LIFEPO4 from Ebikes.ca

[recumbent]

Oh wow !!.. those are the same cells i got from FalconEV, as well as Deepkimchi and Oatnet.

Did they keep near their amp/hr rating after the first season?

I've tried to balance my pack twice now but cannot get them barely above half the distance as when they were new, 3,000
km ago. And yes i torqued the nuts, but only one was loose. Also one cell keeps lower voltage than the rest and three keep much more than the others.
Clearely The BMS is not up to the task, hope Gary's BMS system works to fix our problem, i'm optomistic because it appears to be a ballancing issue, they do not heat-up or anything like that.

Justin told me that they are getting a better BMS from the same company to hopefully fix our problem, one way or another we will get these battery packs balanced.

 

[swbluto]

Oh wow !!.. those are the same cells i got from FalconEV, as well as Deepkimchi and Oatnet.

I torqued the nuts as much as i dared then used hot glue to secure the whole thing together and prevent the nuts from backing out.

They make "locking nuts" for that purpose, no?

 

[OLIVIER]

Problem not solved! After charging overnight, pack voltage is only 40V fresh out of the charger. Charger puts out about 45V.
I dont have a cycle analyst so I never checked the actual capacity, but when new, my pack was at 44.8V and I could easily ride 30km.
Any suggestions?

 

[Ypedal]

Is the BMS still attached ?

If one cell is lower than the rest, the bms may try to lower the other cells to that level, and depending on how the bms/charger interact, the charger may or may not kick back in to bring the whole pack voltage backup to full...

ie: your entire pack is only as good as it's weakest cell.....

My cells came without BMS, or charger( well.. i got chargers but lets not even go there )

 

[sparky]

I rode my bike today and it is awesome!!!
It is my first time on an ebike and the feeling is really great. The controller is programmed for 32 kph and I was going at that speed all the time! It felt really fast!
It was raining and my custom made fenders worked perfectly. Later this weekend I should do a range check.

What motor are you running... and eZee hub or something else?

 

[OLIVIER]

I have a 36V-500W Goldenmotor, on the rear wheel.

 

[OLIVIER]

Latest update:
After a full night of charging, I disconnected the BMS and checked the cell voltage. Each cell is at 3.35 V precisely. Total pack voltage is 3.35*12=40.2
Question: is my pack fully charged? How can I know besides riding until the BMS cuts out?

I think I understood what was happening: Due to the bad connections at the cell terminals, the BMS was sensing a low cell voltage and was shutting down.

I will ride again soon and report.
Olivier out!

 

[Johnbear]

Hi, I have a couple of lifepo4s, not from ebikes.ca, but the cells should read at least 3.65 volts fully charged for a total of 43.8v hot off the charger. Check the output of the charger and see what it is. They can be around 43.8 - 46v. Good luck!

 

[Ypedal]

Using Voltphreak chargers, the cells go " green" at 3.6 / 3.7v .. then float up to as high as 3.99..

However, as soon as you load them up they drop to 3.2 / 3.0v... i don't know how many more mah each cell will absorb between 3.4 to 3.7v but it's not much.

 

[recumbent]

My 48 volt pack charges to 51.8 volts, from the charger that max's out at 55 volts. But if left on the charger overnight, the BMS balances the batteries to 49.8.

The lowest cell was 3.26, and the highest was 3.70 before i balanced it using a light bulb/w aligator clips attached, and an old cellphone charger/w aligator clips.

I used to have a range of 40km new, now I only get about 30km. I doubt these LIFEPO4 batteries will get 2000 cycles. But i haven't lost hope yet, a good BMS might save us from doom.

 

[Deepkimchi]

Hello Ypedal - back from vacation in SC. The "came without BMS" - main point is that he advertised it to be with a BMS then did not send one.

One cell of my battery pack is acting strange. Sometimes it seems okay, then other times it is lower than the rest. Still, even when that one cell is okay the pack seems to sag more under load.

DK

 

[OLIVIER]

I went to work this morning with my ebike and no problems!
It seems that loose connections was my battery problem. Fully charged pack voltage is about 40V. This seems low to me, only 3.33 volts per cell.
There must be a better way to secure cell terminal connections, like using lock nuts combined with bellville washers for example.
Anyway, I am back on the road! 8)

Go Justin Go!

