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Old 20-09-2021, 04:26 PM
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Swagman105 (Geoff)
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Using a power tool battery to power a telescope mount

I have plenty of 18v (Ozito) and 20v (Aldi) power tool batteries for my collection of power tools.
Wondering if anyone knows of a way to provide a 12v output from these batteries to power my telescope mount?
Also can anyone foresee any problems if an adaptor could be made or sourced?
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  #2  
Old 20-09-2021, 05:38 PM
AdamJL
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I asked the same question once on the NINA discord and they all said it was a bad idea without really telling me why. They’re not supposed to be run in parallel so that cuts the run time down but if you’re just running one bit of kit, then I think it’s a great idea
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Old 20-09-2021, 06:10 PM
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It is not really such a good idea, you will not be getting constant voltage as it starts to go flat, producing errors to the Mount. Just my two cents worth.

Leon
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Old 20-09-2021, 06:13 PM
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iborg (Philip)
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Hi Leon


You are right, but, that applies to any battery.


Philip
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Old 20-09-2021, 06:14 PM
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iborg (Philip)
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Hi

There are circuit boards available to do this sort of thing. A couple of examples in the links at the bottom.

I see two problems with doing this-
1: Being careful to not over discharge the battery (applies to any battery system of course)

2: Actually maintaining the electrical connection to the battery.

Neither of these should stop anyone trying it.


One other possible issue, is that many pieces of astro equipment are made to be powered from car batteries. These are only nominally 12V and should be something more like 12.6V when fully charged. It is possible that the mount actually needs a bit than 12.0V to slew at high speed for example. This is something I intend to test with my scope (an LX90).

I have no idea how significant an issue this is.



An example of modifying the battery to use for anything you want-
https://www.instructables.com/Make-a...-multipurpose/

For curiosities sake I have being doing a little more reading, there is an adapter on Thingiverse for Ozito batteries.
https://www.thingiverse.com/thing:2966117






Philip









https://www.ebay.com.au/itm/22436754...frcectupt=true


https://www.jaycar.com.au/24v-to-12v...sort=relevance

Last edited by iborg; 20-09-2021 at 06:37 PM.
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Old 20-09-2021, 07:50 PM
raymo
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I'm guessing that your ZEQ25 will draw anywhere between 1 and 2 amps,
depending on whether tracking or slewing, so you'd need the largest power
tool battery available to make it worth it. O.K I suppose if you are happy to change batteries every couple of hours or so.
raymo
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  #7  
Old 20-09-2021, 09:40 PM
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Logieberra (Logan)
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Software Bisque have been doing this for years. That said, their mounts use higher voltages… https://www.bisque.com/product/ego-b...power-adaptor/
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  #8  
Old 21-09-2021, 07:00 AM
JA
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Quote:
Originally Posted by Swagman105 View Post
I have plenty of 18v (Ozito) and 20v (Aldi) power tool batteries for my collection of power tools.
Wondering if anyone knows of a way to provide a 12v output from these batteries to power my telescope mount?
Also can anyone foresee any problems if an adaptor could be made or sourced?
Yes of course it can be done, but depending on how it's done it can be somewhat wasteful of the energy stored in the battery.

So let's say you want 12 volts DC at several amps. You may actually want more than 12V for optimum mount performance, but that's another story / possible risk.

The 12V supply to the mount should be regulated this can be done in a few ways, but 2 that come immediately to mind are

Linear Voltage Regulator
This a typically a 3pin electronic device (some 4) which requires a few volts (1.5-3V) higher of a input voltage than the required output voltage and can produce a very precise output voltage, either at a specific voltage depending on the regulator chosen or can be an adjustable, often 4 pin type. You can have a higher differential than the 1.5 to 3Volts, but it gets wasted as heat and too low a voltage differential causes loss of precision regulation (drop-out). Since these types of regulators regulate by shedding the voltage excess above the control voltage essentially as heat, they would be very wasteful energy wise in a remote power/battery application and DC-DC converters are probably preferable unless ultra low noise and precise regulation are also an important consideration (unlikley in the suggested application). They are ; however, excellent in low noise precision applications like audio, etc...Typical types are LM7905, 7912, 7915, etc.. with the last 2 digits (LM79XX) referring to the output voltage. These usually only have output currents of 1 to a few amps, but can be supplemented by external pass transistors for very high output 10-15Amps +...

DC-DC Converter
These DC to DC /buck converters as they are known, are far more efficient, especially in the presence of a large voltage differential between input and output when compared with linear types. They are however possibly more noisy and not as precise in regulation as the Linear types above ,but are available as ready built modules on the likes of eBay and possibly via electronics stores like Jaycar.

A typical 18V power tool battery is any where from 1.5 to 5 Ah with 4 and 5Ah types typical at the larger end, these equate to 72 to 90Wh respectively of energy storage. Using such an 18V battery with a linear voltage regulator one would probably only access 40-50% of that available energy as it would only properly regulate when the 18V battery was in the 20 Volt to 13/15 Volt range: i.e: fully charged at 20 or so Volts down to the drop-out voltage of the regulator anywhere between say 13 to 15V for a 12Volt regulator like an LM7912, whereas a DC-DC buck type converter would use far more of the available enerrgy whilst still maintaining regulation. The extent to which it does this depends on the specs for the module.

Even when you have all your ducks in a row with the right/best choice of DC-DC converter, how much can you expect from a typical 18V 4-5Ah battery? The mount draws something less than 1 amp tracking and ~<4 amps slewing as I recall from a video I once posted. I wrote about this once - I need to find that previous reference video to add further later.

