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nuckolls.bob(at)aeroelect
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 Posted: Sun Sep 20, 2020 8:49 am Post subject: evolution of lithium technologies |
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I've been studying current options for lithium
cells on the market. Discovered some interesting
things. For example . . . this excerpt from the
engineering data sheet on an 18650 cell cited
as suitable for battery powered tools:
----------------------------
9.0. Safety
9.1 Overcharge test
Test method: To charge with 20A-20V at 25 for 3hr.
Criteria: No fire, and no explosion.
9.2 External short-circuit test
Test method: To short-circuit the standard charged cell (or 50% discharged cell)
by connecting positive and negative terminal by 80mOhm wire for 10min.
Criteria: No fire, and no explosion.
9.3 Reverse charge test
Test method: To charge the standard charged cell with charge current 10A
By 20V for 2.5 hours.
Criteria: No fire, and no explosion.
9.4 Heating test
Test method: To heat up the standard charged cell at heating rate 5 per minute up to
130 and keep the cell in oven for 10 minutes.
Criteria: No fire, and no explosion.
-------------------------------
What insults might these cells endure if
incorporated into a flight system? Any worse
than those cited above? Just thinking . . .
Bob . . .
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ceengland7(at)gmail.com
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| Posted: Mon Sep 21, 2020 8:12 am Post subject: evolution of lithium technologies |
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On Sun, Sep 20, 2020 at 11:56 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: |
I've been studying current options for lithium
cells on the market. Discovered some interesting
things. For example . . . this excerpt from the
engineering data sheet on an 18650 cell cited
as suitable for battery powered tools:
[snippped]
What insults might these cells endure if
incorporated into a flight system? Any worse
than those cited above? Just thinking . . .
Ā Bob . . .
|
That got me thinking (and searching).
A wade into the shallow end of the data pool yields only damp feet when it comes to actual *power* capacity. The highest 'continuous current' rating I could find on 18650 cells is around 30A. That would imply, at 1st glance, at least 10 parallel cells per link in the serial chain. Many were limited to around 2A continuous. I couldn't find any specsĀ on peak current, either on the bigger vendor sites, or on actual mfgr data sheet pdfs. Descriptions of, and differences among, the various chemistries and naming conventions, are all over the map, depending on which interweb 'authority' you choose to accept. Obviously more going on than I can see in the normal data sheets, since there are dozens of functional examples of starting batteries on the market.
I'd certainly be game for rolling my own battery, but picking the right cell seems a task not suited to mere mortals.
Charlie
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ceengland7(at)gmail.com
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| Posted: Sun Sep 27, 2020 6:46 pm Post subject: evolution of lithium technologies |
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On 9/21/2020 11:03 AM, Charlie England wrote:
| Quote: |
On Sun, Sep 20, 2020 at 11:56 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: |
I've been studying current options for lithium
cells on the market. Discovered some interesting
things. For example . . . this excerpt from the
engineering data sheet on an 18650 cell cited
as suitable for battery powered tools:
[snippped]
What insults might these cells endure if
incorporated into a flight system? Any worse
than those cited above? Just thinking . . .
Ā Bob . . .
|
That got me thinking (and searching).
A wade into the shallow end of the data pool yields only damp feet when it comes to actual *power* capacity. The highest 'continuous current' rating I could find on 18650 cells is around 30A. That would imply, at 1st glance, at least 10 parallel cells per link in the serial chain. Many were limited to around 2A continuous. I couldn't find any specsĀ on peak current, either on the bigger vendor sites, or on actual mfgr data sheet pdfs. Descriptions of, and differences among, the various chemistries and naming conventions, are all over the map, depending on which interweb 'authority' you choose to accept. Obviously more going on than I can see in the normal data sheets, since there are dozens of functional examples of starting batteries on the market.
I'd certainly be game for rolling my own battery, but picking the right cell seems a task not suited to mere mortals.
Charlie
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As a followup,
Do LiFePO4 batteries used for starting have altered chemistry or cell size, as compared to the 'deep cycle' versions? What about charging profiles? If not,
https://www.amazon.com/LiFePO4-Battery-Miady-Rechargeable-Maintenance-Free/dp/B07X7MD2JK/ref=sr_1_3?dchild=1&keywords=12V+LiFePO4&qid=1601260110&sr=8-3
Looks interesting as the starting point for the DIY battery idea Bob mentioned earlier. The terminals are obviously inadequate as made, but it would be interesting to see what it looks like inside. If larger terminals could be installed...
 Virus-free. www.avast.com [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2] [/url]
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nuckolls.bob(at)aeroelect
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| Posted: Sun Sep 27, 2020 7:53 pm Post subject: evolution of lithium technologies |
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| Quote: | As a followup,
Do LiFePO4 batteries used for starting have altered chemistry or cell size, as compared to the 'deep cycle' versions? What about charging profiles? |
Probably. The no-iron lithium products
demonstrate performance all over the map.
I suspect there are similar variations on the
LiFe theme
Interesting product. Q&A's seem forthright.
He says it's got a BMS that current limits
so upsizing terminals is not likely to let
it crank engines.
It sold with free returns . . . i've ordered one
to shake out.
Bob . . .
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