PLEASE HELP 15V power supply Power Tank Recharger

[MRAPO]

A replacement 15V power supply for charging your 7Ah or 17Ah Celestron or

Sky-Watcher Power Tank where can i get one.

[JamesF]

http://www.ebay.co.uk/itm/NEW-15V-800mA-0-8A-AC-DC-Power-ac-adapter-Power-Supply-/230551510312#ht_2147wt_1083

perhaps?

I think it's possible to charge the 17Ah one by connecting a battery charger to the jump leads, too. I'd want to confirm that first though.

James

[JamesF]

The outside diameter of the output plug on that one looks right, btw (5.5mm), but I don't know about the pin diameter.

James

[SeedyF]

I use one of these chargers for my 16ah. It really does keep it much better charged than the old adapter. Keeps the battery in good condition too and wont overcharge. Not exactly cheap though.

You do indeed just attach the cables to the jump start leads on the powertank as James suggested.

http://www.amazon.co.uk/gp/aw/d/B004RADNCQ/ref=redir_mdp_mobile?redirect=true&ref_=oh_details_o05_s00_i00

[SeedyF]

http://www.amazon.co.uk/gp/aw/d/B004RADNCQ/ref=redir_mdp_mobile?redirect=true&ref_=oh_details_o05_s00_i00

Sorry copy and paste didnt quite work out there

[Carbon Brush]

Whatever charger you end up getting, check the voltage.

Do not end up with more than 13.8V on the battery for any significant time, or you will wreck it.

Just in case you don't have anything to measure voltege, a half decent multimeter costs less than a new battery, and is very useful elsewhere.

[faulksy]

Whatever charger you end up getting, check the voltage.

Do not end up with more than 13.8V on the battery for any significant time, or you will wreck it.

Just in case you don't have anything to measure voltege, a half decent multimeter costs less than a new battery, and is very useful elsewhere.

than less you have a battery conditioner type charger which will pulse charge up to 20 odd volts

[Carbon Brush]

Thanks Faulksy.

The key phrase here is 'significant time'.

Putting 20+ volts onto a gel battery is fine for a short time only and in conjunction with off-charge voltage measurement. Which is what 'conditioning' chargers do. The high voltage surge is a known method of attempting to recover batteries that have gone into deep discharge and gone high impedance. It is though better not to get into this situation in the first place.

Many power supplies on the replacement market are basic transformer/rectifier only types with of course awful regulation. If left on after the battery has charged, they will wreck it. I have a 12V car kit that I bought some years ago. In the very tiny small print is a recommendation to not charge for more than 8 hours. The included plug top charger outputs about 16V. Quite enough to wreck the battery if left on for a long time. A regulated 13.8V charger could be left on indefinitely without harm. Hence the recommendation to measure the charger voltage.

The same argument applies for any proposed handset/mount power supply.

I have a couple of power supplies at home that are described as 12V @ 3A. They sound ideal for running a mount. But at light load they give 19V - enough to fry a mount!

[Zakalwe]

Thanks Faulksy.

The key phrase here is 'significant time'.

Putting 20+ volts onto a gel battery is fine for a short time only and in conjunction with off-charge voltage measurement. Which is what 'conditioning' chargers do. The high voltage surge is a known method of attempting to recover batteries that have gone into deep discharge and gone high impedance. It is though better not to get into this situation in the first place.

Many power supplies on the replacement market are basic transformer/rectifier only types with of course awful regulation. If left on after the battery has charged, they will wreck it. I have a 12V car kit that I bought some years ago. In the very tiny small print is a recommendation to not charge for more than 8 hours. The included plug top charger outputs about 16V. Quite enough to wreck the battery if left on for a long time. A regulated 13.8V charger could be left on indefinitely without harm. Hence the recommendation to measure the charger voltage.

The same argument applies for any proposed handset/mount power supply.

I have a couple of power supplies at home that are described as 12V @ 3A. They sound ideal for running a mount. But at light load they give 19V - enough to fry a mount!

Get a proper intelligent conditioning battery charger, such as one made by CTek or Optimate. They can be left connected for months on end (connect them to the jump lead terminals on the power pack) I use them on my motorbikes and they are permanently on charge. The intelligent chargers will periodically test the battery and supply exactly what is needed to keep the battery in perfect condition. As you have said, allowing a normal lead/acid battery to deep discharge will significantly weaken, if not totally destroy it. Leisure batteries can be deep discharged, but an intelligent chager will keep them tip-top.

