Born2Run

Can someone tell me what runtimes have to expect from the 4800 platimum with a brushless 4.5 on FDR 8.0 please?

linger

iTrader: (1)

Kuzo,
I once got into a discussion about cell balancing with the Engineers at a battery manufacturer. They were saying that most of the cell balancers for the RC market do not work correctly. I didn't understand what they meant at first, but after spending months trying to understand how commercial cell balancing chips work - I think I finally get it.

Let's say you have a two cell pack where both cells are fully charged 100%. Even though the manufacturer matches the cells prior to assembly, no two cells are exactly alike. Assume you partially discharge the pack by taking out 1.0 Ah out the pack. Both cells with the same initial voltage will probably be at slightly different voltages during and after the discharge. If you charge and put 1.0 Ah back into the both cells - they both reach 100% charge perfectly.

Now assume the same scenario, where you start with both cells 100% charged and you once again take out 1.0 Ah. This time you attach a balancer that bleeds off current from the higher cell and now the voltages are matched. Now you remove the balancer and recharge the pack. The cell that was brought down by the balancer is now not fully charged and the cell that was at a lower voltage during balancing is now overcharged. The cell balancer actually created a cell mismatch!

The bottom line is that passively balancing cells by forcing a matched voltage of partially charged pack is actually useless.

The balancer should only be used when fully charging the pack. It's meant to bleed off current to specific cell only when any cell reaches over 4.20V/cell. This ensures each cell gets a full charge and no cell gets overcharged.

Checking for cells in/out of balance with a multimeter should only be done when the pack is fully charged.

linger

iTrader: (1)

....
crap double post

kuzo

iTrader: (11)

Interesting, I haven't had any of my packs get out of balance yet so I have yet to use the balancer but when I do, I won't use it in passive mode. So you are only really going to know the balance status at the end of the charge. If you aren't using the balancer in active mode, you'll only find out after you've overcharged one cell.

For example, I charge a pack that is .03V out of balance so the end result would be cell1 - 4.35V and cell2 - 4.05V. But I won't see this issue until after the charge. I guess the question that remains for me at least is - how bad is this? Obviously I would balance the pack after noticing this but what's the safety threshold?

linger

iTrader: (1)

kuzo,
30mV imbalance at full charge is not bad - one cell is at 4.215V and the other at 4.185V.
At 200 mv inbalance - then this become a problem since once cell is at 4.300 V and the other at 4.100 V. Charging a battery to 4.300 V just once isn't too bad. Doing this repeatedly is very bad. Each time you overcharge, the lithium ions start plating on the electodes and the cell starts forming metallic lithium. Metalic lithium is highly flammable and now you have a safety issue.

linger

iTrader: (1)

It really depends on how smooth your throttle finger is. With my non-calibrated throttle finger - the runtime with a 4.5 brushless is in the range of 8-10 minutes for on-road.

afung1

Ling,

What about using a balance charger like this one.

http://www.align.com.tw/shop/product...oducts_id=1142

So it will charge the individual cell to 4.2V, that should balance the two cells. I use it when I get home and fast charge the pack at the track with a series Lipo charger.

linger

iTrader: (1)

Anthony Fungus,
I don't know much about that align charger - but as long as it balances during a full charge - it should be just fine.

afung1

I think all the Align charger does is charge each cell to 4.2V and then stop.

academygaz

Hey guys, I think I might have a problem with my 4800.

I'm charging it with a Pro Peak Prodigy 2 charger (same specs as the Orion Avionics one - possible OEM?). All settings are correct.

When on track with a 27t motor, it feels mega punchy for the first 10 or so laps (laptime is about 10-12 secs), especially out of tight hairpins. After 10 laps, the 'punch' disappears and the car then feels like a regular pack of NiMH's.

I thought it was a balance issue, so I fully charged it until the charger said it was full, the pack peaked at 8.43v, then after about 20secs at rest on the charger, the voltage dropped back and started hovering aorund 8.34v.

According to my multimeter, cell 1 is 4.17v, cell 2 is 4.16v.

Now, that seems to suggest the pack is alright, doesn't it?

The pack hasn't been deep discharged (about 7.6v I think is the lowest), and hasn't been balanced. I got it secondhand in October last year, but the lack of punch has only been recent (the last couple of months).

Its done it with different chassis, different ESC's and motors/gear ratios, the only common thing has been the charger, the pack, and my radio (KO Helios/Spektrum).

Any ideas?

Born2Run

Even Orion Platinum doesn't live for ever.As all the batteries they have a limited circle number.This battery has been used over a year.How long do you think it would be like a new one?

The Rev

iTrader: (3)

"When on track with a 27t motor, it feels mega punchy for the first 10 or so laps (laptime is about 10-12 secs), especially out of tight hairpins. After 10 laps, the 'punch' disappears and the car then feels like a regular pack of NiMH's."

I've noticed the same thing in mod. the car is much faster for 3-4 laps, then drops off and flatlines. my packs are both new. I think it's just the discharge curve. it's not totally linear.

NiMo

I thought that was the norm (happens with both Orion 4800 and Trackpower 4900), 4-5 power laps then loads of good laps then a sudden slowing (or is it me falling asleep ).
I've never reached the LiPo cut off point.

bmmer701

iTrader: (17)

rev: are you using brushless or brushed motor?

i noticed that also when i'm using stock brushed motor. i'm not sure if it's a motor fade or something ...

MarkBrown

iTrader: (9)

Am I correct in thinking that for long-term (>1 month) storage of a lipo it is OK to charge the pack fully before storage? Does it say this somewhere on the Team Orion site? I'm asking because I noticed an article in Car Action that says you should store with 50% charge, which seems like a fussy thing to have to do.