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Old 29-06-2011, 10:31   #1
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Lithium (LiFePO4) Install

We are reluctant pioneers on Namo but our small (4 X 6V AGM) house bank gave out and yesterday we replaced it with a Thundersky bank (16 X 160AH cells) organized into 4 X 160AH batteries for a total capacity of 640AH. We bought the batteries from a company that primarily does electric vehicle conversions Electric Autosports Inc. | Electric Vehicle Specialists but has some marine experience and products.

Our reasons for taking this route were (a) Nigel Calder's advocacy of this technology, and (b) the cost of getting equivalent capacity from lead acid into our boat appeared similar to lithium. Our approach is to keep the installation simple and while the new batteries have cell boards to keep the cells balanced, we intend to rely on the existing alarms and chargers aboard the boat. As you can see from the picture the Thudersky's are a perfect fit in Namo's battery box and hopefully will give us effectively double the capacity in the same footprint. Day 2 and so far so good!
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Old 29-06-2011, 10:50   #2
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Re: Lithium (LiFePO4) Install

Twice the capacity....I like it. Do you have a charge controller? I thought lithium batteries had a different charging a algorithm than lead acid. I've seen some controllers that allow for different battery types is why I mentioned this.
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Old 29-06-2011, 11:19   #3
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Re: Lithium (LiFePO4) Install

We do not have a different charge controller. We are presently using the AGM battery settings on our Mastervolt Combi which charged the batteries and is now in float mode with no charge current being applied. I checked the Balmar regulator on the same AGM settings and it seemed to work OK as well. We also have BlueSky solar charge controllers and I have not yet adjusted the voltages. I have heard that lithium batteries can take higher charge voltages (14.8V) than our AGM settings but time will tell. Some fine tuning of these parameters is probably in order but it seems to be acceptable "out of the box".

The most noticable difference is that the charger and alternator work flat out with these batteries as they have a very high charge acceptance rate of three times capacity or 640 X 3 = 1,920A, more than ten times what our alternator puts out.
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Old 29-06-2011, 12:09   #4
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Re: Lithium (LiFePO4) Install

Has Thundersky sanctioned using the batteries without a special charge controller then?
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Old 29-06-2011, 12:35   #5
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Re: Lithium (LiFePO4) Install

Good question about the warranty policy of Winston Thundersky - I don't know the answer although I hope this is more of a question for our supplier who does warrant this kind of installation.
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Old 29-06-2011, 12:56   #6
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Re: Lithium (LiFePO4) Install

Hi;

I am getting ready to do the same thing, with 8x 200ah cells from Hipower.

Are you using any kind of BMS? We have a Cleanpowerauto housepower BMS. These are the same folks that make the mini-bms.

Chris
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Old 29-06-2011, 13:06   #7
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Re: Lithium (LiFePO4) Install

No BMS other than the cell boards - so far we plan on occasionally checking the cell voltages directly with a voltmeter. Also the led lights on the cell boards do provide a visual indication of problems. Certainly if one had a car installation with 96 cells, a BMS would be required and we may still install one on our simple system down the road
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Old 29-06-2011, 13:18   #8
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Re: Lithium (LiFePO4) Install

When you say cell boards, what do you mean? Who provided them, what make?

Chris
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Old 01-07-2011, 12:41   #9
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What was the cost of the batteries?
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Old 01-07-2011, 14:09   #10
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Re: Lithium (LiFePO4) Install

Cost? We negotiated a price with the supplier so can’t say exactly but converting to lithium made economic sense to us because the boat has a small battery box that held 4 dead 6v golf cart AGMs. We wanted to get to 1,000 AHs which would have meant buying 10 new AGM batteries ($2,500) and doing the boat surgery ($3,000) to build a new ventilated battery box under the aft double bunk Lead acid batteries should not be discharged below 50% so would provide 500 AH usable. The lithium batteries are rated at 640 AH of which 80% or 512 AH usable for about the same price ($5,500).
I heard Niger Calder speak at a boat show recently in which he advised that lithium may be more economical than lead acid when you take into account their higher cycle life and lower cost in diesel to recharge them due to their higher charge acceptance.
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Old 01-07-2011, 14:23   #11
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Re: Lithium (LiFePO4) Install

Chris, not sure who makes the "cell boards" but they are small circuit boards that are mounted on the battery terminals that equalize the cell voltages at the high end of the charge cycle. They have LED's that indicate the state of the cell charge. I think there are several manufacturers to choose from.
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Old 01-07-2011, 17:08   #12
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Re: Lithium (LiFePO4) Install

It's a debatable point as to whether a BMS is needed in a relatively low power yacht environment. The systems in theory needs low voltage protection but most boat systems will drop out and alert the user well before the LVC point. HVC events are practically impossible using normal marine chargers and alternators. Cell Mis balancing in general will not occur at fractions of C charging typical on a yacht. It's important to realise that lifepo4 used in electric vehicles are subject to reapeated LVC and potential HVC and cell balancing are a function of aggressive multiple C charging reigimes

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Old 01-07-2011, 19:48   #13
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Re: Lithium (LiFePO4) Install

I am a little worried about low voltage events occuring such as if we leave the boat and the fridge draws the batteries down over a week or so. One solution might be drive a relay off the alarm terminal of our Xantrex LinkLite monitor.

I am having some fun (sad I suppose on such a beautiful holiday Friday) by running a 1,500 watt electric heater through the inverter for a test and the voltage under load remains rock steady at 12.9V as the amp hours rack up. Although this is how they are supposed to perform, it is amazing to see it. According to the literature, the batteries could supply ten times this amount power. The Thundersky batteries remain cold to the touch although the inverter has got a bit warm.
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Old 02-07-2011, 09:51   #14
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I bought 800 ah (16 x 200) of thunder sky a couple of months ago, so far I'm really happy with them. I went with the mini bms system as on a couple of occasions when not on the boat I had drained the old batteries (flooded GC) quite low. I didn't want to take the chance on destroying the lithium. The bms is connected to a couple of Tyco contactors so if voltage drops too low batteries are disconnected. The cost of the bms in minimal compared to the batteries I don't think it's worth the risk to not install one.

Doug
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Old 06-07-2011, 16:13   #15
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Re: Lithium (LiFePO4) Install

Doug:

As you are a couple months further down the road with this technology it would be interesting to know what your charging program is.

I first did a balancing charge to equalize the cells to 14.8 volts or 3.7 volts/cell. My plan now is to keep to a fairly conservative maximum charge voltage of 14.0 volts (3.5 volts/cell) as I do not have a lot of control over the charging amperage (from the Balmar alternator and Mastervolt charger) and am concerned about the possiblity of overcharging an individual cell.

How have you programmed your boat's voltage regulator and charger to accomodate the Thunderskys?

Thanks,
Ian
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