Homemade Battery Packs

[DrkAngel]

Tenergy 25.9v 2A charger - Next step in testing will be with my 25.9v, 26ah Lithium-ion Polymer pack.

Then, for a "real" trial I will run down my Li-ion pack to 4v/cell, then charge 1 bank to 4.1v.
Monitored charge, will then, proceed.

Interesting note about the Tenergy charger. Even after the charge light turned green, the charger continued to pulse voltage, fairly standard, except that the pulse dropped noticeably below the applied voltage. Battery voltage measured higher after disconnecting the power supply!?

Added note:
Strange was that the high and low pulses were both below the pack voltage after the charger was removed!
Probable explanation - Charger provide an extremely short duration higher voltage "spike" followed by a longer duration, lower voltage drain. (My $30 digital multimeter did not fully recognize the brief, higher voltage, charge portion of the cycle, due to low sampling rate, or buffers.)

Might indicate a balancing algorithm?
Charge-discharge-charge-discharge - cycles every 2-3 seconds.
Premise 1 - A lower voltage cell will accept charge more easily than one with a higher voltage.
Premise 2 - A higher voltage cell will expend energy more easily, (faster), than lower voltage cell.
Given these 2 reasonable premises, then the chargers, charge-discharge pulsing, would tend to equalize, (balance), Li-ion cells! ... ?

 

[liveforphysics]

Added note:
Strange was that the high and low pulses were both below the pack voltage after the charger was removed!
Probable explanation - Charger provide an extremely short duration higher voltage "spike" followed by a longer duration, lower voltage drain. (My $30 digital multimeter did not fully recognize the brief, higher voltage, charge portion of the cycle, due to low sampling rate, or buffers.)

On a charger with no "enable" wire to know when a pack is plugged in, it flickers on to see if a battery is there. If the current from that pack detection pulse is low enough(and we're talking roughly no current and for a very small amount of time just to detect a pack), it knows it's connected to a charged pack and turns off. If you were to swap an uncharged pack on the charger, when that little detection pulse hit, it would begin charging.

This enables the charger to save a small amount of utility power while sitting with a charged pack on it, where a normal meanwell charger just sits running outputting no current to the pack (because pack voltage equals output voltage, so it's impossible for it to continue charging), yet it still has the power supplies idle power being wasted as it sits.

Might indicate a balancing algorithm?

Nope, it's just checking if it's got a pack on it that needs charging. This is how the little flashlight battery chargers work, and pretty much every charger that doesn't have an enable pin to detect a pack.

Charge-discharge-charge-discharge - cycles every 2-3 seconds.
Premise 1 - A lower voltage cell will accept charge more easily than one with a higher voltage.
Premise 2 - A higher voltage cell will expend energy more easily, (faster), than lower voltage cell.
Given these 2 reasonable premises, then the chargers, charge-discharge pulsing, would tend to equalize, (balance), Li-ion cells!

Any current you pass through cells when they are in series goes equally through all the cells. No amount of charge/discharge (even though it's not charging or discharging, it's just checking if it has a low pack on it) can balance a chemistry that has a constant charge storage efficiency (like LiCoO2).

To get a cell to balance, you need a mechanism to enable it. With LiMnO4 (cell's prefixed with IMR), they decrease in charge efficiency as they approach the top of the SOC, so you can naturally find balance with healthy and roughly matched cells and enough cycles through the top end of the charge cycle. With LiCoO2 (like all laptop 18650's), they stay roughly even in charge efficiency through the whole range, with some even becoming slightly more efficient at charge storage with SOC increase. This is why every laptop batt etc has the added hassle and expense of balance taps etc.


If cells are perfectly matched for resistance and capacity, all aged the same, and you get no defective cells, then nobody would need a BMS or balance taps or balance chargers etc.

 

[neptronix]

I recommend that you prove this charger's balancing ability by hooking up the most disbalanced lipo or lico ( non-magnesuim hybrid, the explodey kind ) pack you have to it and let it charge to the pack's maximum voltage.

