| Good point. Where these cells shine is EVs. So a wash for our use, but a wash with the perks of minimal voltage sag under heavy load, small voltage swing through discharge, high charge acceptance, no corrosion or spilled acid, and no need to water.
Bob --- On Wed, 2/20/13, Myles Twete <matwete@comcast.net> wrote:
From: Myles Twete <matwete@comcast.net>
Subject: RE: [Electric Boats] Re: Comparing FLA to LiFePO4.
To: electricboats@yahoogroups.com
Date: Wednesday, February 20, 2013, 9:37 PM
Sure, but the devil's in the details. You've used cycle life as part of the comparison, so let's state it: You're banking on 2000 cycles in claiming 4x the cycle life as Lead. While that's great on paper, and in practice probably achievable, here's your question: How many years will you be using these batteries to come close to 2000 charge cycles? In my boat's case, I can't imagine I do more than 50 charge cycles in 1 year given I only get out on the water about 2-4 times per month. So 2000 cycles is 40 years of use…not exactly a life that I'd expect the batteries (any batteries except for Nickel-Iron) to last. And that's the problem I have with bringing cycle life into the argument. For a commuter car, sure, but for a pleasure boat, not. So based on your numbers, ignoring cycle life, it's kind of a wash between lead and today's price for lithium. Unless you're like me and you buy "used" T105 cells for $20 each that have nominally half the rated capacity. In this case, $120 pack for 100a-h. Having said that, I am seriously considering adding lithium to my boat… -Myles Twete, Portland, Or. www.evalbum.com/492 From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Robert Lemke
Sent: Wednesday, February 20, 2013 9:10 PM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Re: Comparing FLA to LiFePO4. Carter, Until the prices came down, lead was the cheapest but not any longer. The best price on a 220 a-hr 6 volt battery is $100, so $400 for a 440 a-hr 12 volt bank. Since it has a much higher Peukert effect, that 440 a-hr bank drops to 350 a-hr and since you want 500 cycles you won't go past 50% DOD, so for $400 you have a 175 a-hr battery that if cared for will cycle 500 times. (4) 260 a-hr LiFePO4 cost $820, and as tested at that same 20 hour rate that lead gets their capacity numbers, will produce 390 a-hr. At 80% DOD that works out to a usable 312 a-hr. This is almost twice the usable a-hr capacity of the (4) golf cart batteries at twice the price, so it sounds like a wash, right? Not quite, as the cycle life of the LiFePO4 is 4 times that of lead, so basically in the long run 1/4 the price of lead with all the perks I mentioned before. I always strive to get the most bang for my buck, and these cells deliver that and then some. Bob
--- On Wed, 2/20/13, Carter Quillen <twowheelinguy@yahoo.com> wrote:
From: Carter Quillen <twowheelinguy@yahoo.com>
Subject: Re: [Electric Boats] Re: Comparing FLA to LiFePO4.
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Date: Wednesday, February 20, 2013, 8:48 PM
Please don't interpret my argument for flooded lead acid as an enthusiastic endorsement of the technology, my experience has been that it really does kind of suck on many levels and has been a big disappointment from a performance standpoint. But if you don't have 8k for your battery pack, a million golf carts is a testament to the fact that a $1000 bucks will get you there. Also, with the high cost of Lithium, the overall life cycle cost is really too close to call definatively at this point with a too many variables. If you have the cash, who wouldn't rather drive the Testerosa? (Even if it does cost more). But the technology is still a bit fluid with lots of "claims" of superior performance that don't always pan out. Note that Boeing just switched from Lithium to NiCad after a very expensive failure of the Lithium technology in thier Dreamliner. It's good to hear that your experience with LeFePO4 was very positive and that's definitely the kind of feedback the industry needs. Lithium chemistry is probably the future but in the mean time, some of us are still stuck with what we can afford and my argument is that lead is not quite dead, yet! From: Robert Lemke <robert-lemke@att.net>
To: electricboats@yahoogroups.com
Sent: Wednesday, February 20, 2013 10:49 PM
Subject: Re: [Electric Boats] Re: Comparing FLA to LiFePO4. Since this is being kicked around I'll throw in my $0.02 and isn't worth that. I recently went the LiFePO4 route and from my tests I'll never go back to lead. The first thing I discovered was how conservative the a-hr rating is in real world usage. Over the years I grew accustomed to the 20 hour rate of lead acid. I purchased (8) 100 a-hr LiFePO4 cells and found that at that easy 20 hour rate they should have been rated 150 a-hr. Pulling 100 amps for a 1 hour rate they still managed 125 a-hr. That just doesn't happen with lead. A 60 lb group 27 battery gives my electric kayak a 16~18 nm range. The same weight of LiFePO4 gives me 80 nm. Fast charge acceptance is another perk, as I can pull into a marina bar/restaurant and my 8 lb, 50 amp charger will refuel the battery in the time it takes to have lunch and drinks. BTW, the charger has a lithium profile and was less than $200. Another positive is very small voltage sag under heavy draw and not much voltage swing during discharge. Combine all this with 2000+ cycles and electron energy storage doesn't get cheaper than this. Lead is Dead. Bob aka "deckofficer" --- On Wed, 2/20/13, Eric <ewdysar@yahoo.com> wrote:
From: Eric <ewdysar@yahoo.com>
Subject: [Electric Boats] Re: Comparing FLA to LiFePO4.
