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CG-4 dual axis drives power: 12v to 6v converter?

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#1 Yun-Oh

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Posted 20 January 2014 - 10:08 PM

I installed dual axis drives on my CG-4 mount, which are run by 4 D-cell batteries. The problem is that the batteries drain really fast. I normally get just one night out of 4 fresh batteries (the manual says up to 20 hours).

I do use the 8x speed option quite a bit because it is easier to center the target in the field of view, but even that shouldn't make the battery drain that fast.

So, I did some search on the DC to DC converter that allows me to use my main battery (12v, 18 Ah) to power CG-4 motors. Would something like this work?

http://www.powerstream.com/dc6.htm

Or, is there something I'm doing wrong? The scope is well balanced and the motors seem to work just fine, but the controller light starts blinking after about 5-6 hours of use, and the voltage is down to about 5.7v at that point.

The above converter has 2.2 amp rating, and I believe it should be an enough draw for the CG-4 motors. Am I right?

I did search for relevant information on various astro forums, but found some conflicting posts, so just want to ask one more time before I go after the converter.

Thanks!

#2 Starhawk

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Posted 20 January 2014 - 11:35 PM

Don't do it. Run it off the battery pack only. There's no voltage protection- it can run on the D cells, and can be burned up by anything more.

-Rich

#3 Yun-Oh

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Posted 20 January 2014 - 11:54 PM

Hmmm... The spec on the web link shows 1% line regulation at 12v input and 6v output. Doesn't it mean voltage regulation, in other words, protection? Fresh 4 D-cell batteries in the supplied battery pouch actually outputs 6.3v when I measured it, so I believe there is a little room? I'm not an engineer, so can you explain what you mean by protection? Thanks!

#4 beatlejuice

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Posted 21 January 2014 - 12:21 AM

Unfortunately if you are using the mount for visual only I think you made a mistake in buying the dual axis drive. I use the single axis drive from Orion with the same battery pack and it lasts quite a long time.

Making corrections in Dec is pretty simple with the dec slo-mo cable so the only time that you use the 8x is for minor corrections in RA which isn't that often.

Your best bet is to remove the dec motor, re-attach the slo-mo cable and run the RA only. I am guessing that you are doing more corrections in Dec than in RA and this will more than double your battery life.

Eric

#5 Yun-Oh

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Posted 21 January 2014 - 12:34 AM

Unfortunately if you are using the mount for visual only I think you made a mistake in buying the dual axis drive. I use the single axis drive from Orion with the same battery pack and it lasts quite a long time.

Making corrections in Dec is pretty simple with the dec slo-mo cable so the only time that you use the 8x is for minor corrections in RA which isn't that often.

Your best bet is to remove the dec motor, re-attach the slo-mo cable and run the RA only. I am guessing that you are doing more corrections in Dec than in RA and this will more than double your battery life.

Eric


Thank you for the suggestion! It makes sense. I will stick with only RA motor for now until I figure out a way to use a 12v external power source.

#6 Starhawk

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Posted 21 January 2014 - 01:48 AM

No, it doesn't make sense unless you use the dec continuously, which no one does.

The protection I refer to is over voltage and over current protection for the drive circuit. None is needed for D cells, so it doesn't have any. You can burn out the controller very, very, very easily by using alternate sources. As it turns out, the D cells last many nights of observing.

-Rich

#7 Yun-Oh

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Posted 21 January 2014 - 02:26 AM

No, it doesn't make sense unless you use the dec continuously, which no one does.


Well, I was using the DEC slewing rather intensively while I was centering the targets, and I go through quite a few targets in a night. I guess it adds up. Being the power hog 8x slewing is, I think I can at least cut down the power consumption to some level by not using the DEC motor.

The protection I refer to is over voltage and over current protection for the drive circuit. None is needed for D cells, so it doesn't have any. You can burn out the controller very, very, very easily by using alternate sources. As it turns out, the D cells last many nights of observing.

-Rich


That's what I was puzzled about. If the power source, such as the linked 12v-6v converter, does have over-voltage and over-current protection, wouldn't it be okay? It looks like the 6v output is very clean and consistent.

