szakcajaru

pretty much.
the thing with balancing any pack is that you have to consider the number of cells involved. with the older style nimh and nicd packs you had 6 individual cells the worst or lowest of which affected the rest of the pack's performance, a lot of variables considering the number of cells. with a lipo in most cases you're only dealing with 2 cells (2s) so while balacing occassionally is a good thing there really is no need to be as paranoid about it as its been my experience that lipos are more stable and remain more consistent within a pack than nimh's. once a month max should be plenty.

Duster_360

iTrader: (21)

Only observtion I'd add is the more expensive lipo cells are less likey to get out of balance - these are being closely matched at assembly and will remain in balance by themselves for quite awhile. Apogee maintains that high quality cells do not need balancing, period. Mot sure I buy that totally, but for top quality cells, I think balancing may be a touch overhyped.

Less expensive lipos use cheaper cells and are not matched -these are much more prone to get out of balance. These need more attention.

OTE_TheMissile

iTrader: (2)

Just thought of something; I've got an old Traxxas E-Maxx with an EVX and a pair of Titans. This was made waaaay before people put LiPo packs in R/C cars & trucks, so no LiPo voltage cutoff.

But if I get a pair of external cutoffs and put one on each LiPo pack in the truck I'd protect the LiPos from dumping, BUT, according to the manual the EVX will blow if it only runs on one pack.

Didn't someone make LiPo cutoffs with a siren that went off before the cutoff kicked in?

ratherBracin

good point

nutz4rcyktw

iTrader: (67)

Just to make you more comfortable with Lipos. I have run an Orion 3200 and two 4800s for more than a year and raced them every week. They have never been out of balance more than .001 volt between the cells.

We have several guys running Lipos at our off road and at the carpet oval and never had a problem with a Lipo batt yet. We had three NIMHs blow up in the last season. One blew part of its case onto the track from the pits and burned a small hole in the ozite.

Our track requires that all Lipos must be hard cased but does not require sacks. We have fire extinguishers and sand but haven't needed them for Lipos just NIMH.

HVAC25000

iTrader: (19)

They sold me an open package battery (without telling me it was open package), then refused to take it back when I contacted them the day I received it.

Don't buy from a company that sells used items and represents them as new. You could be getting a potentially explosive battery, or one that is just plain dead.

Worst service around, and very crooked.

racinmason

iTrader: (9)

So what are average charge times for a Lipo battery? I guess it would all depend on you charge settings but lets just say in general.

And when they say its a 2S2P battery, its a 2 cell battery wired in parallel?

and 7.4 volts and 11.1 are the average size batteries people are running, I'm guessing the 11.1v batteries are what the monster truck guys use or for really wild brushless setups?

They don't make a charger with a balancer built in?

What is the "C" rating they use when rating batteries, like a 20C constant?



Thanks for the info.

fiveoboy01

iTrader: (30)

"C rating" is the pack's capacity divided by 100.

For example, if you have a 5000mah pack, 1C would be 5. 10C would be 50.

So you've got 2 numbers to remember:

Charge rate should almost be always 1C so if you're talking that 5000mah pack then it will charge at 5 amps. SOME manufacturers(thunder power is one of them) say you can charge at 2C... With their own charger and batteries. I've never tried it, I know some do. Mainly charging at a higher rate will shorten the pack life from what I understand.

Discharge rating is also rated with the "c" rating. So if that same 5000 mah pack has a 20C(continuous) rating and a 25C(burst) rating, then it can discharge at a rate of 100 amps continuous with a 125 amp burst before you start to over-stress the pack. Exceeding the recommended discharge rate can result in much shorter pack life and in some cases damaging or "puffing" the pack.

Usually if you're charging at 1C you're looking at around an hour to charge a lipo unless it's been barely discharged.

As far as balancing, I use a balancer that goes inline between my charger and lipo. It gets balanced every charge... MAY not be necessary but it sure can't hurt.

For a charger I use the Triton Jr. and the Equinox balancer... Around 85 bucks for the charger and something like 30 for the balancer. The balancer is a direct plug in to the charger and Great Planes makes many different balance leads to fit the plug on your lipo. Here's a pic, as you can see the battery charges through the balance lead and balances at the same time:



There are better chargers out there with more bells and whistles, this one has worked fine for me. If I could do it RIGHT NOW, I'd get the FMA Cellpro 4S charger. Built-in balancer, tons of features and the price is awesome:

http://www.fmadirect.com/products.htm?cat=45&nid=4

My second choice(for a larger budget) would be the Bantam BC-6, this can charge up to 6 cells.

http://www.amainhobbies.com/product_...ducts_id/26730

OR for a few bucks more, the Cellpro 10s is also a nice choice:

http://www.fmadirect.com/new_applica...0s_charger.htm

Likely you won't need anything more than a 4-cell charger for car stuff. Being a helicopter guy, we use all sorts of different cell counts up to 12-cell lipos(well not me, I am not that rich ah hahaha).


