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WHAT EXTERNAL LITHIUM ION BATTERY AMP / HOUR SPECS FOR ETX90

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#1 namor

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Posted 19 October 2019 - 10:01 PM

I have a 2007 ETX90 and was thinking of getting an external Lithium Ion battery . I need to know what a good portable AH rating battery to get. Is 6 AH good enough or should I go double digit AH like 10 AH plus 

 

I dont know the current Amp comsumption for the ETX90 SIDEREAL (tracking ) rate or the larger Amp  needed for the SLEW rate. Does anybody know these 2 Amp parameters please?

 

I know the ETX AC adapter #547 is 12 v at 2.5 A and has a male plug 5.5 mm OUTSIDE DIAMETER and a  2.5 INSIDE DIAMETER. and the RED lead from the battery is plug CENTER PIN with a fuse. Should I put a fuse on the black lead also?. And what size fuse Amp to get and should it be a fast blow fuse or ???

 

Does the battery have to have a steady 12 volts output or is there some voltage variation acceptance . I'm afraid anything under 12 volts going into the scopes circuit board may damage it 

 

Any ideas would be appreciated 

 

thanks

Gus 

Toronto Ontario Canada


Edited by namor, 19 October 2019 - 10:07 PM.


#2 namor

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Posted 19 October 2019 - 10:10 PM

This is the battery I was thinking of getting but its output voltage fluctuates from 9 volts to 12.6 Volts 

 

https://www.aliexpre...8b-4dfbe431d214



#3 junomike

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Posted 20 October 2019 - 03:38 PM

I reading it as the output Voltage is 9V - 12.6V depending on the needed voltage, not limited by the battery.

Cheap enough, that's for sure.



#4 EdIII

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Posted 21 October 2019 - 08:20 AM

I have a 2007 ETX90 and was thinking of getting an external Lithium Ion battery . I need to know what a good portable AH rating battery to get. Is 6 AH good enough or should I go double digit AH like 10 AH plus 

 

I dont know the current Amp comsumption for the ETX90 SIDEREAL (tracking ) rate or the larger Amp  needed for the SLEW rate. Does anybody know these 2 Amp parameters please?

 

I know the ETX AC adapter #547 is 12 v at 2.5 A and has a male plug 5.5 mm OUTSIDE DIAMETER and a  2.5 INSIDE DIAMETER. and the RED lead from the battery is plug CENTER PIN with a fuse. Should I put a fuse on the black lead also?. And what size fuse Amp to get and should it be a fast blow fuse or ???

 

Does the battery have to have a steady 12 volts output or is there some voltage variation acceptance . I'm afraid anything under 12 volts going into the scopes circuit board may damage it 

 

Any ideas would be appreciated 

 

thanks

Gus 

Toronto Ontario Canada

 

 

That battery will work for 4 or 5 hours, maybe more, depending on how much you are slewing. I did not check to see if it had the correct plug, but it appears you did. I don’t know the line voltage where you live, but that wall wart will not work in the US without a 120 volt adapter. 

 

I use a 2 amp standard fuse, but that was just what I had. Mine did not come with a fuse. No, you don’t need a second fuse. I have never bothered to measure the true amp draw.

 

I have seen mine run batteries down until it quit. Low voltage has never damaged my scope.

 

Ed


Edited by EdIII, 21 October 2019 - 08:23 AM.


#5 sg6

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Posted 23 October 2019 - 03:58 PM

A Li-ion battery will drop by about 5% from it's starting voltage and maintain that until it is approximately 80% discharged, then it drops off fairly rapidly.

Power-Tech

 

So if you start at 12v, you have in general terms 11.4v available for 80% of the time, but as your drain rate varies difficult to give a value. Although ETX's do not draw a lot when just tracking.

 

Will say I guess the battery starts higher then 12v, maybe 12.2 or 12.4.

So for the majority of the time voltage should not be a problem - well until that unknown 80% mark.

 

I can only suggest you assume 1 amp per hour, unless you intend to wander all around the sky all night. In which case 1.5 amp per hour.

 

So the battery should manage 0.8*6.8 = 5.5 hours(ish).

They should do a 9600mAh Li, I would suggest one of those. Same size, greater capacity - OK more cost.

One of those should last around 0.8*9.6 = 7.5 hours.

 

Personally I would consider the first OK for 4 hours and the second OK for 5 hours. Likely get a bit more but I tend to use worst case and then some more. You might get 5 hrs and 6 hrs. Just don't bank on it all the time.

 

Search out Talentcell, almost certainly the same internally, look nicer, and I have the option of another encased like Talentcel, half the cost and with a 5v output for phones etc - useful.

