Hobbico Voltwatch w/6.0v battery issue?
 

I recently switched out 2 of my old 4.8 volt 1500mah receiver batteries with 2 new 6.0v 2000mah NiMH batteries. I have a hobbico voltwatch in each plane and it's giving me inconsistent readings. As soon as I turn the airplane on, most of the green "safe" lights light up. When I move a servo it get worse and the yellow "caution" light lights up. I switch the voltwatch over to 4.8v setting and it fine. I know that's not right I want a accurate reading for the 6.0v.

Each plane has the same receiver (AR6200), same batteries, and servos (DS821). The battery charge in the first battery was 6.23v, 1950mah and the second battery was 6.41v, 1965mah, so I know I have properly charged batteries. What seems to be the problem?

Has any used the Loganville Hobbies Spy Cell?

Thanks
Steve

RE: Hobbico Voltwatch w/6.0v battery issue?
 

Your Volt watch is fine, this is normal. When you move a servo it draws current from the batts and their voltage will temporarily drop into the yellow zone, then go back to green. Don't try to run 6.0V with the switch set to 4.8V, you might damage it.

RE: Hobbico Voltwatch w/6.0v battery issue?
 

how did you know the batteries were charged to 1950mah and 1965mah?

RE: Hobbico Voltwatch w/6.0v battery issue?
 

Scooty,

If this is normal for the 6.0v to flicker the other green lights, then it would be difficult to know when your battery is starting to get low. I guess I'll have to test it more this week to see if the yellow "caution" light get brighter, as well as the red "fail"light. I guess I thought the left green light would stay solid like my 4.8v setting did. Thanks for you response.

Jetmecho5,

I used a milliamp meter. I acutally disconnected my battery from the reciever to get a reading. I normally don't do this on a regular basis, but since I was having trouble with the voltwatch I was testing just about everything to figure out the problem. I do have to re-bind the receiver when I do this.

Thanks
Steve

RE: Hobbico Voltwatch w/6.0v battery issue?
 

The Voltwatch is giving you some valuable information. It is telling you that somewhere in your wiring between the battery and where the Voltwatch is plugged in, you are getting some IR losses. Could be to small a gage wire for the peak currents you are drawing, high contact resistance in the switch or batteries with a high internal impedance or a bad connection in either the plus or minus leads. The Voltwatch is really a pretty good indication of whether or not your electical system is adequate, almost as good as an oscilloscope. Those lights dance for a reason, momentary voltage drop at the point they are plugged into. If you are using one of the 2.4GHz systems, this voltage drop, even for just microseconds, can cause a reboot with temporary loss of control.

RE: Hobbico Voltwatch w/6.0v battery issue?
 

Do I need a larger on/off switch to handle the 6.0v? I currently have the standard spektrum one installed, do they make a larger heavy duty one?

Steve

RE: Hobbico Voltwatch w/6.0v battery issue?
 

If you really want to get fancy, put a 2000 or 3000 mFd electrolytic capacitor (16VDC rated)
across the battery terminals. They are polarized.
Plus of the battery goes to plus of the cap
Negative of the battery goes to neagtive of the cap...parallel wiring
That's what to big caps are for in amplifiers, provides a big current source for
bass notes. Same deal here.
A servo at rest draws little power until commanded or holding against flight loads.
Neutral to full stick movement request demands max current available and that's
what you see as LED's fickering down as voltage is traded for current.
Put that cap in and watch your flicker disappear.
The cap will charge to the voltage of the battery and act like a redundant battery but
one that has an internal resistance much lower than your battery thus it can dump all it's juice
to the RX/servo(s) much faster than the battery and smooth out those high current demand transients.

RE: Hobbico Voltwatch w/6.0v battery issue?
 

This is a good question; I can't say I've heard anything about upgrading the wiring in planes. I'm up to 1.20's and 25% planes but don't know about upgrading the wiring to handle the 6 volts.

RE: Hobbico Voltwatch w/6.0v battery issue?
 

It is not the volts, it is the amount of current that is drawn during peak demands. The advent of digital servos, more of them and more powerful servos have all upped the current demands . It is the IR drop in the wiring, not the votage of the battery that causes the problem.

RE: Hobbico Voltwatch w/6.0v battery issue?
 

If the IR is greater in smaller wire, and the digtial servos are getting more powerful, wouldn't the manufactures put on larger wire for those servos? (Wait that would cost more, answered my own question.) In any case, I went to my local hobby shop and he gave me a number to Great Planes to see if they had any answers. If this is nornal.... I may just take it off and and plug in my voltmeter and check the votlage every so often and charge them if the voltage get low.

I may take a look at Loganville Hobbies Spy Cell.

Steve

RE: Hobbico Voltwatch w/6.0v battery issue?
 

What's IR?

Also I know it's not necessarily the increase in voltage that causes a problem, but they say that digital servos will wipe out a 6v battery faster than a 4.8 volt, so doesn't that mean there is an increase in current?

I've got 6 digital servos on my planes and would love to know if there are some precautions I'm missing.

RE: Hobbico Voltwatch w/6.0v battery issue?
 

What is IR? IR is the voltage drop (current times resistance) in the circuit that the current is flowing in. The predominant one is the voltage drop between the battery and receiver (the resistance in the switch contacts and wire between the receiver and the battery). Say there is a tenth of an ohm and your have two servos that instantly demand 2 or 3 amperes surge (not unreasonable on digital servos) then you get at least a 0.6 volt drop in supply voltage as seen at the receiver power buss. Now let that resistance increase a bit by using to small a gage wire or getting some corrosion in the switch and the problems quickly get large enough to cause a malfunction due to voltage drop at the receiver. So, the problem is probably not the gage of the wire between the receiver or power box to the servo but the wire and switch between the battery and and the receiver and of course the internal impedance of the battery which adds to this resistance.

RE: Hobbico Voltwatch w/6.0v battery issue?
 

Hi!
Could be that one cell in one of the batteries are bad! Check the voltage on each cell (digital voltage meter) while you run the servos! Each cell should show 1,25V or more!!! If 1V or less, one cell is bad and the whole battery pack should be replaced!

The problem could also be you are charging your HiMH batteries with a fast charger!
All modern fast charging devices uses Delta peak charging and as all modern NiMH batteries are notorious to suddenly show voltage peaks (voltage spikes) during charging your charger notice this and stops charging! So if we want to charge our NiMH cells and be certain enough amps is coming in, we better use an old fashioned slow charger (Wall charger)...or use a more modern battery ...like A123.