787 Batteries and Chargers - Part 1

[FullWings]

Mildly off-topic but the linked report from the Daily Mail above was actually a pretty good piece of factual journalism, with a lot of material brought together plus some photos I hadn't seen before. Credit where credit is due.

[pax2908]

Pic#4 from dailymail, shows a good battery with what appears to be an insulating cover (Teflon perhaps?) - I am wondering if that is a temporary protection (against dropping tools etc. before closing the blue box) or on the contrary it is to be installed permanently?

[cockney steve]

@ Turin...Yes, I understand that in an emergency, you MIGHT want to pull the last dregs out of the MAIN battery....but isn't that why it carries 2 apparently identical units?
Even allowing for the extra cost of certifying these units, they really don't come into the realms of "disposable"...at the price, I suggest that , presently,(grounding excepted) the saving on fuel and space has been wiped out several-fold by the sheer cost of these constant swap-outs

At a couple of thousand dollars each (still a lot of jet-fuel) I'd go along with it.

BUT they're tens of thousands of dollars a pop and at that price, if I were a "punter" I.E. a Boeing customer, I'd expect my Lithium batteries to be effectively managed to give me COST-EFFECTIVE Emergency power
It's not beyond the wit of smart engineers to design a proper, effective battery-management system,possibly with automatic sensing to accass that final, destructive reserve of energy.


It hasn't been done and I'd imagine the owners of these White Elephants feel well and truly shafted......save 20% on fuel, but spend multiple times that on batteries....free Russian Roulette every time your pilots switch on....will it work or will it burn?.......Yea! brilliant sales-pitch....NOT.

I'm with the majority of the last few posters.....faulty management...both in Boeing and in the Battery-system.

I've been saying it all along,- modellers have been using lithium cells for a long time now, they have fires, cell-failures and crashes...but you have to be careful playing with a 2-metre diameter flying scythe and I'm certain the lithium cells have had a lot harder use, with a far longer time between failures than the Thales item.
These modellers are NOT professionals, but they understand the care of their motive-power and subject them to very heavy currents-by the nature of R C helicopters, EVERY cycle is using the maximum safe capacity.

If they can do it,as hobbyists, why can't the might of Boeing, Thales and Securaplane , manage a "floating " emergency battery and an APU starter-battery. Even making the (probably wrong) assumption that the APU is used at every start to give start power for the main engines, there's still the pushback, engine -warm-up and taxiing times for the APU battery to recharge.

To suggest that it's not possible to operate this battery well within it's safe operating parameters is codswallop.

defective management (human and charging/monitoring. )

[syseng68k]

USMCProbe:

Have seen a fair amount of Japanese electronics from the inside and while some
of the design can seem a little laboured, the attention to detail was second to none.
Might have slipped a bit during the past few years, but still pretty good.
It's going that extra mile that differentiates world class from ho-hum products, imo.

In some ways ironic, but the original Japanese quality program was started by an
American just after WWII. Now they export the ideas back to us...

[Speed of Sound]

Pic#4 from dailymail, shows a good battery with what appears to be an insulating cover (Teflon perhaps?) - I am wondering if that is a temporary protection (against dropping tools etc. before closing the blue box) or on the contrary it is to be installed permanently?

Given that it doesn't cover the most delicate part of the system (the PCBs and multi-pin connectors) but does cover the battery terminals I would suggest that this insulation is installed permanently to prevent any shorting of the exposed battery terminals, particularly from damage caused to the fairly thin (conducting) case lid less than 1cm above them.

save 20% on fuel, but spend multiple times that on batteries....

I very much doubt that ANY customer will have paid the estimated $66,000 replacement cost for any of these batteries unless it can be proved that the battery was rendered u/s by customer mishandling.

[syseng68k]

Speed of Sound:

Didn't someone else mention $12k as being the actual cost ?.

I would have thought that there would be an exchange program for such an item, as
they are too expensive just to scrap because of a eg: battery low diagnostic message.

Edit: How do I post an image here if the box lower left says I can't post
attachments ?.

Have a block diagram / schematic and description to post...

[green granite]

syseng68k see:

http://www.pprune.org/spectators-bal...une-guide.html

[Speed of Sound]

I would have thought that there would be an exchange program for such an item, as they are too expensive just to scrap because of a eg: battery low diagnostic message.

I agree, although after a certain number of 'returns' I suspect Boeing/Thales/Yuasa would want to take a good look at these batteries rather than have them taken apart for reconditioning and put back into service.

I'd love to know the proportion of these replacements made to the 'APU' as opposed to the 'main'. If it is heavily weighted towards one or the other, that would be a big clue as to what was happening. Even if it was 50/50 it would help as that points towards a 'battery/charging' problem rather than a 'load/operation' problem.

[syseng68k]

green granite:

Thanks for that. The confusion was over the description in the faq section, which
said something about uploading images via the attachment process. Photobucket it
is then.

If it no longer works, then perhaps the faq should say so ?...

[syseng68k]

Battery Subsystem

Hi,

Here's a quick block diagram of all the major parts and their connections for the
battery subsystem. Info from what we know already and what seems to make sense.



Going from left to right:

External comms datalink:
Provides external comms access to the battery subsystem,
for control and status purposes from other a/c systems.

Charger & Control:
Manages the overall subsystem and has several functions:
Conditions input power to charge the battery.
Monitors the charge and discharge processes to keep
battery operation within safe limits.
Records normal and abnormal operation and events.
Provides a command set for control and status from
external systems.
Has extensive continuous built in test functions.

Control, Status and Heartbeat datalink:
Communication between charger and Battery Management System
Detects failure of communication between charger and BMS.

