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Old Sep 06, 2011, 12:54 AM
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Australia, QLD, Ipswich
Joined Sep 2008
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What do you use to charge at the field?

So i'm wondering about a solution for charging my lipo's at the field when no mains power is available. Ideally i'd like to avoid using my car battery as this is a task the typical starting cycle car battery will not last long if constantly drained down. What sort of Ah do I need to be looking at 10, 20, 30 or bigger for a charging battery, obviously I go to the field with 2-3 charged batteries but If i'm just looking to top them up to get a couple extra flights in what do i need?

Now obviously this is dependent somewhat on what size batteries i use and how far I discharge them, but if we worked of a maximum of 5000mah per pack and I was doing 2-3 top ups what would think would be reasonable or what do you use.
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Old Sep 06, 2011, 01:11 AM
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United States, MO, Springfield
Joined Jul 2010
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deep cycles can deal with being well deep cycled rather well
most people at my field that dont use the mains run off a RV or boat deep cycle
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Old Sep 06, 2011, 01:38 AM
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Australia, QLD, Ipswich
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Yes, my plan is to get a deep cycle forgot to mention that in my post sorry. I'm really just trying to detirmine what size people have found works well so I avoid spending more than I really need to along with the extra weight of a larger battery to lift in and out of the car.
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Old Sep 06, 2011, 03:37 AM
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Letchworth, Great Britain (UK)
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I've just started field charging this year, and I've got an 86Ah deep cycle and a PL-8 charger. I'm usually charging two 3S or 6S 3900mAh packs in parallel, and only a maximum of four charges per session so far. I chose the size because it fits neatly in my flight box, but it seems to be more than enough for my needs at the moment.

You can do the maths if you want, by calculating the watt-hours of the charger battery (say 12v x 86Ah in my case = 1032 watt-hours) and the watt-hours of each flight battery (say 25.2v x 3.9Ah in my case = 98.2 watt-hours): So in my case, five charges of my 6S 3900mAh packs takes about half of my 86Ah battery's capacity. In practice, of course, I never have to charge a pack to its full capacity, so there's some leeway in that calculation.
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Old Sep 06, 2011, 05:23 AM
Rsetiegerd Uesr
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USA, AR, Cave Springs
Joined Apr 2005
3,088 Posts
I take 250Ah of deep cycle goodness to the field with me. The entire setup including charger, fuses, and everything else was around $300 and I never have to worry about having adequate power. The batteries themselves were around $110 from Walmart (I have two in parallel).

-Jay
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Old Sep 06, 2011, 07:07 AM
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United States, TX, Benbrook
Joined Oct 2005
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Our field has power but I still bring my deep cycle battery with me as a backup when there are a lot of electric flyers there.
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Old Sep 06, 2011, 07:19 AM
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Australia, QLD, Ipswich
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Quote:
Originally Posted by CyberJay View Post
I take 250Ah of deep cycle goodness to the field with me. The entire setup including charger, fuses, and everything else was around $300 and I never have to worry about having adequate power. The batteries themselves were around $110 from Walmart (I have two in parallel).

-Jay
Unfortunately the local battery shop here wanted 159 for a 35Ah deep cycle. Checking ebay and about the best I found was about $69 for 20Ah gel style deep cycle. So understandably with the prices getting around i'm trying to keep it too what i'll need vs want. I'd like 50-80Ah but think it's probably more than i'll need.
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Old Sep 06, 2011, 07:32 AM
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I use some generic car battery that I got at Costco for $60. That and a HobbyKing four-port charger. Been using that rig since last summer. Battery lives on a trickle charger when it's home.
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Old Sep 06, 2011, 08:34 AM
Rsetiegerd Uesr
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USA, AR, Cave Springs
Joined Apr 2005
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Quote:
Originally Posted by luke352 View Post
Unfortunately the local battery shop here wanted 159 for a 35Ah deep cycle. Checking ebay and about the best I found was about $69 for 20Ah gel style deep cycle. So understandably with the prices getting around i'm trying to keep it too what i'll need vs want. I'd like 50-80Ah but think it's probably more than i'll need.
Do your research.. not all "Marine" "RV" or "Deep Cycle" batteries are REALLY Deep Cycle batteries.. I have two Optima Gel type batteries under the hood in my truck, they are advertised as "Deep Cycle" but are not really capable of it. They are also only about 50Ah.

I would think 20-35Ah would be fairly useless as a deep cycle battery.. What are you going to do with it? Run an electric boat motor for 150 feet before having to recharge?

Golf carts are a good source of truly deep cycle batteries. As well as batteries specifically designed for electric boat motors. Note that there are "Marine" engine starting batteries too, these are NOT Deep Cycle.

It's a good investment though.. Buy a good battery now and you'll have power for flying for 4-6 years. You don't have to worry about crashing your deep cycle battery.

I nearly forgot, about 3 months ago I blew a fuse in my truck which caused the alternator to stop charging. At 10:30 at night my wife got stranded on the side of the road. I ran jumper cables from my 250Ah deep cycle batteries up to my starting batteries. It was good enough to get the truck home. Nice bonus to carrying spare batteries.

-Jay
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Old Sep 06, 2011, 09:24 AM
Chris
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United States, MO, Peculiar
Joined Aug 2011
27 Posts
I use a 75 Ah deep cycle for in the field, bought at wal mart for like $60. I am using 3s 11.1v bats in my planes ranging from 1800 mAh to 3300 mAh. So far no problems here.
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Old Sep 06, 2011, 05:49 PM
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United States, FL, The Villages
Joined Oct 2010
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Uhm, school me. I use my car battery at the field. You mean by charging my little 2200Mh 3S batteries I may be overtaxing that thing? I do as many as 6 of 'em and never had an issue with car starting.
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Old Sep 06, 2011, 09:34 PM
Rsetiegerd Uesr
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USA, AR, Cave Springs
Joined Apr 2005
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Quote:
Originally Posted by dkrhardy View Post
Uhm, school me. I use my car battery at the field. You mean by charging my little 2200Mh 3S batteries I may be overtaxing that thing? I do as many as 6 of 'em and never had an issue with car starting.
You're probably shortening the overall life of the battery. "Starting" batteries aren't designed to be run down, just to provide the current to start the car, then go back to a charging state.

If you were going to have that battery for 6 years, maybe now you'll only have it for 4 years. Just as an example.

-Jay
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Old Sep 06, 2011, 10:25 PM
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http://www.rcgroups.com/forums/showt...2#post17332376
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Old Sep 06, 2011, 10:29 PM
Lou
Well, that should buff out.
United States, VA, Waynesboro
Joined Dec 2005
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Quote:
Originally Posted by dkrhardy View Post
Uhm, school me. I use my car battery at the field. You mean by charging my little 2200Mh 3S batteries I may be overtaxing that thing? I do as many as 6 of 'em and never had an issue with car starting.
As mentioned a start battery is not the best option, but even more so there have been a number of cases where someone was charging a lipo in the engine compartment of their car when the lipo decided to catch fire. Tends to cause a lot of damage. Same as those that charge in the trunk of their car or the back of the van.
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Old Sep 07, 2011, 08:58 AM
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Joined Apr 2011
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I have charged all my bats for years on my cars battery, just start the car once in a while. no problems ever with the same optima bat. for 7 years
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