Another DIY Portable Power Thread

[John K]

Guys,

I am sure this has been covered before but cannot find the thread. Wanting to get myself some serious long lasting portable power going.

I have a Lumenera SxyNyx camera, newish Dell Laptop (19.5v 5 amps - I'll use this with an cigarette 12v to 20v inverter) and obviouly my scope (12.5" with a Losmandy Drive).

The Celestron Powertank 17 that I have is now totally inadequate - in fact I ended up accidently draining the battery on it so the internal battery now needs replacing - a battery from Jaycar will cost me $70.00

So, if I want to get to around 50amps with a re-chargebale power set up what are my options?

Whilst at Jaycar I looked at a few items I can put together:

- 26amp 12 v Deep Cycle Gel Battery $139 (I would get 2 of these and link them in a bank configuration)

- Trickle charger $50

- Voltage Gauge Unit $9.00

- Ciggarette Lighter Adaptors, Splitters etc around $30.00


So estimated cost is around $350.00


My idea is to simply wire all this stuff together and put it all in an old ESKY that I have.


Thoughts? Suggestions? Are there any other threads on this topic?


John K.

[lacad01 (Adam)]

Hi John, you might want to check out these threads:
http://www.iceinspace.com.au/forum/s...ad.php?t=46306
http://www.iceinspace.com.au/forum/s...ad.php?t=46574
For my 2 cents worth, you should try and avoid using an inverter to supply power for your laptop, they're very ineffecient. Mobs like Jaycar & DSE sell 12V laptop power supplies.
If you can work out your total consumption in Watts coupled with hours of use then divide by 12 will give the capacity of battery in Amp hours, probably want to add 30% onto that as safety margin: e.g.
(watts x usage(hours) = Watt hours) / 12 = Amp hours
cheers

[Jeff]

Hi John,

I agree with Adam's suggestion that you consider avoiding an inverter for the laptop. They work well, but tend to guzzle the juice.

I have a current model Dell laptop which I power remotely using a DC-DC converter from JayCar (DC 120-003, 12v to 18-20v). The only time consuming part was finding a power cable/plug to suit the DC input socket on the laptop. I eventually located and purchased a suitable cable/plug (PL7450) at www.laptopjacks.com.

[Starkler (Geoff)]

Originally Posted by Jeff

Hi John,

I agree with Adam's suggestion that you consider avoiding an inverter for the laptop. They work well, but tend to guzzle the juice.

Indeed I flattened the car battery after 2 days at Snake valley camp using one.

I have a current model Dell laptop which I power remotely using a DC-DC converter from JayCar (DC 120-003, 12v to 18-20v). The only time consuming part was finding a power cable/plug to suit the DC input socket on the laptop. I eventually located and purchased a suitable cable/plug (PL7450) at www.laptopjacks.com.

Laptops suck heaps of juice so best to set it in low power everything mode when using it this way. Being powered externally it will think its plugged into mains power.

[mswhin63 (Malcolm)]

Don't put it in an esky. Even though they are sealed lead acid batteries they still vent. Charger still heats up so you esky may start to melt.

Need ventilation as well.

[Rod]

Hi John,

I have used the cheap universal DC car chargers from ebay to power several different types of laptops. They connect to a 12 volt power supply with a cigarette lighter adapter and come with several circle power plugs for various laptops.

Rod.

[John K]

Originally Posted by lacad01

Hi John, you might want to check out these threads:
http://www.iceinspace.com.au/forum/s...ad.php?t=46306
http://www.iceinspace.com.au/forum/s...ad.php?t=46574
For my 2 cents worth, you should try and avoid using an inverter to supply power for your laptop, they're very ineffecient. Mobs like Jaycar & DSE sell 12V laptop power supplies.
If you can work out your total consumption in Watts coupled with hours of use then divide by 12 will give the capacity of battery in Amp hours, probably want to add 30% onto that as safety margin: e.g.
(watts x usage(hours) = Watt hours) / 12 = Amp hours
cheers

Holy cow. Based on that formula I get:

Laptop: 19.5v; 4.62 amps and 90 watts
it's a Dell Precision M4300
http://www.level8technology.com/serv...zmap=DL18-2598

http://www.level8technology.com/serv...p=AC-DL02-2767

Lumenera Skynyx: 5v 500ma and 2.5 watts

Mount Drive: 12v 500ma and 13 watts

Total Watts: 105.5 x 12 hours = 1266 watts plus 30% = 1645.8 divided by 12 equals 137.15 amps!!!

