Zippy Flightmax / Turnigy lipo testing

[kmp647]

I dont post too much here as i mostly fly large RC electric airplanes and that takes up much of my time

I have put together a 150cc dirtbike conversion using a mars 0708 motor and kelly 72401 controller

being an RC nut I chose to use my old lipo packs connected up in series and paralel to make a 14s 4p 58.5v pack

the cells are mixed from 4000ma to 4500ma mostly in 6s or 4s packs. I have charged them individually with my hyperion 6S10I Chargers(bank charging)

I also charge using a thundersky 6a 58.5v charger from elite , charging the whole pack together.

my pack is about 16ah or so and provides about an hour of squirting around the yard.

I have no amp restrictions on my controller and I guess i may be pulling 220 to 300 amps at times on a hard launch.

I have the motor setup with the drive sprocket on the right hand side of the bike driving a scondary reduction shaft (5/8)

Originally I had 40p chain on the reduction with a 12t motor/ 28t shaft, the other end is a 14t sprocket and chain that goes to the stck rear 46t sprocket, I have now switched th secondat reduction to belt drive using an 18t motor pully and a 40t driven pully on the shaft, givine about a 7 to 1 overall ratio

anyways I think the zippy and turnigy lipos are a great deal and very usable if you are careful
I will try to post some pics, right now the file sizes are to large


Kevin

[methods]

Thanks for sharing.
We are interested to see this setup.

Get the files below 500K.
If you want them to fit on the screen (i.e. not look like a link) I think 800 wide will fit, possibly a little more.

I usually just lock the aspect ratio, set the width to 800, then lower quality to 70% (or whatever gets me a few hundred KB)

-methods

[mwkeefer]

Hello All,

I have received 10 x 3S 11.1v 5AH Turnigy Lipo packs.
1 of 10 3S packs was DOA but repaired (I think, still have to test on bike)
Bottom Line: Extreme Power, No Heat, Great Price, Very Light - Awesome Packs, Tested, Measured and Confirmed, Very Low Internal Resistance !!!

I have never had a lipo fire but please take proper precautions and don't be a jacka$$, mounting your lipos under your crotch in the A frame without some form of NON flamable battery box with some form of pressure cap that faces either forward or is at the far forward position and vents right and left of head stem or at a minimum a blast shield.

My batt box (blast box) is made of 5mil alum panels, welded together which has right and left forward vents (hopefully wont melt or warp head stem if it ever blows a lipo) and will protect my crotch, legs, passenger (my son behind me) from flames, exhaust venting from a lipo puff or fire. Designed so that if there is any real force the directional thrust of the explosion / fire will cause the ebike to slow it's forward momentum.

I went the further step of rigging a very quick, one handed disconnect which will jetison the entire battery box.

This might be over engineered but I have seen the you tube videos of lipo fires / explosions and the added weight of the alum box is minor and should channel any burn out away from me and my son. The critical point is my son!

Once I finish the battery box (painted titanium to match the bike) and my pre-controller I will post all relevant details needed to diy the blast box (can't think of another name), the pre-controller and any other niceities I come up with in my experiments.

Current eBike is:
36" front hub kit from Jason @ http://www.e-bikekit.com of which I am using the included Infineon 9FET controller mounted to the bottom side of a front handlebar bag and the hub (I had to slightly taper the 10mm keyway in the axleshaft to fit in the dropouts properly of my Judy TT and now my Tora RockShox).
Inital power source: 36s3P nimh for 50.4v @ 9900mah charged (from Jason @ http://www.mtobattery.com, fantastic battery shop... found him dealing with Segway battery failure due to moisture, he laser cnc's the cases open this guy is battery elite)

In all fairness I should add that I have modified the controllers software using ParameterDesigner (and a USB->Serial TTL inteface from sparkfun that I had laying around from some previous project). My mods were to the LVC, Current Limit=38.5A, Phase Current Limit=75A, S2 Speed=110% and a few other tweaks (do a quick search on google or here at ES for "infineon controller Parameter Designer").

