### Author Topic: Lipo power to weight ratio.  (Read 4091 times)

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#### SMdude

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##### Lipo power to weight ratio.
« on: July 08, 2017, 01:10:06 am »
Hi Guys,

Just wondering if anyone has some general power to weight ratio for lipo packs?

For my 7.4v packs I get about 28ma/gram.

Reason I am asking is I have just taken delivery of some packs and they are smaller than my last packs and lighter.

And on a third note, does anyone have a battery manufacturer for custom lipo packs they have used and trust that they would like to share via pm?
I'm feeling like I might have been a little done over here...

Cheers

#### HackedFridgeMagnet

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##### Re: Lipo power to weight ratio.
« Reply #1 on: July 10, 2017, 12:37:08 pm »
Specification
That sounds about right if this battery is anything to go by.

I assume you are talking about Energy/Mass or Wh/gram. Apparently it is called specific density, whereas Energy Density is measured as Wh/L

Because u say power/weight but measure in Current/Mass. So  careful with your units.
Quote
Votage: 3.7v
Capacity?1000mA
Continuous Discharge Rating: 1C
Maximum Discharge Rating: 1C
Connector: PH2.0 JST connector
Cable Length: Approx. 70mm
Size: 58x35x5mm
Weight: 22g

(random internet battery.)
Energy/Mass = V * Ah/kg = 3.7 * 1/ 0.022 = 168 Wh/kg

Energy/Mass = V * Ah/kg = 7.4 * 28 = 207 Wh/kg

Maybe the series cell arrangement is confusing you. This will give the same Wh/kg, a higher voltage but less Ah/kg

#### SMdude

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##### Re: Lipo power to weight ratio.
« Reply #2 on: July 10, 2017, 01:23:38 pm »
Thanks!

Yeah, my power to weight is really just a quick check of mAh/weight.
It seems there has been a booboo! I have run these new packs through several cycles and they are consistently 1Ah less capacity than my 40g heavier 3 years old(in storage) packs

So far no response from the seller/manufacturer, though only emailed a few hours ago as I had to do a lot of testing to make sure my battle was a worthy one!

Lol, and it was the one pack I could not compromise on

Thankfully, I can make use of them.

#### Nusa

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##### Re: Lipo power to weight ratio.
« Reply #3 on: July 10, 2017, 02:32:31 pm »
In the end it's not whether they're better or worse than your previous packs.
It's whether they meet the specification the manufacturer promised to deliver.

#### SMdude

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##### Re: Lipo power to weight ratio.
« Reply #4 on: July 10, 2017, 10:23:53 pm »
And the answer to that is a big fat NO.
But being on an entirely different continent, I am not holding my breath that it will get sorted out.
All I can do is work out a way to use/unload them and get more from a different supplier that are built to spec.

#### Audioguru

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##### Re: Lipo power to weight ratio.
« Reply #5 on: July 18, 2017, 05:53:50 pm »
I order excellent North American batteries from the manufacturer when they have free shipping or from my local hobby store. I don't buy cheap fake Chinese stuff from ebay.

#### SMdude

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##### Re: Lipo power to weight ratio.
« Reply #6 on: July 19, 2017, 09:41:22 am »
I don't buy cheap lipos off ebay either!

No, this is just a stuff up that I am most likely just stuck with now. The quality of what they are is good, just not quite what I wanted.
I have a new product 2/3rd designed to utilise them, I see this as a quicker way out as I am sure I could argue for months and probably get nowhere anyway

Anyway, they sure as hell know now what I wanted and want in the future.

Smf