20 replies to this topic

[kas20amc02]

  Hello everyone.  I needed some advice and although it is partially astronomy related, the other is a little tangential.  I have a new-to-me 16-inch Starmaster Dob.  It has tracking and go-to, which I have never had before.  My favorite astronomy sites do not have power and hence are Bortle 2.  I have always been an all-manual guy, but now that I need power, I am wondering what is my best option.

 

  The scope came with these two batteries (the black one says “12 V/8 Ah/20 hours” and the grey one says “12V/ 7 Amp/hr”).  I ran the scope for about 7 hours using both batteries last month at a site with power.  It seemed that the black battery ran out of juice sometime after midnight because the scope stopped slewing.  But the grey one let me observe until around 3 AM, when I packed up.  I have no idea how old the batteries are, conceivable a decade plus if they were purchased with the scope. 

 

A few questions:

1. Does slewing the scope take more power than tracking?
2.  If I bought a third battery, what would be my best option?
3.  If I bought a solar panel, could I charge my existing batteries or would they blow up?!?  I am considering a 100 Watt panel (which I could use at my house as well as while doing backwoods astronomy).  The manufacturer’s website says the solar panel works on gel cells, AGM cells, water-filled cells and lithium batteries.  https://www.amazon.c...nkCode=ogi&th=1

 

  I appreciate your help especially as this is sort of off topic.  But people on CN have been very patient with my questions and there are a lot of physics and engineering trained people on this forum to help us medical folks out.  Thanks in advance. 

~Karl

Attached Thumbnails

• 

[bigdob24]

Those are kind of the stock size batteries that came with StarMasters. 
‘Charge them up and put them on a battery load tester, if you don’t have one take them to a battery sales shop and they can test them.

I had 2 SM and just bought the biggest battery that would fit in the space without cause any problems in the scopes movement and would run the scope all night even with dew controls running too.

Just get a bigger new  battery and enjoy

[John Miele]

Were they fully charged? If so, then me thinks these batteries are on their last legs. I use an 18Ah battery to run my 14.5" Starmaster with servocat tracking and goto and a Nexus DSC  plus I run an EP dew heater strap at the same time. It can run the scope for 6-8 hours two nights in a row with no issue.

[kas20amc02]

I took them to a battery store when I first got the scope and they said they could not test them.  I used my volitmeter and got just over 12V on both of them. 

Any recommendations on type of battery?  e.g. gel?  

 

Is this one any good?  https://www.batterie.../12/wkdc12=14f2

 

 

 

Those are kind of the stock size batteries that came with StarMasters. 
‘Charge them up and put them on a battery load tester, if you don’t have one take them to a battery sales shop and they can test them.

I had 2 SM and just bought the biggest battery that would fit in the space without cause any problems in the scopes movement and would run the scope all night even with dew controls running too.

Just get a bigger new  battery and enjoy

Edited by kas20amc02, 27 September 2024 - 09:24 PM.

[kas20amc02]

Yes, they had both been charged earlier in the day.

 

 

Were they fully charged? If so, then me thinks these batteries are on their last legs. I use an 18Ah battery to run my 14.5" Starmaster with servocat tracking and goto and a Nexus DSC  plus I run an EP dew heater strap at the same time. It can run the scope for 6-8 hours two nights in a row with no issue.

[The Planetman]

This is what I'm running on my 24"....

 

https://dakotalithiu...v-10ah-battery/

 

Being a lithium battery, you'll need this charger:

 

https://dakotalithiu...attery-charger/

[csa/montana]

Moved to Equipment, as this forum is non-equipment.

[kas20amc02]

Thanks.  How long will your battery run the scope?  Did you pick lithium because it is lighter than lead or some other reason?

 

This is what I'm running on my 24"....

 

https://dakotalithiu...v-10ah-battery/

 

Being a lithium battery, you'll need this charger:

 

https://dakotalithiu...attery-charger/

Edited by kas20amc02, 28 September 2024 - 06:20 AM.

[astrohamp]

kas' : both your batteries are of the UB1280 battery type in physical size as 'Planetman points out.  If your OTA has compartments made for this size some DIY will be necessary for larger (physical) ones.  The trade up recommendation to LiFePO4 battery chemistry (and charger) is a good one, at a price of course and one I took a while back.

 

I have 6 of the PowerSonic batteries still in rotation (3 others on the dump shelf) but know that running them down to zero will shorten their useful life considerably.  So only about 4 Amp hours of power should be used before recharge so cycle life (number of use cycles) can be longer.  I've used this charger and a 50w solar panel in field with these lead batteries among other lead units.

