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Old 05-05-2009, 14:00   #16
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Hiracer-
Just because a battery CAN absorb at a 400AH rate, doesn't mean that's how to design a system around it. Consider that when that same battery is only down 25%, it will be able to absorb the full output from a 100A alternator correspondingly faster as well. So even though it is being fed through a straw (so to speak) it is still capable of being recharged faster, under all circumstances, and simply making optimum use of whatever size alternator is there to feed it.

If your speedometer says 180mph--that doesn't mean you have to drive at that speed.
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Old 05-05-2009, 16:16   #17
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Lithium Phosphate batteries are being used by most of the electric car builders now. I am reading about prices ~$1.10 per ah, for the standard 3.6 volt cell. So, that makes them $880 for a 12v 200ah battery. That does not include shipping from China (where much of these are coming from) nor a battery management system or charger. These are spec'ed at 2000 cycles at 80% discharge, and 3000 at 70%. They are also much less affected by the Perkert effect. The numbers I have seen seem to indicate at most a 20% reduction in capacity due to high amp discharge.

High end AGM batteries seem to last 400 cycles at 80%, and cost around $400 + shipping. Compare this to the LIFEPO4 stats above. In my mind, this means that we are should soon see these marketed to the marine industry.

Chris
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Old 05-05-2009, 16:46   #18
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Dunno Chris. The LiPho batteries may be "twice the price but half the cost" but you are omitting a significant extra cost, they need a smarter charge controller.

The Chinese government has made the committment to be a world leader in electric cars, mainly because most of their drivers use a car for less than 40 miles round-trip per day. (In the US the daily cycle is larger and electric cars can't accomodate it.) If they push, they can easily build the new chargers to a commodity price point and then they become possible for the marine industry. But right now...Asking folks to spend twice the money up front for a battery, and perhaps 50% more again to replace their regulator with a smarter one at the same time, would just push things beyond competitive pricing.

And that's assuming the Chinese can demonstrate to the world that they've finally separated their battery manufacturing from their fireworks companies. They've earned an ugly reputation for LiOn battery fires and poor qc. It will take some years to live that down.
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Old 05-05-2009, 17:37   #19
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Hello;

I did mention the need for a BMS and charger. We never mention the cost of a good regulator or alternator when talking about AGM batteries, either. As I understand it, a A BMS needs to keep the individual cells from over or under-charging, as well as equalizing the cells, by either bleed off, or power transfer.

The Lithium Phosphate chemistry supposedly takes care of the fire and explosion issue. I have yet not read of electric cars exploding, and they are using high voltage systems where the issue is more critical.

Concerning charge capacity, these cells all seem to take 3-4c, that is 3-4x their AH capacity.

The Chinese are not the only ones making LIFEPO4 batteries, just it seems the cheapest.


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Dunno Chris. The LiPho batteries may be "twice the price but half the cost" but you are omitting a significant extra cost, they need a smarter charge controller.

The Chinese government has made the committment to be a world leader in electric cars, mainly because most of their drivers use a car for less than 40 miles round-trip per day. (In the US the daily cycle is larger and electric cars can't accomodate it.) If they push, they can easily build the new chargers to a commodity price point and then they become possible for the marine industry. But right now...Asking folks to spend twice the money up front for a battery, and perhaps 50% more again to replace their regulator with a smarter one at the same time, would just push things beyond competitive pricing.

And that's assuming the Chinese can demonstrate to the world that they've finally separated their battery manufacturing from their fireworks companies. They've earned an ugly reputation for LiOn battery fires and poor qc. It will take some years to live that down.
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Old 05-05-2009, 21:30   #20
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Chris-
"We never mention the cost of a good regulator or alternator when talking about AGM batteries, either. " Yes, but since many sailors are just using a cheap automotive style alternator or one with a similarly cheap external regulator--that's a given. With fancy batteries you usually need a more esoteric charging system that does not charge them at all until they drop to a set point (i.e. 40-88%) and then won't recharge them past another set point (85-90%) and each of the car makers is using different logic and different batteries to attain their goals.

Haven't heard of any hybrid power packs causing explosions all by themselves--yet. But there are still few of them out there. How long did it take before we heard reports of cell phones and computers combusting? And how much longer did it take before anyone pinpointed the problems?

They can tell me the new technology is safe all they want, but if it says "Made in China" I know it is still produced under a government that has quite literally encouraged and rewarded counterfeiting and ignored the general concepts fo safety and liability. Except when they put on a show trial and send one boss who didn't pay off the right people to the gallows. I know, things are changing in China. Once they go five years without a massive counterfeiting or toxin scandal, I'll ask Michelin to give them another star. So to speak.

After all, who would have thought wallboard could be a land mine? Only form China. (Sigh.)
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Old 11-05-2009, 14:23   #21
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Hiracer-
Just because a battery CAN absorb at a 400AH rate, doesn't mean that's how to design a system around it. Consider that when that same battery is only down 25%, it will be able to absorb the full output from a 100A alternator correspondingly faster as well. So even though it is being fed through a straw (so to speak) it is still capable of being recharged faster, under all circumstances, and simply making optimum use of whatever size alternator is there to feed it.
Agreed. And that goes to the heart of the paradigm shift. In the past, the battery acceptance rate has been the limiter. With these new batteries, now it's the alternator.
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Old 12-05-2009, 08:55   #22
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A quick question about Ah. Is the Ah rating on a string of batteries multiplied by the number of batteries? IF you have 4 210ah batteries do you actualy have 840Ah's total? I've gotten conflicting answers.

