home made battery pack

Submitted: Friday, Aug 08, 2003 at 14:08
ThreadID: 6445 Views:5668 Replies:14 FollowUps:15
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I'm really stingy about paying hundreds of dollars for a power pack that's only going to give me 12-24 amp hours to run my Engle. I really don't want to go moving stuff around under the bonnet of the 96 Jackaroo. So! What would be wrong with getting my auto electrician to pop a sealed 90 amp/hour battery into one of those black plastic battery boxes you can buy and hooking up some doovers that are in the proprietry power packs to charge the thing through the cigarette lighter ? That way, I could carry the home-made battery pack in the back of the truck next to the 40 litre Engel where it won't be vibrated. I'm told the Engel will draw about 2.5 amps and only run half the time so that's ... er ... 2.5 into 90 = 36 times 2 = 72 hours but only let the battery run down to 40% so that's 60% of 72 = 43.2 hours. How long would it then take the cigarette lighter to bring that battery back up to full charge? Would I be better of with a little $300 Scorpion type genny from e-bay or some sort of solar cell arrangement ... and where do yo get solar cells? Thanks for any help ... I'm SO confused! :-(
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Reply By: flappan - Friday, Aug 08, 2003 at 14:56

Friday, Aug 08, 2003 at 14:56
If you want to be stingy, then solar power isn't for you.

Ok, some ideas (no idea if they will actually work though).

Buy a power pack (or 2) from somewhere like Supercheap. They have 2 types, a 600amp hours and a 900 amp hours. How they go running a fridge . . . No idea, I've run 12v lights off them for days, and then started a car, no probs at all.

at about $60 each . . .

The other idea is to buy a cheap Inverter, and run a battery charger off it to charge your battery in a box.

Again, no idea if it would work or be practicle, buy hey, I'll toss up the ideas, someone will tell me whether it'll work or not.
AnswerID: 27163

Follow Up By: Patrol22 (Queanbeyan - Friday, Aug 08, 2003 at 15:33

Friday, Aug 08, 2003 at 15:33
Flappan - thems are huge batteries at 600 and 900 amp hours - sure they are about 17-14 amp hours and capable of delivering cca 600-900 amps???
FollowupID: 18651

Follow Up By: flappan - Friday, Aug 08, 2003 at 16:00

Friday, Aug 08, 2003 at 16:00
Purely from memory.

and its been know to fail me before.

Quite possibly you are correct. I don't profess to be an expert, as I said, just chucking up ideas
FollowupID: 18652

Follow Up By: Member - John - Friday, Aug 08, 2003 at 20:27

Friday, Aug 08, 2003 at 20:27
Hey Flappan, Been thinking about one of those super cheap jobs just to run a 12v light and a shower for 10 min a day. More importantly, I want a back up should I run the Jackaroo's battery flat. Dont Have a dual battery setup and don't want one. Worried that after a few days in the bush using the light and shower, there might not be enough left to jump start the Jack if I need to.

Am I reading you correctly ? You've Jump started after running lights off the battery for a few days ?

FollowupID: 18669

Follow Up By: flappan - Monday, Aug 11, 2003 at 10:16

Monday, Aug 11, 2003 at 10:16
Yep, quite easily.

In fact, I jump started my vehicle several times, ie 10 times or more before I recharged it, only because I did, rather then I needed to.

They are cheap enough anyway, worth looking at regardless.
FollowupID: 18867

Reply By: Member - Bob - Friday, Aug 08, 2003 at 15:26

Friday, Aug 08, 2003 at 15:26
EO, I don't think a normal leadacid battery will recharge that well throught the cigarette lighter. It will take ages and probably never be fully charged. An alternative, albeit expensive, is to use an Optima sealed battery in a similar way. I wouldn't charge it through the lighter though as it will pull more than 10 amps when charging. I'd run a separate heavy duty line from the battery terminals (protected by adequate fuse) back to where you choose to locate the Optima battery (also protected by fuse). The Optima is about $300 but should last for years.Bob
AnswerID: 27166

