Brammo Empulse battery

[protomech]

Leyden Energy has posted some details about their batteries now on their site.

Their site lists three battery formats: cylindrical 18650 (18mm diameter, 65mm length), pouch, and pack. Pouch batteries have been used in car-sized packs before - see the very interesting ProEV electric impreza racecar - but cylindrical packs are more common. See tesla roadster, insight, killacycle.

Leyden 18650 is rated at 3.7v, 2.2ah. 43g gives 190 wh/kg, not far off of the earlier quote.

With a bit of guessing, that gives the following battery configurations:

Empulse 6.0 24s 30p = 88.8v 66ah 5.86kwh 30.8kg
Empulse 8.0 24s 40p = 88.8v 88ah 7.81kwh 41.1kg
Empulse 10.0 30s 40p = 110v 88ah 9.77kwh 51.4kg

24s 30p means 30 cells in parallel, 24 cells in series (720 cells in total).

Leyden claims 1000 cycles @ 100% DOD (no mention of temp, cells are claimed to be very tolerant of high temperatures).

Also worth noting. The Empulse 10.0 should be able to get about 60% more power out of its pack than the Empulse 6.0. If the controller / motor / gearing were upgraded on the Empulse 10.0, it should have a top speed somewhere north of 120-130 mph. Imagine a 60kw / 100hp big motor kit for the Empulse..

[GeorgeS]

Thx proto,
I'll have to study this some more. Did you go thru the volume numbers?? Will all those batteries fit in the space allotted within the frame??. Also 2.2 ah doesn't seem that good of an energy density. The original Tesla roadster batts were 2.2 of course if we can go 100% DOD that makes a big diff. and 1000 cycles is that good?? at once a day that's only 2.7 yrs.

GSB

[protomech]

Thx proto,
I'll have to study this some more. Did you go thru the volume numbers?? Will all those batteries fit in the space allotted within the frame??. Also 2.2 ah doesn't seem that good of an energy density. The original Tesla roadster batts were 2.2 of course if we can go 100% DOD that makes a big diff. and 1000 cycles is that good?? at once a day that's only 2.7 yrs.

GSB

Bear in mind that's 1000 complete cycles - 2000 50 to 100% discharge/charge cycles causes roughly as much wear as 1000 0 to 100% cycles. 1000 cycles at 100% DOD is 60k miles** for the Empulse 6.0, 100k** miles for the 10.0. 100k miles of riding in 2.7 years would be an impressive feat!

** your mileage will vary

Life cycle performance is negatively impacted by a number of factors:
* higher temperature during charge or discharge
* higher rates of charge or discharge
* increasing age of the battery

For example, the Valence packs used in the Enertia are tested in the lab for 1600 cycles @ 45°C, 2600 cycles @ 23°C with a 0.5c charge/discharge. The "C" rating for battery charge/discharge is rated in multiples of the battery's amp-hour rating, for example a 3.7v 2.2ah discharging at 0.5c is 1.1a. Similarly, a 3.08kwh enertia pack discharging at 0.5c is 1.54 kw.


Note above that battery life is typically tested to 80% capacity. So after 1000+ nominal cycles on the Empulse, you should have around 80% of your original capacity remaining. 80 miles on an Empulse 10.0, 48 miles on an Empulse 6.0. You can continue to use the bike with the diminished range, or you can replace the packs. The older reduced capacity packs can be recycled or used for fixed energy storage, where decreased specific energy isn't hugely important.

The Tesla Roadster is a good point of comparison. The Roadster pack is 99S 69P, for a total of 6831 cells (vs 1200 similar-size cells in the empulse 10.0). The Roadster's cells are rated at 3.79v and 2.23 ah, so they are very similar in size and capacity to the Leyden Energy cells.

The big difference is weight; I haven't seen quotes for the Roadster individual cell weights, but the complete pack weighs in at 900 lbs. Counting packaging, each cell averages out at 60g, vs 43g for the Leyden Energy cells sans packaging. I don't have any feel for much weight the packaging adds.

The Roadster's battery is pack is also rated to 50k miles @ 70% remaining capacity (see, that's cheating . At roughly 250 miles/cycle, that's only 200 complete cycles, and probably 130-150 cycles @ 80% remaining capacity. It's not fair to compare cycle counts without knowing the test temperature or the charge/discharge rate, but it seems the batteries in the Empulse and the Enertia will hold up better.

