Hi MArk , the 2c discharge test is done just for a second or two, We use a carbon pile battery tester for this. if we do not get close to the 180 amps, then it might not be a keeper.

I would go with a 6-8 amp rc charger.

Brian

---In electricboats@yahoogroups.com, <mark.internet@...> wrote:

Brian
Could you explain this
we charge to 3.4 volts do a 2C discharge test
Discharge at 180A? for how long? Also what would be good to use to pull 180A?

So, if I use an ImaxB6ac unit.
it says it can discharge at 1A and charge at 1-5A.
So I could connect 1 cell and it would take 90 hours(if the cell is in real good condition) to discharge.
Then another 18 hours to charge up again.

Could I use it to charge the cell from completely dead(0.0), or am I best to keep using my bench power supply to slowly charge them back to life.
If the Imax really puts out 5A, it would be 10 times faster than my bench supply.

Also, I am able to set my bench supply as CC and set to 5A, but the voltage rises to about 12 Volts, I suspect that would not be a good thing though.

Thanks to everyone for their help on this.

From: "mainfuse@..." <mainfuse@...>
To: electricboats@yahoogroups.com
Sent: Friday, November 22, 2013 2:10:00 PM
Subject: RE: Re: Re: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

These cells are charged when they reach 3.34 volts , charging higher is a surface charge and the voltage should climb from 3.4 to 4 volts fairly fast.In testing Older or abused cells , we charge to 3.4 volts do a 2C discharge test , then measure and record the voltage. Let them set for 2 weeks, if the voltage is still holding the recorded voltage , it might be a good cell.If there is a internal short the voltage will drop over time. Next test would be a complete discharge test to measure ah. I like the RC charger/dischargers that one can buy from Hobbyking.You can set the charge voltage and current . You can also use them to cycle the cell to see just how much capacity you have.

hope this helps some, Brian Hall

thunderstruck Motors

---In electricboats@yahoogroups.com, <mark.internet@...> wrote:

I'm so confused.
I looked more online and found this page http://gwl-power.tumblr.com/post/556594132/faq-3-2v-lfp-cell-initial-charging
it was in reference to these batteries -

GWL/Power SE60AHA - Lithium Cell LiFePO4 (3.2V/60Ah)

http://www.ev-power.eu/CALB-40Ah-400Ah/SE60AHA-Lithium-Cell-LiFePO4-3-2V-60Ah.html

FAQ: 3.2V LFP cell initial charging

Question: How should new cells 3.2V 40AH, 60AH, 90AH, 100 AH, etc. be formed before first usage?

Answer: The new 3.2V LFP cells delivered from the warehouse are partially charged. However before the first use, it is essential to charge each cell to full capacity. The initial charging should be done with the charging current set to less than 1C (typically 0.5C), till the voltage level of 4.0 V is reached.

There is no other need for LFP 3.2V cells to be formatted or otherwise specially prepared for the use. After the first charge to full, the cell is ready to be used for use.

The above charging rule is also applied to the initial charge after the cell has been unused or stored for a long time. If not used more than 1 month, it is recommended to make again an initial charge to full.

Important: if you plan not to use the cells for a long time, before storing you must charge cells to full. In the case of storage longer than 1 year, it is required to recharge each cell after 12 months to full.

Posted 3 years ago

From this it would appear I should try to push these batteries to 4.0 Volts.

I am currently pushing .24 A at 3.7 volts and the battery is up to 3.26 Volts

Mark

I also read on another page to not use a BMS, but bottom balance?

so many different opinions

From: oak <oak_box@...>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Thursday, November 21, 2013 8:30:15 AM
Subject: Re: Re: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

Mark,

I'm trying to rig up something similar, except automating it with a couple of Arduinos.

My plan is to use 12 Car headlight bulbs as the load.

I'll use 12 car relays (rated 15A, for lights or horns) to switch the load or the charger (power supply) to the batteries.

The Arduino can monitor the battery voltage, charge the battery up, disconnect the charger / power supply, monitor the resting voltage, apply the load and monitor battery drain, then disconnect the load, rest a bit, and start the charging process all over again.

I'm using a LCD shield to tell me what's going on (if I don't want to have a netbook or laptop connected), and all data will be collected on a SD card shield attached to the Arduino.

So.... If I get this set up, I can try different batteries, and plot all the data.

Once I've got it all working, a similar set of Arduinos / chargers will go out to the boat, and will then be able to tell me everything I want to know about how my batteries are doing, and the load from my motor!

It's just painfully slow progress getting everything set up, and the code written and debugged, etc....

If only I didn't have to go to work, I could get a LOT more done!!!

