Introduction from LifeBATT UK Distributor

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MalcolmB
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Postby MalcolmB » Wed Oct 17, 2007 9:27 pm

Maybe this will help sort things out: http://batteryuniversity.com/partone-16a.htm
:)

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ChrisB
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Postby ChrisB » Wed Oct 17, 2007 9:51 pm

mmmmm was waiting for this site to pop up on the thread :lol:

Right..........

At 1C, a 10Ah battery discharges at the nominal rating of 10A in less than one hour. At 0.1C, the same battery discharges at 1A for roughly 10 hours.


Well thats not right , surely :?: , you would expect if you discharged a 10Ah C1 battery at 1amp it would supply that for way in excess of 10hrs

Take say a Rolls Deep cycle unit ...........

CAPACITY AT THE 20 HOUR RATE 1.265 SP. GR. 305 15.3
CAPACITY AT THE 15 HOUR RATE 1.265 SP. GR. 287 19.1
CAPACITY AT THE 12 HOUR RATE 1.265 SP. GR. 271 22.6
CAPACITY AT THE 10 HOUR RATE 1.265 SP. GR. 259 25.9
CAPACITY AT THE 8 HOUR RATE 1.265 SP. GR. 244 30.5
CAPACITY AT THE 6 HOUR RATE 1.265 SP. GR. 226 37.6
CAPACITY AT THE 5 HOUR RATE 1.265 SP. GR. 214 43
CAPACITY AT THE 4 HOUR RATE 1.265 SP. GR. 198 50
CAPACITY AT THE 3 HOUR RATE 1.265 SP. GR. 180 60
CAPACITY AT THE 2 HOUR RATE 1.265 SP. GR. 156 78
CAPACITY AT THE 1 HOUR RATE 1.265 SP. GR. 110 110


The last two figures are Ah cap and discharge current .

So it starts out at the 20hr rate as a 305Ah battery but by the time you discharge it at the 1hr rate its now only a 110ah battery so how does that figure with the 10amps for an hour or 1amp for 10 hrs ???

So if we take the 10Ah battery from the battery university site how can a battery rated at 10Ah for 1 hr be the same battery rated at 10Ah discharged at 1A for 10 hrs ?? dont make sence ???

This is going to make for an interesting thread me thinks.

ChrisB
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MalcolmB
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Postby MalcolmB » Wed Oct 17, 2007 11:11 pm

Where's Paul when you need him?

I'm not trying to teach anyone to suck eggs, but this is a useful way to get things straight in my own head.

My lead acid batteries have a label rating of 26Ah, but if you read the manufacturer's data sheet you find that this capacity is actually specified over a 10-hour period, so the only way you could actually get this much energy out of the battery would be to discharge it at 2.6 amps over 10 hours, which is not a lot of use to me. This is known as the C10 rate, in other words the nominal capacity (26Ah) divided by 10 hours.

Because no battery is perfect, the faster you discharge it, the less energy you can get out of it. So if I discharge one of my batteries at the 1C rate (in one hour, which is more likely) I only get 19.6 amp hours from it, according to the manufacturer's data sheet, which matches up well with my own experience.

Unlike lead acid batteries, the new lithium phosphate batteries can supply high currents without a serious reduction in capacity, so a battery that is rated at 10Ah can actually supply a current of 10C, in other words ten times its nominal rating (100 amps) and still actually deliver close to 10Ah. (Note this is 10C, ten times it's rated current, as opposed to C10, one tenth of its rated current).

The battery university example is based on theoretical capacity, without taking into account the Peukert effect, which it describes later on.

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Postby ChopperMan » Thu Oct 18, 2007 7:15 am

Thank you for the explanation Malcolm, this is my understanding too.

Paul, when I read your post last night it was far to late for me and I'll admit I was completely confused. Then at 4am this morning I realised, I'm talking about Apples, and your talking about Oranges :)

The experiment below was conducted i believe by the Taiwanese factory engineers:

"A 24V/40Ah LiFePO4 battery may look like the SLA (Sealed Lead Acid) 24V/ 50Ah battery, but we have installed it on an electric scooter and tested it on the Dyno test equipment. The 40Ah X 48V LiFePO4 battery runs the range of 106 miles, and the 50Ah X 48V SLA battery only runs about 34 miles. It is almost 3 times the range of the SLA battery. However the discharging rates are different. The LiFePO4 battery retains more than 90% Amp Hour in different discharging current, while the SLA will drop very soon if we are continuously discharging in high current rate (for example the100A discharging will cause the 50Ah SLA to become 20Ah capability). This might explain why the 40Ah LiFePO4 battery will run 3 times the range of the 50Ah SLA battery."

My own experience of LifePO4 chemistry batteries is very similar. Voltage sag is far less noticeable and my chopper, which has no peddles, would get 10 miles on 36V 18Ah Europa Gell Cells, when the pack was run flat. On a 36V 20AH LifePO4 pack, I have done 20 miles with no decernable drop in power, (which is explained by the flat(ish) discharge curve) and the CycleAnalylist recorded 14Ah used. When you consider that a new LifePO4 pack will discharge close to 95% of it's rated capacity for the first couple of hundred charges (85% at 1,500 cycles) you can extrapolating that I should have a range of approx 26 miles.

