Super capacitors replacing car battery. - Page 1
Forum section: electronics / projects

author: firepower
author_rank: Regular Contributor
timestamp: February 12, 2015, 08:00:51 am
content: http://youtu.be/z3x_kYq3mHM

author: elgonzo
author_rank: Unknown
timestamp: February 12, 2015, 08:33:16 am
content: Interesting, but not really new...http://en.wikipedia.org/wiki/Capa_vehicle#Capabus

author: max_torque
author_rank: Super Contributor
timestamp: February 12, 2015, 12:48:28 pm
content: Not only "not new" but also irrelevant!"Starting your engine" is only one thing your car battery does. These days the Hotel Loads are massive, and with smart alternators the battery is being deep cycled in order to minimise fuel consumption. Also, starting you engine on a normal day, when for all we know, it's already warmed up, is a long way from meeting OEM requirements, where they will require an un-assisted start down to around -20 degC. Then there is the issue of cost. This Supercap "battery" costs significantly more than a std lead acid battery, and will require a DC-DC convertor to use (energy contained is proportional to voltage, unlike a chemical battery).Right now, the OEMS are moving to LiPo batteries in high end weight critical applications.So, yes, you can start your engine with a super capacitor, but then you can also start it with a starting handle as well, and no one does that these days either.........

author: nowlan
author_rank: Frequent Contributor
timestamp: February 12, 2015, 01:12:22 pm
content: He leaves his car at an airport for a week, and it starts fine. I dont see the problem.

author: Pjotr
author_rank: Frequent Contributor
timestamp: February 12, 2015, 01:34:10 pm
content: Quote from: max_torque on February 12, 2015, 12:48:28 pmNot LiPo but LFP batteries. I once started my car with four 3AH LFP cells. Worked like a charm, current was about 180 amps! Have look at this company:http://www.super-b.com/en/

author: lutkeveld
author_rank: Regular Contributor
timestamp: February 12, 2015, 04:18:26 pm
content: Indeed. LiFePO4 is the future for car batteries.A123, the leading brand in the LFP spaces, makes 2.5Ah cells that can deliver 120A starting current.High temperature range, low self discharge, high energy density, high cycle life, can be charged with a lead acid charger.It's even cheaper than lead acid, considering you can get your car started with 4 cells in series (12,8v) and will last much longer.They don't have much capacity, so you have to keep your engine hot

author: max_torque
author_rank: Super Contributor
timestamp: February 12, 2015, 08:44:20 pm
content: Quote from: nowlan on February 12, 2015, 01:12:22 pmWow, a whole week, left at an airport. Best give the OEM's a bell and tell 'em he's solved ALL their problems!In reality, Hotel loads can be on cars left parked for months, in -20 degC ambients, cars where the battery is non fully charged before the engine is shut down (because modern cars use the battery to do load leveling, and only charge it when the vehicle is in overrun etc). People can sit in cars, with the radio on full blast for hrs, then add in heated seats, heated screens, high power cooling fans, multiple fuel pumps, numerous infotainment systems etc. What you'll notice is that modern cars have BIG batteries!(Starting a engine, in a car in good condition is not that hard, or uses that much energy (typically, 50Nm crank torque at an average speed of 150rpm, so approx 0.8kW, add in an overall efficiency of say 65%, so that's 1.2kW. And a modern engine can start well inside 1 second, even from cold, so total power used is 1.2kJ.)

author: mtdoc
author_rank: Super Contributor
timestamp: February 12, 2015, 08:59:29 pm
content: Quote from: lutkeveld on February 12, 2015, 04:18:26 pmThe issue with LiFePO4 for this application is that they are much less tolerant of abuse. Severely overcharging or undercharging a lead acid battery will shorten its lifespan but will not immediately kill it like it will a LiFePO4.More sophisticated electronics to prevent that would need to be implemented in autos. The expense of that combined with the higher cost of the batteries themselves means Lead Acid batteries will continue to the batteries of choice for auto starting ICE auto accessory applications for some time to come.Even my Volt - which has a very large Lithium battery bank, uses a 12V lead acid battery for starting the ICE and for powering accessories in the car.

author: Pjotr
author_rank: Frequent Contributor
timestamp: February 12, 2015, 09:35:37 pm
content: Sure, all Lithium chemistry batteries of more than one cell need a sophisticated battery management system. The battery makers (who are others than the cell manufacturers) incorporate that in their batteries most time. But for the main battery of PEV's and PHEV's lead acid is a no go, simply because of weight and size.But look at the price of Li powered hand held tools nowadays. The better ones also use LFP batteries and have sophisticated electronics to watch the batteries at charge and discharge.