The results are spectacular (once my front wheel stops smoking - well spinning) TOP SPEED=38 MPH, AVG=32, Range on 5AH 12S (4x3S 5AH Turnigy Packs) approx. 6 MILES / 9.656064 KPH @ nearly WOT and NO pedaling (not even to help start). This was a brute range test at max power and let me say that my test course is not for the faint of heart, 1.2 mi of 50/50 flats and 10% grades, dh 30% grade, 3.1mi gradual 10%, 1.5mi with a nice .5mi 24% grade uphill and then a patch similar to the first 1.2mi with 50/50 flats and 10% grades.
With LVC set for 3.2v per cell or 38.4 (actually set lower but with 4v of slack, see the ParameterDesigner info) and according to my eLogger v3 the pack provided 5302mah (over rating even with such a safe cutout margin), peak current of 38.5 (dead on) and ear to ear ev grin accelleration, max watts was approx 1954 WATTS - lol, motor never got warm, esc was but batteries stayed about 2 deg. C over ambient temp under my approx 8C max continuous load.

I should also add that I charged and balanced these 3S packs 2-3 times before this test using iCharger 1010B+ and monitoring / logging all charging data for the packs using LogView. Charged they were all within .01mv of each other (in each 3S pack and paralleled into 12S) and stayed this way through 1C discharge testing.

Only issues with the Turnigy's was 1 of 10 came in at 0 V but a quick check on ES and in the HK comments for the packs and I tore the wrapping off the bad 3S pack and sure enough the solder joints had broken (weren't great to begin with) Since I had no aluminum rosin or solder I just used my trusty and overpowered RS gun to remeld the existing solder joint while applying pressure to the disconnected tab using a probe from and old VM (I do this alot).
Though I haven't discharged this repaired? pack on the bike yet, I have run it through 5 full charges at 1C (first charge I did at 1/5 C and dischage at 7A and pack seems fine. I will test on bike in a day or two and post any observations or issues with the pack keeping it ourside my battery box in a seperate lipo bag while testing for safety, and no I don't test with my son... I use 38lbs of SLAs and a 5gal gas can filled with water in the child seat to simulate my son and his shifting weight while testing)

If anyone would like the logs from the eLogger or the charge / discharge cycles on the packs from logview, drop me a msg and I will provide them.

Sorry for the long post but I did the full gamet of testing on these packs and thought I should share as much detail as possible.

Thanks to everyone for all their help, contributions and problem solving that got me interested in an eBike as an alternative to my i2 Segway (3 years and still going).

- Mike

[methods]

I am having the same results.
Of the (8) 5000mah 6S packs I bought 7 of them are still within 30mV after many rides and no balancing.
One pack, the one that came in with one cell 100mV low, is still off
I now suspect that they just forgot to balance that pack before shipping it out.

I am not going to balance these packs for another couple of months.

I charge till the first cell hits HVC and I discharge (hypothetically) until the first cell hits LVC
(in actuality I have not yet ran the pack down past 80%)

-methods

[mwkeefer]

methods,

Did you charge/balance/discharge the 1 pack that came in with the 100mv low cell before using it in your application?

If not, that is your culprit... unlike many battery chemistries, lipo doesn't seem to have a bleed off effect (unless they are damaged) to help self balance. That would (probably has) caused your already imbalanced pack to get quite a bit farther from balance with each charge / discharge (depending upon load).

You have the right idea of cutting charge when best cell reaches 4.20/4.21 and using an LVC based upon the lowest cell drop but... if you have balance taps (you do) then just charge that out of balance pack with a decent 3s charger (I wouldn't charge at greater than 1/2C) / balancer.

Though 100mv doesn't seem too bad, I would wager that after each cycle you will see between 5-10mv difference (your good cells seem to suggest that) every 10 cycles or so but with the 100mv low condition you could be loosing a good deal of your capacity.

I'm not an EE and I could be wrong but from everything I have tested and all I have read that would be the case.

