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Lipo Basics, What Do I Need To Know

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My Main buggy is the DF-03, can anyone recommend two things for me:

A 5000mah lipo battery to fit the DF-03 chassis

A good charger for Lipos

i'd like to get two batteries and a charger and try and keep the cost below say £120.

Cheers

Don't know if it's available near you, but I just got a Thunder AC6 charger for $55usd and it works great: DC input, 120-240v AC input, Lipo/Life/Nimh/Nicad up to 5amps, up to 6-cell lipo blance board, PC monitoring software, temp sensor, and a huge array of cables and adapters...

http://www.hobbypartz.com/thac6smbachw.html

AC6-Charger.jpg

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I needed to turn the pack around and put the wires to the rear when I fitted Li-Po into the Grasshopper. This needed 2 sections cut out from the chassis for the wires to exit from. One for the battery wires and the second for the balance tap. LiPo packs are slightly longer than Ni-MH/NiCd. I connect the ESC/Battery above the gearbox.

I get over 2 hour runtime on my setup with crazy fast speed if you use more than 1/2 trigger. Running IP4000 Li-Po, MambaMax 4600Kv brushless fitted to the gearbox with a Lunchbox motor mount and the long brass 10T Lunchbox pinion. Top speed is around 55km/h, but most times it's never driven at more than 1/2 throttle.

Cheers for the reply.

Any chance I could see some pictures of your Grashopper particularly the areas that pertain to LIPO conversion.

I guess so far I will need a LIPO charger, battery, and maybe a esc. Will the silvercan be happy with LIPO power?

Thanks

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If not running a lipo-ready ESC, you will also need a low-voltage-cutoff. If you discharge a lipo below a certain point, it will ruin the battery. Then if you try to charge it again, it may turn into a fire.

Look for lipo alarms or Low voltage Cutoffs...

What's a good LV cutoff setting for my EZ run 5.5 running on 4900 25c saddle packs? The ESC gives a cutoff option range between 2.6 and 3.4v per cell in .2 increments.

Thanks!

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What's a good LV cutoff setting for my EZ run 5.5 running on 4900 25c saddle packs? The ESC gives a cutoff option range between 2.6 and 3.4v per cell in .2 increments.

Thanks!

I would run it at 3.4v. You definitely don't want to go below 3.0. The less you discharge your lipo, the longer they will last. Popular opinion on rctech right now is to only discharge 75% of your capacity when racing...

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Can a Futaba MC330 ESC and a TEU 101BK handle lipo's? and are Lipo's waterproof too?

Thanks

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Can a Futaba MC330 ESC and a TEU 101BK handle lipo's? and are Lipo's waterproof too?

Thanks

Any ESC that runs on 7.2v, can also run 7.4v. When a 6cell nickle battery is fully charged (a really expensive one), it can put out as much as 9volts. A 2 cell lipo cannot go over 8.4v at full charge without being irreversibly damaged. The only extra accessory you need would be is a low voltage lipo alarm. This keeps you from over discharging the pack (you CANNOT run them flat). Just look on eBay for those $2 lipo alarms from Hong Kong...

You probably don't want to submerge a lipo. I do know people kill the chemistry on purpose by giving them a salt-water bath after a full discharge.

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Can a Futaba MC330 ESC and a TEU 101BK handle lipo's?

The ESCs can handle lipos no problem, the problem is the lipos can't handle being run on those ESCs without adding a low voltage cutoff. Without a cutoff those ESCs will keep on going until the voltage is below the minimum voltage of the lipo, which will kill the lipo pack.

and are Lipo's waterproof too?
Do not run a lipo anywhere near water, any water inside the pack will damage it.

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Any ESC that runs on 7.2v, can also run 7.4v. When a 6cell nickle battery is fully charged (a really expensive one), it can put out as much as 9volts. A 2 cell lipo cannot go over 8.4v at full charge without being irreversibly damaged. The only extra accessory you need would be is a low voltage lipo alarm. This keeps you from over discharging the pack (you CANNOT run them flat). Just look on eBay for those $2 lipo alarms from Hong Kong...

You probably don't want to submerge a lipo. I do know people kill the chemistry on purpose by giving them a salt-water bath after a full discharge.

Great info, thanks very much. :o

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The ESCs can handle lipos no problem, the problem is the lipos can't handle being run on those ESCs without adding a low voltage cutoff. Without a cutoff those ESCs will keep on going until the voltage is below the minimum voltage of the lipo, which will kill the lipo pack.

Do not run a lipo anywhere near water, any water inside the pack will damage it.

Thanks very much too, i'm thinking lipo is the way to go now. :o

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Thanks very much too, i'm thinking lipo is the way to go now. :o

You won't be disappointed.

A lipo alarm like this is very cheap and simply plugs into the battery packs existing balance tap. Once voltage drops so low, the lights turn red and alarm sounds very loud. I'm gonna be getting one very soon...

Connection.gif

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Apologies for the thread necromancy, but I thought seeing as this seemed to be the definitive resource for the LiPo newbie, I might as well stick my question in here :blink:

Just bought a couple of Flightmax 4000 2 cell 25C batteries, and have a question with regards to charging them. They've been supplied with a 4mm bullet connector lead (female connector on the positive, and male on the negative) and I'm just wondering what people use to connect these up to their chargers, as I can't find a charge lead that will fit. The closest that I can find at least appears to be a Losi EC3 connector, but that looks like that has two male connectors inside the plug. I'm loathed to chop the supplied connectors off and solder a deans female connector on. I'd have thought these kinds of connectors would be quite popular, and that a suitable charge lead would be easy to source, but no dice.

Am I missing something plainly obvious?

