Battery selection criticism please

[wesnewell]

I've got 12 4s packs and I charge them all at the same time, the same as I would if I had 8 6s packs.

[999zip999]

Still Lipo is a hard for the work place battery if you have to bring inside to charge. If a big enough pack is less worry as not the need to charge in the office ect.

[dogman]

Yes, I left my ping V1 battery plugged into the bike the day I rode home with a 102 f fever when I got the west nile virus last summer. Two weeks later I found it all puffed and resting at 1v. The bms should have cut off the battery at 36v though, so it was a fail. The lvc in the controller should have helped, but the 3w the controller draws on standby must have been enough to take it from 28v to 1v. It was parked pretty close to fully discharged too, so 72 wh per day was enough to do the trick, with just a 100wh left in the pack.

By cycle 700, it had gotten to where it would get very unbalanced every discharge, and had lost some capacity. Not 20% lost, but more like 10%.

The point is, just because a single cell of lifepo4 can do 2000 cycles in a lab under controlled enviroment does not mean your 48 cells bouncing around on the bike in the hot and the cold, getting bulk charged then balanced, AND the bms are going to last 2000 cycles. We've seen plenty of bms or cell failures by cycle 500 or sooner.

So while one chemistry or another may have a longer cycle life, it does not garantee that all of your cells will do that. That's even more true the way some kits are marketed. That is 2c batteries matched with motors and controllers that will draw 2c. I never tire of saying, " don't buy that 10 ah battery for a 20 amp controller".

RE charging at work. For many people, charging RC lipo at work would be just dangerous enough to not do it. But if you have a secure place to charge outside, that could be different. Personally, I would NOT charge lipo on my desk at work. One puffed cell venting toxic gas in the office could get ya fired. I charge my lifepo4 at work, but that is outside.

[deVries]

equally treated, never drained 100%, charged correctly ( slightly lower than 4.20v ) at reasonable C rates ( half the claimed specs on HK ) .... lipo has been holding up as long as any other lithium packs i've used ( and i've used them nearly all )

What is your experience with A123 batteries? Battery volts/ah? Service date/cycles?

Have you tracked your LiPo with some record keeping? Service life date, total cycles, and what do you charge your lipo to & discharge to? Metered by volts or amps used on rides? What is the maximum you will discharge to if needed, or is that something you avoid except for some "emergency" that almost never happens if ever???

Thanks.

[Ypedal]

http://ypedal.com/Lipo/Lipo.htm

HK turnigy lipo started early 2010 for me, my main test rig is the Norc Chaos on 100v 5ah with a 55 amp controller. That pack was used for 2 years, bulk charged with meanwell supplies to 100.0v ( giving a range of 4.13 to 4.18v per cell across 24 cells ) .. occasionally ballanced charged with an Icharger 3010B but over 2 years of this i've discovered that the icharger ballance cycle was not needed as the cells always return to their voltages pre-ballance almost right away, but it served a learning purpose.

if you have healthy cells in your pack, a BMS and ballancing is not required..

Discharges going to work and back = 9.6km = +/- 3ah average per cycle ( from 5ah cells at 10C peak, 2C +constant from 20C packs )

work 5 days a week *( and a few cycles per day on the weekends ) , 2 years, from april to dec = 500+ cycles over 2 years and the packs are still working, i have to perform a capacity test and report back but i have 1 cell that limits the others on the most + side of the pack. always that same cell that dies first.. not sure why.

I installed 4 fresh packs on the nocro this year for commuting as the 2010 cells are showing their age but still work fine and are used for secondary packs on my other bikes ( the BMX, rang extender for longer trips in a backack, etc etc etc.. )

All my bikes have Cycle Analysts, that is how i keep track of voltage, ah, etc. on the bikes, i also use CA's on my chargers to keep track of charge profiles and behavior. (no BMS on any of my packs )

my PSI cells ( 10ah Lifepo4 cylindrical cells ) have been in service since early 2009, not that many cycles on these, they have been used on the chopper, on the BMX in a backpack, various projects of the years , accidentally drained to 0v and revived, more than once, and still work...

A123 i have not used very much, only a few 26650 cell packs here and there, but no data to report on those..

i present my projects page with LOTS of data to read thru for anyone interested in knowing details of all this.... blogged as i go.

