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Old 17-01-2013, 06:13   #1141
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Early adopters need not worry as you are not covered by insurance, so self-insurance is the game...hope ya got deep pockets.

I stand by my post from over a year ago, as well as the post a few days ago.

Lloyd
Please show me the exclusion in my policy, or any policy, that "excludes" LiFePO4 batteries.

Please show us in the ABYC standards were LiFePO4 are non-conforming...?
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Old 17-01-2013, 06:25   #1142
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Insurance is a tax on people who cannot do math. The premiums paid have to cover the claims paid out + the operational overhead + taxes + profits. It should be obvious that insurance companies collect more than double (sometimes three or four times) in premiums than they pay out in claims.

There are exactly three circumstances it might make sense to buy insurance:
1. The magnitude of a potential loss (relative to net worth and income) is so large it would ruin one's life. For example, one who is retired with little or no income and owns only a boat would be ruined by loss of the boat.
2. Insurance is required by law and the penalties for non-compliance are more severe than the expected losses of paying for insurance.
3. One has private information not available to the insurance companies that shows the real risk is much higher than the insurance companies would think. Formally, this is called "moral hazard". Hypothetically, if an insurance company thinks a boat is safe but the owner knows that it's being eaten by an unknown-to-science species of marine termites then insurance would be a good deal for the owner and a bad deal for the insurance company.

Remember, insurance can never be a good deal for both the insurance company and for the owner, unless the owner is vastly more risk-averse than the insurance company (see exception #1 above).
Hmmmm.... We pay $812.00 per year (67k agreed value) and have owned the boat 6 years. Was hit by lightning at year three of ownership. The check was for $26,845.00... I would need to keep our boat for 33 years to equal the coverage we were reimbursed for lightning damage. Our rates did not budge after the claim.... I don't know a marina or winter storage yard around here that does not at least require liability insurance... I'll gladly pay my $800.00/year...
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Old 17-01-2013, 06:36   #1143
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

All the back and forth over BMS vs. no BMS and I paid:

$75.00 = House BMS Control Board
$55.96 = 4 BMS Cell Modules
$80.00 = EV200 LVE contactor
$20.00 = HVE relays for alt and solar...

Total $230.96

Does not sound unreasonable to me. I may also throw a cell logger on there too.. I will still be at about the same price as four Odyssey PC2150 AGM batteries that have 400 cycles to 80% DOD vs. roughly 3000 cycles to 80% DOD...
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Old 17-01-2013, 06:49   #1144
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The reason you balance is to get the maximum capacity out of the bank ( which is why its a big thing in EV land , especially with many batteries ) if however your demands are within the capacity of the bank at its most imbalanced , there's no need to balance.

I have found that generally over time the cells trend is to converge at fractional C charging / discharging

Dave
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Old 17-01-2013, 08:16   #1145
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Hmmmm.... We pay $812.00 per year (67k agreed value) and have owned the boat 6 years. Was hit by lightning at year three of ownership. The check was for $26,845.00... I would need to keep our boat for 33 years to equal the coverage we were reimbursed for lightning damage. Our rates did not budge after the claim.... I don't know a marina or winter storage yard around here that does not at least require liability insurance... I'll gladly pay my $800.00/year...
Of course, insurance companies lose money with a few customers.

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I have found that generally over time the cells trend is to converge at fractional C charging / discharging.
It would be great if we had a large statistically-significant data set indicating whether LiFePO4 cells tend to converge or diverge over time and under which conditions.
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Old 17-01-2013, 09:47   #1146
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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It would be great if we had a large statistically-significant data set indicating whether LiFePO4 cells tend to converge or diverge over time and under which conditions.
This is true about a lot of characteristics of LI Ferrous, I wish we had data over time

dave
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Old 17-01-2013, 10:35   #1147
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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But no system out there today manages a pack by monitoring current in and out.
I'm sorry, but you haven't done your research.

If it was just BMS vendors selling you stuff that wasted money for useless features it wouldn't be so bad, but a system which top-balances on every charge is reducing their life, and some are even dangerous enough to create a fire and destroy YOUR ENTIRE BOAT.

JackB
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Old 17-01-2013, 10:36   #1148
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I've learned a lot here by reading it. I have a question/remark

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Originally Posted by goboatingnow View Post
The reason you balance is to get the maximum capacity out of the bank ( which is why its a big thing in EV land , especially with many batteries ) if however your demands are within the capacity of the bank at its most imbalanced , there's no need to balance.
But this does seem to imply that a smaller bank would be sufficient to meet needs if kept balanced. How does the cost of the BMS compare with the savings of having a somewhat smaller bank?

On another note: Both Mastervolt and Victron now offer Lithium batteries that give the appearance they can be used more or less as drop in replacements for LA. (Mastevolt has even announced LI starter batteries)
How good value for money are these?
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Old 17-01-2013, 10:43   #1149
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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But this does seem to imply that a smaller bank would be sufficient to meet needs if kept balanced. How does the cost of the BMS compare with the savings of having a somewhat smaller bank?
Is there really an opportunity to save money by buying a 1% or so smaller bank?
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Old 17-01-2013, 10:48   #1150
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Status update. On pack #2 that had the two errant cells, after a top and bottom balance, this time during discharge I'm at the 40 hour mark, 1200 w-hr pulled from pack (1280 w-hr cap) and two cells at 3.31 volts, the other two at 3.30 volts. The last time at 980 w-hr pulled, one cell had dropped to 2.5 volts. I'm a happy camper, they appear to be balanced. The fast series charge is the next test, as this pack has always needed to have the charger turned off early because one cell would get above 4.0 volts. I'll find this out in 6~8 more hours.
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Old 17-01-2013, 10:51   #1151
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Status update. On pack #2 that had the two errant cells, after a top and bottom balance, this time during discharge I'm at the 40 hour mark, 1200 w-hr pulled from pack (1280 w-hr cap) and two cells at 3.31 volts, the other two at 3.30 volts. The last time at 980 w-hr pulled, one cell had dropped to 2.5 volts. I'm a happy camper, they appear to be balanced. The fast series charge is the next test, as this pack has always needed to have the charger turned off because one cell would get above 4.0 volts. I'll find this out in 6~8 more hours.
Good luck and thanks for keeping us informed!
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Old 17-01-2013, 10:59   #1152
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Is there really an opportunity to save money by buying a 1% or so smaller bank?
So you only lose about 1% by not balancing? I thought it could be a lot more. Especially after repeated charge/discharge cycles.
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Old 17-01-2013, 11:00   #1153
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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So to you I ask will it be insured???

HOW WILL YOU KNOW???

TODAY'S INSURANCE BUSINESS IS THE BUSINESS OF DENYING CLAIMS AFTER RECEIPT OF PREMIUM.

lloyd
No kidding.
See my Safeco Insurance rant if you haven't already:

An Old Dufus Hit My Docked Boat
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Old 17-01-2013, 11:06   #1154
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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So you only lose about 1% by not balancing? I thought it could be a lot more. Especially after repeated charge/discharge cycles.
In my case with the cells that sat in inventory for 2 1/2 years, my loss was closer to 10%, but as you can see from my above post, they are getting balanced.
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Old 17-01-2013, 11:08   #1155
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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So you only lose about 1% by not balancing? I thought it could be a lot more. Especially after repeated charge/discharge cycles.
I think we need to distinguish between balancing once before installation versus a continuous attempt to keep them balanced. I haven't seen any evidence that cells diverge after having been balanced once and there have been reports here of convergence (at least with moderate C values).

My current inclination is to balance once and then once a year check individual cell voltages. I have no intention of buying a BMS. Your windage may vary.
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