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nuckolls.bob(at)aeroelect
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 Posted: Sun Aug 09, 2020 7:16 pm Post subject: Revmaster engine with EarthX battery |
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At 09:15 PM 8/9/2020, you wrote:
| Quote: | | But lithium batteries prefer to be stored at less than a full charge, so in that regard not filling them up is a plus. Why not use the diode and use whatever size battery provides required capacity? Battery will be happy, generator will be happy, and weight will be controlled. |
Apples and grapefruit . . .
Airplanes are not battery storage facilities . . .
Legacy design rules call for:
(1) battery to start engines and
(2) operate most useful electro-whizzies after
alternator failure in accordance with design
rules for endurance.
Look at the charge volts vs. capacity curves
again . . . dropping the bus to 13.4 (3.35 volts
per cell) or even 13.0 (3.25 volts per cell)
leaves you with a battery that is essentially
useless for (2) above.
The endurance bus grew out of a concern for
PLANNING and MAINTAINING alternator-out
performance. I've had readers craft airplanes
that capable of running out a full
tank of fuel during battery-only ops.
For years the FAA had a number pulled
from some dark place calling for 30 minutes
minimum endurance in battery-only ops . . .
Every try to get down from 41,000 feet
in a Beechjet in less than 30 minutes?
I can personally attest to the agonies
of meeting even the 30 minute rule without
adding 25 more pounds of lead to the airplane.
The point is that we need to keep a grip
on the fundamentals of our craft. All
engineering stands on the three-legged
stool of properties of materials, management
of energy, refinement of processes.
The folks at Revmaster are having problems
with their obviously tippy engineering stool.
Elegant system integration is refinement
of process to meet (1) and (2) above.
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Sun Aug 09, 2020 7:43 pm Post subject: Revmaster engine with EarthX battery |
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| Quote: |
What about active current management? More complicated from a total parts count, but might be dirt simple to implement, for less than $20. Something like:
current limited supply |
Man, if you don't scan the offerings every
week in that venue, you'll miss some new
gizmo! Thanks for the heads-up.
Your find reminds me of a bench study I
did on similarly 'upgraded' rectifier/
regulator philosophy for pm alternators
a couple years ago. Didn't find any
really attractive options . . . then.
But the item you've cited suggests a
further look is called for. It's getting
late . . . I'll sleep on it and do some
'asphalt engineering' on it tomorrow.
Need to drive into Wichita for remodeling
materials.
Re: my post of a few minutes ago.
I've got a stable of flashlights and tools
that use LiFePO4, 18650 cells. The chargers
for ALL of these cells tops off at 4.2 volts.
This doesn't seem to put the cell in any
manner of overcharge stress. The charging
currents fall to 1 milliamp or below at 4.2
volts.
I've got EarthX and AeroVoltz batteries on
the bench now that have been getting characterized.
Based on what's been gathered so far, both products
do indeed get your engine started . . . but when
charged at 14.2-14.4 volts, their discharge curves
look very similar to the plots I've been
getting on energy-starved, individual cells.
I'm thinking that BOTH products have untapped
chemical potential that is not available for
operating an airplane during alternator out
conditions. I think this shines a spot-light
on early lithium marketing claims for "lead
acid equivalency" and "engine starting battery".
Both terms sort of hat-dance around the capacity
issues forsaken in a quest for the holy-grail
of lighter weights.
To acquire the SAME capacity as a PC680 by
replacing it with THREE or FOUR AeroVoltz
AVAI-270 or TWO EarthX ETX36D.
Not a problem if your design goals for alternator
out endurance are approaching zero.
Bob . . .
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user9253
Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan
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| Posted: Mon Aug 10, 2020 4:31 am Post subject: Re: Revmaster engine with EarthX battery |
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Whether the victim is the battery or the generator, the object is to reduce the
current. A diode will do that. If a regular diode limits the current too much,
perhaps a Schottky will work. It will not hurt to experiment. Once the battery has been
recharged to a certain level, a relay could be automatically energized to short out the diode.
