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Solar charge controller feed by truck alternator

Discussion in 'Technical Chat' started by exportexp, Jul 12, 2018.

  1. Jul 12, 2018 at 11:47 AM
    #1
    exportexp

    exportexp [OP] Well-Known Member

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    All of our trips so far have been driving all day and camping at night. So I was looking at a CTEK D250SA to charge an extra battery mounted in the bed of my truck. I think I can recharge the minimum discharge from each night while driving trails each day. I also want the ability to hook up a solar panel in the future if it is needed.

    The thought passed through my head and I would like input.

    Could I just use a decent MPPT charge controller feed by the alternator instead of solar panels do the same thing? My Idea is to have a relay hooked up to hot while running circuit. Take power from that relay and feed it into the solar panel in-put to the charge controller and let the charge controller work its magic.

    CTEK D250SA $269 - $300

    Decent 20A MPPT charge controller $100

    That’s almost enough savings to take an extra weekend trip.

    What do you think? Will it work? What am I missing?
     
  2. Jul 13, 2018 at 6:22 AM
    #2
    Wyoming09

    Wyoming09 Well-Known Member

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    The question is do you want to go Solar power or not ??

    I don`t know if a charge controller will work with Alternator power input if your sure it will then just hook it up .

    I just always used a battery isolater for charging a second battery thus saving the Main battery for starting
     
  3. Jul 13, 2018 at 10:51 AM
    #3
    exportexp

    exportexp [OP] Well-Known Member

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    Yes I would like the ability to go solar in the future.

    I don't need the batteries to be tied together.
    I don't have a winch or other large loads on either battery.
    The 2nd one is only used for water pump, LED lights, night time charging and maybe a fan.

    I'm not sure how the charge controller will behave being tied to the alternator. That's what I'm hoping someone can help me answer.
     
  4. Jul 14, 2018 at 1:59 AM
    #4
    Wyoming09

    Wyoming09 Well-Known Member

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    Have you decided on just what charge controller you like.

    Looking at a Few of them it might be possible to clean and throttle the alternator output enough to work .

    The cost though might get expensive

    Maybe some one has already done this ??

    Why not just go Solar and be done or run a dual battery Isolator to your ready to upgrade to Solar
     
  5. Jul 17, 2018 at 11:02 AM
    #5
    License2Ill

    License2Ill Woke like a Coma Toyota Tacoma

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    I have the older D250S and the Ctek stuff is worth the extra money.

    I just got back from 90 days on the road with an average of 5 days spent per camping spot. 78L ARB fridge with a few smaller accessories. 11a of solar and the alt w/ the Ctek kept my 2nd battery happy.

    I also have a Morningstar Sunkeeper pwm 11A on the starter battery that was my original second battery charging unit that I wired in different ways and it never seemed to work well with the Alt input.

    Most 12v modules are 20-22voc with a heavy load from the charge controller you can see those vlts drop to 14.5-16vdc, plenty for the second battery to be charged.
    The alt at best puts out 14.4? Under large load from the CC the vlt from the alt may be 11-12vdc at the input at the charge controller and it'll take quite a while to charge the second battery if it will charge it fully at all.

    It's just not ideal.

    I'm not sure what is all on the market these days. Maybe they make voltage upconvertors on more CC like I believe the ctek has on it's alt input.
     
    Last edited: Jul 17, 2018
    exportexp [OP] likes this.
  6. Jul 17, 2018 at 4:28 PM
    #6
    destin_meeks

    destin_meeks I used to fix people's crappy stereos

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    A big flaw in this plan

    a 20A charge controller is only made to take in a MAX of 20 amps...

    Your alternator puts out 90-130 amps depending on if you have the tow package

    I dont picture the charge controller lasting long, if at all, under that amount of power
     
  7. Jul 17, 2018 at 5:56 PM
    #7
    License2Ill

    License2Ill Woke like a Coma Toyota Tacoma

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    Charge controllers generally don't work that way. A 20A input on a CC can pull 20A Max.

    You can supply it with 100A, say of PV and it'll pull 20A and you've wasted 80A of potential current.
     
