switching to lipo's, the formula.........

[94eg! 834]

And read this you strange people who think they know better

It is easy to find you know, its called google

especially read the part from Dominator

http://formuladrc.fo...2-lipo-c-rating

oh and note where the decimal place goes !!!!!!

its to change the mah's to amps.

I read his post (see below) and it was just about as clear as yours. It doesn't actually tell you HOW to convert. It just says to add a decimal. While yours told how to convert incorrectly. It's not a big deal, no need to freak out. I screwed up my post too, but I didn't flip my lid when someone pointed it out.

To calculate or understand a "C rating" you first need to convert the battery capacity from milliamps (mah) to amps which is really simple, you just at a decimal point. So it goes like this... a 5000mah battery is 5 amps, a 4600mah battery is 4.6 amps, a 4200mah battery is 4.2A... and so on. The amp number you just got is a "C"... so for a 5000mah battery, 1C = 5A.

Even still, you were way off base on the "too good an ESC will blow up your battery" reasoning. Imagine if someone "googled" up this thread and quoted your post as fact? They would be completely mislead as to the function of RC electronics. Google is not the answer. Research is the answer. Forums are just here to help people along with their research. There is as much or more misinformation on the internet than credible fact, and the way this thread was presented is testament to that.

[super gripper 419]

I read his post (see below) and it was just about as clear as yours. It doesn't actually tell you HOW to convert. It just says to add a decimal. While yours told how to convert incorrectly. It's not a big deal, no need to freak out. I screwed up my post too, but I didn't flip my lid when someone pointed it out.

Even still, you were way off base on the "too good an ESC will blow up your battery" reasoning. Imagine if someone "googled" up this thread and quoted your post as fact? They would be completely mislead as to the function of RC electronics. Google is not the answer. Research is the answer. Forums are just here to help people along with their research. There is as much or more misinformation on the internet than credible fact, and the way this thread was presented is testament to that.

sorry chap but it reads perfectly clear to me and yes it does. its a very good post by Dominator on formula DRC.com

[TA-Mark 195]

The bit I see missing from both your and Dominator's post is the explaination that the metric prefix 'milli' means 'one thousandth'. To say 'just move the decimal' could cause someone to make the mistake of calling a 280mAh (Micro-T Li-Po) as being 2.8Amp instead of 0.28Amp.

The only other error I seen in your posts supper gripper is about the ESC being the part of the equation. When it comes to current draw from the motor and current supplied by the battery, it makes no difference to the figures if there's no ESC in the middle at all (directly connected or 3-step MSC on the fastest switch setting - brushed of course). The ESC's current draw is negligible (the power used to make it operate) when compared to the current passing through it to the motor. The ESC only needs to be of sufficient rating to handle the current moving between the battery and motor.

[super gripper 419]

''The ESC only needs to be of sufficient rating to handle the current moving between the battery and motor''

thank you TA-Mark, this is what I have been trying to explain all along. ( in a round about kind a way)

yes moving the decimal. 4000 mah = 4 amps

top chap that man you know

[94eg! 834]

sorry chap but it reads perfectly clear to me and yes it does. its a very good post by Dominator on formula DRC.com

sorry chap but it reads perfectly clear to me and yes it does. its a very good post by Dominator on formula DRC.com

Yeah the post would have been good if it EXPLAINED the conversion. Unfortunately it didn't. All he had to do was say "To convert milliamps to amps, you divide the mah by 1000". Unfortunately it didn't, so it is NOT a good explanation. It also doesn't explain how you came to the conclusion about the speed control rating effecting the battery. You literally stated the battery would explode if the ESC was rated too high. I wouldn't mind hearing about how that came to be. The only thing the speed control has an effect on is motor performance (via frequency & resistance). Weather or not it can handle the thru-current is of no consequence to the battery or motor, only overal performance (or lack thereof). ESCs are just high-frequency on/off switches. The more switches they have (in parallel), or the better quality switches they contain, the more current they can flow without converting energy into heat.

[super gripper 419]

sorry, I thought the conversion from milli amp hours to amp hours was basic common knolledege.

[94eg! 834]

Not the way you explained it.

[Sayer 742]

Not the way you explained it.

These histrionics could have been avoided if instead of posting:

you need to put a decimal point after the first number of you batteries capacity.

he'd posted:

you need to move the decimal point three places to the left to get your battery's capacity in Amps.

And even if we're all a bunch of knuckle dragging mouthbreathers unworthy of his continued association, this:

by using an esc that has a higher current drain than your lipo can give this then in effect is taking too much out of the lipo during its 'burst' (the point when you ask for full power)

is still super-wrong and should have been left out of an informative post.

Edit- to fix number of decimal places

[TA-Mark 195]

One thousandth is three decimal places, not two decimal places. 5000.0 -> 5.0000

The metric prefixes are not common knowledge to those used to SAE (imperial) measurements and calculations. When I say milli-, kilo- or centi- to my dad he just looks at me stupidly.

The only thing having an ESC that is rated way more than you need hurts is your hip pocket.

[Sayer 742]

The metric prefixes are not common knowledge to those used to SAE (imperial) measurements and calculations. When I say milli-, kilo- or centi- to my dad he just looks at me stupidly.

I've got no excuse since I was actually taught in school the decimal place trick as a quick way to multiply or divide by powers of 10. Still though, that would have been far better than instructing people to just add a decimal point after the first number with no explanation as to why. You'd never have to mention metric prefixes and they'd still be safe from turning their lipos into fireballs.

On another note, the OP mentioned that Lipos swell when charging and contract when discharging. To the best of my knowledge, any such swelling is an indication of a problem rather than ordinary behaviour. Anyone with more knowledge of battery tech care to weigh in on that?

