787 Batteries and Chargers - Part 1
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 81
Posts: 1,454
Likes: 0
Received 0 Likes
on
0 Posts
After looking at the picture of the exemplar battery in the NTSB report, one thing puzzles me about the smaller monitoring wires. There appear to be 3 wires that are attached to electrically potential-equivalent points on each inter-cell junction.
One on a cell connector on one side of a battery cell, one on the interconnector that connects to the next cell, and one on the cell connector on the other side of of the interconector. (Hope that is clear)
I cannot believe that these wires are all measuring potential. Some of them are either shunt wires or serving some other function such as temperature monitoring (although how that might happen is not obvious)
One on a cell connector on one side of a battery cell, one on the interconnector that connects to the next cell, and one on the cell connector on the other side of of the interconector. (Hope that is clear)
I cannot believe that these wires are all measuring potential. Some of them are either shunt wires or serving some other function such as temperature monitoring (although how that might happen is not obvious)
Last edited by Machinbird; 27th Jan 2013 at 17:31. Reason: add hyphen
Lyman
I'm not sure about that. I read somewhere else that there is system / operating
requirement that the APU battery be fast charged over a time scale and at a rate
that would not be possible using lead acid or nicad.
Engineering of this type has nothing to do with emotion, seduction etc, other
than the usual designer's passion to do the job right :-).
Who knows what we will be told though. With so many $ at stake, some of the
vendors could be bankrupted if found to be at fault...
Regards,
Chris
Boeing demonstrated no need for the Lithium Battery
requirement that the APU battery be fast charged over a time scale and at a rate
that would not be possible using lead acid or nicad.
Engineering of this type has nothing to do with emotion, seduction etc, other
than the usual designer's passion to do the job right :-).
Who knows what we will be told though. With so many $ at stake, some of the
vendors could be bankrupted if found to be at fault...
Regards,
Chris
Join Date: Aug 2011
Location: hong kong
Age: 63
Posts: 93
Likes: 0
Received 0 Likes
on
0 Posts
@Turin
Thank you. That eliminates the bus as the culprit at BOS. Cause of other cells destruction is down to the charger, continuing to power the battery after failure of #3, or purely thermal.
The APU AC BUS can be tied to the L and R AC busses.
Join Date: Aug 2011
Location: hong kong
Age: 63
Posts: 93
Likes: 0
Received 0 Likes
on
0 Posts
@Machinbird
Redundancy of sensing and balancing?
Edit: Upper PCB looks like for control and sensing. Lower PCB for balancing. Seems to be a lot of electronics for this functionality.
After looking at the picture of the exemplar battery in the NTSB report, one thing puzzles me about the smaller monitoring wires. There appear to be 3 wires that are attached to electrically potential-equivalent points on each inter-cell junction
Edit: Upper PCB looks like for control and sensing. Lower PCB for balancing. Seems to be a lot of electronics for this functionality.
Last edited by saptzae; 27th Jan 2013 at 17:45. Reason: PCB
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
Hi, cwatters (#199)
I yet expressed my concern on the max current the main battery is alowed to supply the DC bus. In an earlier post we discussed the issue.
Points to mention:
1) As confirmed by TURIN there is a diode module easily understood as the switch that put the (charged) battery in the bus. I agree with your concern that a limiter is important. I consider ESSENTIAL when using these dangerous batteries, letīs say, DANGEROUS CELLS. Even with superb circuitry they will remain DANGEROUS.
2) A limiter to be safe must be integrated to the System Software (unless you put a FE in the cockpit). Which are the priorities when the bus needs the help from the (main) battery?
3) As i understand the Battery charger is connected BETWEEN the battery and the diode module. The management of the best configs in a degrading scenario is not so simple.
4) And you must always respect the weakness and criticality of the dangerous cells. Who in the project made the algorithms ? (required and certainly existent). Boeing or a partner?
Integration teething pains? Or nightmare?
