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Charging Batteries in the Field

Old 12-17-2007, 12:31 AM
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flash89
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Default Charging Batteries in the Field

Greetings all,


I've recently made my first R/C airplane purchase, a Hobbico Electristar, and I am eagerly awaiting some nice weather to go out to the field and try it out.
The common Electristar battery configuration uses 2 3000 Mah NiMh packs and from what I've been reading that is about 9-12 minutes of flight time. These are probably the batteries I will go with. I don't plan on keeping this plane any longer than it takes for me to get enough skills to fly something a little more exciting, so I'm not going to invest in Lipos for this plane.

I've been into R/C cars for some time and already have a superbrain 977 charger that can handle the batteries for the Electricstar.

With my cars, I always just carry enough batteries with me for the day, but a single $50 4000Mah pack for my car lasts me 30+ minutes. Four of those packs at a total cost of ~$200 last me a good 2 hours, which is about as long as my wife let's me out of the house to go play with my toys. :-)

For about that same $50 I'm only getting 9-12 minutes of flight time with the Electristar. So for that same 2 hours of run for my plane, the battery cost would around $500 which seems kinda high.



Now, my question is this. Do most of you electric R/C pilots out there typically have enough batteries on hand to last the day, or do you charge in the field? If you charge in the field, what sort of setups do you use?
Is there typically Electric available at the field?
Do you charge from your Car battery?
Do you have larger batteries you charge your packs from?
Some sort of available alien technology I'm not familiar with?


Thanks for taking the time to read my question.
Old 12-17-2007, 01:58 AM
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calvino
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Default RE: Charging Batteries in the Field

what most pilots here do (i have read) is have a few packs, one guy has an ingenious idea, have 3 packs (he runs a Nextstar), he flies for a bit, but doesn't DRAIN THE PACK FULLY, so it charges faster, he brings it in for a landing, has a bud slap that pack in a cooler with that reusable ice pack stuff, and gets one fresh off the charger, so by the time he is done with the new pack, he slips the "cooler pack" into the charger..... and so on and so forth, as for you, since it uses 2 packs, I don't think that is the most efficent route, I would maybe have one or 2 extra "pairs" of packs, if you can talk the wife into one, hey, Christmas is around the corner...., as for charging, I guess they use like a SLA (sealed lead acid battery), same thing your car runs, only it doesn't rip your arm out of it's socket as you drag it over, they work good, a simple search can turn up a few, also check with the local phone company, they may have some lying around that are perfectly fine, but they changed them out for safety's sake[8D]
Old 12-17-2007, 05:47 PM
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Default RE: Charging Batteries in the Field

When you drop by the field I fly at... you can look at the parking lot and tell what cars the electric plane pilots are flying... because their hoods will be up... charging batteries.

You can also invest in a marine quality lead battery (beefy car battery)... that way you don't risk draining your car battery and leaving yourself stranded. Plus... if you charge with a separate battery you can move it away from your car.. less risk of a catastrophic fire should you charge an ornery LiPo.
Old 12-17-2007, 07:10 PM
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Default RE: Charging Batteries in the Field


ORIGINAL: SackOHammers

When you drop by the field I fly at... you can look at the parking lot and tell what cars the electric plane pilots are flying... because their hoods will be up... charging batteries.

You can also invest in a marine quality lead battery (beefy car battery)... that way you don't risk draining your car battery and leaving yourself stranded. Plus... if you charge with a separate battery you can move it away from your car.. less risk of a catastrophic fire should you charge an ornery LiPo.
which would really mean, no easy trip home, yeah, it is one thing to jumpsart your car, it is another to have a charged wreck towed, the few times I have been down to a flying field, everyone seems to use Lead Acid batteries, like the ones designed for RC car starterboxes, they seem to last a while, and are much lighter than a marine battery
Old 12-19-2007, 12:32 AM
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Default RE: Charging Batteries in the Field

Those little latern batteries don't let you charge a whole lot.
Old 12-19-2007, 07:35 AM
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Default RE: Charging Batteries in the Field

ORIGINAL:
Now, my question is this. Do most of you electric R/C pilots out there typically have enough batteries on hand to last the day, or do you charge in the field? If you charge in the field, what sort of setups do you use?
Is there typically Electric available at the field?
Do you charge from your Car battery?
Do you have larger batteries you charge your packs from?
Some sort of available alien technology I'm not familiar with?


Thanks for taking the time to read my question.
I usually have 2-3 battery packs that will fit any one of my planes. Normally several planes use the same packs so I don't need a zillion battery packs. I also have 2 chargers with me.

In normally go to the flying field for 4-8 hours at a time so having enough packs for the day was never part of my plan. Having enough packs to handle a reasonable charge rotation is what I look for.

Mostly I fly Lipos these days and most of my planes are flown at 1/2 to 2/3 throttle most of the time. I can get 15 minutes or more of flying time that way.

Many are electric gliders where I make a 30 second to 1 minute run to altitude then I power off and look for thermals. Even if I don't find much lift, I can usually get 8-12 climgs like that so 30 minutes on a pack is common and I can easily go over an hour on a pack.

I you fly a pack, then it goes on a charger.

Fly the second pack, then it goes on the charger. The first pack may be done at that point.

If I have a third pack, I will go up again, or I switch to a plane that uses a different pack.

With NiCds there was a pretty fast turn around. In as little as 20-30 minutes, charging at 2-3C, a pack was ready. However they were heavy and did not last very long.

NiMh you could finish a pack in about 30-40 minutes at 1.5-2C charge rate. They took longer, but for the same weight, they lasted about 40% longer so it was a good balance.

Lipos take 45 minutes to an hour to charge, depending on your charger and the pack. Some of the newer lipo chargers claim to be able to safely charge at up to 3C. That would get lipos back to the charge rate of NiCds. My fastest lipo charger does 1.4C.

So it is a combination of your style of flying, how long you stay and how long your packs last. But I always charge at the field and I typically have two chargers going.


If you are getting the Electristar RTF, then you have a choice of lipos or Nimh. You only reason to go NimH is if you can leverage some of your car batteries and chargers. But those are likely to be 6 cell packs and either te wrong shape or too heavy for the plane.

Based on the recommended packs, the two NiMh packs, together weight 30 ounces. The two Lipo packs weigh about 12.5 ounces. 17.5 onces difference, in a plane is HUGE. Even though the two 2 cell Lipo packs will be slightly lower in voltage, I think you will get better performance on the plane with the lipos due to the lighter weight.

I don't know what the ESC or BEC are rated for but you can likely fit 3 cell lipos in there which will give you GREAT performance compared to the NiMh packs and still probably be 10 ounces lighter. It might be an upgrade for later as the ESC may not be able to handle the 3 cell packs or you might have to change the prop so you don't over amp things. But that is a consideration for later.

Go LIPO

If you get into planes, you will go to lipos or A123 packs eventually. The capacity to weight ratio is just too good not to go there. In cars, it may not matter, but in planes weight is everything.

If you are going to be flying planes of similar size and weight, just get lipos that will fit the current and likely future plane. Then invest in a second charger and a third pack for the next plane.
Old 12-23-2007, 07:25 PM
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Default RE: Charging Batteries in the Field

I use a car jumpstarter to charge batts. with. Has two cig. outlets and an inverter where I plug the hot glue gun in for repairs. It has a 20 AH batt so it lasts all day. And I jumpstart those cars that have been charging batts all day.

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