Thin plate lead/acid tech
Reasonable options is what these pages are all about!
Including the wit and humor from certain Commandereers.
Next generation batteries are extremely attractive and expensive.
And I believe that Nigel Calder article is almost 5 years old.
So maybe there's been some acid gone under the plates by now.
Stamped out paper-thin (less than 1/64 inch and 99 44/100 percent pure virgin lead) pages does sound like an advertising gimmick, but maybe there's been enough time to get the bugs out of this FOURTH type of lead/acid battery.
By necessity thin plates would have to be supported by something inside like glass mat,
So I assume all the TPPL have to be AGM. Don't think that Gels are seriously considered anymore.
This tricky new product has to be linked with sophisticated electronics.
And the way I read it, AGM batteries, as far as cruisers are concerned, don't work well off grid.
They're not foolproof even with expensive controllers and cruising conditions.
So, the new bat will bring us another set of problems, large and small, that have to be worked with and worked out? - or is the TPPL the maintenance-free answer? Will they vent, for instance? Can they take any neglect?
Are we still waiting to see?
Are there 3 happy sailors out there that have 3 years of cruising with these babies?
At some point I'll compare costs of GCs with TPPLs.
The battery mounting system will still need a leakproof tray for the battery bank.
And a waterproof lid to insure against shorting and dollops of water coming through the companionway!
And I agree with you that NIGEL CALDER is the most trustworthy guru we have on marine matters. He is faultless so far as I can read into his M&EM tome on marine esoterica. I have his cruising volume as well. Will read anything that comes up Calder publishes in the media. We are lucky indeed to have him as the authority we can go to!:cool:
From Yahoo's Electric Boat Forum
Hey guys, I ran across this on Yahoo's very active Electric Boats Group. Posted at the beginning of April 2012. "Eric" seems to be THE guy on the forum.
This link is below, but I also found it rather useful:
http://www.vonwentzel.net/Battery/00.Glossary/
************************************************** *******First of all, lithium batteries should never be drained to 0%, using my
Thundersky LiFePO4 prismatic cells as an example, a single event of dropping the
cell voltage to 2V can ruin that 3.2V cell forever. This intolerance to
complete discharge is one of the drawbacks to lithium cells in EVs and electric
boats. That is also one of the reasons that many people run Battery Managemnet
Systems (BMS) that will prevent over and under-voltage situations by
disconnecting the batteries before they are damaged.
So for our purposes, the following dicharge levels are what most of the members
here agree provide an acceptable balance of usable capacity and battery life.
Flooded batteries (FLA) can be regularly discharged to 60% depth of dicharge
(DoD).
AGM batteries are good to 70% DoD.
Lithium cells are good to 80% DoD.
Like James said, you also need to consider how fast you drain your battery. We
all know that a battery that will deliver 200Ah at 10A (20 hour rating) will
deliver less at higher discharge rates. You can see that in the manufacturer's
spec sheets. Using the Trojan SCS225 12V FLA battery's specs as an example,
it's 20 hour rating is is 216Ah, at 25A it's down to 225 minutes or 94Ah and at
75A the battery capacity to 100% discharge is 57 minutes or less than 72Ah.
http://www.trojanbattery.com/Products/SCS22512V.aspx
My first post here about different battey types and Peukert's Effect was back in
Nov 2009 (post # 12716), but I've refined the explanation each time it comes up.
Here's the latest version "Choosing a battery type" from Jan 26 , 2012 (post
#20750)
===================================
Choosing a battery type for your electric boat conversion can be difficult.
Here's some information that is generally accepted on this board. The product
specs from battery vendors don't tell the whole story.
FLA (flooded lead acid) batteries are typically run to about a 60% DoD (depth of
discharge). Some people go deeper, but many consider this depth to be a good
compromise between energy delivered and maintaining a long life, measured in
charge cycles.
AGM (absorbed glass mat) batteries can be discharged to the 70-80% range. I
generally consider a 70% discharge for AGM systems. Both FLA and AGM weigh about
the same for the same rated capacity.
Lithium Batteries (LiFePO4) can be discharged even deeper, for range estimates I
use 80% DoD to keep a small safety reserve. LiFePO4 batteries are about 50% the
weight of lead/acid batteries for the same rated capacity.
