Posted: 2/2/2012 10:41:40 PM EDT
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So, tonight I was pondering... How can we lower the weight of an EMCOMM box? Well, most of the weight is in the batteries. Well, I participate in airsoft, and have begun using LiPo batteries. I was thinking, maybe this lipo battery can be adapted to HAM radio... Running it across my volt meter, an 11.1v battery fresh off the charger give 12.5v. Now, I know that the SLA batteries used are rated at 12v, but I don't know the max current deliverable...
Now, to me, LiPo batteries have a funny nomenclature. The battery sitting in front of me says 11.1v 2200mah 20C. I know what the first 2 parts mean, but what does 20C mean? Some googling told me that the 20C rating is the constant discharge rating. Multiply the C rating by the Ah of the battery gives you the Ah discharge rate. So my battery will discharge up to 44Ah. Most mobile 2m radios draw a maximum of 15A during Tx (and no one is talking 100% of the time). So, in my non-electronics minded mind, this could work. You can get a 4S battery which is rated at 13.2v with 8400mah. I think 2 of those wired in parallel would be awesome. One of the reviews says a guy is using 2 as starter batteries for his motorcycle with a nominal voltage of 13.9v. Here is a link to the battery: http://www.hobbyking.com/hobbyking/store/__14074__ZIPPY_Flightmax_8400mAh_4S2P_30C_LiFePo4_Pack.html That battery only weighs 1kg (2lbs) whereas a 12v 12ah SLA weighs something like 9lbs. Pretty good weight savings... So, am I on to something? Or am I just really really sleep deprived? |
| The "c" rating means that the battery can for short periods of time deliver a high amperage. In your example a 2200mah battery with a "c" rating of 20 will deliver 44 peak amps. Although the "c" rating is supposed to be a constant, the battery will have a very short life span if driven at the maximum "c" rating. But you are on to something which I already do, I have adapted a AA battery case for my Yeasu VX-6r to run off of 7800mah 2s Thunder Power RC batteries. It runs forever!! I am in to RC Helis so the idea to run the VX-6r came from using these types of batteries. You want to be careful about the voltage that your radio can handle as when fully charged Lipo batteries have a much higher voltage than the nominal rating. You will have to get a Lipo specific battery charger to charge them properly, one that will balance the cells so that battery will be charged properly and ensure longevity. Hope this helps. |
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edjo69: I'm very familiar with Lipo batteries and their quirks. I have a charger already.
I guess the only way to really find out is to buy a couple batteries, wire them up, and test it on a mobile radio... Now to just find a mobile radio... Anyone want to donate one to the cause? |
| if I were to do this, I would probably put some sort of voltage regulating circuit in between the LiPo and my fancy schmancy radio to prevent the aforementioned higher voltage quirks from frying anything expensive. something simple to keep it at 13.8VDC and below. |
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Quoted:
if I were to do this, I would probably put some sort of voltage regulating circuit in between the LiPo and my fancy schmancy radio to prevent the aforementioned higher voltage quirks from frying anything expensive. something simple to keep it at 13.8VDC and below. Fully adjustable inline voltage regulators are readily ava. at any hi-end RC heli/airplane web-store. Once you get familiar with lipo's they are very easy to work with and have amazing capacity-to-weight ratio. The only down side in a long term survival situation is their need to be fed by fancy chargers that suck quite a bit of amperage on their own (unless you want to charge your batteries for 2-4 hours at a time). I'd say its a good everyday, short-med length solution, but certainly not a long term solution unless you have the ability to run a power hungry battery charger every now and then. And if you have that you are probably flying your heli too!! 
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http://www.hobbyking.com/hobbyking/store/__7637__Turnigy_balancer_Charger_2S_3S.html
That charger hooks to a 12v source and charges at 800mah. I know that's slow, but if you are charging your batteries, you probably have shore power. Hook that inline with your PS and you'll be good to go... Or pay a little more and get a charge current of 6A: http://www.hobbyking.com/hobbyking/store/__7028__Turnigy_Accucel_6_50W_6A_Balancer_Charger_w_accessories.html I really think you could wire one of these into your PS (I'm planning on using one that has multiple outputs: http://12voltpowersupplies.us/). I really do think this could work as a weight saver for EmComm boxes... |
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I just keep my gel-cell sealed batteries in battery boxes that hook up via aderson power poles. I can carry them seperately from my 'fly-away' kit. When I deploy, I never know what the generator situation will be, (except for my EU-2000i's), and I need power for stuff other than just a radio...like a laptop, Pactor modem, light, scanner, printer, etc. I needs me some power.  
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