I'm going to buy a Hobbico Expanded Scale Voltmeter MKII from Tower Hobbies. I have a Nexstar with the Futaba radio system. Are these the right leads for that particular radio set up? Can I test both the reciever and transmitter batteries with those? Would this be a good set up? Thanks.

Those would be the ones. You can check the receiver batteries with the receiver cord, but you won't be able to check the transmitter. Futaba installs a blocking diode in the charge circuit and this won't let you discharge the transmitter battery for cycling or let you use a meter. You can also use the cords to charge the transmitter and receiver batteries at the field with a fast field charger.

Jesse

If your transmitter has the older style battery connector it will be just like the one on your receiver. If that's the case you could use the voltmeter, but the battery indicator on the transmitter is pretty good, and you don't have to worry about a "servo load" on the transmitter pack, so I wouldn't use it. (The voltmeter puts a false "load" on the receiver pack to determine if the pack has sufficient capacity, not the case with the Tx.)
Dennis-

I just make pig-tails as needed for my voltmeter. The leads shown will work, but there is the diode issue. If you don't mind voiding your warranty, then you can bypass the diode. I did it. The reason why is that my charger is a peak detection charger and wouldn't work with the diode. That meant I was constantly pulling the battery out which put a lot of strain on the battery lead which I was afraid would lead to the demise of an airplane.

Bypassing the diode allows me to leave the battery in and use any charger I want.

- Paul

Yes, you will not be able to read the transmitter pack but your transmitter has a gauge.

dkf1979,
That meter is only good for testing batteries. Why not by a VOM that will test DC, AC and resistance. I got mine from Radio Shack for $19.95. It is small, digital, bright yellow, and uses the dual banana connectors.
With this you can make up all of the different leads you need. In order to put a load on my batteries I put two 47 ohm, 1 watt, resistors on a dual banana plug, net is 23 ohms 2 watts. When I want to load the battery I just plug it on top of the plug with the leads.
This is much more versatile and I do use it for a lot of other things, even in this hobby.
KW_Counter

I have a VOM too but I bought one these because it's small fits nicely in my box, plus it puts simultated load and give more acurate reading. I do have a question though about cycling TX batteries. Bypassing the diode will kill the warranty but will it have adverse affects on the TX? Why do companies install them in the first place?

Personally I use a Fluke DVM and I load it like KW Counter does. It is more accurate than the Expanded scale Hobbico meter.

The reason manfactures put in a blocking diode is for protection from reverse charging your transmitter. I.E. trying to charge the battery with the charger negative lead to the positive lead of the charger. With the blocking diode nothing happens, without it the smoke comes out. Another method is to fuse the positive jack and then put a diode wired as a shunt to ground. In case of reverse polarity the fuse blows. The newer radios use a resettable solid state fuse.

Bypassing the diode has no ill effects other than cancelling the protection it afforded in the first place.

John

A better method the manufacturers could use is inserting a bridge rectifier between the charging jack and the circuitry. This would always direct the proper polarity in the right direction, irregardless of how you hook up the charger. I still don't think that you would be able to peak charge the battery due to the voltage drop across the diode.

How hard is it for you to remove the battery to cycle it outside the case?
Why not just leave it on until you reach between 1.0 and 1.2 volts/cell?
That is what I do. Make sure you don't live near a field where you could cause interference. Or, do it at the field while your pin is up. A good day of flying should get you pretty close to this.

KW_Counter

It's not hard. The problem is that with the Futaba radios that allow you to remove the battery through a hatch, the plug is inserted in a way that causes a lot of strain on it during removal. That would be a really bad plug to develop a short. The more times the battery is taken in and out, the greater the chances of damaging it.

That's why I bypassed the diode - not for convenience, but for safety while still being able to use a decent charger (Sirius).

You can also splice a servo-type connector into the battery lead, between the radio and the battery. That will make it easier to plug and unplug the pack, but it's also one more thing that can fail if the splice connections are poor. On my radio, I just have the diode bypassed.

Jesse