SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Apr 30, 2006, 09:13 AM
Registered User
Adelaide, Australia
Joined Apr 2002
141 Posts
Discussion
Generator for field charging

I am seriously thinking of getting a portable generator to charge my large battery packs at the field. I have a few 10S lithium packs and 30 cells Nimh. I've been looking at some 1000Watts out put portable generator/ inverter. They're not as heavy as my deep cycle battery. Any idea if the 1000watts is enough?
Arief is offline Find More Posts by Arief
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 30, 2006, 10:54 AM
Registered User
Milton Keynes UK
Joined May 2003
384 Posts
1000 Watts will let you charge a 10s battery at about 20 amps.

10s=approx 42v maximum.

42V x 20A = 840 Watts.

you have to remember that your charger is not 100% efficient, so you cannot charge at 24A (42x24=1000ish) because the generator will be supplying more than 1000 watts

Stuart




The question you need to ask yourself is: Would you and the other flyers at your field like a generator buzzing all day long while you/they fly nearly silent electric models???

Stuart
stu78 is offline Find More Posts by stu78
Reply With Quote
Old Apr 30, 2006, 11:21 AM
Registered User
sawatt's Avatar
USA, NY, Albany
Joined Jan 2006
155 Posts
Some would probably say...Hey, can I hook mine up too???
sawatt is online now Find More Posts by sawatt
Reply With Quote
Old Apr 30, 2006, 01:30 PM
Registered User
St. Mary, Maryland, United States
Joined Dec 1996
8,557 Posts
My 25 amp Radio Shack power supply has 430 watts input printed on the back, my 15 amper says 260. So a 1,000 watt generator (which seem to be really 1,000 peak and 900 continous!) will run 2 25 amp supply's at full load.

Look for quiet, the Honda EU1000i is very quiet @ 59 Db. Some of the others less so, of course the Honda is expensive - it better be quiet .
Chris True is offline Find More Posts by Chris True
Reply With Quote
Old Apr 30, 2006, 02:08 PM
UN Earth peoples true enemy
treehog's Avatar
Euroland
Joined Jan 2004
1,801 Posts
It is probabbly the only solution that isnt too expensive

generator 1000watts is very very nominal and if its from one of those big stores is prably a 1000 watss on a good day with a following wind....

I would tend to look at the issue from a heavy weight solution contious motor runs multiple recharge cost ratio solution versus lightweight solutions one or mayby two recharges per day with slower recharge rates

Taking the heavy weight solutions first

I have a lot of marine sailing boat experience with generators from 500 watts to 50kw and the numbers they claim are mostly made up by accountants who chose not to listen to engineers so as to flog overrated crappy gear at higher prices make heaps of money for accountants and lay off the contract engineers

Most of the 1000w generators when connected to a 1000 watt drill often cut out as surge loads temporaly reach more than 1000 watts

We had a short circuit solution which drove the throttle to max first then loaded it with drill and that sometimes helped but continuios demand 1kw often grilled generators in hot climates

At tick over the generator 1000 watt generator makes mayby 500 watts until you speed it up and the load throttle automatic solutions often dont work so manual overide is the name of the game to stop surge overload cutting out issues

Probably best to forget invertors they are mad money and you often lose 20% so your at some 800watts and often turn into instant hot barbies in hot
climates as they are realy trannistors that can easly overheat and a 1kw invertor is probably an ok 500 watt invertor

Tranformers such as power stabilisers often work better and tend only to trip out if things go pear shaped but a tad pricy so if you can get computer power supply type with 500 watts and charge slower is a good lightweight soulution with a 1000watt generator and lots of cooling off rest stops

Having had bad experiences in the marine world genrating power the best rule was simple a 1000 watt generator is probably an ok 500 watt generator and unlikly to be 1000kw so we always doubled the power generator where possible or reduced the drain to match half load and 1000watt drill was probably rely 1.5kw not loaded and 2kw loaded so generation is half and consumpion is doule and your getting the true piture

We always switched off the 7kw aircon units if we wanted to turn on surgy appliance like washing machines so it was be cool and be stinky in dirty clothes or be hot and sweaty in clean clothes how the lifes of sailors have changed since the good old days of bucket shower

generator 1000watts is very very nominal and if its from one of those big stores is prably a 1000 watss on a good day with a following wind....