I think I'll need a portable generator. The problems is the laptop. It's a hungry machine!!

Does that sound right to you guys?

[erick (Eric)]

John, it's 137.15 AmpHours - a bit different to Amps!

Are you sure that your mount drive is as low as 500mA - what about when it is slewing?

No dew heating??

Fundamentally you need a power supply that will 1) comfortably deliver the maximum Amps that is required at any one time (lappie chunking flat out and drive slewing and camera "clicking" and downloading), and then 2) deliver sufficient average Amp load over the period of time that you need - 8 or 10 or 12 hours.

Any big battery should supply enough total Amps - they are designed to crank over cold car engines! The real question is the delivery of AmpHours over sufficient time without depleting the battery so far that it is damaged before it can be recharged.

[MrB (Simon)]

Firstly the laptop DC-DC converter,
19.5v/12v = 1.625 increase in voltage, so 4.62A x 1.625 = 7.5A current draw.
Lets say its 80% efficient.
7.5 / 0.8 = 9.4A or 12x9.4 = 113 Watts

113+2.5+13 = 128.5 Watts total
128.5/12 = 10.8A MAXIMUM current draw.
The laptop is not likely to be running at max power tho, so most of the time I reckon you'd be somewhere between 5 to 7.5A draw.

If you have two 26Ah batteries in parallel (52Ah), and lets say a worst case of 10A draw, the batteries would supply 52Ah/10A = 5.2h....
But, SLA battery capacities are rated at 20 hours because it looks better, (26Ah/20h = 1.3A per hour for 20 hours), at higher currents there is loss due to internal resistance in the battery.
Jaycar says the 26Ah batteries are rated at 3.74A over 5h(18.7Ah), so two in parallel would handle ~7.5A for 5 hours.

There ya go, about 5 hours with two 26Ah batteries.

[John K]

Originally Posted by MrB

There ya go, about 5 hours with two 26Ah batteries.

Thanks for that. So my guestimate for a 130amp battery for 12 hours does not seem far off. Would need a truck to carry it there!

I guess will also get a 1-2 hours out of the lap top battery and could simply also buy a spare. Might be better off trying to find a powered camp site somewhere north of Melbourne instead!

Originally Posted by erick

John, it's 137.15 AmpHours - a bit different to Amps!

Are you sure that your mount drive is as low as 500mA - what about when it is slewing?

No dew heating??

No slewing with this scope and no dew heating. The drive is a Losmandy same as on the G11 so that's what it comes up in the specs. With a 17am Celestron Powertank have run if for 10 hours no problems

[Barrykgerdes]

I have never had much success with battery power for trains, computers, telescopes, golf buggies, lighting etc. The batteries always seem to be flat when they are most needed.

I still use a battery to power my LX200 in the field. I have a couple of discards from the golf buggy that are OK for a few hours at about an amp but useless in the golf buggy.

However I saw the light many years ago and now have one of those quiet 2Kva inverter generators. It runs for about 14 hours on a tank full (7 ltr) and supplies my computers, lights, (bed warmer), toaster etc. I keep a spare 10 ltr. can of fuel and can always get more.

I cover it with a metal frame and throw the unused caravan annex over it and it can't be heard 4 metres away.

Barry

[GrahamL]

I got one of these a while back
http://www.whitworths.com.au/main_it...=123&item=4190
You can get them a bit cheaper if you hunt around,
To drop a 100 ah deep cycle battery in it would be about $210
if i remember right and it did fit as I recall , the 80ah was $180,works fine though the webbing on the strap is plenty strong the plastic buckle is hopeless , I wrapped a thick leather belt around it .

cheers graham

[John K]

Originally Posted by nightstalker

I got one of these a while back
http://www.whitworths.com.au/main_it...=123&item=4190
You can get them a bit cheaper if you hunt around,
To drop a 100 ah deep cycle battery in it would be about $210
if i remember right and it did fit as I recall , the 80ah was $180,works fine though the webbing on the strap is plenty strong the plastic buckle is hopeless , I wrapped a thick leather belt around it .

cheers graham

Good info Graham, thanks for that.

