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Old Dec 17, 2008, 03:51 AM
How high does it go?..duh
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What generator to get?

Hi there guys, I'm looking at getting a generator to charge my A123's in the field, just wondering what size/type of generator to get? I'm using this charger (I may get an extra one if I can run two at once)
http://www.unitedhobbies.com/UNITEDH...alance/Charger
and looking to charge 4s A123 packs (at 10 amps if possible). Whats the best way?..Find a generator that chucks out 12v and as many amps as possible and hook onto that, or put my mains transformer on the 230v side of the generator and then connect the charger?
Is there a need to get a special generator with noise cancellation etc or will any old generator do?
What sort of output from the generator should I be looking for 850w, 1000w 2000w etc?
Sorry for all the questions but I dont have a clue about generators.
Cheers and merry xmas
Ian
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Old Dec 17, 2008, 05:04 AM
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Letchworth, Great Britain (UK)
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Have you considered the alternatives? A deep-cycle marine battery (it can tolerate being deeply discharged before it gets recharged, unlike a car battery that is best if it's constantly recharged by the alternator) at the flying site, and recharged at home, is probably better. Less noise and fumes in the pit area to annoy the other flyers, if you're in a club

To get an estimate of what size you need, your A123 packs are nominal 13.2 volts and 2300mAh capacity, so you theoretically need a 12v battery with 2530mAh (2300 x 13.2/12) capacity for every charge you intend to do in a day's flying. Add something for losses in the system, and you'll see that a 50Ah (50000mAh) battery might give you something like 20 full charges

If you're really set on a generator, and intend to charge at around 10A, you'll theoretically need about 11 amps from a 12 volt outlet, which equates to 132 watts. I see that the charger you've referenced is rated at 250 watts, so you might as well at least match that with the generator. But I'm not sure how well the charger will cope with a 12v supply from a generator -- the couple of chargers I've used are quite fussy about their input voltage, so if it sags under load or rises under no-load the charger might trip out due to invalid input voltage
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Old Dec 17, 2008, 06:02 AM
How high does it go?..duh
Pigs dont fly's Avatar
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Thanks for your reply abenn, I need to be able to fly continuously and always have cells available so the marine battery is a non starter as it will go flat.
The '12v out' supplies I've seen on most of the suitcase type regulated generators dont put deliver many amps (usually less than 10), so was wondering if I could use the mains voltage side and use my mains transformer..or would this not work?

Anyone already doing this with a generator?

Many thanks
Ian
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Old Dec 17, 2008, 06:03 AM
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Miramar, Florida
Joined Jul 2007
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Quote:
Originally Posted by Pigs dont fly
Hi there guys, I'm looking at getting a generator to charge my A123's at the field, just wondering what size/type of generator to get? I'm using this charger (I may get an extra one if I can run two at once)
http://www.unitedhobbies.com/UNITEDH...alance/Charger
and looking to charge 4s A123 packs (at 10 amps if possible). Whats the best way?..Find a generator that chucks out 12v and as many amps as possible and hook onto that, or put my mains transformer on the 230v side of the generator and then connect the charger?
Is there a need to get a special generator with noise cancellation etc or will any old generator do?
What sort of output from the generator should I be looking for 850w, 1000w 2000w etc?
Sorry for all the questions but I dont have a clue about generators.
Cheers and merry xmas
Ian
Last year before SEFF I purchased a Yamaha EF1000iSC 1000 watt inverter generator to be able to charge at the field. The one thing I was hearing was no one wants to hear the typical 5,000 watt Home Depot-type generator that is quite loud, especially for extended periods. Likewise I heard that electronics can be finicky on a typical generator.

All of this lead me the the small inverter generators made by Honda and Yamaha to name a few. They generate 12 VDC and invert it through an inverter for 100 VAC, making clean power that can run computers and sensitive electronics. Best of all they are small (26 lbs) and super quiet. You can run it 10' away and have a normal conversation as the generator is some 55 dBA, very quiet!

Jack
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Old Dec 17, 2008, 06:14 AM
How high does it go?..duh
Pigs dont fly's Avatar
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Hi Jack, yes thats the sort of thing I was looking at. Can I ask if you charge using the 12v output or put a transformer and then charger on the mains voltage output? I really need a fast 10amp charge in the field, as I will be flying all day every day.
Thanks
Ian
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Old Dec 17, 2008, 09:01 AM
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"Last year before SEFF I purchased a Yamaha EF1000iSC 1000 watt inverter generator to be able to charge at the field. The one thing I was hearing was no one wants to hear the typical 5,000 watt Home Depot-type generator that is quite loud, especially for extended periods. Likewise I heard that electronics can be finicky on a typical generator."

