Hybrid bus problems -- batteries
#1
10-18-2008, 09:30 AM
Join Date: Oct 2005
Location: Huntsville, AL
Posts: 5,613
Hybrid bus problems -- batteries
http://www.thestar.com/News/GTA/article/519770
Understand that there is no universal hybrid solution and an electric hybrid is not always the best solution. In the case of heavy vehicles like buses and medium to large service trucks, a hydraulic system makes a lot of sense because hydraulics can handle huge energy bursts needed for buses and trucks. In fact, I'm somewhat disappointed that GM/Chrysler/Daimler two-mode was electric based instead of hydraulic.
My Prius studies have expanded to batteries and I'm finding them to be 'good news' and 'bad news.' Yes, they help establish an electric capability in our vehicles allowing limited range, electric operation. However, batteries are finicky and difficult to properly use. Worse, they have severe limits on how much 'impulse' power they can absorb or release.
One last thing, hybrid performance is very route and driving profile sensitive. There is a reason why hybrid skeptics prefer 'long distance' highway test routes, they don't have to deal with inertial losses from start and stop driving profiles.
What is interesting in this article is the failure of lead-acid batteries, the ones we have the most experience with. I am by no means a battery expert but to have life-time issues with lead-acid suggests something is terribly wrong with the control laws of these hybrids.
GOOD NEWS! Used hybrid buses may soon become available at affordable prices!!!
Bob Wilson
Tess Kalinowski
Transportation reporter
The TTC is going back to buying diesel buses because the batteries on its newer hybrid diesel-electric models are proving too "hit and miss."
An existing order for 130 hybrids next year will go ahead, but next week TTC staff will recommend the commission approve a $61 million order for "clean diesel" buses in 2010.
. . .
The remaining 2009 hybrids will be delivered with Chrysler's new lithium-ion batteries rather than the lead-acid cells already in use on the TTC fleet. The TTC wants to test the newer batteries but isn't prepared to commit to that technology, said spokesperson Brad Ross, who didn't rule out the possibility of trying hybrids again after the 2010 order.
. . .
Batteries [lead-acid rjw] that should be lasting five years are surviving only about 18 months, which affects service because those buses have to come off the road for repairs, he said.
. . .
It was hoped the hybrid buses would save 20 to 30 per cent on fuel but they are achieving only about a 10 per cent saving, he said.
. . .
Transportation reporter
The TTC is going back to buying diesel buses because the batteries on its newer hybrid diesel-electric models are proving too "hit and miss."
An existing order for 130 hybrids next year will go ahead, but next week TTC staff will recommend the commission approve a $61 million order for "clean diesel" buses in 2010.
. . .
The remaining 2009 hybrids will be delivered with Chrysler's new lithium-ion batteries rather than the lead-acid cells already in use on the TTC fleet. The TTC wants to test the newer batteries but isn't prepared to commit to that technology, said spokesperson Brad Ross, who didn't rule out the possibility of trying hybrids again after the 2010 order.
. . .
Batteries [lead-acid rjw] that should be lasting five years are surviving only about 18 months, which affects service because those buses have to come off the road for repairs, he said.
. . .
It was hoped the hybrid buses would save 20 to 30 per cent on fuel but they are achieving only about a 10 per cent saving, he said.
. . .
My Prius studies have expanded to batteries and I'm finding them to be 'good news' and 'bad news.' Yes, they help establish an electric capability in our vehicles allowing limited range, electric operation. However, batteries are finicky and difficult to properly use. Worse, they have severe limits on how much 'impulse' power they can absorb or release.
One last thing, hybrid performance is very route and driving profile sensitive. There is a reason why hybrid skeptics prefer 'long distance' highway test routes, they don't have to deal with inertial losses from start and stop driving profiles.
What is interesting in this article is the failure of lead-acid batteries, the ones we have the most experience with. I am by no means a battery expert but to have life-time issues with lead-acid suggests something is terribly wrong with the control laws of these hybrids.
GOOD NEWS! Used hybrid buses may soon become available at affordable prices!!!
Bob Wilson
Last edited by bwilson4web; 10-18-2008 at 09:35 AM.
