I got a message from another club member inquiring about these.
And through my own experience I felt it worthy to
post this up on the main boards just in case others get caught.
Be VERY careful with these 'PORTABLE' !
I am on my second in as many years.
They are totally unsuitable for scopes!!!
Even though some of the shops sell the likes,
if you ever run the Voltage down under then the battery is basically knackered.
If you have an astrotrac or the likes, (I think that comes with a 12volt battery power holder) then a good set of rechargeable batteries are the best thing.
Dave Lillis is the expert here...
maybe you could shed some light as to why these just dont work!
Portable power packs for scopes beware!
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Frank Ryan
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Dave Lillis
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This is a long post but is worth it for those wanting to power their systems remotely.
I've done abit of research on batteries to run the Obsessionator and have found a few points that might be useful here.
Usually these power packs use a standard sealed SLI (starter,lighter,ignition) lead acid battery (car and UPS batteries etc), if so, I wouldn't use this battery pack on your telescope system.
These SLI lead acid batteries they are not designed for long duration use but are used for high power short interval applications such as starting a car engine.
If you discharge more then 20% of its capacity, you can permanently damage the battery, if you go alot further you will definitely damage it, do this a number of times times and what you'll find is that the time it runs your scope in the field will become shorter and shorter and a time will soon come when it might not work at all.
In this case you'll need to replace the battery in the pack.
I used to go through a car battery every 8 months or so when I was using it to run my LX200, I couldn't figure out why, but now I know that I was draining them way beyond their ability to come back to life after a recharge attempt.
If you have a low power system like say an ETX, then get your self a cheap voltmeter and make sure that your SLI battery never runs below 12.5 volts (a 12volt battery is actually 12.65-12.7 volts), when it gets to that point turn the scope off.
For a higher power system, what you want is a reserve capacity battery such as a deep cycle battery a leisure battery or a marine battery (preference in that order). Its preferable to get one that isn't sealed so you can top up the electrolyte when needed. These batteries can discharge 70% and be recharged with no ill side effects.
One rule with all batteries is to recharge them ASAP after use, do not leave them lying around discharged.!!
LEISURE/DEEP-CYCLE BATTERIES
All the below applies to deepcycle/leisure/marine batteries only.
A word of advice!
Take care to calculate all your 12 volt items and their requirements before the initial purchase as a lightly used battery will eventually be the most economic.
Leisure batteries are designed to give a steady low amp discharge rather than meet the sudden high power demand required from a car battery to start an engine.
The life of a leisure battery is largely determined by the depth of the discharge cycle. We will say as an example that a leisure battery that is discharged each time by 15% of it's capacity may last for ten years. The same battery discharged by 30% of it's capacity will last for 8 years, 50% for 5 years, 75% for 3 years and possibly being discharged by 100% lasting only 1 year.
A 100 amp hour battery theoretically delivers 100 amps for 1 hour. Or 10 amps for 10 hours etc in theory, but in reality you should refrain from draining the battery more then half of its capacity for longevity reasons.
Power is amp x volts, so 100amps at 12v = 1200 watts, or 1,2kW 1.2kW for 1 hour is 1.2kWh.
Any form of heating element will cause a rapid drain on a battery, so know in advance its power requirements,
All batteries self discharge when not in use and leisure batteries will self discharge 7 to 10% monthly.
How to kill your battery dead!
1/. Uncontrolled Charging causes overheating and the releasing of hydrogen gas, dont recharge in a small confined room in the house (and here's looking at you Frank) unless you want to blow your house up
2/. Used too little (memory effects, looses amphour capacity, so cycle every 2 months)
3/. Stored discharged (sulphating, any flat battery left flat will be scrap within 3 months)
4/. Do not store on a cold surface as this rapidly increases the self discharge rate.
5/. Too much deep cycling (a good rule of thumb is not to go beyond 50% of the battery's endurance at worst)
Volts - State of charge
12.7V or over — 100%
12.5V — 75%
12.4V — 50%
12.2V — 25%
12V or under — Discharged
When battery manufacturers state that a battery has a capacity of 110 Ah they presume the battery will be operating where the ambient temperature is 25 degrees centigrade. For every 1 degree centigrade drop in temperature the battery capacity falls by 1%
The time required to recharge a leisure battery can be calculated as follows. The recharge time in hours equals the battery capacity in Ah, multiplied by the Depth of Discharge in %, multiplied by 0.8, multiplied by 1.5, divided by 100 times the charger current rating in Amps, plus one hour. For example, a 110 Ah battery, discharged to 50%, on a 10 Amp charger, would take about 7.6 Hours.