I yet expressed my concern on the max current the main battery is alowed to supply the DC bus. In an earlier post we discussed the issue.
Points to mention:
1) As confirmed by TURIN there is a diode module easily understood as the switch that put the (charged) battery in the bus. I agree with your concern that a limiter is important. I consider ESSENTIAL when using these dangerous batteries, letīs say, DANGEROUS CELLS. Even with superb circuitry they will remain DANGEROUS.
2) A limiter to be safe must be integrated to the System Software (unless you put a FE in the cockpit). Which are the priorities when the bus needs the help from the (main) battery?
3) As i understand the Battery charger is connected BETWEEN the battery and the diode module. The management of the best configs in a degrading scenario is not so simple.
4) And you must always respect the weakness and criticality of the dangerous cells. Who in the project made the algorithms ? (required and certainly existent). Boeing or a partner?
Integration teething pains? Or nightmare?
Machinbird
There was a brief explanation in post, #177 but put more simply, the use of
two wires to each cell isolates that cell measurement from any interaction with
the other cell voltages and currents.
Also, wires may be dualled in some places to provide redundancy against a
single wire break. This would also allow diagnostics to detect a broken wire.
Such dualling is not uncommon...
Regards,
Chris
After looking at the picture of the exemplar battery in the NTSB report, one thing puzzles me about the smaller monitoring wires. There appear to be 3 wires that are attached to electrically potential-equivalent points on each inter-cell junction.
two wires to each cell isolates that cell measurement from any interaction with
the other cell voltages and currents.
Also, wires may be dualled in some places to provide redundancy against a
single wire break. This would also allow diagnostics to detect a broken wire.
Such dualling is not uncommon...
Regards,
Chris
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
Redundancy?
Hi,
Machinbird (#201)
Redundant wiring...
What the designers made is still beyond my imagination.
The thin wires, over the cells, the connectors used and TWO PCBīs all inside the chamber where the hot cells are is UNBELIEVABLE.
Machinbird (#201)
Redundant wiring...
What the designers made is still beyond my imagination.
The thin wires, over the cells, the connectors used and TWO PCBīs all inside the chamber where the hot cells are is UNBELIEVABLE.
Last edited by RR_NDB; 27th Jan 2013 at 17:56. Reason: Typo and add title
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,074
Likes: 0
Received 0 Likes
on
0 Posts
syseng68k
Quote:
Boeing demonstrated no need for the Lithium Battery? (sorry, my quote)
You reply...I'm not sure about that. I read somewhere else that there is system / operating requirement that the APU battery be fast charged over a time scale and at a rate that would not be possible using lead acid or nicad.
And, they would not have. If FAA requires a performance level that cannot be met with current technology, then they have gone into the design business. And Boeing would not design an aircraft that could not be built under current regs. Would they build a bird that was dependent on concurrent rule change? No, the rule predated the design...
If that is the case, the Dreamliner is dead. It is at least cemented in concrete to Lithium....because without back up electric, no current a/c can be airworthy. And if 787 won't certify with anything but Lithium.....
Maybe the bridge back to NickelMH burned in the EEbay?
Quote:
Boeing demonstrated no need for the Lithium Battery? (sorry, my quote)
You reply...I'm not sure about that. I read somewhere else that there is system / operating requirement that the APU battery be fast charged over a time scale and at a rate that would not be possible using lead acid or nicad.
And, they would not have. If FAA requires a performance level that cannot be met with current technology, then they have gone into the design business. And Boeing would not design an aircraft that could not be built under current regs. Would they build a bird that was dependent on concurrent rule change? No, the rule predated the design...
If that is the case, the Dreamliner is dead. It is at least cemented in concrete to Lithium....because without back up electric, no current a/c can be airworthy. And if 787 won't certify with anything but Lithium.....
Maybe the bridge back to NickelMH burned in the EEbay?