[HighlanderMWC]

Now you're concerning me about my Enertia's pack. I'm usually riding more like 2-2.5kW discharge (3-5kW on hills and starts if I'm taking it easy) and discharging to say 15% (typical low of 8% high of 20%) daily (weekdays).

[GeorgeS]

Thx for the detailed response. I will get back-GSB

[protomech]

Now you're concerning me about my Enertia's pack. I'm usually riding more like 2-2.5kW discharge (3-5kW on hills and starts if I'm taking it easy) and discharging to say 15% (typical low of 8% high of 20%) daily (weekdays).

< 1c (3.1kw) average discharge, regular bursts of < 3c (9.6kw) should be no problem for the battery pack. Similarly, I don't think discharging to near-empty would cause any damage to the lithium iron phosphate packs in the Enertia, but that's a better question for a brammo rep.

Basically, if you're not abusing it, then you can assume Brammo designed the bikes to be ridden. If you do something extreme to the pack, like buy an Empulse 6.0, ride it most of the time at throttle 100% (5-8c discharge) and charge it on a 230v 70A (3c charge) tesla charger -- if such a thing were possible -- maybe your pack would have dropped down to 70% capacity by 1000 cycles instead of 80%. 1c discharge and 0.5c charge are pretty light demands on any reasonable battery pack.

[HighlanderMWC]

< 1c (3.1kw) average discharge, regular bursts of < 3c (9.6kw) should be no problem for the battery pack. Similarly, I don't think discharging to near-empty would cause any damage to the lithium iron phosphate packs in the Enertia, but that's a better question for a brammo rep.

Basically, if you're not abusing it, then you can assume Brammo designed the bikes to be ridden. If you do something extreme to the pack, like buy an Empulse 6.0, ride it most of the time at throttle 100% (5-8c discharge) and charge it on a 230v 70A (3c charge) tesla charger -- if such a thing were possible -- maybe your pack would have dropped down to 70% capacity by 1000 cycles instead of 80%. 1c discharge and 0.5c charge are pretty light demands on any reasonable battery pack.

That helps. I think the Enertia was originally limited to 7kw and the service reps now offer a tweak to the settings that looks like it might be 9.6kw (I don't recall seeing any bursts over the low 9s). When packs degrade would it show as lower voltage when fully charged?

[protomech]

< 1c (3.1kw) average discharge, regular bursts of < 3c (9.6kw) should be no problem for the battery pack. Similarly, I don't think discharging to near-empty would cause any damage to the lithium iron phosphate packs in the Enertia, but that's a better question for a brammo rep.

Basically, if you're not abusing it, then you can assume Brammo designed the bikes to be ridden. If you do something extreme to the pack, like buy an Empulse 6.0, ride it most of the time at throttle 100% (5-8c discharge) and charge it on a 230v 70A (3c charge) tesla charger -- if such a thing were possible -- maybe your pack would have dropped down to 70% capacity by 1000 cycles instead of 80%. 1c discharge and 0.5c charge are pretty light demands on any reasonable battery pack.

That helps. I think the Enertia was originally limited to 7kw and the service reps now offer a tweak to the settings that looks like it might be 9.6kw (I don't recall seeing any bursts over the low 9s). When packs degrade would it show as lower voltage when fully charged?

From what I've read, pack degradation will show up as the pack falling off in voltage more rapidly (voltage hits the lower cutoff at 25 miles instead of 30 miles, say). Full charge voltage should be the same.

[GeorgeS]

Proto,
I put together a crude 10.0 pack volume using your estimate of 1200 18650 cells.

The dimension between your legs (width)=7.7
The long diagonal dimension when viewing the pack from the side=22.4"
ht=5.6"
to do this I assume a 10% increase in each of the cells dimensions for packaging.

I also came out with of 54g for the Tesla 18650 cells by using some other data I had which is very close to the number you calculated. (However you can bet they have a new 18650 for the S that will have some improved numbers, lets not sell them short)

All in all this battery looks pretty darn good. They are quoting a 60 deg C max operating temp. Pretty amazing as that is 140 degrees F!!! We know this pack is lighter as they doubled the Enertia Plus battery's kwh with NO INCREASE in wt. We also know that they only increased the price by 1000$ so they must be making their cost bogey's.

This is very exciting news for all of us that have Empulse orders as it  means they have a battery manufacturer that can supply the Empulse battery at the technical specs and price to make this bike happen.

One thing I caught when reading the Leyden site (under power packs) was that they will use PTC's in this pack for thermal passive management!!

I'm one happy camper --GSB

[Gavin]

Sweet. Maybe the passive thermal management will keep the fan from running except at high speed or very hot days. And at high speeds you aren't going to hear the fan anyways...as for hot days, well a fan is expected then...

