[wymbly1971]

Originally Posted by Max

I still dont understand what all the hype is about Lipo packs for transmitter.

Capacity is Capacity

I run anywhere bettween 2000 mah Eneloop NiMh to 2700 NMh

Some guys want to use a 2200 Lipo.

Well, guess what? My NiMh2700 will outlast any 2200 Lipo, and with less chance of messing my my transmitter to boot. No worries abut over-voltage on the lipo, or diodes pooching out on me. So why the hype? I will continue to stay with NiMh for now

The thread starter asked about converting to LiPo. I have some experience with this, so I thought I could share my experience.

When I switched to LiPo, I was becoming frustrated with the self discharge rate of NiMh cells. Eneloops were pretty exotic and pricey at the time. The NiMh were generally lower capacity and more expensive than a comparable LiPo and the tabbed versions more difficult to find.

Then there is the pack preparation.

8 individual AA's need to be soldered together. That is easy enough with a spot welder but I thought it might be risky with a regular old soldering iron. Then the cells need to be physically bound together by some means; big heat shrink, hot glue, black tape? Easy to do for a flat-8, but quite a bit more difficult for a 2x4.

A lipo (with diodes) needs to have one plug cut off, and 4 solder joints made with pretty much anything that will melt the solder, two pieces of standard 1/8" heat shrink and you're done.

Cheaper, easier, considerably higher capacity (than the original NiCd) and virtually zero self discharge is what helped me make my choice.

If I had to do it again, I would consider Eneloops too. Thanks for the suggestion

[Max]

Originally Posted by wymbly1971

The thread starter asked about converting to LiPo. I have some experience with this, so I thought I could share my experience.

When I switched to LiPo, I was becoming frustrated with the self discharge rate of NiMh cells. Eneloops were pretty exotic and pricey at the time. The NiMh were generally lower capacity and more expensive than a comparable LiPo and the tabbed versions more difficult to find.

Then there is the pack preparation.

8 individual AA's need to be soldered together. That is easy enough with a spot welder but I thought it might be risky with a regular old soldering iron. Then the cells need to be physically bound together by some means; big heat shrink, hot glue, black tape? Easy to do for a flat-8, but quite a bit more difficult for a 2x4.

A lipo (with diodes) needs to have one plug cut off, and 4 solder joints made with pretty much anything that will melt the solder, two pieces of standard 1/8" heat shrink and you're done.

Cheaper, easier, considerably higher capacity (than the original NiCd) and virtually zero self discharge is what helped me make my choice.

If I had to do it again, I would consider Eneloops too. Thanks for the suggestion

I know. I already answered his question in post #3.

Originally Posted by Max

Umm, I dont think that is good advice, considering JohnM'r radio is 7.2V

A DX7 runs on 9.8V nominal power (8 cell Nidcad or Nimh)

The 12FGA runs on a 7.2V nominal power (6 cell Nidcad or Nimh)

Using a 3 cell lipo that you are using in your DX 7 will FRY the 12FGA. I sure as heck would not put any 3 cell into the 12FGA.

Lets approach this more scientifically;

1) a 6 cell 7.2V Nicad/Nimh can come in anywhere from 8.4V to 6.6 (1.4V @ full charge per cell down to 1.1V @ lowest safe discharge per cell)

2) a 2 CELL lipo comes on from 8.4 to 6.6 under normal operating range. (4.2V @ full charge per cell down to 3.3V @ lowest safe discharge per cell)

If it were me, I would have not hesitation using a 2 cell lipo on the 12FGA

Yes, the OP had asked about 2S lipo for his application and for the record, I did say he should be good to go with a 2S lipo. I was responding to the thread hijackers that dont read the thread and start posting willy-nilly about thier 3S lipos and and how great it is for them and blah blah blah.... not reading the OP's 2S question...

[Spitball]

At least two suppliers now have ready-made Eneloop NiMH Tx packs, all assembled with welded cells and thin clear shrink. They were prepared to make up a special 6-cell pack for my Airtronics SD-5G but I found you can't easily remove the built in connectors so I still use loose cells and clean the contacts from time to time. And they will not void your warranty!
P.S. I agree Max - this is so often is the case, I once had a lecturer who was fond of saying "I do not wish to know that!"

[spog]

Eneloops won't do this

[bobreib]

I have a 12 FG and replaced the original battery with a 2000mAh NIMH after market battery. Although an improvement, it is still not that great. I recently came across these and ordered a pair. I'll believe the rated capacity after I can test it, but it sure looks promising.

[Flypaper]

Another place you might try is laptop power supply. They're li-ion measuring 18mm dia and 650ma long. I used them for a plane but didn't have enough poop to do much more than fast taxi. These are low discharge batts i've since found on the Emoli website at 5 amp discharge rate which would be fine for a trans. Problem is, I don't think they'll fit in your trans. being too long.

[bobreib]

I ran a test on 3 batteries .. Current Draw set at 400 mAh, Tetminal voltage 6.8 ( these are typical for the 12FG )
The original 1700 mAh battery lasted 3 hours 15 minutes
A 2000 mAh after market battery lasted 4 hours 8 minutes
The 4200 mAh Li ion batteries lasted 4 hours 48 minutes.

The Li ion battery still had lots of capacity, but the terminal voltage was below the 6.8 volt alarm setting of the 12FG.

As you can see from the photo, 2 of the Li ion batteries fit OK, but they are too big in diameter to fit 4 of them in the battery compartment.

[hifly2104]

Originally Posted by tskca

Anyone try one of those inexpensive Tx batteries listed on the HK website?? I am in the market too.

Seems like the only problems encountered so far by buyers have been their size and not checking the polarity of the battery leads before plugging it in. Then they do sell genuine A123 cells to make your own battery??

Ken

Until now I thought all radios took a standard size TX battery. It appears I was wrong there is no such thing as a standard size. I have a Futaba 9C and a JR XP7202 the 2650mAh 3s battery that HK sell will fit both of these radios and it is fitted with the plugs for either
http://www.hobbyking.com/hobbyking/s...poly_Pack.html
I need to replace the one in my radio now as it is two years old mind you it would probably been good for another two years if I hadn't left the radio on. That is the one and only draw back I know of using this lipo battery they go dead they are garbage

[Flypaper]

I killed my lipo twice in the DX7. I charged under NIMH until it got over 3 volts per cell. then go to lipo in the charger. Worked fine afterwards, both times. Sold the trans last yr and the guy is still using it with the lipo. These ones for trans. are low discharge batts and able to handle it. It was from HK. I bought a lipo for the DX8 from HK and it's working fine.

[hifly2104]

Originally Posted by Flypaper

I killed my lipo twice in the DX7. I charged under NIMH until it got over 3 volts per cell. then go to lipo in the charger. Worked fine afterwards, both times. Sold the trans last yr and the guy is still using it with the lipo. These ones for trans. are low discharge batts and able to handle it. It was from HK. I bought a lipo for the DX8 from HK and it's working fine.

Will give that a try It appears only one cell isn't charging as lipo