Then i add 10,000 posts here on ES, reading and writing daily other's findings and results, and imo... start with quality cells, do a preliminary QC check and make sure you dont have runts in the pack, manually monitor them carefully all the time, any lithium chemistry will work excellent for you.

Avoid, ebay, lowest priced cells, packs spot welded crappily, bad chargers, BMS's ... i hate BMS's... they have caused me more cell failures than they have saved packs.. arg..3

This pack is still in use :
http://ypedal.com/EBK/ebk.htm

been abused, lent to customers *( heavy usage from one guy for 6 months ) cold tested, heat tested, dropped, and still keeps on ticking.. i have to get it back for a capacity test from the local customer who is currently using it.

---

All that being said, you can kill a pack with a single day of bad usage, if you try hard enough.. be it lifepo4, limn, lico, rc lipo, nimh, nicad, or lead acid... no matter.. severely overcharge it, drain it flat with a hard over-discharge, and there you go .. 2000 cycle claims worth nothing if you ruin a pack by being a jerk.... like tools... use as intended..

edit " fixed typo's..

[pff7]

"All that being said, you can kill a pack with a single day of bad usage, if you try hard enough.. be it lifepo4, limn, lico, rc lipo, nimh, nicad, or lead acid... no matter.. severely overcharge it, drain it flat with a hard over-discharge, and there you go .. 2000 cycle claims worth nothing if you ruin a pack by being a jerk.... like tools... use as intended..

nicely said Ypedal !

[aixelsyd]

Parachuting and Lipo are things you realy need to right the first time, and every time. .

As a skydiver I second that notion

[GMUseless]

do a preliminary QC check and make sure you dont have runts in the pack, manually monitor them carefully all the time, any lithium chemistry will work excellent for you.

There it is. Thanks Ypdeal. Turnigy should print that on every pack and pay you a royalty.

DIY QC...because you are about to use RC grade cells (i.e. toys) in an EV application.

I treat them like pets. They need attention. I check on them every few days. Any packs sitting idle gets a cell-log plugged in at least once a weak. I look for leakers, laggers, puffers, ghosts or MIA's. I keep a log, and labels right on the packs of which cells to watch for suspicious behavior.

And upon receiving any pack...I cycle it at least 5 times. I watch how it balances. I measure capacity. I let it sit a few days at 90% to watch for self dishcarge. I fully expect to not be able to use 10-15% of everything I get from Hobby King.

Then, I sleep good at night. And charge at work, on my desk. (But in nomex bags, and I do have a door leading outside close by...and two five gallon buckets half full of sand each in the closet.)

[dave02150]

Hello and sorry for the long-delayed response

Thank you, everyone, for your thoughts and suggestions.

Some of the advice I have taken to heart ie. I have purchased regular instead of hardshell batteries. (I'm all excited! They arrived today!)

Some things I guess there can be no definitive answer on - it's a matter of opinion and personal experience.

I have purchased 4 x Turnigy 5Ah 6s 20C packs - 2 in series (44V, 5Ah) for recreational rides, or 2 x 2 for the trip to work and back. I'm not comfortable with the idea of charging at work (yet)(maybe never)(we'll see...)

I have purchased 2 chargers - an iCharger 106B (from EP Buddy; not here yet) and a HobbyKing eco six balance charger. I have purchased 2 low voltage alarms.

The HobbyKing stuff was all ordered on July 25 and it arrived today August 7. It appears to have come from China via EMS Speedpost. I was able to track it online as far as "Released by Air Destination" on 1 August. No city name was mentioned, but it took a week to get from there to here. Packing was very good, there appears to be no damage.

Total cost so far: $281 + $98 = $379 (US)

binlagin: I am sorry to hear of your long wait; I was worried that mine may have been as long. Luckily, only 2 weeks. I am also in the Ottawa area (Chelsea, QC) - it's 18 kms to my cubicle downtown. I don't recall specifically choosing US Warehouse or International when I made my order, but it appears to have come from China and arrived here in under 2 weeks. If you ordered from HobbyKing, do they have online tracking for US Warehouse orders?

I have been doing more reading and I have lots of work ahead - I am going to be conditioning the batteries to improve lifespan and to get used to the charging / discharging processes.

Thanks again, we'll be seeing you on the road! More likely, I'll be back here asking more noob questions.
dave02150

[Jason27]

I use lipo as a backup for short distances. I just have to be very careful when charging them.