Today's Message Index:
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1. 02:09 PM - Re: Re: EFI current requirements (Robert L. Nuckolls, III)
2. 02:35 PM - Re: EFI current requirements (markfw)
3. 03:23 PM - Re: Re: EFI current requirements (Charlie England)
Message 1
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| Subject: | Re: EFI current requirements |
>The issue of AH ratings has been around as long
>as lithium battery tech. Since the typical duty
>of a battery in a motor vehicle is purely
>starting, the lithium guys have almost always
>used AH 'equivalent' ratings when it comes to
>the battery's ability to *start* an engine.
I don't think there was any misunderstanding about
the ratings. The 'equivalency' thing was about cranking
current . . . period. In the early days, they deliberately
omitted comparisons of battery capacity . . . which made
their marketing numbers for weight and size versus
performance look better. My earliest conversations with
EarthX confirmed this.
>Those of you planning on using EX batteries do
>need to be aware that the internal battery
>management system really is another failure
>point, and has failed in at least one case. If
>it decides that there are external problems, or
>the battery is near end-of-charge (whether its
>assumption is correct or not), it will
>disconnect the battery. Under the right
>conditions, with some, older design alternators,
>the load dump could cause an alternator failure.
>Not likely a risk with B&C alts, but many older
>internally regulated alternators will die in a load dump situation.
"Load dump" is nearly an non-existent phenomenon
and it would not happen due to the actions of
the BMS. Recall that the BMS breaks the output
as the battery is being discharged . . . if you
have a working alternator on line, then the battery
will be charging and the BMS will be happy. It would
never disconnect while a functioning alternator
was doing its job.
>In an 'alternator out' situation, the EX *will*
>disconnect at some point, before the battery is
>fully depleted. Your call on use, but do know
>the failure modes if you use them.
---------------------
>>Just a suggestion about your battery comments....
>>I would think that using the smaller battery to
>>"boost charge" the larger battery might be
>>better than trying to start an engine directly off the smaller.
BATTERIES CANNOT CHARGE BATTERIES.
>>The larger boosted battery has the internal
>>hardware and cabling to handle huge loads like
>>starting sequences.=C2 The smaller battery could
>>bring the larger back to life enough to get a good engine start.....
SORRY, DOESN'T WORK THAT WAY. If the smaller
battery stores enough watt-seconds of snort
to crank the engine, then use it to do just
that. But 'charging' a dead battery from
a 'full' battery doesn't work.
>>On Sun, Dec 29, 2019 at 10:42 AM markfw
>><<mailto:markwheelermd@icloud.com>markwheelermd@icloud.com> wrote:
>>"markfw" <<mailto:markwheelermd@icloud.com>markwheelermd@icloud.com>
>>
>>John,
>>
>>Thanks for the link to the thread of Ross's
>>evaluation of the Shorei battery. This is a
>>good example of non-truth in advertising.
>>
>>However, according to Ross the Shorei weighs
>>2.2 pounds and is good for approximately 6 ah.
>>The EarthX ETX 900 battery is rated by them at 15.6 ah and weighs 4.9
pounds.
>>
>>Since these Lithium battery manufacturers
>>apparently all use the same (or similar)
>>Chinese Lithium cells I would say that EarthX
>>is rating their batteries properly for
>>continuous use rather than just starting.
I got on EarthX a few years back about the 'equivalent'
rating and they started adding contained energy (CAPACITY)
values to their advertising literature.
>>I will be using an EarthX 24 ah single battery
>>in my day-VFR Carbon Cub. I will also have the
>>EarthX 2 ah portable "starter" battery if I
>>forget to turn off my master switch.
You don't have active and insistent LOW VOLTS
warning?
>> It will be interesting to see if it will
>> actually start my engine. It's
>> counterintuitive that such a small battery
>> could start an O-340, but it can supposedly do it.
If you're carrying an 'extra' battery around as
a hedge against failure to use a checklist, perhaps
it would be more elegant to upsize the main battery,
ditch the 'ohmygosh' battery and include some means
for making sure the master doesn't get left on.
A little buzzer on a low oil pressure switch works
good . . . little irritating flashing lights work
too . . .
But adding more batteries for any reason only increases
your battery maintenance time and costs by the same
factor. The elegant solution has ONE battery and
a failure mode analysis that confirms exceedingly
low risk. If you've got an unused vacuum pump pad,
TWO alternators and one battery (perhaps smaller than
a 900) is about as reliable as you can get.
