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Old 22-04-2012, 09:27   #376
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Bob,

I would buy a single cell capacity that meets your needs. Series/parallel will be a nightmare for keeping cells balanced. As to life, if cared for and 70% DOD, you should see 3000 cycles before bank capacity degrades to 80% of rated.
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Old 22-04-2012, 10:00   #377
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Bigger cells won't fit in the present space. And I don't have the time to wait for new 1000 ah cells from China anyway. I don't think these are kept on hand anywhere!
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Old 22-04-2012, 13:25   #378
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by downunder View Post
Size of your bank will have an effect. You have not indicated the size of LiFeO4 bank you need. 400ah,250ah or 200ah ???
I believe I mentioned a 4 cell 400Ah bank. Total capacity of 400Ah.

J
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Old 22-04-2012, 19:16   #379
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi Bob (ebaugh),

I just read your post, so I'm going to go through it a few times and post a few different replies with my thoughts as I digest it.

My first thoughts are:

- Bob (Deckofficer) talks about expected cycle life, and that sort of result seems to be a fairly consistent claim across manufacturers. I know that some manufacturers have run accelerated cycle tests which support that claim, but I'm not yet aware of any cruiser who has run these cells more than a few years in real conditions (Deckofficer, please correct me if you're aware of any). So, I still think that the jury is still out on cycle life in our application, but it is promising. As you've discovered, lead-acid cycle life is actually terrible if you're a regular heavy (for a house bank application) user, so hopefully LiFePO4 will prove to be significantly better, even if it doesn't match fully the claims. But you will be on the leading edge here for marine housebank usage, so be prepared for anything (and let us know about your experiences).

- Have you looked at if the 400Ahr cells fit in your space? - those would be better than 260's if they fit. Since weight probably isn't an issue for you, and I'm guessing that space isn't either, I'd personally fill up the space with as much capacity as can fit (even if you have to parallel cells). That will get you more time without running your generators, as I'm sure you know, which would be good. The deeper discharge and higher % charge capability of LiFePO4 should help you significantly here.

- I don't have practical experience of paralleled strings, but I'd think that paralleling 2 or 3 strings of large cells won't be too much of a problem with balance. I think that T1Terry uses a few series-parallel strings and seems to have no issues. I do think that you need to be more vigilant about monitoring cell balance, but as a liveaboard you can do that. I'd suggest that you get a cell voltage monitor which enables you to view the voltage real-time.

You sound like you're pretty much on top of your energy usage, needs, and maintenance issues, so I think it really is that easy. I don't think anyone should be afraid of these cells: you just need to pay attention to the detail and note the differences. If you've run a proper charge/discharge/maintenance regime with sealed-lead cells, then you'll be able to do it with LiFePO4.

I'll post some more comments after I've thought about your chargers some more.

Cheers,
Paul.
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Old 23-04-2012, 05:19   #380
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Paul,

I think 400's will fit. After that they get too tall. It's mostly a matter of what I can find available. I need them by June in Grenada, and don't think I have time to order from China. Weight is no issue, space is. To keep it simple they need to fit in 2 boxes sized for 6 golf carts each in a row. Cost is an issue so I'm going to be limited to 800 to 1100 Ah.

Until I found this thread, and Terry's posts, I figured I needed to configure 4S for 12V then 4P. That is the only way to monitor all individual cell voltages. And use some sort of BMS. But at least some of the applications on this thread imply that's not needed for a max 4S configuration, and I'm a believer in simple when possible. I'm guessing annually I would need to unhook the cells to check individually.

If it helps the configurable inverter/charger is a Magnum 2012, and the older one is a Xantrex (Trace) RS-2512. I only use one at a time for inverting (for obvious reasons), but both to charge. I have to be careful when starting to charge so they both go into bulk mode to start.

Look forward to your future comments

Thanks Bob
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Old 23-04-2012, 06:19   #381
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Ebaugh,

As a way of introduction, we are currently cruising with a 400ah LIFEPO4 pack, full-time since November.

You have it backwards. Lets say you are putting together a 400ah bank comprised of eight, 200ah cells. You parallel two cells together to make a 400ah, 3.2v cell, and do that with all eight cells. Then, string those in series to make 12v.

This is HIGHLY preferred to making up several 12v strings, and then paralleling them.

It is my understanding that by stringing to make up capacity, you build-in some tolerance for out of balance conditions. If one of the cells in a 3.2v string goes a little high, it will tend to be balanced out by the other, lower cells.

In contrast, if you do it the other way, you could end up cooking 1/2 of your bank, it one of your 12v strings hits high voltage before the other string. Yes, they could balance themselves, but not fast enough perhaps?