Have you thought of using one of the various BMS balancer circuits available here on ES to keep your packs in top shape and to last for as long as possible? That would work perfectly will a standard charger only (could even use SLA CC/CV tweaked for correct voltage).
-Mike

[methods]

Thanks for the tips - but not to worry - I am the Lipo master

I think I own 50Lbs of Lipo - though luke probably owns 100lbs

I have 24S balancers, 12S balancers, a box full of 6S balancers, balancing chargers, non-balancing chargers, home made chargers...
I charge my packs at 24S 100.8V 13A with power supplies.
2 of my chargers draw so much current that I have to plug them into special 2 gang outlets at my house that I wired for 20A + 20A

I probably have 100' of collective JST-XH 6S balance tap pigtails that I have built into every sort of balancing harness you can think of.

I am purposely not balancing the packs to see how far off they get.
Wont hurt anything since I do cell level battery management.

-methods

[liveforphysics]

I made a super fancy continous balancing setup for my lipo packs. Kept every cell +- .02v of each other. Turns out, that was totally un-needed. I charge at 84v and 32amps (requires 2 seperately breakered power outlets). The cells never get out of balamce, and I kinda feel like I made my balancing setup for no reason. I think the reason is i run one pack at 40Ah (8x5Ah cells in P), and the other at 20Ah, and the cells never really feel any stress. I can cruise along at 55mph going up hill pulling 250amps continous, and the packs don't even get warm, and the voltage stays rock solid. Same with when I charge at 32amps, the cells never feel any stress or heat, and I think that helps them stay in perfect balance so well. I also rarely even discharge below 50%.

[spike]

I haven't used RC Lipos before and would appreciate some recommendations for a 60+V 10Ah setup from Hobbycity. Choosing the packs seems to be much easier than choosing the balancing charger, connectors and discharge monitor. Can anyone give a recommendation for a full setup with links to HC? I know the dangers, just want to get started with the high C packs. TIA.

[mwkeefer]

methods -

my bad : ) I knew you were heavy into (pun intended) lipo and should have realized you were testing max oob (out of balance) when doing std charges with std charger. Just thought I'd mention the balancers either way for potential newbies.

I am certain you, liveforphysics and I (plus most others "really" into ev or RC) have adequate testing equipment to monitor these packs (yep, you have me out packed by prob 100s of cells) and I have a fair idea of what I am doing but you obviously KNOW what you are doing. My concerns only fall with people who are newer to the chemistry as I was a few months ago = )

Though as liveforphysics and you both indicate the packs don't get too far oob (even with the loads liveforphysics) uses, I just wouldn't want someone to skip at a minimum a 6s analyzer, charger, discharger, logger because otherwise they could have issues. Personally I believe that with this chemistry doing a full checkup every 10 or so cycles is required (Identify weak cells, possible damanged cells, etc) which I do using my pair of iCharger 1010B+ chargers. I have seen some fairly out of wack cells quickly this way and eliminated them from the pack to prevent damages.

I'm just placed my third lipo order (split into 3) for 5x6S packs + a small ton of the 4mm bullet gold connectors and some other odds and ends. I placed as 3 orders and did the EMS shipping to the USA (methods - I did read your slow boat post) so I should have them shortly (saturday / monday).

spike - hey man, that's my real world nick = ) If you could be a bit more specific about your needs I am sure that myself and the other (more elite) lipo people would be glad to assist. Based just upon what you have put in the post and assuming you mean nominal pack v as opposed to off charger v: To get 10AH you will need to double the packs from HobbyCity (5AH ea) and for the voltage at nominal just use (3.7 / 60 = 16.21 lipo cells). I think you would be ok just using a 2P16S configuration which (and I am looking to methods or liveforphysics now to confirm) would best be fit ordering 4 6S packs and 4 2S packs from hobby king.
That will give you a nominal voltage of 59.2v but off the charger you would see 67.2 which should work fine.
If this is not what you are looking for in nominal V let me know.

In regards to chargers I will let methods or another chime in as I use 2x fairly expensive (160+ USD) chargers/balancers and a custom charge harness currently (uses relays to switch the packs into charge mode as 2x or 4x 6S packs, once power is applied to the charge port - if failure or removal of charge power then board defaults to discharge mode (it's ugly and bulky but it works and I already have my netbook in my luggage bag with all these other items. Not sure this is a way for anyone to go, I like the idea of SLA chargers (or powersupply chargers) for in field use but... I didn't know enough at the time to trust myself with those.