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Joe Gores |
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon Aug 10, 2020 5:12 am Post subject: Revmaster engine with EarthX battery |
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At 07:31 AM 8/10/2020, you wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>
Whether the victim is the battery or the generator, the object is to reduce the
current. A diode will do that. If a regular diode limits the current too much,
perhaps a Schottky will work. It will not hurt to experiment. Once the battery has been
recharged to a certain level, a relay could be automatically energized to short out the diode. |
But we've established that the battery is
already in an energy-starved state for
charging posed by the LiFePO4 chemistry.
While 'reducing' the current may indeed
fix the burning alternator problem, it
will also reduce the already suppressed
energy content of the battery.
In all fairness, if design goals for this
installation are simply to get the engine
started . . . then perhaps an experiment
to add the suggested diode is worth
exploring. But if there are ANY goals for
battery only endurance, then adding the
diode will be counter-productive in an already
precariously compromised condition.
Discussions in other threads are suggesting mods
to the charging system to make it more robust.
Assuming time and costs are attractive,
improving robustness is never a bad thing.
Further, it may well go toward
RAISING the bus voltage to a more common
14.2 to 14.4 range thus greatly increasing
stored energy in the battery . . . a win-win,
no?
I've expanded the annotation on the charge volts
vs. energy stored plots I posted previously. These
further emphasize that when operated 'per
manufacturer's recommendations', the battery
will contain perhaps 25% of it's potential
storage for the LiFePO4 chemistry.
If anyone has information to the contrary, I'd
be pleased to know it! I'd really like to be
wrong about this . . .
Bob . . .
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echristley(at)att.net
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| Posted: Mon Aug 10, 2020 5:54 am Post subject: Revmaster engine with EarthX battery |
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I'm using a Scorpion LiFePO battery, and due to some carb tuning issues, have had the chance to drain it a few times. It never seem to have a large reserve capacity. The regulator for my 20A John Deere regulator was set to 13.2V, so this makes sense.
I'm switching to Bill Clapps generator design, that uses a Harley-Davidson 32A generator, and the regulator is advertised at 14.7V. This email chain has me wondering if I should look for a regulator that goes to 16V, but Scorpion advertises that the max should be 15.0V on their website. Maybe Scorpion is just being overly conservative due to the LiFePO's sensitivity to overcharge?
SSTZ14S-FP Scorpion Stinger 12v 387 CCA LiFePo4 Extreme High Output Battery
<![endif]--><![endif]-->
<![endif]-->SSTZ14S-FP Scorpion Stinger 12v 387 CCA LiFePo4 Extreme High Output Battery
Lithium Batteries are discharged to 30% of capacity for shipping requirements. When you receive the battery it w...
On Sunday, August 9, 2020, 11:44:03 PM EDT, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
| Quote: |
What about active current management? More complicated from a total parts count, but might be dirt simple to implement, for less than $20. Something like:
current limited supply |
Man, if you don't scan the offerings every
week in that venue, you'll miss some new
gizmo! Thanks for the heads-up.
Your find reminds me of a bench study I
did on similarly 'upgraded' rectifier/
regulator philosophy for pm alternators
a couple years ago. Didn't find any
really attractive options . . . then.
But the item you've cited suggests a
further look is called for. It's getting
late . . . I'll sleep on it and do some
'asphalt engineering' on it tomorrow.
Need to drive into Wichita for remodeling
materials.
Re: my post of a few minutes ago.
I've got a stable of flashlights and tools
that use LiFePO4, 18650 cells. The chargers
for ALL of these cells tops off at 4.2 volts.
This doesn't seem to put the cell in any
manner of overcharge stress. The charging
currents fall to 1 milliamp or below at 4.2
volts.
I've got EarthX and AeroVoltz batteries on
the bench now that have been getting characterized.
Based on what's been gathered so far, both products
do indeed get your engine started . . . but when
charged at 14.2-14.4 volts, their discharge curves
look very similar to the plots I've been
getting on energy-starved, individual cells.
