Dualbatts

[John Mcnamara]

I have not used anything with Ni written one it for years now. NiMh are OK for TV remotes. After that I don't give them house room. I started using A123 batteries when they first appeared and I have used them ever since without a single failure. Recently I have started using the Jeti Power Ion Batteries.
A123 - (LiFe04) Very safe, can be charged inside the model. Almost no self discharge. 6.6VDC from a a2 cell battery. These do need regualr balancing. I always balance charge them.
Power Ion (LiIon) Very safe, can be charged inside the model. Almost no self discharge. 7.2 VDC from a 2 cell battery. Jeti say that provided they are charged correctly according to their instruction, no balancing is required. I am only into my second season with these so too early to tell, but so far so good.
LiPo Fundementally unsafe. These have oxygen embedded in the anode. They are easily damaged in a crash. If they start to burn the CANNOT be extinguished. Never charge them in the model, only in a fire safe container. Must be balanced regularly.
As the chairman of a jet club for the last 10 years, I have seen a few models crash and burn. But the worst fires were from LiPo's in the nose, that we could not stop burning. I fill a smoking hole in the ground with the contents of a 25KG foam extinguisher, and still it burned!
My advice do not use them except for motor power in an electric model. There is little choice in that case.
The number one cause of batteries fires remains incorrect charging protocol. Be careful out there guys.
John

[Ian Davis]

Like John I've used A123 batteries for many years.

While I might regret saying it, I'm so confident in their behaviour I no longer worry about dual batteries and backers - things of the past.

My source from day one with A123's is Puffin Models of Bristol. Good prices and service.

Ian

[John Mcnamara]

Hi Ian,
That is a fair point. A123's have been totally reliable. They do eventually loose their capacity but even this seems to be a gentle affair. I just replaced some in one glider last year, as they were starting to fade after about 8 years. They are now residing in a jet, running the lights. VFM.
However, In my gliders I always have to put lead in the nose, and you cannot get electricity out of lead sheet (well, you can, but you know what I mean). So I prefer to make up some weight with a second battery and SWITCH.! I have had these fail too.
For the extra bit of cost it makes sense to me, but after loosing a few gliders, I tend to be belt and braces.
John

[jimbo]

Having been on the receiving end of a lipo fire in the past I try to avoid these if I can!
I've used the li ion batts, I have a dual set up in my stingray. I've yet to try the lifepo4 a123 batts. Do look good however similar cost as the li ion at 27 quid a set they aren't cheap. An eneloop costs about 10 to 12, gives a redundant set up for 25 quid plus switch. Personally I'd always rather a dual set up over a single if I have the room.
Colin i've had 3 sets if 5 cell over lander Cs fail over the years, won't be buying them again.

[Chris Veitch]

John

I have swapped to li-Ion on a few gliders recently having got fed up with the loss of capacity of the old batteries when stored.

I did look at A123 built was not sure of the reliability of the discharge curve. How do you ensure you know how much capacity is remaining in the batteries ?
Regards
Chris

[John Mcnamara]

Another good point. It is quite tricky. You can do a gentle discharge and watch for the voltage to drop, BUT, the good thing about A123's is an extremely flat discharge curve. At the end of this flat phase, the curve drops like a stone. This makes it tricky for any discharge system to spot that the battery is nearly flat, so when I do it I am watching it every few minutes. As soon as the votage drops below about 6.3 volts they can be considered as flat.
This is just a rule of thumb. I practice I do this very rarely now (because it is a PIA to do). Instead hi have a simple stratergy based on the aformented failure to extract current from lead. So I fit the biggest batteries that I can, and always use two. Invariably this leads to a surfeit of capacity in my models, despite often (usually, well always) using digital servos.
What you can be sure of is how much capacity you charge into the batteries. Unlike anything Nixx, there is an almost direct relationship between capacity shown during charge and actual capacity.
Couple this with the modern tarnsmitter providing real time telemtry warning of the battery state, and having a second one anyway, and you are very safe. So far no incidents on my part.
BR

John

[Phill Tadman]

Hi John,

Do you regulate your Jeti Ion batteries or connect them directly to the Rx or Central Box?

Thanks,

Phill

[John Mcnamara]

Hi Phill
It entirely depends on the installation, and in particvular the type of servos being used. In the installations so far I have used CB 400 in a couple of models, and a mix of HV and SV servos. In another I have used HV servos throughout and No CB


John

[Chris Veitch]

Hi John

Just wondering how your Life's perform during a days flying, what voltage do that start and finish with ?

I have just started using the Lions in the last few weeks. On Sat when the DG was flying a lot of the day at Eden I stated at 8.1v and ended up at 7.6v with 2 packs of 2s5900s so reasonably happy with that.

Thanks

Chris

[John Mcnamara]

Hi Chris,
They always start the day at 6.6v, but I always charge overnight so they settle to this voltage by morning. I always find that one battery does slightly more work than the other, the one that has the lowest internal resistance is always lower.
So I typically see 6.6v from one and 6.5v from the other, but only after lots of flying. Back from the Eden Vale aerotow, with about 1 hour overall flying time on my Orlik, one was showing a solid 6.6v, and the other flickering between 6.5 & 6.6v. However, that battery will typically stay at that voltage all day. Vintage gliders do not take much current in a typical thermal flight, so I put 268mA into one and 198mA in the other, total 466mA. I have 5200mAh capacity in the Orlick, so in theory 11 hours of flying time between charges! I am not planning to put that theoretical limit to the test anytime soon.
John