Where did you find a 100ah deep cycle battery for $210?

Looking at their site: http://www.whitworths.com.au/main_su...escr=Batteries

they look a bit more expensive?

[erick (Eric)]

Originally Posted by nightstalker

I got one of these a while back
http://www.whitworths.com.au/main_it...=123&item=4190
You can get them a bit cheaper if you hunt around,

cheers graham

Currently on special $49 at Supercheap auto. I picked up one last week. Now deciding what battery to put into it.

[GrahamL]

Bugger Eric I paid $65 for mine

Alco john but there site dosn't show the range I was shown .
They are imported and are probably the cheapest of the cheap.
I can't stress how crap that plastic buckle on the strap is when it goes you will likely wear the battery or crack its case getting out of the way .

these guys have a similar priceline by the looks
http://www.batteryguru.com.au/23.html

[erick (Eric)]

Originally Posted by nightstalker

I can't stress how crap that plastic buckle on the strap is when it goes you will likely wear the battery or crack its case getting out of the way .

Thanks for the warning. I had already looked at it and thought "Yuck". I'll come up with a quality strap. Pity it doesn't have good hinges and sturdy catch - but for $49 - well.................

[lacad01 (Adam)]

Originally Posted by erick

Thanks for the warning. I had already looked at it and thought "Yuck". I'll come up with a quality strap. Pity it doesn't have good hinges and sturdy catch - but for $49 - well.................

I purchased one of these cases for my camper trailer so it's permanently fixed, don't think I'd be toting it around unless some serious mods were made.
Haven't looked back at this thread for a couple of days but maybe something else in the mix might be to look at whether it's worth getting one of those netbook or EEEPC's, apparently they can have up to 7hours battery life ...end of the day it's another expense coupled with getting the deep cylce batteries for all the gear, decisions, decisions

[solissydney (Ken)]

Hi. I use a 60Amp, deep cycle car battery. From memory I paid $220.00 a few months ago. Try NRMA for cheaper prices.

[mill (Martin)]

Ok everyone seems to assume a laptop is running on full power all the time
That is not true at all.
A laptop will only use full power when everything is set on full and you use the full processor cycles (eg stacking or long calculations).

The power supply only charges the internal batteries and the amperage fluctuates between 0.2 and say 4 Amps when charging the batteries while using the lappy (measure this if you don't believe me ).
The rest of the time there will be just a trickle charge.
When there is no battery in the lappy the amperage will flutuate a lot more.

Just my 2 cents here about lappy's.

[RobF (Rob)]

Originally Posted by mill

Ok everyone seems to assume a laptop is running on full power all the time
That is not true at all.
A laptop will only use full power when everything is set on full and you use the full processor cycles (eg stacking or long calculations).

The power supply only charges the internal batteries and the amperage fluctuates between 0.2 and say 4 Amps when charging the batteries while using the lappy (measure this if you don't believe me ).
The rest of the time there will be just a trickle charge.
When there is no battery in the lappy the amperage will flutuate a lot more.

Just my 2 cents here about lappy's.

Agreed - Jaycar told me the DVD player is usually the culprit in laptops needing more than about 2.5 amps. I ended up buying a more expensive higher amperage converter. In their words, you don't want anything going bang when you accidentally put in a DVD at the same moment the laptop is going flat out on something with the disk drive running and every USB port plugged in. Unlikely but could happen in the field....

My Acer laptop is rated at about 3.5amps, but only seems to draw 1-2 amps in the field. I've written a basic script to blank the screen when I'm imaging and leave it alone for a while.

Another option is to buy something like an EzyPC that draws about 1amp. Won't help with dew heaters etc though.

I bought a deep cycle AGM from this ebay seller without troubles:
http://stores.shop.ebay.com.au/best-...34Q2ec0Q2em322

Worth including cost of a decent charger too to prolong battery life - not cheap.