Reply By: Blackie - Friday, Aug 08, 2003 at 15:27

Friday, Aug 08, 2003 at 15:27
Supercheap sell a black battery box pre-wired with a cig plug and terminals on the outside You just drop in your battery of choice. Marine dealers sell these as well....about $80.00. You could make your own. I had to take my Waeco pack apart, the wiring looked pretty straight forward (if you knew what you were doing) The batteries in side look like one available at Supercheap, Tandy etc.
AnswerID: 27167

Reply By: ExploreOz - Friday, Aug 08, 2003 at 15:45

Friday, Aug 08, 2003 at 15:45
Thanks people. That Supercheap Auto suggestion sounds the way to go. Seems it's a feasible idea after all (someone's already invented it!) which makes you wonder why anyone would pay so much for a Waeco that's only a fraction of the amp/hours. Jim
AnswerID: 27168

Reply By: ExploreOz - Friday, Aug 08, 2003 at 16:43

Friday, Aug 08, 2003 at 16:43
When I said I was stingy about buying eg a Waeco powerpack, it was only in the sense of being unwilling to be ripped off by a drastically overpriced product (for what they are). .. and why settle for 24 amp/hours when you can have 90 amp/hours just as easily and more cheaply. But that still leaves me at the campsite after 3-4 days with a flat powerpack and a hot fridge. There's the little e-bay gennies for $300 ... but what sort of solar panel would I need? How big? Where from and how much? Thanks Jim
AnswerID: 27171

Reply By: haze - Friday, Aug 08, 2003 at 16:43

Friday, Aug 08, 2003 at 16:43
Exploreoz I use the system suggested by Bob in the back of our Disco. Using a normal 9pl. Exide, and as well as the fuse a 20a. diode which prevents current back flowing as the vehicle is started. Also a switch at the battery used as an isolator. Seems to work ok.
cheers haze
AnswerID: 27172

Follow Up By: David N. - Saturday, Aug 09, 2003 at 17:10

Saturday, Aug 09, 2003 at 17:10
haze, and others... I highly recommend you do NOT use a diode as there is a voltage drop across the diode which will prevent anywhere near full charge being attained. You will get much closer to full charge by avoiding the diode.
One option is to use a suitable resettable circuit breaker to charge it and a bit of "back flow " when starting will just pop the breaker for a while if you crank for long... or you can manually disconnect while you start and then reconnect the battery charge lead. Personally, I don't worry about the back flow as it does no harm.
Or you can go the whole hog and get a proper dual battery system.. it all depends on how much you want to spend...
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Reply By: Eric - Friday, Aug 08, 2003 at 21:04

Friday, Aug 08, 2003 at 21:04
the $300 gen from ebay are great to charge your battery rince they offer 13 volts and 2450 @700 watts . If you want a long lastng battery , go to Powercrank and purchase a deep cycle battery will last ages ,But remember to run it flat .

Ps a 12 volt fluro will run for ever off it
AnswerID: 27193

Follow Up By: David N. - Saturday, Aug 09, 2003 at 17:12

Saturday, Aug 09, 2003 at 17:12
I hope you meant NOT to run it flat.
Running it flat, or close to it, will destroy it very quickly.
FollowupID: 18746

Follow Up By: Eric - Sunday, Aug 10, 2003 at 08:57

Sunday, Aug 10, 2003 at 08:57
Yes I did mean Run it flat , thats how a deap cycle battery works , if it is a standard battery , you are correct this will kil it , thats why I suggested the deap cycle works a treat . I run a Deap cycle battery as my secondary battery and I have flattened it more times than I would like to remember , rercharges a treat
FollowupID: 18797

Follow Up By: David N. - Sunday, Aug 10, 2003 at 16:53

Sunday, Aug 10, 2003 at 16:53
Eric, no offence intended at all,
but for your own benefit I suggest you learn a bit more about lead acid batteries...
Deep cycle batteries are a little more tolerant of being run flat than starting batteries, but you should still never run it flat if you want it to last.
If you run it dead flat you will shorten it's life DRAMATICALLY!
NickleCadmium batteries like to be run flat, Lead acid batteries should never be flattened if possible, and that includes deep cycle batteries. Don't take my word for it- ask someone else who knows a little about batteries.
As I said I'm not having a go at you, but for your own benefit I suggest you learn a little more....
FollowupID: 18823

