Using a power tool battery to power a telescope mount

[Swagman105]

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?

[AdamJL]

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

[leon]

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

[iborg]

Hi Leon


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


Philip

[iborg]

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-power-tool-battery-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/224367545063?_trkparms=ispr%3D1&hash=item343d590ae7:g:engAAOSw4sVgO lPR&amdata=enc%3AAQAGAAACoPYe5NmHp%252B 2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsSv tkx670Z0mbyfWqmxLFLYd7eIUe11yTGZDR4 MKrxFqaHyaLHDvoZbrDYrBqwghIMXqT8jX5 fhnJx7r0gJHn1hGIqXGRg5hv3wnqjtBK5gG GiezJcgQLDP6%252BU9YRVEU%252B6HO%25 2F6AGiCE7k%252BGM8M3fjh4i5aMdGpnGgf mrRm%252FtssD%252BxZa4LL2ynuetm10Ez %252BzTAXongN0YmOm9iVrZ8f6wBhg8fuww IDV0SkS62c%252BR0WpwhhG2KdeWOH%252B 2z1gUnmQaZoKDE8pFjSd1re8GkTElr%252F 3rLyBV7zKpxH3aeLJNZd1lXQuR2hQlOu4pB H%252BSyLfZ9w%252BiEU0PFtZ1th4B7ZsD Ib%252BULaYKD6yIuy0IPpyIEX1zh3YMQ7f Sh6I2l2KHTwI0kgRWvfqwG0AxmYBwUP3bpl dvKKmKy4CLC9WYQwOknB2ugozelxL2Z7WVn tDY7ONeUxIw2Sl3pytSqiSHXSpv5XhzVFdP g0HU4U7mvJUKpGjdkmJYh2xyxlM1vD%252F %252BZL0q57z26LI0d57kg%252BIToh3soU mznQ2ne5b1DCy1Mn4KIGK%252FueX4nnMV7 Gv5yqLSiaKc1apqWBx9qsDYbqxsbu27C1VM P2I1ainqWZjjFKV7XtQVhXR3YAFmtZiBTyk vda7r%252FfychWfklWB1YRrsFFZd5qfWmv cAouA0DjNbm2S%252FHGaZmqay0Pc8hOWqR 0w6JRHqjKNYnlmL2cIJgMqHWiuOGRjuj9oN DcDRrUYbGh%252ByCg%252FvV3CyXUGHuvP oSNrM23yAn%252BkOSa4IbXSR%252BZm%25 2F4Twh7cyHc7bUiPk%252Bvw0fkwN2Na26q rHlpRLy8s4aZ8wb6UIf6%252B5jTY6qc13n oKIu%252F1YBwwkw%253D%253D%7Campid% 3APL_CLK%7Cclp%3A2334524&frcectupt=true


https://www.jaycar.com.au/24v-to-12v-dc-voltage-converter-module/p/AA0238?pos=1&queryId=bfc8ea5a99ef645e027b0593c9e 74c07&sort=relevance

[raymo]

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

[Logieberra]

Software Bisque have been doing this for years. That said, their mounts use higher voltages… https://www.bisque.com/product/ego-battery-to-paramount-power-adaptor/

[JA]

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

[bojan]

I am using one of those on my bartelized dob to reduce voltage from 24V to 12 V:
https://www.ebay.com.au/itm/393364781626?hash=item5b965e3a3a:g: 824AAOSwOTdg4Sfw


Also, this one or similar should be OK:
https://www.ebay.com.au/itm/313339939365?hash=item48f4840a25:g: K6MAAOSw9Flf1Dl6


Or this:
https://www.ebay.com.au/itm/323560161389?hash=item4b55b0406d:g: VjoAAOSwmx9foQ3P

[Sunfish]

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.

[sharkbite]

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/402659684510?chn=ps&norover=1&mkevt=1&mkrid=705-139619-5960-0&mkcid=2&itemid=402659684510&targetid=1278935637969&device=c&mktype=pla&googleloc=1000286&poi=&campaignid=12502547493&mkgroupid=123090288695&rlsatarget=pla-1278935637969&abcId=9300512&merchantid=7364522&gclid=EAIaIQobChMImID0oOCO8wIVmJJmA h3BDglYEAQYBCABEgLnAPD_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)

[AdamJL]

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

[mura_gadi]

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

[sharkbite]

say hello to my little friend ;-)

https://www.ebay.com.au/itm/313630448719?hash=item4905d4dc4f:g: ZhkAAOSwdfFgljnm&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.

[Swagman105]

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.

[ausastronomer]

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 (https://www.ebay.com.au/itm/154109634370?_trkparms=amclksrc%3DI TM%26aid%3D1110006%26algo%3DHOMESPL ICE.SIM%26ao%3D1%26asc%3D2020121011 1452%26meid%3Dd5aecb6a26b34624af3e5 f173b22cde5%26pid%3D101196%26rk%3D5 %26rkt%3D12%26sd%3D124367518711%26i tm%3D154109634370%26pmt%3D1%26noa%3 D0%26pg%3D2047675%26algv%3DSimplAML v5PairwiseWebWithBBEV2bAndUBSourceD emotionWithUltimatelyBoughtOfCoview V1%26brand%3DPower&_trksid=p2047675.c101196.m2219&amdata=cksum%3A154109634370d5aecb6a 26b34624af3e5f173b22cde5%7Cenc%3AAQ AGAAACMHOalNSW1OC%252FMEi3waPkyJg9n GB8%252FhZMzYp1LUOJ%252BAuV%252FfCC AMiCETwJJb3GuTyzuo07YFCPutR4IuKRg3% 252B5JaHpDgKw0%252FhPQ8F2YieFOusAQ% 252BfDKKcdtWNdDnNl7aS4mm3rbY2IA7%25 2BOwCHfHKwWK6SqaVs1utaHcsokAzTNIedE VJQZ7DnlQH70quAS5lJub7rROSSChV7ST%2 52FVFdOHF8mHbopF3LGNgUXGR7bDoap0p%2 52FbrO5tgqNWAzpWvmThVsyb91jcCqG%252 BFsBQ8kDx%252BvOlo%252FDNFwlpuuc854 G7ce%252BQVY2T8m3I8pZWsBQ6eFTvTTrUy EfdC2xdFz1AdGUf4leR0QZWAE%252FvXXnZ mFOIFLZAGkBe9I8Iy6%252BwCwJ4oPQstyv OI%252FZ1kGrDQAf%252B1f%252FzrbA0Qt KsM7DRY%252Fx2WRo6DhWqPXu2ae4c9MyB8 GCuuV1%252FGLSquhQUJekagCgV5l5Tsud4 E7OyH1s5G%252BgfSTl%252Bvyx5bHSQnyr L1V%252BS1aMosMhS7QYY21hJAybW%252Fa l20f0EKMIULhFyrhaAdHshvWV1gGW456W9c nfn0vDZdqSccTM1%252Foer7j3uX3QrUtul N92kGRIh5MJuzi5KKAHIVnGjUB7e%252F5e MEILpwCPMKAZuz4T0k4ld0qvJ9rwOd6mSNB 3QSgMH8OZMa%252BO3KQNmRLLQTmQtsTfpo EmkCNCEXd9TtnIQCsj2zf1zm0gKro21ywDV hOy1AStyvpKy6mvQti2hprlIKr%7Campid% 3APL_CLK%7Cclp%3A2047675) 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.