I'll second jfetter's post on this aspect. Several of us have the Honda 1000Ei, which is similar to the Yammy and very quiet. We have also gone to using the MasTech 2050 power supply as a charger exclusively for getting the fast charge into the A123's. This connects to the AC outlet.

BTW, the 12v outlet is limited to about 150w, so you need to go the AC route. Tex.
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Old Dec 17, 2008, 09:34 AM
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Quote:
Originally Posted by Pigs dont fly
Hi Jack, yes thats the sort of thing I was looking at. Can I ask if you charge using the 12v output or put a transformer and then charger on the mains voltage output? I really need a fast 10amp charge in the field, as I will be flying all day every day.
Thanks
Ian

On most small inverter generators, the 12VDC output is unregulated. If you read the manual, it states that it should only be used in emergencies to boost a dead car battery.

Caution would dictated conneting a 110/220V AC to DC power supply in order to power your chargers from a generator.
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Old Dec 17, 2008, 09:54 AM
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I used a small, cheap two cycle 1200W generator all last year. It used a two cycle engine and was quite noisy but no one complained. You could put an extra muffler on it to quiet it down.
I made my own charger. I just used a full wave bridge I got from ebay in series with a Variac from the 110V/220v generator output. I just adjusted the Variac to get 10A to the batteries and monitored the voltage on the batteries and stopped charging when the voltage reached 3.8V/cell. At 10 A it took less than 15min to charge the cells
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Old Dec 17, 2008, 10:42 AM
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The Northeast Kingdom, Vermont
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Why not use that expensive "generator" you drive to the field to maintain a deep cycle marine battery. You would not have to run the engine all that long to keep the deep cycle battery from going flat
Cheers,
Pete
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Old Dec 17, 2008, 11:04 AM
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Quote:
Originally Posted by dirtybird
I used a small, cheap two cycle 1200W generator all last year. It used a two cycle engine and was quite noisy but no one complained. You could put an extra muffler on it to quiet it down.
I do the same to charge my A123's at the field with a Mastech power supply. I paid about $100 at Pep Boys. It's no noisier than the glow and gas engines running in the pits. And since it's charging A123's it only runs for 12-15 minutes at a time. I charge 7s2p A123's at 15 amps and 27 volts. If I had to do it over again I might have gotten the Mastech with dual 30v outputs instead of the model with a single 50v output. The generator doesn't seem to care what voltage you run but runs rough at higher amps. With that model I could charge each 7s pack at 27volts and 10 amps.
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Old Dec 17, 2008, 04:51 PM
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Miramar, Florida
Joined Jul 2007
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Quote:
Originally Posted by Pigs dont fly
Hi Jack, yes thats the sort of thing I was looking at. Can I ask if you charge using the 12v output or put a transformer and then charger on the mains voltage output? I really need a fast 10amp charge in the field, as I will be flying all day every day.
Thanks
Ian
I use the 110VAC side to power my 25 Amp DC power supply. The limit is 900 Watts which is more than enough to power all of my chargers...

Jack
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Old Dec 17, 2008, 04:53 PM
HAL... Open the damn doors!
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Miramar, Florida
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Another benefit of these little inverter generators is they are 4 cycle, no mixing oil, just stop by the gas station and fill the tank!

Jack
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Old Dec 17, 2008, 06:39 PM
jrb
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Edina, MN, USA
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When away from my home field and there's no AC, I power my MasTech 5020 via a Vector 2000W modified sine power inverter running off my 2007 Explorer.

My wiring harness let me charge at the full go of 20amps; also gives me the safety of an Arming plug too!

A search on me and vector; 17 threads: http://www.rcgroups.com/forums/searc...rchid=17647025 .
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Old Dec 17, 2008, 10:09 PM
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I've looked at and evaluated all the options and although I don't have one yet, when the time comes I'll get the Honda, most likely the EU2000i.

Although the initial purchase price is a little steep, I'd rather not spend my time dealing with buying, carting, and charging heavy batteries or leaving my car running at the field or taking the chance of damaging my alternator. Anyone check the price of having an alternator replaced on a late model car recently? It's more than half the cost of the Honda. Plus I can use the Honda to power a fan or other appliances at the field and it will come in handy when the power goes out. Lastly, like most Honda products, they have a good resale value in the event I no longer need it.
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Old Dec 18, 2008, 02:24 AM
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Letchworth, Great Britain (UK)
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But, taking an i.c. generator to the field rather defeats the objective of going electric, doesn't it? And a 47lb generator sounds just as heavy to me as a medium size deep cycle battery ....

I have to admit, that Honda looks like a very nice piece of kit. But its price would keep me supplied with deep cycle batteries for the rest of my life
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