for these two small CCs.   Apart from buying a 120VAC charger and running it off the inverter (a clumsy and inefficient way of doing things), the only other way to keep my start batteries always fully charged would be to occasionally connect them to the house batteries' Morningstar CCs, but they are set for deep-cycle batteries, not for SLI batteries.   I just want a simple and completely-automatic way to always keep my start batteries at 100%.   I already have a roof-full of PV panels for my house system, so it makes sense to me to also use them for the start batteries if possible.

    John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #6
    Hoe about adding a single small 12 volt panel and controller completely separate from the big system?

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #7
    What are the specs on the panels (size, and how wired - numbers in series and/ or parallel)?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    edited December 2017 #8
    Estragon said:
    What are the specs on the panels (size, and how wired - numbers in series and/ or parallel)?


    They are in two rows of four, each row wired in parallel, i.e. each row produces 34A at 30V.   The Steca CCs' rated maximum input voltage is 47V, but obviously I am bigly* exceeding their intended input current, hence the Bad Things happening.

    Mr.Google suggested that a buck voltage converter with current limiter could possibly be a solution.   I could set it to about 18V output (the same as a small "12V" panel) and 6A, then it should produce sufficient power to allow each Steca CC to gently float-charge the start batteries.   Does that sound reasonable?

    As I've mentioned before, with a roof-full of PV it seems silly to have to get another panel just for the start batteries.   I'm sure there's something out there that will work for me  -  I just don't know exactly what at this time.

    Thanks, John

    * Sorry for that Trumpism . . .

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #9
    If the panels are in parallel, why not just take one panel out of the main array and wire it to a smallish mppt charge controller? Something like a Midnite Kid or Morningstar Sunsaver would handle the voltage and you wouldn't have to worry about too much current.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #10
    Since you already have the controllers I still think the most straightforward and inexpensive approach would be a small 12 volt panel to maintain your starting batteries.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #11
    > @littleharbor2 said:
    > Since you already have the controllers I still think the most straightforward and inexpensive approach would be a small 12 volt panel to maintain your starting batteries.

    Probably, but RV applications are often constrained by suitable mounting space. Another option might be an echo charger (eg Bluesea).
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    #12
    Estragon said:
    If the panels are in parallel, why not just take one panel out of the main array and wire it to a smallish mppt charge controller? Something like a Midnite Kid or Morningstar Sunsaver would handle the voltage and you wouldn't have to worry about too much current.


    I had thought of that, but running an extra cable or wire down from the roof is impossible at this point  -  I've run the 4AWG downfeed cables through the hollow roof ribs, but I cannot get another conductor inside them now.   So, it's 34A or nothing!

    John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • grizzzman
    grizzzman Registered Users Posts: 18 ✭✭
    edited December 2017 #13
    Google trik-L-start. I did this in my M/H. It worked well. It will charge a max of 5 amps and drops the voltage or an amp-L-start that charges a max of 15 amps off the house bank.
    Boondocking is my game
    640 Watts Mono Bogart TM2030 and SC2030  Controller GC 6V 208 AH  Costco batteries  300 Watt Inverter and 2000 watt inverter 100AH LIFEPO4 2P4S
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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    edited December 2017 #14
    grizzzman said:
    Google trik-L-start. I did this in my M/H. It worked well. It will charge a max of 5 amps and drops the voltage or an amp-L-start that charges a max of 15 amps off the house bank.


    That would probably work well for me.   However, I haven't given up on finding some sort of buck voltage converters with 5 or 6 amp current limiters  -  I think Drok makes some, but who knows what their quality is?   If I can't find something like that (I'll talk with my go-to electronics store folk tomorrow and see what they recommend), then the Trik-L-Start will be a good Plan B.   Thanks for your help with this.

    Whatever I end up doing, I'll need two separate chargers for the two start batteries, because the battery that's constantly connected to the engine's computer needs more to keep it fully charged than the other battery that has no load at all on it when the main switch is off.

    John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #15
    A potential problem with a buck converter is they generally lower voltage, that is not what's needed, it's the current which needs limitation, my experience with them is they are current limiting, which means they shut down to protect themselves, not to protect the load downstream, requiring disconnect to reset. PWM controllers do not like any sort of capacitance in the input and may not work with a buck converter anyhow. The Trik-l-start device looks to be a good fit as its specifically designed to do exactly what's needed, trickle charge indirectly using the current array, networking is amazing, you discover new tricks from others experiences, got to like that.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    #16

    I've just ordered a pair of Trik-L-Start battery maintainers to keep my start batteries healthy.   My experiment with the Steca Solsum CCs would have worked if I had been able to find two 6A solar panels (which is what they are designed to run from) that would fit the remaining limited roof space.   There are no readily-available current-limiting buck converters that would work right in this application.   Well, it was fun trying.   So now I have two Solsum CCs and four switches on a panel, ready to use, looking for a new home.

    Thanks everyone for your suggestions and advice.

    John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    #17

    Progress report after using the Ultra Trik-L-Start battery maintainers for a few weeks:

    I initially used an ATC 7.5 amp fuse for each Trik-L-Start's power feed from the house batteries (they're rated at a maximum 0f 5 amps charging), but they both kept blowing fuses every time I started the engine.   Hrumph.   The owner of LSL Products, their manufacturer, advised me to instead use a 10 amp self-resetting circuit breaker for each feed wire because they can briefly draw more than 5 amps if the start batteries are under load.   I now have a pair of Cole-Hersee 10 amp Type 1 self-resetting automotive-style CBs (the same sort as are used everywhere else in the bus), and they seem to have solved the problem.

    The Ultra Trik-L-Starts seem to be a good product, even though I'm surprised that they can briefly draw more than 7.5 amps.

    John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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