12v generators

Discussion in 'Tech/Mech General' started by CHRI$, Aug 13, 2011.

  1. CHRI$

    CHRI$ Funster

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    intresting :thumb:
    same engine as im useing:thumb:



    12 Volt Generators.
    [​IMG]Petrol battery chargers (i.e.12 volt generators) are essentially a standard vehicle alternator attached to a small petrol motor. Many were initially home made and even the current wave of commercial ones are far from "consumer" products.
    Most (all?) of the current ones seem to come from Australia although they may be assembled in the UK. Unlike mains generators you have to adjust the engine speed manually and if you suddenly apply an extra load the engine may stall.
    Unless you are happy to use crocodile clips to connect to your battery each time you use the generator then you will need to do some serious heavy duty wiring and fit an external 12 volt high current socket. Note that disconnecting your generator whilst it is running may damage it.
    The one illustrated above uses a Honda four stroke motor and a Bosch 55 amp alternator. It weighs 12kg and is only 410mm long.
    Whilst significantly noisier (74dba @ 7 metres) than a top end mains generator (say 59dba @ 7 metres) it is considerably quieter than some no-name generators listed at an ear shattering 91dba! It will certainly charge your battery far faster than most battery chargers running from a mains generator and thus annoy your neighbours for less time! 12 volt 55 amp generators are available for around €775 at the end of 2008.
    Because the current range of 12 volt generators do not incorporate a proper three stage battery charger they should only be used for bulk re-charging of a well discharged battery.
    Unfortunately my testing of the generally well made 55 amp Christie generator (above) was cut short by an intermittent fault with the ammeter after a little over an hour of use. Whilst the generator itself was an interesting alternative to a mains generator my experience with the (only?) UK supplier was unsatisfactory (Trading Standards and my Credit Card company are currently involved and we may yet end up in the courts).
    On balance I don't think the current range of 12 volt generators (petrol battery chargers) are yet ready for the overland campervan market. The need to manually adjust the engine speed, the absence of any current limiting electronics (so the engine does not stall when you switch on the inverter) as well as the need to add heavy duty 12 volt wiring together tip the balance in favour of a high quality (inverter) mains generator.
    Note that many mains generators also provide 12 volts for battery charging at "up to 8 amps". My Honda EU10i will charge my campervan battery at around 6 amps but only if the "eco throttle switch" is set to off. This significantly increases the engine speed and noise level. With the "eco throttle switch" set to on, it charges at under 3 amps.
    Stephen Stewart.
     
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  2. Terry

    Terry Funster

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    Hi Chris :thumb: while I find your post interesting (after dragging it out for a long while) I too made the assumption that a alternator would be ideal to charge the batts only difference was mine is run by a 2.8 engine :Rofl1:
    terry
     
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  3. CHRI$

    CHRI$ Funster

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    but terry, do realy want to sit there with your 2.8 engine running for hours chargeing batteries with all the problems that it can cause,ie glazeing the bores,useing expensive diesel,and stinking out the van parked next to you?
    and how would you start your 2.8 diesel if your battery is flat?
     
  4. scotjimland

    scotjimland Funster Life Member

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    Well, as Terry said, they aren't new, .. but this sums them up rather well and why I believe they have never really caught on.. and unlikely to do so as they do not offer 230v mains without heavy cables and a large inverter..

    With the RV, I had a EU20i Honda genny, a 70A four stage Victron charger/inverter .. and 4 x 85ah batteries.. When flat.. ie down to 50% or 12v it only took about 2 1/2 hours to fully recharge .. It did it fully automatically with no need for human intervention.

    If I needed 230v the Victron provided 1.6kw of pure sine wave power..
     
  5. CHRI$

    CHRI$ Funster

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    so how much payload does that that lot take up remembering not all motorhomes have the same payload as an rv,roughly 70 kg i recon?, and cost?£1000 i recon?
    and if you needed 240 why not pull it off the genny at 1800kw of pure sine wave??
     
  6. scotjimland

    scotjimland Funster Life Member

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    Cost .. yes, not cheap, about £800 for the genny, ( but of course you could buy a Kipor :Rofl1: )
    Charger .. again not cheap a 50A 4 stage will set you back £350 -£400

    payload.. I guess about 30kg

    I know where you are coming from Chris, a 12v 70A genny is cheaper and lighter but comes with the associated problems of being unregulated and requires some technical knowledge to use safely ..

    When it has a voltage regulator for battery charging and a governor on the engine to maintain the speed irrespective of the load when coupled to an inverter .. it may become a serious contender ..
     