Do not bother will small "wall-wart" type power supplies. They won't supply anywhere enough current to charge the battery in a reasonable length of time, and as they have no "intelligence" they will continue to supply current even if the battery is charged. This will also ruin a lead/acid battery.

[Zakalwe]

Whatever charger you end up getting, check the voltage.

Do not end up with more than 13.8V on the battery for any significant time, or you will wreck it.

Just in case you don't have anything to measure voltege, a half decent multimeter costs less than a new battery, and is very useful elsewhere.

There's no point in doing this with an intelligent charger, as it will vary its voltage and current depending on whats connected to it.

[Carbon Brush]

I see little point in spending £30+ on an intelligent charger when a £10 regulated power supply will do the job.

The main benefit of the intelligent charger is to try to recover a damaged battery. This is though often fruitless.

A simple regulated supply of 13.2V to 13.8V will keep any lead acid battery charged, without complication, and can be left connected indefinitely.

I would not use the fleabay item as it stands. It is 15V output.

Two diodes in series with the ouptut would make it more suitable.

I would always measure the voltage from any power supply before use. Hence the meter recommendation.

The recharge time from (the correct type) of simple regulated plug top supply will be reasonable because of the charge characteristics of lead acid battereis.

The multimeter can be used for other tasks so is not wasted money.

For similar cost to the intelligent charger, you can buy a fixed 13.8V 5A bench top supply intended for CB radios and the like. A useful piece of kit for powering other items (including dew heaters) in your astro collection.

There are lots of threads on SGL about people having (mostly avoidable) problems with gel batteries.

Many resulting from a failure to understanding charging requirements.

I had hoped to be able to contribute something to help reduce their occurence. Apparently not.

I have been designing electronic equipment for 30+ years. More than a little of this has included battery back up of one sort or another. The battery charging and monitoring circuits being part of the design. Not relying on buying something from China and hoping it is fit for purpose.

If you want to know more about gel lead acid batteries, the Yuasa and Sonnenschein sites (battery manufacturers) are good start points.

My last post on this thread.

[SeedyF]

I see little point in spending £30+ on an intelligent charger when a £10 regulated power supply will do the job.

The main benefit of the intelligent charger is to try to recover a damaged battery. This is though often fruitless.

A simple regulated supply of 13.2V to 13.8V will keep any lead acid battery charged, without complication, and can be left connected indefinitely.

I would not use the fleabay item as it stands. It is 15V output.

Two diodes in series with the ouptut would make it more suitable.

I would always measure the voltage from any power supply before use. Hence the meter recommendation.

The recharge time from (the correct type) of simple regulated plug top supply will be reasonable because of the charge characteristics of lead acid battereis.

The multimeter can be used for other tasks so is not wasted money.

For similar cost to the intelligent charger, you can buy a fixed 13.8V 5A bench top supply intended for CB radios and the like. A useful piece of kit for powering other items (including dew heaters) in your astro collection.

There are lots of threads on SGL about people having (mostly avoidable) problems with gel batteries.

Many resulting from a failure to understanding charging requirements.

I had hoped to be able to contribute something to help reduce their occurence. Apparently not.

I have been designing electronic equipment for 30+ years. More than a little of this has included battery back up of one sort or another. The battery charging and monitoring circuits being part of the design. Not relying on buying something from China and hoping it is fit for purpose.

If you want to know more about gel lead acid batteries, the Yuasa and Sonnenschein sites (battery manufacturers) are good start points.

My last post on this thread.

Dude - take it easy - it's just a discussion. If I didn't already own a CTEK I'd thinking "there is some useful advice about alternatives"

[JamesF]

There's also a replacement power supply here:

http://astronomia.co.uk/index.php/power-tank-replacement-power-supply.html

I don't think there's an issue with using a 15V supply in this instance. It's what gets supplied by the manufacturer and AFAIR from taking one apart the entire 15V doesn't just get dropped across the battery to charge it either, though I was surprised at the design. For example, I don't recall that the 3V, 6V and 9V power outputs are regulated, but just use diodes chained together to drop the voltage.

James