I'm thinking that BOTH products have untapped
chemical potential that is not available for
operating an airplane during alternator out
conditions. I think this shines a spot-light
on early lithium marketing claims for "lead
acid equivalency" and "engine starting battery".
Both terms sort of hat-dance around the capacity
issues forsaken in a quest for the holy-grail
of lighter weights.
To acquire the SAME capacity as a PC680 by
replacing it with THREE or FOUR AeroVoltz
AVAI-270 or TWO EarthX ETX36D.
Not a problem if your design goals for alternator
out endurance are approaching zero.
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon Aug 10, 2020 9:34 am Post subject: Revmaster engine with EarthX battery |
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At 08:53 AM 8/10/2020, you wrote:
| Quote: | I'm using a Scorpion LiFePO battery, and due to some carb tuning issues, have had the chance to drain it a few times. It never seem to have a large reserve capacity. The regulator for my 20A John Deere regulator was set to 13.2V, so this makes sense.
I'm switching to Bill Clapps generator design, that uses a Harley-Davidson 32A generator, and the regulator is advertised at 14.7V. This email chain has me wondering if I should look for a regulator that goes to 16V, but Scorpion advertises that the max should be 15.0V on their website. |
Nope. Most suppliers cite the same number knowing
full well that contemporary systems would never
be purposefully adjusted so high. In fact, charging
plots I'm gathering suggest that charging voltages
at the upper end of recommended range DO NOT increase
stored energy.
Your legacy regulator adjusted 14.2 to 14.4 will
be just fine.
| Quote: | Maybe Scorpion is just being overly conservative due to the LiFePO's sensitivity to overcharge?
SSTZ14S-FP Scorpion Stinger 12v 387 CCA LiFePo4 Extreme High Output Battery
|
I presume that this battery is fitted with some form
of battery management system. Unfortunately, there is
no obvious consensus as to what constitutes the
optimum BMS nor are there published numbers as to
how they are set up.
In general, a BMS will manage one or more
of the following aspects of battery
operations:
Disconnect when overloaded
Disconnect when over charged (I guessing that
the 'unhook' happens at around 14 volts)
Disconnect when over dis-charged
Disconnect on over temperature
Cell balancing for recharge of a
deeply discharged battery -OR-
overcharge prevention for a
degraded cell.
Note that the BMS can only UNHOOK
a battery from the rest of the ship's
electrical system. It cannot boost
the effective charging potential for
enhancing energy stored.
So when the battery manufacturer speaks
to recommended bus voltage, the voltage
impressed on each layer of cells is
1/4th that value.
Going back to the plots I've gathered
in weeks past, the legacy bus voltages
for lead-acid based DC power systems
will be incapable of charging a LiFePO4
cell to its chemically limited energy
potential.
Unlike popular products in the OBAM aviation
market, lithium batteries for TC aircraft
are designed, tested, qualified and
maintained to exceedingly detailed
requirements. See:
https://tinyurl.com/y49tvwlz
Unlike our friends in the OBAM aviation
lithium market, the TC suppliers prominently
cite Ampere Hour ratings of their products.
This is because their target market is
FORM, FIT AND FUNCTION replacement for
legacy lead or nicad products. Therefore,
even tho they can start an engine with
a lighter/smaller battery, they are
required to keep stuffing cells into the
package until capacity requirements are met.
This makes for a SUPER cranking battery!
I'll have some more data plots to share
later today. I had to postpone my expedition
to Wichita.
Bob . . .
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echristley(at)att.net
Guest
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| Posted: Mon Aug 10, 2020 1:00 pm Post subject: Revmaster engine with EarthX battery |
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OK. I'm missing something major here. Earlier you stated:
Take a peek at the capacity vs. charge voltage
plots. A 3.6 volt charge (14.4v bus) would
charge an LiFePO4 to about 25% of its
potential chemical potential capacity.