This is not the video I was looking for, but has some answers regarding current draw (although no mount payload is specified), it shows 0.37A in rest state (not sure if this is when tracking or stopped) and just over 2A when slewing at highest speed (rate 9). On another occasion I did find a video on youtube (now no longer there unfortunately) which showed 3.48 A being drawn during full speed slewing on an unloaded AZ EQ6 mount.
If the 0.37A mentioned is the current draw whilst tracking or even perhaps a little higher, then your 18Volt 4 to 5Ah battery with DC-DC Buck converter with the odd bit of slewing should keep you going for a reasonable night session of a few hours.

Food for thought ....
It might be possible with some experimentation and with EQUALIZED batteries (equal voltage & equal condition/health) and some risk to parallel a few batteries for increased energy storage, but I'm not 100% sure how some of the Li-ion battery packs' control systems would like that. It might depend and be risky. In some situations a good battery might be degraded by a lower health battery it's paralleled with. Enter at your own risk on that one.

Best
JA

Last edited by JA; 21-09-2021 at 11:06 AM.
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  #9  
Old 21-09-2021, 07:09 AM
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I am using one of those on my bartelized dob to reduce voltage from 24V to 12 V:
https://www.ebay.com.au/itm/39336478...4AAOSwOTdg4Sfw


Also, this one or similar should be OK:
https://www.ebay.com.au/itm/31333993...MAAOSw9Flf1Dl6


Or this:
https://www.ebay.com.au/itm/32356016...oAAOSwmx9foQ3P
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Old 21-09-2021, 07:21 AM
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Sunfish (Ray)
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I use an 18v drill battery with an adjustable regulator , heat sink and fuse/indicator light which I have tuned to be below 15v and provides enough amps for a camera. I connected the wiring to the input clips of a 5v clip on USB module that you can buy for the drill battery. Works fine and saves one more power lead and transformer , also providing 5v at 1 or 2 amps if required.

Last edited by Sunfish; 21-09-2021 at 07:54 AM.
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  #11  
Old 21-09-2021, 07:39 AM
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I have done something similar to power portable speakers....
( same principle, different voltage :-) )

using a buck converter gives much more voltage stability than
what the scopes are designed for....
A "12v" lead acid or SLA battery can vary from 11 volts and close to 14 while still able to pump out lots of current....

So this solution is actually better...since you will be regulating
the output to be a constant voltage

At risk of repeating what others have said....

Steer away from Linear Voltage regulation - its simpler but wasteful of battery power. Any of the ones that Bojan suggested will work - i'd go for something with at least a 3A max output current to maintain voltage stability during slewing. (tracking uses bugger all, so don't worry about that bit) (and the 20 amp job is overkill)

There are 2 things that might fly up the ointment....

1.) the capacity of your drill batteries.
Some are not great for endurance - they are designed to supply
large current for a small time. (think how long you actually power a
drill). I'd suggest you need at least 4AH so that you don't have to swap
batteries halfway through the night.

2.) there will be little to no warning of impending battery flatness. SLA's slowly drop voltage as they fade, so you will start to see things like slewing causing the lights on the controller dimming. Lithium ion and the like, tend to pump out max until they don't. especially if you have good quality drill batteries with built in under voltage protection.

Overall though - it works well with my speakers, and i don't see why it
wouldn't work well with your scope.

P.S.

depending on your battery, you might be able to buy an adaptor to effect the physical connection -
something like this:

https://www.ebay.com.au/itm/40265968...CABEgLnAPD_BwE

I know dewalt and makita sell off the shelf adaptors to fit their batteries - note that these don't change the output voltage - you will still need a buck converter.
(some also have USB power out)

Last edited by sharkbite; 21-09-2021 at 08:59 AM.
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Old 22-09-2021, 08:15 AM
AdamJL
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Most of my cordless stuff is DeWalt so that’s great to hear they sell adapters. I have several 6Ah batteries (or 2Ah at 54V….that could be an issue!!) that could be used
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Old 22-09-2021, 08:52 AM
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mura_gadi (Steve)
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power levels

Hello,

You can get a variety of battery level indicators from $5 onwards for various battery types - 12v/LIPO etc. A cheap one displays 100/80/50/20% power levels on four LED's...

Easy to put one in your power circuit.



Steve
try Ebay/jaycar etc
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Old 22-09-2021, 09:13 AM
sharkbite
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Quote:
Originally Posted by AdamJL View Post
Most of my cordless stuff is DeWalt so that’s great to hear they sell adapters. I have several 6Ah batteries (or 2Ah at 54V….that could be an issue!!) that could be used
say hello to my little friend ;-)

https://www.ebay.com.au/itm/31363044...frcectupt=true

This thing is way overpowered for the job - but when you are talking about bucking 54 volts, this is the style you are looking at...

i did find a much smaller one that bucks 50v - but only at 1.5 amps, so while tracking would be ok,it
might struggle when slewing.
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Old 07-10-2021, 01:30 PM
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Swagman105 (Geoff)
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Ready made 18v to 12v power source for De Walt batteries

Hi all
Thanks for your input.
Have been doing a bit more browsing and while I couldn't find an adaptor for my Ozito and Aldi batteries, I did turn up the following power source designed for De Walt batteries. It has a 12v 5A output and two 5v USB outlets.
Made in China of course but any thoughts again.
Would really suit my idea of having a clip on easily charge battery system.
Attached Thumbnails
Click for full-size image (De Walt power source.jpg)
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  #16  
Old 14-10-2021, 11:49 AM
ausastronomer (John Bambury)
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This seems like a lot of work to save ~$30 on a battery that's designed to do the task required.

An 18v 5a cordless battery has 90 watts of stored energy, a 12v 7A SLA battery has 84 watts of stored energy and you can buy one of those for $24.99 delivered to your door and not have to fart around with odd power connections. Sometimes DIY is good, it can save money and achieve a better result. I don't think that applies here.
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