Best value power tank?

[Spoon]

Hi everyone,

I need to get myself a power tank do I can go out to a dark sky site with my heq5. I will need to power the mount and a dew heater, so 2-4 cigar lighter socket ports. I've heard the maplins ones are good. Anyone got any good ideas?

Thanks

Cam

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[paul mc c]

A question i was going to ask my self.

[Spoon]

Convenient

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[Avocette]

A lot of people miss the point that a 12 Volt 'power tank' has a lead acid battery which provides a little over 13 V when fully charged but does not tolerate being discharged to much less than 12.8 V before it will start to 'suffer' and lose a significant number of potential lifetime recharge cycles. Normal car batteries spend most of their lives being charged by the alternator and are only required to discharge for short periods when starting the engine. Power tanks are similarly meant to be used to supplement a discharged car battery to get the engine started which then gets on charging the main battery again. Some lead acid batteries are constructed differently to permit a greater amount of discharge before they need recharging again. Caravan or 'leisure' batteries are more tolerant and the best lead acid batteries such as the very expensive Exide Maxxima (£150+) are designed for a 50% discharge (down to 12.3V) before there is any reduction in their 1000 recharge cycle life expectancy.

See if you can find values of current in Amps drawn by the mount and dew heaters. Take this figure and multiply by the number of hours you expect to be observing. Then multiply this number by 5 or even more if the weather is frosty to get an idea of the battery capacity you should choose. Don't skimp on a 7AH or even 17AH power tank and think you'll get away with it. You'll just end up buying another one soon enough.

I personally have a 55AH Exide Maxxima which weights 17kg. I check its state of discharge every so often with a home made sensitive voltmeter which has green LEDs every 0.1V from 13V down to 12.4V, an orange LED at 12.3V, and a red LED at 12.2V. I didn't make the voltmeter for astronomical purposes originally or else I would have used the LED colours in reverse. Even then, this battery only delivers 27.5 AH before I have to recharge it!

[ollypenrice]

I tried a couple of power tanks some years ago but they croaked in no time flat. I also have a friend in the car trade who said he'd stopped selling them because they were so unreliable. What you really need is a deep discharge battery (AKA leisure or boat battery) or perhaps the new kind of gel battery. I don't know about these, but basic car re-starters are not at all right for our astronomical purposes.

Olly

[Carina Lass]

Power tanks are not worth the money.

Go and buy a mobility scooter gel cell

They are available in several sizes and can take a discharge to 9 volts without detriment.

I use one of those for normal single evening s or a deep cycle marine battery 110ah for weekends away.

buy a good quality 6 stage charger to look after the battery.

[Carina Lass]

You can get a decent 110ah deep cycle battery from any chandlery for 85 quid

[Spoon]

You can get a decent 110ah deep cycle battery from any chandlery for 85 quid

Have you got a link to it? I can't seem to find it

Cam

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[AlistairHowie]

You can get a decent 110ah deep cycle battery from any chandlery for 85 quid

How heavy is it??  Possibly important for a mobile imager going to a dark site.  Have a look at Deben Tracer LiFePO4 batteries - expensive, but MUCH lighter, smaller, able to be discharged MUCH further than SLAs without any problem, nice constant voltage over 90% of their discharge curve, only lose 0.5% capacity per day, 1000+ charge/discharge cycles, inbuilt over charge/discharge/etc protection and very very safe  (unlike LiPos).  Just a shame they're so expensive ...

[andrew63]

I think i would go with tracer also, much more practical than old cell types.

Search Results - First Light Optics

andrew

[AlistairHowie]

That links to Tracer LiPos not LiFePO4 batteries. The lipos have a declining voltage over their discharge cycle (curves on the FLO site from memory) whereas the LiFePO4s hold their voltage much better at around 12.5v. I have a 24Ah LiFePO4 and their capacities go north of 40Ah, but boy are you going to have to pay for the likes of them. Grab a 24Ah cell for circa £250 ( extortionate, I know) but use 90% of its capacity for years and years to come without worry). Possibly cheaper in the long run ....