[TA-Mark 195]

On another note, the OP mentioned that Lipos swell when charging and contract when discharging. To the best of my knowledge, any such swelling is an indication of a problem rather than ordinary behaviour. Anyone with more knowledge of battery tech care to weigh in on that?

To my knowledge, swelling indicates a build up of gas. This gas build up happens in all battery types.

Lead Acid batteries have cell vents. Rust on the hood above the battery in an older real car is common and an indication of battery venting.

Ni-MH and Ni-Cd packs have vents on the positive end of the cell (sometimes covered by a piece of cardboard). I've heard Ni-HM cells vent in both charge and discharge. When the vents become blocked is when these battery types are dangerous and may explode (like a hand grenade).

Li-Po packs don't have vents, and expelled gases can build up between the layers of the cell structure if it becomes trapped. I have seen packs that have swollen during both discharge and charging.

Contracting would indicate a loss or absorption of the gasses, which doesn't sound right at all in a battery cell.

[wolfdogstinkus 1893]

So this battery http://www.ebay.co.u...=item53eb6878aa

30c 3300mAh would have 99amps constant and be fine with a 60amp ESC?

So fine with an EZRUN but maybe not with a Castle system? (If I ever get mine back)

30c x 3300mAh = 99,000mAh / 1000= 99amps constant

I don't know why they are still supplying batteries with a 99amp capacity with a 7.5amp connector? surely that is dangerous as if the connector fuses/ welds itself together with the heat, then you have no way of dis-connecting the power source in case of fire.

[GregM 1109]

Wolfdogstinkus, it's not the ESC itself that draws the Amps from the battery, it is the motor. So there's yet information needed about the motor you want to use.

[Gruntfuggly 562]

Anyone know if a TEU101BK will cope with 7.4v from a LiPo ? I've had a quick blast and it didn't instantly explode (not that I expected it to), but the specs only say 7.2v... it's running a Sport Tuned, so the load shouldn't be particularly high...

BTW - Wolfdogstinkus - I've just bought two 30C 4000mah Turnigy packs from the US for £32 (inc. delivery) - might be a better value option?

[wolfdogstinkus 1893]

Thanks GregM and Gruntfuggly, the EZrun system I have is actually the 35amp ESC and the 9T motor so not sure what the motor specs are?, couldn't find them when I checked the website, also waiting to get my Castle system back so ideally would like batteries that will run both systems.

I have also just found this battery which looks good.

http://www.hobbyking...Car_Lipoly.html

At £20 for two which seems pretty good, have never ordered from hobbyking so have no idea how much the shipping is? it looks to be around £7?

[atf300 28]

Anyone know if a TEU101BK will cope with 7.4v from a LiPo ? I've had a quick blast and it didn't instantly explode (not that I expected it to), but the specs only say 7.2v... it's running a Sport Tuned, so the load shouldn't be particularly high...

BTW - Wolfdogstinkus - I've just bought two 30C 4000mah Turnigy packs from the US for £32 (inc. delivery) - might be a better value option?

sure , you will be fine . i ran a tt01e with that esc exclusively on lipo and its still there . the lipos are 30c.

[Gruntfuggly 562]

Thanks atf300 - good to know.

Wolfdogstinkus - these are the packs I bought (as recommended by Shanks):

http://www.hobbyking...idProduct=21004

hobbyking seem to have some good value deals...

The shipping for two packs was $15.

[atf300 28]

Thanks atf300 - good to know.

Wolfdogstinkus - these are the packs I bought (as recommended by Shanks):

http://www.hobbyking...idProduct=21004

hobbyking seem to have some good value deals...

The shipping for two packs was $15.

i have exactly these. check in the hobbyking uk warehouse or the european german one. shipping is faster and no customs, also you can return them there if there's a warranty issue .

[wolfdogstinkus 1893]

Thanks Gruntfuggly, they look better than the ones I linked to, do they fit in place of a stick pack?, at 135mm long they might be a squeeze but should fit ok.

[94eg! 834]

I don't know why they are still supplying batteries with a 99amp capacity with a 7.5amp connector? surely that is dangerous as if the connector fuses/ welds itself together with the heat, then you have no way of dis-connecting the power source in case of fire.

There aint a connector around that can withstand 99amps either.

[Gruntfuggly 562]

@wolfdogstinkus - They fit perfectly in the cars I was hoping they would (Stadium Thunder, Dyna Blaster, F350 and Wild One).

@atf300 - I didn't know they had a UK warehouse? I should have a look and see what the cost would be. As for the warranty, unfortunately I've voided that already - had to change the Turnigy connectors for Power Poles. The Turnigy ones seem decent (although quite big) but I've converted everything else to Power Poles already...

@94eg! - When you think 99amps at 7.4v is just over 700 watts - you've got a good point!

[atf300 28]

Actually the warranty still stands, I'm not sure though. Decent batteries those, especially for the price. With a bit of dremeling you can fit them in most cars.

Also those 4mm connectors on the batteries are so so. I change them to my preferred xt60 system

[GregM 1109]

Anyone know if a TEU101BK will cope with 7.4v from a LiPo ? I've had a quick blast and it didn't instantly explode (not that I expected it to), but the specs only say 7.2v... it's running a Sport Tuned, so the load shouldn't be particularly high...

The ESC itself should be fine with that setup, but be sure to use a seperate LiPo low-voltage cutoff circuit, as the TEU-101BK doesn't have such a circuit incorporated.

[Gruntfuggly 562]

I've bought a small audible alarm module that plugs into the charging socket. It's pretty loud, so hopefully it will do the job. I'll have a look for a separate cut off though - that sounds like a good idea...

[GregM 1109]

FYI:

Retrofitting a LiPo low voltage cut-off to regular ESC http://www.tamiyaclu...showtopic=66249