LIFE or LIPO, 2s RX battery choice?

[martin collins 1]

I am just getting back into petrol aircraft having flown solely electric for the last 15 years and i fitted a 2s lipo into my first model with a voltage regulator, the engine is a mag version so no need for an ignition battery. My next model will have electronic ignition so i will need two batteries, one for ignition and one for the receiver, what are the benefits or otherwise of Life v Lipo? Also is it possible to have an external balance plug point so that the battery can be charged and balanced without having to remove the wing? 

[GrumpyGnome]

I'll let others answer re LiPo vs LiFe......

 

Re extended leads, yes, of course you can. But having flown electrics for 15 years, you know not to charge Lithium cells in situ.

[martin collins 1]

It is more for checking the percentage of the battery left without having to remove the wing in between flights.

[GrumpyGnome]

Ah gotcha. Yes, you can get extension balance leads for a few pounds. On fleabay for example.

[martin collins 1]

I have an extension lead, bought off ebay but was wondering how to mount it to the plane so i could plug in from the outside. Someone must have done it on their plane? 

[SIMON CRAGG]

Been using LifePO4 as RX packs for many years. 

Work fine.

[John Rickett 102]

Presumably the ignition unit will be 6v, an unregulated LiFe 2S 1000mA/h pack will easily provide an average day's flying and be safer than a LiPo. No need either to remove for charging.  

[Denis Watkins]

If you decide on externals

RapidRC 

 

 

[martin collins 1]

Switch is fine for charging a life battery but would still want a balance lead socket to check battery percentage remaining as it's going in a bipe. Undo u/c, remove wing struts, remove bottom wing to check the battery.... Got to be a better way! Maybe i will just run the extended balance lead into the cockpit for checking. Life battery on ign and a separate rx one, how many 10 min flights would you get on a 1000mah 2s? 

[Frank Skilbeck]

Life batteries are the same.voltage as a 5 cell Nimh so you can.use regular servos without a UBEC, with a Lipo you either need HV servos or a UBEC.

 

I'll just put a shoutout for Molicel batteries here, 2s are a great replacement for.a 2s lipo for.ignition or HV servo power supply.

Edited September 19, 2023 by Frank Skilbeck

[martin collins 1]

Thanks Frank, i thought you needed a voltage regulator with Life as well as lipo, i run 6v compatible servos and Spektrum rx's so i don't need a voltage reg on a 2s Life battery then. 

[Paul De Tourtoulon]

Why use 2 battery's, I only use one for the rc and ignition.

[Frank Skilbeck]

21 minutes ago, martin collins 1 said:

Thanks Frank, i thought you needed a voltage regulator with Life as well as lipo, i run 6v compatible servos and Spektrum rx's so i don't need a voltage reg on a 2s Life battery then. 

Yep a 2s Life charges up to 7.2v and quickly drops to.around 6.6v and stays there. It does make it difficult for the battery checkers to get an accurate % remaining reading as the main part of the discharge curve is very flat.

[martin collins 1]

41 minutes ago, Paul De Tourtoulon said:

Why use 2 battery's, I only use one for the rc and ignition.

Ok Paul, as mentioned i am new to requiring rx batteries having flown only electric for the last 15 years. 👍

[Frank Skilbeck]

1 hour ago, Paul De Tourtoulon said:

Why use 2 battery's, I only use one for the rc and ignition.

 

One battery is fine, especially with a magneto ignition 😁

[Don Fry]

2 hours ago, martin collins 1 said:

Thanks Frank, i thought you needed a voltage regulator with Life as well as lipo, i run 6v compatible servos and Spektrum rx's so i don't need a voltage reg on a 2s Life battery then. 

No, it all runs smoothly. Loads of power delivery, no sag. Point of interest, want to fly, now, don’t know what you have dragged out last time, even can’t remember last time, wack a 2C charge in. Before the cup of tea is drunk, it’s charged. No brainer.

[Dale Bradly]

3 hours ago, martin collins 1 said:

 how many 10 min flights would you get on a 1000mah 2s? 

I have 2x models flown regularly, with 20cc gas and 6-7 servos in each, and seperate 2s LiFe batts in the 1500mAh range for radio and ignition.

