Originally Posted by areid

I've used a cheepo turnigy switch mode bec from HK in a mid range dlg with zero issues, but am hesitant to trust it (or their higher amp version) in anything larger/more expensive.

I have had such good reliability with the Turnigy / Hobbywing "8a, Max 15A" switching type unit (from HK or similar), that I now use it with 2 cell LiPo's in all my expensive gliders such as Pace F4, 4m mouldies, etc. The unit allows you to select 5v or 6v output. The switch is an "open circuit to ON" (i.e. if it gets disconnected, the unit defaults to "on". There are voltage warning lights. The power output is a y-lead with 2 servo type connectors, and a ferrite ring. I love it.

This one?

http://www.hobbyking.com/UNITEDHOBBI...idProduct=6233

And this one looks to be the same unit branded differently:

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

The features look good, but the dimensions seem like it may not fit into an F3B or F3F plane....Might be the hot tip for a slightly bugger fuse, or in a scale sailplane.

R,
Target

[QUOTE=areid;20111634]Interesting thread. I also like using LiFe's and get a bit nervous running without a regulator (despite in theory the peak voltage is less than a 5 cell NiMH)."

Intersting comment Areid, cause when I have commented about this I can guarentee you that the off the charger voltage is signaficantly less that 5 cell NiMh (Cd). I use a balancer every charge just to see the voltages on each cell just so I know that all is well in the pack. I am coming off the charger at ~6.7V +/-.05V. If I remember correctly (it has been that long since I have used NiMh's), I routinely saw NiMh packs fresh off the charger at atleast 7.0V and sometimes up to 7.2V. I must admit that I have never ever worried about LiFe's sans a regulator or BEC using JR servos, both regular or HV. I have learned the lesson that devices that are controlling voltage are just another site of failure in the system.

Now, with reference to the MKS servos, that is another issue and I guess I realize that they sound nice but how do you bring a servo, in this day and time, to the market that does not handle voltages in the 6.0-7.0V range. The first time I heard about this, I kind of thought the heresay was not possible, well, the guy the Mark Miller was talking about I also know and he nearly lost a ship over it. I guess that is another story, sorry for the opinion.

Marc

Originally Posted by OVSS Boss

... I am coming off the charger at ~6.7V +/-.05V.
Marc

Hi Mark, wondering what charger you are using? Most I am familiar with will charge LiFe 2S packs to well over 7v right off the charger (while it's true under load they soon drop to ~6.8). Maybe your balancer puts a significant load on the cells after the charge cycle is done?

Chris B.

I am using the Thunder Power 1010 with the external balancer. I am guessing if your voltage is different it has to do with the programming, but I am not sure. The voltage I am seeing has nearly no deviation from that value.

Marc

Here's an interesting story. Kyle Dahl, who is one of the current heli hot shots, has a fleet of 3 identical Logos. All have a BEC that gives either 7.4 or 5.2 volts. Turns out 1 of his 3 primary helis had the BEC inadvertently set to 5.2 instead of the 7.4 of the others.

Over the course of flying all three helis in a short period it was not until after he was done flying that the setting error was discovered. In other words, he could not tell the difference between 7.4 volts and 5.2 volts when it came to the performance of his helis.

Kind of makes you go Hmmmmm..................

I use the LiFePO4 packs because I love how they perform, not so much because of the absolute voltage. Nice steady voltage over the useful charge. I am not going to put in my planes any servo that cannot handle the packs I want to use without a regulator.

Originally Posted by Silent-AV8R

... I am not going to put in my planes any servo that cannot handle the packs I want to use without a regulator.

Then either you're choosing from a small subset of the best performing servos out there OR you feel safe with exceeding manufacturers spec voltage limits. I'd rather not use a regulator or voltage reducer either but... careful selection of the best one for the job can greatly reduce the risks of using one. I'm pretty confident this thread will help with that!

Chris B.

And now ask him which servos are IN the sailplanes he flies!?

R,
Target

Then either you're choosing from a small subset of the best performing servos out there OR you feel safe with exceeding manufacturers spec voltage limits.

Both are true. So it is more correct to say that I am choosing from a small subset of the best performing servos out there AND I feel safe with exceeding manufacturers spec voltage limits.

I use Futaba S3150 and S3155 servos on unregulated 2S LiFePO4.

Bill,
You outlaw!

Tom

This forum really is much better than TV.

Originally Posted by tewatson

Bill,
You outlaw!

Tom

Yep, livin' life on the edge.

Originally Posted by SoaringDude

Hi Mark, wondering what charger you are using? Most I am familiar with will charge LiFe 2S packs to well over 7v right off the charger (while it's true under load they soon drop to ~6.8). Maybe your balancer puts a significant load on the cells after the charge cycle is done?

Chris B.

My iCharger has a 'storage' mode charge option. I use this immediately after doing a full ballanced charge and it brings the 2S pack voltage down to the recommended storage charge of 6.6 volts. In observing its discharge amounts, there appears to be only 40 mah removed to get it down to this voltage, I thus fly with it that way and so I don't need to ever worry about those peak spikes created during the charge and certainly don't miss the 40 mah for flight.

Originally Posted by target

This one?

http://www.hobbyking.com/UNITEDHOBBI...idProduct=6233

And this one looks to be the same unit branded differently:

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

The features look good, but the dimensions seem like it may not fit into an F3B or F3F plane....Might be the hot tip for a slightly bugger fuse, or in a scale sailplane.

R,
Target

Yup, those are them! I have managed to stuff one into a Pace F4 which has a very small fuzz, so it can be done...

Originally Posted by SoaringDude

Then either you're choosing from a small subset of the best performing servos out there OR you feel safe with exceeding manufacturers spec voltage limits. I'd rather not use a regulator or voltage reducer either but... careful selection of the best one for the job can greatly reduce the risks of using one. I'm pretty confident this thread will help with that!

Chris B.

Chris, I was through the Horizon Hobbies office last week and saw the most amazing thing, LiFe's everywhere. Peter Goldsmith, Team JR Leader and John Diniz, JR Line Manager, have LiFe's in their ships and Horizon will have a line of them for sale soon. No regulators, nothing extra in sailplanes but the batteries and normal parafanial. At least at JR, servos are tested to higher voltages. And those of us that fly them in 2S LiFe set ups have no problems.

I realize that there are folks that put more time on their ships than I do in a year, but I fly comps all the time, my set ups have to hold up and be reliable. Just like Bill M., the attributes these batteries bring to the table are just just too good to pass up, sans any regulators*.

Marc

*Do remember Chris, I lost a ship because of a CC Reg that failed in flight, and as was pointed out to me, everything works great till it fails...