Richard D Bahmann aka/Wrongway

My Feedback: (42)

Thanks!!

cobrajocky

everydayflyer ,

Had my first outing last weekend with the new 3S A123 VPX based pack in my FW-190 (see posting above), very disappointing. Hoping you can decipher what went wrong.

In my foam FW-190, the 3S A123 pack had noticeably less power right from the start than the 3S 1500 mAh 20C pack I've been using and in just a couple minutes in the air the battery sagged to just enough for a very quick landing. On the ground, I could hold the tail and gun the motor and watch the pack sag to nothing. Total run time (including the big sag) maybe 3 minutes total.

Specs on the power plant in the FW-190 - TowerPro 1500KV bell type brushless, rated at only 14 amps, running a 3 blade GWS slow fly prop 10x6, 20A ESC.

I charged the A123 3S at 5 amps - highest my Mystery charger with go with Li-IO or Li-Fe program settings -, at 3.6v in automatic charge (the charger detects the max level).

chadr

i am no expert like everydayflier, but have some a123 experience under my belt now. when you recharged the pack how many mah were put back in? do you have a low voltage cutoff on your rc? what were the voltage levels of each cells at the start and end of the charge cycle?

everydayflyer

A fully charged 3S LiPoly starts at 12.6 volts and under a moderate to heavy load is 10 to 11 volts.

A 3S A123 1100 starts at 10.8 volts and under similiar loads is approx. 7.5 volts. There is good reason wht SOP is to use a 4S A123 to replace a 3S LiPoly.

As mentioned A123s also require a lower LVC. Standard for them is 2 volts per cell. In contrast 3 volts per cell LVC for LiPoly and 3.2 is much better/ safer for them.

Charles

cobrajocky

everydayflyer,

I'm still very wet behind my ears on "lectric planes (old Nitro / Gas flyer), can you explain SOP (standard op proceedure?) and LVC?

"A 3S A123 1100 starts at 10.8 volts and under similiar loads is approx. 7.5 volts." Wow! I thought I was reading in various strings around here, that A123
s held up their peak charged voltage a hell of a lot better that flopping 3 volts! If this is true, and mine acted like this within seconds, A123's aren't worth it.

OK, I get use a 4S Li-ON when subbing for a Li-PO. Athough then, at the cost of A123 cells even scavenged from VPX packs, A123's aren't a cost effective alternative to Li-PO, especially as the Li-PO pack prices are falling quickly. Also then the A123 packs at a 4S to Li-PO 3S comparable ratio, are at a huge weight disadvantage. Also much bulkier.

Not sure I understand what your saying in - "As mentioned A123s also require a lower LVC. Standard for them is 2 volts per cell. In contrast 3 volts per cell LVC for LiPoly and 3.2 is much better/ safer for them."

My charger will allow for a fully manual charge (5 amps max); what would you recommend for charge parameters? Total charge time at these parameters?

everydayflyer

Correct on SOP , LVC Low Voltage Cutoff (point where ESC either stops motor or pulses it).

I have been posting CBA graphs of A123s under different loads for over two years now. Just like LiPolys it depends on discharge rate and load.

Fact is the very first post in this thread has a CBA graph showing these 1100 being discharged at 6-21 amps.

http://www.rcuniverse.com/forum/fb.asp?m=6590509

I flew LiPolys for years and then made the switch to A123s. I love the fast charges,hundereds upon hundreds of cycles life, no fear of venting with flames, etc.

Cost . To me it has always been cost per flight. I have been very careful with top of the line expensive LiPolys and gotten perhaps 200 flights before performance really started to drop. I have abused A123 and have 300 to 500 flights on packs that are still going strong.

A 5S A123 2300 which cost approx. $90 to $100 if you purchase it pre built flys my 48" WS / 3 to 4 1/2 aircraft as well as a 4S 3300-3700 LiPoly which cost $140 to $180 and once again the A123 will last 2,3 perhaps 4 times longer and can be charged much faster. '

LiPolys drop voltage on a curve during a flight so by mid flight you have less power than at the first of flight, A123s stay very close to the same power until they are empty.