Make sure you get it on video

 

[DrkAngel]

Tenergy 25.9v Li-ion charger:

Lithium-ion Polymer 25.9v, 26ah pack charged nicely, also!
All banks of cells charged tightly within 1/100th of a volt, of the median 4.18v!

Previously described, "off balance" pack test, scheduled for Tuesday, when I'm back in the shop.

 

[liveforphysics]

Drain the pack down to empty.

Charge one cell bank with a single cell charger to full.

Set pack in a safe place.

Plug into charger, and enjoy.

 

[neptronix]

OK, now if you are going to do this test, use these following parameters:

Disbalance the cells like so:

Cell 1 & 2, charge/drain to 3.1v
Cell 3 & 4, charge/drain to 3.3v
Cell 5 & 6, charge/drain to 3.6v
Cell 7, charge/drain to 4.0v

Total voltage should be about 24v when you stick it on the charger.
Make sure to get it on video, including measuring the voltages before the charge, and after the charge.

And i take back the whole non-fire proof clause. Please do this in a fire proof area. I don't want you to burn your house or apartment down. Check out some of LFP's overcharged lipo videos on youtube to prepare yourself.

 

[DrkAngel]

I recommend that you ...

You run your test ... I'll run mine.

Drain the pa ...

Ditto.

 

[neptronix]

Drain the pack down to empty.

Charge one cell bank with a single cell charger to full.

Set pack in a safe place.

Plug into charger, and enjoy.

Even better.

 

[liveforphysics]

Drain the pack down to empty.

Charge one cell bank with a single cell charger to full.

Set pack in a safe place.

Plug into charger, and enjoy.

Even better.

Yes, its the test you run when developing a BMS. It finds faults in designs and concepts the fastest. If your BMS can handle it (and all the good ones can), then you know your system is solid.

 

[DrkAngel]

Enough already!
You two should take that sort of thing into the privacy of your own room ...

 

[DrkAngel]

Enough already!
You two should take that sort of thing into the privacy of your own room ...

Sorry! Didn't mean to be crude, but neptronix and liveforphysics were "tagteaming" each other in an, almost, obscene manner. I just got ... revolted.

If interested in this thread but don't like the "static" generated by those 2, at the bottom of the page you can choose "Sort by" "Author" and read the Drkangel posts!

 

[neptronix]

Enough already!
You two should take that sort of thing into the privacy of your own room ...

Sorry! Didn't mean to be crude, but neptronix and liveforphysics were "tagteaming" each other in an, almost, obscene manner. I just got ... revolted.

If interested in this thread but don't like the "static" generated by those 2, at the bottom of the page you can choose "Sort by" "Author" and read the Drkangel posts!

How are we tag teaming you?
You said you have a balancing charger. Either test it the way you would normally test a balancing charger or admit that you're wrong about it being a balancing charger.

We are asking you to verify what you have claimed.

 

[liveforphysics]

Enough already!
You two should take that sort of thing into the privacy of your own room ...

Sorry! Didn't mean to be crude, but neptronix and liveforphysics were "tagteaming" each other in an, almost, obscene manner. I just got ... revolted.

If interested in this thread but don't like the "static" generated by those 2, at the bottom of the page you can choose "Sort by" "Author" and read the Drkangel posts!

Sort threads by battery fantasy, or battery reality.

 

[DrkAngel]

Enough already!
You two should take that sort of thing into the privacy of your own room ...

Sorry! Didn't mean to be crude, but neptronix and liveforphysics were "tagteaming" each other in an, almost, obscene manner. I just got ... revolted.

If interested in this thread but don't like the "static" generated by those 2, at the bottom of the page you can choose "Sort by" "Author" and read the Drkangel posts!

How are we ...

Sort threads ...

Together Again! What a couple!