This is what I use to power the obsessionator.
http://www.irishastronomy.org/boards/vi ... 88&start=0
I've done abit of research on batteries to run the Obsessionator and have found a few points that might be useful here.
Usually these power packs use a standard sealed SLI (starter,lighter,ignition) lead acid battery (car and UPS batteries etc), if so, I wouldn't use this battery pack on your telescope system.
These SLI lead acid batteries they are not designed for long duration use but are used for high power short interval applications such as starting a car engine.
If you discharge more then 20% of its capacity, you can permanently damage the battery, if you go alot further you will definitely damage it, do this a number of times times and what you'll find is that the time it runs your scope in the field will become shorter and shorter and a time will soon come when it might not work at all.
In this case you'll need to replace the battery in the pack.
I used to go through a car battery every 8 months or so when I was using it to run my LX200, I couldn't figure out why, but now I know that I was draining them way beyond their ability to come back to life after a recharge attempt.
If you have a low power system like say an ETX, then get your self a cheap voltmeter and make sure that your SLI battery never runs below 12.5 volts (a 12volt battery is actually 12.65-12.7 volts), when it gets to that point turn the scope off.
For a higher power system, what you want is a reserve capacity battery such as a deep cycle battery a leisure battery or a marine battery (preference in that order). Its preferable to get one that isn't sealed so you can top up the electrolyte when needed. These batteries can discharge 70% and be recharged with no ill side effects.
One rule with all batteries is to recharge them ASAP after use, do not leave them lying around discharged.!!
LEISURE/DEEP-CYCLE BATTERIES
All the below applies to deepcycle/leisure/marine batteries only.
A word of advice!
Take care to calculate all your 12 volt items and their requirements before the initial purchase as a lightly used battery will eventually be the most economic.
Leisure batteries are designed to give a steady low amp discharge rather than meet the sudden high power demand required from a car battery to start an engine.
The life of a leisure battery is largely determined by the depth of the discharge cycle. We will say as an example that a leisure battery that is discharged each time by 15% of it's capacity may last for ten years. The same battery discharged by 30% of it's capacity will last for 8 years, 50% for 5 years, 75% for 3 years and possibly being discharged by 100% lasting only 1 year.
A 100 amp hour battery theoretically delivers 100 amps for 1 hour. Or 10 amps for 10 hours etc in theory, but in reality you should refrain from draining the battery more then half of its capacity for longevity reasons.
Power is amp x volts, so 100amps at 12v = 1200 watts, or 1,2kW 1.2kW for 1 hour is 1.2kWh.
Any form of heating element will cause a rapid drain on a battery, so know in advance its power requirements,
All batteries self discharge when not in use and leisure batteries will self discharge 7 to 10% monthly.
How to kill your battery dead!
1/. Uncontrolled Charging causes overheating and the releasing of hydrogen gas, dont recharge in a small confined room in the house (and here's looking at you Frank) unless you want to blow your house up
2/. Used too little (memory effects, looses amphour capacity, so cycle every 2 months)
3/. Stored discharged (sulphating, any flat battery left flat will be scrap within 3 months)
4/. Do not store on a cold surface as this rapidly increases the self discharge rate.
5/. Too much deep cycling (a good rule of thumb is not to go beyond 50% of the battery's endurance at worst)
Volts - State of charge
12.7V or over — 100%
12.5V — 75%
12.4V — 50%
12.2V — 25%
12V or under — Discharged
When battery manufacturers state that a battery has a capacity of 110 Ah they presume the battery will be operating where the ambient temperature is 25 degrees centigrade. For every 1 degree centigrade drop in temperature the battery capacity falls by 1%
The time required to recharge a leisure battery can be calculated as follows. The recharge time in hours equals the battery capacity in Ah, multiplied by the Depth of Discharge in %, multiplied by 0.8, multiplied by 1.5, divided by 100 times the charger current rating in Amps, plus one hour. For example, a 110 Ah battery, discharged to 50%, on a 10 Amp charger, would take about 7.6 Hours.
This is what I use to power the obsessionator.
http://www.irishastronomy.org/boards/vi ... 88&start=0
Last edited by Dave Lillis on Mon May 12, 2008 10:50 am, edited 3 times in total.
Dave L. on facebook, See my images in flickr
Carrying around my 20" obsession is going to kill me, but what a way to go.
Carrying around my 20" obsession is going to kill me, but what a way to go.
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Frank Ryan
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- Joined: Sun Aug 05, 2007 2:45 am
- Location: Ballycasey, Co. Clare
Very strange thing...
I had a Halfords battery pack that I thought was dead.