Thanks for your help!

#8 Ouranos

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Posted 21 January 2014 - 08:36 AM

Whatever you do - be a bit careful. I have the same mount with the drives added and I burned up the hand controller by using the wrong voltage power source.

#9 Starhawk

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Posted 21 January 2014 - 09:19 AM

You aren't supposed to slew with it- break the clutches and move the scope manually, then take over with the drive.

I've already burned up one CG-4 trying to adapt it to a new power supply, and I am an engineer. Do the manual slew trick and you'll find the drive lasts well enough, and a burned up controller means a new drive, which would pay for many years worth of D cells.

-Rich

No, it doesn't make sense unless you use the dec continuously, which no one does.


Well, I was using the DEC slewing rather intensively while I was centering the targets, and I go through quite a few targets in a night. I guess it adds up. Being the power hog 8x slewing is, I think I can at least cut down the power consumption to some level by not using the DEC motor.

The protection I refer to is over voltage and over current protection for the drive circuit. None is needed for D cells, so it doesn't have any. You can burn out the controller very, very, very easily by using alternate sources. As it turns out, the D cells last many nights of observing.

-Rich


That's what I was puzzled about. If the power source, such as the linked 12v-6v converter, does have over-voltage and over-current protection, wouldn't it be okay? It looks like the 6v output is very clean and consistent.

Thanks for your help!



#10 Geo.

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Posted 21 January 2014 - 02:50 PM

I don't see why a buck converter won't work fine. The real problem here is that the Synta handbox has NO voltage regulation, NADA! The ICs are designed to run at a VCC of 5vDC. They can tolerate 6v, so why spend $0.29 on a L7805 to provide safe VCC when you can toss a penny resistor? The Synta steppers are rated 6v at 1 amp.

These buck converters are built around the LM2596 series of regulators that are capable of driving a 3A load with excellent line and load regulation. The motor is only going to draw the amps it needs and the votage is held to tight limits. http://www.ti.com/li...link/lm2596.pdf

For $4 on eBay you can pick up the LM2596 set up as a buck converter with these specs:

4-38V to 1.25-36V DC Buck Step Down Converter DC
Module Properties: non-isolated step-down module (BUCK)
Input voltage: 4-38V
Output voltage:1.25-36V adjustable w/pot
Output current :0-5A (recommended for use within 4.5A)
Output power: recommended for use in below 75W, more than 50W please add heat sink.
Working temperature: -40 to +85 degrees
Operating Frequency: 180KHz
Conversion efficiency: up to 96%
Load regulation: 0.8%
Voltage Regulation: 0.8%
Short-circuit protection: Yes (the limited current is 8A)
Over-temperature protection: Yes (automatic shutdown when over-temperature)
Input reverse polarity protection: No
Wiring: Solder points V-IN & V-OUT
Dimensions: 54* 23*18 (mm)

Attached Files



#11 Starhawk

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Posted 22 January 2014 - 12:12 PM

Note, one funny feature of the CG-4 drive control, which keeps a regular AC adapter from working, even if it tops out at no more than 6 volts, is the large current swings cause them to drop under voltage. You need the amperage capability of D-cells to handle this. So, a typical 500mA 6v power supply doesn't work.

George's method may work, or it may not be able to provide power at the right rate with the right voltage. Needless to say, I'm skeptical of playing with this, especially since the way it fails is it just sort of works afterwards, then you realize it doesn't actually track at all.

-Rich

#12 Yun-Oh

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Posted 23 January 2014 - 08:03 AM

You aren't supposed to slew with it- break the clutches and move the scope manually, then take over with the drive.


I was not using the motor when I moved to one target to another. Of course, I did it by unlocking the clutch and pushing the scope by hand. But I did use the motor quite a bit while centering the target. The light on the controller started to blink after about 5 hours. The voltage shows about 5.6v when it started to blink. The manual says the battery pack is supposed to last about 20 hours, so it is not designed to use for more than a few nights in the first place. I don't think I want to pile up that many used batteries. It's a huge waste in my opinion.