The chart you shared showed it clearly. To get to the 100% capacity on the charging plots you shared, I'd need to run a bus voltage of 16.8V (4.2V/cell).
Below, you're saying that 14.4V will be fine. I'm thinking, "How could 25% of capacity be 'fine'?" I've obviously lost the plot somewhere in here.
BTW, I killed one of these by putting it right above the exhaust with no protection. Don't do that. It's expensive.
However, due to that slight misfortune, I am able to confirm that it is made of 12 "bags", wired so that current flows through 4 groups, with each group having three bags. The external connectors are attached directly to each end of the string, with what I'm eyeballing to be 10 or 12AWG wire. The only electronics in the case is a small circuit board that allows for a rudimentary check of the batteries charge.
On Monday, August 10, 2020, 1:38:06 PM EDT, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
At 08:53 AM 8/10/2020, you wrote:
| Quote: | I'm using a Scorpion LiFePO battery, and due to some carb tuning issues, have had the chance to drain it a few times. It never seem to have a large reserve capacity. The regulator for my 20A John Deere regulator was set to 13.2V, so this makes sense.
I'm switching to Bill Clapps generator design, that uses a Harley-Davidson 32A generator, and the regulator is advertised at 14.7V. This email chain has me wondering if I should look for a regulator that goes to 16V, but Scorpion advertises that the max should be 15.0V on their website. |
Nope. Most suppliers cite the same number knowing
full well that contemporary systems would never
be purposefully adjusted so high. In fact, charging
plots I'm gathering suggest that charging voltages
at the upper end of recommended range DO NOT increase
stored energy.
Your legacy regulator adjusted 14.2 to 14.4 will
be just fine.
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kenryan
Joined: 20 Oct 2009
Posts: 424
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| Posted: Mon Aug 10, 2020 1:24 pm Post subject: Revmaster engine with EarthX battery |
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Ditto what Ernest says. I too am lost. Seems like on the one hand 14.x volts is just fine and on the other hand 14.x volts is terrible and will never charge the battery. Clearly I am missing something important.
On Mon, Aug 10, 2020 at 1:07 PM Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:
| Quote: |
OK. I'm missing something major here. Earlier you stated:
 Take a peek at the capacity vs. charge voltage
  plots. A 3.6 volt charge (14.4v bus) would
  charge an LiFePO4 to about 25% of its
  potential chemical potential capacity.
The chart you shared showed it clearly. To get to the 100% capacity on the charging plots you shared, I'd need to run a bus voltage of 16.8V (4.2V/cell).
Below, you're saying that 14.4V will be fine. I'm thinking, "How could 25% of capacity be 'fine'?" I've obviously lost the plot somewhere in here.
BTW, I killed one of these by putting it right above the exhaust with no protection. Don't do that. It's expensive.Â
However, due to that slight misfortune, I am able to confirm that it is made of 12 "bags", wired so that current flows through 4 groups, with each group having three bags. The external connectors are attached directly to each end of the string, with what I'm eyeballing to be 10 or 12AWG wire. The only electronics in the case is a small circuit board that allows for a rudimentary check of the batteries charge.
On Monday, August 10, 2020, 1:38:06 PM EDT, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
At 08:53 AM 8/10/2020, you wrote:
| Quote: | I'm using a Scorpion LiFePO battery, and due to some carb tuning issues, have had the chance to drain it a few times. It never seem to have a large reserve capacity. The regulator for my 20A John Deere regulator was set to 13.2V, so this makes sense.
I'm switching to Bill Clapps generator design, that uses a Harley-Davidson 32A generator, and the regulator is advertised at 14.7V. This email chain has me wondering if I should look for a regulator that goes to 16V, but Scorpion advertises that the max should be 15.0V on their website. |
 Nope. Most suppliers cite the same number knowing
 full well that contemporary systems would never
 be purposefully adjusted so high. In fact, charging
 plots I'm gathering suggest that charging voltages
 at the upper end of recommended range DO NOT increase
 stored energy.
