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Old 06-01-2011, 19:50   #346
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As an aside...regarding a BMS; I'm a fan of having dual positive busses; one for charging and one for loads. In other words, each battery bank should have TWO relays (one for charge sources, the other all the loads) rather than one protection/isolation relay.

This way, if there is a low-voltage cutoff (for instance: oops, I left the fridge on and generater didn't auto-start when no one was home!) then the BMS leaves the charging buss on so that when a source comes on (like the sun come up and the solar panels kick in) then the voltage come up, the load relays click back on, and you're good to go. Well, until the sun goes down, in this particular scenario...;-)

Conversely, if you have a charge source go awry (solar, alternator, whatever) and it overshoots the max voltage for the system, the BMS can cut the charge buss only without shutting down the whole boat.

Like I said in the previous post, there are different philosophies out there, this just happens to be mine (and why I like the Genasun system).

B
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Old 06-01-2011, 20:23   #347
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All good points Ocean Planet and all very true.
I will add another angle to the argument.
In a report on the cause of lead acid battery failures as analysed by a marine insurance company the biggest single cause (more than 50%) of battery failures was as a result of cells failing due to constant vibration/pounding in rough seas.
So if you want the maximum reliability when purchasing expensive LiFePO4 batteries buy a battery with cylindrical cells rather than prismatic cells. Cylindrical cells are tightly wound and don't have separate plates which can separate and short out over time or otherwise cause premature battery failure. In addition cylindrical cells are the only LiFePO4 cells which can provide very high discharge rates so on power boats can also be used for engine starting as well as for house power.
The aim of the prismatic cell manufacturers is to make their cells as cheaply as possible and as a result they perform negligible (or often nil) reliability testing. We actually perform extensive vibration testing (as in the computer monitored vibration test rig) and reliability testing of our batteries and obviously this testing takes time and adds to the cost of the end product due to the investment in factory QC testing equipment.
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Old 04-03-2011, 03:30   #348
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

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Originally Posted by LiFeTech Energy View Post
All good points Ocean Planet and all very true.
I will add another angle to the argument.
In a report on the cause of lead acid battery failures as analysed by a marine insurance company the biggest single cause (more than 50%) of battery failures was as a result of cells failing due to constant vibration/pounding in rough seas.
So if you want the maximum reliability when purchasing expensive LiFePO4 batteries buy a battery with cylindrical cells rather than prismatic cells. Cylindrical cells are tightly wound and don't have separate plates which can separate and short out over time or otherwise cause premature battery failure. In addition cylindrical cells are the only LiFePO4 cells which can provide very high discharge rates so on power boats can also be used for engine starting as well as for house power.
The aim of the prismatic cell manufacturers is to make their cells as cheaply as possible and as a result they perform negligible (or often nil) reliability testing. We actually perform extensive vibration testing (as in the computer monitored vibration test rig) and reliability testing of our batteries and obviously this testing takes time and adds to the cost of the end product due to the investment in factory QC testing equipment.
Hi LifeTech,
Vibration and schocks are key issues on a fast sail boat, with modern riging, carbon mast ect.... and the frequencie range can be larger than those generated by the old nice diesel.
Regarding the Li bats installation, my packs are put on long strips of high density neopren foam, acting as sillent blocks and then compress with the spectra lines used to attach the pack to the boat.

rgds
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Old 04-03-2011, 03:42   #349
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

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Originally Posted by OceanPlanet View Post
As an aside...regarding a BMS; I'm a fan of having dual positive busses; one for charging and one for loads. In other words, each battery bank should have TWO relays (one for charge sources, the other all the loads) rather than one protection/isolation relay.

This way, if there is a low-voltage cutoff (for instance: oops, I left the fridge on and generater didn't auto-start when no one was home!) then the BMS leaves the charging buss on so that when a source comes on (like the sun come up and the solar panels kick in) then the voltage come up, the load relays click back on, and you're good to go. Well, until the sun goes down, in this particular scenario...;-)

Conversely, if you have a charge source go awry (solar, alternator, whatever) and it overshoots the max voltage for the system, the BMS can cut the charge buss only without shutting down the whole boat.