  7. CHRI$

    CHRI$ Funster

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    just looked on ebay cheapest 2000 honda new is just over a grand:Eeek:
    dry weight 21kg.
    i had a problem with it not adjusting the throttle when a load is applied,but can get over this by just running it at high rev's to start with:thumb:
    most altenators have built in voltage regulators.
    but i did not build it as a direct replacement for a 230 volt genny,but as a fast battery charger:thumb:
    and im in the proccess of sorting out the noise,by changing the air intake:thumb:
     
    Last edited: Aug 13, 2011
  8. Road Runner

    Road Runner Read Only Funster

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    TBO I rely on 12 volt so a way of rapid charging the battery via an alternator is a brilliant concept:thumb:
     
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  9. CHRI$

    CHRI$ Funster

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    see thats all it takes, a comment from an itteligent(sp) and good looking buddy,and my spirits are well and truly lifted:thumb:
    i thank you kind sir:thumb:
     
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  10. Road Runner

    Road Runner Read Only Funster

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    A good idea deserved good feedback:BigGrin:

    It does all our solar panels do but far more rapidly and worth a bit of petrol, miles better than running a genny all day to achieve the same outcome.

    Couldn't think of anything rude to say:Wink::Laughing:
     
  11. CHRI$

    CHRI$ Funster

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    not like you john:Rofl1::Rofl1:
    do you want to be my marketing manager?:Rofl1:
     
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  12. scotjimland

    scotjimland Funster Life Member

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  13. Terry

    Terry Funster

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    No Chris you have the wrong idea :Rofl1: I go to the shops or pub etc, so the van charges the batts :thumb: As to starting the van -I make sure the starter batt is a good un :thumb: but if it let me down then the L/Btt takes less than a few mins to swop over to the starter one :Rofl1::Wink: I used to carry long jump leads but after abiut 3 yrs decided a adjustable spanner could do the same job :thumb: all be it with a little more effort :Eeek::Rofl1::Wink:

    Probably a lot better solution than carrying a engine/alternator and spare can of fuel :Wink:
    each to there own :thumb:
    terry
     
  14. CHRI$

    CHRI$ Funster

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    so running to the shop's is the best you can come up with,once i park my motorhome up it's there for the duration.and useing the water pump,for showering and the wife useing a hair dryer every day and telly on every night needs power so i need to put back that power quick,and dont need big bank's of batteries to run all that ,just needs a small 12v genny capable of chargeing fast,job done:thumb:
    i suppose it a bit like building your own motorhome when it's cheaper to buy one on the open market,but each to there own:thumb: i know, i build one and if i took my labour into account i would have been better off buying one:thumb:but you got the satisfaction of building yours,as i got the satisfaction building a little genny:thumb:
     
  15. haganap

    haganap Funster Life Member

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    As some-one that uses 12v more than 240 hook up, I think its a great concept. But, here is the adjustments I want on it before I let you trial it in my van.
    I want to be able to have it installed in a locker, an automatic start.

    Surely a power surge wouldn't matter if it was running 12v any way? or how would you load it?

    Until you update your plans, Im out :thumb:
     
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  16. CHRI$

    CHRI$ Funster

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    the auto start is an easy bit:thumb:
    installing it in a locker easy:thumb:
    no trial needed as it work's and does exactly what its suppose to:thumb:
    power surge.???
    i think people cant get their head around the fact that it is a battery charger and not a genny:Sad:
    the way it can be loaded is when its running and the wife decides to use a 1000w 230v hair dryer through the inverter as it will try to replace the power being used out the battery:thumb:
    must be something good about it, i have five more to build for other people:thumb:
    and the new ones will be lighter as i will be useing ally for the frame work:thumb:
     
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  17. scotjimland

    scotjimland Funster Life Member

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    indeed, but how will you control the charge rate and auto stop when battery is full . ?

    I alluded to this in a previous post.. it needs to be used by someone who has half a brain .. it isn't press button and forget ..
     
  18. CHRI$

    CHRI$ Funster

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    it controll's its own charge rate-it wont just chuck out 70 amps it will only put out what it needs to:thumb:
    on a slightly disgarged battery it will bring that battery back up to charge(14.8) on tickover,on a fully discharged battery say 11v it has to work harder but once the battery goes over 12v the alternator will work less right up untiil the bat is fully charged.
    jim!! just 1 Q do you know how an alternator works?

    if a running alternator is connected to a fully charged battery all day it will not try and charge it it will sit there doing nothing.
     
  19. scotjimland

    scotjimland Funster Life Member

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    Yes I do understand how they work and appreciate they are now self regulating .. when I asked about regulation I was thinking of the older types that had an external regulator.. my mistake.. :Blush:

    just one point, when the battery is fully charged , the voltage from the alternator will still be 14.4v across the battery .. yes ? Will this not boil the battery if left too long ?

    hence my question about auto off ..

    As an aside, what do you estimate the build cost is ?
     
  20. Snowbird

    Snowbird Funster Life Member

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    Am sure I have seen these at ex military sales years ago.
    Am not saying they were exactly the same,but the concept sertainly was.
    If my memory serves me right they used to be built into a small frame.
     
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