 Your legacy regulator adjusted 14.2 to 14.4 will
 be just fine.
|
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon Aug 10, 2020 4:54 pm Post subject: Revmaster engine with EarthX battery |
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At 03:57 PM 8/10/2020, you wrote:
| Quote: | OK. I'm missing something major here. Earlier you stated:
Take a peek at the capacity vs. charge voltage
plots. A 3.6 volt charge (14.4v bus) would
charge an LiFePO4 to about 25% of its
potential chemical potential capacity.
The chart you shared showed it clearly. To get to the 100% capacity on the charging plots you shared, I'd need to run a bus voltage of 16.8V (4.2V/cell).
Below, you're saying that 14.4V will be fine. I'm thinking, "How could 25% of capacity be 'fine'?" I've obviously lost the plot somewhere in here. |
Yes, you missed the irony of my observations.
The plots I published so far show the voltage vs.
capacity characteristics of a single, 'barefoot'
cell. These are generally marketed as flashlight/
tool/electronics batteries. Almost without exception,
you cannot achieve the advertised capacity unless
the cell is charged to the maximum, 4.2 volts
rating . . . which translates to a bus equivalent
of 16.8 volts.
Now, vendors like AeroVoltz, EarthX, True Blue,
Shiorai, et. als. will take combinations of
individual cells and package them together
with a battery management system (BMS). The
BMS will implement certain protections as mentioned
in my previous post. One such protection is for
too high a charge voltage such that the device is
compatible with legacy vehicular DC power
systems. i.e. 14.2 volts or thereabouts.
The BMS is a significant piece of electronics.
1/4 to 1/3 the battery's internal volume can
be occupied by transistors and such.
Check out the attached plots on an EarthX
ETX36D battery I've had on hand for a few years.
There are three plots where the battery was charged
at 14.2, 14.4 and 15.0 volts. Note that unlike
the plots on individual cells, these all lay
practically right on top of each other . . . all
three show a battery capacity of 10.2 to 10.6 A.H.
This tells us that the BMS is in control of how
cells in this battery are charged INDEPENDENTLY
of the charging voltage. Stepping up your alternator
output voltage with some hope of exploiting latent
battery capacity would not be fruitful . . . and
possibly harmful to other electro-whizzies in the system.
The data I've gathered so far seems to say that
cells incorporated into batteries for lead-acid
replacement are DE-rated by design of the BMS.
This doesn't mean that the lithium batteries
offered do not deliver to their nameplate ratings . . .
it simply says these batteries contain chemical
capability that cannot be exploited in
a 14 VDC system.
Bob . . .
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echristley(at)att.net
Guest
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| Posted: Tue Aug 11, 2020 4:36 am Post subject: Revmaster engine with EarthX battery |
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Aaah! Now I see the light. AeroVoltz and EarthX take care of making sure that 14.2V is sufficient.
The Scorpion, being as close to raw cells as one can get, has left that task to me. Driving this battery to 16.8V would be useful from the aspect of battery capacity.
Shoot! Just what I needed. Another distraction. Now I have to take the old battery apart to play with the cells. 
On Monday, August 10, 2020, 8:56:53 PM EDT, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
At 03:57 PM 8/10/2020, you wrote:
| Quote: | OK. I'm missing something major here. Earlier you stated:
Take a peek at the capacity vs. charge voltage
plots. A 3.6 volt charge (14.4v bus) would
charge an LiFePO4 to about 25% of its
potential chemical potential capacity.
The chart you shared showed it clearly. To get to the 100% capacity on the charging plots you shared, I'd need to run a bus voltage of 16.8V (4.2V/cell).
Below, you're saying that 14.4V will be fine. I'm thinking, "How could 25% of capacity be 'fine'?" I've obviously lost the plot somewhere in here. |
Yes, you missed the irony of my observations.