  8. Jul 17, 2018 at 5:59 PM
    #8
    License2Ill

    License2Ill Woke like a Coma Toyota Tacoma

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    It's a dry heat thou, AZ
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    Overvolting a CC, yes that'll fry it. Quickly.
     
  9. Jul 17, 2018 at 6:04 PM
    #9
    License2Ill

    License2Ill Woke like a Coma Toyota Tacoma

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    Now that I think of it don't alternators put out current based on rpm & demand loads? Anybody have an answer?

    I know blocking diodes/heat sinks are used on wind generators for excess/unwanted production...
     
  10. Jul 17, 2018 at 6:10 PM
    #10
    destin_meeks

    destin_meeks I used to fix people's crappy stereos

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    From the manual for the Renogy Rover 20A
    "Do not exceed 20A. The Short Circuit of the solar array should be less than 20A"

    It also says
    "When PV short circuit occurs, the controller will stop charging. Clear it to resume normal operation"

    I may be misunderstanding, but my brain thinks that means "don't give it more than 20a or it will quit working"

    I am MECP certified (mobile electronics, all things 12v) and I am familiar with how most things will pull power from what is available, but I believe you can input too much amperage into a charge controller. The manual would at least make you think so.
     
  11. Jul 17, 2018 at 6:38 PM
    #11
    License2Ill

    License2Ill Woke like a Coma Toyota Tacoma

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    It's a Renogy, and imo they're crap, so it may not have the protection features most charge controllers have. I cant say Ive used much of the cheaper china units, but I've never seen or heard of over current destroying a CC.

    I have the older 25A CTEK mentioned in the OP and the 12A Morningstar I talked about earlier and both have been fed from a 160A alternator. The CtEK is designed for a Alt input feed, so it's apt. The other CC didn't seemed to be bothered, but didn't seem to work well off the alt.


    I'm a electrician and specialize in PV off-grid systems btw, but just an enthusiast on the 12VDC stuff. :)
     
  12. Jul 17, 2018 at 6:56 PM
    #12
    destin_meeks

    destin_meeks I used to fix people's crappy stereos

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    Looking at the Morningstar stuff and sure enough, none of them mention input amperage limits. One more thing to look for when I get the chance to build my system :thumbsup:

    You see the whole forum talk about renogy like it’s the bee’s knees. Maybe just a good budget brand?
     
  13. Jul 17, 2018 at 7:19 PM
    #13
    License2Ill

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    They're cheap, compact and have lots of features. We had a client try to do a switch-er-o to get a lower bid by trying to self-supply some of the system. And it was all Renogy. My supervisor threatened to cancel the job, basing it on their internal circuitry being flimsy and a fire hazard and couldn't give him our company job satisfaction warranty.
    I actually got 360VDC into my butt cheek on a metal roof due to a customer supplied cheap china box that had an internal short and bypassed the internal disconnect.

    Morningstar are nice products and fairly inexpensive with great customer service and a decent warranty. I have a PMW unit and one leaf over the module will kill the current, so I'd wish I got one of their MPPT ones. Not sure if Midnite is making 12V automotive stuff, they're nice products also.
     
  14. Jul 17, 2018 at 7:51 PM
    #14
    Sandman614

    Sandman614 Snarky TWSS elf, Travis #hotsavannahdotcom, LRGRNR

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    If you set it up right you don't have to worry about over voting the controller. Note replace the boat motor with an alternator. You need a battery isolator.

     
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  15. Jul 18, 2018 at 8:19 AM
    #15
    synaps3

    synaps3 Wag more bark less

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    There's a lot of misinformation in this thread. I researched the hell out of the CTEK solution for my solars before I decided fuck it and just left the stock battery for now. I'll be getting a dual or triple battery setup with a D250S long-term, but cost is too high to justify my need right now... Either way, I hope this clears some stuff up:

    First, the D250S and D250SA both have integrated MPPT controllers. You don't need that separately. Both are called D250S Dual or just D250S, it's the same thing. The SA is newer, and has support for a smart alternator. You should be fine with the D250S in a Taco, but you can use a D250SA and just not hook up the smart alternator cable.

