Old nmh battery

[thehorse]

I have a 7.2v 900 mAh battery for a Skyfly and would like to upgrade it to something newer. It's a 6pack battery 30/50/50 mm. Looking forward to ideas

[xviper]

Basically, you need to consider the following:
1. The plane needs ~7.2V.
2. It needs ~900mah
3. The kind of connector the battery requires to hook up to the plane.
4. A suitable charger to deal with LiPo batteries.
The current state of RC plane battery tech is the LiPo (Lithium Polymer), so look at some of the offerings there. You can use a 2 cell, 7.4V LiPo. So as to not change the balance of the plane, you should pick a LiPo that is approximately the same weight as your old battery. Since LiPo tend to be more efficient, they weigh a little less and are physically smaller than a NiMH of the same output. This is good for you because a higher mah LiPo will give you a bit more flight time. Check here to see what might be suitable for your plane:

https://www.motionrc.com/collections/lipo-batteries?_=pf&pf_t_number_of_cells=2%20Cell%20(2S)%207.4V

If you can solder, you can easily change the connector on the plane or the battery to match each other. Weigh your old battery to see how best to approximate the weight.

[WintrSol]

There are also LiFe batteries (2S 7.2V) that are rated for flight power, like A123 types. A little larger and heavier than the equivalent rated LiPo, but still smaller than your NiMH, and may be a better match to the power system.

[DivenParker]

It is recommended to 8.4V 900mAh NiMH Battery. You also can choose 2s lipo battery with about 900mAh capacity.

[WintrSol]

Since lipo batteries have a higher density, you could even get one with a greater mAh capacity, and still be lighter than a 6 or 7 cell NiMH battery of 900mAh capacity. Flight time would be longer, without sacrificing handling.

Of course, going to a lithium-based battery would require a charger to match.

[thehorse]

I'd like to thank all of you for sending me many new exciting ideas. After a long absence from RC I'm back at it. Buying new charger, planes and many accessories. Thanks again.

[thehorse]

A question for you. I see 2 sets of wire plugs from the lipo battery. Why 2?

[xviper]

A question for you. I see 2 sets of wire plugs from the lipo battery. Why 2?

The twin wires are the power leads that plug into the plane and give it juice and also for charging - that's where the power goes in as well as come out. The multiple wires ending in a white connector is the balance plug. It's used when charging or if you wish to plug in a device like a voltage alarm when flying.

[WintrSol]

To expand on this, the cells can slowly drift apart in state of charge, so one can go flat before the other (not a good thing). Balancing is bring both back to the same state of charge; this can be done by the charger in balance mode (assuming it has one), or with a separate balancing tool. Also, some cheap chargers charge only through the balance connector.

Speaking of going flat - if you discharge a lipo too much, you can greatly shorten its life, even kill it. Unless you use a lipo-rated speed controller (ESC), you will need the external monitor, to sound the alarm when the battery is too low.

[thehorse]

After much research I have purchased a B6 new multi charger that does all batteries. I've also located a 7.4v 1000mah Lipo battery that should be a snug but good fit.
My new concern is the wiring. The Lipo battery wires in this range of power are just a tiny bit different. The Skyfly motor wires are 2mm + or maybe 18 guage. Lipo is 2mm minus
Is it a problem having a very slight difference in the matching of new battery to the old motor?

[xviper]

After much research I have purchased a B6 new multi charger that does all batteries. I've also located a 7.4v 1000mah Lipo battery that should be a snug but good fit.
My new concern is the wiring. The Lipo battery wires in this range of power are just a tiny bit different. The Skyfly motor wires are 2mm + or maybe 18 guage. Lipo is 2mm minus
Is it a problem having a very slight difference in the matching of new battery to the old motor?