I don't see why a buck converter won't work fine. The real problem here is that the Synta handbox has NO voltage regulation, NADA! The ICs are designed to run at a VCC of 5vDC. They can tolerate 6v, so why spend $0.29 on a L7805 to provide safe VCC when you can toss a penny resistor? The Synta steppers are rated 6v at 1 amp.

These buck converters are built around the LM2596 series of regulators that are capable of driving a 3A load with excellent line and load regulation. The motor is only going to draw the amps it needs and the votage is held to tight limits.


Thanks for the detailed information, George! This is what I thought, but apparently there is something we are missing, I think. I've heard quite a number of people frying the controller, and with proper buck converter, I don't think it should happen. Again, I'm not an EE, so I humbly stay puzzled... :question:

Thank you for your thoughts, everyone! I will have to decide to risk frying my controller or maybe get a Lacerta controller. Lacerta is overpriced in my opinion, but it certainly does offer everything you need (6-12v power input, autoguider port, 16x slew, solar and lunar speeds). While I'm at it, I might even order Lacerta MGen II for stand-alone guiding. :cool: Now that's an expensive proposition... :tonofbricks:

Or, maybe try rechargeable batteries. The problem though is that NiMH batteries give 1.2v, not 1.5v like Alkalines. Having the controller light start to blink at 5.6v doesn't give me confidence that 1.2v (4.8v when four are serially connected) would be enough.

I thought this would be a simple motor addition to CG-4, but I guess nothing is simple... :bawling:

#13 Eddgie

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Posted 23 January 2014 - 09:05 AM

I know that this might sound like a silly question, but what kind of batteries are you using?

Many people use very inexpensive (cheap) D batteries labeled "Heavy Duty." These are now mostly Zinc Chloride which is inferrior to modern but much more expensive Alkaline batteries.

These batteries are in fact pretty horrible batteries that appear big and powerful, but often are no better than some top tier AA rechargable batteries.

As for the DEC motor, the DEC motor only runs when you push the button while the RA motor never stops.. Yes, using the DEC does drain the battery more, but in four hour so running, my bet is the RA motor uses 95% of the power from the battery.

My old Vixen Polaris uses a single 9V battery that is smaller than a D cell and it will run the mount for hours with no problem and the motor never stops.

I would look carefully at the batteries you are using.

If they are general puprose "Heavy Duty" and not even alkaline, my bet is that this is where your problem is.

These are just crummy batteries not hardly worth buying.

As an example, the Eneloop rechargeables I use will run my 12" Go-To dob for several hours.

Try to find the Amp Hour rating on the batteries you are using, and before you give up on these (which seems to be impossible on most cheap D batteries).

Using better batteries gets expensive though, so you may want to consider just investing in some good AA rechargables and buying a AA battery hodler.

This will be smaller and lighther than what you have, and if the batteries you are currently using are cheap non-alkalines, these may actually run longer than what you have.

If you have two packs, you can just swap a pack of rechargbles when they run low.

You can also use the current holder by using a sleve:

"D" size sleeve for AA batteries

AA Rechargable battery holder

Also, you may need to use 5 AA rechargables. These are rated at 1.35 vdc, so this will give youa bit over 6 vdc, but this is not usually a problem. Maybe it will run on 4 though, but my guess is your light is a low voltage light indicator and it might come on early. The rechargables drop to 1.3 pretty quickly, but then hold that much longer than a similar sized standard battery.

Anyway, don't discount the fact that if you are using "Heavy Duty" batteries, your problem is really just te batteries themselves.

"Heavy Duty" non alkaline batteries are about the worst batteries made, and some modern rechargables will easily outlast.

I usually use a 12 volt 7 amp hour battery to run my dob, but I always keep a 10AA pack handy because sometimes I forget to recharge the 12 volt battery. I can pop in the 10 pack and do a couple of hour session in an emergency.

Hope this is helpful to you in some way.

