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Calling Power Supply Experts: Is this battery sufficient to power an EQ6 and 2 Atik CCD cameras?

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#1 jag32

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Posted 21 October 2018 - 10:35 AM

Is this battery sufficient for powering an EQ6 mount and 2 Atik CCD cameras for 6-7 hours?  https://www.amazon.c...h/dp/B007Q2CUD0

 

The 35ah version.

 

 



#2 Nebula27

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Posted 21 October 2018 - 10:38 AM

Do you know the power consumption of the Atik cameras? I am pretty sure it will be sufficient.

#3 mvas

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Posted 21 October 2018 - 10:43 AM

Is this battery sufficient for powering an EQ6 mount and 2 Atik CCD cameras for 6-7 hours?  https://www.amazon.c...h/dp/B007Q2CUD0

 

The 35ah version.

Estimates ...

 

17mAh useable  / 2 total amps used = 8-9 hours

17mAh useable  / 3 total amps used = 6-7 hours

17mAh useable  / 4 total amps used = 4-5 hours

17mAh useable  / 5 total amps used = 3-4 hours

 

 

Total Load Amps = EQ6 amps + Atik #1 amps + Atik #2 amps 

Once you determine your actual TOTAL load in AMPS then you can do the simple math, as shown above.

 

Put Anti-Dew Heaters on separate battery?


Edited by mvas, 21 October 2018 - 10:47 AM.

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#4 RaulTheRat

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Posted 21 October 2018 - 11:01 AM

Should do, EQ-6 will average about an amp, more when slewing but mostly just tracking. Cameras call them an amp each which is probably an overestimate and you've got 3 amps total load, so 7 hours would use 21Ah or about 2/3 of the total capacity which is a good place to stop if you want the battery to last.

#5 jag32

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Posted 21 October 2018 - 11:08 AM

Estimates ...

 

17mAh useable  / 2 total amps used = 8-9 hours

17mAh useable  / 3 total amps used = 6-7 hours

17mAh useable  / 4 total amps used = 4-5 hours

17mAh useable  / 5 total amps used = 3-4 hours

 

 

Total Load Amps = EQ6 amps + Atik #1 amps + Atik #2 amps 

Once you determine your actual TOTAL load in AMPS then you can do the simple math, as shown above.

 

Put Anti-Dew Heaters on separate battery?

Here is the power consumption i've found:

 

EQ6 Mount:  2 amps (Slewing); 1 amp (Tracking)

Atik camera #1:  0.8 amps

Atik camera #2:  0.6 amps

 

So assuming worst case scenario 2 amps while slewing, it calculates as 3.4 whereas using 1 amp for tracking, the total is 2.2.  So I figure the realistic amount would be somewhere between 2.5 and 3.2 depending on how much slewing I do.  So based on this, it looks like i'm in the 6-8 hour range.  Is this correct?  Also, you say 17mAh is useable, is that the rule of thumb where essentially only 50% is useable?  



#6 pkrallis

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Posted 21 October 2018 - 11:08 AM

I've run my EQ6  and a laptop with a 2d display 4 to 5 hours a night for 2 nights on a 35 AH battery  You should be good.



#7 jag32

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Posted 21 October 2018 - 11:12 AM

I've run my EQ6  and a laptop with a 2d display 4 to 5 hours a night for 2 nights on a 35 AH battery  You should be good.

Peter, thanks--quick question:  how did you connect your laptop to the 12v battery?  What adaptor/connector did you use?



#8 scadvice

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Posted 21 October 2018 - 11:20 AM

Never let your battery go below 50% of charge. This means that you have about 17 AH to work with. The first reason to limit to 50% is it will kill the battery life going below that. The second reason is some mounts and equipment do not perform at the voltage available below that 12.06 volts and can fail.This chart below to gives you the discharge profile for your batteries and the voltage drop with discharge.

