DC Alternator

Discussion in 'Off Grid Living' started by jasonl6, Oct 12, 2014.

  1. jasonl6

    jasonl6 Monkey+++

    Morning guy and gal's. I'm in the market for a dc alternator for charging my battery banks. I currently am using a 13th propane air cooled gen. I just picked up a 2 cry yanmar liquid cooled diesel and would like to run a dc gen/alt and most controler. I've looked around some and most units are smaller for windmill applications.
  2. ghrit

    ghrit Bad company Administrator Founding Member

    Jase, we need a lot more info for good guidance. What is the power and rpm rating of the engine? How many batteries (i.e., amp hour storage rating) and what voltage? Do you already have an inverter to allow an alternator, or a voltage regulator for a DC generator?

    (And for us, what means "13th propane?" And, I assume you mean "2 cyl" not "2 cry" engine.)
  3. fmhuff

    fmhuff Monkey+++

    One of the hot setups for two to three KW generators (Honda and Yamaha) is an alternator powering a car size battery with an AC inverter running off the battery. This way there is no need to match frequency and many gen-sets can slave to each other.

    Even so you could roll your own using a semi-truck 220 Amp alternator. Even this Amperage only puts out about 2.6+ KW which is around a 4 HP load. What's the HP of the Yanmar and what's it's most efficient load and rpm range. I think you should shoot for efficiency with the ability to surge a little when needed.

    I'm thinking off the shelf low cost components that will last a long time and can be replaced easily. Cost vs performance. There are also some interesting offerings on eBay in the 5KW range.
    Last edited: Oct 12, 2014
  4. Tevin

    Tevin Monkey+++

    Yes I agree with @ghrit . Your post has too much missing info/unclear terms to advise in detail where to go with this. What is a "most controller"?

    Anyway, that Yanmar is one of the best, if not
    the best small generator on the market. I would get a nice battery charger sized for your application, push it with the Yanmar, and be done. You cannot build anything better than a Yanmar.

    I use a small 1400 watt Honda generator with a 40 amp automotive charger to keep my batteries topped off when my solar panels can't keep up. Even in the dark of winter I don't need to run the generator more than an hour or so per day.

    If you want something dedicated to battery charging only, the suggestion of truck alternator & small engine combo is excellent. It's a fairly easy do it yourself project that does not cost a lot of money. There are tons of YouTube vids that will show you how.

    AmericanRedoubt1776 likes this.
  5. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Also , your driving it with belt & pulleys or direct . My Yanmar 2 Cyl is 1800 rpm with HI set at 2100 rpm .
    Your solar ? Like me at 1/2 way so far. Spent the day (Weekend doing this , & every weekend till 2016, then I'll be finished) Need to know your battery voltage & amp hr's , Cuz C20 is what you want to hit.

    Last edited: Oct 15, 2014
  6. jasonl6

    jasonl6 Monkey+++

    Sorry for the lack of info in my first post. My system is 16 6 volt deka batteries in 2 48 volt banks. I have a outback 60 charge on 9 250watt sharp panels and 8 100 watt panels on a xantrex charge controller. I have dual xantrex inverters that are used currently when the ac propane generator is charging the batteries. I would like to use a dc system with another mppt charge controller. The diesel unit will be more efficient and since it's liquid cooled i can use the radiator to temper my garage in the winter.

  7. ghrit

    ghrit Bad company Administrator Founding Member

    OK so far. What is the nameplate rating on the Yanmar? Given that it's pretty likely a marine machine, the governor will not hold or respond to rapid changes in load, so a brushless DC generator is a best bet (tho' an alternator with inverter will work fine, just make sure the inverter puts out a clean sine wave.) What are your "normal" loads and at what voltages? Peak anticipated loads?
  8. jasonl6

    jasonl6 Monkey+++

    I'm not near the motor now but know it was off a semi. It was used for a/c, heat and power while parked. It has a plate that says 8.8kw at 2800 rpm. I would like to back it off to 1800 rpm. Not sure how to answer the question about peak loads.
  9. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    What I would do in such a situation, is look around for a 48 Vdc Generator, in the 6-8 Kw, range. (LeMarsh)(Not an easy find, these days) Since you Battery Bank Voltage is 48Vdc, there just are not a lot of 48+ Vdc Generators made these days. Now if you had a Battery Bank voltage of 24 Vdc, any of the Bigger 18 Wheeler Alternators can do that job, and can be found surplus in MANY Truck JunkYards around the country. SO, with that in mind, Better to go with an AC Genend, and then go with 48 Vdc High Current Battery Charger that are used in the Telco Industry to maintain their Internal Battery Banks at the Central Offices. (Raytelco, Lorain, LeMarsh, etc)
  10. jasonl6

    jasonl6 Monkey+++

    That is kinda how it's set up now. I was hoping to just be able to find a 48 dc unit. The only ones I came up with are these 2. PM-ALT.com Permanant Magnet Alternator for Wind Turbine the second is only good to 1200 possible 1600 max. Not sure about the first one.

    Last edited by a moderator: Jan 26, 2015
  11. kg4jxt

    kg4jxt Monkey

    I had a couple of wind generators over the years on my sailboat. The best one was made from a 2.5kW industrial sewing machine motor PMDC. Now, that motor was a nominal 100V motor, but connected to a battery bank it was held to the bank voltage and put out a decent current. I think you do not have to concern yourself too much with the nominal voltage of a PMDC motor/generator. But you do need a diode between it and the batteries. I did not buy the motor direct from the distributor - a wind generator company had it drop-shipped to me, so can't help you with source, but it was less than $50 for the motor (shipping cost more).
  12. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    If you put a MPPT Charge Controller (Outback MX or FM Series, or similar) in between that PMDC Motor (nominal 100Vdc) and the Battery Bank, you will realize significantly more Energy transfer, than running direct. Also, the Charge Controller will deal with the Extra High Voltage from on the Input, and provide Three State Battery Bank Charging, which will prolong the life of the Batteries in question. Just noting, here....
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