kubark42
1 W
- Joined
- May 15, 2020
- Messages
- 59
I'm converting an AC-5M to electric, and I've been struggling for a while now to figure out how I want to do my battery pack. I keep coming back to LiPo as the right solution. When I look at the existing eGlider solutions, I've come to realize that they have unnecessarily large packs because they need the amps. So the packs wind up costing more, and worse, weighing significantly more. Weight is the enemy in aviation, it makes you come down faster, sooner, and harder.
The mission profile for a self-launching glider is very different from an ePlane. In the latter case, you need hours of motor time, but in an eGlider you need 3-5 minutes to climb high enough to connect with a nearby thermal. 3-5 minutes pack life sounds much more like an R/C hotliner than it does an EV.
Over the last decade, the R/C world has really gotten a good handle on 15C-20C batteries. There's extensive test data and suppliers are easy to come by. Companies have been around long enough to establish reputations and the products are mature. Fires aren't a thing of the past-- there will always be mistakes and foolish behavior-- but buying good quality packs and chargers it seems to overwhelmingly mitigate the fire risk.
The price and weight for a LiPo pack which can launch the AC-5M to 300m (~1000') is $500 and 3kg. The same pack in LiPo is going to be $3-4k and 12-15kg. The Li-ion pack will be good for another 50 minutes of cruise flight, but that's not the standard mission profile and so that extra battery time is typically unused dead weight.
Safety is a concern, but the 3kg lithium fire is a lot easier to manage than the 15kg one. Furthermore, from an operational standpoint a 3kg pack is one people won't hesitate to remove from the airplane for charging, whereas a 15kg one might lead people to be lazy and charge the battery in situ.
So there are some strong reasons to use LiPo over Li-ion. However, using LiPo is bucking the industry trend, and I hate to reinvent wheels if it's not required.
Am I missing something important here?
The mission profile for a self-launching glider is very different from an ePlane. In the latter case, you need hours of motor time, but in an eGlider you need 3-5 minutes to climb high enough to connect with a nearby thermal. 3-5 minutes pack life sounds much more like an R/C hotliner than it does an EV.
Over the last decade, the R/C world has really gotten a good handle on 15C-20C batteries. There's extensive test data and suppliers are easy to come by. Companies have been around long enough to establish reputations and the products are mature. Fires aren't a thing of the past-- there will always be mistakes and foolish behavior-- but buying good quality packs and chargers it seems to overwhelmingly mitigate the fire risk.
The price and weight for a LiPo pack which can launch the AC-5M to 300m (~1000') is $500 and 3kg. The same pack in LiPo is going to be $3-4k and 12-15kg. The Li-ion pack will be good for another 50 minutes of cruise flight, but that's not the standard mission profile and so that extra battery time is typically unused dead weight.
Safety is a concern, but the 3kg lithium fire is a lot easier to manage than the 15kg one. Furthermore, from an operational standpoint a 3kg pack is one people won't hesitate to remove from the airplane for charging, whereas a 15kg one might lead people to be lazy and charge the battery in situ.
So there are some strong reasons to use LiPo over Li-ion. However, using LiPo is bucking the industry trend, and I hate to reinvent wheels if it's not required.
Am I missing something important here?