Follow Up By: Eric - Sunday, Aug 10, 2003 at 19:56

Sunday, Aug 10, 2003 at 19:56
I wasn't offended Dave , thats why I suggested the phone call to power crank direct . We are all here to learn , and I love to hear everyones oppinion thast why i love this forum . Thanks for the input .
FollowupID: 18838

Follow Up By: Old Jack - Sunday, Aug 10, 2003 at 20:54

Sunday, Aug 10, 2003 at 20:54
To All
NickleCadmium batteries DON'Tlike to be run flat, in fact you will damage them sifnicantly by running them totaly flat.
individual cel voltage should not be allowed to fall under about 1 volt per cell( each cell in a NIcad. is about 1.2 volts)
you run the risk of having a battery that will not re-charge if you run it flat.
the discharge curve for a Nicad cell is very flat. once the charge drops the current & voltage output falls very rapidally.

Ni-cads should be stored fully charged and re-charged after a cooling down peroid as soon as possible after discharge.

FollowupID: 18840

Reply By: Member - Tony- Friday, Aug 08, 2003 at 22:00

Friday, Aug 08, 2003 at 22:00
If its any help I run a battery in the back dedicated to the fridge. It is connected to the dual batteries under the bonnet via 6mm wire and through an accesory hella spotlight relay wired to the ignition. Charges equally with the main battery and when the ignition is off there is no drain back. If you should run the rear battery flat swap the spade terminal to the other side of the relay and you are drawing of the vehicle battery. Had this in place for years without an ounce of trouble.
CheersThe Ghost
AnswerID: 27200

Reply By: Member - Rick - Saturday, Aug 09, 2003 at 00:49

Saturday, Aug 09, 2003 at 00:49
G'day ExploreOz

I have recently thought of doing this method also. But if you use a lead acid battery, for safety's sake you should not keep it in your truck. Why not you ask? Well, vapour + spark = BANG.

Therefore a sealed gel battery like Opitma would do the trick. But these cost.........to get a battery box + battery + plugs, wire, etc= about $ 400.

So the perspective for a Waeco type pack appears different now, eh?

I finally repacked by rooted Urban for $ 120, and have portability (best feature for my money - I take the battery & light to the required spot, usually well away [50 foot +] from the vehicle. 12 V light cord is only 20 '). I also get peace of mind + some performance for fridge, heaps for lights, and enough oomph to turn the truck over of the Exide Extreme carks it.

CheersRick (S.A.) - ' It is better to travel hopefully than arrive'
AnswerID: 27224

Reply By: ExploreOz - Saturday, Aug 09, 2003 at 01:04

Saturday, Aug 09, 2003 at 01:04
Thanks for replying but at $659 for 48 amp/hour in the Waeco Thumper, l still think $400 to build my own 90 amp/hour pack works out better Jim
AnswerID: 27225

Follow Up By: David N. - Saturday, Aug 09, 2003 at 17:16

Saturday, Aug 09, 2003 at 17:16
Couldn't agree more.
Have my own "home made" battery pack which is way way better value than the commercially made Waeco etc.
Just remember to never run it flat or it will not last long at all. About 30 to 40% is suggested minimum charge state for a deep cycle battery.. the more deeply you discharge it the shorter life you'll get from the battery.
FollowupID: 18747

Reply By: ExploreOz - Saturday, Aug 09, 2003 at 17:47

Saturday, Aug 09, 2003 at 17:47
um ... hang on ... there's conflicting advice here : Eric ses to remember to run a deep cycle battery flat and you say remember to only flatten to 30% ... I'm all confused agin! :-)
AnswerID: 27273

Follow Up By: Eric - Sunday, Aug 10, 2003 at 09:08

Sunday, Aug 10, 2003 at 09:08
Give powercrank a call on 03 93540009 and ask them , I remeber Tass telling me to run it falt or close to flat , but it dosn't hurt to ask the sourse dirrect , we all can make mistakes . The way I undestood it was the longer and slower charge the better .
FollowupID: 18799

Follow Up By: David N. - Sunday, Aug 10, 2003 at 17:26

Sunday, Aug 10, 2003 at 17:26
anyone who tells you to run your battery anywhere near flat just wants to sell you another battery ASAP.
Even dedicated power supply deepcycle batteries (which are not the "deep cycle batteries " you can buy for your car or caravan) do NOT like being flattened. Lead acid batteries OF ANY DESCRIPTION should not be flattened if you want reasonable life from them.
The "deep cycle" batteries we all buy for running fridges etc etc (which look like a normal car battery) are really only a modified starting battery- a true deep cycle battery is very heavy indeed and totally unsuitable for cars.
FollowupID: 18830