Chris
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Old 23-04-2012, 06:47   #382
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Quote:
Originally Posted by witzgall
Ebaugh,

You have it backwards. Lets say you are putting together a 400ah bank comprised of eight, 200ah cells. You parallel two cells together to make a 400ah, 3.2v cell, and do that with all eight cells. Then, string those in series to make 12v.

Chris
Chris, That is the plan. Go back a couple of posts and see my first post in the thread. Thanks, Bob
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Old 23-04-2012, 07:07   #383
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Chris, That is the plan. Go back a couple of posts and see my first post in the thread. Thanks, Bob

Oops, Sorry. Good luck with your project.

Chris
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Old 23-04-2012, 13:00   #384
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Hi Bob (ebaugh)
Perhaps check with http://www.ev-power.eu/
They have several sizes on stock, currently 47pcs of Winston 1000Ah.
They run a blog also: http://gwl-power.tumblr.com with lots of interesting posts.
I bought 6pcs of 90Ah 12V batts from them last year, which I run for propulsion (24V - 2Kw) outboard and as housebank.
I charge with 2pcs 20A on shorepower and with solar when sailing.
So far I'm very happy with the setup.
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Old 23-04-2012, 13:23   #385
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
I would buy a single cell capacity that meets your needs. Series/parallel will be a nightmare for keeping cells balanced
why?, the general issues affecting cell balancing are not generally present in a boat system.

Dave
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Old 11-05-2012, 10:13   #386
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Well I took the plunge. Could not source larger cells for delivery to Grenada in time to meet our schedule. Not without air freight, which was too expensive. So I will be using GBS 100 Ah cells, 48 of them for a 12P, then 4S array for a 1200 Ah bank at 12V. GBS batteries are sold by several vendors in the US, but are imported by Elite Power Systems. They seem to have a good reputation among the EV community that uses them.

I am planning to install a BMS, specifically the one engineered for Elite and sold on their website. I'm not sure it's really necessary, but I did not have a SOC meter on the boat and it was only slightly more expensive to add the BMS which includes one. It also allows cell monitoring at the electric panel, something else I wanted to have.

Wish me luck. I should have them installed by the end of June.
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Old 11-05-2012, 18:53   #387
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by ebaugh View Post
I've read this thread twice now from end to end. I think most of it has sunk in, but I'm not sure. So I'd like to see if this is a reasonable plan. And ask a few questions.

My house bank is presently 12 6V lead acid golf cart batteries. We use 400-500 amp hours a day at anchor. I know that's a lot. It's mostly refrigeration (4 110V Systems) and reducing consumption is a topic for a different thread. We are an all electric boat, and have to run the generator for cooking, so we charge at the same time with paralleled inverter chargers, with a maximum rate of 200 amps. A typical day we charge 1-2 hours in the morning and 1-2 hours in the evening, normally at 150 amps bulk due to other generator loads.

We live aboard and spend 80 percent of our time at anchor. The golf carts work OK, but their service life is about 18 months due mostly to cycle life. The days we miss one of the charging cycles we go from 80-85 percent SOC to around 30. I'm hoping this investment will see at least a 5 year service life. Does this seem reasonable for a lithium swap out? I'd also be interested in what you think the efficiency difference might be given the data below. Less generator time daily would save some fuel.

I'm considering installing 16 Sinopoly/Thundersky 260 Ah cells. First connected 4P for 3.2V then 4S for the house. BMS will be the inverter. HVC by setting the max charge voltage to 14.4 V and LVC by turning off the inverter at 11.5 V. Almost all loads are AC. Underway, the alternators (adjustable charge voltage, but no smarts) are presently set to 13.2 V to keep from overcharging on multi day runs.

One of my inverters allows a custom charge profile, the other one is either 14.4 or 14.6 bulk/absorption and 13.2 float. Both have temperature compensation. I'm planning to remove the sensors to eliminate that variable. Underway, the ambient temp is about 115-120 degrees F. At anchor its more like 90 to 95F. Set both to 14.4 bulk. How long should 14.4 be held during the absorption phase? I can set this time for both inverters. Both are timers without consideration for charge rate. The adjustable inverter can have a different float voltage, mostly for marina time, what should this be set to?

I suppose ideally you have a system that keeps track of power used and replaced, but I don't have that. So it has to be voltage and time based.

After breaking in of a few cycles, I might tinker with using 14.6 bulk if the cells are close. But unless I keep them the same value, one will stop charging once the bulk value is reached. Would this change the absorption time?

The average load is about 20 amps, peaks to as much as 250 amp with other loads intermittently. I also start the mains off this bank, about 600 amps for a few seconds. Batteries interconnected with copper bus bar 3/4 wide by 3/8 thick. Installed in old golf cart battery box. Plan to secure with wood wedges to prevent movement, is banding required? Balancing resistive path to each cell by connecting at opposite corners of each 4P 3.2V cell.

