I would like to know if anyone has any details on running gear off a car battery. Essentially how does one hook up a power strip to a car battery, how does one recharge the battery and how much gear could be powered from a car battery and for how long. I would be running a Macbook pro, a metric halo ULN2, a DI box and maybe one or two external hard drives. I'm assuming running off a battery would give clean power free from any hum.


Thanks to anyone with any practical tips to get such a setup working.

I have a gigantic version of what you're talking about: my studio (and the whole house!) runs off a 12-volt battery bank-- it's your standard photovoltaic installation.

I've got an Excel-tech inverter to deliver pure sine wave AC from the batteries. The power is perfectly clean and static/glitch free. Electronic gear takes very, very little power to run, as far as the nitty-gritty details of exactly how to size your system, I'd get ahold of

www.backwoodssolar.com

These guys know the stuff inside out, they live and work with it every day. Good luck!

hey tc5 I know about running equipment off of automotive batteries. ok basically how it works is you need a deep cycle automotive battery. different from a car battery as it takes more of a drop in charge and can be recharged easily. traditional ones need to be well ventilated. due to release of hydrogen gas through the vents. agm style ones can be stored in a closet without a vent and sealed ones ie optima can be stored anywhere. so a marine battery is Dc so you need a power inverter( search x-power) to convert that to ac house current. try to get yourself a true signwave inverter it is easier on your gear. now thease have two places for leads that connect to the terminals of the battery red to red black to black etc. make sure the wire is at least 4 guage. then there is a transformer and regular house plugs and a power switch on the front of the unit. Now there are various sizes of inverters and you must to a little research to get the right one. basically on the back of all the gear you use or where the power plugs into the gear there is a sticker that says how many amps it draws. do this for all your gear you are using. ie my digi 002r draws 5A. and total it up. then multiply that number by 115 and it gives you the total wattage you are drawing ie. 5a multiplied by 115 is 575 watts. and then you can select the apropriate wattage of inverter. and I would give a little extra for added room. ok then plug a power conditioner to the house plug at the end of your inverter and then plug all your gear in the power conditioner. now as to how long this will work is up in the air you can go to your local home depot and on the back of thease inverters it will tell you aprox. how long power you will have. get a marine battery with the longest reserve time possible.

As for recharging the batteries a typical automatic battery charger will do the trick I would get at lease 75A charge or you will be charging the thing for weeks. it does take about 8 hours to recharge a marine battery. I have also used rigs that were in a trailer that used a dual battery isolator to the altenator. but that is more for permanent setups. If you have any more questions IM me.

I will point out that at least the ULN-2 (and probably the Hard Drives) can be run directly off the battery's 12v DC. You will get a longer run time if you use the DC directly rather than inverting to 120v (because each conversion is only 80-90% efficient). The one device that you have listed that is potentially problematic without using the DC->AC inverter is the Mac; the MBP wants to see 24v (IIRC). You may be able to figure out how to use one of the airline power adapters (which are 12v in) to run the MBP directly from DC.

Either way you go, you'll be fine (if you follow the other advice in this thread). But you will get longer runtimes if you directly power the devices that actually support DC power. You can even direct power the DC devices and use an inverter for the MBP.

Good luck!

Some numbers must be wrong there. That unit can't draw more power than a Krell!! Maybe 0.5A?


/Peter

Just a heads up, I tried running a laptop and an audio interface off my standard car battery with one of the nicer AC inverters that you can get, and the audio starting glitching up and such until I unplugged my laptop. I'm guessing this isn't something you can do with a $40 AC inverter like I bought, so don't bother trying with something like that.

Hmmm, you might have had something that's designed to run a power tool or something with your car, in which case it might have been a square wave inverter? Hard to know but there's a big difference between square wave and sine wave.

But then, on the plus side, if it was only $40, that's great, even if it doesn't work right.

Thanks all for the input. All quite helpful. One thing I forgot to mention is that I'm in the UK. If that makes any difference.

You do know to drive on the wrong side of the road, right?

Well I'm not sure, it was made for running laptops off of the car battery, but plugging in the audio interface as well is when it started bugging out.

Cool!

Is this because you can't get grid power, or just because it's more reliable than grid power?

Always wanted to do something like that, but it's never been practical for me.

Out of curiousity, is there a lifespan for those battery packs? I've heard that hybrid cars like the prius needs to replace it's battery pack after three years. I get about the same life out of most of my laptop batteries. The laptop batteries start to show their age after a year, and after three, they're useless. Most times it's cheaper to replace the laptop than the battery for it.

Very cool Joel, I didn't know that you where off the grid. That's awesome.

To the thread originator. I highly suggest you use a Black & Decker Electromate 400. It is a rechargeable portable power station, jump-starter/ air compressor, (Not 1176 : )

I have one of these babys and it is awesome. I use it to record on location sound so that I can use my custom Class A tube pre with my Sennhieser 416 shotgun mic.

Long, winding story.... the short version is when we were living in a cabin in Vermont in 1983, we got a few panels and a few batteries, to see if it really worked. It really did! Fast forward to today-- always built in places where it was cheaper to set up a PV system than to bring grid power in.

