LiFePO4 Batteries - Okay Tear Me Apart ;-)

[DaveOnCudjoe]

I'm just catching up on this thread after some time away. In my situation, a single bank with 40 AH/day usage and 6amp solar charging and outboard motor alternator charging , what type of charge management would some of the more experienced users recommend? Dave

[Tinkerer007]

I installed my 200 AH Thundersky battery in the boat this weekend. There were a couple "uh-oh" moments like when I got the lights turned on but there was no current draw (The current was shown on the battery 2).

I pulled out 2 group 27 (~120 AH) flooded batteries, and for about the same weight as one of them installed the LiFePO4 battery.

The new battery is a little taller, but similar in size. I am not sure if I could fit two of them in my battery area.

We sprayed CRC Battery Protectant on all connections / connectors, and installed the Mini BMS, with an additional 500 A solenoid controlled by the Mini BMS.

I also have a Link 2000 to monitor the voltage and amps out and in. I did get the Puekerts effect variable set to 1.

When I installed the battery, I thought it was fully charged at 13.2 V. I started the engine and was please with the peppy starter action. I was pleased to see 41 Amps to the battery. The most I had seen previously with the two batteries in parallel was ~20 Amps. After 15 minutes the amps were down to 20 A and the voltage was up to 13.3 V.

I am excited to see how this behaves. I will be taking the boat out for a day race in less than two weeks.

I will try to add some picts...


56.5 Pounds...


Original batteries


LiFePO4 installed with Mini BMS and solenoid

[Intentional Drifter]

Very cool, Tinkerer -- we're all waiting to see how it goes and hoping for the best.

ID

[witzgall]

Tinkerer;

Did you make the cell packaging plates and bars, or buy them?

Chris

[Tinkerer007]

They were included with the battery.

The first picture is how the battery came out of the shipping crate.

[senormechanico]

Tinkerer007
I'm watching this with baited breath.
How much weight saved?
One of these days, I'm going electric hybrid.

[ctsbillc]

Yes, this is interesting. Hopefully the quality issues with these batteries are vicious rumours, or historical issues now corrected.

If your experiences are good, there are going to be a lot of folks following your lead.

Bill

[Tinkerer007]

I just weighed one of the West marine deep cycle 90 AH batteries and it was 53 lbs. So, for the similar weight I get 4 times the usable AH. 90 to 30 state of charge compared to 80 to 50 state of charge with the flooded batteries.

+ the charging seems to be more efficient, and there is supposedly no Pukerts effect. Basically you need to put in 1.3 amps for every one you get back.

I think the reliability issues with the batteries will be less likely to appear. Most of those reports are with the electric vehicles that can and do draw more than 1C. On my boat the largest draw I have is the starter motor @ 83 A. And that is not continuous draw. But even that is less than 1C of a 200 AH battery.

Part of my frustration with hte flooded batteries was that I did not understand how the starter was wired into the AB switch. I thought it was connected to the output, so the engine would start with which ever battery was selected by the switch. I found the to not be true when installing the new battery. The starter is hooked to the battery 2 terminal on the switch. This caused me to suspect battery one was dead, when it was not.

But I still could not even run the instruments, and GPS and VHF for a day of ocean racing on one battery.

[LiFeTech Energy]

Originally Posted by ctsbillc

It's wrong of me to single out China of course, but they are the big one. I suppose it's wrong to favour Germany over China also - China has never attacked us (sorry Lifetech).

Bill

It should make you feel better to know that the computer controlled cell manufacturing machinery and robotics which will manufacture our new cell is made in Japan.

[ctsbillc]

:-)

Thanks, I feel much better now.

I see the Euro has recovered a bit now Germany has donated generously to Greece. This does not help Euro exports of course.

Eventually China will be unnable to keep the Yuan artificially low , and then you will be playing on a level field.

Bill

[hellosailor]

Maybe someone can unconfuse me on thi:
All lithium batteries, including LiFePo, need to have the charging managed per cell, yes? Or not?
And if the charge management has to be per cell, then the nominal 12v recharging has to be...split up by the charge management system, and reduced down from 14v to about 4v per cell? How is that managed, brute force regulation? DC-to-DC downconversion?
I'm not seeing the bigger picture clearly here at all.

[Tinkerer007]

For a simpler system , I have the Mini BMS. There are individual PCBs on each cell. These will limit the current (up to .75 amps) to a cell as it charges, allowing the other cells to catch up.

Fancier BMS will manage the charge at the bottom as well (I think), but they are $100s of dollars.

I will be watching the cells to see how close in voltage they stay. When I got the battery, the cells were within .05 volts.

So, my plan is to charge with my regular alternator and let the Mini BMS manage the individual cells. My alternator only gets up to 14.4 volts, so I am not sure if I will be able to get a 100% charge, but it should be close.

[goboatingnow]

IAll lithium batteries, including LiFePo, need to have the charging managed per cell, yes? Or not?

Managed per cell definitely, but not neccessarily charged per cell.

IN reality, its debateable whether per cell level is needed for marine use. cell level management really developed in electric car use, where multiples of C are used in charge and discharge cycles and hence the cells can get out of balance and this can cause a cell to experience a HVC event.

My view is that with 1C or less out of balence is very unlikely to happen. Hence LVC and HVC events could be handled on a battery level. Even if cell level monitoring was done, it could simply flag cell level events rather then handling them.

I am currently designing some electronics specifically for boat power control and its a debate as to whether cell level or battery level control is needed. There is so little real experience of marine usage, yours will be watched with interest.

Dave

[LiFeTech Energy]

Originally Posted by goboatingnow

Managed per cell definitely, but not neccessarily charged per cell.
Dave

Dave has it spot on.

As far as cell balancing is concerned this can be achieved 3 ways-

1) As part of the internal battery electronics which will balance cells during charging (mostly). When combined with LVC and HVC protection this is then a complete BMS.

2) A separate cell balancer. This can be either an internal or external unit.

3) In some cases battery owners may not want the compexity of electronics and electronic components used in BMS and balancers. In these cases often single cell chargers are used for manually charging and balancing cells since each cell can be individually charged to capacity completely independently of all other cells.

The better/higher the quality of the cells used, the better the cells will stay in balance by themselves without any kind of BMS or cell balancing. This is due to less variation from one cell to the next in terms of-
1) internal impedance
2) true/measured capacity

For example I have been using a LiFePO4 engine starting battery in my Toyota Camry for almost 2 years now. This battery does not have any kind of BMS or cell balancing built into it at all. It only has LVC. The cells stay in balance well all by themselves because the cells are "matched" or "racing" cells so tolerance between all of the cells in the pack is very close which means that all cells charge and discharge at very close to the same rate and therefore any tendency for cells to get out of balance (for practical purposes) is non existent.

[gbanker]

can this new battery accept higher charging rates? does this new technology require that we upgrade our battery chargers or alternators to make full use of it benefits? if these batteries can accept higher charging rates and the charging methods are not upgraded, is there any benefit in terms of reduced charging times?