Like I said in the previous post, there are different philosophies out there, this just happens to be mine (and why I like the Genasun system).

B
I fully agree, and I build my pack 24V 130Ah in this way with the GENASUN components.
To be safer, I used the Victron bat controlers H Volt' and L Volt' alarms to overlap the BMS HV/ LV relay controls. This give a kind of "early warning" before the BMS disconnects your pack while you are running full speed with spinack and autopilot....
rgds
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Old 24-03-2011, 19:07   #350
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

Gael,

Nice going ! Alarms are our friends...:-)

Smooth sailing!
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Old 20-04-2011, 22:31   #351
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Re: Okay. Status update.

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Originally Posted by jallum View Post
The batteries I ordered (Thundersky 300Ah's) have begun to arrive. Here's a picture of the first batch, adding up to 300Ah@24v (or 600Ah@12v!)... with a National Geographic for scale. Total cost for this batch: $2640.00, plus shipping. This is going to be good fun. Now, to select a BMS.
I'm looking at Interstate Deep Cycle batteries at $95 for 208ah/12V. At $285 FOB (no shipping), your batteries will have to last 10 times as long to pay out. Since I figure to get at least 2 years out of mine and I'm almost 59, I'd BREAK EVEN at age 80.

I hope they work great, but I can't see the advantage. Ask me again in 20 years.

John
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Old 05-05-2011, 12:39   #352
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

"As for RaceCell, I looked at their stuff. You really can't call it a BMS, since it only does top balancing and no LVC. Without LVC its not a BMS, its a waste of money."

RaceCell offers 3 different BMS systems with LVC.
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Old 05-05-2011, 12:56   #353
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Re: Okay. Status update.

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Originally Posted by Feral Cement View Post
I'm looking at Interstate Deep Cycle batteries at $95 for 208ah/12V. At $285 FOB (no shipping), your batteries will have to last 10 times as long to pay out. Since I figure to get at least 2 years out of mine and I'm almost 59, I'd BREAK EVEN at age 80.

I hope they work great, but I can't see the advantage. Ask me again in 20 years.

John
One of the few advantages of getting old; you wear out before all the stuff on the boat does.
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Old 02-06-2011, 09:23   #354
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

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Gael,

Nice going ! Alarms are our friends...:-)

Smooth sailing!

Hi,
Just a question for all folks around.
I'm using 2 24V/130Ah packs since October2010. No I want to refine the measurement and performances. Every pack has it own battery monitor from Victron and I can set several parameters.
One of them is the charge efficiency ie for 10Amp loaded in the bat' you can use only 9Amp, so 90% efficiency.
Does someone has a solid number for CALB (former Sky Energy)cells?

thanks in advance
Gael
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Old 02-06-2011, 12:36   #355
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

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Originally Posted by gael View Post
Hi,
Just a question for all folks around.
I'm using 2 24V/130Ah packs since October2010. No I want to refine the measurement and performances. Every pack has it own battery monitor from Victron and I can set several parameters.
One of them is the charge efficiency ie for 10Amp loaded in the bat' you can use only 9Amp, so 90% efficiency.
Does someone has a solid number for CALB (former Sky Energy)cells?

thanks in advance
Gael

I don't have a number, but I think that the Perkerts Quotient is close to flat for these, something like 1.0x, where X is the unknown number. When I (Finally) get my LIFEPO4 bank in place, I think I will start by programming the link 10 with 1.05, and see how that matches up with reality.

Chris
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Old 02-06-2011, 14:31   #356
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

I've been using 1.01-1.02 on the Peukert's, and 99% (as high as you can go) on the Victron monitors. That's been working fine.