Last edited by Lyman; 27th Jan 2013 at 22:19.
What the designers made is still beyond my imagination.
The thin wires, over the cells, the connectors used and TWO PCBīs all inside the chamber where the hot cells are is UNBELIEVABLE.
The thin wires, over the cells, the connectors used and TWO PCBīs all inside the chamber where the hot cells are is UNBELIEVABLE.
for the death of the battery is lost forever
How that ever got past systems engineering beats me...
Regards,
Chris
Last edited by syseng68k; 27th Jan 2013 at 18:04.
Join Date: Aug 2011
Location: hong kong
Age: 63
Posts: 93
Likes: 0
Received 0 Likes
on
0 Posts
@RR_NDB
As to electronics in the same box, I prefer this over adding another box. The wiring to it could not practically be protected.
I am still trying to understand the failures.
Could one make the thing simpler and thereby safer? Perhaps.
The thin wires, over the cells, the connectors used and TWO PCBīs all inside the chamber where the hot cells are is UNBELIEVABLE
I am still trying to understand the failures.
Could one make the thing simpler and thereby safer? Perhaps.
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
Battery voltage measurement
Hi,
On the 6 wires attached to ea. one battery terminals (strips) we may comment:
1) They measured the voltage in the best circuit points. Inside the battery and directly at cells
2) Redundancy may explain half of the wires (triple) with a voting scheme.
3) Other 2 (1 in ea. strip) could be to simplify the measurement of the adjacent cells voltage (near to minus and plus battery terminals)
4) The remaining two could be the mentioned bypass.
IMHO the matching using bypass is not the best way as emphasized when comment on much safer parallel charging.
On the 6 wires attached to ea. one battery terminals (strips) we may comment:
1) They measured the voltage in the best circuit points. Inside the battery and directly at cells
2) Redundancy may explain half of the wires (triple) with a voting scheme.
3) Other 2 (1 in ea. strip) could be to simplify the measurement of the adjacent cells voltage (near to minus and plus battery terminals)
4) The remaining two could be the mentioned bypass.
IMHO the matching using bypass is not the best way as emphasized when comment on much safer parallel charging.
Last edited by RR_NDB; 27th Jan 2013 at 18:24. Reason: Typo
saptzae:
In fact, you don't need another box. There's already a multipin connector
back to the charger and one would expect the battery sensing and management
electronics to be in the charger enclosure, not at the battery, where it's
vulnerable to cell leakage.
Imho, the only things that should be in the enclosure are the cells and
perhaps a small pcb supported by the connector, carrying inline fuses to
protect critical wiring.
We just might have to agree to differ on this one, but it all helps the
enquiry :-)...
Regards,
Chris
As to electronics in the same box, I prefer this over adding another box.
The wiring to it could not practically be protected.
The wiring to it could not practically be protected.
back to the charger and one would expect the battery sensing and management
electronics to be in the charger enclosure, not at the battery, where it's
vulnerable to cell leakage.
Imho, the only things that should be in the enclosure are the cells and
perhaps a small pcb supported by the connector, carrying inline fuses to
protect critical wiring.
We just might have to agree to differ on this one, but it all helps the
enquiry :-)...
Regards,
Chris
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
Same box separated chambers
Hi saptzae,
They could use separated chambers. The sensing AND the preprocessing of the voltages and temperature as you know is highly CRITICAL. The connectors used inside the same enviroment is a weak point. The harness (testability) another issue.
The failure of both batteries perhaps can be explained by the only thing common in both incidents. The battery itself. Heat and electrolyte leakage conpromising this circuitry not adequately located.
They could use separated chambers. The sensing AND the preprocessing of the voltages and temperature as you know is highly CRITICAL. The connectors used inside the same enviroment is a weak point. The harness (testability) another issue.
The failure of both batteries perhaps can be explained by the only thing common in both incidents. The battery itself. Heat and electrolyte leakage conpromising this circuitry not adequately located.