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For the 4mm bullet style lipos, I use the LBA-10-CAR harness from Hyperion. It' has two wires with 4mm bullets on either end, and three balance wires (one with a 2mm bullet). Provided your charger has a 6-cell balance port (7-pins), this should work fine for you. To use this with my Thunder AC6, I did have to snip off the locking tab from the 7-pin molex that plugs into the charger.

HP-EOSOUT-CAR02-Diag1.jpg

If you don't want to bother with that, or your not sure about the plugs, you can get something like this from Hobby King. I beleive they are recommended when purchasing your Zippy battery pack. If you don't like the Tamiya connector, you can always replace it with whatever you do use. The 3-pin balance tap should easily plug right into your balance board (depending on what brand charger you have).

http://www.hobbycity.com/hobbycity/store/u...?idProduct=9191

Tamiya-2S.jpg

And if you don't have a balance charger, you can always use alligator clips.

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Yeah I do have a balance charger, and I guess using Tamiya connectors for charging isn't a problem because there's a much lower current going through, so you don't need Deans or the like for that. That's the obvious thing I was missing :blink:

Thanks for pointing me in the right direction ;)

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What do the "C's" in lipo packs mean exactly? Like 20c, 30c etc.

Thanks.

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What do the "C's" in lipo packs mean exactly? Like 20c, 30c etc.

Thanks.

20C means it can discharge at 20 times it's capacity. 20 x 5000mAh = 100Amps. Higher the "C" rating the more punch the pack will have. Too low a "C" rating (like 5C in a Li-Po) is not suitable to power a 540 sized motor. These low power packs are suitable to power the transmitter or similar low drain applications.

Charging is also given a "C" rating, usally 1C. 1 x 5000mAh = 5Amps.

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According to SMC, the C rating specifically refers to the max discharge rate a pack can sustain while still maintaining 90% of it's capacity. The only problem is that this 90% figure is not an industry standard. Any brand can use any percentage they want to make their numbers better.

To give you an idea: A 40C pack, in theory, can be fully discharged in 1.35 minutes (using the 90% rule), regardless of overall capacity. A 50C could be done in 1.08 minutes. And all that without the cells themselves melting down. I seriously doubt any type of connector could even handle that much current and everything would have to be direct soldered.

Imagine this new Intellect 5600mah 50C pack being discharged at 280amps and surviving!!!! :)

IP560050CC.jpg

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Do not run a lipo anywhere near water, any water inside the pack will damage it.

Lipo's are fine in water as long as it is fresh water. No salt water or the connections will corrode badly. Same goes for NIMH though. Lipo cells are sealed up airtight so no water will get to them. If they were not then the moisture in the air would ruin them. One area to be careful of is the balance tap. In theory the tap wires are so close together that the water could short them==> in theory. A balloon around the taps fixes that.

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20C means it can discharge at 20 times it's capacity. 20 x 5000mAh = 100Amps. Higher the "C" rating the more punch the pack will have. Too low a "C" rating (like 5C in a Li-Po) is not suitable to power a 540 sized motor. These low power packs are suitable to power the transmitter or similar low drain applications.

Charging is also given a "C" rating, usally 1C. 1 x 5000mAh = 5Amps.

All things being equal, does this nean that the higher the c's, the faster the battery drains? Less runtime, more power?

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The higher the C rating the more amps the battery can supply, but it will only supply what the motor/esc calls for.

Example: If a motor capable of drawing 60 amps is hooked to a battery that can supply 100 amps the motor will only draw the 60 amps and the battery will easily give it. If the same motor is hooked to a battery capable of only 50 amps then the motor will still try to draw 60 amps and the battery will be overworked trying to give it.

Usually you what use the 120% rule and have a battery that is capable of at least 20% more amps than what a motor can draw.

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The higher the C rating the more amps the battery can supply, but it will only supply what the motor/esc calls for.

Example: If a motor capable of drawing 60 amps is hooked to a battery that can supply 100 amps the motor will only draw the 60 amps and the battery will easily give it. If the same motor is hooked to a battery capable of only 50 amps then the motor will still try to draw 60 amps and the battery will be overworked trying to give it.

Usually you what use the 120% rule and have a battery that is capable of at least 20% more amps than what a motor can draw.

I think it's quite important to mention that the C rating is tied to the capacity of the battery, I've seen ppl make the assumption that a, for example, 2000 mAH 30C gives more amps than a 5000 mAH 20C...

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hi all

I had to get in on this chat as i am buying Lipos at the moment.

So I have taken on board all the information. here is my small question, I have bult a SRB with standrad champ motor and 50A ESC what Amps would this need, Is it the speed controller that limits the amps or the motor that demands it. (if i put a more powerful motor in will it strain the ecs as well or will the esc limit the motor)

The batteries I am looking at now are 7.4v 3000mAh 35C which will give a constant drain of 105Amps which is more than enough for the set up i am using I think.

Please correct me if i am wrong

Thanks Mark

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hi all

I had to get in on this chat as i am buying Lipos at the moment.

So I have taken on board all the information. here is my small question, I have bult a SRB with standrad champ motor and 50A ESC what Amps would this need, Is it the speed controller that limits the amps or the motor that demands it. (if i put a more powerful motor in will it strain the ecs as well or will the esc limit the motor)

The batteries I am looking at now are 7.4v 3000mAh 35C which will give a constant drain of 105Amps which is more than enough for the set up i am using I think.

Please correct me if i am wrong

Thanks Mark

It is the motor that determines the load or current draw from the battery...

I would expect that 3000mAh 35C batteries should be more than adequate for the standard kit 540 motor..

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Yes, the motor demands the amps, but some ESCs have current limiters as well. The ESCs to look out for are cheap ones that advertise working with low turn mod motors (down to like 15T). These only do so by limiting the current to the motor and keeping the ESC cool. Due to the current limiters, you end up with the same cruddy performance no matter what motor you use.

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