John

From: Mark F <mark.internet@...>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Thursday, November 21, 2013 10:17 AM
Subject: Re: Re: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

The battery seems to be taking a charge.
I guess if I only give it .5 or less of an amp on a 90Ahr battery It will take over 7 days to completely charge.
with my charger only putting out or battery only taking .25 of an amp, it would take 14 days to charge.

Here is what I have found this far.

LIFePo4
constant voltage 3.5V
time        amps/volts        Volts
08:00            0                    0.0
8:30           1.49 A             .97
9:00            1.14A            1.52
9:30            1.02A            1.72
10:00        .91A            1.91
10:30        .78                2.13
11:00        .67                2.32
11:30        .59                2.45
12:15        .56                2.50
13:00        .53                2.54
13:30        .52                2.56
14:00        .51                2.59
14:30        .50                2.60
15:30        .48                2.64
16:00        .47                2.66
16:30        .46                2.67
17:30        .44                2.70
18:15        .44                2.74
tuesday
08:00         .28                3.00
09:00        .28                3.00
19:00
Wed
08:00        .18                3.15
16:00         .17                3.15

changed charger to 3.7 Volts from 3.4
1700        .32                3.16
20:00        .31                3.18
Thursday
08:00        .25                3.24

I am hoping to get 4 batteries charged to 3.5Volts and then connect them to an inverter and run a few light bulbs(load) to see my AH(at a reasonably light load)

I have done this with my NIMH batteries to see if they are all close in performance.
I connect the inverter and on the A/C side I connect a string of lights and also an old school analog clock that is powered by A/C.
When the inverter brings the batteries down to 10.5 Volts it shuts off. The clock stops and I can see my Ah.

I hope the LiFePo4's are good down to 2.625 Volts.

If this works well, I may have these batteries ready for my boat by spring:)

Mark

From: Mark F <mark.internet@...>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Monday, November 18, 2013 9:37:16 AM
Subject: Re: Re: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

After removing more batteries, I found one that was actually installed as a single with the expansion plates on it.

I have connected it to my bench power supply 60Volt 5 amp adjustable CC or CV.
I have set it at CV with 3.5 V as the ref.
I connected a meter at the battery to check voltage at the battery.

start 0.0 Volts
1/2 hr   charger sending 1.49A   voltage at cell .97
1 hr    charger sending 1.14A   voltage at cell 1.52
1.5                                 1.02                            1.72

cross my fingers and hope for the best.

I suspect they will be dead, but its worth trying to bring them back to life.
If they come back with reduced AH, I would be happy.

Mark

From: "boat_works@..." <boat_works@...>
To: electricboats@yahoogroups.com
Sent: Sunday, November 17, 2013 8:53:40 PM
Subject: RE: Re: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

I charge my prismatics at about C/9 (21A). They don't swell at all, but then I am careful not to overcharge them.

-Tom

---In electricboats@yahoogroups.com, <mark.internet@...> wrote:

I purchased the bike with these batteries.
I suspect there was a drain on the system as a whole as all the batteries are 0 Volts.
I have taken one and tried charging it slowly with about 1 amp and it has climbed to a .5 volt after 1.5 hrs.
When the batteries were in the bike, they had aluminum brackets on the sides of the strings.
Is it ok for me to charge these slowly without the brackets, or do I risk the batteries expanding or worse?

Thanks for everyones help.

From: "boat_works@..." <boat_works@...>
To: electricboats@yahoogroups.com
Sent: Tuesday, November 12, 2013 9:42:22 PM
Subject: [Electric Boats] RE: testing used Thundersky 90AH LFP90 Lithium Iron Phosphate Batteries

Testing is easy:

Check individual resting voltage.

If near 0V they are probably toast, but you can try to gently charge them (a couple amps), and see if the voltage rises during charge. If not, they're goners.

If they are 2V or more you can charge them to about 3.5V per cell. This is almost a full charge. Resting voltage should be around 3.35V

Once charged, either:

1. Time the discharge into a constant load (lights, heater), measure the current, stop the clock when cell measures at 2.5V under load (or maybe 2.8V or bit more if you want to be conservative), so you can calculate the Ah capacity of the cell.

2. Apply a load, and monitor the Ahs consumed with an Ah counter (LinkPRO, JLD404, etc.). Keep an eye on the voltage., stop test at 2.5V or so.

I'll bet that if the sellers of the car say the cells are bad, they are bad.

-Tom

---In electricboats@yahoogroups.com, <mark.internet@...> wrote:

I am thinking of purchasing a vehicle with these batteries.

They say their pack is dead.

Any suggestions on how to test the pack or cells and what to worry about if they are used batteries.

Or should I just consider the pack bad and recycle them?

Thanks