Reply By: Deano - Saturday, Aug 09, 2003 at 21:36

Saturday, Aug 09, 2003 at 21:36
Dunno much about the porta paks but recently was treated to a sheep on a spit cooked for 12+ hours and run off of it and the owner hadn't even recharged it. Then, about midnight jumpstarted his mates ute NP.

dealer I recently bought my L300 4by also had one and asked what he thought about them. Reckons he has jumpstarted around 14 vehicles without the thing going flat.

Seems they got the cranking power but as far as amp hours and the math stuff I am lost. Seen them for $139 at repco so just buy two? :)
AnswerID: 27288

Follow Up By: Member - Des - Monday, Aug 11, 2003 at 12:54

Monday, Aug 11, 2003 at 12:54
We got a reconditioned model from Projecta JumpStarter for $80. Has a 17A/hr battery, weighs about 5kg. Not sufficient to run a fridge, but adequate for lights, shower pump, air compressor, etc, and handy insurance against a flat battery. Recharges from cig lighter plug in a few hours. Suits us fine and very happy with it. See Projecta web site.

If you tried to run a fridge from it (say 1.5 or 2 amps/hour) it would run flat overnight and maybe wreck its battery. Having two of them wouldn't solve the problem - you'd be better off getting or making a bigger one. Thanks to all for the tips on that topic.
FollowupID: 18886

Reply By: haze - Sunday, Aug 10, 2003 at 14:41

Sunday, Aug 10, 2003 at 14:41
Quick reply to David N.. The diode now used came from a u/s alternator. it is located on a small panel adjascent to the rear battery.With the dig. voltmeter,main batt. at high idle 14.35v., rear battery 13.9v., with engel running (very old 17l. mod.) 12.25v. So whilst its not charging the daylights out of it, its not losing much either. I do have a far more elaborate setup in the 75 trayback, but it runs freezer, lights, invertor etc. Anywhere from 20a. charge rate (adjustable) using a honda driven 12v. alternator.
cheers haze
AnswerID: 27341

Follow Up By: David N. - Sunday, Aug 10, 2003 at 17:15

Sunday, Aug 10, 2003 at 17:15
haze trust me! (I'm not a used car salesman- or a battery salesman either!!)
You'd be better not using the diode! (I do know what I'm talking about as I was an electrical engineer many moons ago.)
It's always difficult to charge an additional battery properly without an expensive setup, and a diode only makes things worse. The small voltage drop through the diode is bad news and will prevent you getting your battery charged anywhere near max, which is very important both for the long life of the battery and of course how much you'll get out of it before it needs charging again..
A heavy duty relay, (which you can switch manually if you like) however, has virtually no voltage drop and is a much better option if you don't just want a "manual" connection.
I offer this advice purely for your own benefit, as I don't like people getting bum steers from some of the ignorant "experts" out there and I will never make a dollar out of selling you another battery.
Cheers and best wishes.
FollowupID: 18826

Reply By: haze - Sunday, Aug 10, 2003 at 18:02

Sunday, Aug 10, 2003 at 18:02
David, I do trust you, honest (now where have I heard that before!!) By making the initial reply I did was because I reckoned Exploreoz was looking for a fairly elcheapo way out to keep the engel going, which is exactly what Idid for our Disco. And as Isaid, it works, the batt. doesnt go flat, but it is only a "weekend away" arrangement. And I COMPLETELY agree, if you want long term ie.5/6 months away you have to have a far more dedicated setup. Which I do have in my 75s. L/C. Manually switchable solenoid/s for up to three extra batts, 12v. alternator with switchable regulated or constant output (the only way to FULLY charge a battery) driven by a 4hp. honda motor. Amp and volt meters to monitor the goings on AND most important, wiring/ connections (soldered) switches of a capacity to maintain volts and current where you want it. But this dont come cheap, even when you do it yourself
Sometimes a bloke is better off keeping his trap shut!
Thanks anyway David
cheers haze
AnswerID: 27357

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