 

I was able to find a 12Ah same size LiFePO4 battery a while back though no longer made.  They have however apparently packed even more capacity into the same space with this unit.  For me though I needed to stay airline friendly with 12Ah per battery (under 160 watt-hours each battery) in order to "carry on". 

A search can point to possible LiFePO4 battery alternatives though be mindful of physical dimensions if space requires.

 

As for solar charging I chose a Victron MPPT 75/15 unit with charge parameters set for LiFePO4 particulars rather then lead.  There is a newer 'Bluetooth included' unit as well.

Been using 100w Renogy rigid panels for >5yrs although HQST panels get good ratings.  Thought about making a "suitcase" from two 50w panels although my power needs are larger and OEM models getting better. Stay away from flexible panels from what the user info on them is saying.

[CA Curtis 17]

A fully charged healthy lead acid battery should read 12.6V to 12.9V depending whether it is a flooded or a sealed battery.  If you are reading 12V with no load the battery should be replaced.  I highly recommend a LiFePO4 battery as it is a much better choice in terms of cost and weight.  A lead acid battery should never be discharged below 50% whereas a LiFePO4 battery can safely be discharged 100% without damaging the cells inside.  The internal BMS shuts down the output once the internal cells reach their minimum recommended voltage.  Of course you will prolong the life of the battery by not fully discharging, but the typical full discharge cycle life of LiFePO4 batteries is >2000 which I think would be hard to do over the 10 year calendar life of the battery.

 

I highly recommend batteries from LiTime who makes quality batteries at a good price.  But there are lots of batteries, almost all of which are made in China, to choose from.  The US batteries like BattleBorn and Dakota Lithium are "Assembled" in the US from components made in Asia.  None of these battery suppliers is making their own lithium cells in the US at this time.  So don't necessarily think you are getting US made from these suppliers.  I have a Battleborn battery and I can attest is is well made - I even toured their factory floor to see their assembly and test processes which are very impressive.  But for my RV and for my astronomy applications I decided on LiTime due their price, as well as, their quality build.  You can find a wide range of form factors and capacities on their web site, as well as, on Amazon.  I have posted reviews of Battleborn, LiTime and Bioenno Power LIFePO4 batteries on my Youtube channel if you care to learn more.

 

When it comes to charging with a solar panel, you will not cause the battery to blow up but you do need to make sure that you solar charge controller is set to Lithium, which is easy to due and the charge controller instructions will guide you.  The Victron charge controller referenced above will work just fine.  That specific one is rate for no more than 75V and 15A which would be no problem with a single 200W or less panel.  If you plan to start adding panels you should be a model with a 100/50 rating.  I use one of the larger capacity Victron solar charge controllers in my RV.  But, for a single 100Ah or smaller LiFePO4 battery you do not need to pay that much.  There are many less expensive ones available on Amazon.  I use one of these when I recharge my 100Ah battery that I use for astronomy.  

 

If you want to see how to hook things up for charging with a solar panel and a solar charge controller take a look at this video I made when I reviewed the LiTime battery that I use out in the field.  At the 13min mark I discuss how to do this https://www.youtube....h?v=wIJPRiEm0VU

 

Good luck

Curtis

 

As far as charging 

[kas20amc02]

Thanks guys.  This is really helpful.  I also read some web articles comparing lithium batteries vs lead and it certainly seems that lithium makes the most sense for what I am doing.  Will look for a lithium battery that will fit in the slot (and that can be here before I leave on Tuesday!)

 

Glad to know a solar panel can charge it!

[kas20amc02]

After charging the batteries today for a few minutes to top them off, I get a reading of 13.02 and 13.0 for them.  I assume that is a pretty good number but I am still gun-shy after the batteries being entirely discharged the other night after 4 hours or so of astronomy, especially since I am doing a two night trip this week in an area without power.

~KaS

 

 

 

 

A fully charged healthy lead acid battery should read 12.6V to 12.9V depending whether it is a flooded or a sealed battery.  If you are reading 12V with no load the battery should be replaced.  I highly recommend a LiFePO4 battery as it is a much better choice in terms of cost and weight.  A lead acid battery should never be discharged below 50% whereas a LiFePO4 battery can safely be discharged 100% without damaging the cells inside.  The internal BMS shuts down the output once the internal cells reach their minimum recommended voltage.  Of course you will prolong the life of the battery by not fully discharging, but the typical full discharge cycle life of LiFePO4 batteries is >2000 which I think would be hard to do over the 10 year calendar life of the battery.

[kas20amc02]

Oh, lastly, I found an answer to my first question on an old forum. 

1. Does slewing the scope take more power than tracking?
Some people have measured power usage and slewing the scope takes about 1 amp/hr while tracking takes 0.45 amp/hr.  So slewing is about twice as energy intensive as tracking.

