K2 vs. StarkPower LiFePo4 batteries

"So the next consideration is switching in flight. Same concerns apply..."

Yikes, I switched from 2 lead acids to 2 LFPs, and I seriously doubt I have low voltage drop diodes in there. Is this like a Schottky Diode? https://www.sparkfun.com/products/10926. I take it the BMS or whatever it's called in the K2s doesn't manage this. Thanks for the heads up Evan.

I have two LiFePO4 batteries and two toggle switches. When it's time to
switch I simply turn on the second switch and turn off the first.
Click, click - it takes about as long to do it as to say, "click,
click". No problems.

On 4/14/2015 6:41 PM, Tango Eight wrote:
On Tuesday, April 14, 2015 at 8:23:29 PM UTC-4, Ron Gleason wrote:
On Tuesday, 14 April 2015 17:44:48 UTC-6, Tango Eight wrote:
On Tuesday, April 14, 2015 at 7:29:58 PM UTC-4, JS wrote:
I have used and charged two 10AH LiFePO4 batteries in parallel sans probleme.
Jim

On Tuesday, April 14, 2015 at 2:48:04 PM UTC-7, Ramy wrote:
Can one charger charge two identical starkpower batteries in parallel?

Ramy
Please take questions of this sort to the manufacturer of *your* batteries. The right answer is going to depend on the details of internal construction. And there are going to be some cautions if not an outright admonishment against this.

LFP batteries have very low internal resistance, so batteries in different states of charge will pass a very large current when connected in parallel until their voltage is equalized. If your batteries are fused as they should be (right on the terminal), you stand a fair chance of blowing fuses if you hook together batteries in reasonably different states of charge.

Here's a *great* time to ignore the "well, it worked for me" replies. It'll work acceptably well right up to when it doesn't.

My $0.02.

Evan Ludeman / T8
Damn you Evan, presenting common sense and logic. I looked on the K2 website and nothing mentioned about charging in parallel. However chargers are $50 buck, cheap insurance.

Not an excuse but this setup came with the plane I acquired. Buyer beware, but I should have checked the setup. yup ordered a second charger today. Thanks Evan.

Ron
No trouble!

So the next consideration is switching in flight. Same concerns apply...

I've never been able to figure out a good way to get a back up battery in my 20, so I have just one big honking 12AH battery. But if I had a dual LFP battery system, I'd use (appropriately rated) low voltage drop diodes to prevent back feeding the low battery with some mongo current during switchover. With my luck, I'd blow the fuse on my good battery....

-Evan / T8

--
Dan Marotta

On Tuesday, April 14, 2015 at 5:48:04 PM UTC-4, Ramy wrote:
On Tuesday, February 3, 2015 at 3:33:38 AM UTC-8, wrote:
We have been selling the Starkpower battery for more than a year now. Started out very cautiously - selling only a few to a few of our steady customers. We have now sold several hundred with no complaints. They really are great and are exactly the same size as the battery they replace.

One caution is you must use the special charger (inexpensive) that shuts off when the battery reaches a fully charged state.

Tom Knauff
Knauff & Grove, Inc
Ridge Soaring Gliderport

www.eglider.org

Can one charger charge two identical starkpower batteries in parallel?

Ramy

You can, not really recommended. Typical in charging ANY batteries in parallel.

On Tuesday, 14 April 2015 15:48:04 UTC-6, Ramy wrote:
On Tuesday, February 3, 2015 at 3:33:38 AM UTC-8, wrote:
We have been selling the Starkpower battery for more than a year now. Started out very cautiously - selling only a few to a few of our steady customers. We have now sold several hundred with no complaints. They really are great and are exactly the same size as the battery they replace.

One caution is you must use the special charger (inexpensive) that shuts off when the battery reaches a fully charged state.

Tom Knauff
Knauff & Grove, Inc
Ridge Soaring Gliderport

www.eglider.org

Can one charger charge two identical starkpower batteries in parallel?

Ramy

Works for me with 2 K2 batteries. I sent you a picture