The plots I published so far show the voltage vs.
capacity characteristics of a single, 'barefoot'
cell. These are generally marketed as flashlight/
tool/electronics batteries. Almost without exception,
you cannot achieve the advertised capacity unless
the cell is charged to the maximum, 4.2 volts
rating . . . which translates to a bus equivalent
of 16.8 volts.
Now, vendors like AeroVoltz, EarthX, True Blue,
Shiorai, et. als. will take combinations of
individual cells and package them together
with a battery management system (BMS). The
BMS will implement certain protections as mentioned
in my previous post. One such protection is for
too high a charge voltage such that the device is
compatible with legacy vehicular DC power
systems. i.e. 14.2 volts or thereabouts.
The BMS is a significant piece of electronics.
1/4 to 1/3 the battery's internal volume can
be occupied by transistors and such.
Check out the attached plots on an EarthX
ETX36D battery I've had on hand for a few years.
There are three plots where the battery was charged
at 14.2, 14.4 and 15.0 volts. Note that unlike
the plots on individual cells, these all lay
practically right on top of each other . . . all
three show a battery capacity of 10.2 to 10.6 A.H.
This tells us that the BMS is in control of how
cells in this battery are charged INDEPENDENTLY
of the charging voltage. Stepping up your alternator
output voltage with some hope of exploiting latent
battery capacity would not be fruitful . . . and
possibly harmful to other electro-whizzies in the system.
The data I've gathered so far seems to say that
cells incorporated into batteries for lead-acid
replacement are DE-rated by design of the BMS.
This doesn't mean that the lithium batteries
offered do not deliver to their nameplate ratings . . .
it simply says these batteries contain chemical
capability that cannot be exploited in
a 14 VDC system.
Bob . . .
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echristley(at)att.net
Guest
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| Posted: Tue Aug 11, 2020 4:51 am Post subject: Revmaster engine with EarthX battery |
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Unfortunately, that presumption would be wrong. The Scorpion LiFePO has cells soldered directly to the output. But, this gives us an opportunity!! (Excuse me while I make some lemonade.)
Extrapolating from the comments below, the TC manufacturers have to make the battery bigger, because the legacy system can only pump the cells up to 30% of their capacity. If we can move away from the legacy requirements, and not have a BMS shutting the charging down, the physics would suggest that we could easily get double the battery capacity. The HUGE caveat, is that all other systems would have to be tolerant of 16V.
On Monday, August 10, 2020, 1:38:06 PM EDT, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
I presume that this battery is fitted with some form
of battery management system.
. . .
Note that the BMS can only UNHOOK
a battery from the rest of the ship's
electrical system. It cannot boost
the effective charging potential for
enhancing energy stored.
. . .
Therefore,
even tho they can start an engine with
a lighter/smaller battery, they are
required to keep stuffing cells into the
package until capacity requirements are met.
Bob . . .
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ceengland7(at)gmail.com
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| Posted: Tue Aug 11, 2020 5:50 am Post subject: Revmaster engine with EarthX battery |
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Hey Ernest,
See my earlier post.
Charlie
Sent from BlueMail
On Aug 11, 2020, at 8:18 AM, Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote: | Quote: |
Unfortunately, that presumption would be wrong. The Scorpion LiFePO has cells soldered directly to the output. But, this gives us an opportunity!! (Excuse me while I make some lemonade.)
Extrapolating from the comments below, the TC manufacturers have to make the battery bigger, because the legacy system can only pump the cells up to 30% of their capacity. If we can move away from the legacy requirements, and not have a BMS shutting the charging down, the physics would suggest that we could easily get double the battery capacity. The HUGE caveat, is that all other systems would have to be tolerant of 16V.
On Monday, August 10, 2020, 1:38:06 PM EDT, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
I presume that this battery is fitted with some form
of battery management system.
. . .
Note that the BMS can only UNHOOK
a battery from the rest of the ship's
electrical system. It cannot boost
the effective charging potential for
enhancing energy stored.
. . .
Therefore,
even tho they can start an engine with
a lighter/smaller battery, they are
required to keep stuffing cells into the
package until capacity requirements are met.