- Mike

PS: methods - You have given me lipo envy!
PPS: methods - Have you ever had a lipo puff or blow while in use on bike? If so, bad lipo? Electric failure cascade, swollen packs? Did you get hurt? (just helpful safety info for me and everyone else)

[spike]

spike - hey man, that's my real world nick = ) If you could be a bit more specific about your needs I am sure that myself and the other (more elite) lipo people would be glad to assist. Based just upon what you have put in the post and assuming you mean nominal pack v as opposed to off charger v: To get 10AH you will need to double the packs from HobbyCity (5AH ea) and for the voltage at nominal just use (3.7 / 60 = 16.21 lipo cells). I think you would be ok just using a 2P16S configuration which (and I am looking to methods or liveforphysics now to confirm) would best be fit ordering 4 6S packs and 4 2S packs from hobby king.
That will give you a nominal voltage of 59.2v but off the charger you would see 67.2 which should work fine.
If this is not what you are looking for in nominal V let me know.

In regards to chargers I will let methods or another chime in as I use 2x fairly expensive (160+ USD) chargers/balancers and a custom charge harness currently (uses relays to switch the packs into charge mode as 2x or 4x 6S packs, once power is applied to the charge port - if failure or removal of charge power then board defaults to discharge mode (it's ugly and bulky but it works and I already have my netbook in my luggage bag with all these other items. Not sure this is a way for anyone to go, I like the idea of SLA chargers (or powersupply chargers) for in field use but... I didn't know enough at the time to trust myself with those.

Thanks Mike (Spike)

That is pretty much the info I'm looking for but I'm not too worried about the exact voltage. Around 60-70V fits what I would like for my next build. I'm more concerned that I'll buy the wrong packs, mismatch the chargers/monitors, and pay more than I need to get started. For example, if I bought these packs http://www.hobbycity.com/hobbycity/stor ... oduct=9176 in 2P3S it would give ~67V 10Ah nominal (top end of what I need), or these http://www.hobbycity.com/hobbycity/stor ... oduct=9177 in 2P4S it would give ~59V 10Ah nominal (it would be adequate for the motor I'll be using), in either case I wouldn't know which charger/balancer to buy for these packs or how many. I only understood half of what you said about your charger setup . I've also read that it's wise to buy a cell monitor for the packs on discharge. Any recommendations on matching products from the Lipo elite would be great! I guess a starter pack for RC newbies is what I'm asking for.

[mwkeefer]

Hello all,

Just an update on the turnigys...

3S Pack #4 just went, its reading funny on the ohmmeter for internal resistance and if i push hard on the edges where the solder tabs are within the heatshrink the readings go back to semi normal. This is for sure a broken solder joint that was fine prior to use. While these are still high quality and the best value in cells I have found, I plan to open them all now and resolder the tabs properly. I have to do this anyway to a few packs to make a 10S3P configuration so it's not a big deal but... as of now, I would suggest removing the shrink and pulling the silicone pad over the PCB and ensuring good electrical and mechanical connections exist fixing where need be.

Even with this, I would still recommend these batteries and I will post an update when I determine the total number of bad joints in my 10 packs. Guess I do need aluminum flux and solder.

spike,

If you would be so kind as to post your current setup: motor type, drive type, speed controller type, desired top speed, average crusing speed, manor in which you intend to use (power only, throttle only or hybrid) and finally the range you would like to acheive.

Be as specific as possible about your motor and ESC, if you have ratings such as kV (RPM of motor per 1V input) that would be helpful. What model / type of ESC are you using or if your not sure, where did it come from.

You seem to have the right idea with the packs but to give you my best advice I (we) would need a bit more information.

If you can post these details, I will calculate a best case / worst case scenario (usign your use patterns as starting point) and then the real guru / elite on here can correct me if / where I go wrong.

Another item is budget, what are you planning to spend for the batts, chargers and power supplies.

And yes cell level discharge LVC (low voltage cutout) is important because if you develop a bad lipo cell it will prevent over discharging a single cell thereby causing potential damage. That would save your pack (if you have the LVC wired to a power cutout - ebrake connector or such).

Post what details of your intended setup you can and I will work out recommendations tonight.