I was going to bring it back to get a refund but I said I'd
give it one more shot.
I charged it up for 48 hours,
plugged in the ETX and set it up, no trouble so far,
then I did several re alignments, set ups, slews, train drives,
anything I could think of and the battery still read 100%.
I left it set up and went to bed, the next morning it was still
working away.
I even plugged in my laptop and it worked.
This never worked before.
I charged it up again and it looks like its fine.
Very strange.
I had a Halfords battery pack that I thought was dead.
I was going to bring it back to get a refund but I said I'd
give it one more shot.
I charged it up for 48 hours,
plugged in the ETX and set it up, no trouble so far,
then I did several re alignments, set ups, slews, train drives,
anything I could think of and the battery still read 100%.
I left it set up and went to bed, the next morning it was still
working away.
I even plugged in my laptop and it worked.
This never worked before.
I charged it up again and it looks like its fine.
Very strange.
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Dave Lillis
- Posts: 2757
- Joined: Sun Aug 05, 2007 10:02 am
- Location: Limerick city
I guarantee you Frank the battery is someway damaged, but the fact that this deepcycle was done only once means that it might be only slightly damaged in that it might only hold 90% of its previously maximum charge.
I was kinda surprised to hear that it was completely gone after that night up on the hill,
Glad to hear its ok now.
I was kinda surprised to hear that it was completely gone after that night up on the hill,
Glad to hear its ok now.
Dave L. on facebook, See my images in flickr
Carrying around my 20" obsession is going to kill me, but what a way to go.
Carrying around my 20" obsession is going to kill me, but what a way to go.
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Frank Ryan
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Dave Lillis
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- Location: Limerick city
When I say 90%, I mean 90% of its amp hour power, not the voltage, in other words it'll last 90% of the time it used to last.
Dave L. on facebook, See my images in flickr
Carrying around my 20" obsession is going to kill me, but what a way to go.
Carrying around my 20" obsession is going to kill me, but what a way to go.
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Frank Ryan
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- Joined: Sun Aug 05, 2007 2:45 am
- Location: Ballycasey, Co. Clare
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Dave Lillis
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- Location: Limerick city
well,
for example, if it lasted 50 hours before, it'll last 45 hours now,
for example, if it lasted 50 hours before, it'll last 45 hours now,
Dave L. on facebook, See my images in flickr
Carrying around my 20" obsession is going to kill me, but what a way to go.
Carrying around my 20" obsession is going to kill me, but what a way to go.
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Frank Ryan
- Posts: 2980
- Joined: Sun Aug 05, 2007 2:45 am
- Location: Ballycasey, Co. Clare
Seriously,
ARE you a politician in secret!
Well, that pack used to last me for days straight so
I reckon unless I'm trying to jump start a JCB then it'll
be okay for the ETX.
After all my griping about that little bugger,
I still use it quite a lot and have to say,
if it stood up to my 'powder' like touch then that is a real plus for Meade!
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Dave Lillis
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- Location: Limerick city
ok, confusion reigns.
The autostar and power meter on the power pack are measuring voltage and nothing else.
How long the voltage stays high depends on the condition of the battery, a good one will last a long time while a bad one will drop in voltage quickly.
Dave L. on facebook, See my images in flickr
Carrying around my 20" obsession is going to kill me, but what a way to go.
Carrying around my 20" obsession is going to kill me, but what a way to go.
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John O'Mahony
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Frank
The trick with the powerpacks is to recharge them immediately after using them even if there is a green light on the indicator. The Halfords one I use for the CGE mount is 18 months old. The mount pulls 1-2 amps but even after a 6 hour session the battery still indicates a full charge. It takes 4-5 hours on the charger to top it back up. It has given me no trouble at all (so far).
My other unit I use for the LX10 and a kendrik heater. The LX10 only uses a few milliamps, the heater about 1.5 amps. I am going to invest in a small hairdryer for the 11" after the experience in the Burren-don't think a heater band would have coped with the moisture level that night. I'll run this off the back up powerpack.
The trick with the powerpacks is to recharge them immediately after using them even if there is a green light on the indicator. The Halfords one I use for the CGE mount is 18 months old. The mount pulls 1-2 amps but even after a 6 hour session the battery still indicates a full charge. It takes 4-5 hours on the charger to top it back up. It has given me no trouble at all (so far).
My other unit I use for the LX10 and a kendrik heater. The LX10 only uses a few milliamps, the heater about 1.5 amps. I am going to invest in a small hairdryer for the 11" after the experience in the Burren-don't think a heater band would have coped with the moisture level that night. I'll run this off the back up powerpack.