Bob . . .
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kenryan
Joined: 20 Oct 2009
Posts: 424
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| Posted: Tue Aug 11, 2020 6:08 am Post subject: Revmaster engine with EarthX battery |
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OK. It seems like my "understanding" of battery charging is seriously flawed. I thought, for example, that if a partially discharged battery was connected to a higher voltage source, the battery would be charged to that voltage level. Since the EarthX has a charged, resting voltage of 13.2 - 13.3 volts I thought that if it was connected to a 13.5 volt source, it would eventually charge the battery. Apparently, none of this is true?
On Tue, Aug 11, 2020 at 5:18 AM Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:
| Quote: |
Unfortunately, that presumption would be wrong. The Scorpion LiFePO has cells soldered directly to the output. But, this gives us an opportunity!! (Excuse me while I make some lemonade.)
Extrapolating from the comments below, the TC manufacturers have to make the battery bigger, because the legacy system can only pump the cells up to 30% of their capacity. If we can move away from the legacy requirements, and not have a BMS shutting the charging down, the physics would suggest that we could easily get double the battery capacity. The HUGE caveat, is that all other systems would have to be tolerant of 16V.
On Monday, August 10, 2020, 1:38:06 PM EDT, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
 I presume that this battery is fitted with some form
 of battery management system.
. . .
 Note that the BMS can only UNHOOK
 a battery from the rest of the ship's
 electrical system. It cannot boost
 the effective charging potential for
 enhancing energy stored.
. . .
 Therefore,
 even tho they can start an engine with
 a lighter/smaller battery, they are
 required to keep stuffing cells into the
 package until capacity requirements are met.
 Â
 Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Wed Aug 12, 2020 7:36 am Post subject: Revmaster engine with EarthX battery |
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At 09:05 AM 8/11/2020, you wrote:
| Quote: | | OK. It seems like my "understanding" of battery charging is seriously flawed. I thought, for example, that if a partially discharged battery was connected to a higher voltage source, the battery would be charged to that voltage level. Since the EarthX has a charged, resting voltage of 13.2 - 13.3 volts I thought that if it was connected to a 13.5 volt source, it would eventually charge the battery. Apparently, none of this is true? |
As long as you DON'T put silicon 'smarts' between the
energy source and the battery to be charged.
Those plots I published for stepped increases in
charging voltage on a single LiFePO4 cell speaks
to the phenomenon you've cited. This is generally
true for all the SVLA, Flooded and Gel versions
of the Lead-Acid technology . . . because our
vehicular DC power systems EVOLVED around the
charge/discharge reactions of lead, sulphur, oxygen
and hydrogen. This convention is 160+ years old.
It also works for the new kids on the block that
use lithium, iron, phosphorous and oxygen but with
a big 'gotcha' . . . the differences in voltage
for these two chemistries keep them from being
form/fit/function interchangeable.
Our alternators, regulators, light bulbs, legacy
electronics, etc. etc. were optimized for function
in a 14.2-14.4 volt world that was ESTABLISHED
by the chemistry of the battery-of-choice for
over a century.
But three LiFePO4 cells stacked gives us a charge
(bus voltage) of 12.6V and a discharge (alternator-out)
voltage of about 11.1V. Decidedly incompatible with
the legacy lead-acid world.
Okay, cells stacked gives us a bus voltage of 16.8 and a
14.8V alternator-out voltage. Again . . . not a drop-in
replacement.
Some folks have decided to offer 4-stack batteries
with no 'smarts' and which will be charged to
3.6 volts per layer . . . a potential that does
not charge the chemistry to its latent capabilities . . .
but 'good enough' if the target users are willing
to accept compromised performance in exchange for weight
savings.
Further, it turns out that this very energetic
chemistry comes with some risks. It will produce
extra-ordinary fault currents for it's size.
