K2 vs. StarkPower LiFePo4 batteries

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

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

....And the chargers are very inexpensive. I have 2 LiFePO4 batteries
and two chargers.

On 4/14/2015 5:44 PM, 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

--
Dan Marotta

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, the voice of reason and logic. I just checked K2 website and nothing posted but a charger is only $40. Seems to be cheap insurance for for $125+ battery.

No an excuse but this is the setup that came with the plane I bought. Buy beware but I should have known that.

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

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

On Tuesday, 14 April 2015 18:41:54 UTC-6, 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

Switching in flight is covered, similar to what you describe. I have the opposite situation; currently 2 batteries but ability to add 2 more (front of stick and in tail) that are wired and plumbed.

Thanks Evan

From the StarkPower website:
"Unlimited packs in parallel at 12V but only with individual 12V chargers on each battery."

http://www.starkpower.com/spnews/energystoragebatt/

On Tuesday, April 14, 2015 at 6:41:54 PM UTC-6, 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

"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.

On Tuesday, April 14, 2015 at 9:16:30 PM UTC-4, Clay wrote:
"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.

You want to use components rated for more than one amp :-), but right idea. I don't have specific recommendations, but troll the Mouser(.com) catalog or equivalent.

Trying to get good data on what these bms boards do is tough (or was, last I looked). But most will source quite a bit of current. DC doesn't switch worth a crap either... interrupting a high current DC load is *really* hard on switch contacts and best avoided.

-Evan / T8