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I just love my GOTO Equatorial Mount. Since it has a 22lb carrying capacity, it does not come with any batteries. In order for me to travel, I need to add my own battery power supply. In this post I’ll review the Talentcell 12V 6.5 aH capacity battery bank which appears to be the same model as the Agena AstroCell AC-B05.
Get yours at Amazon or AgenaAstro;
12 Battery Bank
Most mounts take a 12V power supply with an input capacity of around 2 to 3 amps. This of course varies but this is a typical range. I use the ASIAir and I can see in realtime what it is consuming. For tracking and running 2 cameras and one filter wheel mine uses about 1.1A. This will be higher for slewing but you cannot view the power consumption while the scope is slewing.
If you add more accessories such as dew heaters or an auto focuser, then the power requirements will go up.
Best Chemistry For 12V Power – Li-ION vs LIFEPO4
For lithium batteries, there are 2 common chemistries. Li-Ion and LIFEPO4. LIFEPO4 stand for Lithium Iron Phosphate. There are a few differences between these two chemistries. Li-ion has a higher energy density. LIFEPO4 is lower, but it is considered one of the safest batteries available. Not only are they safe, they have a more stable discharge curve then Li-ion. What this means for astronomers is that they can maintain a higher voltage over the length of the discharge curve than Li-ion. The only other disadvantage to LIFEPO4 is that they tend to cost more. This is due to the not being mass produced to the extent that Li-ion batteries are produced.
If you read the reviews for any Li-ion battery packs intended for telescopes, you will see people complaining about the voltage. It’s just a result of the chemistry and the number of cells in series used in the pack.
Talentcell produces both versions with the Li-ion packs being nearly 50% the cost of LIFEPO4.
For the Li-ion version, almost all manufacturers use a 3 cell design using the 18650 cell. Well that’s a bit of a problem for applications needing an actual 12V output. The reason being is that 3 cells in series equals about 10.2V total when each cell is at 3.4V. 3.4V is about the middle of the road on the discharge curve.
In contrast, the LIFEPO4 version uses 4 cells. At a nominal voltage of 3.2 per cell, this equals 12.8V which is perfect for a 12V power application.
Specifications
- 1 – 12V unregulated DC output with a max. capacity of 5A at 6500mAh
- 1 – 9V unregulated DC output with a max. capacity of 2A at 9244mAh
- 1 – 5V DC USB output with a max. capacity of 2A at 1664mAh
- Weight: 760g or 26.8oz
- Dimensions: 43 x 89.2 x 168mm (1.7 x 3.5 x 6.6″)
Includes:
- 14.6 V DC charger
- 1x DC5521 male to DC5521 male power cable
- 1x DC4017 male to DC5521 male power cable
How Big Of A Battery Do You Need?
To calculate the capacity that you need, divide the capacity of the battery by your average total usage in amps.
Talentcell makes 2 versions of LIFEPO4 a 6.5aH and a 12.8aH version.
Example.
1.1 average amp usage = 6.5/1.1 or 5.9 hour run time.
1.1 average amps usage with the 12.8ah version works out to 12.8/1.1 or 11.6 hour run time
Output Connections
The battery comes with 3 output connections. One for 9v, 12v and one USB 5v output. This gives you a lot of options and allows for multiple connections at the same time.
I plan to use a single 12V output and the let the ASIAir distribute the power through their on board 12v output and USB ports. This makes is less cluttered and I can run a single power cable up to the mount instead of many.
Conclusion
There are many choices to choose from even from just TalentCell. If you must have a nominal output of 12V then I would go with either of the 2 LIFEPO4 versions. However if your voltage requirements are not that critical, you can save some money by purchasing the Li-Ion versions. Before you do anything however, calculate how much capacity you need.