M11 / LiPo conversion charging question
 

I've installed the Losi LiPo transmitter pack in my M11 and am VERY pleased with it thus far.

Something that DOES puzzle me a bit is that Losi recommends not allowing the voltage to fall below 11.1v where my understanding is that LiPos are GENERALLY good as long as they aren't discharged below about 3v/cell (9v in the case of a 3-cell tx pack). When I asked about this on the Losi customer service line they said something about this being the 90% charge point or something.

Anybody have some insight?

tia,

Scottrik

That sounds a little odd to me as 11.1v is the nominal voltage of the 3 cell lipo pack. I run an HT Batteries lipo in my M11. Usually, it charges up to 12.5v and hangs around 12.1 for a while, but it's dropped down to 10.3 or so before I've charged it.

True, though.... you don't want to go below 3v/cell or you could risk damaging the battery. Oh, and make sure you charge the pack outside of the radio! :nod:

Thanks for the input.

LiPo rookie here...why must the battery be recharged outside the radio?

It "must" be charged outside the radio so you can keep an eye on temperature, and should it blow up or fail it won't take the radio with it. Just like for safety you should always charge your NIMH or LIPO battery out of the car. In case of failure less property damage will ensue.

In theory too if heat starts to build up it won't dissipate as quickly if it's cooped up inside the radio.

Thanks for the info Wes.

Approx. what level would 75% be?

So even though it's "recommended" to remove the battery it's not absolutely necessary? I know guys are leaving batteries in cars and racing all day just charging between heats. I don't even plan to charge at 1-C (maybe 1/2-C?) so should heat be an issue.

Similarly, balancing. On a battery subjected to such low charge/discharge rates is balancing done every charge? Every, say, third charge? Ever?

I've been very happy with the battery thus far but am not overly keen on having to ante up to replace it either. A local bought it figuring he could wedge it into his Nomadio. And couldn't. He sold it to me unused but fully charged and I've now done 3 club race days (2 classes of 1/12 each day), a test-n-tune day and a race down in Denver. Still shows over 11v. My NiMH batteries would NEVER last that long. A two-day was about all they were good for.

Another reason to charge the lipo battery outside the radio is due to the balance lead/charger. In order to properly charge a 3-cell lipo it should be done on a balance charger which has a unique connector not found on the radio.

Most likely, the 3-cell lipo will have a 4-wire Hyperion or Align connector on it which you must plug into the charger. Not only will charging through the radio not completely charge each cell in the 3-cell pack, but it is also dangerous as you can't observe the battery.

If the battery starts to swell while charging or even get warm.... RUN!:lol:

Well, more seriously, immediately stop charging and disconnect everything as a warm lipo or a swelling lipo is a bad sign.

I have never heard of any sort of problem with losi lipo's. do you have any specific examples? anybody else?

This must be a mistake in the instructions i am quite sure. I have taken mine down to 9.6V and it has charged back up without any problem and have been at low 10's too. Mine is the helios version and has been working great for several months now. ;)

Balance charging is not required IMO. While it will keep the battery in optimal health, even Kokam has stated that balancing may not always be required. After several hundred cycles they are finding cells staying with 1% of one another, more than safe.

However I do balance every now and then because I have a balance charger, I might as well. Generally every 5 or so cycles I throw it on the balance charger because you might as well do it right if you are going to do it at all.

I would not let the battery go below 10v...that gives you plenty of radio time AND plenty of cushion so you don't over discharge. Most radios have some sort of low voltage warning.

I charge mine in my radio, my last radio (M8) I retro fitted a battery into the radio and had to take it apart to get the battery out, so I just made a charge lead and charged it in the radio. I did what you were saying, 1/2C charge and it never got warm.

Also there is no reason why you could not just open the bottom of the radio and plug your balance connector to the battery.

I've actually gone back to NIMH though because I like the weight of the radio, the ballast in the bottom keeps it from tipping over when I set it down.

Excellent--thanks Mr. Wes!

I WILL have to keep an eye on the voltage, though, because I'm pretty sure the alarm doesn't begin to sound until it's WELL below 10v. In fact I don't think it sounds until substantially below 9.

I'm also guessing I won't want to push TOO far as it seems the discharge profiles I've seen for LiPos would indicate that they drop pretty fast at the end of the cycle.

mine goes off 9.9v i also use the ht. i generally charge mine around 10.9v but during test sessions it has run to the alarm more than once takes forever to recharge but never a problem. i wouldn't make a habit of it though.

each lipo cell has a minimun of 3.7v and the battery should not discharged less then that. 3.7 by 3 is 11.1 so dont go lower than that or you will lose battery life and it will take less charge. ask apogee or vxr there are makers of most lipo even losi lipos

Just received this note from Losi customer service:

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Scottrik,

They can be discharged down to 9.0V but would recommend that they not do this every time. This is a misprint on our part and we are going to post it on our web site soon.



If you have any other questions, please let us know!



Thanks,
Nathan Brady
Product Support Team Member
Horizon Hobby Distributors
4105 Fieldstone Rd.
Champaign, IL 61822
877-504-0233
[email protected]

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Which pretty much agrees with Wes' observations.

Thanks all.

thanks i was looking for the same answer