-Mike

[methods]

PPS: methods - Have you ever had a lipo puff or blow while in use on bike? If so, bad lipo? Electric failure cascade, swollen packs? Did you get hurt?

Never. On a regular basis I am running my 24S2P pack and my 12S4P packs. I have shorted both of them many times at a cell level and at a pack level. There are at lest 10 pictures around here of what I call "Kentucky Fried Finger" and never a problem with the cells.

Btw: My new charging setup does cell level balancing for 12S and 24S via a GoodRum Fechter type shunt balancer. It is not finished yet though so I just charge at a pack with BM6's attached. They will start beeping at 4.25V - which - after the charging current is removed settle down to under 4.20V / pack.

I am using the power supplies below for charging. Each is good for about 1.5KW

---------------> Charger hacks



-methods

[mwkeefer]

methods -

First, thanks for confirming what I thought... most people will not have problems with lipos even with "mild" abuse, ie: KFF (Ive just begun getting my color back after connecting a final 4mm male -> female and shorting a 24AH48V SLA supply @ full charge - I really thought my finger was gonna fall off and I was just in shock).

Second, amazing setup... I recognize the powersupplies, I found them recently while searching for another commercial contract project (need more like 110-220vac -> 100v dc @ 6A, very not cheap!).

I am still working on incorporating a modular BMS (over voltage protection, undervoltage warning then shutdown trigger, etc) which will handle up to 3S @ a time but using individual 4.22V max @ 1C (5A) chargers controlled via a common arduino mini 20mhz dev board (you should see the size of this part, I couldn't hardly find it when it arrived in a box). The idea is handle the charging of the cells individually via the balance taps (5A might be too much, not sure yet) so that I don't need to buck up the voltage to match a particular series count of cells. By incorporating a warning indicator (line drawn high +5v) a simple loom (or flat Cat5 cables, IDE cables, etc) cab be used to run signal wiring to an LED display or, in my particular case ... the arduino is already driving a very nice color LCD screen (cell phone type) which means I can use commonly available open source libs to generate the needed graphics to represent the physical connected pack and which cell has a warning. Now I only need to send back a device id (to assign to each cell in pack) and a reading over a serial bus (2 wire), if I go 3 wire I could then address the device and tell it to cutout or reduce current, etc. At which point the controller will automatically reconfigure for instance if your running 12S and the controller is notified of a failed cell it will essentially remove the cell from the pack and change the pack cutout voltage accordingly.

Too much info about a totally un-related issue. I haven't pulled the pack apart yet, I am busy with my other pack charging and balancing while logging (this is cycle 9 for this pack) and I want to have this data (internal resistance, charge capacity, discharge capacity, temperature chages, discharge temperatures) all at a cell level for cycle 10 which will be the basis for my "official" and technical review of the packs.

Then I am going to dissassemble the packs and reconfigure into 4 x 1P5S @ 5AH packs which will be connected for discharge in 2P10S @ 10AH. The other packs I am planning will be 4x 1P2S which will be wired into 2P2S configuration for discharge then run in Series with the main 10AH 10S pack.

I have already begun designing a solid state switching system( I guess it would qualify as a Solid State Relay array) to handle switching the packs into charge mode and disconnecting the packs from each other when not in use.

This makes my charger design much simpler as I can simply daisy chain these boards together on a serial bus and provide individual LVC/HVC/LVC Warning for such a large pack at the individual cell level.

Just so you know, my Maximum current draw (at 10S) would be 87A but I don't expect to go that high, more like 70-75 which is perfect for cheap FETS without even paralleling = )

-Mike

[spike]

spike,

If you would be so kind as to post your current setup: motor type, drive type, speed controller type, desired top speed, average crusing speed, manor in which you intend to use (power only, throttle only or hybrid) and finally the range you would like to acheive. Be as specific as possible about your motor and ESC, if you have ratings such as kV (RPM of motor per 1V input) that would be helpful. What model / type of ESC are you using or if your not sure, where did it come from. Another item is budget, what are you planning to spend for the batts, chargers and power supplies. And yes cell level discharge LVC (low voltage cutout) is important because if you develop a bad lipo cell it will prevent over discharging a single cell thereby causing potential damage. That would save your pack (if you have the LVC wired to a power cutout - ebrake connector or such). Post what details of your intended setup you can and I will work out recommendations tonight. -Mike

Hi Mike. Many thanks for the help.

