Another Lipo thread
 

Not far off now and looking for a 3s and 2s pack, for around £150 for both ($300).

I like the look of the Flightpower ones bascily because they are in the UK and the quality, however, they don't do any higher capacities of a decent size over 3700mAh? I seriously don't want to make my own Lipo packs. So don't suggest it. :D

The TrueRc ones look too cheap to be true (no pun intended), they do a 3s 8000mah for $100... that seems great. Does anyone know the discharge rate and what they can be charged at too? Something I really want is to be able to charge it at decent rates, like 1C (for a 8000mah pack that is 8amps would I be right in saying?).

Thanks guys.

Just FYI, all Lipos can be charged at 1C. Some claim to be greater than 1C capable for charging, but in reality that's possible for all Lipos. Usually, greater than 1C charging is only recommended when either the charger has a built-in balancer or the balancer can communicate with (and alter the charge rate of) the charger, like the Thunder Power charger and balancers. The most important thing to consider when working with charge rates is if your charger can handle what you want to do.

The next size up in Enerland cells (the company that makes the Flightpower cells) is a 5000mah cell. This cell is a true powerhouse, it can sustain 30C currents (150amps!) pretty well, but is rated at 20C continuous. However, this cell is priced around $60 PER cell. I think for you Enerland cells are out of the picture (for cost vs. capacity).

The True RC cells have a graph that can be seen here:
http://www.rcgroups.com/forums/attac...hmentid=806053
Don't worry about the ending of the 6C (green) curve, that was just when the temperature cutoff cut in on the guy's testing equipment.
This cell is about a 8C continuous cell, but is capable of doing 10C for most of the discharge. There's no way that your car is going to be pulling 80amps average, so the discharge rate is fine.

Just chipping in w/ my $.02

I have been using the TrueRC 8000mah 3s and 2s wired in series for 5s on my erevo for the last few weeks. I gotta say, for the $... they are great. I charge them up and run for 45 minutes bashing around the bmx track. I ususlly have broken something before the batts were dead. The packs have never gotten even more than just slightly warm. Even running back and forth full throttle in a grass field. (the esc did though..lol)

I must say though... Charging them takes a while, at least with my charger. I'm using a superbrain 977. It will charge MiMH at 5A, but the Lipos it caps the 3s @ 3A and the 2S @ 2.5A. At that charge rate it takes a couple hours. to completely charge them. I'm thinking about getting the new Thuderpower charger. It is supposed to go up to 10A for Lipos. That would cover the 1C and then some. I'm also waiting to see what the new SUperbrain 989 is gonna be like. Is supposed to charge up to 8A on Lipos as well, and with the aded bonus of AC/DC right out of the box. But... These chargers only have 1 output, so to do both packs its 2 hours of charging time anyway. I can plug up and charge both batts at the same time on the 977.

Sorry for the ramble.... I kinda got off point.

Summary: Good batts...:027: Long runtime...:027: Good power.....:027: Low price...:027: how can that be bad?


EDIT: And dan is a pretty decent dude as well.

So why can't you charge the 8000mAh at 8amps? Isn't 1c the capacity divided by 1000 or something? So 3300s, 1c is 3.3amps?

His charger in limited in how many amps it can put out. 1C is equal to the capacity in Ah. Ah (Amp-hour) = mAh (milliamp-hour) / 1000.

Metalman is right. Its not the packs. Its the Chargers limitation. The packs can take 8A charge rate. My charger cant deliver more than 3A for lipo.

Sorry. didnt mean to confuse you.:002:

So these 8000mAh True RC ones are like 8c discharge? Is that abit low?

I believe you meant to say Ah = mAh / 1000

There is no such thing as a "low" C rate. Since these cells can handle 32amps continuously, and higher in burst, that's not too bad as long as you use a 2p setup for 8000mah and 64amps continuous.

Thanks :).

So will the C rating be fine with a 7XL? Running 5s2p/6s2p 8000mAh packs?

Still unsure what all the jargon means. :D

I'd worry about using 6s Lipo with a 7XL (for the motor's sake). Otherwise, that setup should be more than okay.