To: electricboats@yahoogroups.com
Date: Wednesday, February 20, 2013, 6:09 PM
Hi Carter, I know that your plan is largely solar and you've got generator and a full diesel driveline as backups, but here's some battery only performance data. So your eight T-125 (530 lbs) have a 20hr rating of 12kWh, but at a 25A load, the total capacity drops to 10kWh (that's the Peukert Effect kicking in). Put the load up to 50A and the total capacity is 8.4kWh. And at 80A (you said earlier that 80A = 3.8kts or 4.4mph), the total rated capacity falls to 7.5kWh, a loss of 37% to Peukert's effect. Limit your discharge to 60% of total capacity and you batteries will last 1.12 hours at 80A draw. At 3.8kts that works out to 4.25nm range on a full charge of your batteries. The Balqon pack with a 20hr rated capacity that is 67% higher than your FLA pack seems like a luxury, but let's check the same loads. Balqon doesn't list the weight, but it should be right around 500 lbs like your current pack. Starting with a total rated capacity of 20kWh, at 25A the rated capacity drops to 19.86kWh, very close to the 20 hour rated capacity. At 50A, the rated capacity is still 19.45kWh. Finally at 80A, the Balqon pack rates to 19.2kWh, losing only 4% to Peukert's Effect. Since LiFePO4 batteries can be consistently discharged to 80%, you could run the motor at 80A for 3.83 hours for a range of 14.5nm. That's 3.4 times the FLA range at 3.8kts under batteries alone. So at the cash register, the Balqon battery looks 8 times more expensive than the T-125s. But if you consider the increased range without any weight, the Balqon pack is only 2.3 times the cost of the T-125s. Trojan says that the T-125 is good for 650 cycles. At 2000 cycles for the Balqon, you would have to buy 3 sets of Trojans for the same number of cycles. If you factor in the full life span in cycles, the Balqon works out to 12% cheaper per mile than 3 sets of T-125s. I know that this doesn't change the fact that the original investment takes a bigger wallet, but that could ultimately save you money in the long run. I know that you didn't ask for this, but I like running the numbers, and it's been a while since anyone has done the math in front of the group. I figure that this exercise might be helpful for new mebers here. Fair winds, Eric Marina del Rey, CA --- In electricboats@yahoogroups.com, Carter Quillen <twowheelinguy@...> wrote: > > Followed the link to check it out. Nice battery and made in America, (mostly), to boot. >  > Wish I had an extra $8 grande, I'd buy one tomorrow. Puts my 8 pack of Trojan T-125s to shame but since I only paid about a thousands bucks for an 8 kW pack I don't feel that bad. Looking forward to the day when you'll be able to buy Lithium for the cost of lead and it's coming. In mean time, I'll have to be content with my horse and buggy and wait for the model 'T's of batteries to hit the market. >  > Carter > www.archemedesproject.blogspot.com > > From: James Sizemore <james@...> > To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com> > Cc: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com> > Sent: Wednesday, February 20, 2013 7:24 PM > Subject: Re: [Electric Boats] Re: Converting a small trimaran to electric drive > > > > Here is a 20kw lithium pack with bms and case for the below 8000, total package. > http://www.balqon.com/store.php#!/~/product/category=2897128&id=12658249 > ------------------------------------ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/electricboats/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/electricboats/join (Yahoo! ID required) <*> To change settings via email: electricboats-digest@yahoogroups.com electricboats-fullfeatured@yahoogroups.com <*> To unsubscribe from this group, send an email to: electricboats-unsubscribe@yahoogroups.com <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/ |
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