 

[cycle9]

@Recumbent

I saw your post from about a month ago. I have been working with and diagnosing several of these packs for customers, and have come to several conclusions:

1. The BMS programming is not necessarily correct (at least on the ones we got, I am not sure about the ones from ebikes, but I bet they are the same). Basically, the problem is that the "bleed" function which equalizes cell voltage is only active during charging, but not once the pack has reached over-voltage condition (which means any one cell over the cutoff). Therefore, things can get out of balance after a while and never fully re-balance because the active charging period is not long enough for full cell equalization. I've been reprogramming the BMS units with some success to actively bleed to ~3.45 V even when not charging.

2. Some of their cells go bad. I've replaced several in our packs already. The worst one had a resistance of 0.25 Ohms, so as soon as the current hit > 7A, this cell voltage would drop and the pack would cut out. Once I replaced the bad cell, all was good again.

Anyway, if you are getting reduced range/mileage out of your pack, you should definitely contact the folks at ebikes.ca, they will certainly help you out.

Best regards,
Morgan

 

[recumbent]

2. Some of their cells go bad. I've replaced several in our packs already. The worst one had a resistance of 0.25 Ohms, so as soon as the current hit > 7A, this cell voltage would drop and the pack would cut out. Once I replaced the bad cell, all was good again.
Anyway, if you are getting reduced range/mileage out of your pack, you should definitely contact the folks at ebikes.ca, they will certainly help you out.Best regards, Morgan

How do you check for internal resistance?

I have a good digital multi-meter with ohm scale's, but afraid will burn the meter if i touch the battery terminals with meter in ohm scale. Don't know why i think this.

Thanks for the info Morgan, the batteries are surprisingly close to the same voltage when charged for a couple hours after green light.

 

[OLIVIER]

I am now running without the BMS. All cells have the same resistance and my range is greater than my commute, so I dont know the max. I commute 22km.
I am monitoring the cell voltage closely. If I find a cell with a low voltage during the constant voltage charging phase (~3.6V or less), I unplug the charger and boost that cell with a single cell charger. After my commute, all cells are around 3.32V. Fully charged pack is now 45.5 Volts fresh from the charger.
I now did 2200km with that pack with no measurable loss in performance. Thats about 100 recharge cycles. Its the charger that is slowly dying! The fan will have to be replaced soon... My brakes are also just about dead... I need to find a bike with disk brakes and suspension for next year. The cells themselves seem rock solid so far
I am now a lithium addict! 8)

 

[chvidgov.bc.ca]

Hi Olivier...I'm just approaching the 1000 mile mark on my 36V 12Ah Lifpo4 pack from ebikes.ca, and I've been following your thread with interest, noting the possibility that my pack could become unbalanced. However, after 37 cycles (most of them shallow), my fresh-off-the-charger is holding well at 45.3 volts. Could you tell me at what voltage lower than that that I might be worried at. Anyways, so far so good...I am attempting to "baby my baby".... I guess I've been averaging about 3 miles per Ah so far, mostly short range commuting, with one trip up to 44 miles. Do you know if they are still planning on getting a different BMS for these? Thanks. I picked up a 48V 8Ah Nicad for my next bike, I'm thinking I can bypass a generation of battery chemistry and maybe go to the new Toshiba supercharge ion (Scib) in a few years. Cheers.

 

[OLIVIER]

chvidgov... I knew I had problems when the charger was putting out 45.5 V but the voltage at the battery was only ~40V. The BMS was not letting the juice flow.

 

[dnmun]

recumbent, the internal resistance number is derived from the delta voltage divided by delta current. it is a derived number, a function of the ability of the current to get out of the battery, not like measuring resistance in a passive device.

we did a buncha IR calculations over on dr basses headway thread.

 

[cycle9]

Sorry for my delayed response.

The easiest way to do this is if you have a shunt-based current meter like Watts-up or Cycle Analyst. You will need two different resistive loads, with a different enough resistance value that they will draw substantially different currents.

For example, you can use an old stove element as one of your resistors (see picture), then put two of those stove elements in parallel as your second resistor.

Then, connect your battery pack to the first resistive load, R1. Measure the current, I1, and voltage, V1.
Next, connect your battery pack to the second resistive load, R2. Measure the current, I2, and voltage, V2.

You can then calculate internal resistance using Rb = (V1-V2)/(I1-I2), where Rb is the resistance of the battery (i.e., the delta resistance).

Now, with the packs that we and ebikes.ca have played with, there's a BMS that actually has a serial port, which allows individual cell monitoring (voltage only). I have used that feature to diagnose problems with particular cells, by watching which cells have bigger voltage drop when a load is connected. But to get to the BMS in these batteries requires taking the pack apart... And, then you need special software to actually monitor things....

Best regards,
Morgan

How do you check for internal resistance?

I have a good digital multi-meter with ohm scale's, but afraid will burn the meter if i touch the battery terminals with meter in ohm scale. Don't know why i think this.