#2
10-22-2008, 12:10 PM
Re: Hybrid bus problems -- batteries
Although I'm not an expert on batteries, I do have some experince mostly with lead-acid, having used them in standby power supplies, telecomm backup plants, and similar uses.
The key with SLA from a long-life perspective, is to have them fully charged during periods of non-use. As a matter of fact, a small "trickle" charge is almost mandatory even if the battery is fully charged.
Also, from time to time, depending on usage and environmental conditions, the bateries must be equalized with a current limited and temperature compensated higher voltage application.
What this means is that during rest periods, i.e nights and weekends, the buses would still have to be connected to an AC source while parked.
The key with SLA from a long-life perspective, is to have them fully charged during periods of non-use. As a matter of fact, a small "trickle" charge is almost mandatory even if the battery is fully charged.
Also, from time to time, depending on usage and environmental conditions, the bateries must be equalized with a current limited and temperature compensated higher voltage application.
What this means is that during rest periods, i.e nights and weekends, the buses would still have to be connected to an AC source while parked.
#3
10-22-2008, 02:25 PM
Join Date: Oct 2005
Location: Huntsville, AL
Posts: 5,613
Re: Hybrid bus problems -- batteries
Although I'm not an expert on batteries, I do have some experince mostly with lead-acid, having used them in standby power supplies, telecomm backup plants, and similar uses.
The key with SLA from a long-life perspective, is to have them fully charged during periods of non-use. As a matter of fact, a small "trickle" charge is almost mandatory even if the battery is fully charged.
Also, from time to time, depending on usage and environmental conditions, the batteries must be equalized with a current limited and temperature compensated higher voltage application.
What this means is that during rest periods, i.e nights and weekends, the buses would still have to be connected to an AC source while parked.
The key with SLA from a long-life perspective, is to have them fully charged during periods of non-use. As a matter of fact, a small "trickle" charge is almost mandatory even if the battery is fully charged.
Also, from time to time, depending on usage and environmental conditions, the batteries must be equalized with a current limited and temperature compensated higher voltage application.
What this means is that during rest periods, i.e nights and weekends, the buses would still have to be connected to an AC source while parked.
You're doing stuff with SLA? I recently got an eBike only to find the charger was not very good. I didn't realize that unplugging and plugging in the charger into the battery while the AC was on would cause it to fail:
My design:
I'm using a solid-state relay to switch the pulsed, rectified AC to feed a current limiter that then feeds a voltage regulator. There is a blocking diode and 'in-rush' diode that allows the battery to be plugged and unplugged without risk.
The as-built from junk box parts:
Are you building your own charger(s) or using COTS?
Bob Wilson
#4
10-24-2008, 08:51 AM
Re: Hybrid bus problems -- batteries
First things first: WOW! This is the first time I see a schematic drawn using MS Excel.
If you want to do some nice looking schematics, from a freeware program, go to www.expresspcb.com and download their editor. As a bonus it also comes with freeware printed circuit board software, which you can use if you decide to build some prototypes. The prototypes are very reasonably priced.
I've been building my own battery chargers for a long time. From the very simple, to microprocessor controlled devices. It all depends how much time/effort one has and how much performance one wants.
If you want to do some nice looking schematics, from a freeware program, go to www.expresspcb.com and download their editor. As a bonus it also comes with freeware printed circuit board software, which you can use if you decide to build some prototypes. The prototypes are very reasonably priced.
I've been building my own battery chargers for a long time. From the very simple, to microprocessor controlled devices. It all depends how much time/effort one has and how much performance one wants.
#5
10-24-2008, 09:52 AM
Join Date: Oct 2005
Location: Huntsville, AL
Posts: 5,613
Re: Hybrid bus problems -- batteries
If you want to do some nice looking schematics, from a freeware program, go to www.expresspcb.com and download their editor. As a bonus it also comes with freeware printed circuit board software, which you can use if you decide to build some prototypes. The prototypes are very reasonably priced.
The complex design will replace the existing motor controller with an integrated motor controller, battery charger and AC inverter. I won't be happy until I can freely move power from AC to DC, DC to traction, traction to DC and DC to AC from one controller. Of course I'll also include instrumentation like an accurate speedometer and battery 'fuel gauge.' Then I'll be ready to work on my Prius mods. <GRINS>
Bob Wilson
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