Battery Management System, BMS:
Measures each cell's voltage and temperature.
Balances cell voltages in relation to each other.
Communicates with the charger to report cell voltage,
temperature, normal and abnormal conditions.
Has it's own built in test functions.

Cell Voltage Measurement and Cell Balancing, a-i:
Measures each cell's voltage
Balances each cell's voltage

Temperature Sensors, 1-8:
Individual sensor mounted on each cell to provide cell
temperature measurement.

8 Cells:
4 volts nominal, 75 ampere hours each.

Contactor / Relay:
Provides electrical isolation for the series string of cells.

For the 787 system, some of above is guesswork, but is what I would
consider a minimum set of functionality for such a system. It's only
a back of envelope description though and a bare bones example.

Anyway, feel free to tear it apart, criticise, whatever...


PS: Posting images: they changed the interfaces on Photobucket, but got there
eventually

[Speed of Sound]

syseng

Thanks for that.

Does anyone know where the temperature sensors are situated? The only pics of the undamaged batteries I have seen have the insulator cover over the connections and I can't see where the sensor wires terminate on the damaged batteries.

[syseng68k]

Speed of Sound:

We don't have that info. Ideally a single sensor per cell, otherwise rapid temperature
rise in a single cell may not be seen in time to shut the system down...

[kilomikedelta]

SpeedOfSound, Posts #142 and #158 of this thread show the monitor connections although I don't see anything going to a temperature sensor.

[Speed of Sound]

kilomikedelta

Thanks for that.

Either my eyes are going or the resolution isn't good enough to see exactly where each sensor wire is teminated at the battery end. I may be wrong but they all seem to be connected to cell terminals or shunts including a number that seem to be connected to 'bits of metal' which are at the same potential!

[TURIN]

Cockney Steve,

Turin...Yes, I understand that in an emergency, you MIGHT want to pull the last dregs out of the MAIN battery....but isn't that why it carries 2 apparently identical units?

No, the APU and Main batteries perform completely different and seperate functions. You cannot use power from the Main Battery to start the APU anymore than you can use the APU battery to power the brakes unless you physically disconnect them and swap their positions. Do-able on the line to get the a/c back home but not a switchable feature from the flightdeck.

Even allowing for the extra cost of certifying these units, they really don't come into the realms of "disposable"....

In the event of an emergency they will be.

Normal ops they shouldn't be.

BUT they're tens of thousands of dollars a pop and at that price, if I were a "punter" I.E. a Boeing customer, I'd expect my Lithium batteries to be effectively managed to give me COST-EFFECTIVE Emergency power
It's not beyond the wit of smart engineers to design a proper, effective battery-management system,possibly with automatic sensing to access that final, destructive reserve of energy.

Absolutely.

....If they can do it,as hobbyists, why can't the might of Boeing, Thales and Securaplane , manage a "floating " emergency battery and an APU starter-battery. Even making the (probably wrong) assumption that the APU is used at every start to give start power for the main engines, there's still the pushback, engine -warm-up and taxiing times for the APU battery to recharge.

Assuming the APU battery was used to start the APU of course, which during normal turnround ops it won't be as ground power will be attached.

[rottenray]

Mildly off-topic but the linked report from the Daily Mail above was actually a pretty good piece of factual journalism, with a lot of material brought together plus some photos I hadn't seen before. Credit where credit is due.

OMG U R SO RITE!

Seriously, ALL of the images in that "article" are available elsewhere, with far less "journalistic license" surrounding their publication.

[StinkyMonkey]

A350 Batteries

I've been led to believe that the A350 is not likely to have the same problems with it's Lithium-Ion batteries as Boeing due to a difference in the design, and consequently smaller batteries will be used.

Can anyone familiar with the A350 development verify/deny/enlighten?

[FullWings]

Seriously, ALL of the images in that "article" are available elsewhere, with far less "journalistic license" surrounding their publication.

I think you'll find that applies to almost all news media today, in that it's bought/fed from Reuters, UPI, etc. Most of the aviation related material in cases like this comes from sources like the NTSB & JTSB.

One issue that crops up very regularly in PPRuNe is the standard of reporting when it comes to anything aviation related, especially incidents or accidents. If you don't live in the UK, maybe it doesn't surprise you when a tabloid newspaper produces a largely factual report on what (to the general public, at least) is a fairly technical issue. We who inhabit this small, damp island have to re-read it several times to confirm that it doesn't mention politicians' misdemeanours, football or breasts in the narrative.

Now back to batteries...

[saptzae]

@syseng68k - #570

You can't use same connection for monitoring and balancing, as the balancing current would introduce substantial measurement errors. Thus, there must be two separate pairs of wires per cell, one for monitoring and one for balancing.

Existing batteries show no indication of per cell temperature monitoring. Per cell temperature monitoring accomplishes nothing as the lag would be seconds.

An infrared camera may be of interest though, as long as it could detect an cell-internal arc withing a millisecond or so. I have no experience with infrared and don't know whether feasible.

IMHO, there will be at most a few milliseconds available to shut charging down after a cell short, to prevent damage to other cells.

Most important is to quickly detect a cell short (via voltage) transients and disable the charger. When in doubt, don't charge!

I read that some of the small standard cells have a disconnect feature on pressure rise. Pressure monitoring may also be of interest?

[Speed of Sound]

BMS connections.

I have taken this pic from the NTSB Powerpoint presentation which is the highest resolution image I can find of the monitoring connections to the individual cells.

No obvious temperature sensor connections although the chewing gum/cotton wool over the shunt between the middle two cells on the LHS of the array looks as though it could be hiding something although it is probably just a mirror of the connection on the shunt of the RHS.

Ybat787_zpsff032c0d.jpg Photo by SoS57 | Photobucket