I'm holding off using the RC motors/ESCs for ebike builds until I see what develops. That will probably be the next step. The lipo packs will start on a Hi-Koll/USPD setup on a 27" touring bike. The controller is a Crystalyte 36/72V 45/A controller (analogue not digital). According to EVDeals the Koll motor runs at 3730RPM at 48V/883Watts, but that gets geared down to a wheel speed of ~45Km/hr. I think 72V would be too much for the Koll motor which is why my target is between 60-70V. The bike will be used for commuting a 20Km round trip in busy traffic. I want to keep it light with good torque and acceleration from the lights. Keeping up with the traffic would be useful. The limit is 60Km/hr in built up areas. I can charge the batteries at work if necessary so high Ah won't be necessary. I can just peddle harder if the batts drain down. I had figured on spending around $600 to get started with packs/chargers/monitors, but could spend a bit more if that's unrealistic. Cheers!

[liveforphysics]

If you are going to make your own charging/balance setup, don't set it for 4.2v. Set it for 4.125v peak. Yes, you sacrifice 10% of the potential to store energy. However, your number of life cycles extends by about 10x (yes, 10 times the cycles) according to most manufactures cell life graphs.

Charging from a switching power supply works fantastic. They do the perfect CC/CV curve ideal for charging LiPo.

LiPos are really not a hazard when shorted. A proper LiPo battery is designed to harmlessly vaporize it's cell tab in the event of a serious short, and it vaporizes that tab well before the cell even gets warm. The packs are designed like this so it's as if each cell has its own fuse protection built into the pack design.

I run a 20s, and I made the packs in 20Ah 10s cell groups. I run these cell groups 2s 2p if I want a 74v 40Ah pack, or 2s1p if I want a lighter weight 74v20Ah pack. When I charge, I split the pack into 10s sections if I'm going to balance, or I leave it 20s if I'm not going to balance. My cells never go out of balance, so I generally just charge as a 20s pack.

I set the charger for 82.5v. This brings each cell to ~4.125v.

There are a couple things to be careful about with LiPo. If you over discharge a cell, it's damaged. It will have higher Ri, and it's a hazard to have in your pack the next time you charge. You are not in any danger as you are over discharging, it's when you go to recharge again that you are taking the risk of fire. The second is to not let cells go over 4.3v. Yes, you can generally raise a cell to 4.5v-4.8v before it starts to vent, but exceeding 4.3 is when you begin to damage the cell, and you are risking a venting event.

I think a potentially slick and simple and reliable way to deal with LiPo would be 5w 4.2v zener diodes with a 0.1ohm resistor in series across each cell. Then set your power supply to only charge to 4.125v/cell average, and if a cell were to get out of balance for some reason, the zener would clamp it at 4.2v during charging. You could very easily build this tiny cell level over-charge protection right into the pack.

I just did a quicky search on digikey, and found some 5w 4.3v zeners for $0.14/diode. They have an excellent temp/v change curve of about -0.4mV/degC. So, even if your pack got 40defC above room temp during charging, it would LOWER the clamping voltage by ~16mV, which would actually just make things slightly more safe I supose. lol. 10uA leakage current at 1v, does not list a spec for 4.1v leakage current. I would take a wild guess it might be around 100-2,000uA at 4.1v. That would mean it would be safe to stay on a 5Ah cell for months (maybe years) with out leakage current being a danger to draining the cell. It would be a good idea to disconnect it if you were going to store your pack for months, but that's not much of a hassle or concern for most folks.

Unless there is some critical flaw that I've missed seeing, it seems like you could setup indivual cell level over-charge protection for a pack for about $5 in parts.

Does someone see a flaw in my logic here? Any critical flaw that makes it a poor choice to use a simple zener clamp for cell protection? If the 2Ohm impedence seems too high, or 5w limit too low, it would be easy enough to connect 4 or 8 in P, and get that down to 0.5Ohm-0.25Ohms with a 20-40w limit. They are only $0.14 each from rip-off-key, so I'm sure I could do a 1,000 quanity buy on them for like $0.05 each from a real parts supplier.