Then there is a trait called the Peukert Effect, this describes a battery's
decreased ability to deliver energy at higher amp loads. I won't go into the
math here, but that loss is predictable through Peukert's equations. Brace
yourselves; it's going to get technical for a while.
In fact, the concept was known for many years before Peukert was able to
quantify the relationship between the load and capacity lost. Here's a link to a
page that explains the Peukert Effect in greater detail:
http://www.smartgauge.co.uk/peukert2.html
The content can be a little difficult to work through, but it is correct. There
are additional pages that provide validation of their version of the formula,
where the results can be verified against the published specs of almost any
battery. If you don't want to work through all of the math in the middle of the
page, the second to the last paragraph refers to how different battery types
have different Peukert's Exponenets and what that can mean.
If you can accept that different batteries can have different Peukert Exponents
depending on how they are made, then the following link shows graphically how a
different Peukert Exponent affects the available capacity of different
batteries. Look about halfway down the page, in the section labeled "The Peukert
Effect":
http://www.vonwentzel.net/Battery/00.Glossary/
Finally, while few manufacturers publish their specific Peukert Exponents, some
do and some other numbers have been published for common batteries. Peukert
Exponents are typically calculated through empirically measured capacity at
different loads. Here are a few examples (values closer to 1.0 are better):
Trojan T-105 = 1.25
US Battery 2200 = 1.20
Optima 750S = 1.109
Thundersky LiFePO4 = 1.03
So what does this mean in the real world? Let's pick a battery bank size of
10kWh (208Ah @ 48V) and a constant load of 2500W (52A @ 48V). That will drive
most of our boats to somewhere between 4 and 5kts, your results will vary.
The simple math would indicate that there are 4 hours of capacity at that
discharge rate in the bank to 100% DoD, so FLA batteries like T-105s would have
60% of 4 hours or 2.4 hours of usable range. Likewise AGM would be 2.8 hours and
Lithium would have 3.2 hours of usable range. But this is where Peukert's effect
raises its ugly head.
FLA with PE of 1.25 – 10kWh to 60% DoD at 2500W = 1.60 hours (that's a loss of
33% to Peukert's Effect)
AGM with PE of 1.1 – 10kWh to 70% DoD at 2500W = 2.38 hours (15% lost to
Peukert's Effect)
LiFePO4 with PE 0f 1.03 – 10kWh to 80% DoD at 2500W = 3.05 hours (less than 5%
loss)
You can see that AGM have almost 50% more usable range than T-105s for this size
battery bank at this load. Reducing the load (slowing down) reduces the effect
and speeding up makes it worse. Even though quality AGM are about twice the cost
of T-105s, the extra usable range makes them a very good alternative. Add in the
much lower self discharge rate so that constant maintenance charging is not
required and they look even better. People also recognize that AGMs seem to last
longer in the real world and now the AGMs are cheaper in the long run. If weight
is a concern, then LiFePO4 is the way to go. The high price per Ah can be
intimidating, but you can reduce the Ah and achieve the same range, saving money
and even more weight. Let's do the math for a battery pack that has a 2.5 hour
range at 2500W.
FLA – 14.25kWh to 60% DoD at 2500W = 2.5 hours = 633 lbs, cost about $1500
AGM – 10.5kWh to 70% DoD at 2500W = 2.5 hours = 520 lbs, cost about $2500
LiFePO4 – 8.25kWh to 80% DoD at 2500W = 2.5 hours = 200 lbs, cost about $3500
So now the lithiums are only 2.3 times the cost of T-105s but they are less than
1/3 the weight for the same range at this load.
So for most boaters, I recommend AGMs as a good balance of price to range.
So the bottom line is: it's your money, your boat and you know how you use it.
You get to figure out your priorities and pick the storage system that best fits
your particular needs and constraints.
========================================
So you can see in the last table that 8.25kWh of LiFePO4 batteries
delivers the same usable capacity as 14.25 kWh of regular flooded batteries at a
2500W load.
Notice that I'm not talking in Amps, Ah or Voltages any more. This math works
for any voltage, 12V, 24V, 36V, 48V, 144V, it doesn't matter. Even I was
surprised to find that out. Since the boats in this group are a bunch of
different voltages, it is easier to compare them in Watts because Watts are a
more consistant measure.
Fair winds,
Eric
1964 Bermuda 30 ketch, 5.5kW Propulsion Marine drive, 8 kWh Lithium batteries
Marina del Rey, CA