 

[Ypedal]

tho a bit sarcastic, you should apreciate that these guys are teaching you something valuable, your bulk charger will not ballance your pack, it is not a ballancing charger, if you think it is and have no understanding of it, it's a good thing that you are made aware of it ! :wink:

 

[DrkAngel]

tho a bit sarcastic, you should apreciate that these guys are teaching you something valuable, your bulk charger will not ballance your pack, it is not a ballancing charger, if you think it is and have no understanding of it, it's a good thing that you are made aware of it ! :wink:

Sorry, I never even claimed that it was a balancing charger!
I noted that it appeared to be maintaining balance in my batteries, (equalized to within 1/100th volt of 4.18v), multiple packs.
Further stating that I will test, through altered voltage variances, and monitoring, in an attempt to verify, or disprove, the possibility of active balancing.

If after a few more cycles it maintains equalization as well as it has been, on multiple packs of my, many years old, recycled, "worthless"LFP, "garbage"LFP "fecal"LFP cells, then, it is doing something better than what, liveforphysics claims that, the best charger-BMS could do!

 

[Ypedal]

Fair enough but if the packs end up perfectly ballanced, it's not because of the charger..

 

[neptronix]

tho a bit sarcastic, you should apreciate that these guys are teaching you something valuable, your bulk charger will not ballance your pack, it is not a ballancing charger, if you think it is and have no understanding of it, it's a good thing that you are made aware of it ! :wink:

Sorry, I never even claimed that it was a balancing charger!

Might indicate a balancing algorithm?
Charge-discharge-charge-discharge - cycles every 2-3 seconds.
Premise 1 - A lower voltage cell will accept charge more easily than one with a higher voltage.
Premise 2 - A higher voltage cell will expend energy more easily, (faster), than lower voltage cell.
Given these 2 reasonable premises, then the chargers, charge-discharge pulsing, would tend to equalize, (balance), Li-ion cells!

Me and LFP both pointed out that there is no way for this charger to balance cells.
Your corresponding posts seem to indicate that you thought it would balance them.
You even accepted a challenge to test whether or not it can balance.

So do you think that this charger is capable of balancing or not drkangel?
Yes or no?

My lipo cells come out equalized after dozens of non-balance charges too, only because they a set of matched cells in the first place.

 

[DrkAngel]

Fair enough but if the packs end up perfectly ballanced, it's not because of the charger..

Sorry, I never even claimed that it was a balancing charger!
I noted that it appeared to be maintaining balance in my batteries, (equalized to within 1/100th volt of 4.18v), multiple packs.
Further stating that I will test, through altered voltage variances, and monitoring, in an attempt to verify, or disprove, the possibility of any active balancing.

I have been building and using Li-ion packs for 3 years now, including 100s & 100s of charges, with multiple chargers(at least 6) and PCB/PCM/BMS's(at least 4) but this charger outperforms any of them, for maintaining equalization!
Deserves further scrutiny!

 

[DrkAngel]

My lipo cells come out equalized after dozens of non-balance charges too, only because they a set of matched cells in the first place.

My lipo and Li-ion cells come out equalized too, only because they were packs of my, many years old, recycled, "worthless"LFP, "garbage"LFP "fecal"LFP cells.

Sorry, I had determined to not respond to "them" but I couldn't resist!

 

[Red_Liner740]

Good to hear. I have some good news as well!

i assembled 6 6s2p packs and put them into an 18s4p battery pack....cells were not balanced but were ganged up as close to possible into individual packs... total cells = 72. 50.5v start voltage....capacity? who knows....they were 2.2 and 2.6 ah cells...so approximately 12ah with age? i dunno, its late and a long day and i cant think right now. just a note, as of now i dont have a way to charge the packs...i can charge individual cells using the ebay 18650 600mAh chargers but now that they are in packs i have no way....i have a balance 6s charger but no balancing leads so as of now thats collecting dust until i receive the balancing leads.

anywho, i assembled the bike, the wheel and threw the mini pack on the back rack and went for a test ride.

motor is a GM Magic Pie 48v 1000w system with the internal controller. 26" rim with 1.95" tire.