Too bad it isn't water cooled like the Empulse...but maybe Brammo feels the lower speed Enertia doesn't need that much cooling.

Gavin

[booeyschewy]

i'm interested to know a couple things about the batteries. Since it's the most costly thing on them, and I know that the batteries on the first hybrids ended up having a pretty short lifespan, how long is the warranty for the batteries?

This may be a dumb question, but would hot humid conditions alter their operation (like subtropical miami)?

[Brammofan]

Hey booey - welcome to the forum.

The battery (and the rest of the bike) warranty is one year, although in California, if you want to take advantage of the rebate, you have to buy a two year warranty, which is something like an extra $250.  The website mentions that extended warranties (up to three years) will be available. 

Some lifespan information can be found on the Wiki: http://www.brammoforum.com/wiki/index.php?title=FAQs

And, (there are no dumb questions), I think the batteries are essentially unaffected by humidity and temperature, although it is recommended that they be charged in temperatures under 113F and operated under temps of 104F (from the Enertia owner's manual). 

[protomech]

i'm interested to know a couple things about the batteries. Since it's the most costly thing on them, and I know that the batteries on the first hybrids ended up having a pretty short lifespan, how long is the warranty for the batteries?

The base warranty is one year. Leyden Energy claims > 1000 cycles, > 10 year lifetime (calculated) on the likely batteries in the Empulse.

Demands on Hybrid batteries are different than EV batteries. They're much smaller, and so are asked to discharge and charge at much higher rates which tends to wear the batteries more quickly. Even so, my Honda Insight had its batteries replaced at 100k miles and I expect to get another 100k out of the second pack. Toyota Prius taxis in NYC have gone 200k, 300k miles on the original batteries. Time seems to be the key concern rather than number of cycles on a properly maintained pack.

This may be a dumb question, but would hot humid conditions alter their operation (like subtropical miami)?

Humid conditions should not cause operational problems. LE claims -30°C to 60°C operating temperatures (-22F to 140F), 95% relative humidity. Regular operation at higher temperatures will likely cause the batteries to wear more quickly, for example the batteries in the Enertia 3.1 kwh are tested to 80% capacity at 2500 cycles at 23°C / 0.5C, 1500 cycles at 45°C / 0.5C.

See this thread where operation in humid weather and rain is discussed:
http://brammoforum.com/index.php?topic=161.0

[booeyschewy]

thanks for the info!

couple more questions:
1. living in miami we have significant portions of the year where daytime temps are upper 80s and 90s and a few months of solid 90s. This will put extra strain on the battery then? Is there a way to estimate or ballpark the drain this could have. This isn't that bad because in the deep south they get summer temps >100 which we don't, but I'm still curious. I don't have an air conditioned garage so... 

2. Most of my commuting is at 35-45mph in an urban environment. I take it I would get better mileage than the quoted 60/80/100 then? Or what is the quoted distance clocked at?

[protomech]

thanks for the info!

couple more questions:
1. living in miami we have significant portions of the year where daytime temps are upper 80s and 90s and a few months of solid 90s. This will put extra strain on the battery then? Is there a way to estimate or ballpark the drain this could have. This isn't that bad because in the deep south they get summer temps >100 which we don't, but I'm still curious. I don't have an air conditioned garage so...  

I don't know of any way to estimate the drain short of testing the pack or getting a chemical engineer with a deep knowledge of the cell chemistry to run a simulation. My gut (wishful?) feeling is that those temperatures are well within the claimed operating specs for the pack, and that any loss will be pretty minimal.

2. Most of my commuting is at 35-45mph in an urban environment. I take it I would get better mileage than the quoted 60/80/100 then? Or what is the quoted distance clocked at?

Brammo rates the Enertia Plus (same 6.0 kwh pack) at 80+ miles urban commuting, 60+ miles suburban commuting, 40+ miles highway commuting.

Most of the original Enertia owners are getting around 35 mile ranges at 35-45 mph speeds. That should put an Enertia Plus or Empulse 6.0 at 60-70 mile ranges at similar speeds.

Here's a spreadsheet I ripped off with calculated pack ranges (based on usage):
https://spreadsheets.google.com/ccc?key=0AubOGC_oXqHfdHN6RTVhNEl6ejR3VXBmbUstbHhweFE&hl=en&authkey=CLe-idYC

Edit: It's based on the extremely helpful logs kept by ppc750. Mm, delicious G4.