Initial cell balancing per this thread by charging in a temporary 4 single cell series configuration and manually loading the high cell until balanced.

It seems too easy, am I missing something? Thanks for you help!

Bob
Hi Bob,

I thought this thread had died so I haven't been back for a while, got a bit of reading to do :lol:

I see you have gone with the GBS cells, it will be interesting to hear your results and follow your experiences using this brand, all information is good information. I went with the Winston Battery Co cells (formally Thundersky before the company split) mostly because of their superior cycle life and ability to charge and discharge at higher rates than most of the other prismatic cells. The cylindrical can charge/discharge at higher rates, of no value for house battery use, but the cycle life is rather short and far too many connection points, to me, just asking for trouble if they are hidden in boxes so you can't check them.

Good to see you understand the principle of series/parallel to build capacity, strings of single cell batteries paralleled simple causes big balance problems, parallel connection at single cell level (3.2v) actually aids balancing, I see a few members here have found the same thing.
As far as a BMS.... avoid an active balancing unit, they kill a lot of cells due to control failures. The balancing issue is so negligible in a 4 cell series pack, especially one with multiple parallel cells, you may find you never need to do it but 12mthly doesn't hurt for peace of mind. The idea of needing to do it on a constant basis simply isn't correct, I'm doing my 720Ah pack now after 12 mths use with 24/7 200Ah plus discharges over night and a number of low voltage disconnects (LVD) due to crap solar conditions. They got to 200mV apart at the top end of the charge, still within 10 mV during use.

A few things in your post I thought I should touch on

One of my inverters allows a custom charge profile, the other one is either 14.4 or 14.6 bulk/absorption and 13.2 float.

If you are going to use 14.4v for boost cut off don't hold the cells at that voltage, 13.9v for absorption if you must have one and 13.8v float. I would seriously look at dropping the boost voltage to 14v, that's 3.5v per cell, but if the charge rate is higher than 0.5C (50 amps per 100Ah capacity) then 3.6v or 14.4v at the terminals is ok for the boost section only. Please keep in mind, it's individual cell voltages that are important, not terminal voltages, 3.4v rested is as full as you can get, there is no 110% full, the voltage and amps (watts) pumped in after the cell is full is doing nothing but heating the cell and boiling the electrolyte, killing the cell.

Batteries interconnected with copper bus bar 3/4 wide by 3/8 thick.

The links connecting the cells should be very flexible and with a hump in the middle if possible to encourage movement at this point. If the links are too rigid they will eventually start moving under the terminal bolt creating a resistance joint, resistance equals heat at high loads resulting in terminal problems and a rapid out of balance condition as the resistance created heat burns watts at the cell that weren't used else where in the pack = out of balance as far as capacity. This capacity out of balance is the cause of the sudden high voltages at the peak of charge and sudden voltage drop at total discharge.

Hope this lot of rambling thoughts helped and didnít add to any confussion.

T1 Terry
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Old 11-05-2012, 21:56   #388
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Just as an update to my experience with these cells (and my Aerogel insulation projects), and I hope I'm going to inspire, not create jealousy !

Last winter I installed four 200 aH HiPower LiFePo4 cells for the only bank in the boat.
I also rebuilt my fridge/freezer with Aerogel (actually Cryogel) insulation and installed a keel cooled compressor.
Added to that was a BlueSky MPPT controller and a total of 320 watts worth of solar panels.
We also have converted to almost all LED lighting except for the nav lights.
Here comes the good part.
We have SO MUCH extra solar that I started musing about using the inverter to heat water.
Don't laugh, I can hit the (now insulated with Aerogel) water tank about a half hour in late AM giving us steaming hot water for showers, dishes etc, and still have full batteries by afternoon.
PINCH ME ! I'm dreaming !!
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Old 11-05-2012, 22:55   #389
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I thought it would be a good idea to use a 2.2kw 240v jug as a "dummy load" to test my 80v solar panels max 400w. It was boiling the water in the jug after 4hrs!! not what I was expecting.

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Old 12-05-2012, 02:49   #390
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

We have been working on a system that turns the water heater on for 5 mins if a cell hits 3.6v, all charged from solar. We adjust up the peak charge voltage to 28.4v (24v system) to tempt a few cells to go into run away and hit 3.6v before the others. The thermotstat turned off the heater element by 2pm and then alarms etc started going off because there was no where to dump the excess solar. Brian (the motorhome owner) now uses his air con in the afternoons to chill the rig down rather than waste the excess solar. He is now looking at increasing the battery bank to 720Ah @ 24v and putting electric stove back in so he doesn't need to buy LPG bottle refills. His whole rig, except for the LED lights, runs on 240vac including a 220ltr fridge/freezer via an inverter 24/7.

T1 Terry
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