Under very high loads (>200A, depending on bank size) perhaps the Peukert's could be higher, but it's so close that it will take time to tell what the "magic number" should be.
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Old 02-06-2011, 14:35   #357
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

Regarding CALB/SE cells; note on the charge-discharge graph below the amps in/out was something like 99.7% efficient...virtually 100%
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Old 03-06-2011, 11:10   #358
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Re: LiFePO4 Batteries - Okay, Tear Me Apart ;-)

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Regarding CALB/SE cells; note on the charge-discharge graph below the amps in/out was something like 99.7% efficient...virtually 100%
Hi,
thanks for the link. I got this diagram from Genasun/Alex last year but I may be a bit pessimistic in my interpretation.
As of today, I have set the Peukert expo to 1 and the CE to 90%; So I'll keep in mind this is pessimistic. Anyway, I just starting this calibration and not yet close from these "magic number". I guess Chris has the same approach.

I have defined several profiles as "marina" "mooring" "cruising" with an averaged user-time per profile per function. The most demanding are the watermaker(25Amp) and the fridge (3Amp).
The computed consumption per day is 60Ah and a solar pannel give me 15 to 20Ah ( I'm now in Las Palmas - Grand Canaria) . The experience shows that we stand for minimun 6days, still with bat's above 25.5V, w/o crnaking the engine.

So I'll come back to you when I'll got some consolidate data's

Cheers

gael

Ps Chris, thanks also for your answer!
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Old 27-06-2011, 19:12   #359
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Re: LiFePO4 Batteries - Okay Tear Me Apart ;-)

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Greetings everyone!

I come from DIY Electric Car community where we have used LiFePo4 cells for last couple of years. This is wonderful technology and it beats Lead Acid hands down. Subject of BMS has always been shrouded in a mystery, which deterred many people from these batteries. Many companies make super expensive and complicated BMS systems, but it doesn't have to be either complex or expensive.

As I built my own electric car with LiFePo4 cells, I also designed simple and affordable BMS, which I am now offering for DIY EV market. One of my customers asked if my BMS can be used in marine environment to replace house banks of Lead Acid batteries. Sure it can, its very flexible and simple to integrate with 4 LiFePo4 cells for drop-in replacement of 12V Lead Acid battery, or 8 cells to replace 24V battery bank, etc.

I am attaching wiring diagram here for drop in replacement of 12V Lead Acid battery for a house bank. Also here is the link to my BMS site, where you can find user guide and ordering info.

As for cells, Thundersky and SkyEnergy are 2 popular names, but there is also HiPower which has a new cell model competing with others. I am curently awaiting a test batch of new HiPower cells to confirm their quality. I am working directly with factory in China and planning to bring those cells to US to offer complete kits for marine and EV use.

I have decent experience with LiFePo4 cells by now, so I hope to be able to help your community here if you allow me.

Thanks



Attachment 13872
Hi Electric1, I was overwhelmd to find your post on here after a very lengthy search on LiFePO4 info. Cutting a long story short, I'd like to get your opinion on my setup. I have ordered 8 x LYP400 ThunderSky batteries that is suppose to arrive any moment. I have a "cruiser" but not on water. I cruise on land in a house bus. I have a 12v 600Ah flooded LA housebattery pack that is stuffed and will be replaced by this Lifepo4 set. However, I do not have a BMS and would like to get one. Also, a major concern is I will have 2 banks of 4 cells each, connected in parallel to give me 12v 800Ah. Will I need 2 chargers, one per bank? Will I need 2 BMS'es? Will I be able to use 2 isolated chargers (Ctek XS25000) in parallel over both banks or is it better to have a charger on each bank?
Hoping to hear from you soon.
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Old 27-06-2011, 20:09   #360
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Re: LiFePO4 Batteries - Okay Tear Me Apart ;-)

Hi Fastcat I have been thinking about the KISS factor for years because I have gone way past that this is OK because most of my systems are easily found just about anywhere # I would love to see you get any help with the spaghetti ( Photos of battery bank ) in Fiji or the Magellan Straits or even here in Cairns.
I am not against progress but we are getting pretty good with our systems now ( Wind. Solar. LEDs and big reliable Alternators and computerized regulators) and our footprint is getting pretty low as a Cruising Sailor . Have you asked about the disposal of these batteries after 20 yrs or are they just dumped in a desert like NUKE Waste

I hope that all the specs come up as hoped as I will love to see your results but after 20 yrs dont know if I will be still here

Best of luck with your trials I am sure we will all be watching Cheers Jacko
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