LVC references of 2.0 for A123s and 3.0-3.2 for LiPoly.

LVC of 2.0 per cell for A123 will result in close to an unloaded / resting voltage of 3.2 per cell and 95% of capacity used if power system is correctly matched.

LVC of 3.2 violts per cell with LiPoly will result in open / no load voltage of approx. 3.7-3.8 volts per cell and 80 to 90% of capacity used.

Using 100% capacity of A123s does not hurt them. using more than 80% of LiPolys capacity does harm them.


Charging: I charge A123 2300 at up to 10C. I have charged the 100s at 10C but really feel that 5C is better for the 1100s as they retain heat more due to thier steel construction.

If you really want to learn about A123s then RC Groups is a much better site.

Here is my A123s links post .

http://www.rcgroups.com/forums/showp...01&postcount=2

Charles

cobrajocky

Thanks Charles,

Will check out the RC Groups link you provided.

Using the A123 2300 isn't an option for what my son and I fly, mostly light weight prop or small EDF park flyers. If we're going to use anything it would be the 1100's.

However, that being the case and if it needs to be a 4S A123 replacing 3S LiPO (or 3S A123 for 2S Li-POs on very small planes), WEIGHT is a BIG issue. Li-PO's for the same C output wins hands down. It will really limit what very light planes we can fly using very heavy A123 1100's.

For 3S and 4S A123 1100 packs, what manual charge total time should I use if the charger is set for 3.6v and 5 amps? Or should I just trust the charger to do it automatically sensing for a full charge?

everydayflyer

3.6v as a LiPoly charger which charges to 4.1 or a A123 charger which charges to 3.6?

In general foamies such as sold by Fancyfoam.com are the min. size for 1100 A123s. I use to fly these with 3Sn 1320 LiPolys but use 4S 1100 A123s now. They are aprox. 3 oz. heavierie but fly fine.

MiniUltra Stick flys great on 3S A123 2300 with Hacker A30-16M / 12X8 prop.

A123s are not for all planes or everyone. Sure are a lot lighter than Ni batteires.

Charles

cobrajocky

No, my "Mystery" branded charger (basically the same as a dozen others I've seen with LCD data displays with other brand names) allows me to choose Li-PO, Li-Fe or Li-ON and voltages correspondingly of 3.7v , 3.3 or 3.6 as a program. I've been using 3.6v (Li-ON) since it gave me the highest voltage without being in a Li-PO program.

As I reported in an earlier posting this page, using the Li-Fe "automated" charge program (3.3v), the "full" charge was only 10.52v.

Max selectable charging amperage with this charger is 5 Amps.

Thanks for your input, I'm learning a lot thanks to you.

everydayflyer

In that case 3.3 would be the correct setting. A123s settle to approx. 3.45 per cell shortly after charging to 100% capacity.

Charge set at 3.3 then change to 3.6 and note the small mAh capacity added with the higher setting.


Charles

cobrajocky

Gotcha on the 3.3v, but at what point do I "change" to 3.6v? And should I choose the max amperage for the charge (5 Amps) or something lower? The "program" for all three types of Lithiums batts allows a longer max charge time of 10 minutes - should I go longer or shorter?

Thanks
Keith

dirtybird

My Feedback: (5)

I saw an ad for VPX batteries on ebay. $28 + 9.95 shipping. Now that Walmart is out I guess this is what you will have to pay

maninblk

I need an A123 battery pack at 4200mah, at 14.8volt, how can i achieve this or does anyone sell one that i can purchase?

cobrajocky

You aren't searching very hard, I just bought 3 more VPX packs for 16.09 each thru Amazon.com! No sales tax and free shipping since it was over $25. [sm=bananahead.gif] Ha ha ha.

B & D dumped Wal-Mart because Wal-mart wasn't promoting it at all in their stores. The B & D rep wrote on the B & D blog that it will be showing up in other mainline stores, possibly even at lover prices.