Typically they would be operated/flown/powered for around 20min per day. I find i put about 450mAH back into each batt. (Interestingly i find there is very little difference between radio and ignition batt for the same flight duration)

No need to balance charge every time, so this is easiset done at home when wing is off anyway. Likewise as im at no risk of taking batt any where near discharged on a typical day at the field, i dont need to check batt levels between flights.

Edited September 19, 2023 by Dale Bradly

[Martin McIntosh]

LiFe for me every time now, way more reliable than LiPo`s. I have one petrol model with one on ignition but run it through a 5V 5A regulator since I once got caught out using a 6V NiMh. It destroyed the plug and ignition unit (RCXeL) after just 6 flights.

You cannot use a checker on LiFe because it will always show 6.6V until the last few seconds of charge.

Very few servos these days will not run on 6.6V. I have a Bipe which uses four on ailerons, two are normal and the other two HV because they were the only ones available during a lockdown. No difference in speed so I reckon that HV ones simply have a regulator on the amp.

[martin collins 1]

Interesting Martin, i understood from others the Life could be used unregulated on the Rexel ignition unit 🤔. The Fusion battery checker i use does Life batteries and gives a percentage of battery on it, i would be using that rather than volts, presumably that is a pretty accurate way of seeing how much is left in it? 

[martin collins 1]

1 hour ago, Martin McIntosh said:

It destroyed the plug and ignition unit (RCXeL) after just 6 flights.

I am glad you mentioned that Martin, after research different Rexel units seem to have different voltage limits, some can handle up to 20v, mine however says 4.8-6v, a Life rx pack would have blown it as you found out! So the sweeping comment from a number of people re using a Life or lipo on the ignition is not always correct, i guess i will have to put a v regulator on it.

[martin collins 1]

One of these should be here tomorrow to drop the voltage on the Life rx pack to 6v.  https://wheelspinmodels.co.uk/i/103493/

[Manish Chandrayan]

2 hours ago, martin collins 1 said:

I am glad you mentioned that Martin, after research different Rexel units seem to have different voltage limits, some can handle up to 20v, mine however says 4.8-6v, a Life rx pack would have blown it as you found out! So the sweeping comment from a number of people re using a Life or lipo on the ignition is not always correct, i guess i will have to put a v regulator on it.

Martin, the older Rcexl ignitions were meant for 4.8-6v and marked so accordingly. Check your new ignition and the compatible voltage should be clearly indicated on the ignition. Current one's will work perfectly on 2s LiFe and I personally prefer separate LiFe packs for ignition and Rx unless the model demands ballast, whereupon out comes the largest 4/5 cell NiCd pack for the ignition.

Regarding checking your LiFe packs without taking off the wings, you can extend the balance lead with a custom made lead where one end would have standard 2S JST female connector to mate with the pack's male balance connector, and the other end will need to be cut off and a standard Futaba/JR 3 wire male connector spliced. This connector then suitably fixed on to the model for easy access. When required, pull out the extension and plug it in to your checker pins.     

 

Edit

Just read (missed it first time around) that your ignition is 4.8-6v. 

My advice would be to change the ignition to later version and switch to LiFe packs as soon as possible. I have had regulators fail. Later version ignition with LiFe has less components to fail        

Edited September 21, 2023 by Manish Chandrayan

[Martin Harris - Moderator]

I prefer the simple method of using a suitably rated silicon diode which drops 0.6 - 0.7V volts with minimal failure potential.  
 

It’s a fallacy that 2S LiFe batteries maintain 6.6 volts throughout their discharge curve - there is a small but steady and measurable decline throughout the discharge - the more rapid voltage decline starts at around 6.3V under low discharge rates but would still allow plenty of time to land.  The problem is how you measure this in flight - I find that my telemetry alarms under heavy servo use e.g. during flick rolls when set to detect a low battery but to be honest, I never get remotely close to using my battery capacity and put up with the “false” alarms. 

[Bruce Collinson]

5 hours ago, martin collins 1 said:

One of these should be here tomorrow to drop the voltage on the Life rx pack to 6v.  https://wheelspinmodels.co.uk/i/103493/

NB the plug and socket are not servo-type Futaba/JR.   I fell for that too.

BTC

[martin collins 1]

10 minutes ago, Bruce Collinson said:

NB the plug and socket are not servo-type Futaba/JR.

Break out the soldering iron, new ends required then.....