Most of the 1000w generators when connected to a 1000 watt drill often cut out as surge loads temporaly reach more than 1000 watts

We had a short circuit solution which drove the throttle to max first then loaded it with drill and that sometimes helped but continuios demand 1kw often grilled generators in hot climates

At tick over the generator 1000 watt generator makes mayby 500 watts until you speed it up and the load throttle automatic solutions often dont work so manual throttle overide is the name of the game

Probably best to forget invertors they are mad money and you often lose 20% so your at some 800watts and often turn into instant hot barbies in hot
climates as they are realy trannistors that can easly overheat

Tranformers such as power stabilisers often work better and tend only to trip out if things go pear shaped



So to get a sure 1000watts buy a 2 or better still 2.5 kilowatt generator and that will probly run for years to come

Then you hit a new problem weight and fuel consumption of that type jumps and cost benifit ratio from generator compared to a large truck or tractor obtained second hand battery is starting to be marginal

The happiest boats I knew usualy had a twin lead acid batterry of some 800amp hour or some 20 times larger than the average car 40 amp hour which was topped up by the inboard 65 amp generator when some 10% capity was used up usuasualy every day and more if voltage dropped more than usual as deisel inboards dont use much fuel and often cheaper than petrol 2kw generator and no fire fuel issues from petrol types and lead cells near keels help stability for boats


Humungus battery of 800 amp hour will supply steady 80amps for a few hours but its best to own a pick up truck and forget lugging it onto the field unless its twenty 40 amp batteries ganged together but can take serious heavy weight use year in year out

The rule for cheapo lead acid types is never exceed 10% or 1/10C power drain relitive to battery capassity for any extended period eg 10 mins plus and dont use more than 50% of cappasity rfegularly as deep dischaging lead acid dosnt like to do freqently and rechage rates at 10% or 1/10C
Fast charge from car or truck generators is only a quick top up and deep rechages causes drastic shortning of life for lead acid batteries

In a typical car start situation the lead acid is stressed for some 10C but only for a few seconds and rechage rates of 1C for a few minutes in noral car use


Alternitives marine deep discharge type batteries are normaly tooooooo expensive are usualy 20% heavier per amp hour rating than lead acid and dont like deep dischages either and or fast recharges much to the contary propaganda if you want a 1000 cycle life

gel cell types are often used in go cart golf cart and electric scooter applications and seem to tolerate closer to 1C in bursts so suspect 1/2C is possible semi continious light weight solution 45 min discharge rate with long rest period but wouldnt be suprised if the best ratio was 1/5C or 20% capasiity for long life use heavy weight solutions and at that premium price unlikely to be useful option
If gel cell can tolerate light weight solution 50% drain or 1/2C for 1000watts you would need some 200amphour and euro prices suggest some 300 to 600 plus or some aus$ 1000 plus solution

If you ran the motor of your pick up truck at some 2000 rpm not tick over as that dosnt supply power to battery generator charger the pick up trucks 35 amp generator will keep the power going longer on your battery combo and you could look to reducing to to 400amp hours lead acid battery if you were only doing a few charges a day for a lighter weight solution or mayby 100AMP hour gel cell solution but probably couldnt hack heavy weight requirements

Better still get a truck battery generator 65 amp hour and retro fit that to your pick up truck to stop generator getting grilled from continious power demands as those generators were normaly meant to supply burst fast charge power requirments

I have seen some boats rig up a 65 amp generator to a small petrol engine from lawn mowers etc but never got to hear the results from this practice but suspect if they were careful not to exceed 50% of rated abilities it wouldnt grill to easly

From memory you need some 5 hp to drive a 35 amp generator and ten HP for a 65 amp but less will probably work but the smaller motor will be going very fast and making lots of noise to generate this much power so most used over size motors going more slowly for more heavy weight solutions

Solutions vary according to your spend ratio meckanical abilties car types you own field where you fly from etc

In germany they sometimes get local electricity supply run up to the club house expensive but lots of members or local consils chip into cost

Other clubs leave large truck batteries on site and rotate them around with charging from home back breaking but workable solution for ten cell stuff

With 30 cells if there is no possibilty to get electricity fed to club house or if you float around lots of clubs then the solutions are lots of thirty cell packs precharged and topped up on field from car battery with engine running at 2000 rpm and or mobile generator 2kw types or big truck battery's ganged together or smaller amp hour hour gel cell lead acid types

An option I might try out in the future for myself if i start to get into the twenty cell plus areana will be to use car motor running 2000rpm and voltmeter coupled to a home brew 7 amp or 10 amp 2p10s nicads pack and or for more heavy weight uses use a 1000watt better 1500 watt generator if such exists driving a high 30amp wall car recharger through same nicad pack and try to rechage using less power wher possible such as 500 watts

This solution is dependent on that 7 or ten amp nicad types can absorb some 2C recharge rates and dischage rates of 15C and would rely be a sort of shock absorber smothing the current for model rechager and possible light weight solution than 800amp hour lead acid solution but suspect if i drift back into marine areana again will do float planes and live on boat with realy humungious big lead acid scronged around from marina