Bob . . .
Message 2
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| Subject: | Re: EFI current requirements |
nuckolls.bob(at)aeroelect wrote:
>
> > The issue of AH ratings has been around as long as lithium battery tech. Since
the typical duty of a battery in a motor vehicle is purely starting, the lithium
guys have almost always used AH 'equivalent' ratings when it comes to the
battery's ability to *start* an engine.
>
> I don't think there was any misunderstanding about
> the ratings. The 'equivalency' thing was about cranking
> current . . . period. In the early days, they deliberately
> omitted comparisons of battery capacity . . . which made
> their marketing numbers for weight and size versus
> performance look better. My earliest conversations with
> EarthX confirmed this.
>
>
> > Those of you planning on using EX batteries do need to be aware that the internal
battery management system really is another failure point, and has failed
in at least one case. If it decides that there are external problems, or the
battery is near end-of-charge (whether its assumption is correct or not), it
will disconnect the battery. Under the right conditions, with some, older design
alternators, the load dump could cause an alternator failure. Not likely a
risk with B&C alts, but many older internally regulated alternators will die
in a load dump situation.
>
> "Load dump" is nearly an non-existent phenomenon
> and it would not happen due to the actions of
> the BMS. Recall that the BMS breaks the output
> as the battery is being discharged . . . if you
> have a working alternator on line, then the battery
> will be charging and the BMS will be happy. It would
> never disconnect while a functioning alternator
> was doing its job.
>
>
>
> > In an 'alternator out' situation, the EX *will* disconnect at some point, before
the battery is fully depleted. Your call on use, but do know the failure
modes if you use them.
> >
>
> ---------------------
>
>
> >
> > > Just a suggestion about your battery comments....
> > > I would think that using the smaller battery to "boost charge" the larger
battery might be better than trying to start an engine directly off the smaller.
> > >
> >
>
> BATTERIES CANNOT CHARGE BATTERIES.
>
>
> >
> > > The larger boosted battery has the internal hardware and cabling to handle
huge loads like starting sequences. The smaller battery could bring the larger
back to life enough to get a good engine start.....
> >
>
> SORRY, DOESN'T WORK THAT WAY. If the smaller
> battery stores enough watt-seconds of snort
> to crank the engine, then use it to do just
> that. But 'charging' a dead battery from
> a 'full' battery doesn't work.
>
>
>
> >
> > > On Sun, Dec 29, 2019 at 10:42 AM markfw wrote:
> > >
> > > John,
> > >
> > > Thanks for the link to the thread of Ross's evaluation of the Shorei battery.
This is a good example of non-truth in advertising.
> > >
> > > However, according to Ross the Shorei weighs 2.2 pounds and is good for
approximately 6 ah. The EarthX ETX 900 battery is rated by them at 15.6 ah and
weighs 4.9 pounds.
> > >
> > > Since these Lithium battery manufacturers apparently all use the same (or
similar) Chinese Lithium cells I would say that EarthX is rating their batteries
properly for continuous use rather than just starting.
> >
>
> I got on EarthX a few years back about the 'equivalent'
> rating and they started adding contained energy (CAPACITY)
> values to their advertising literature.
>
>
> >
> > > I will be using an EarthX 24 ah single battery in my day-VFR Carbon Cub.
I will also have the EarthX 2 ah portable "starter" battery if I forget to turn
off my master switch.
> >
>
> You don't have active and insistent LOW VOLTS
> warning?
>
>
> >
> > > It will be interesting to see if it will actually start my engine. It's
counterintuitive that such a small battery could start an O-340, but it can
supposedly do it.
> > >
> >
>
> If you're carrying an 'extra' battery around as
> a hedge against failure to use a checklist, perhaps
> it would be more elegant to upsize the main battery,
> ditch the 'ohmygosh' battery and include some means
> for making sure the master doesn't get left on.
>
> A little buzzer on a low oil pressure switch works
> good . . . little irritating flashing lights work
> too . . .
>
> But adding more batteries for any reason only increases
> your battery maintenance time and costs by the same
> factor. The elegant solution has ONE battery and
> a failure mode analysis that confirms exceedingly
> low risk. If you've got an unused vacuum pump pad,
> TWO alternators and one battery (perhaps smaller than
> a 900) is about as reliable as you can get.
>
>
> Bob . . .