Top speed with wheel in the air is 45km/h according to my bike speedo but it hasnt been verified against a known source (just installed it yesterday).

anywho, in the beginning the bike had good pick up and speed...i gently rolled onto the throttle as to not overload the pack.

two WOT circles around the block and the pack was noticeably sagging...badly! lol I didnt look at the speedo during this run.

brought the bike in and measure voltage with wheel in the air. 49.9v stopped and about 1v drop while spinning up, this was obviously a much lower voltage drop then when accelerating. took the bike out again and measure top speed with the "depleted" pack....38km/h.

so....do the laptop batteries work? yes! even a test 72cell unbalanced, randonmly charged (battery voltages ranged from 4.10v up to 4.24v) pack got me to a pretty good speed. range sucked but then again, the planned pack will have around 3 times the capacity of this test pack and i'm sure voltage drop wont be that much of an issue...

untill i receive my mean well charger and balancing lead, this project is on hold.

i dissasembled the packs after and measured individual cell pair voltage...one pack had nice 4.17 across, most packs have average 4.13 with a few cells below and above that. one pack had 4.08 average with 4.04 being the lowest voltage. that cell pair is gonna get yanked out and replaced.

 

[DrkAngel]

Tips:

Same capacity cells - highly recommended
20ah minimum - 30ah recommended

Especially with a smallish pack - partial throttle & pedal assisting, getting, up-to-speed, will greatly improve range!
Full throttle from dead stop, produces a lot of wasteful-damaging heat and, comparatively little, useful acceleration.

 

[Red_Liner740]

^^ Agreee. This was only a "test" pack

i got antsy and wanted to see what this thing will do with the 6 packs that i had assembled.

there are another 300 or so more cells that are charged up and holding voltage waiting for me to sort them.

 

[DrkAngel]

^^ Agreee. This was only a "test" pack

i got antsy and wanted to see what this thing will do with the 6 packs that i had assembled.

there are another 300 or so more cells that are charged up and holding voltage waiting for me to sort them.

If you are getting the iMax B6 balance charger, be aware that various reports, find full 5amp charging to be "iffy". Recommend 2-3amp charging initially. Personally, my B8, blew a Mosfet at 5amps, 12v input - 29.4v output. Mosfet replaced, will test with higher input voltage, lower output voltage etc. Will post results.

Also, stay tuned for test "trial" of the Tenergy non-balance charger. After initial balance, the Tenergy has been maintaining an equalized voltage , between banks of cells, on multiple, many year old, recycled, Lipo & Li-ion packs! Equalized to within 1/100th of a volt, to the median 4.18v!

Tests will include:
multiple cycle variance;
test with 1 bank, partially discharged
test with 1 bank, higher charged

Hoping to determine if the charger helps to maintain an equalized voltage or, if equalization will deteriorate with continued cycling.

At worst, it appears that the charger, (without BMS/PCB/PCM), does a fairly good job, over many cycles, and that a "balancing" charge might be recommended, only, occasionally?

 

[neptronix]

At worst, it appears that the charger, (without BMS/PCB/PCM), does a fairly good job, over many cycles, and that a "balancing" charge might be recommended, only, occasionally?

Any charger will do a fairly good job of keeping cells in balance that aren't falling out of balance themselves.
There is nothing magic about it. I've gone 33 cycles and counting with my iCharger in non-balanced mode and a pack of lipo that was balanced late last year. Variance at top of the charge is consistently less than 0.01v.

3 cycles with my meanwell and the cells are not showing variation still.

Anyway, it is normal to be able to run for a long time without balancing. It's just that a BMS gives you a layer of security against overcharge or overdischarge, and also allows you to use more of the battery pack by stopping charge or discharge at exactly the point where the cells are full.

This is another reason why i am a fan of 90-95% DOD. I leave a little voltage at the top and bottom so that i can run without balancing my batteries for longer. I then have very good protection against eventually overcharging my cells.

As for the IMax b6/b8.. they seem to have generally have bad factory calibration. Running them at lower amps provides better balance according to a few posts i've read.