Ralf
treehog is offline Find More Posts by treehog
Reply With Quote
Old Apr 30, 2006, 04:38 PM
nooobama
United States, PA, Stroudsburg
Joined May 2004
984 Posts
Coleman sells an 1800watt quiet (not as quite as the Honda or Yamaha) that is 1/2 the price of the Honda 2000watt which is what I use for tire warmers at the track. Home depot has them if you want to check them out. Most of the better gen's have the dile down feture that will let the gen run at lower rmp when it doesn't need full power. That alone will help keep the noise down.
finishman2000 is offline Find More Posts by finishman2000
Reply With Quote
Old Apr 30, 2006, 05:38 PM
McClintock on rcu
jaeder's Avatar
Brighton, Massachusetts
Joined Jul 2004
279 Posts
Note when recommending stores and brands, that australia may not have the same as the US/Canada. Everyone should own at least a small generator, especially in a world at war.
jaeder is offline Find More Posts by jaeder
Reply With Quote
Old Apr 30, 2006, 06:45 PM
Registered User
Adelaide, Australia
Joined Apr 2002
141 Posts
hey guys, Thanks for the responses. the generator I'm looking at is here: http://cgi.ebay.com.au/ws/eBayISAPI....MEWA%3AIT&rd=1

It's a digital inverter genrator. funny thing about it is that max amps output is 10 Amps, whereas I'm powering my schulze with a 20 amp PSU at home.
Arief is offline Find More Posts by Arief
Reply With Quote
Old Apr 30, 2006, 06:59 PM
Registered User
Joined Apr 2006
634 Posts
Powering an transformer from a 900 nominal generator will yield about 700-800 watts at the 12 volt end. thats good for about 58 1/3 amps upto 66 2/3 amps thats plenty to power 3 chargers at full load. Thats shooting at $600 or more plus gas (ouch)
charge1(ds) is offline Find More Posts by charge1(ds)
Reply With Quote
Old Apr 30, 2006, 07:32 PM
Registered User
Futurase's Avatar
Fayetteville Municipal, Arkansas, United States
Joined Sep 2004
574 Posts
I have a Honda EU2000i. I did not buy it for R/C use and do not need it for that. When it comes to generators there is Honda and then there is everyone else. I could give you plenty of REAL reasons why. The Honda 1000 watt generator is small, light and will run as smooth silk. If you buy a Honda you will never regret it. Don't listen to the garbage about inverters. I would not own a generator that did not have one. The power out of a Honda generator is cleaner than what comes out of your wall at home I can almost promise you.
Futurase is offline Find More Posts by Futurase
Reply With Quote
Old Apr 30, 2006, 08:17 PM
Registered User
St. Mary, Maryland, United States
Joined Dec 1996
8,557 Posts
Quote:
Originally Posted by Arief
hey guys, Thanks for the responses. the generator I'm looking at is here: http://cgi.ebay.com.au/ws/eBayISAPI....MEWA%3AIT&rd=1

It's a digital inverter genrator. funny thing about it is that max amps output is 10 Amps, whereas I'm powering my schulze with a 20 amp PSU at home.
10 amps is on the DC circuit. That's not what you want to use, you want to use the AC circuit with the power supply or supplies you use at home.
Chris True is offline Find More Posts by Chris True
Reply With Quote
Old Apr 30, 2006, 08:22 PM
Registered User
Joined Apr 2006
634 Posts
Its true inverters produce the cleanest electricity. Now about air... ...too late!
charge1(ds) is offline Find More Posts by charge1(ds)
Reply With Quote
Old Apr 30, 2006, 10:49 PM
Registered User
Adelaide, Australia
Joined Apr 2002
141 Posts
Guys,
Thanks again. Futurase, I will look into the honda a bit closer
Arief is offline Find More Posts by Arief
Reply With Quote
Old Apr 30, 2006, 10:56 PM
Registered User
Zebulon, NC
Joined Aug 2000
5,086 Posts
I have had the Honda 1000 watt for a few years, never had any problems and I have used it for field charging many times. I even use it to power my mini refridegerator in my trailer so I have cold drinks at the field and it requires a 1700 watt startup but the Honda runs it fine.
Steve H. is offline Find More Posts by Steve H.
RCG Plus Member
Reply With Quote
Old Apr 30, 2006, 11:25 PM
fortune favours the bold
gjestico's Avatar
Vancouver Boundary, Canada
Joined Dec 2001
367 Posts
You can get 1000 watt cheapie made in china generators new for around $200 on ebay. They are like 50 lbs, but they do work and they have ohv engines .

http://cgi.ebay.com/NEW-COMMERCIAL-1...QQcmdZViewItem

I have one of these and it does work. My power test consited of hooking up a 1000 watt hair dryer and it will pull the load, with throttle to spare. Combine one of these generators with an IOTA 55 amp power supply ($100) and you have a lower cost field charging setup. The hondas are real nice, but cost $700 new.

Greg
gjestico is offline Find More Posts by gjestico
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion a new idea for field charging? kmp647 Batteries and Chargers 16 Mar 20, 2007 01:01 PM
Discussion Which charger for field charging stever2006 Batteries and Chargers 1 Aug 06, 2006 01:12 PM
Used Lead Acid Helicopter Battery for field charging... stu78 Batteries and Chargers 9 Jan 29, 2004 10:31 AM
Alternatives to Car Battery for Field Charging jpv11 Beginner Training Area (Aircraft-Electric) 10 May 05, 2003 11:44 PM
Auto Battery Booster Pack for field charging? denete Electric Plane Talk 7 Mar 10, 2002 10:15 AM