[QUOTE=jhautz]Just chipping in w/ my $.02
But... These chargers only have 1 output, so to do both packs its 2 hours of charging time anyway. I can plug up and charge both batts at the same time on the 977.[QUOTE/]

You can make a Y connector and charge them in series so it will only take 1 hour.

You can make a Y connector and charge them in series so it will only take 1 hour.

Which Lipos would you go for? I like the Flightpower ones but their capacity is abit low and I like the TrueRc ones but their protection and build quality looks low, how they use tape around them and all.

I would go for the TrueRC ones.

That assumes that the 2 packs are ballenced to each other pretty close to start with. That would increase the chances of overcharging a pack, wouldnt it?

I would make a y and charge in parrellal. that away you have the same in each pack. Start slow and then bump to a 1 c charge. I like this idea for it keeps the batteries the same for running in series. JMO

:002: :002: So by chargeing in series it will ballance the sells from pack to pack? Then whats the point of the balancers? I thought that the balancers were needed because they batteries would not equalize to each other when charged in series.:002: :002:

It doesnt matter anyway... The charger I have is only capable of chargeing 1s, 2s or 3s Lipos.

Balancers do a cell to cell in the pack.
I charge mine in parrlellal so the packs come out to the same voltage. I wouldn't try this with the nimhs but they charge differently.

Charging multiple packs at the same time with one charger can indeed be accomplished, but you should take precautions.

1 - NEVER charge packs of different manufacturers or different capacities together with one charger.

2 - Make sure the cells in each pack are balanced to the SAME voltage before the first charge. NEVER charge packs where the cells are at different voltages.

3 - Make sure that your charger can handle whatever configuration the packs equal when putting them together. If you're charging a 2s1p 2000 pack with a 3s1p 2000 pack in series, make sure your charger can do 5s charging at 2Amps or less.

4 - Regularly balance the packs to keep them safe when doing the multiple-pack charge.

Here's an example:

A. I have two 3s1p 3200mah lipo packs that I want to run in parallel. This means I am running the equivalent of 3s2p 6400mah.
B. I balance both packs individually during a charge to bring every cell to 4.2 volts.
C. I plug the two packs in parallel and run them in my vehicle. At this point, the cells will still be balanced (or very, very close to it) because they are all pushing the same amount of power to the vehicle.
D. After the run, I keep the packs plugged in parallel and attach them to the charger, then begin charging at 6.4Amps (3200mahx2=6400mah=6.4A).
E. After the charge is complete, go back to step C.

Repeat steps C through E a few times, then go back to step B and re-balance. You do not have to re-balance every time you charge as long as you are using the packs within their stated parameters. Don't charge to more than 4.2V per cell. Don't run below 3.0V per cell. Don't let the packs heat up (run within the amp rating of the pack). When lipo packs are initially balanced, then used properly, the cells will very rarely go out of balance during the usable life of the pack.

Remember, as always, the risk of using the technologies we talk about here lies solely on the user. Make sure you excersize sound judgement and make informed decisions on everything you do, including these sometimes potentially volatile toys we like to play with. :003:

Awesome info Thanks alot!!! I didn't know it was OK to charge Lipos in parallel like that.

Now I have one more question. I run 2 pack setup in series, not parallel. I have 8000mah 3s and 8000mah 2s pack (same cells, same manufacturer) that I run in series for a 5s configuration. Is it OK to charge these packs in a 5s series configuration? In the example you have above you were using a parallel configuration for discharge and charge.

Yes.
You would balance both the 2s and 3s packs INDIVIDUALLY in an initial charge, run them as a 5s (series) in your vehicle, then hook them up as a 5s to your charger.
In your specific case, your charger needs to be capable of charging a 5-cell lipo, and you'd be able to charge at up to 8Amps.
You should also make sure, for safety's sake, that you re-balance your packs every few charges.

FYI - In regards to your second statement, "I didn't know it was OK to charge Lipos in parallel like that." : your packs are already parallel, I believe. The lipo packs you are using are 2s2p 8000mah and 3s2p 8000mah, correct? If so, you are already doing what I showed in my example - your packs are parallel in their packaging, whereas my packs were paralleled by my own wires.

So it would be worth t for me to upgrade to the new TP charger. I could charge both packs in only an hour.

jhautz, the thread invader. :005:

sorry. my bad...:007: :032:

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