#14 Yun-Oh

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Posted 23 January 2014 - 07:03 PM

I was using Duracell and Energizer Alkaline batteries. I will look more into the rechargeables and see if it would work. Having 5 might be necessary because of the lower voltage. The problem is that there is no way to test anything without taking the risk of frying the board. I hope Celestron can answer this question. I will send them an email.

Thanks!

#15 Eddgie

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Posted 23 January 2014 - 07:52 PM

That is why I use 10 AAs for my CGE and Go-To dob (though again, this is only in an emergency when I forget to charge the 12 V 7 ah battery. 8 Batteries is not enough to give a full 12 VDC, though these batteries run at 1.3 volts until they are very close to running out.

If you are using good alkalines though, the AAs won't run as long, but you can just have multiple sets in small packs and just trade out a pack when it starts to get weak.

But you may have some issue. I would think that a set of 4 alkaline Ds would run you longer than you are getting.

Is the RA axis perhaps very stiff? Is the motor on a clutch where you can use the manual RA knob?

Try turning the RA knob and see if the motion feels very stiff.

An electric motor develops full torque at 0 RPM, but if there is resistance, it will draw full current at 0 RPM as well. Most motors used less energy when they are actually running at rated speed than when starting up.

If your mount is very stiff in RA, you may want to consider a tear down and a re-lube with a high quality grease, and then a re-mesh of the worm to get the movement as low friction as possible.

#16 Yun-Oh

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Posted 24 January 2014 - 06:18 AM

Is the RA axis perhaps very stiff? Is the motor on a clutch where you can use the manual RA knob?


It is a great point. I doubt it is causing my problem though. Before installing the RA motor, I was able to turn the many RA control by just sliding my finger over it. Maybe the motor connection is giving the worm too much pressure, but it is very unlikely.

I would think that a set of 4 alkaline Ds would run you longer than you are getting.


How long they last is not that important. I would be more than happy to replace the batteries in the middle of observing session as long as they can be reused. I'm just not comfortable with used batteries piling up and costing too much.

I will try your AA battery suggestion and see if it works. Thank you for sharing your experience. And wish me luck... :crazy:

#17 Eddgie

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Posted 24 January 2014 - 09:25 AM

Well, here is the really great news.

The Eneloop 2500ma batteries are outstanding. They have a spec of something like 1500 recharges and they have very low self discharge.

While it seems expensvie to go this route, once you make the investment, you could literraly fully replace all the AA and AAA batteries in your house.

I use all Eneloop and Amazon Basic rechargables (also a low discharge design) and have not had to buy a throw away AA or AAA in a couple of years.

So, if they don't work for you in the telescope, you will be able to re-deploy them to some household device like remote control or flashlight or Telrad or some other high consumptoin device and in time, you will easily get your money back.

And maybe your drive is just power hungry. But it is odd that my Polaris will run for hours off of a single 9v battery.

And by the way, I run the POlaris off of a rechargable too. I have three 9V recharvable batteris. I keep on in the charger and I use one in the handset and one in my Orion Red/White astro light.

The 9vdc rechargables may make more sense than any of the others becasue of the high replacement cost of these batteries.

Anyway, if you get rechargables, my advice is to go ahead and get a good one like the Eneloop because in time, the battery will indeed pay for itself and they are one of the very best low self discharge batteries on the market today.

Even if it winds up in your remote or something, you will get your money out of it, but they are better used in devices where they are used a lot.

Let us know how it works out, but do look again at your RA drive. The RA motor never stops running, and I feel like maybe you have some drag or somethinng.

Also, if you can, try swapping the RA and DEC motor. Maybe there is some issue with the RA motor itself...

#18 Yun-Oh

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Posted 25 January 2014 - 03:27 AM

The Eneloop 2500ma batteries are outstanding. They have a spec of something like 1500 recharges and they have very low self discharge.


Yes, it was the rechargeables I was looking into as well. It's pretty much the only one with enough load capacity. I just ordered them, so I will report back.

Also, if you can, try swapping the RA and DEC motor. Maybe there is some issue with the RA motor itself...