You have the oddity of running an older "brushed" motor. The Hobbico receiver appears to also be its own speed controller (and voltage regulator), so current goes through that before going to the motor. I think you'll be OK. Just check the "hotness" of the wires after a routine flight. The battery connector could be a little warm - that's OK. The motor wires could also be a little warm. However, if they are hot to touch, then you'll need to keep that in mind and not fly it at high throttle for extended periods of time. But since the battery wires seem to be thinner, those may get warmer. Again, "warm" is OK. Just remember that your battery voltages (stock vs chosen LiPo) is still similar regardless of whether it comes from a LiPo or NiMH battery. You've also picked a battery that is very close in mah, so you have some compatibility in terms of voltage and amps.

[thehorse]

Thanks xviper2, I'm also looking at connectors. I like JST because they are easy to install. I bought XT30 but they are very small and the fit is extremely tight. I've ordered XT60 I'd enjoy feedback in this area. Thanks in advance.

Best regards,

Ed

[xviper]

If space is a limitation, I'd say that JST is the handiest to tuck into small spaces. XT30 are also small, but because of their shape, not as easy to tuck into narrow crevices. XT60 is just a bigger XT30. XT60 is more akin to EC3, which is quite common for 3 cell LiPos over 2200 mah. HobbyKing seem to love XT60's. Planes from Horizon Hobby tend to like the EC3, EC5 and Deans.

[thehorse]

Thanks xviper2, I'll keep you posted as for my changes.

[thehorse]

One more question. Most all small Lipo batteries are sent with the male connector. Should I change to female connector and install male connector for motor and esc?

[xviper]

Once you progress to brushless motors and ESCs, the connection at the ESC are usually "male" (same as the charge lead from your charger). Therefore, the leads on the battery is "female". The exception to this are some of the HXT connectors where on each side, there is one male and one female. Some HXT's are also the same as more popular connectors (male on the ESC and female on the battery). HXT's are not that popular anymore. Take a look at the different types of batteries that MotionRC sells and you'll see what I mean. Each type of connector is designed to handle a certain range of voltages and amps.

https://www.motionrc.com/collections/lipo-batteries?_=pf&page=1

[thehorse]

I understand however my old Skyfly came with mini Tamiya male on the NiMH battery and female to the esc and motor. Instead of driving myself crazy would it be OK to just install a new Tamiya male connector on the new Lipo battery? I realize Tamiya are old school. Do you think this will work?

[xviper]

I understand however my old Skyfly came with mini Tamiya male on the NiMH battery and female to the esc and motor. Instead of driving myself crazy would it be OK to just install a new Tamiya male connector on the new Lipo battery? I realize Tamiya are old school. Do you think this will work?

Of course, it will work. Just be careful of the polarity. It's not likely that you will encounter another plane with a Tamiya connector, so go ahead and do the male on the battery. Later on if you want to use that same battery on another plane that has a more conventional connector, you can get an adapter like this and modify to suit:

http://www.ebay.ca/itm/TAMIYA-Connector-to-Deans-T-Style-Plug-Cable-for-RC-Speed-Controller-ESC-Battery-/251872285207?hash=item3aa4c21217:g:6ekAAOSwpDdU~Usn

Even better would be to make an adapter now or find one to buy that will connect from your plane to the battery. That way, you can use the battery as is for future planes that have more conventional ESC connectors.

[thehorse]

Thank you so much for all your help and valuable information. I bought this old plane in 2006 and it's still basically new in the box. I've modified the adjusters on the rudder and horizontal stablizer. It's illegal to fly unmanned rc aircraft here in Japan. Very strict laws we're passed in 2014. Basically I'm fine tuning the plane getting it ready to take to California later this year and fly it there. Your advice is a real pleasure to study. Thanks again.

[xviper]

Thank you so much for all your help and valuable information. I bought this old plane in 2006 and it's still basically new in the box. I've modified the adjusters on the rudder and horizontal stablizer. It's illegal to fly unmanned rc aircraft here in Japan. Very strict laws we're passed in 2014. Basically I'm fine tuning the plane getting it ready to take to California later this year and fly it there. Your advice is a real pleasure to study. Thanks again.

Better check out the regulations in the USA, too. This past year, both the FAA (USA) and Transport Canada have come out with fairly strict regulations regarding RC model aircraft.