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Thursday, January 12, 2012

How Much Do You Have In The Bank? - Part 1

Batteries. We all need them. We all want more capacity. I mean, the whole idea of RVing is to take the luxuries and necessities of home on the road with us. Comfort is a GOOD thing. So is convenience.

Lithium Ion Latop Battery, Cooking
Batteries have been around a LONG time.The technology hasn't changed all that much in hundreds of years. A bit of lead, a bit of acid and behold, a battery. Yes, they've gotten marginally better in the intervening years, but there hasn't been a great leap in that technology for quite a while. We did have Ni-Cd's then NiMh, both had their advantages and disadvantages. (Anyone remember battery "memory?") Well, there is something relatively new afoot in the battery industry. Lithium Ion chemistry has taken most other types out of the mix when it comes to small electronics (cell phones, laptops, etc.) The problem is the basic Lithium Ion chemistry can go into something called "thermal runaway" it doesn't happen often, but when it does it can be catastrophic.

Imagine having that happen near you propane tank!

3.2V LiFeP03 Cell
There is a fix. A new chemistry. Still based on Lithium Ion technology, but MUCH more stable. Lithium Phosphate (LiFePO4). These have all the advantages of Lithium Ion technology, but won't meltdown like a bad nuclear reactor. (Two and Three Quarter Mile Island, anyone?) They can store a lot more power than typical lead acid batteries, they weigh less, and can be discharged further than the typical 50 percent of lead acid without damage. They can be charged using existing technology and can be retrofitted pretty easily to any RV.

Sounds Great Right???!?

There Ain't No Such Thing As A Free Lunch. (TANSTAAFL)

They cost. They cost big. But wait! The prices are slowly coming down. A couple of years ago they were $3,000 (2009) now you can get a 200Amp/Hr setup for around $1,500. Now that electric vehicles are becoming more common place (let me tell you about my GM EV1 someday...) the batteries that drive (yes, pun intended) are dropping in price due to increased demand. With more factories expanding all the time it won't be too long before you can get these for $500/200Ah!
Typical Lead Acid Battery

Let's do some basic economics math. The typical RV has two lead acid batteries that provide around 200A hours total. You can discharge them safely to 50 percent so you have 100Ahrs to play with. They can usually be charged/discharged (a "cycle") around 500 times or so. The average cost for these are around $150, perhaps you have to have them shipped. They weigh around 80 pounds each so figure some money for that as well. If you take $150 times two batteries that's $300 and then divide it by 500 cycles you get  about 60 cents a cycle.

4 cell 12.8V nominal LiFePO4 Pack

Now look at lithium phosphate batteries. Today, the cost of one 200Ah battery would be around $1500 but that's where we have to take another path. You can discharge these to 80 percent so from 200Ahrs you get 160Ahrs to play with. You can do this for 3000-5000 cycles! So if you look at the cost $1,500 divided by 3000 cycles = 50 cents a cycle! At 5,000 cycles it's only 30 cents a cycle! This does NOT take into consideration that you are getting 60 percent more amp hours per cycle to play with. If you figure that in, it's even less expensive since you could go with a smaller battery.

Did I mention they weigh 30 percent less that a lead acid battery!

Do you remember when I mentioned TANSTAAFL?

There are differing opinions on charging these beasties. Surely, a quality charge controller that can be programmed what the voltages should be at the various stages (Bulk, Absorb, Float) will work fine. The problem is that sometimes the cells themselves can vary in voltage and not charge fully. If you have four cells per battery pack, it's important to make sure each one is close to the other to make sure the battery lasts. They also do not like being overcharged (Who does?) and REALLY do not like being discharged below around 10.8 volts. Shouldn't be a problem as long as you monitor them and/or get a low voltage cut-off...I will be getting one and setting it at around 85 percent discharge. This way I can't destroy my expensive battery pack!