Thank you for the suggestion. I tried it, but no difference. I believe they are both working fine. It was worth the try though. Taking at least one possibility out of the equation.

I also talked to someone at Celestron, and apparently using a buck converter is not recommended because it does have the potential to fry the controller. It doesn't make sense to me, but there are many things I don't understand. So, buck converter is also out of the equation.

It leaves me with only rechargeable battery option. I will report back when I get them. It will be either "it works!" or "I fried the controller"... :question:

#19 Yun-Oh

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Posted 02 February 2014 - 12:23 AM

Reporting back!

I finally received the rechargeable batteries (Eneloop 2500mAh AA) today after Amazon struggled to ship it out quickly. They arrived precharged, so I put them in the D-cell spacers (also ordered through Amazon) and stuffed the Celestron battery pouch with them.

Now, it's time to connect the cables and turn on the controller. Did I fry the controller? Fortunately, no. :jump:

It worked! I don't know if the tracking was accurate (the test was done indoors since it was raining), but it moved the motors (both tracking and slewing) without a problem.

This was a good start, and the real test came. The Eneloop batteries were measured just shy of 1.4v at the beginning and quickly dropped to 1.3v in about 2.5 hours. At this point, the light on the controller starts blinking, a warning for low battery. I left the mount to track, and about after 6 hours, the controller light turned to red and the motors didn't turn anymore. The batteries are measured at less than 1.1v at this point.

Now I'm recharging the batteries (9 hours for 4 AAs), so let's see if a full charge makes any difference tomorrow. What I know now though is that the AA rechargeables with D-cell spacers do work and they don't fry the controller (yet...).

I still think 6 hours is rather short, and it would be shorter with 8x move for centering used time to time. But, at the least, now I have an alternative to regular D batteries. I guess I can just buy 8 more, use 4 and keep a set of 4 ready for replacement for the night, while having 4 in the charger.

It is still an open question why this controller/motors combo consumes power so quickly, but rechargeables should save me from piling up drained D-cell batteries.

I will report back again when the sky clears (hopefully soon) and I can verify that the tacking is accurate.

#20 Eddgie

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Posted 03 February 2014 - 03:12 PM

I am to at a loss as to why this particular motor/controller is so battery hungry.

Be aware that you can get advanced battery chargers that can recharge these batteries at 1000ma, which means they will charge in about 2 hours.

The best ones will let you not only do a quick recharge, but will also give you information about how much charge was required.

And my thinking was that you could do exactly what you are talking about, which is to just get two (or even three) sets of these and that way you could just swap out after several hours to a fresh pack.

I use a small holder that you can get on Amazon. For you, something like this might work:

AA holder

These have normal 9 VDC connectors so if you put these on your cable (if it does not already have them) you would not even have to pull the batteries out of the holder, you would just swap in another holder already loaded with batteries.

Even if you don't get longer run time, using these will save you a huge amount of money in the long run.

I hope this is helpful.

#21 Eddgie

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Posted 03 February 2014 - 03:27 PM

I know this seems like a lot, but this is the charger that I use.

Once you start using these kinds of high quality rechargables, you realize that there is no need to buy throw away batteries anyomre, and you start wanting to use them in in everything.

I now have AA and AAA MiMh batteries in my Remotes, computer mouse(s), flashlights (I only by LED flashlights now that work with AA batteries.. I have a Cree that will blind you it is so bright) Telrad, and just about anytying else I can.

I have not had to buy a disposable battery in years.

While these chargers seem expensive, they charge fast and they tell you exactly how much charge the batteries took.

They can also let you pair batteries by capacity (if you have one battery that runs low before the others then you get less run out of a pack).

Anyway, if you decide you like these, consider gettting some more of these "Pre-charged" batteries for other things around the house and investing in a high quality charger/conditioner to get the most out of them.

Mh Battery Charger

#22 Jon Isaacs

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Posted 03 February 2014 - 03:28 PM

I am to at a loss as to why this particular motor/controller is so battery hungry.