All the info is a little much at first, I know it was for me. But once you digest it all you realize that lipos are way better than anything else

racinmason

iTrader: (9)

That info really helped! I've been into nitro for 7 years and the only electric stuff I've touched are my two Helis and my RC18t. It just seems like electric has gotten sooo much better(obviously) with the brushless motors and Lipo batteries over the years, it really has gotten my attention and wanting to give it a try.

Thats nice you can just plug a balancer right inline with the battery and charger.
And when you balance a battery, it refers to making sure the voltage is the same in each cell so they are even correct?

That triton charger, balancer setup looks pretty decent, I looked up the specs for the charger off tower hobbies, that nice you can charge other batteries too like nimh. To bad its not A/C and D/C.
You think the Super brain 989 is overkill?

a 7.4v 4000mah 2s lipo should give me pretty good run time right?

Briguy

iTrader: (125)

Some lipo manufactures say not to use any superbrain chargers . Not sure why .

fiveoboy01

iTrader: (30)

I'm not really familliar with the superbrain charger. I don't really know anyone who uses it, doesn't seem like a very popular one. That doesn't mean it's not any good... But I can't really comment on it as I have no knowledge of it.

I think I remember someone telling me they get around 20 minutes of runtime with a 5000mah 2S lipo in their brushless 1/10 scale truck. BUT, that's going to vary a lot depending on motor, gearing, track and your driving style.

You can get a low voltage cutoff to prevent damage to the lipo but I prefer to just run a few times and time it... Then recharge and see how many mah you put back into the pack. Do NOT get a charger that will not tell you how much capacity you put back into the pack, you really need to know this number so you know how much you're taking them down. Over-discharge a lipo and you will likely ruin the pack or severely shorten it's cycle life.

I follow the 80% rule, which is not to take more than 80% of the pack's capacity before recharging.

So for a 5000 mah pack, when recharging I'd want to see no more than 4000 mah put back into it after a run(or however many runs it would take to drain that much out of the pack).

Remember that the less capacity you drain from the pack before you recharge it, the easier you are on it and you'll get more life/cycle out of the pack. So if you're pulling 2500 out of it during a 5-7 minute qualifier, if you have time, recharge it before the next one. It's better for the pack to pull 2000 out of it then recharge and pull 2000 out of it again, than to pull 4000 out at once then recharge. You CAN do that(stay at or below that 80% number) but I like to take as many steps as possible to make the packs last longer.

Briguy

iTrader: (125)

I run a 10.5 brushless in my truck with an Orion 3800 and get about 32 minutes before the cut-off kicks in . IMO if your ESC does not have a cut off you need one . They are cheap and save you from ruining a $100 battery .

racinmason

iTrader: (9)

I don't really do any racing at the time, mostly playing around in parking lots or the park, yard etc.. so the longer the run time, the better.

I know you have to be careful about how far down you drain the batteries, I have a Blade CX2 heli and a Blade 400 3D and they both came with LiPo batteries, for my cx2, I always fly till I notice a difference in power then stop.

So if you know your battery is capable of a 20min run time, you're better off using maybe 10-12 minutes of it, stop, charge it and go again? Can you do that? I guess your charging time would be less and better for the battery life.

There is alittle time required for cooling for the battery between runs and charges isn't there?


Briguy. 32 minutes of runtime!! Thats very impressive. how do you keep you ESC and motor cool. I would think things get very hot after 30 minutes, even 15 minutes...... If 32 minutes of run time is possible, I can't wait to get to battery power.

Don't most popular brushless setups come with a low voltage cutoff or do you have to add that yourself? for example, the Traxxas velineon system or the Castle creation sidewinder?

Thanks again guys for this info.

Briguy

iTrader: (125)

Some brushless escs come with lipo cut-off and some don`t . The esc and motor don`t have a problem with overheating at all . ESC has a fan on it and was going to put a fan on the motor but only gets to 100 degrees . We run on a big track and it`s geared kinda tall and still doesn`t get hot .