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
Hi,
Chris @ #209
Indeed. We can strongly suspect we lost the information. Why?
If the measurement is conpromised (as happens in Pitot icing) the recorded parameters are useless.
We will need better ways to monitor these Dangerous Cells in order to allow the to be used in airliners.
Still LOLīng on the "999% required"
Chris @ #209
Indeed. We can strongly suspect we lost the information. Why?
If the measurement is conpromised (as happens in Pitot icing) the recorded parameters are useless.
We will need better ways to monitor these Dangerous Cells in order to allow the to be used in airliners.
Still LOLīng on the "999% required"
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 81
Posts: 1,330
Received 0 Likes
on
0 Posts
Originally Posted by syseng68k
Imho, the only things that should be in the enclosure are the cells and perhaps a small pcb supported by the connector, carrying inline fuses to protect critical wiring.
Join Date: Feb 2011
Location: Nearby SBBR and SDAM
Posts: 875
Likes: 0
Received 0 Likes
on
0 Posts
Ni Cd
Bear @ #208
The retrofit to Ni Cd is (technically speaking) ABSOLUTELY POSSIBLE.
Problem is problems are mounting and the technical aspect is one among other.
The Review is IMO the major issue.
A virtual stalemate was created with the threat to make everybody loose.
And the chances to precisely identify what led to BOS fire and TAK smoke are not 100%
The retrofit to Ni Cd is (technically speaking) ABSOLUTELY POSSIBLE.
Problem is problems are mounting and the technical aspect is one among other.
The Review is IMO the major issue.
A virtual stalemate was created with the threat to make everybody loose.
And the chances to precisely identify what led to BOS fire and TAK smoke are not 100%
Last edited by RR_NDB; 27th Jan 2013 at 20:38.
Join Date: Jul 2009
Location: France - mostly
Age: 84
Posts: 1,682
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Machinbird
There appear to be 3 wires that are attached to electrically potential-equivalent points on each inter-cell junction.
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,074
Likes: 0
Received 0 Likes
on
0 Posts
RR_NDB
Possible in every way but one? If Boeing utilizes the Licell pursuant to the "waiver" (the 'restrictions') because their design cannot accomodate NiMH, then they cannot even propose it.
They then sink or swim with LiPolymer. To do that, they must redesign the entire technology. They then have to show, against existing prejudice and accident history, that LiPolymer is safe, to a degree established by the authority that put them on the ground.
Why are the cells wrapped rectangularly? From a geometric standpoint, why not cylindrical? Flattening a two phase material roll creates build at the edges, and ooze at the ends. Why conductors at the top, not the side? Why stacked chock a block in a cube, instead of nested in a "honeycomb, horizontally? Why then a conductor for a case, and not a cast ceramic vault?
A thin layer of plastic to isolate the looms from solid metal conductors, so the insulation fails, and the sensing and control looms all short together?
A lash up, suitable for Mickey Rooney's soap box racer?
Possible in every way but one? If Boeing utilizes the Licell pursuant to the "waiver" (the 'restrictions') because their design cannot accomodate NiMH, then they cannot even propose it.
They then sink or swim with LiPolymer. To do that, they must redesign the entire technology. They then have to show, against existing prejudice and accident history, that LiPolymer is safe, to a degree established by the authority that put them on the ground.
Why are the cells wrapped rectangularly? From a geometric standpoint, why not cylindrical? Flattening a two phase material roll creates build at the edges, and ooze at the ends. Why conductors at the top, not the side? Why stacked chock a block in a cube, instead of nested in a "honeycomb, horizontally? Why then a conductor for a case, and not a cast ceramic vault?
A thin layer of plastic to isolate the looms from solid metal conductors, so the insulation fails, and the sensing and control looms all short together?
A lash up, suitable for Mickey Rooney's soap box racer?
Last edited by Lyman; 27th Jan 2013 at 22:21.