[ZapPat]

Luke - This is from the diode's datasheet. To me, it looks like the current will be too high even before even hitting 4V. Too bad, as a zener with a very steep curve would have been a nice simple fault protection.

Zener I vs V.jpg

Zener I vs V - The 4.3V one is the fourth curve from the left.

(99.08 KiB) Downloaded 895 times

The chargery BM6's that Methods uses are great little gadgets, and pretty cheap at 13$ per 6 cells. You just have to be in earshot to disconnect the bulk charger if something weird happens. They also have a programmable LVC, so can also be used for discharge protection.

Another great thing about the BM6 vs other RC multi-cell monitors is that it doesn't seem to draw it's power from only the first two cells. This is important if you leave them on the battery for long periods, since the BM6 will not bring your cells into a more and more unbalanced state with use. All the others I've seen will drain maybe ~6mA or so from the two first cells - not much, but a pain nonetheless since it will end up being the biggest cause of cell disbalance in these high-C rate LiPo packs.

Pat

[Jeremy Harris]

Just as an aside, I'm currently working on a LiPo charger, using the same sort of system that Doc came up with for charging LiFePO4 cells. I've found some switch mode DC-DC converters that have a 3.3V and 1.2V output, electrically isolated from the input. The output voltage is trimmable by +/- 10%, which will allow me to trim the series linked outputs between 4.05 and 4.95 volts. These things put out 15 amps, so are only really suitable for high charge rate LiPo cells.

If I trim them for 4.125V per cell then I think I should have a pretty robust high power charger, at a cost way under that of one of the dedicated RC Lipo chargers.

Jeremy

[liveforphysics]

That sounds great Jeremy! What input voltage do they take? Any ideas of the efficiency?

What are the physical dimensions, a rough idea of cost?

Thanks!
-Luke

[methods]

The biggest problem I see with parallel charging is that you need to get to each cell....
You cant push 15A through a JST-XH connector rated for 3A so that means you have to cut into your lipo packs and (in the case of a 24S pack) bring out 25 14awg wires.
Then you need a connector suitable for passing 15A.

Sounds like a lot of work if you have mountains of Lipos.

My vote is for charging off of a regular old power supply and using a shunt type balance like the GGoodrum / Fechter board.
I have my issues with that board but I like it in principle because you can mix and match very easy.

I use power supplies that have "modules" so I can match them up in parallel and run 15A or 20A or I can even pair up supplies and run 40A.
Hypothetically limitless.

How small are those 15A supplies you are using?
Could I put 24 of them on the bike? If I could - that would be a big advantage over my 1/2 shoebox size supplies.

-methods

[Jeremy Harris]

The modules are Power One, 1/4 brick ones, so are quite small, see eBay 160350956570 or the Power One data sheet attached. They run from a 36V input, which happens to be fine for me because I have a big 36V switched mode supply I can use to power them.

I agree, the cells may need to have the balance wires beefed up for 15 amps per cell, but if I have quite a few cells paralleled up via the balance connectors I'm hoping that things should even out, allowing the standard wires to be used.

Jeremy

[methods]

but if I have quite a few cells paralleled up via the balance connectors I'm hoping that things should even out, allowing the standard wires to be used.

Jeremy

ahhhh.... I did not think of this.
Good point.

-methods

[mikehains]

A very informative, excellent thread. Hopefully the right one for me to make my first post.

The good news - based on my lurking research here, my 9 x 5000maH 5S Turnigy packs turned up yesterday from Hobby City. 8 of them perfectly balanced. One not so good, with one cell around 100mV low. That has since been ironed out by the 1010B+ charger (also purchased after carefully reading these forums).

I am going to run them 10S4P for a nominal 36v system, and charge them 10S4P with the 1010B+ charger ... balance leads in parallel.

Here's my big question: Can the balance leads stay in parallel when they are in use on the Kart ?

I have 2 x Chargery BM6 (after reading posts from Methods) which are excellent. Given that the pack is 4P, these devices will be enough if the balance leads stay in parallel while the pack is in use.


