Need your help - NiMH battery packs

[Wayne]

Hey all, I have a question for you. If you are flying gliders or IC engines, are you currently using NiMH battery packs?

It is time to restock these, but demand for these packs is dropping but our minimum order is rather high. They have a short shelf life so we really can only stock the configurations that will sell in a given time. I think demand has dropped enough to the point it makes little sense for us to attempt to stock these anymore.

What are your thoughts on this?

 

[Konrad]

I can't argue against the sales data.

I like the 1300 mAh 5 cell 6V battery. I like the mass. I also like the discharge curve of NiMh better than Lipo for the radio. I've saved a few ship as I notice the slower responce of the dying NiMh battery. Had I has a lipo I don't think i'd have made in back to land.

That having been said I like the high voltage 8.4v of a 2 cell lipo.

 

[thenated0g]

I use them in all my gliders but it's mainly the price I like and the simplicity.

 

[gp49]

Use them in all my gliders (too many). Mostly 4 cell, 4.8 volt. Your pricing is better then most other places.. How hard would it be for you to make custom cells in-house based on a couple standard sizes?

 

[thenated0g]

@Wayne is this a problem with the single cells as well or just the premade packs?

 

[Nigel]

Premade packs mostly. Some sizes sell, others don't. Individual cells give us more flexibility to create any size pack, as well as an easier to maintain stock. It's unfortunate, but if the batteries sit for a long enough time, we have to pull them from stock and effectively eat the loss.

 

[Wayne]

Well, good news is our battery supplier is willing to do a lower quantity, so we will continue to offer the pre-made packs in most sizes. And yes some individual cells also.

The issue with making cells here is we pretty much have to charge a base price of $10 or $15 just for the labor and materials to build a pack. We will start offering this service in the future, but we simply do not have the spare labor to offer any additional services at this time.

Thanks all for the responses.

 

[Tahoed]

If you take a look around, many of the servo companies are moving to high voltage or wide voltage servo's. Life's or 18650 and 14500 are the future of our receiver packs.

 

[Haoyang Wang]

I am using lithium packs in my new gliders. Single-cell Lipo for DLG. 2-cell Lii-ion for larger gliders.

From time to time, I still need to replace the NiMH packs in my older gliders. Unfortunately, each glider has its own size of batteries:
. square pack for Weasel
. flat, short pack for Ahi
. flat AAA pack for NCFM Halfpipe
. flat AA pack for Windrider BeEvolution combat wing
...

This is stupid, but I don't see an easy path toward standardization.

 

[Tahoed]

There is no standardization. I've got a 2S lipo with a BEC in my Ahi. All the fuselages are different and there are a number of options to the builder as far as space, weight, size and your servo selection as far as voltage. It's a crazy hobby...? I just deal with it on an individual basis with every airframe. It's what makes this fun.

 

[Wayne]

Yeah, the Dream Flight planes are built around some rather odd NiMH packs. I'm not sure why he builds around these odd sizes, but he always has. I suspect to make a little money on the battery sales. Most others were based on AA or AAA packs.

 

[Johnnashville]

How about stocking some 2s LiFe receiver packs?
the 500mah to 1000mah size

 

[Jim-e]

I have some older opto speed controls and also going to resume flying mostly smaller i/c. Been using some 250mah nicads that I assembled (solder tabs has been my choice since the 1980's) but down to two packs. So I ordered some solder tabs cells nicads and life since Aloft was out of stock, from an online supplier in Richmond CA. Some of the life cells were six + years old but turned out okay. The 2017 AA nicads had okay capacity using a MAHA 9000 charger on break in cycle, but the 2016 cells took several tries to get them within 50 mah of 700mah, and one cell is way weaker so instead of two 8 cell tx packs, I have one pack in limbo because the supplier has been ignoring me. So the long winded point I can make is making packs can be a losing proposition because of difficulty matching cells, because batteries begin to die once they are made. The life cells seem more durable than nimh and nicad cells must be old stock and that is a problem.

 

[Wayne]

I can look into the LiFe cells, but I think the low C Lipo packs from Dualsky we offer are actually a better option for receivers. They are really wonderful packs in a range of useful sizes and no need to change the charge mode in your charger.

Nicads actually have a very long life span, but poor capacity and self drain very quick. NiMH can have a much slower self drain, but lack of use kills these cells. Lucky to get a year out of them if they are just stored. You do not want to buy old NiMH cells. Sadly lots of shops are sitting on old cells and are happy to sell them. You really need to make sure you are getting fresh stock. We buy ours factory direct to avoid the old cell issue. If you can source really high grade NiMH cells, I think they can have a longer shelf life, but not by a ton.

Lithium Cells - I honestly do not know what the shelf life is for a properly stored cell. Internet wisdom is 2 to 3 years, but with modern cells I suspect that it may be much longer. With this said, we are careful not to over stock so we can always supply fresh cells to our customers. Again we buy manufacturer direct to assure fresh production. With many electric cars we can see the cells far exceeding these numbers with good results. I think Tesla offers a 7 year warranty on the packs?? I have seen many people harvest new or slightly used cells that are over 5 years old from industrial backups with nearly full capacity still available.

Anyone else interested in LiFE packs?

 

[doclov]

Hi Wayne:
I would be interested in 2s LiFE packs.

 

[Wayne]

Will see what I can find.

Had a fun little wire melt down this weekend. For the life of me I am still not sure what happened, but it was the first time I am powering a brand new model with a 2S lipo. Plugged in my final channel and smoke and melting wires. I had a short servo extension between the battery and the receiver, and that melted down like a fuse link. Checked it all out and powered with a NiMH with no issues. No idea what caused this. Must have been a short in the final plug, but the heck if I could find any signs, and as mentioned it all is working now. Same servos and even the same receiver. I thought it all might be damaged. Just a little smudge of black where I plugged in the last flap servo.

 

[sande005]

Another vote for LiFe. I've gone to them for all my fuel flying. LiPo's being 3.7 or 7.4v seem to be either too little or too much for the nominal 4.8-6v equipement I use. But the LiFe's, while pushing the voltage a bit, have worked very well. And after several years of using them, seem to be stable enough that (rightly or not) I am able to just leave them in the plane, and charge there as was done with Nicads/NiMh. I wouldn't chance that with LiPo.

 

[Target]

I love the Life packs. The 850 Hyperion fits great in most slopers. And the 1700 2S2P is a drop in replacement size wise for a 4 x AA square pack.

 

[sande005]

Well, it is a simple volts/amps/usage thing, but I've started to track mah usage in my basic 4 ch. glow trainer used for instruction, and the subject came up about LiFe for the starter and the electric fuel pump.
After 22 logged flights, it is shaping up that a 700 mah 2S LiFe pack can get me about 15 15 min. flights.
Using a 700 mah pack on my fuel pump gives me over 4 gallons of pumping before a recharge.
Having a big "Dynatron" starter, a 4500 5S LiFe pack will get me well over 500 starts of that little .40 engine (!)

Obviously, similar LiPo's would do the same, but LiFe's are better in sizing the voltage to what the equipment is rated for. Looks like I got too excited, and oversized by a significant margin. Except for the plane, it is nice to only have to charge once a season!

 

[thenated0g]

Just had my first nimh pack die.. buried inside of one of my vacuum bagged wings.. sigh. Looking at life now myself for future projects. Mainly as i want to keep it simple and using life over lipo means i don't need any voltage adjustment inside as most of my slopers cant take 2s lipo or higher. Also seems like a lot of life batteries have a manufacture charge rating at 5c which is pretty awesome for using out at the field.