And the whole awesomely cool/futuristic angle, you can't knock that!

I was going to say the same thing. At home my 002, G5, Rack of pres and my mackie 8bus 200W PSU are happily sipping away at 4.3A of power right now...

Okay, first of all you need to know exactly how much power you'll be drawing at any given time, lets say 1500 watts so that you can choose a proper inverter.
Second of all, an off the shelve inverter like a Black & Decker (or radio Shack's) is NOT what you're looking for but a "pure Sine Wave power Inverter" which is going to cost way more cash than you may think...
Third, a much better option than a regular car battery is a deep cycle Marine battery, as these are hard core proven batteries which won't render inoperative in a few of months of demanding situations.
Cheers!
S.

I disagree with the above post. I've been using my set up for awhile now with stellar results. I would suggest you don't knock it, till you try it...

I avoid driving on the wrong side of the road to limit the number of casualties....

Yes I saw at the link posted by Joel that those are quite expensive indeed...

Its okay to disagree... On my side I work with 12v lithium NP1 batteries and all my equipment runs natively on 12v so I dont need an inverter, but I do own a 1500 watts pure sine wave power inverter just in case I'll ever need it.

There is nothing pure in this world.

Regular lead acid car batteries are not designed to be drained all the way. They are designed to start the car and then spend the rest of the trip recharging. Running a lead acid battery until it is empty, or close to it, can shorten its life.

NiCads, Lithium Ion, and other batteries are designed to drain all the way down and then recharge. You can get these in large sizes, like the size of a car battery, so you can record for a long time.

I'm using regular lead acid batteries for my 12V-based setup since years. Many years. Regular car batteries are perfectly fine - there's really no need to spend money on marine deep-cycle etc stuff. It's not worth it.

Of course one doesn't run them down - the trick is to get some that are big enough to deliver and have an eye on them. And that goes for any kind of chemistry.


Karl Lohninger
midnight oil films

NO, NiMH should not be drained all the way down! Most devices that use them will prevent that from happening.

Same with Lion.

Perhaps you mean drained down to what is nominal for such a battery in a discharged state? Or drained by a device that is designed to discharge these batteries?

Yes. Battery powered equipment is usually designed to shut down if the battery gets too low before ruining the battery.

If the OP wants to create a custom battery rig to record for a long time, he needs to figure out when to stop recording when the battery power gets down to a certain level before ruining the battery.

In my experiences, a lead-acid car battery is heavier than other batteries, and it is the least forgiving if you run it all the way down.

For the novice, something like the aforementioned Black & Decker Electromate would be the best solution.

If you accidentally short out a car battery, you could have an explosion with acid flying everywhere. Hopefully you would capture the sound of the explosion before you loose all power! heh

I'm reviving this old thread. I'm looking at the specs for Amperes on my equipment and I'm not sure I understand exactly how much juice I would need to run these:

SSL MYNX:
DC +5V - 2.5A
+/- 15V - 0.3A

API 7600:
0.5A/0.25 A - 250V

Metric Halo ULN2:
+24V - 2.0A

Wiebetech Drive:
output 12V 3A
input 1.2A

MacBook Pro 15":
Not sure how many Amps but I could run this off its own battery

The specs are a bit confusing regarding the input and output. Which is the relevant one to calculate the needed power?

Thanks for any help.

I hear you on the lead battery front, but I still like the confidence of using deep cycle batteries, because many folks do run them down to zero volts and in the long run it's not, much fun changing them out over and over.

Well, it looks like your figures mix and match AC vs. DC power for one. The 250V is most certainly AC?

You really need to talk to a specialist, I wouldn't be surprised if the fine folks at Backwoods Solar Electric Systems could boil it down for you, to the nearest decimal, anyway.

Thanks Joel. I've been looking at their site. Their examples of different setups is helpful. I'm aspiring to do as you are doing and live off the grid when I move to the country hopefully soon. In the meantime if I can run just this little setup off grid that would be good.

the 250v spec is how it's written on the back of the 7600.
T 0.5A/0.25 A - 250V

It also looks like pure sine wave power is the way to go. I only want to run on the cleanest juice!

http://www.xantrex.com/web/id/1858/DocServe.aspx

the Best Inverters with True Sine wave have 3% THD,
and most have 5%.

PS Audio Power Plant Premiere has:
0.6% output with 3.5% input.
0.7% outwith 4% input.
0.8% with 4.5% input.
allways with -80dB noise. (much better than Furman p-1800 AR + PF R)

Accuphase PS-1210 has:
0.22% THD

want to see the difference between 3% and 0.22% ?
http://www.accuphase.com/cat/ps-1210_e.pdf
Accuphase Laboratory, Inc.

APC UPS Surta 5%
Honda Power Inverters <5%

***
With and without power conditioner and Voltage Regulator
***
sad but true, anyway...
Accuphase PS-1210 0.22% THD comes pretty close.
also some 6N or 7N Silver and/or OFC cables are pretty close 99.999999%