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

[goboatingnow]

Originally Posted by hellosailor

Dave, there's more than one Big Brand Name automaker who is, and has been, making "electric" cars that did not and do not use Lithium batteries of any kind.

Toyota Prius, possibly the most widely deployed. NiMh.

Tesla. NiCd.

Everywhere? Not lithium, not yet. The vote is still not in.

The Toyota Prius is a very dated design.

Dave

[bcn]

Toyota/Lexus is indeed the exception - staying with "a proven design".

Honda changed to LiOn with the latest Civic Hybrid version.

bcn

[gael]

Originally Posted by hellosailor

Dave, there's more than one Big Brand Name automaker who is, and has been, making "electric" cars that did not and do not use Lithium batteries of any kind.

Toyota Prius, possibly the most widely deployed. NiMh.

Tesla. NiCd.

Everywhere? Not lithium, not yet. The vote is still not in.

FYI Renault/Nissan work so far with Heter for LIPO packs.

I'm leaving on my boat with wife and 7mont baby since 2 years, cross the Atlantic this Jan' and presently mooring in English Harb' -Antigua.
I have 2 banks of 24V/130Ah _so 16 cells fron CALB and all BMS from Genasun .
Fridge with aerogell insulation , leds eveywhere, 100l/H watermater, SSB transmitter and a 2KW windlass. I use all of them w/o cranking the diesel.
As extra pwr source I have a single solar panel giving 4amps peak.
Average, we can stand for 5 days w/0 "noise"

So this technology works very well.

As lesson learned: I have underspecified the main alternator.Only a 75Amp leec-Neville. better a 120Amp for the 2 banks allowing a faster charge.
Never connect 2 banks in parralel. Use separate basic switches and a way to avoid "1 & 2".

rgds
Gael

[bcn]

Originally Posted by gael

As lesson learned: .........
Never connect 2 banks in parralel. Use separate basic switches and a way to avoid "1 & 2".

rgds
Gael

Reasoning? What did happen?

[deckofficer]

bcn,

You've been doing your research. +1

[mrm]

Originally Posted by hellosailor

Toyota Prius, possibly the most widely deployed. NiMh.

Tesla. NiCd.

Everywhere? Not lithium, not yet. The vote is still not in.

Uh, oh, quite to the contrary, Prius seems to be an exception to the norm and the majority vote seems to be in already. All new developments I am aware of use or plan to use Lithium based chemistry.

As for Tesla, quoting directly from Model S Specs and Standard Features | Tesla Motors :

Powertrain
Model S is a rear wheel drive electric vehicle. The liquid-cooled powertrain includes the battery, motor, drive inverter, and gear box.
40 kWh microprocessor controlled, lithium-ion battery
[...]

[hellosailor]

Sounds like the market is maturing. Which only leaves the question of BMSes. How fancy, how expensive. They're not just bolting up 3-stage "boat" regulators in those cars either.

[mrm]

Originally Posted by hellosailor

Sounds like the market is maturing. Which only leaves the question of BMSes. How fancy, how expensive. They're not just bolting up 3-stage "boat" regulators in those cars either.

And with boats this is much easier to address than with electric cars.

For one, we use strings of much fewer cells.

For two, we load the cells much less than cars do. In electric car the battery may be drained empty within two hours drive. In a boat, we usually size the bank to last a minimum of two days.

Both factors make for much easier battery management in boats, as there is significantly less possibility of individual cells getting out of balance.

[gael]

Originally Posted by bcn

Reasoning? What did happen?

If yours packs are largely unbalance there is serious risk for a large current surge which maigth blowup your switches or your wiring. I had just avoid the trap when I build the packs and play with the cells standing alone.....

For my 2 packs I have 2 T shapes switches, linked together with a 2mm rope. So these 2 swicthes canot be set "on" simultaneously.

rgds
Gael

[gscriba]

Love the idea of a LiFePO4 system. To summerize what would be good setup for a 40 foot live aboard sloop with an daily average use of approx. 120 amps - 12 volts.

• 400 amps (4 x 100 amp 3.2 volt cells)
• Approp. connectors to create a 12 volt pack
• High and Low volt alarms (brand?)
• Battery charger with customizable settings (brand?)
• Alternator with output 120 - 150 amps (for use on a approx. 40 hp diesel) with customizable regulator
• Alternative power supply: Solar - 125 watt panels x 2 if San Fran or further south (more if further north in PNW?). Panels side by side over the bimini wired in...oh boy, here we go...series or parallel?
• Solar regulator MPPT such as a Morning Star TriStar 45 vs 60 amp (room to grow)
• Wind generator? (trying to stay away from one if possible, but if I must...brand?)

Currently have installed house 420 amps 12 volt system (4 x 6 volt lead-acid golf cart batteries that are several years old); BlueSea VSM 422; 60 amp alternator with Balmar MC612 regulator; on the dock with shore power at present; no solar or wind generator.

What would you build, keeping simplicity in mind, but with the desire to upgrade to the LiFePO4 house bank?

Thanks.

[deckofficer]

I'm going with electric propulsion next time around, so my needs will be different.

1) 48 volt 400 amp/hr bank for propulsion and inverter
2) 48 volt inverter, 4800 watts output on the AC side
3) 14 KW diesel DC charger, 270 amps charging at 52 volts. Being DC, very efficient and light for a 14 KW output at 337 lbs.
4) As many solar panels as can be fitted, now that you can buy at $1.13 per watt instead of the over $5.00 per watt I paid for my current panels.

[senormechanico]

Originally Posted by gael

If yours packs are largely unbalance there is serious risk for a large current surge which maigth blowup your switches or your wiring. I had just avoid the trap when I build the packs and play with the cells standing alone.....

For my 2 packs I have 2 T shapes switches, linked together with a 2mm rope. So these 2 swicthes canot be set "on" simultaneously.

rgds
Gael

I was going to post the same reasoning, but am too much of a noob to these batteries to have "street cred".

[JoeFish]

Originally Posted by senormechanico

I was going to post the same reasoning, but am too much of a noob to these batteries to have "street cred".

Join the club!

A lot to learn, but I'm never so arrogant as to think technology can't improve so I'm learning. This thread is a great help.

[mrm]

Originally Posted by gscriba

Love the idea of a LiFePO4 system. To summerize what would be good setup for a 40 foot live aboard sloop with an daily average use of approx. 120 amps - 12 volts.

• 400 amps (4 x 100 amp 3.2 volt cells)

Umm... no, if you meant 400Ah you will need 4 cells of 400Ah each.

Depending on how you connect cells together (series or parallel) you can either add Volts or Ampere-hours, but not both at the same time - one of the two has to stay constant.

For example, assume you have 4 cells of 100Ah capacity and 3.2V voltage each:

• If you connect them in series (that is: plus-minus-plus-minus-plus-minus-...) you will get a bank of 12.8V and 100Ah capacity.
• If you connect them in parallel (that is: all pluses together and all minuses together) you will get an equivalent of a single 3.2V cell with 400Ah capacity.

[gscriba]

Oops. Yes, of course. 400 amps total (4 x 400 amp, 3.2 cells). Thanks for pointing that out. I would like to hear from anyone who is actually using the LiFePO4 as a house bank. What system would you build with the situation I described previously?