![[Home!]](../images/mighty_etx.jpg){kind=small}
Last updated: 13 September 2008
|
Last updated: 13 September 2008 |
Jump to today's update.
Sent: Monday, October 8, 2001 7:47:56 From: Lang.Michael@Orbital.COM (Michael Lang) Regarding Scott Pierces' question on rechargeable batteries in the ETX telescopes, as an ETX-125 owner tinkerer & explorer (no observing site is too remote for me, if it's in the USA), I would advise against use of NiCad's or NiMH batteries in the telescope internal 8-cell holders. To do so will power the scope at much less than the desired 12 volts, in fact, the scope will be powered at only 10.4 volts - best case. I have experimented with internal 1.65 amp-hour NiMH batteries and experienced glitchy performance and out right motor stalls and failure messages displayed on the Autostar. Now I only will use standard 1.5 volt alkaline cells or RayoVac rechargeable alkalines in the telescope base battery box - if I use internal batteries at all. I've found the best power source to be an external 12 volt pack. Power Sonic makes a series of Gel Cells that are based on Lead-Acid chemistry. These batteries are sealed (won't leak or vent gas) some are quite small, they are all very inexpensive - compared to NiCad's or NiMH cells, and they are easy and safe to recharge. I use the Power Sonic PS-1270, 7 amp-hour battery. I purchased it from "Batteries America" (http://www.mrnicd-ehyostco.com/). The battery has standard automotive crimp lugs for terminals . I bought everything required to assemble the pack, including a little digital volt meter at Radio Shack. I even bought a slick little fused coil-cord, with the correct connector for the telescope. (Don't forget to add a 1 amp fast blow in-line fuse). All electrical connections are overwrapped with silicone tape to seal and insulate them. The battery is nested inside a foam padded camera case. The case / battery pack measures about 8 X 5 X 4 inches. The case has a side pouch that I use for the charger, meter, and various adapter cables to charge the battery after several nights out under the stars. It all weighs about 6 pounds, and I set it on the accessory tray of the tripod - it helps stabilize the tripod and damp out vibrations. The foam padded case also keeps the battery warm on chilly nights, although for really frigid nights, I overwrap the case in a few layers of that silver-mylar material that Wal Mart sells as a "survival blanket". Since the battery warms up a little when powering the ETX, keeping that heat in the case ensures the battery output voltage constant and above 12 volts, even when I'm blue & can't feel my fingers. My pack has powered my ETX-125 for several days of nightly viewing without any recharging. And that's with a couple hours of use each night. (My ETX has an Autostar + electric focuser). To determine if a recharge is required, I check the pack voltage at the end of a night. If it's below 12 volts right after I power the scope off, I charge it until the voltage rises to 14.7 volts (usually overnight will do with my charger). If you want all the technical details on these really neat Power Sonic batteries, checkout the Power Sonic Web Site (http://www.power-sonic.co.uk/ and look under "12 volt SLA"). CAUTION CAUTION CAUTION DO buy a digital voltmeter. Radio shack sells a bunch of simple inexpensive units for under 30 bucks. Use it to check the polarity for any external power source, before you connect it to your ETX. Verify that when the red meter probe is connected to the center socket of the power plug, and the black meter lead is touching the outside (silver) barrel of the power plug, that the meter displays "+12 volts DC" . Don't worry, you can't be shocked if your fingers touch the power connector or meter probe contacts.) Be positively sure there is not a " - " (negative) symbol displayed on the meter. As a check that you've got it correct, reverse the meter leads: black to the power connector center socket, red to the outside barrel. The meter should display " - 12 V DC", if you've got it right. And don't let the volt meter probes touch each other, while you are making this measurement. If you have any questions, contact an expert before you connect up to your ETX for the first time. Most Radio Shack stores have a smart electronics-inclined High School kid or two who can help you out, if you have any questions. -------------------------------------------------------------------------------- Now for the faint hearted who don't want to tackle assembling such a pack; go to the Batteries America Web Site, and look for the BP-1270 Battery Pack. They didn't offer this when I built my pack, but for $69.95, you get pretty much everything you need to power your ETX. It's all in a slick little case, and has the cigarette plug connector, so all you have to do is buy the car adapter plug, and away you go............... -------------------------------------------------------------------------------- Michael Lang LANG.MICHAEl@ORBITAL.COM
Subject: Rechargeable Batteries addition Sent: Sunday, October 14, 2001 10:34:55 From: NArmstro@cha.ab.ca (Armstrong, Neil) On the rechargable battery front, I agree 101%. with Michael Lang. Nickel Metal Halide and Nickel Cadium batteries can only produce about 1.2 volts per cell. They do not produce enough voltage for optimum performance (autostar performance and slewing speeds). I ended up spending over 50 bucks for Ni-MHd and they can't even produce enough voltage. What I use is rechargable alkaline batteries. They produce the full 1.5 volts per cell. When I searched for satellites using my new 1.5 volt cells, the autostar only took about 2 to 3 seconds (it varies) whereas on the old Ni-MHd it would take over 30 seconds.
Subject: 12V 1800MAH Lithium Ion Battery Sent: Wednesday, September 10, 2008 19:54:38 From: Bob Harris (harrisb@cfl.rr.com) Attached is a report on the results of my evaluation of the 12V 1800MAH Lithium-Ion Battery that was mentioned on the ETX user group. Quick Summary: Fantastic. Bob Harris
12V Rechargeable Lithium-Ion Battery
I have just finished testing the 12V Rechargeable Lithium-Ion Battery that was mentioned recently on the ETX User Group. Thge battery is available for $5.87 (no joke) plus $9.97 shipping from the Ebay store of Goods-Keeper at the following URL:
Note: Communication with this Ebay seller is excellent, however, if you order this battery, be prepared to wait 2-3 weeks for delivery because it will be shipped from Hong Kong.
Product Features are as follows:
12V Rechargeable Lithium-Ion Battery for CCTV Camera
Input: 12.6V DC
Output: 10.8-12.6V DC
Current: 1800MAH
Size: 3-3/4x2-1/4x5/8
Includes: Power Adapter/Charger and Power Cable
SUMMARY: THE BATTERY POWERED MY ETX-125PE FOR FOUR (4) HOURS AND SHOWED NO SIGN OF SLOWING DOWN WHEN I POWERED DOWN FOR THE NIGHT.
When run down, the battery requires 8 hours for a full charge, however, my battery arrived almost fully charged and required only a minor top-up.
The power cable supplied with the battery had to be modified to accomodate the ETX-125 12V power connector.
The test was performed on my ETX-125PE with the dew shield and an 8x50 Amici right angle view finder installed (a little extra weight). The test was performed indoors due to the Florida hurricane season.
The first thing that I did when I started this test was to turn on the Utilities/Battery Alarm so that I would know when the battery was running out of juice.
I set the AutoStar to Tour and slewed through the Tour menu (many many times) to a new location in the sky every 2-3 minutes for 4 hours.
The battery alarm did not come on, nor did I detect a slowing of slew speed, after 4 hours when I shut down out of boredom.
CONCLUSION: THIS IS A GREAT BUY, VERY SMALL, AND PERFORMS VERY VERY WELL. MY TEST WAS FOR ONLY FOUR HOURS. IF YOU ASSUME THAT THIS IS THE LIMIT OF ITS CAPACITY (WHICH IT IS NOT), YOU CAN RUN TWO IN PARALLEL TO GIVE YOU A FULL NIGHTS VIEWING. THIS LITTLE BATTERY EVEN HAS ITS OWN ON-OFF SWITCH.
Go back to the Tech Tips page.
Go back to the ETX Home Page.