    Second, the D250S and D250SA are fine with an alternator hooked to the battery terminal, and won't ever get "overload" by the alternator. The D250 has 4 terminals, one for solar, one for alternator, one for ground, and the last for the secondary battery. IT IS DESIGNED for the full current of the alternator. No matter what, charge will be limited to 20A through the D250 to the secondary battery, BUT having way higher current on the alternator side is normal and expected.

    If you need more than 20A charging (only a concern with a really big batteries or multi-battery banks with high discharge), then you put a CTEK Smartpass in parallel with the D250. That passes through more current. It's really not needed for a truck though, that would be more of an RV or off-the-grid setup with a battery bank containing 3+ batteries and a large load.

    If you use the common Renology 100w panel, only use one. The CTEK can't take much more than one panel in direct sun.


    Here's a diagram of how the D250S is typically wired in a simple overland setup. Note it's VERY simple, by design, and works without a ton of crap:

    Screen Shot 2018-07-18 at 11.11.36 AM.jpg

    Put your accessories -- fridge, whatever else, off the Service Battery. I'm planning on keeping the winch on the starter battery though, with the capability to jump manually between batteries if I needed to.
     
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  16. Jul 18, 2018 at 10:25 AM
    #16
    exportexp

    exportexp [OP] Well-Known Member

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    I would like to thank everyone who has responded and provided information.
    From what has been posted here and what I have found with additional research the D250S is the best solution for a hybrid second battery. By hybrid I mean it can be charged by both the alternator and/or solar. Im not not convinced it is the only way to achieve duel charging capabilities, but definitely the simplest.

    At this time this project is getting moved down the priority list due to cost. I'll be sure to update with photos and maybe a write up when I am able to install the D250S.
     
  17. Jul 18, 2018 at 10:37 AM
    #17
    Sandman614

    Sandman614 Snarky TWSS elf, Travis #hotsavannahdotcom, LRGRNR

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    The SI-ACR I posted has one more component, the charge controller, which you can get bundled with the solar panel you choose. The switch battery switch is optional and was just a diagram I mocked up for my installation. I can't see paying the price for the ctek route..
     
  18. Jul 18, 2018 at 10:48 AM
    #18
    synaps3

    synaps3 Wag more bark less

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    The CTEK is more, but you have less components and complexity since the MPPT is onboard. An MPPT controller the same quality as the CTEK will be ~$100, then the ACR is $80 or so, which puts you in the ballpark of the CTEK. I was talking to a seller on ebay and had them down to $200 shipped for the D250S; they're way marked up on most sites.
     
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  19. Jul 18, 2018 at 11:00 AM
    #19
    Sandman614

    Sandman614 Snarky TWSS elf, Travis #hotsavannahdotcom, LRGRNR

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    The charge controller that comes bundled with most panels will be perfectly fine for the weekend warrior overlander. It's not like we're trying to run an entire van off grid in some 3rd world country..
     
  20. Jul 18, 2018 at 11:46 AM
    #20
    synaps3

    synaps3 Wag more bark less

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    By that same token though, most will be fine without solar or dual batteries too. ;)

    MPPTs are a LOT better than PWMs, especially in overcast conditions. To be an apples to apples comparison with an ACR, you need to bundle it with an MPPT to compare against the CTEK configuration.


    If you're already spending $120 on a solar panel with PWM, $100 on a tray, $200 on a battery, $50 on wire/crimps, and $80 on the ACR, the added cost to consolidate into a single unit with an MPPT with the CTEK is relatively small, and you can get a better panel while you're at it.

    To me, the CTEK is a a simple single module that solves the entire dual battery problem with no complex components or wiring diagrams. It's worth it to me to spend $100 more on a $400+ upgrade to get better performance, more simplicity, and a way faster / easier install.


    I don't want to discredit the ACR in a solar dual battery setup. It is a proven, working solution and is cost-effective. The CTEK will perform better and be simpler to install, but it is more expensive and isn't modular at all. Both have their benefits, I just prefer the CTEK.
     

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