NEQ6 Pro running on a deep cycle battery !

[Pscammp]

Hello all,

    I am about to embark on building my own power supply box for my stuff using a 75Ah deep cycle battery. I have a question to ask if you don't mind ref my mount (NEQ6 Pro)......

 

I'm not 100% sure of the best way to deal with the supply to my mount. I have heard people just put in a fuse, some use DC-DC converters etc

So what's the best and safest bet for me here:

1. Just fuse the positive line ?           If so, what size fuse should I use ?

2. Use a DC-DC step up converter to get the voltage up a couple of volts and then fuse that  ????   If so, can anyone suggest/link me to an appropriate item  ?

What do you think ??

 

Regards

Paul

[Cornelius Varley]

I'm not sure why you would choose option 2. 
For option  1 this power cable http://www.firstlightoptics.com/power-accessories/skytron-power-supply-cable-skywatcher-eq3-2-eq5-heq5-eq6-series-mounts.html uses a fast blow 3amp fuse, so you should incorporate the same into your powere cable.

[Physopto]

I had a NEQ6, the only reason to use a DC/DC converter is if you intend to use the battery and allow it to deplete beyond 1/2-2/3s of its full charge. As a lead acid battery discharges the voltage drops, a bit like the water leaving a hose pipe held horizontally. The fall of voltage is such that the NEQ6 tries to take more current as the voltage drops to apply the same power to the circuits. Not good for the mount. The NEQ6 manual will give the currents taken for lower voltages. If you can keep the voltage stable at 12.2 volts at all times the mounte will operate in a more stable manner. The mount can take voltages between, if memory serves me correctly,  11-16 volts. But a lead acid battery is fully discharged at 10.6 volts. You will loose some voltage due to wiring and connections to the mount. So the mount may be very close to completely discharging the battery if it is allowed to run into that situation. Not good for the battery or the mount.  A good method is to charge the battery whilst it is in use. The battery voltage can rise then above a fully charged (12.8volts), as it needs to go to 14.4 volts to become fully charged. This excess voltage is called surface charge and once the charger is removed it will dissipate  over about a 12 -24 hour period to a nominal 12.8 volts. This is assuming it is not in circuit. The point I am getting at is that if you charge and use a DC/DC stabilised supply your mount will only see 12.2 volts regardless of the battery voltage, as long as the stabilised supply is capable of supplying the current. Your battery can be left on charge all the time during the time you are using the mount. 

The only proviso is that you use a long lead from the battery to the mount. The battery needs to be well ventilated at all times and no where near any source of ignition. A lead acid battery starts venting hydrogen gas once the charging voltage gets to about 13.6 volts. The amount of gas is dependant upon the charging current. Even sealed for life batteries vent hydrogen gas during this phase of their charging, if the charge rate is too great. A source of ignition can be something like just switching on or off a light, even a torch. You cannot smell hydrogen gas!

The safest lead acid batteries are the gel type that are sealed. I used a 55 Ah one for several years. The best type of chargers are the inteligent type, with several stages of automatic charging. CTEK being the type I used. They have the added safety factor that if disconnected inadvertently from the battery whilst still charging there is no spark, e.g. much safer.

You  definitely need a fuse in the positive line to your mount of the appropriate value. 

In short if you are not going to charge your battery whilst in use and use it until the battery becomes well depleted then a DC/DC stabilised supply is a boon. But the battery will not last long as using it in that way kills batteries quickly. 

If you intend to charge at all times during use then the NEQ6 can take the higher voltages during a charge cycle. But but the voltage will be variable unless you use a stabilised converter. 

It is your choice in the end. You can easily get a whole nights use out of a 55Ah battery on an EQ6 type mount, then just recharge in the morning. That way your battery never gets too far discharged and will last much longer ( possibly years).

if you intend to supply other items then you may have to use a constant charge system.

Derek

[Gina]

I found my NEQ6 stopped working properly below 12.5v.

[Tinker1947]

The voltage really needs to be over 12 volts, while the mount is tracking its fine but a slew and the voltage drop will screw up the tracking so the scope loses its position, a flickering LED indicates the mount is not happy with the supplied voltage.....

[Physopto]

I agree with both Gina and Tinker above. I do run my gear off DC/DC stabilised converters where necessary, but I did not for my NEQ6. I did keep the battery on charge at all times when in use though. I only once managed to see the flashing red led, purely my own fault as I missed a blown fuse in the charger. If you are not happy with chancing a release of Hydrogen gas you can use the "Supply" option on a CTEK charger to get a permanent 13.6 volts. BUT then there is no spark protection in the circuit or short circuit protection. You have to be extremely careful then, not advised to be honest!

The flashing RED LED means you are at too low a voltage and the mount is sucking above the recommended supply current through its circuits. If the LED gets faster you are even further into the "Blown Circuit Board " territory.

Every body has their own preferred method of supply, probably bourn out of experience and what works for them!

Derek

[rweust]

My NEQ6 doesn't provide any trouble as long as the voltage stays 11.6V or higher. I used to have some trouble, but it was caused by a bad supply cable and connection. What I did was use the 12V DC supply cable of an old portable car fridge (something about 4 mm2 fine flexible copper). It proved much better than the loudspeaker cable I used before this. Furthermore get rid of the 5.5/2.1 mm DC socket of the NEQ6 itself and assemble a proper power socket. I use an industrial  13A Weipu push-pull connector, not cheap, but worth every penny. The last thing I did was solder a 2200uF electrolytic capacitor over the power supply connection. It will just fit behind the PCB in the NEQ6 and filters the last of the short power drops out that sometimes clearly appear on the power supply of the NEQ6 (maybe caused by the step motors and drivers).

 

 

 

If you have your mount more stable, nothing stands in your way to feed it directly from a lead acid battery. A deep-cycle lead acid battery will still provide 11.8V, even when it is discharched to 80% DOD and you are drawing a current of 0.1C, with my 36Ah AGM cyclic lead acid battery, still 3.6A continuous. Only at low temperatures around freezing (0 °C) the voltage will drop another 0.5 °C, but in praxis the case of my (home build) power tank will keep the battery warmer than that, certainly when 0.1C discharging current is drawn.
 

May I recommend a deep-cycle, AGM (absorbed glass mat) lead acid battery you can discharge to 80% DOD (depth-of-discharge) with still 250-300 full charge/discharge cycles life time left, if you are thinking about capacities of 75Ah. Don't use a starting (car) battery! They can’t be discharged over 40% DOD without damaging their capacity and life time of only half, anyway (150 full charge/discharge cycles at 30-40% DOD).

 

I wouldn't recommend the ready to use 3A fused supply cables either, they probably haven't got the square millimeters copper inside to get low enough voltage drop. Mine is fused at 5A, but is able to feed al lot more current.

 

Robert.