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Steve
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Old 12-05-2009, 09:38   #23
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Connecting batteries in series increases the voltage, connecting them in parallel increases the amp hours. So, if you put two 6 volt 200 aH batteries in series, you would end up with 12 volts and 200 aH. If you put two 12 volt 200 aH batteries in parallel you would end up with 12 volts and 400 aH. Sooo, you could connect 2 6 volt 400 aH batteries in series to get 12 volt 400 aH, you could then repeat that with 2 more six volt batteries connected in series to get another bank of 12 volt 400 aH. You could then connect these two sets together in parallel and get 12 volts at 800aH.
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Old 12-05-2009, 09:55   #24
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If all the batteries are in parallel then the Ah's is the total of the individual batteries. For example a group of 4 batteries of 12 Volts and 105 Ah's each would be 12 Volts and 420 Ah's in total.
However, if one was using four 6 Volt batteries of 110 Ah's wired in series pairs to get 12 Volts per pair the output would be 12 Volts and 220 Ah's.
The Amp-hours for identical series connected battaries is just the Ah of one battery but the voltage is the sum of the total. So two 6 Volt batteries in series yields 12 Volts but the Amp-hours is just the rating of the weakest battery. (Which is the reason that one should not mix batteries of different ratings or age or type)
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Old 12-05-2009, 09:57   #25
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Wow, two almost idential answers at the same time.
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Old 19-05-2009, 14:41   #26
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Thumbs up Valence Lithium Iron Magnesium Phosphate (LiFeMgPO4) Battery Modules

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High end AGM batteries seem to last 400 cycles at 80%, and cost around $400 + shipping. Compare this to the LIFEPO4 stats above. In my mind, this means that we are should soon see these marketed to the marine industry.

Chris
Valence lithium batteries are being marketed to traditional lead-acid battery applications. As expected, since lithium batteries have lower internal resistance, they claim in their lead-acid comparison that they don't require as high an amp-hour rating to deliver the same energy as a lead-acid battery.

Compared to a same-size lead-acid battery, they claim:
  • 33% lighter with twice the run-time
  • Longer shelf life and faster recharge time
  • Smart battery monitoring and internal cell balancing
  • No sudden death
  • State of health monitoring
I have not seen a price comparison.

They claim thousands of cycles at 100% depth of discharge in their XP Lithium Iron Magnesium Phosphate (LiFeMgPO4) Battery Modules data sheet.
Valence’s U-Charge® Power System family of products has now been installed in more than one hundred applications since it was launched in 2006, offering proven performance. U-Charge® family has now found its way into an array of electric vehicle applications such as cars, trucks, vans, buses, scooters and boats.
Offering excellent cycle life of 3-4 times that of lithium cobalt U-Charge® battery modules are 33% lighter than their lead acid equivalent batteries. U-Charge® also offers twice the run-time of lead acid with deep depth of discharge cycling.
Valence also claims to be working with marine and boat manufacturers to develop lithium iron magnesium phosphate energy storage solutions as an alternative to internal combustion (IC) engines and lead acid replacement.
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Old 19-05-2009, 16:09   #27
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Yeah but do a search on it and you find nothing. No one is selling them to the consumer. Maybe larger companies but not u or I.
So for now, they remain future technology.
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Old 19-05-2009, 16:30   #28
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I posted this in another thread, but it is relivant here..

I have ordered some LIFEPO4 cells to take a look at this new technology. The order is for eight 40ah cells, to make up a 24v 40ah pack. This will hopefully be used to power a Torqueedo motor, which I recently purchased. This pack will have 4x the capacity of the battery that shipped with the unit. I stil need to source a charger and the Battery Management electronics, and the cells won't be here for at least six weeks.

The cells are from Sky Energy, and top off at 3.6 volts at full charge, which would give a 4 cell battery the 14.4 volts at ful charge when configued to be a 12v battery. There are other cells, Thundersky, which have a higher final voltage of 4.2, which might not work well for a 12v configuration. The reason I mention this is that there are different parameters for the cells, just like wet, agm and gel cells have different parameters. It seems that there are different ways of cooking these up, or perhaps different design criteria.

I have read that the Perkert effect is much less of an issue with these cells, so the calculations on battery size would be smaller than when using the currently used battery cells such as wet or AGM. They do not tolorate full discharge however, so a system that provides cuttoff voltage, I have seen a figure of 2.0v per cell, is needed,
and monitored at the cell level.

Chris


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Old 19-05-2009, 16:37   #29
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<snip>
I have read that the Perkert effect is much less of an issue with these cells, so the calculations on battery size would be smaller than when using the currently used battery cells such as wet or AGM. They do not tolorate full discharge however, so a system that provides cuttoff voltage, I have seen a figure of 2.0v per cell, is needed, and monitored at the cell level.
A "concise" explanation of the Peukert Effect: SmartGauge Electronics - Peukert in depth - Advanced maths

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Old 20-05-2009, 10:29   #30
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Valence lithium batteries - only large sales

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Yeah but do a search on it and you find nothing. No one is selling them to the consumer. Maybe larger companies but not u or I.
So for now, they remain future technology.
You are correct; I called them in Texas yesterday, and they told me that they only sell business-to-business: "That is our current business model." They will also contemplate very large orders to end users, from which I inferred that you would have to be powering a fleet.
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