mrkab

iTrader: (3)

So if I have this straight you're saying I shouldn't lower the IR of my battery because *checks notes* my camber is probably wrong?

Ok so hypothetically if I put the car together correctly and the camber is correct is a lower IR better or worse?

mrkab

iTrader: (3)

Which part specifically is outdated? Is lower IR better or worse? Does cycling not lower the IR, even if only temporarily and at the expense of longevity? Why do they show a lower IR after cycling?

gigaplex

iTrader: (2)

Lower IR is better, but cycling at high rates only temporarily lowers the IR a small amount at the expense of the health of the pack. Unless you're replacing them regularly, you'll actually end up with lower IR over the life of the battery if you don't cycle them aggressively.

I don't cycle my 6-12 month old packs and their IR is about 1 mOhm per cell after a normal 10A charge.

Roelof

A lower IR will only work with you if you have the rest of the setup set to the max. So the max rpm out of the motor, the best car setup and most important the best driver.

staiguy

iTrader: (7)

what good is more speed going to do if your alignment is so off that your car isn’t going straight? You can put it together perfectly but eventually after awhile it will need regular maintenance. Some crashes can slightly bend pins throwing off alignment. ceramic bearings or some titanium turnbuckles could be better then 30amp up/down/up. The weight and freer drag is more permanent and cheaper then pumping batteries. Although bearings need their maintenance too. Again I never said there wasn’t a benefit. Just that it’s marginal, especially if practice is a bigger overall improvement. If you aren’t regularly checking over your buggy, are you going to regularly check battery health? High up down charging destroys packs at a faster rate than a 1-2c charge.

oldfool

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slappomatt

I rarely get below storage voltage. usually come off the track at 3.9-4.1

I assume the heat is what kills them but as I said my last batch of batteries I have made sure they stay cool and they are already puffing. I swear high C car packs are just trash.

trilerian

iTrader: (51)

Here are the basics... Lipo battery works by a form of electrochemical reaction. Heat speeds this reaction up and you see a lower IR. High current cycling (charging, discharging, or a combination) your packs raises the internal temp of the battery, this is why it lowers the IR. High current cycling of your batteries can lead to performance degradation over time.

Personally, I use DRC heated lipo sleeves. I use them on the lowest setting, this heats up my batteries to above ambient temperature, but not high enough to cause any legality issues. And, this allows me to charge at 1-2C and not worry about hurting my packs. I will race packs for 2-3 years, I think my newest packs are over a year old right now.

Trust me, it isn't my batteries that are holding me back!


EDIT: To answer the OP. I use high $ racing packs. Since I am only replacing them every 2 years or so, I buy expensive packs from EA, Trinity, R1, and sometimes Fantom. I don't like the Sunpadow's, just fyi.

EDIT 2: If you are running offroad, don't overlook the A-main Protek packs. I have a couple second hand and they have stellar IR numbers. Packs that were over 2 years old had better IR than new Fantom race packs.

mrkab

iTrader: (3)

In other words it does exactly what bill and others describe.

So you're saying it works.

mrkab

iTrader: (3)

Ok but what if my car drives straight?

Lots of people here literally saying this is wrong, outdated, etc. when it's clearly not entirely wrong. "It's not worth it" is a very different argument from "it doesn't work".

I don't cycle my batteries, I charge at 1C when time allows and 2C when it doesn't. It's not worth it to me, I'm 1 second off the front anyway. I do notice the IR drop and my fastest battery has the lowest IR as well.

staiguy

iTrader: (7)

what high $$$ brands are you using? Lots of people at my track using gens ace redline, protek, fantom, team power, and trinity,. I use r1 and haven't had any problems. Protek seems to be a favorite but gens ace is a cheaper battery that more budget minded racers seem to go towards. Rotor Ron puts out a battery that, on paper, looks like a decent battery for the price. If your battery is at its lowest state when you store charge it your doing good. What is your charger that you use? My one battery that went bad on me was a cheaper battery but i suspect some solder broke somewhere on the balance area, I used to have one of those cheaper b6 chargers but now use an icharger x6. The new one has a 2 amp balance plug vs the other at only 1 so balancing takes about 1/2 the time. The new lets you choose a slow, normal, or fast balance if you in a rush or not. If you have been using them regularly then maybe the charger isn't balancing them that well and over time one goes bad before the other? running out of ideas :P Is the track surface or air temp really hot?


also pic of the battery?

Roelof

It is known, heat will lower the IR. For sure stock drivers do find it very important but stock motor draw less current so the gain of a lower IR is less noticeable. One steering error will cost you more time than a low IR can save the time.

staiguy

iTrader: (7)

Great! Keep up with the maintenance so it continuously runs straight. On the track are you driving straight, not over correcting, taking every turn, landing perfectly, etc. Diminishing returns - high amp battery cycling falls towards the top of this. More track time or a practice day would probably lead to faster laps and a better consistency than a little more battery juice. There is a level where you need to do this to be competitive, otherwise they would fall behind. Most people aren't at this level

Very true. Last time i brought up high amp cycling people started saying the same thing - dont do it, no advantage, dangerous, etc. If tracks banned this and made everyone plug into a X-amp limited plug the advantage would be gone. I'm not an electrician but it's more of the idea of actually enforcing rules with hard limits. Make your charger go over the mandated amp limit then..., FLIP, the breaker dun exposed you! Then you get a warning. Do it again and your race day is done or banned from the track.
I think the previous person talked about using something like a tire warmer to warm up the battery. This would work but in the opposite way of externally warming the battery rather than internally. Some dangers in this method too, especially if your in a rush and crank up the heat.

Roelof

I know a guy in the Dutch nationals who has more wires going to his lipo bag than only for charging. Because with charging there can be heat we have a rule that at the start of a race the battery may not have a higher temperature than 10 degrees C above the ambient temperature. This guy has a tire warmer in his lipo bag and heats his batteries to that temperature although external heating as internal by high amps charging and discharging is not allowed.
If I was a race director and would see that I would send him home.

trilerian

iTrader: (51)

In the US, according to Roar rules we can have batteries that temp up to 90°F for indoor races. Looks like they did away with the 1C charge they had for awhile too.

11.2.4.5.2 LiPo battery maximum charge rate- Please follow the written instructions provided with the battery by the manufacturer.
11.2.4.5.3 Maximum temperature for a charged LiPo battery pack shall be determined by the race director and posted in tech. For indoor races temp should be 90 degrees.

There are no rules stating you can't warm your battery externally or internally by high charge currents.