[Carina Lass]

Well, during summer I live on a canal boat so I can only tell you where they are in relation to the canals of Northern UK....

I got my deep cycle batteries near warwick.

But there's a load of places I've seen them the same price - they're heavy - but I'm a skinny chick and I changed 4 of them on my boat.

Setting up at home in Australia is a simple exercise as I leave my deep cycle battery in the obsy. Unless I'm going somewhere then I just drive my car to the obsy at the bottom of the garden or use the ride on mower to move it to the drive.

My wee gel cell is the size of a brick and will last 2 evenings. But not if I connect the lappy to it.

I also have mains to the obsy.

[Twisted Lip]

That links to Tracer LiPos not LiFePO4 batteries. The lipos have a declining voltage over their discharge cycle (curves on the FLO site from memory) whereas the LiFePO4s hold their voltage much better at around 12.5v. I have a 24Ah LiFePO4 and their capacities go north of 40Ah, but boy are you going to have to pay for the likes of them. Grab a 24Ah cell for circa £250 ( extortionate, I know) but use 90% of its capacity for years and years to come without worry). Possibly cheaper in the long run ....

Dumb question I know but how to you hook it up to the standard 'cigar output' style adapter everything in astro uses?

WIll

[perfrej]

Excellent posts all around - finally some good advice. While Lithium Polymer in various forms are he best, let's stick to Lead-Acid for a while. Only deep-cycle tolerant batteries should be considered, which spells Gel or AGM. The latter is, in a high quality version, capable of full discharge with little or no damage. My car has one for the consumables on-board and a standard car battery for engine start. As the thing sucks an unbelievable 65A with the ignition on, a cycle tolerant battery must be used, so they are supplied from the factory with 95Ah Varta AGM on the left hand side. Not to mention when the refredgerator is running

AGM basically does the same thing as gel, which is to make sure that the contact between the lead plates and the electrolyte is good. Gel, obviously, by using a gel form of the "liquid", AGM by using absorbant glass mats that use capillary force to keep it in place.

As usual, remember that anything you buy has to show at least 12.6 - 12.8V on the shelf in the store! Bring a DVM when buying batteries!

All the best,

Per

[Gina]

When I tested my NEQ6 mount for running voltage, I found it was unreliable or stopped working below 12.5v.  SW mounts are rated up to14v so lead acid batteries are ideal.  But the LIPO batteries that FLO sell discharge to 10.5v and only start just above 12v and I wouldn't have thought they would power a mount    Discharge curve.   Do some mounts work right down to 10.5v, I wonder...

[Earl]

I got a Leisuer Battery whcih I intend to use on a regular its just not intergrated into things yet fully, Dome control and cloud sensor currently run of it.

[AlistairHowie]

Re how to hook the batteries up, they come with proprietary connectors on the battery side ... t-bar with the LiFePO4 and a little used automotive connector on the LiPOs. You can see pics on the Deben website. The other end of these cables terminate in various plus including cigar socket, Anderson Powepoles, etc. In the past, Deben have made up 2 cigar sockets to one t-bar cable for me. If you need more than that, rather than daisy chaining y-connectors you probably need to build a distribution box. And if doing that, change everything to XLR plugs!

[Earl]

Ill be looking into a better distribution system in the new year, I have a plan

[Twisted Lip]

Earl - you're doing well to power all that equipment of the leisure battery, I'm impressed and it looks good.

Re how to hook the batteries up, they come with proprietary connectors on the battery side ... t-bar with the LiFePO4 and a little used automotive connector on the LiPOs. You can see pics on the Deben website. The other end of these cables terminate in various plus including cigar socket, Anderson Powepoles, etc. In the past, Deben have made up 2 cigar sockets to one t-bar cable for me. If you need more than that, rather than daisy chaining y-connectors you probably need to build a distribution box. And if doing that, change everything to XLR plugs!

Thanks chap, yes I actually had a look around the Deben website and saw in the accessories section, they had several adapters. Perhaps this is an option for the new year. 