 

State of Charge- 12 Volt battery- Volts per Cell

100%                       12.7                 2.12
90%                         12.5                 2.08
80%                         12.42               2.07
70%                         12.32               2.05
60%                         12.20               2.03
50%                         12.06               2.01
40%                         11.9                 1.98
30%                         11.75               1.96
20%                         11.58               1.93
10%                         11.31               1.89

0                              10.5                 1.75

 

All plugs/connections should be fused. Some experts suggest using two batteries in parallel with a step down transformer to assure the voltage says more constant over the use cycle. Also there are little adjustable voltage monitors out there that will shut down the system (or alarm) if the output voltage drops below an acceptable range. 


Edited by scadvice, 21 October 2018 - 11:37 AM.


#9 scadvice

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Posted 21 October 2018 - 11:37 AM

Peter, thanks--quick question:  how did you connect your laptop to the 12v battery?  What adaptor/connector did you use?

 

Sorry, missed this one above. Computers use a 19 -20 volt dc charging system and are power hungry... something like 2.5 to 3 amps  depending on the computer. So you have two problems the first is you need a Converter Regulator to bump the 12 volts up to 19 or 20 volts

 

https://www.amazon.c...0?ie=UTF8&psc=1

 

Second, since they are a power hog more battery storage say at least an other usable 17AH .  

 

You can get away with less but at the risk of short battery life.



#10 mvas

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Posted 21 October 2018 - 02:30 PM

Never let your battery go below 50% of charge. This means that you have about 17 AH to work with. The first reason to limit to 50% is it will kill the battery life going below that. The second reason is some mounts and equipment do not perform at the voltage available below that 12.06 volts and can fail.This chart below to gives you the discharge profile for your batteries and the voltage drop with discharge.

 

State of Charge- 12 Volt battery- Volts per Cell

100%                       12.7                 2.12
90%                         12.5                 2.08
80%                         12.42               2.07
70%                         12.32               2.05
60%                         12.20               2.03
50%                         12.06               2.01
40%                         11.9                 1.98
30%                         11.75               1.96
20%                         11.58               1.93
10%                         11.31               1.89

0                              10.5                 1.75

 

All plugs/connections should be fused. Some experts suggest using two batteries in parallel with a step down transformer to assure the voltage says more constant over the use cycle. Also there are little adjustable voltage monitors out there that will shut down the system (or alarm) if the output voltage drops below an acceptable range. 

There is no such thing as "Never discharge below 50% or you will kill the battery life" - this is pure nonsense.

You can discharge the SLA battery below 50%, without any damage to the battery.

50% is just a "rule-of-thumb" (an estimate) to maximize depth-of-discharge vs max cycles vs battery life in years.

I don't know who started this "Discharging below 50%, kills the battery" rumor but it needs to stop.

 

Just recharge the Lead Acid batteries as soon as possible, after each use.

Do not let them sit discharged, because the lead-sulfate will harden permanently, which permanently reduces capacity

 

Also, with a Lead Acid Battery ... "If you don't use, you will lose it" because the old age clock is ticking from day #1 - so use it within reason and ignore the rumors.


Edited by mvas, 21 October 2018 - 02:30 PM.


#11 WadeH237

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Posted 21 October 2018 - 02:56 PM

There is no such thing as "Never discharge below 50% or you will kill the battery life" - this is pure nonsense.

You can discharge the SLA battery below 50%, without any damage to the battery.

Uh, no.  This is really bad advice.

 

Here is the datasheet for a UB12350 35ah AGM battery.

 

If you look at the chart entitled "Cycle Life vs Depth of Discharge", you will see that the battery is rated for just over 200 cycles if you fully discharge it.  It is rated for 500 cycles at 50% discharge, and 1200 cycles at 30% discharge.

 

If anything, you should use less than 50% of its rated capacity if you want to prolong the life.


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#12 pkrallis

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Posted 21 October 2018 - 03:17 PM

Jag 32,

 

I used to use a low power (if memory serves 60 watt inverter) but now I use a 12VDC to laptop power supply I think from eBay but also available on Amazon in several models. I connect with cigarette lighter extension units available at any auto store.



#13 scadvice

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Posted 21 October 2018 - 03:33 PM

Anything I post is 'as I see it' based on information I've found. Here is the information I based my conclusions on:

 

https://batteryunive..._acid_batteries

 

Which led me to this list...

 

https://batteryunive...to_charge_table

 

 

and this one...