You're report of impending death of VPX as a souce for cheap A123, is premature sonny.[:'(]

bcchi

Wall Mart and Home depot is selling the VPX packs out a $7.00 They are no good. BCCHI

everydayflyer

They are closing out the VPX line due to the fact that they did a very poor job of marketing them and they did not sell well. Shelf space is very valuable and can not be taken up with low volum sales items.

The cells themself are great. HomeDepot made the same kind of mistake with the DeWalt 36V cordless tools and is why many of us got great deals on A123 cells by way of EBay.



Charles

cobrajocky

There was a recent thread on the B&D site where the VPX product manager swears that they aren't dropping the line, but it would now show up at stores like Target. We'll see.

With the way that B&D comes and goes with tool lines (I got burned on those costly VersaPak NiCD POS line about 6 years ago), anyone would be damn stupid to buy any Black and Decker power took! They have no credibility in my mind.

Charles, I'm still not getting good results charging my 3S A123 packs. The "Mystery" brand charger I'm using in auto program mode for LiON at 3.6v 3.3 amps says it's charged to 12.09v, but my 3S battery tester that they aren't peak charged. As I noted before, it also has a program for LiFE which only charges to 3.3v though. Max amps for any Li type batt program is 5A. I also balance the A123 packs, same results.

Here is the spec info on Mystery Charger - [link=http://www.new-energy-supply.com/d-p22077313-%5BSuper_Deal%5D_Mystery_B6_Charger_for_rc_helicop ter/]Click me[/link]

I does a great job of charging and balancing LiPOs and my NiMH batteries.

Any input or suggestions greatly appreciated, Charles.

My best,

everydayflyer

Correct setting for A123 (LiFePO4 cells would be

it also has a program for LiFE which only charges to 3.3v though.

That is not max. charge to but base(nonimal) voltage just like 3.7 is base(nonimal) voltage for LiPoly.

Cells should charge to 3.6 each and be approx. 3.45 a few minutes after charge is completed.

It is best to charge at 1C,then 2C then 3C when new.


Charles

cobrajocky

So you're saying charge using the LiFE setting (3.3v) but it will still take on a charge of 3.6v (3.45) even at the LiFE setting?

And, when the A123 batts are new, only use 1C (1.0 A?) and as they get older raise the rate to 2C (2.0A?) Or are you saying charge them once at 1A, then again at 2A and them again at 3Amps?? How long do I keep doing that? first few charges or until the batts are "seasoned"? Life a couple dozen times?

Do you ever do a "balance" charge separately? (I made my 3S packs with balance connectors)

Sorry for all the questions, A123 is totally new to me as apposed to NiMH or LiPO.

chadr

The charger specs would indicate it charges to the max voltage of 3.6 for life, just like it should charge to 4.2 volts for lipo:

LiPO
Vultage level: 3.7V/cell
Max.charge vultage: 4.2V/cell
Allowable fast charge current: 1C or less
Discharge vultage cut off level: 3.0V/cell or higher

LiFe
Vultage level: 3.3V/cell
Max.charge vultage: 3.6V/cell
Allowable fast charge current: 4C or less
Discharge vultage cut off level: 2.0V/cell or higher

everydayflyer

The initial 1C then 2C then 3c charges are to alow the cells to form /condition. The discharges folowing these charges should also be at reduces rates such as 2c,4c,6C.

Number of cycles required will vary with the cells / packs. If one observes the charges and discharges it can been seen when the cells are staying together.

I have had AA123 packs which were near perfect from the first cycle and I have had others which required 15-20 cycles to settle in. I have had two 5S apcks which required a cell to be replaced as the cell was still laging behind the others afte 40 cycles or more.

A lot of this conditioning depends on how hard you are going to use them. The same type of discussions on LiPolys have been going on for years. If you get 15-20 minute flights / runs from a battery then that is an average 3 to 4C discharge rate and is not hard on them. If you get an average 5 to 6 min. flight / run then that is a 10-12 C avaerage which is much harder on them. In addation to the average C rate during discharge the depth of discharge makes a big difference. Discharging greater than 90% from A123s causes them to heat up more and also can cause greater inbalance.


Charles