author: LaurenceW
author_rank: Frequent Contributor
timestamp: February 12, 2015, 11:03:34 pm
content: Hmm - think about discharge curves. Most batteries of any chemistry will deliver their energy at a (largely) constant rated voltage, until they get to their rated output, when the voltage starts to drop off rapidly.Capacitors of any type, on the other had, will deliver their energy while the voltage drops much faster. This graph says it allhttp://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http%3A%2F%2Fwww.tecategroup.com%2Fultracapacitors-supercapacitors%2Fultracapacitor-FAQ.php&ei=AS3dVNvICcKrUc6og7gL&bvm=bv.85970519,d.d24&psig=AFQjCNGz51flDXe6n5ZfrNzfiNhl1wphuw&ust=1423867519799151It's all down to basic math. Energy=half Capacitance x Voltage squared, and "ya canny change the laws of physics, cap'n"Supercaps have their place, but one bloke showing that it is at leastpossible(and quite interesting!) to start a car with them, their energy density and discharge characteristic make them (excuse me) "non starters" (look, I said i was sorry) for engine start applications, IMHO

author: Nerull
author_rank: Frequent Contributor
timestamp: February 12, 2015, 11:12:57 pm
content: Quote from: mtdoc on February 12, 2015, 08:59:29 pmCars don't cost $2, I think they can handle a battery management circuit. Its not like they aren't already full of complex electronics.

author: lutkeveld
author_rank: Regular Contributor
timestamp: February 12, 2015, 11:22:33 pm
content: A BMS/PCM is IMO a requirement for a LiFePO4 pack. Overcurrent, low-voltage, high temp, balancing etc...

author: suicidaleggroll
author_rank: Super Contributor
timestamp: February 12, 2015, 11:49:12 pm
content: Quote from: lutkeveld on February 12, 2015, 11:22:33 pmLow temp is a problem for them as well. You can't charge a lithium battery below 0C at high currents or you'll damage it. It's not such a big deal for the primary battery in electric cars because the charging current is still relatively low compared to the battery capacity (.1C or lower), but I don't think a small battery just big enough to start an ICE would be able to handle a 100+ amp charging current from the alternator if it's below 0C without damage.

author: mtdoc
author_rank: Super Contributor
timestamp: February 13, 2015, 12:06:05 am
content: Quote from: Nerull on February 12, 2015, 11:12:57 pmThe point is it's an added expense and point of failure. A proper auto BMS will need to be more robust than what is typically used in many other applications. Typical auto alternator charging circuits are all over the place and would quickly kill a lithium battery.Making a LiFePO4 starting battery system that was as reliable as the current lead acid variety would not be cheap.Any added cost for battery and BMS would need to be justified by improved performance. Current lead acid starting batteries - while imperfect - are considered "good enough" and therefore are unlikely to be replaced anytime soon IMHO.

author: Circlotron
author_rank: Super Contributor
timestamp: February 13, 2015, 02:27:26 am
content: I think the ticket would be to put some supercaps across an existing lead acid battery. Would likely extend the useable lifetime because when the battery can no longer supply the cranking current it could still charge the caps. This would especially be true in cold climates.

author: LabSpokane
author_rank: Super Contributor
timestamp: February 13, 2015, 05:48:04 am
content: Quote from: Circlotron on February 13, 2015, 02:27:26 amhttp://www.maxwell.com/esm/And that is exactly the intended use. Maxwell has been selling parallel batteries to fleet operators for a few years now.

author: eneuro
author_rank: Super Contributor
timestamp: February 13, 2015, 08:02:14 am
content: Quote from: LabSpokane on February 13, 2015, 05:48:04 amHow much does it cost lets say for 2L Diesel HDI ?This Maxwell ESM has 4 years varanty, similar to crappy classic lead acid car battery, so it have to be priced much lower else it doesn't make any sense to put such ultracapacitors into classic combustion engine car, but well those ESMs can be interesting option for small EV (electric vehicle owners) and usable at regenerative breaking stages, but futher investigation needed and we need to see its charge discharge chracteristics, but anyway it looks like those ESMs could be still usable to reuse this breaking energy to power up onboard EV equipment, etc, so it is quite interesting option

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 13, 2015, 08:08:29 am
content: Where supercaps could potentially make a difference is in regenerative braking. Their ability to accept very large currents are a perfect match for that application. Likewise, their ability to supply very large currents would take EVs to a whole new level. (Just beware the extreme arc flash hazard of such a cap bank!)

author: eneuro
author_rank: Super Contributor
timestamp: February 13, 2015, 01:38:47 pm
content: Quote from: NiHaoMike on February 13, 2015, 08:08:29 amNot so easyWhich is capacity of those magic ultracapacitors 12V car starter batteries?I saw 350F 2.5V in those custom based ones, which means that 6 such caps in series give us theoretical 15V @ ONLY 6.6kJ of total energy100kg mass at speed 50km/h~14m/s has kinetic energy 9.6kJ and with human weight lets say 75kg and... light bike we have easy 100kg total mass, so it means we can imagine the magnitudes of regenerative brakeing storage capabilities needed when... 10 times bigger object is moveing - 10 times more kinetic energyIt looks like for the moment flywheel KERS is better option and it was my huge interest into this technology a few years ago and this is technology I've choosen for my HPEV too, I was banned in one of the EV forums a few years ago while started talking about this, but... that is fine-moderators somethimes are not very creative...and have no great ideas...It was also used in F1 some time ago and it attracted my attention, but modern ultracapacitors seams to be very usefull too in EVs but rather as smaller energy storage systems and it is worth to investigate and maybe upgrade my HPEV design

author: SeanB
author_rank: Super Contributor
timestamp: February 13, 2015, 03:14:55 pm
content: I am using a few parallel capacitors on the battery of my UPS. Around 0.2F of capacitance does make a difference in run time, especially as the battery discharges and internal resistance increases. Added about 15% of extra runtime before low voltage cut out to this application.