Thanks for the info Morgan, the batteries are surprisingly close to the same voltage when charged for a couple hours after green light.

 

[cycle9]

chvidgov... I knew I had problems when the charger was putting out 45.5 V but the voltage at the battery was only ~40V. The BMS was not letting the juice flow.

I can tell you what is happening here (and you're right, it's not a good sign).

The BMS monitors all cells for max voltage (programmable, but usually 4.0V). Any time one of them reaches 4.0V, the BMS closes down the charging FET, so the charger things the pack is charged (but it is not!).

So, what happens when your pack becomes unbalanced is that a single cell may reach 4.0V and shut down charging, while all the rest of the cells are still lower voltage.

For example, if you had a 4-cell pack, and they were balanced, the charging would shut down when they are all 4V:
V = 4 + 4 + 4 + 4 = 16V total

Now, if you have that same 4-cell pack unbalanced, so only one is 4V and the others are 3.3V, you have:
V = 4 + 3.3 + 3.3 + 3.3 = 13.9V.

That's why the pack reads lower voltage after charging. It is a very easy way to diagnose a mis-balanced pack.

For a 48V pack, the above effect is amplified because there are 16 cells. (12 cells for 36V)

In our experience, some of these BMS units were not well programmed. They don't actually bleed the cells down after charging has stopped. So cells can get more and more out of balance. For the few that we have sold to customers, I've ended up going back and reprogramming each BMS to prevent this problem. This BMS may work ok when correctly programmed, but IMHO the new one from Gary is superior (but also much more costly to get set up with).

I hope that helps!
Morgan
cycle9.com

 

[chvidgov.bc.ca]

Well, it seems I was overly optimistic that my pack 36V 12Ahr from ebikes.ca would remain balanced.

I was fooled by the terminal voltage of 45.3 on the CA which is about right (mean of 3.77V) and thought that meant that all of my cells would be the same, but now I find a range of cell voltages in my pack from 3.9 down to 3.35 (two cells) on a full charge, and I am getting repeatable premature cutouts at 8.4 Ahr.

At cutout, the lowest cells are around 2.9 volts,and the others are about 3.32 It seems that the BMS won't effectively rebalance the pack, even after 10 hours on the charger. As you mentioned, the BMS doesn't seem to bleed lower after hitting the overcharge max on the max cell, to enable the low cells to catch up in the charging process.

Justin has helped me by recommending a charge of each cell separately, up to 3.7 volts, so I am aquiring a YESA single cell charger (3.9V/1amp) from ebay/comcyleusa, which is around 30 Canadian landed in Victoria after shipping.

I am hoping that a new BMS will help, when it becomes available, but in the meantime I am hoping that I can manually rebalance the pack myself to restore the full 11.5 Ahr before LVC that I was encountering when I got the pack. I haven't done anything hurtful to the pack otherwise, that I am aware of...as you say, it seems hopeful that these packs can get balanced <somehow> manually if necessary, but they don't seem to stay balanced. This seems to fit the documentation on ebikes.ca of their problem with a low voltage cell in a pack, which reduced it to 9Ahr, which was restored to 12Ahr by manual intervention... also I'm wondering if it is easy to "reprogram the BMS"...and how to do it? In the meantime, using my Nicads more...

Chris

 

[Ypedal]

You can get 2 amp single cell chargers from http://www.voltphreaks.com , the latest batch is not as nice as the 1st one's but for ballancing purposes it does the job.

If you could bench test the pack, bypassing the bms, it's safe to go down to 2.5v per cell ( absolute max 2.1v ) it may reveal something... ( bms may be cutting in early )

 

[chvidgov.bc.ca]

Thanks Ypedal...actually, I mispoke, the YESA models are also 2 amps. I'm wondering if it is true that I could charge the whole pack with one charger, if I connected all the cells in parallel, and they would all end up perfectly identical in their terminal voltage - except that it would take about 72 hours? So I could take a few days off and come back with a perfectly balanced pack? Rather than just topping up the low ones? So if I rewired my pack as 1s12p with switches to toggle it to 12s1p like it is now when I want to ride, I could get a "slow but perfect" balancing capability that I could use now and then? Interesting idea...

 

[Ypedal]

Possible.. not practicle..

Better to bulk charge the pack.. then top off each cell with a single cell charger for a complete full ballanced charge.. :wink:

 

[Ypedal]

Hey.. question for you since you have the same cells... do you smell a strong solvent odor from the pack ? kinda like nail polish remover or strong rubbing alcohol type but sweeter..