Lipo Battery

[petermick]

I recently came across a Green Box Nobler that was built back in the 60s.  The person I got it from was trying to convert it to electric. I decided to go ahead and complete the project. Because the plane weighed about the same as my Vector 40 I thought I could use the same setup which was an E Flite 15 motor a 50 amp Castle ESC and a 2600 mah 4s battery with a runtime of 5 1/2 minutes. When the flight ended I normally had 20% battery capacity left. This setup worked great for a number of years until the Vector started to show it's age. I set the Nobler up with the same motor with a RC Electric Parts 60 amp esc and the same 2600 battery. I have test flown the Nobler with the rpm set at 9800 and flight time set at 2 1/2 minutes. The plane flies great.  For whatever reason the battery capacity at the end of these short flights is below 50% which is unacceptable. I am wondering if a 3200 mah battery would solve this issue. My problem is I am limited to a battery with a length of no more than 4 3/4 inches. It appears that 3200 or 3300 batteries are usually 5 1/4 inches long. Does anyone know of a larger capacity battery that meets my size requirement of 4 3/4 inches?
Thanks
Peter Mick

[Dennis Adamisin]

Brodak carries the 4S x 3500 with a similar form factor as the 2600's you are using.  I know they fit the Vector ARF, so should fit the Nobler.  They are probably heavier than the 2600's tho...

https://brodak.com/electric-accessories-1/battery-s/lipo-battery-4s-x-3500-for-ef-1-large-stunters.html

[Ken Culbertson]

Boy this is the week for great flying planes with grumpy batteries.  The ThunderPower 4s 2800 is shorter than the one you are using now by 18mm.  It also has the advantage in that the 4s, 5s and 6s are the same length and width.  They are just deeper.  I doubt that the extra 200mah is going to be enough but if your ESC and motor will take a 5s you could get the head room that way.  TP are not cheap but they are light and they go on sale frequently at 40-50% off.  The next size up (3500) is too long by 15mm.  FYI, I flew my ARF Nobler on the TP 4s 2800 with plenty to spare.

The spin-up and takeoff uses a lot of battery.  I was disheartened when my latest one drew my test battery down to 15% (Li-Ion) after three 1 minute trim flights.  The same battery fully charged made it to the end of the pattern.  So, you probably have 5 minutes run time but that is really not enough.  Maybe the extra 200mah would be enough though. 

Good luck - Ken

[Mike Palko]

Peter,

A 2600mah or 2800mah 4S pack should easily get a Nobler through the pattern or fly for 5 1/2 minutes. It sounds like you are using old lipos which might be the issue. They are aging out. If you have a charger that measures internal resistance you can start there. High cell resistance is an indicator that the lipo is in poor health and needs to be replaced.

That’s my guess if the power system was a direct swap from the Vector to the Nobler.

Mike

[Curare]

Using percentages to calculate how much capacity is left in the battery isn't an ideal choice. It's good for a very, very rough guide at the field but I wouldn't hang my hat on it.

How much are you putting back into the battery to recharge it? That's probably the biggest indicator. If you're flying for 2 1/2 minutes and chewing up 2000mah, you have a big problem. Have you put a wattmeter in line to see what kind of amperage you're pulling?

I will also say that lipo's inherently lose capacity as they age, so you'll notice you'll see your percentage at the end of the flight dwindle over time. I generally aim to have 25% left in the pack, and once it gets down to 20%, I pass them off to my RC buddies.

One final thing, there are a bunch of guys on RCGroups who have been testing battery packs of all brands and have tabulated the data, it's very informative. Thunderpower are some of the worst bang-for-buck batteries on the market.

Here's a link for the curious.

https://www.rcgroups.com/forums/showthread.php?1767093-Battery-Load-Test-Comparisons

The whole thread is over 1000 pages long, so page one give you the cliff's notes.

[Dennis Toth]

There is a lot of data but I didn't see a summary/conclusion page?

Best,   DennisT

[Ken Culbertson]

 Most of the batteries they are testing are in the 5000mah range.  I couldn't find any in the 25c range that compared to what we use.  They sure do have a dislike for Thunder Power.

Ken

[Curare]

Most of the batteries they are testing are in the 5000mah range.  I couldn't find any in the 25c range that compared to what we use.  They sure do have a dislike for Thunder Power.

Ken

That they do, but it's not without corroborating data.

I think the reasoning behind using only 5000mah packs is to be able to compare apples to apples. With that in mind, and a gracious dash of salt, one can figure out what packs might suitable to their requirements.

[Dwayne Donnelly]

I find them to be a crap shoot, I have Zippy's that are 8 years old and still going, I've bought Venom's that only lasted just over a year (maybe why they are out of business now) Take care of them don't charge on to high a setting and don't run them down past 20% left and most brands will last way past the cost per flight compared to glow.

[Fred Cronenwett]

Lipo battery sizing is easy to follow

The voltage of a 3S is the same for all 3S Lipo's
The connector might be different
The balance connector might be different
The size is dependent on the Mah capacity of the battery

Hobby King will tell you how long, wide and thick the batteries are

Bottom line the higher the Mah the larger the Mah capacity is, but you want to pay attention to all three dimensions to see what fits your model.