Thanks in advance,
Mike

[mwkeefer]

Mike,

If I understood correctly you are running 10S but have 4 of them for 4P10S. Currently charging all 4 packs of 10s on the 1010B+ with the balancers in parallel same as discharge of each 10S pack.

If that is correct then yes you can leave (and should) that configuration while discharging also.

If you wired your packs the correct way from scratch (assuming 4P10S not 10S4P there is a difference) then you would first parallel each 4 individual cells (totalling 40 cells) then connect them all in series. In this instance you would add a balance tap at +, - and on each cell inbetween. Basically you would still have 10 taps and they would be wired in at the paralleled cell level.

Your setup is perfect for the balance charging taps and good enough for the discharge side too. The proper way would have been to do 4 cells in parallel, make 10 packs like that @ 3.7 nom ea 20AH then connect 10 of them in series for 12S 20AH. That type of build would be referred to as 4P20S.

Your pack is correctly configured to charge as a 4P20S since they will both tap the same place, I would stick with no more than 1C charge rate to keep the life of your packs (cycles) higher.

It would be better for a discharge perspective if the output termination was based on these 4cell parallel segments but unless you going to move past the rated value (4x20C=80C*5 = 400 Amps Nominal (4P) and max would be 4 x 30C = 120C * 5 = 600 Amps for 15 Seconds.

You have a very nice pack there, now if you have a sufficient power supply that can push over 16.5v and 30-40A continuous... you have a perfect charging system with your 1010B+ (check the post about the power supply onsale for 17.00 at microcenter, quality dual fan unit. Fits nice with charger in trunk on rear rack for my bike.

If your not sure about the top end speed of 10S, you could always make a similar pack of 2S4P and wire in series to make a 12S supply (or 3S, 4S). For testing... use a single 10S 5AH pack and series with single 5AH 2S, 3S, etc. No they wont go more than a few miles (10 or so) at a nominal draw of 30A peaks of 40 but that is fine for an evaluation run.)


Hope it helps!

-Mike

[mwkeefer]

Mike,

Don't know why I didn't think this sooner but the 1010B+ is max charge rate of 10A which I think drops to 7A for 10S, the limit is the voltage buck up and the components themselves and it is right around 300 watts so.

10S Max V required for Charge: 42.4v DC
300 Watts Potential / 42.4v = 7.07 A

lets be nice and assume 100% efficiency and ample DC power to operate the conversion (above 13.5v)

10S4P Capacity = 20AH

7 / 20 = 2.86 Hours or 2 hours 50 minutes (approx) to acheive full charge from empty.

Just as long as your satisfied with the 7A limit always (forget fast charge, you still can't push more than 7A when in 10S mode) this is actually a great setup.

3 Hours Charge Time is nothing compared to my 6 hour Segway charges and you have room to upgrade, modify and play if you want.

An additional item worth mentioning is that you can leave the 10S paralleled tap connected to your 1010B+ set to monitor mode to view realtime cell cluster information and log battery drain, etc using the LogView software so it really is a nice setup.

The slower charging will result in longer battery life. Also, set the lipo charge cutoff @ 4.18 as suggested earlier in the forum, this will greatly increase your packs longevity also.

The only real problem I see to using the parallel balance tap (not for your application, for mine) is that having 3 good cells and 1 dead or dying in the cluster of 4 and the 3 good ones will mask the failure cell. My intent is to monitor each individual cell (in your case that would be 40 monitor leads and analog to digital conversion. My final config will also be 10S but wired as 4P10S and tapped per cell not per cluster. Charging will be handled by dual 1010B+ chargers running off a 750 waltt modified PC power supply (portable) and charged in non balance mode without plugs most of the time but using the paralleled method to charge 2 of the 10S packs per charger (1.5 hr full charge)

This will all be replaced once my pre-controller is working with it's own charger = )

-Mike

[mwkeefer]

10S4P Lipo Nominal 37v or 3.7v per cell
Manu Spec Max Charge: 4.20v per cell or 42v
Suggested Max Charge Cutout: 41.5-41.8 - 4.18-4.15 (should extend the life of your packs)
Maximum Low voltage cutout: 30v or 3.0v per cell
Suggested Low Voltage Cutout: 31-32v or 3.1-3.2v per cell