Today's Message Index:
----------------------
1. 06:05 AM - Re: Battery BMS failures? (Robert L. Nuckolls, III)
2. 08:37 AM - Re: Re: Battery BMS failures? (Robert L. Nuckolls, III)
3. 09:52 AM - Re: Re: Battery BMS failures? (Eric Page)
4. 10:30 AM - Re: Re: Battery BMS failures? (C&K)
5. 04:58 PM - Re: Re: Battery BMS failures? (Eric Page)
6. 11:13 PM - Re: Re: Battery BMS failures? (James kale)
Message 1
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| Subject: | Re: Battery BMS failures? |
> So the agile BMS watches temperatures
> and strives to limit those effects
> on the cells irrespective of system
> demands from the outside.
Oh yeah, forgot to include charge balancing.
Unlike most battery chemistries, individual
cells in a series string of lithium may
become 'unbalanced'. This simply means that
one or more cells may 'top off' sooner than
the rest. If the charging continues until
all cells are topped off, there is risk
for over-charging the fast learners thus
insulting their sensibilities.
This is generally accomplished by placing
a load resistor across the faster cells
thus forcing more charge energy into the
slow cells until everyone is in lock-step . . .
consider a cell balancer to be the
ISO9000 of the lithium battery community.
Here's an article from Battery University
on the topic . . .
https://tinyurl.com/y3egekew
. . . yesterday's missive was intended to
illustrate that the term "BMS" is un-defined
in the consumer world and maybe not well
defined in the engineering world either. Unless you
have access to the designer's product performance
specification, it's wise to investigate
before you plunk down your beer money
for a battery upgrade. The full constellation
of products offered are NOT interchangeable
nor are they necessarily plug-n-play into
our legacy electrical systems.
In light of this fact, the phrase "BMS
failure" in any dark-n-stormy-night
story is not very informative unless
the narrator offers specific failure
analysis data . . . almost NEVER a
component of such stories.
Bob . . .
Message 2
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| Subject: | Re: Battery BMS failures? |
>
>Indeed, the deHavilland DHC-8-202 that I flew in
>a previous life was fitted with battery
>temperature gauges on the overhead panel (just
>below the left fire t-handle in the linked image).
>
>https://bitly.com/2uj9V9F+
>
>The airline I worked for operated them in the
>desert southwest, where ambient temps routinely
>exceed 100=C2=B0F. Given the short-hop, quick-turn
>nature of the flying we did, and the
>eye-watering current required to start
>a >2,000shp engine, we kept a close eye on those gauges.
>
>Eric
Did you ever have occasion to take
a hot battery off line?
Bob . . .
Message 3
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| Subject: | Re: Battery BMS failures? |
> On Mar 21, 2019, at 08:36, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com>
wrote:
>
> Did you ever have occasion to take a hot battery off line?
Just once, but not in flight. After flying three Phoenix-Yuma-Phoenix round trips
on an especially brutal July day, we exceeded limits and couldnt start up
for the fourth scheduled Yuma turn. I cant say that either of us was particularly
bothered by the forced break!
Eric
Message 4
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| Subject: | Re: Battery BMS failures? |
On 21/03/2019 11:36 AM, Robert L. Nuckolls, III wrote:
>>
>> Indeed, the deHavilland DHC-8-202 that I flew in a previous life was
>> fitted with battery temperature gauges on the overhead panel (just
>> below the left fire t-handle in the linked image).
>>
>> https://bitly.com/2uj9V9F <https://bitly.com/2uj9V9F>+
>>
>> The airline I worked for operated them in the desert southwest, where
>> ambient temps routinely exceed 100F. Given the short-hop,
>> quick-turn nature of the flying we did, and the eye-watering current
>> required to start a >2,000shp engine, we kept a close eye on those
>> gauges.
>>
>> Eric
>
> Did you ever have occasion to take
> a hot battery off line?
>
>
> Bob . . .
>
An aircraft of that size and vintage may have had a battery charger that
monitored temperature and could limit charging current??
It seems like the Lithium "BMS" strategies are moving in that direction.
Limiting the alternator size as per Earth-X recommendations is a small
step in that direction which I applaud. Even with VRLA batteries I
tossed my 100+ amp alternator in favor of a 40 amp unit.
Ken
Message 5
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| Subject: | Re: Battery BMS failures? |
> On Mar 21, 2019, at 10:28, C&K <yellowduckduo@gmail.com> wrote:
> An aircraft of that size and vintage may have had a battery charger that monitored
temperature and could limit charging current??
Dont quote me on this (its been awhile...) but as I recall, the temperature monitoring
was separate from the charger. I think the chargers only data inputs
were weight-on-wheels and where its AC Power was coming from (external or engine-driven
generator).
Eric
Message 6
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| Subject: | Re: Battery BMS failures? |
I was a 28 year Army Active Duty helicopter pilot. In the mid 70's I had a
Nicad helicopter battery completely melt down. Just molton liquid in the
steel box container. Fortunately the hydrogen did not ignite. We smelled
it and then noticed a terrifically high charge rate. We landed the CH-47
helicopter and we opened the battery box to find the mess. A few years
later the Army put a warning in the manual to land if you smelled the rotten
egg smell and get out of the helicopter get away from it and not to touch
the battery. Finally in the 90s the manufacturer put a battery charger in
the circuit which limited the charge current to about 10 amps. It
prevented thermal runaway charging which could happen with the battery just
tied to the main bus and a 200 amp generator attached to the bus.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
<owner-aeroelectric-list-server@matronics.com> On Behalf Of C&K
Sent: Thursday, March 21, 2019 12:28 PM
Subject: Re: AeroElectric-List: Re: Battery BMS failures?
On 21/03/2019 11:36 AM, Robert L. Nuckolls, III wrote:
>>
>> Indeed, the deHavilland DHC-8-202 that I flew in a previous life was
>> fitted with battery temperature gauges on the overhead panel (just
>> below the left fire t-handle in the linked image).
>>
>> https://bitly.com/2uj9V9F <https://bitly.com/2uj9V9F>+
>>
>> The airline I worked for operated them in the desert southwest, where
>> ambient temps routinely exceed 100F. Given the short-hop,
>> quick-turn nature of the flying we did, and the eye-watering current
>> required to start a >2,000shp engine, we kept a close eye on those
>> gauges.
>>
>> Eric
>
> Did you ever have occasion to take
> a hot battery off line?
>
>
> Bob . . .
>
An aircraft of that size and vintage may have had a battery charger that
monitored temperature and could limit charging current??
It seems like the Lithium "BMS" strategies are moving in that direction.
Limiting the alternator size as per Earth-X recommendations is a small step
in that direction which I applaud. Even with VRLA batteries I tossed my
100+ amp alternator in favor of a 40 amp unit.
Ken
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