Lipo questions
 

I have an Emaxx with your 9L/9918 combo and am considering going with lipo cells,I see in your ad for the Warrior 9918 it says "useable with lipo cells" exactly what does this mean?

I am not sure "exactly" what it means, but I will forward this question off to BK directly and post a reply when I have a clear understanding of what this means.

While we'er waiting I have more questions.I've been asking around at local hobbies shops about a lipo setup for an Emaxx,but with very little success.They either have no idea or are strongly against it.I understand the dangers involved in both charging and bashing relative crashes but the extended runtimes and lightweight keeps me interested.What little I've learned is a company called ThunderPower makes a Lipo pack that has a built-in device that cuts the power before the cell runs down to low and damageing it self otherwise there is a regulator that can be bought and manually added to the pack.Is this accurate?

I already bought a charger that can charge Lipos.I currently run GP3300s,two 7 cell packs(14 cells=16.8 volts)and dont want to give up the excellent power,but I've heard that with lipo two 7.4 packs(14.8 volts) when fully charged is equal to 16.8 volts,thus no power loss.Am I hearing accurate information?

This supplier is cheaper than ThunderPower:

http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MEWA:IT

All of the concerns you mentioned are valid concerns. Care must be taken when using these cells to avoid costly and/or disastrous repercussions. Having said that, I too have been bitten by the lipo bug! I haven't gotten my hands on the safety device for avoiding over discharge, but I am careful not to overwork the cells. I have played quite a bit with the lipos in my tc3 and absolutely can tell you they are awesome. I did run some in my e-maxx a few times as well, but the packs I have aren't truly up to e-maxx duty, so I have been very careful. A 14.8 volt lipo pack, of the right configuration (strong enough to discharge at a high enough rate) will definately feel more like 14 cells than 12 cells (nickel cells). They seem to hold their voltage better and have excellent punch. The 11.1 volt lipos (Kokam 2000mah) that I use in my tc3 (used two packs in parallel -so 4000mah and 11.1 volts) seemed every bit as punchy or maybe even a little more punchy than my 12 matched, high voltage gp3300 batteries in the e-maxx! The 12 cell gps topped out a little faster (as voltage came back), but the lipos are impressive. The two Kokam packs also weigh about as much as 5.5 3300 cells, so the truck lost over a pound and had 4000mah worth of runtime! I will reserve my e-maxx for some better lipos in the future (some day, I will stock them in the store), but my budget and time hasn't allowed me to get the bigger cells. I would also try to attach the batteries in the truck in such a way that they are not prone to damage (from rocks being thrown by the spinning tires or bottoming out on a rock in the back yard, etc.). I have seen a 7xl motor run on 22.2 volts and it was about as crazy as you could imagine. The batteries put out a bit over 2000 watts in this truck (over 3hp!) and was pretty insane. The guy ended up overdischarging them on a run (ran too long) and ultimately destroyed the cells 9$$$ out the window). I say go for it, but be aware of the downfalls and take steps to avoid costly mistakes. Proper charging is another story, but it sounds like you have done some research already. Just be careful. I know I plan to keep using them!

Hey Mike thanks for being so prompt in your reply.MMMM,have you had any lipo/Emaxx experience as of yet? I'll take info you have to offer.

I haven't had a personal experience with lipos myself. I've just spent a lot of time researching them. The amount of mAh these things can have is amazing! I've seen 10,000 mAh packs!

Here's an overdischarge protection circuit for lipos. You'll need it if the pack doesn't already have one built in.

http://www.newcreations-rc.com/Produ...number=Lisaver

In order to keep the costs from getting to out of hand I was looking for something in the 6000 mah area.Its been awhile since I saw these numbers so correct me if I'm wrong,a stock Emaxx with Titans and 14 cells draws 30-40 amps continuiously and can have bursts of up to 70 amps.When looking for Lipo cells in a brushless setup will these numbers vary much?I've seen Lipos that can handle 60,90 and 120 amps,which is right for me? THX

What voltage are you gonna run? On 14.8 volts, I would look for something that can handle at least 60-80 amps continuosly and peak over 100 amps. A heavy truck with big tires and high traction really draws power on acceleration. You may get away with a weaker cell, but it will be pushed and will not last as long. The 6000mah packs you mentioned: what rate can they discharge at (12c? 15c?)? Got a link to them?

The Thunder Power Batteries list the discharge rates:

http://www.thunderpower-batteries.co...batteries.html

The 6000 and 8000 mAh batteries discharge at 8-10C with 15C bursts. The 6000 mAh batteries are rated for 48-60A continous and 90A bursts. The 8000 mAh batteries are rated for 64-80A continous and 120 A bursts.

I personally wouldn't buy less than the 8000 mAh lipo.

The 8000mah packs are the safer batteries for sure. There are other batteries with 12-15C discharge rates, and Kokam is said to be releasing some 30C discharge cells!

Thanks MMMM for listing the link,that is where I was looking.Because my charger can only charge 3 cells max I would have to go with 2 cell packs.2 packs of TP8000-2s4P 8000 mah at 7.4 volts.I didnt hear about Kokam but I did hear that Hitec was releasing some lipo packs though.I may have to hold up a bit to see what they have to offer.

I hope the prices come down. Right now they're just too expensive!

I spoke to Alex of BK Electronics at great length today. Basically, the voltage cutoff is 2.55 volts per cell when using lipoly cells. This is a little low if you talk to most people, though. Their next generation of controller will have a fully adjustable voltage cutoff, but they are a few months out. They are also working on a pair of controllers designed to work on low cell counts and up to 12 cells for cars. These new controller should be at or below the warrior controller prices, but will function better than the warrior on low cell counts (warrior has a 5.5volt bec cutoff, which causes problems on takeoff), while the new controllers will have a 3volt bec cutoff. This has been tested by some famous onroad guys in a touring car so far, and I should get one for testing in a few weeks. These won't be available for a few months, but it sounds as if it will be a great option for low cell counts at warrior level pricing! The 60 amp version will be released first, followed by a 95 amp version! They are working on some new motors as well that are said to perform as good or better than the Lehner motors at a lower price point. I will be sure to keep you posted on the availability and performance of these items as they arrive.