Prolonged deep discharge can seriously injure
an otherwise good battery. Charging at greater
than legacy lead-acid voltages will indeed
'stuff' more energy into the battery but allowing
or recommending operations above the legacy
levels poses system wide risks that may be
hazardous to hardware. The batteries are at
greater risk for catastrophic failure to
to over-charging or hard-charging.
So, BMS enter stage-right:
A judicious collection of transistors and things
can be hammered into a 'battery management system'
that will pound our square cornered lithium
product into a round, lead-acid hole.
Hence, products like EarthX and AeroVoltz
with BMS system will FUNCTION in the lead-
acid hole with minimized risks but performance
compromises.
'Barefoot' lithium products will also
function in the lead-acid world but safeguards
offered by BMS fitted products are the
user's responsibility.
Bob . . .
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kenryan
Joined: 20 Oct 2009
Posts: 424
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| Posted: Wed Aug 12, 2020 9:08 am Post subject: Revmaster engine with EarthX battery |
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Thanks Bob. That does help clear things up.
On Wed, Aug 12, 2020 at 7:42 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 09:05 AM 8/11/2020, you wrote:
| Quote: | | OK. It seems like my "understanding" of battery charging is seriously flawed. I thought, for example, that if a partially discharged battery was connected to a higher voltage source, the battery would be charged to that voltage level. Since the EarthX has a charged, resting voltage of 13.2 - 13.3 volts I thought that if it was connected to a 13.5 volt source, it would eventually charge the battery. Apparently, none of this is true? |
 As long as you DON'T put silicon 'smarts' between the
 energy source and the battery to be charged.
 Those plots I published for stepped increases in
 charging voltage on a single LiFePO4 cell speaks
 to the phenomenon you've cited. This is generally
 true for all the SVLA, Flooded and Gel versions
 of the Lead-Acid technology . . . because our
 vehicular DC power systems EVOLVED around the
 charge/discharge reactions of lead, sulphur, oxygen
 and hydrogen. This convention is 160+ years old.
 It also works for the new kids on the block that
 use lithium, iron, phosphorous and oxygen but with
 a big 'gotcha' . . . the differences in voltage
 for these two chemistries keep them from being
 form/fit/function interchangeable.
 Our alternators, regulators, light bulbs, legacy
 electronics, etc. etc. were optimized for function
 in a 14.2-14.4 volt world that was ESTABLISHED
 by the chemistry of the battery-of-choice for
 over a century.
 But three LiFePO4 cells stacked gives us a charge
 (bus voltage) of 12.6V and a discharge (alternator-out)
 voltage of about 11.1V. Decidedly incompatible with
 the legacy lead-acid world.
 Okay, cells stacked gives us a bus voltage of 16.8 and a
 14.8V alternator-out voltage. Again . . . not a drop-in
 replacement.
 Some folks have decided to offer 4-stack batteries
 with no 'smarts' and which will be charged to
 3.6 volts per layer . . . a potential that does
 not charge the chemistry to its latent capabilities . . .
 but 'good enough' if the target users are willing
 to accept compromised performance in exchange for weight
 savings.
 Further, it turns out that this very energetic
 chemistry comes with some risks. It will produce
 extra-ordinary fault currents for it's size.
 Prolonged deep discharge can seriously injure
 an otherwise good battery. Charging at greater
 than legacy lead-acid voltages will indeed
 'stuff' more energy into the battery but allowing
 or recommending operations above the legacy
 levels poses system wide risks that may be
 hazardous to hardware. The batteries are at
 greater risk for catastrophic failure to
 to over-charging or hard-charging.
 So, BMS enter stage-right:
 A judicious collection of transistors and things
 can be hammered into a 'battery management system'
 that will pound our square cornered lithium
 product into a round, lead-acid hole.
 Hence, products like EarthX and AeroVoltz
 with BMS system will FUNCTION in the lead-
 acid hole with minimized risks but performance
 compromises.
 'Barefoot' lithium products will also
 function in the lead-acid world but safeguards
 offered by BMS fitted products are the
 user's responsibility.
 Bob . . .
|
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