LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[Maine Sail]

Originally Posted by noelex 77

If the connection posts swivel outboard aluminium is a great conductor and the resulting short would be spectacular.

I am way ahead of you... Going to be 1/4" black starboard.

Originally Posted by noelex 77

My vote is for red anodising.

One blue, one red vote...!

[deckofficer]

No, you forgot me, 2 blue, 1 red.

[Maine Sail]

Originally Posted by deckofficer

No, you forgot me, 2 blue, 1 red.

Sorry!

[CharlieJ]

Blue.

[hellosailor]

Mona Lisa and spectaculars aside...Maine, I think you really should replace all that aluminum with teak, drilled for the rods of course. Maybe ornamentally carved, going for the Steampunk look? And a nice frosting design on the top panel?

Aesthetics! Points for aesthetics! Somewhere in the Khyber pass, some artisans are saying "Bare unornamented metal? No wonder the US is in trouble!"

[durundal]

Hi everyone,

I'm getting ready to bite the bullet on a battery for my Farrier 22 (still fairing, but the time has come to start getting all the bolt on parts) and I am trying to figure out what exactly I need. I am looking at the 60 Ah Winston 12V combined cell as sold in the US by Balqon.com, or building a pack of 4x 60 Ah cells (Winston or CALB likely). The 12V unit has advantages in my mind for simplicity and being self contained with fewer points to short things out to accidentally, and the prices are the same with the exception of needing strapping and connecting links for the individual cells.

Power will be from a 50W outboard alternator and maybe a little solar panel down the road. Loads are all low, all LED lights and iPad charger, the biggest current draw will be an autotiller so I shouldn't be regularly drawing much more than 10-20A, if that. It sounds like an undervoltage cutoff is required at least, I am assuming a MPPT solar charge controller can be selected that would limit input voltage enough to stop charging before 4V/cell, but is there an equivalent controller for an alternator? Or is one even needed? I am concerned about having the battery heat up enough to start a fire (of itself or stuff around it), not dying an early death capacity-wise.



I also haven't stumbled on anywhere selling pre-made copper jumpers or the compression stuff for the individual cells, is there somewhere out there or is it all DIY? Is there a preferred vendor for the voltage cutoff switches as well, and any reason to not want to use a solid state relay for the cutoffs to reduce the number of mechanical connections to go wrong?


A mechanical engineer trying to do electrical stuff,
Andy

[durundal]

Oh, and for general information, here is some info on the 12V battery I got from Steve at Balqon after they opened up one:

Andrew,
The 12v Battery consists of (4) 60 ah batteries in series with a post on the main positive and negative coming through the top. By having some sort of alarm on these cells would let you know when the batteries are getting to charged or getting discharged to low.

Steven Barhanovic
310-326-3056

[deckofficer]

Andy,

I wouldn't go the expense of a MPPT controller if you only plan on one small solar panel, just use a small charge controller. The 50 watt output of your small outboard alternator will have a LA voltage set points and won't be capable of over charging your LiFePO4 pack because it will taper down to nothing before the upward swing of the charge knee of these cells.

If your solar panel will be 65 watts or less, and you want the features of MPPT, and designed for LiFePO4, check this unit out......
http://genasun.com/all-products/sola...ge-controller/

There are others better versed on this than me, so stand by and they will offer up some suggestions.

[T1 Terry]

Originally Posted by durundal

Oh, and for general information, here is some info on the 12V battery I got from Steve at Balqon after they opened up one:

Andrew,
The 12v Battery consists of (4) 60 ah batteries in series with a post on the main positive and negative coming through the top. By having some sort of alarm on these cells would let you know when the batteries are getting to charged or getting discharged to low.

Steven Barhanovic
310-326-3056

If you want to keep it simple, a jusi cell logger available from hobbyking or most hobby stores and a smoke alarm wired arcoss the alarm terminals to the test button terminals.
set the logger for max 3.6v and min 2.8v and you won't damage the cells. I think I'd go for the 90ah unit myself, gives you more spare to play with so the low cell alarm isn't reached, the cycle life will be longer then. if you want a method of controlling the max cell voltage but still having the solar and outboard charging, a dump load equal to or slightly more than the total charge rate, maybe a 12v hot water heater element, if you have no use for the hot water then waste it into the ocean.

T1 Terry

[downunder]

How about as an option using a Genasun Lithium controller (price $599) for your put together battery pack.


http://genasun.com/all-products/gena...tems/gli-cp-1/

Looks as if Genasun sell them seperatly. Certainly more expensive but nothing like buying the full genasun 360AMP pack for $6,399.

Paul who owns Sulaire a St Francis 50 recently fitted the Genasun batteries.

Cheers

[downunder]

Found a link on Genasun website.

Suliere 50 Catamaran | Genasun

[downunder]

Originally Posted by Maine Sail

I am way ahead of you... Going to be 1/4" black starboard.




One blue, one red vote...!

Blue will make it look like a genasun.

[deckofficer]

Originally Posted by downunder

Found a link on Genasun website.

Suliere 50 Catamaran | Genasun

After getting accustomed to Balqon's clearance prices running $0.20 per watt, Genasun's $1.21 per watt reminds me of pricing lithium for my EVs 5 years ago, then going with AGM.

[downunder]

Originally Posted by deckofficer

After getting accustomed to Balqon's clearance prices running $0.20 per watt, Genasun's $1.21 per watt reminds me of pricing lithium for my EVs 5 years ago, then going with AGM.

Its my understanding Paul had had so many electrical hassels with his vessel, could afford the genasuns and wanted a hassel free plug in system. He recons now he could have gone with less AMP/HRS it is so efficient.

[deckofficer]

Originally Posted by downunder

Its my understanding Paul had had so many electrical hassels with his vessel, could afford the genasuns and wanted a hassel free plug in system. He recons now he could have gone with less AMP/HRS it is so efficient.

Then Paul has found out what most who have followed this thread (and all that own LiFePO4) already know, and that is how ultra conservative LiFePO4 cells are rated.

A 220 a-hr LA is rated at a 20 hr rate, so in real world use (loads greater than 10 amps) is really about 160 a-hr, or at the recommended 50% DOD, a 80 a-hr battery.

By contrast a 100 a-hr rated LiFePO4 is still conservative even at a 1 hour rate, but at a 20 hour rate will give 165 a-hr. At 80% DOD, 132 a-hr usable.

220 a-hr LA in our service, usable 80 a-hr.
100 a-hr LiFePO4 in our service, usable 132 a-hr

Big difference, all due to how they get their ratings.