I hope this helps.

Ian

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LiFeBATT NEWS FLASH

Postby ChopperMan » Thu Oct 18, 2007 10:44 am


NEWS FLASH Thursday 17th October 2007


Our initial introduction of the LiFeBATT 36V 20Ah pack has met with critical review of the weight due to the design of the moulded modular cases. For this reason, we are re-tooling the cases on this pack to archive a lighter weight, and also simplify the Battery Management System. Delivery will now be re-scheduled for January 2008 for all packs.

As a result of this delay in product release - LiFeBATT will offer our individual cells only to the market starting in late November 2007.

These will be available in limited numbers, so please reserve your cells early, the price will be announced shortly.

Kind regards,

Ian

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ChrisB
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Postby ChrisB » Thu Oct 18, 2007 5:33 pm

Its ok folks its a speed reading error on my behalf :oops: :roll:

Thanks to Malcom who put it all into perspective.

Right I can now see where I'm getting confused , Ians talking about 10C or the number before the C , where as I'm talking about the C10 or the letter before the number :oops:

Well of course its all going to be odd and not right as we are both talking about the oppersite ends of the scale :lol:

Durrrrrrrrr , my fault for speed reading in the first place.

So if I'm right the a 12v 10Ah lifebatt will .......... supply a continuous discharge of 120A for a total of 1 hr and then be flat then ??

Thats a heck of a discharge !!! about 1.4kwh or 1.4 kw for an hour :shock: seems quite a claim :? and it dosnt effect battery life or general performance ???

ChrisB
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MalcolmB
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Postby MalcolmB » Thu Oct 18, 2007 7:41 pm

its a speed reading error on my behalf

Been there, done that :D The problem with web-based communication is it tends to bypass the normal self-censoring and proofreading software.

Yes, the lithium phosphate chemistries seem to be very robust and can deliver impressive currents with little reduction in capacity. Detailed specs for the LifeBatt cells don't seem to be available yet, but the radio control community are reporting excellent results with the A123 cells, which are based on a similar chemistry. They tend to abuse their cells, running helicopters and heavy models at high currents, but are still getting several hundred cycles from them at discharge rates of 20C and higher, which means they're pulling 60A from cells weighing less than 100 grams. At present the only real option for getting hold of A123 cells is by buying DeWalt 36V battery packs on Ebay and stripping out the cells, but the cells are only 2.3Ah and you have to build your own BMS if you want to use them in any other configuration.

Discharged at a rate of 1C the A123 cells are reported to deliver around 1500 full discharge cycles before capacity is reduced to 85%, and I'd expect the LifeBatt cells to have similar performance. At the 10C rate the capacity will be slightly reduced, as will cycle life, but this chemistry is the best available at the moment for high discharge applications.

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ChrisB
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Postby ChrisB » Thu Oct 18, 2007 10:25 pm

MalcolmB wrote:
its a speed reading error on my behalf

Been there, done that :D The problem with web-based communication is it tends to bypass the normal self-censoring and proofreading software.


So embarrassing when this happens :oops: , trouble is I look after a couple of forums and tend to have to flit about and its so easy to miss the obviouse :oops:
MalcolmB wrote:Yes, the lithium phosphate chemistries seem to be very robust and can deliver impressive currents with little reduction in capacity. Detailed specs for the LifeBatt cells don't seem to be available yet, but the radio control community are reporting excellent results with the A123 cells, which are based on a similar chemistry. They tend to abuse their cells, running helicopters and heavy models at high currents, but are still getting several hundred cycles from them at discharge rates of 20C and higher, which means they're pulling 60A from cells weighing less than 100 grams. At present the only real option for getting hold of A123 cells is by buying DeWalt 36V battery packs on Ebay and stripping out the cells, but the cells are only 2.3Ah and you have to build your own BMS if you want to use them in any other configuration.

Discharged at a rate of 1C the A123 cells are reported to deliver around 1500 full discharge cycles before capacity is reduced to 85%, and I'd expect the LifeBatt cells to have similar performance. At the 10C rate the capacity will be slightly reduced, as will cycle life, but this chemistry is the best available at the moment for high discharge applications.


Well if they stand up the claims then they do sound very interesting, I'd like to see some better test figure over a range of tests mind you before taking the plunge at that price.
The nearest stuff I can think of so far that are similar are the thundersky Li-ions.

My problem would be needing something like 162 volts nominal pack voltage for the berlingo, as for Ah well the nicads are 100Ah C3 from memory not sure what that would transpire to with a LifeBatt pack, may be ChopperMan can suggest ??


ChrisB
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ChopperMan
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Postby ChopperMan » Fri Oct 19, 2007 7:34 am

NEWS FLASH Friday 18th October 2007

Individual Cells now available in limited numbers. Click here http://www.lifebatt.co.uk/order.htm to place your order now to avoid disappointment.

Cost per 3.3V 10Ah cell is £32.00 each. This excludes BMS and charger, but includes delivery and VAT.

Any questions please call 0044 (0) 1268 774415

Kind regards,

Ian

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ChrisB
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Postby ChrisB » Wed Oct 31, 2007 11:07 pm

LifeBATT and the Berlingo is now HERE

ChrisB
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