 

You will have to make a small converter from the battery lead to the ETX socket - different sizes. As it is center to center and so edge to edge no problem. I had to make one for mine.


Edited by sg6, 23 October 2019 - 04:02 PM.


#6 Taylor

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Posted 17 November 2019 - 10:57 PM

I use the 3000mah Talentcell for my ETX90-AT. It lasts longer than any observing session would ever last. 

 

I use a right angle adapter that converts the ETX input size to the standard 2.1mm plug, the adapter came in some power adapter kit that I luckily had laying around. 

I then use a 1 foot 2.1mm cord to connect it all together. 

 

Also has USB output if I want to plug in the iPad or the Meade Stella. 

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  • talentcell.jpg


#7 aeajr

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Posted 17 November 2019 - 11:47 PM

The ETX scopes might pull as much as 2 amps during slew but normally it is pulling 1 amp or less for tracking.   

 

That battery has more than enough capacity.   

 

What worries me is that it does not say whether the center is positive or negative or what size the plug is.   It has to match the ETX input port for size and polarity.   Most likely it is fine, but these are things you would want to check.



#8 Taylor

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Posted 18 November 2019 - 10:05 AM

The ETX scopes might pull as much as 2 amps during slew but normally it is pulling 1 amp or less for tracking.   

 

That battery has more than enough capacity.   

 

What worries me is that it does not say whether the center is positive or negative or what size the plug is.   It has to match the ETX input port for size and polarity.   Most likely it is fine, but these are things you would want to check.

Nothing to worry about. All the Talentcell batteries are center positive, outside negative and work with zero issues with the ETX. 

Just make sure to get a 5.5mm outside, 2.5mm inside adapter and you're good to go. Have run mine for hours and hours with zero problems. 



#9 Piet Le Roux

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Posted 25 November 2019 - 10:12 AM

I have more experience with the LX90 than the ETX90 but from my experience I will say don't  do it (I was hoping that the knowledgeable people on this site would have recommended that).The Meade scopes were designed to work from 8 1.5 volt dry cells or a 12V  lead acid battery. The voltage of these batteries only drop below 12V when the batteries are flat. Don't take any notice of the "battery Level : 100%" That will only show less than 100% around 10V  and by that time your drives will be having problems because they cannot supply the torque needed plus you did a "calibrate motor" at over 12V and now the encoders are having reading problems. Yes I agree below 12 Volt will not damage anything. I don't doubt that these batteries can supply the amps needed and have a lot of capacity but if the voltage is going to drop below 12 Volts they are not suitable.


Edited by Piet Le Roux, 25 November 2019 - 10:13 AM.


#10 aeajr

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Posted 25 November 2019 - 10:40 AM

Note that an LX200 mount is a MUCH bigger mount than an ETX and made to carry much greater loads so it will draw more power.  Many consider this an observatory class set-up. 

 

A note about capacity.

 

I work a lot with batteries for my electric airplanes and gliders.

 

Capacity, measured in Amp Hours, AH, or miliamp hours mAH tell you how much capacity the battery has.   However it tells you nothing about how fast it can deliver the power.   1 AH = 1000 mAH

 

Any rechargeable pack that is rated for 3AM or 3000 mAH, should be able to run your ETX.   That pack will be able to put out 1C at a minimum, which would be 3 amps.    Your ETX 90 will likely never pull 3 amps unless you are hanging cameras and stuff off of it and even then I doubt it will pull 3 amps.   The only way to really know is to put a meter on it and measure the draw, but these are my estimates.   Or call Meade and ask if they publish an amp draw for the mount.  I don't think they do. 

 

The higher the capacity rating of the pack, the higher its amp delivery capability.   So a 6000 mah or 6 AH pack that is rated for 1C can deliver 6 amps.  You don't need that much so the pack will not be working hard at all and will last longer.  Most lithium and NiCd packs can deliver more than the 1C rate. 

 

All batteries experience a voltage drop as they discharge.  That goes for AA dry cells, car batteries, jumper packs and the like. They all do this.  This is the basis of a capacity meter that some packs offer.  They read the voltage and know how much capacity is left.

 

As this is normal, the mount will be able to handle it as long as the pack isn't approaching discharge.  If you never use more than 50% of the capacity you will likely never experience a significant voltage drop and everything will be fine.  A Lithium pack is likely 12.4V when fully charged but will drop to about 11  for most of its useful capacity under a 1C load.  The mount will handle that just fine. 

 

If we assume that the scope is slewing 100% of the time, drawing about 2 amps then, if you run that for an hour you will use 2 amp hours of capacity or 2000 miliamp hours of capacity.    So you would want at least a 4 AH or 4000 mAH pack for a 1 hour session.