I think really I need to be running things off the mains but I've avoided this for years because it seems to be so complicated!

Cheers

Will

[Physopto]

Hi all,

Just bought a Deben battery. 40Ah in a Pelicase. Now I'm broke, £650  . Thing is I use a lot of power for my rig in the field. I should now get almost the full current capacity out of the battery as opposed to half or less on really cold nights from the lead acid :pish  at present! LiFePo need a lot of careful thought. Have you ever seen a Lithium battery go on fire? scary to say the least. That is why I did not buy a cheap foreign make! Just a point though. I specified two connectors for the Pelicase, so that I can recharge whilst still being connected to the equipment. All a bit pointless if it drains before I'm finished imaging.

Derek

[Davey-T]

Those Deben batteries have shot up in price since I bought one, got the best of both worlds Maplin power pack chucked out all the innards and fitted Deben battery, easily runs everything all night in middle of winter and can carry it in one hand

Dave

[Twisted Lip]

Hi all,

Just bought a Deben battery. 40Ah in a Pelicase. Now I'm broke, £650  . Thing is I use a lot of power for my rig in the field. I should now get almost the full current capacity out of the battery as opposed to half or less on really cold nights from the lead acid :pish  at present! LiFePo need a lot of careful thought. Have you ever seen a Lithium battery go on fire? scary to say the least. That is why I did not buy a cheap foreign make! Just a point though. I specified two connectors for the Pelicase, so that I can recharge whilst still being connected to the equipment. All a bit pointless if it drains before I'm finished imaging.

Derek

Ouch! That's a serious payout! Did you get it for, them directly?

Will

[AlistairHowie]

£650 isn't cheap, but it's a better price than I thought you'd get!  Deben offer a 40Ah 12V LiFePO4 in a peli case for £790, but I see you can get the battery alone from them for £454 and then add in a charger and peli case separately.  I take it you went for the latter option?  Do you know what the difference is between what you ordered and their stock, £790 option?  Just wondering ...

[Physopto]

Ouch! That's a serious payout! Did you get it for, them directly?

Will

Hi Will,

No-ish, bought a 22 Ah tracer battery at Kielder from The Widescreen Center at the Saturday event. Trouble was that the young lad who sold it did not understand exactly what he was selling and did not let me know that the charger was only 1.65 Ah. It also could not be charged at the same time as being used. After talking to Simon on the telephone we agreed that it should be returned and exchanged for a 40 Ah unit in a Pelicase with 10 Ah charger. I stipulated at that time that it should be capable of being charged at the same time as being used. I had previously checked with Deben that this was possible. Unfortunately some one did not listen properly! I received a battery direct from Deben without the extra  charging connection. This was returned after talking to Simon. I then received the correct Item eventually. Simon stated on the telephone that he had been informed that all these batteries would in future include a second connection. But I definitely would check this if ordering one up. So in answer to your query not quite!

Still al that ends well

Derek

[Physopto]

£650 isn't cheap, but it's a better price than I thought you'd get!  Deben offer a 40Ah 12V LiFePO4 in a peli case for £790, but I see you can get the battery alone from them for £454 and then add in a charger and peli case separately.  I take it you went for the latter option?  Do you know what the difference is between what you ordered and their stock, £790 option?  Just wondering ...

Hi Alistair,

I would check the price you have seen. It is not correct as I see it. 40 Ah in Pelicase with the correct (LiFePo) 10 Ah charger ~£650. Not £790. You may be looking at a bare 80 Ah I don't know. It's a while since I looked at the site. If you are correct, it maybe because they are fitting the extra connection. If so a stupid increase. They will loose business. To get their 2 year guarantee it had to be done by them, so it was supplied all done. Just a note here though! The batteries from them all come with a small protection circuit. This protects against over heating etc., Lithium batteries of this size can be a bomb if not looked after properly, they are really nasty when provoked!!! That is why I bought from a well known firm with a reputation to protect. I really did not fancy one from some unknown Chinese import.

regards,

 Derek