I am also surprised that batteries are not lasting longer. My old Orion AstroView, same basic thing, lasts quite a long time with even standard D cells. Alkaline Batteries have a capacity of between 12amp hours and 18 amp hours. If they are only lasting 6 hours, that says the controller is drawing more than an amp on a continuous basis, that seems like a lot of juice.

I did disconnect that Dec drive on mine as Eric suggested. I didn't do it to save power, I did because the drives are so slow and for visual it's quicker and more reliable to slew manually.

Jon

#23 Eddgie

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Posted 03 February 2014 - 03:31 PM

And if you are going to keep a spare pack, you may be able to get away with less expensive batteries. The Eneloop 2000s cost much less.

You may decide that three sets of 2000s makes more sets than two sets of 2500s.

I am very curious as to why your drives use so much.

I can run the single axis of my Vixen Polaris (one 9 volt battery) for about 24 hours on that one battery!

I recently left it on one day after doiing some solar observing and went out the next day to observe, and the darn thing was still runnin! Amazing.

#24 Yun-Oh

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Posted 03 February 2014 - 06:19 PM

Ed,

Thank you so much for detailed input. I ran another test yesterday with the rechargeable batteries fully charged again, and this time it lasted about 12 hours. The light on the controller started to blink at about 7 hour mark (voltage drops to 1.2v each), and it still lasted 5 more hours (voltage is about 1.0v each when the light turned red).

It is a good sign and more consistent with your results.

However, I think the problem with this particular controller is that it draws so much more power when the 4x or 8x speeds are used. I didn't touch the buttons at all yesterday, and it lasted significantly longer than the day before when I played with the 4x and 8x speeds. The controller normally draws about 400mA with only RA tracking, but it suddenly jumps to 3.5A when a slew button is pressed at 8x. This kind of sudden change just kills the battery, I believe.

So the lesson is that use the buttons as little as possible... :( With only tracking, the rechargeables would last a whole night.

Well, the good news is that with two days of testing, I haven't fried the controller. The tracking is good and even more consistent than the regular batteries because the rechargeables maintain 1.2v voltage for a long time before it kind of abruptly drops to 1.0v, while regular ones continuously drops in voltage at all times.

With these test results, I think your advice is dead on. I will buy 2000mA ones rather than the 2500mA ones, and it should work fine just for tracking. Charger is not a big deal because I am going to keep one set fully charged at all times, so I can just charge the used one during the day.

In summary, I believe the design of this controller cut too many corners on protection and safety to function reliably with various power sources. At least we figured out an alternative to regular D-cell batteries, so I will settle with that. And the battery pouch is way lighter with these AA rechargeables in spacers. :)

Thanks everyone for your input!

#25 Eddgie

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Posted 04 February 2014 - 09:17 AM

Happy to help. And again, if your cable uses a 9 volt connector, you can get the plastic holders in the link I sent you and have a backup pack at all time.

At least you are not going to be buying a bunch of D cell batteries every time you use the scope, and that is the beauty of these high quality rechargables. Even if you have to change batteries, you are still not having to buy disposables time after time after time.

And I too like the very small size.

Using the 6 cell hodler (dummy battery is you only want to run 5), you can velcro it to the RA housing and not have any cables or batteries hanging down.

Since this is a non-Go-To though, there should not be any issue with just swapping a pack out with a standby pack. That is what I do. I have two packs and I just snap one off and plug the other one in.

Now my packs are 10 AAs, so a lot of money for batteries, but normally I use a 12 vod 7 ah battery.

I keep these handy because sometimes I forget to plug in my 7 ah battery after a session to recharge, and the AA packs make sure that I always have something I can run the scopes with.

I also have a cable with two 9 vdc connectors on the end which allows me to either run two packs at once, or just hot swap (plug the second pack, unplug the first pack) so I don't loose alignment.

As I mentioned though I have a box of these batteries that I use around the house so I always have spares charged for when I need to replace remote or whatever.

You can also buy 8 and 10 bay chargers.

Hope this works for you. At least you won't be buying D cell batteries by the box anymore.






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