 

But normally we slew and then we track.  During tracking the amperage demand drops dramatically.  It may be less than .5 amps. If you tracked for 1 hour you could use .5AH or 500 mAH.

 

So, how long is your typical session, or how long do you want to plan for?   If  you use an average of 1 AH of capacity for every hour you run the mount then you want 2-3 AH of capacity for every hour you run the scope.

 

This does not take into account cameras, dew heaters or other accessories, only the mount.   If you put a lot of weight on the mount it will draw more.

 

If you are doing AP where tracking errors must be kept to an absolute minimum, then Multiply that by 4 so you never get down to more than 20% discharged which will minimize the voltage variation and lead to better tracking accuracy. 

 

So, going back to your original question.  Is a 6AH pack big enough?   I would say that should be good for about 1.5-2 hours in cold weather and 2-3 hours in warm weather.   Likely it will last longer than that, but I am talking about the minimum you can expect as every session will be different and you want to have plenty of extra capacity. 

 

If you can get a 10 AH, that is even better.  15 AH, even better. More capacity will never hurt you.


Edited by aeajr, 25 November 2019 - 10:54 AM.

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#11 Piet Le Roux

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Posted 25 November 2019 - 11:44 AM

Note that an LX200 mount is a MUCH bigger mount than an ETX and made to carry much greater loads so it will draw more power.  Many consider this an observatory class set-up. 

 

A note about capacity.

 

I work a lot with batteries for my electric airplanes and gliders.

 

Capacity, measured in Amp Hours, AH, or miliamp hours mAH tell you how much capacity the battery has.   However it tells you nothing about how fast it can deliver the power.   1 AH = 1000 mAH

 

Any rechargeable pack that is rated for 3AM or 3000 mAH, should be able to run your ETX.   That pack will be able to put out 1C at a minimum, which would be 3 amps.    Your ETX 90 will likely never pull 3 amps unless you are hanging cameras and stuff off of it and even then I doubt it will pull 3 amps.   The only way to really know is to put a meter on it and measure the draw, but these are my estimates.   Or call Meade and ask if they publish an amp draw for the mount.  I don't think they do. 

 

The higher the capacity rating of the pack, the higher its amp delivery capability.   So a 6000 mah or 6 AH pack that is rated for 1C can deliver 6 amps.  You don't need that much so the pack will not be working hard at all and will last longer.  Most lithium and NiCd packs can deliver more than the 1C rate. 

 

All batteries experience a voltage drop as they discharge.  That goes for AA dry cells, car batteries, jumper packs and the like. They all do this.  This is the basis of a capacity meter that some packs offer.  They read the voltage and know how much capacity is left.

 

As this is normal, the mount will be able to handle it as long as the pack isn't approaching discharge.  If you never use more than 50% of the capacity you will likely never experience a significant voltage drop and everything will be fine.  A Lithium pack is likely 12.4V when fully charged but will drop to about 11  for most of its useful capacity under a 1C load.  The mount will handle that just fine. 

 

If we assume that the scope is slewing 100% of the time, drawing about 2 amps then, if you run that for an hour you will use 2 amp hours of capacity or 2000 miliamp hours of capacity.    So you would want at least a 4 AH or 4000 mAH pack for a 1 hour session.

 

But normally we slew and then we track.  During tracking the amperage demand drops dramatically.  It may be less than .5 amps. If you tracked for 1 hour you could use .5AH or 500 mAH.

 

So, how long is your typical session, or how long do you want to plan for?   If  you use an average of 1 AH of capacity for every hour you run the mount then you want 2-3 AH of capacity for every hour you run the scope.

 

This does not take into account cameras, dew heaters or other accessories, only the mount.   If you put a lot of weight on the mount it will draw more.

 

If you are doing AP where tracking errors must be kept to an absolute minimum, then Multiply that by 4 so you never get down to more than 20% discharged which will minimize the voltage variation and lead to better tracking accuracy. 

 

So, going back to your original question.  Is a 6AH pack big enough?   I would say that should be good for about 1.5-2 hours in cold weather and 2-3 hours in warm weather.   Likely it will last longer than that, but I am talking about the minimum you can expect as every session will be different and you want to have plenty of extra capacity. 

 

If you can get a 10 AH, that is even better.  15 AH, even better. More capacity will never hurt you.

Ok I give up......



#12 SeymoreStars

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Posted 25 November 2019 - 11:51 AM

I have bought batteries from this company for use with HAM radio. They aren't cheap but the are great. If you buy one, buy their charger also.

 

https://www.bioennop...fepo4-batteries




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