Typical Cell Mounted BMS
There are electronics that can manage all this for you. Available as a separate device or even pre-built into (onto?) your battery back. These will fix that problem right up at a bit of added cost. They are called Battery Management Systems (BMS) and can range from under $100 to multi-thousand sophisticated versions with LCD displays and lots of bells and whistles.

While I believe it is important to monitor your batteries (any kind) I believe the best monitoring software is in you own brain! Keep an eye on you voltages and you'll be OK. Check the individual cells once in a while and see if there any variance, If so, charge the low cell, or drain the high one :)  I oversimplify, but these batteries are pretty robust.

Conclusions?


I'm not ready to make any set conclusion on a direct swap for lead acid at this time. I will be testing a 400Ah pack(s) in the coming weeks and will keep everyone posted on the results. It SEEMS like a great advance for RVers (What's not to love?) However, I'll be the guinea pig and experiment with them. Likely, something will fry, explode, melt down, or not be as advertised. Let the manufacturers put their product where there mouths are!
Various sizes of LiFePO4 cells

Stay Tuned to this space in the coming months for some real world testing data from yours truly. Everyone could use more in the battery bank, couldn't they?

Be Seeing you, down the road.

Rich "The Wanderman"
http://www.thewanderman.com

14 comments:

  1. excellent news. thanks.

    ReplyDelete
  2. Gracer,
    I've been in contact with all the major manufacturers, so I should be able to sort it all out and provide some "real world use" information in the coming months.

    Rich "The Wanderman"

    ReplyDelete
  3. DesertManfred,
    Me too! Seems that this is a greatly underserved market for the Lithium Phosphate manufacturers and integrators. I am personally VERY interested in this technology since my Class a is always short on space and you can never have too much reserve capacity!

    Rich "The Wanderman"

    ReplyDelete
  4. Thanks for posting this. I first heard of this a few months ago from online friends who have very strong technology skills and were converting a bus. I have far less technology skills, and my project is a "do it yourself" camper in a small vehicle. I look forward to learning much more.

    ReplyDelete
  5. Are you familiar with this study at Technomadia?

    http://tinyurl.com/7htorgc

    rhetter69

    ReplyDelete
  6. Ray,
    Excellent Find! I hadn't seen that one. I will try and contact them at some point and see how their system is faring. How I wish I had the space to use like they do.

    My build will always tend to be geared toward smallest/best in a limited space.

    Thanks!

    Rich" The Wanderman"

    ReplyDelete
  7. Calvin,
    Stay tuned....I am gathering all the bits and pieces and designing a system that most any RV'er could live with (or scale for their own use)

    It's a huge amount of research....I like it!

    Rich "The Wanderman"

    ReplyDelete
  8. Quarterly report?

    ReplyDelete
    Replies
    1. Anonymous,
      So far, cooperation from vendors has been abysmal. The manufacturers are more interested in developing a product, but are slow to respond from china.

      Keep checking back. This is a "near and dear" project for me.

      Rich "The Wanderman"

      Delete
  9. Great work so far, I see you responded to Calvin about working on a "RV system" would love to read about when you have it put together

    ReplyDelete
    Replies
    1. B Smith,
      I tried putting together a system, while it WILL work, the prices are still too high to justify a changeover. They are coming down in price, and I believe they will be competitive with Lead Acid very soon. Stay Tuned!

      Rich "The Wanderman"

      Delete
  10. Rich, Are you still working on this project or have you found a solution?
    Thanks!

    ReplyDelete
    Replies
    1. cpolo.
      You bet I am... All of my updates and upgrades to the solar charging system (including the latest) talks about Lithium Iron Phosphate as a replacement. They WILL work great, but the price points are still VERY high in comparison to Flooded Lead Acid batteries. When I can source a reliable 200ah LiFePO3 battery with a BMS and HVD for under 500USD I will buy TWO of them. But, for now, they are no where near that number. Almost double. I've also never been given the opportunity to test any from ANY manufacturer. That's a red flag in my book.

      Keep reading! And thanks for you interest.

      Rich "The Wanderman"

      Delete

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