Flying with different batteries
 

Hi ,

Would like to hear your experiences about this topic.

Actually, i am flying P-programs with typhical 2+2 ship`s ( currently, integral`s).
My battery arsenal has become widely ranged by different brands, in different conditions. They all work fine, at least good enough to perform the P-schedules in normal conditions.

Personally i feel it challenging to keep a constant flying style using the different batteries, caused by the differences between them.

E.G : I can set up my throttle curve / power-management for one battery, and it will be wrong for the next one ...

... equal packs in same condition all the way would be fine, but ...

How do you guy`s deal with this?

Thanks in advance,
Kjell Olav

RE: Flying with different batteries
 

Kjell Olav,

I am in the same situation, having collected batteries through several years.

Although expensive, I think this is the only solution to the problem:
Through away all the old packs, including those you bought this year. (Seriously.)
Buy a sufficiently large number of sets of batteries at the beginning of the season and use them approx. equally much through the year. They will deteriorate a bit during the season, but should remain quite equal to eachother.
Repeat treatment annually.

Magne

RE: Flying with different batteries
 

Unfortunately  I do share the previous opinion as I too have come to the same conclusion. I will explain why and how:</p>

May 2008 I had decided definitively to go just electro and at the time, after a lot of analysis, decided to buy 6 x 2S and 6 x 3S 3200mAh Kokam H5 30-50C packs. At the time I believed that 1000$ of investment will pay off as the packs should last at least 3 years with adequate performance, therefore easily offsetting potential cost for glow fuel. With these packs I could have easily had any combination from 2 to 12S without any problem at any time. Even if the relative capacity was not big it was easily compensated by higher voltage as for eg. 12S 3200 roughly has the same energy potential as 10S 4000, and with very high (at the time) discharge rate. In practice those same packs were used on 6 different planes as 3S, 4S, 6S, 10S and 12S if necessary.</p>

May 2009 I bought my first Rhinos, 3S 2250 25C for mere 30$ (today 19$) and immediately figured out that they are holding power better than my precious Kokams [X(]! Then I tried also Flightmax, they are good but not as good as Rhinos. So far my Rhinos are still holding well, will see what will be in May next year. Also I am currently selling all my Kokams for 1/3 of the price I paid for them, and new still cost the same!!! That was really a "good" deal</p>

I just hope, wish, that the LiPo technology has made a huge step in 2009 and we all were just test pilots for various Kokam, Polyquest, TP, FP, Hyperion ... and that new batteries we all buy today will REALLY last longer, otherwise the old Henry Ford was right: "The best battery is a new battery, pardon, car"  ;).</p>

So far I did not like to bring my charger at the filed as I had sufficient number of packs. But I think this will have to change as I plan next season to be on 10S on multiple models and I will never again spend 1000$ on new batteries in one shot!</p>

This is my (sad) experience, would really love to hear from the others.</p>

RE: Flying with different batteries
 

Hi Kjell

The new Schulze L, XL, and XXL controllers have a feature referred to as voltcontrol in them. What this does is allow you to set the top end rpm a bit lower than what you would get from the batteries fresh from the charger. From that point on the ESC will always maintain that peak RPM regardless of input voltage.

For instance, lets say off the charger your peak RPM is usually 6500 rpm. So you set your ATV such that you have 6000 rpm, now the ESC recognizes this point at full open and as long as you have enough input voltage it resets itself to always provide 6000 rpm max.

Unfortunately the smallest ESC that this is offered on is the 32.115 which is a little large for F3A use, but with some small modifications can be made a little lighter. Maybe Schulze can be convinced to make an F3A sized version if there is enough interest :)

RE: Flying with different batteries
 

Great inputs guy`s !

... so far i had my favourite packs for competition , other for practice , stronger / lighter conditions etc , but it don`t seems right to me this way ... Personally, i prefer a constant powermanagement regardless of the flying conditions ... Better to deal with the flying condition`s as it is.

Schultze is defenetly into something here as Chad mentioned.
Lets hope we can get an ESC that fit our higly needed constant powermanagement for F3A, regardless of the batteries.. It would not only make things a lot easier performing our schedule`s, but allowing us to both do some experimental and keep our old- but still going batteries ...

lets convince schultze about this, and get things started :)


Kjell Olav

RE: Flying with different batteries
 

Hi.

I think that what Schulze is doing is very good, I actually requested this feature several years ago.
However, I do not think that it fully compensates for the problem here.

What it does, in my opinion, is to compensate for the voltage drop during the flight, to ensure that you have the same power at the end of the flight, as you had at the start.

What Kjell Olav is describing, (or at least what I have experienced) is more significant power variations.
I started to fly electric 2m pattern models in 2002, and have (deliberately) lost count on how many battery packs I have had. There is however one thing that has always been the case, and that is that the packs I bought this year are better than the packs I bought last year, which are better than the packs I bought two years ago etc. etc.
The differences are quite significant.
At the beginning of this season I had some packs from last year, and I bought a few new packs. (Flightmax 30C)
Testing new and one year old Zippy packs, on the same motor/regulator/propeller:
1 year "Old" packs: 33.5V/75.2A/2518W/6060rpm
New packs: 37.4V/88A/3300W/6600 rpm

This is more than 30% increase in power, on the same set-up. I also have two year old battery sets (Thunder Power Prolite) that are still in use, and these have even less power.

Therefore, to take advantage of the Schulze system, I would need to set the power level (rpm limiter) VERY low, to match the oldest packs, in order to achieve constant performance irrespective of which pack I am using. I don't want to do that. I want to use the best battery packs I have for competitions, which leads to the power variation problem when practicing with older packs.
If my oldest packs were still "plenty powerful enough" for competition, then it maybe would be different.

Magne

RE: Flying with different batteries
 

Hi Magne,

Yes you are quite right, very old packs will always be down on power. I don't think there is any solution to that except to get new ones :) The Schulze feature is only intended to compensate for small differences between relatively similar batteries.

RE: Flying with different batteries
 

AND.....

It will even out relatively minor power changes attributable to variations in ambient temperature differences (morning, mid-day, evening).

Regards,

Dave

RE: Flying with different batteries
 

... what about an ESC that have the ability to program a power-curve from end point to end point, regardless of the battery condition ?

E.G: output voltage- or may even output-watt controlled , - throug the complete throttle curve ? ( with certain max amp safety restrictions). A weak pack that do not follow the curve could be stored in the ESC-memory and be put out of business...

... I may be way of here ... I do not even know if this is technical possible to make ...


Kjell Olav

RE: Flying with different batteries
 

And what about LiFePO4? Can anyone tell how a new pack compares to an old one? Prices have gone down and are absolutely comparable to Rhino/Zippy packs , while the weight is unfortunately still the same.</p>

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=10311</p>

There would be a 600g penalty from 12S 4500  LiFe compared to 10S 4900 Rhino.</p>