Edited by kas20amc02, 28 September 2024 - 04:48 PM.

[CA Curtis 17]

After charging the batteries today for a few minutes to top them off, I get a reading of 13.02 and 13.0 for them.  I assume that is a pretty good number but I am still gun-shy after the batteries being entirely discharged the other night after 4 hours or so of astronomy, especially since I am doing a two night trip this week in an area without power.

~KaS

A couple of things. First, to get an accurate reading one needs to let the battery rest for 30min or longer after charging. Second the voltage under load will be lower than with no load. Not saying you didn’t do these just want to be clear for anyone reading this

[briansalomon1]

I'm using a Blue Solar charge controller and a Netzero 100 watt portable panel. They are effective and built to last.

 

https://www.victrone...ollers/mppt7510

https://goalzero.com...hdPw5W_T3KoIboc

[kas20amc02]

I had no idea and I measured them immediately after disconnecting the charger.  Certainly no offense taken as I know very little about physics.  After letting them sit overnight, I got a reading of 12.97 and 12.87 V.  

 

I ordered a lithium battery as well.  As big as I could cram into the corner of the rocker box without moving the little bumpers.  20 Amp-hours as opposed to 7, so a big boost.  I plan on going to the Colorado Star Stare next summer and don't want to need to upgrade again for a 3+ day trip.  

 

~Karl

 

 

 

A couple of things. First, to get an accurate reading one needs to let the battery rest for 30min or longer after charging. Second the voltage under load will be lower than with no load. Not saying you didn’t do these just want to be clear for anyone reading this

[CA Curtis 17]

I had no idea and I measured them immediately after disconnecting the charger.  Certainly no offense taken as I know very little about physics.  After letting them sit overnight, I got a reading of 12.97 and 12.87 V.  

 

I ordered a lithium battery as well.  As big as I could cram into the corner of the rocker box without moving the little bumpers.  20 Amp-hours as opposed to 7, so a big boost.  I plan on going to the Colorado Star Stare next summer and don't want to need to upgrade again for a 3+ day trip.  

 

~Karl

Karl,

 

Now that makes sense since both of the batteries you showed are sealed.  Good luck with the Star Stare.  I have thought of traveling to check it out one day.  Maybe.

 

Best Regards,

Curtis

[BrendanF]

When the telescope would not slew, the battery was likely depleted and the voltage dropped enough to mean the motors would not go fast but there was enough voltage left to run the system normally.  The voltage from a battery can drop under high loads, so the battery is low, the extra load of slewing too much.  If your lead acid batteries will not maintain a ~13.2V after charge and something in the 12V range under load, they have likely expired.  Those little 7/8 Ah batteries are used for small computer UPS devices, and are easy to find and fairly cheap, but they do need to be maintained (just like a car battery--one can't leave them too long without charging).

 

I got this as a replacement for the lead acid batteries on my StarMaster:

 

https://www.bioennop...ed-green-case-1

 

It is the exact same size as those 7Ah original batteries (I couldn't find anything bigger that I thought would fit), and has a lot more useful power as you can easily use~ 80% of a LiFePO4 battery's capacity without reducing its life significantly (compared to ~50% for lead acid).  LiFePO4 batteries are great--lighter and more useful capacity, but they are more expensive, as you probably know by now.

 

These 'bare'  12V-class LiFePO4 batteries (with no built-in charge/voltage controllers) are easy to charge:  14.6V constant voltage.  A solar charge controller (which goes between the solar panel and the battery) needs to have a LiFePO4 setting (i.e. constant voltage) to match the battery voltage, but a simple voltage controller between the solar panel and the battery can also work.  If you google 'state of charge' for lead-acid or LiFePO4, you can find charts of measured voltage and charge state for info when and how much charge a battery needs. 

 

For my StarMaster with Skytracker GOTO, I have an 'inline watt meter' (I added matching connectors for my StarMaster) and have measured a usage of ~1.5 Ah for 4 hours of observing (no fans or dew heaters or other loads), so one of my 9Ah batteries would be good for at least 2 full nights.  If you have a voltmeter, you can also estimate usage via the 'state of charge' voltage, but it will be less precise.

[kas20amc02]

Well there were probably many ways to do this cheaper, but what can I say....I am from Texas and bigger is better.  As a bonus, it perfectly fits in between the rubber bumpers and the wood.  I figured it could also run dew heaters or other accessories in the future if needed. 

 

Thanks to everyone for their advice.

Attached Thumbnails

• 

[kas20amc02]

Another angle

Attached Thumbnails

• 

[astrohamp]

Happy to read you were able to trade up to a larger capacity battery (by 4x from 4Ah to 16Ah+ practical usable) that fit your space without issues.