 

https://batteryunive...t_battery_table

 

mvas, please give me some links to you statements as I'm always open to learn something new and different that may change my opinion.

 

Maybe I should have used 'shouldn't' as opposed to 'never' and 'could reduce' as opposed to 'kill'??hmm.gif  



#14 RaulTheRat

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Posted 21 October 2018 - 04:00 PM

Of course it's an individual choice to some extent, but I'd be quite happy going down to 70% depth of discharge (ie. 30% remaining charge) on a smallish, not particularly expensive battery like a 35ah SLA or gel cell that is maybe $100 or thereabouts. I think below that you're really into diminishing returns where you're getting 10% more utility and really beating the battery up, but stopping at 50% when say 300 cycles at 70% d.o.d is probably still going to last you a number of years seems overly conservative.

Now if we were talking about a few KWh worth of batteries in a motorhome or similar with a replacement cost of thousands, then yeah, I'd be more gentle on them.

Again, it's an individual decision, but I do think the point where long term battery life Vs usable charge "drops off a cliff" is more like discharging below 30% than 50.

You've also got to ask yourself what's important - if I needed for example about 25Ah to get through a session, I could either carry a 35Ah battery, discharge it to 30% and replace it every couple of years for ~€100, or I could carry 50Ah, discharge to 50% and it might last for example 4 years and cost €150 to replace.

Then the 35Ah costs me €50 per year, the 50Ah costs €37.50, but I'll pay the extra not to have to carry the heavier battery. The other way to look at that is that the 35Ah doing 200 cycles costs €0.50 per cycle and the 50Ah doing 400 cycles costs €0.37 per cycle, so each time I carry the lighter smaller battery it costs me €0.13 to do so.

Edited by RaulTheRat, 21 October 2018 - 04:12 PM.


#15 scadvice

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Posted 21 October 2018 - 04:36 PM

TheRat makes a point. I believe most of us shorten battery life also by forgetting top them off every few weeks when not being used or in a reasonable period after a night of AP'n. Thinking of that, my power pack needs to be topped off....step.gif



#16 Phil Sherman

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Posted 21 October 2018 - 08:09 PM

Is this battery sufficient for powering an EQ6 mount and 2 Atik CCD cameras for 6-7 hours?  https://www.amazon.c...h/dp/B007Q2CUD0

 

The 35ah version.

The one thing that I didn't see in any of the prior posts is that the item referenced is NOT a 35AH 12V battery! It's a pair of 35AH 12V batteries. If you follow the 50% discharge rule, that's 35AH available to run equipment.

 

500 cycles at 50% discharge could be considered the equivalent of 250 cycles at full discharge. Since the full discharge rating of the battery is 200 cycles, using it to 50% of charge gains you 25% additional life. The extra life needs to be weighed against the difficulties of doubling the battery weight. If you use the battery once a week (almost) every week, the difference is a battery lasting four vs five years. At twice a month use, it's eight vs 10 years. For weekly use, the difference in cost of ownership is around $3/year. You need to decide if this savings is worth carrying a battery twice as heavy.

 

My personal choice; run the battery down more than 50% and carry less weight. $3 is less than the cost of a fast food lunch.



#17 jag32

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Posted 21 October 2018 - 11:14 PM

The one thing that I didn't see in any of the prior posts is that the item referenced is NOT a 35AH 12V battery! It's a pair of 35AH 12V batteries. If you follow the 50% discharge rule, that's 35AH available to run equipment.

 

500 cycles at 50% discharge could be considered the equivalent of 250 cycles at full discharge. Since the full discharge rating of the battery is 200 cycles, using it to 50% of charge gains you 25% additional life. The extra life needs to be weighed against the difficulties of doubling the battery weight. If you use the battery once a week (almost) every week, the difference is a battery lasting four vs five years. At twice a month use, it's eight vs 10 years. For weekly use, the difference in cost of ownership is around $3/year. You need to decide if this savings is worth carrying a battery twice as heavy.

 

My personal choice; run the battery down more than 50% and carry less weight. $3 is less than the cost of a fast food lunch.

Just to clarify, I had no idea the offering in the link was selling two of the same battery.  I would only be using one at a time.  Sorry for the confusion.




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