Roar ruling on 8.5v
 

How do you feel about the guy next to you charging is lipo to 4.25 per cell?

I sometimes charge to 4.3v a cell... NO issues...


I know what I'm doing, IDK if the person next to me does though...


'overcharging' your batt is not dangerous if you know what your doing and have 'good' batteries(new, not puffed, low IR, etc). Its not until you get joe schmo that wants to get every last race out of his $150 battery that is 4 years old, puffed, and about to blow on its own, that you start to have issues...


Pay attention to your batts and you won't have any issues...

I charge to 4.2v per cell... but thats what ive always been told and thats what my "smart" charger is setup to do. i always balance charge as well.

sorry to sound like a noob, but what is the deal with this? why are they rated at 3.7v but charge up to ~4.2v per cell? EVERYONE i know or have seen at the track does this as well.

3.7v is the nominal voltage per cell, which means it charges to 4.2v per cell but will drop to 3.7 rather quickly then they discharge much slower. that's the best i can explain it.

i really don't see the point of overcharging your batts by such a small amount when they'll drop to nominal fairly quickly anyway. seems like it's just a good way to blow your batteries with no real benefits.

They're not really 'rated' at 3.7cv/cell, just referred to like that. This is called the 'nominal' voltage. Not much diff than a sub c or AA NiMh cell where they're referred to as 1.2v/cell when they charge to higher than that.



Supposedly, the 3.7v/cell is what a lipo cell drops to under load.....

All he is doing by over-charging his cells is lowering the lifespan of his battery

Any decent load on the pack will take it down anyway

Cheers

This thread comes from Roar changing the max allowable voltage at roar events to 8.5v.

At events, racers are going to push every rule to their limits. So if the max allowable voltage is 8.5v, they are going to charge their packs to 8.5v.

How safe is this? How much damage are you doing to your cells?

8.4v vs 8.5v, hardly a noticeable difference

Early non balance lipo chargers used to charge to 4.3v / cell

Once they started to realize it reduced pack lifespan people started to lower it

You seriously think there would be any performance increase at all ?

Have you seen a high current discharge graph ?

Look at how long the voltage stays above 4v


https://www.flightpower.co.uk/images...5000_curve.jpg


Cheers

What ROAR is doing is plain silly and dangerous. Here's why:

1. Most chargers are set to cut off between 8.4 to 8.44 volts. I've seen some mis-calibrated chargers take them to 8.46.
2. By allowing the 8.5 limit at racing events, they are essentially saying it's OK to take your pack to 8.5, which can only be done if you by-pass the charge limit. In my personal case I have a Much More silent charger. It cuts off at 8.40-8.41. The only way I could get it to reach 8.5 is to re-peak the pack in HiMh mode. If you do this you will have to sit and monitor your charger until it hits that voltage. What if someone forgets to do that??? Your battery will continue to charge.

Just my opionion as a race organizer and director.

I can set my Icharger anywhere between 4.1-4.3v a cell... just because your charger can't doesn't mean that others cant...

EDIT: I've found that the difference between 4.1v and 4.3v a cell is about 500mah on a 5000mah battery...

If the guy next to me feels that he needs an extra 0.1 volts in his battery to win then I say fill your shorts buddy.

Any how many cycles will you lose by doing that ?

Cheers

universal rule in rc and computing: no matter what you do, some weenie will seriously shorten the life of his kit to become a tiny fraction of 1 percent faster than you.

My question; is the above the reason ROAR is making the rule change? 8.5v doesn't bother me really. That 1/10th of a volt isn't going to gain you anything anyway, it's gone in the first 1/2 lap of warm up.

BTW my charger will let me charge to 8.6v......IF I want too

Apparently I missed this. Where did ROAR declare the upper limit to now be 8.5V?

I've had cheaper chargers that I found to be quite safe with my batteries, but showed a peaked battery above 8.4V during tech. This could be an effort to ease the burden of cost in upgrading to an adjustable peak LiPo charger [which I have upgraded to for the ability to adjust my peak to meet tech with less hassle].