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Battery Pack
for the
ETX-90 Scope


The ETX-90 needs electrical power -- power can come from three sources:

  • Internal AA batteries -- nine AA batteries can be inserted into the battery compartment in the scope base.  These are good for only a few hours then you must replace them.
  • AC adapter.  Plug it into the wall, plug a power cord from the adapter to the scope.
  • A heavy-duty battery pack.  This is my favorite -- a rechargeable heavy-duty battery pack that can run the scope for hours and hours, then you recharge it.

You can find AC adapters and battery packs from several manufacturers or dealers.   I suggest you try ScopeTronix -- there are others but I have had excellent experience with them.  Go to the ScopeTronix site, check the Table of Contents for the link to accessories for the Meade ETX scopes -- you will find AC adapters and battery packs there.

My modifications to a ScopeTronix battery pack

The original ScopeTronix battery pack

I purchased a battery pack from ScopeTronix -- it is on their site under Field and Power Accessories --

Vector Pocket Power™
4.5 amp Hour, 12Vdc Portable Power Pack
ScopeTronix part number VPPAK45

I am very pleased with this power pack.  It comes with a recharger.  I observe 30-60 minutes a night, 2-3 nights a week.  I recharge this battery pack once a month and that has always been sufficient.  If you observe for longer times, you would need to recharge more often.

I recommend this battery pack WITH ONE RESERVATION -- there is an important modification that I made to my battery pack that you may need to make if you purchase this battery pack.

Modification

I found a weakness on this battery pack.  Look at this photo.  Note that the battery pack has a socket -- it's the same as a vehicle cigarette lighter socket.   The power cord from the scope plugs into this socket.  Note that the recharger has a plug -- to recharge the battery pack, plug this into the socket and plug the charger into the wall.

btry pck-2.jpg (47351 bytes)

As the battery pack came originally, the socket and plug were weak points.  The socket attached to the battery pack had a spring-loaded cover and the socket itself was not deep.  The plug on the end of the scope power cord would sometime slip out of the socket on the battery pack, thereby cutting off electrical power to the scope.  The spring-loaded cover was weak -- the third time I used the battery pack, the cover popped off and flew across the room.

I went to Radio Shack and bought a replacement cigarette lighter socket and plug.   After I replaced the original socket and plug, I realized I should have made photos of the modification process -- but -- I did not, so here are photos of the finished modification.

plg sckt-1.jpg (38148 bytes)

On the left of this photo is the red nylon battery case.  In the center of the photo is the Radio Shack cigarette lighter socket that I used to replace the original socket.  This socket has a rubber plug attached that covers the socket when it is not in use.  The object on the right is the plug coming from the recharger -- this is also a Radio Shack item that plugs into the socket to recharge the battery pack -- I cut off the original plug and replaced it with this one.

Go back and look at the first photo.  Note that the socket is attached to the battery with two wires -- and -- note that there is a small pocket on the side of the battery's nylon cover into which the socket fits. Now look at this photo.   When I removed the original socket, it simply unplugged -- the wire ends had spade connectors.  I made up two pieces of wire -- red for positive, black for negative -- with spade connectors.  These two pieces of wire allow the socket to extend from the battery pack -- this makes it easier to pull out the socket and plug/unplug the power cord from the scope or from the recharger.

wiring.jpg (31916 bytes)

I suspect that most of these medium-size battery packs are made the same way.  If you purchase one, look at the socket and plug arrangement -- you probably will want to replace the flimsy originals with heavier duty devices -- take the battery pack to Radio Shack and look at their stuff -- you'll figure it out.

Why not use rechargeable batteries in the ETX battery compartment?

You can, of course, use rechargeable batteries in the ETX battery compartment.   You could use Nickel-Cadmium (NiCd) batteries or rechargeable Lithium Ion batteries.  There are a couple of problems with rechargeables.

  1. The scope battery compartment is a bit of a pain to get to.  The access door is on the BOTTOM of the scope housing.  To replace the internal batteries, you must remove the scope from the tripod.  I am too lazy to do this every time I need to change batteries.
  2. Rechargeables do not have the same voltage output as alkalines.  For example, an alkaline AA will produce 1.5 volts for some time.  NiCd's produce slightly less voltage.  This, with 8 alkaline AA batteries, you get 12 volts DC. With NiCd's, you get 10-11 volts.   The scope will work, but, as the voltage drops from use, you will need to replace the NiCd's more often than alkalines.  Ditto for Lithium Ion batteries.

Go to the Tech Tips page on Mike Weasner's Mighty ETX Site for discussions of the pros and cons of rechargeable batteries in the ETX battery compartment.  Lots of people use them.   I don't.

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