Bob,
I DO have both audio and visual (thanks to you) warnings of low voltage.
But for the "forgot the master switch" problem I think you are right. It would
be simpler (and save weight) to have an audio warning, like in a car. Since my
EFIS will still be on after I turn off the engine I will investigate having it
make some kind of cabin-audible noise based on low oil pressure, since I would
have my headset off when I was leaving the airplane.
Mark
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494159#494159
Message 3
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| Subject: | Re: EFI current requirements |
On Fri, Jan 3, 2020 at 4:15 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> The issue of AH ratings has been around as long as lithium battery tech.
> Since the typical duty of a battery in a motor vehicle is purely starting,
> the lithium guys have almost always used AH 'equivalent' ratings when it
> comes to the battery's ability to *start* an engine.
>
>
> I don't think there was any misunderstanding about
> the ratings. The 'equivalency' thing was about cranking
> current . . . period. In the early days, they deliberately
> omitted comparisons of battery capacity . . . which made
> their marketing numbers for weight and size versus
> performance look better. My earliest conversations with
> EarthX confirmed this.
>
> Those of you planning on using EX batteries do need to be aware that the
> internal battery management system really is another failure point, and has
> failed in at least one case. If it decides that there are external
> problems, or the battery is near end-of-charge (whether its assumption is
> correct or not), it will disconnect the battery. Under the right
> conditions, with some, older design alternators, the load dump could cause
> an alternator failure. Not likely a risk with B&C alts, but many older
> internally regulated alternators will die in a load dump situation.
>
>
> "Load dump" is nearly an non-existent phenomenon
> and it would not happen due to the actions of
> the BMS. Recall that the BMS breaks the output
> as the battery is being discharged . . . if you
> have a working alternator on line, then the battery
> will be charging and the BMS will be happy. It would
> never disconnect while a functioning alternator
> was doing its job.
>
>
> In an 'alternator out' situation, the EX *will* disconnect at some point,
> before the battery is fully depleted. Your call on use, but do know the
> failure modes if you use them.
>
> [large snip]
>
> Bob . . .
>
There may be no misunderstanding among the engineers at the lithium battery
companies, but respectfully, there has *always* been a misunderstanding
among a great many *aviators* about actual capacity of commercially offered
lithium tech vs SLA and/or wet cell lead acid. You seem to reinforce my
point with,
"In the early days, they deliberately
omitted comparisons of battery capacity . . . which made
their marketing numbers for weight and size versus
performance look better. My earliest conversations with
EarthX confirmed this."
The recently referenced thread on the Vans Air Force forum proves that
it's still the case. The original poster of that thread has been building
electronic ignition and electronic injection systems for aircraft for at
least a couple of decades, and he stumbled upon the knowledge while doing
periodic load testing (that he obviously didn't do before putting the
lithium tech battery of choice into service). This was not an EarthX
aviation battery; it was one of the offerings from a motorsports company.
To their credit, EarthX seems to have modified their aviation offerings
and increased the cell size (count?) so that total energy does compare with
the various SLAs they are marketing against. It did take some rather
pointed, public comments on aviation forums for that to happen.
On the 'load dump' issue: The BMS in the EarthX (according to EX's own
literature, and their rep who posts frequently on VAF) will disconnect the
battery under what it considers an overvoltage charge condition, and IIRC,
also when it thinks the battery is in danger of being excessively depleted,
or too high a current demand is being placed on it. The very fact that the
BMS *can* disconnect the battery (for whatever reason), should, it seems to
me, require us to include that fact in failure mode analysis. If the BMS
itself fails in a fashion that disconnects the battery, that's a new and
different failure mode (which may come as a complete shock if one hasn't
done his homework). If the BMS gets confused and thinks the alternator is
in an OV condition, it may disconnect from the electrical system> load
dump>potential alternator failure>dark airplane.
People like me that have some electronics skill can set up an IR alt with
OV protection for less than 1/2 the cost of just a B&C regulator. A lot of
us are still running internally regulated alternators, many of which likely
still have 'prehistoric' regulators that are not immune to load dump issues
because they are sourced from cars built back in the 1970s/1980s. While
load dumps might not be an every day occurrence, they do happen. Many years
ago, I killed an alternator with an ill-advised switch flip, so I know it
can happen. An EarthX battery mixed with one of those old school IR
alternators does up the odds of a dark airplane, if failure modes aren't
accounted for.
Charlie
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