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Old Jan 06, 2008, 02:57 PM
rcbrust is offline
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Request for Opinions on RAM3 Batteries


Guys,

I plan on offering a LiPo cell as an accessory for the RAM3 altimeter. As shown below, the cell will come with a lead and connector which will plug directly into the RAM3, making it a self contained package. In other words, you can plug the battery into the RAM3, wrap them up in a piece of foam, and stick them wherever you want in your glider. No need to connect to your receiver.

Now, the question I have is, what size LiPo cell should I go with? I'd like to pick one size so that I can buy them in quantity and keep the price lower. Currently I've settled on two cells, both of which are shown below with a RAM3 and a penny for size reference.

The smaller cell on the top is 30mAh and will run the RAM3 for about 5-6 hours. The cell on the bottom is 50mAh and will run the RAM3 for about 9-10 hours. The size and weights of all three units are as follows:

RAM3: 0.75" long x 0.60" wide x 0.33" thick - 2.2 grams

30mAh Cell: 0.82" long x 0.48" wide x 0.20" thick - 1.3 grams

50mAh Cell: 0.82" long x 0.56" wide x 0.28" thick - 1.8 grams

So, do you think it's worth half a gram and a slightly larger size to get the extra 4 hours of run time? Or, do you think that 5-6 hours is plenty and it's better to keep the size and weight to a minimum?

Thoughts and opinions are invited.

Thanks,
Randy
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Old Jan 06, 2008, 03:20 PM
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Randy,

I'm for the 50 mah option. Minimal weight gain for many more hours of flight time. Plus, easier not to blow up on charge (until you come out with your charger!)

John
Old Jan 06, 2008, 03:32 PM
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Hmm... I don't know if that's a completely unbiased opinion... considering that 50mAh cell in the picture is yours...

And yes, John makes a good point. Thanks for reminding me. I have a little inexpensive charger designed for safely charging these little cells. It will be a little while though until I can get the pc board laid out and get it into production.

Randy
Old Jan 06, 2008, 04:07 PM
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I like the idea of the 50mah in that there is quite a bit of lattitude in the time available. You could potentially use it for a whole weekend if you unplugged between sessions.

How much data (time) will the Ram3 store at say 2 points per second)?

Rick
Old Jan 06, 2008, 04:25 PM
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Quote:
Originally Posted by ThermalBuster
How much data (time) will the Ram3 store at say 2 points per second)?
Record times are (approx):

1 sample/sec rate - 18 hrs

2 sample/sec rate - 9 hrs

5 sample/sec rate - 3 hrs and 35 mins

10 sample/sec rate - 1 hr and 45 mins

Randy
Old Jan 06, 2008, 04:32 PM
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For all of us dlg guys saving the weight is a good thing. And most of us have a way to charge at the field.Either way it looks awesome.
Old Jan 06, 2008, 09:21 PM
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I'd like to see the 50mAh option.
Old Jan 06, 2008, 09:47 PM
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50mah for me .. looks like a great unit.. what will I do with my ram2 now?

cheers jeff
Old Jan 07, 2008, 08:07 AM
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The 50mah looks like a nice fit to me. Nothing wrong with the 30mah but the 50 isn't that much bigger or weightyier and then you just start it and forget it.
Old Jan 07, 2008, 08:37 AM
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I just realized that I forgot to include one other critical piece of information. At this point in time, the the two cells cost the same.

Randy
Old Jan 07, 2008, 08:43 AM
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wishes this caption was longe
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randy i have one of your older lipos that came with the RAM 2. I have never used because i can't charge it safely. that problem is way more important than battery size.

I suppose you need to keep the gram counters happy. better go small or folks will be mad that it's "too heavy"

If it's not the weight folks will complain about the price of the bigger battery...

there just aren't enough rolling eyes smileys in the world.....
Old Jan 07, 2008, 09:11 AM
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I vote for the 50mah cell.

Also I suggest you make your charger have a reasonably easy option (eg select jumper, or change resistor) to change the charge current between say 50ma and 20ma, as there are many small cells being used nowadays (eg on indoor toy type helis), and few small chargers.

Neil.
Old Jan 07, 2008, 04:48 PM
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That's an interesting observation Neil! I have one of those tiny heli's that charges off of the AA powered transmitter. It would be fine if the charger for the 30 or 50mah battery were powered by AA cells rather than having to clip onto a car battery. Any chance?

Rick
Old Jan 07, 2008, 05:09 PM
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It would be possible to do. But, unless I'm convinced otherwise, I think that most people would rather just clip it onto a 12 volt source.

Randy
Old Jan 08, 2008, 11:21 AM
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Can't say that I have a good argument for doing something other than a charger powered by 12v. Just seemed like it might be easy to charge off of a 4.8 volt receiver pack or something. Oh, nevermind........


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