Buying the right power pack 1

[PeterAL]

I am going to be buying a Roland CD-2e recorder and using it in locations where I cannot plug it in.

The tech specs of this unit tells me that it has a current draw of 540 mA, and when using batteries it takes 6 X LR6 (AA) type alkaline batteries - so 9 volts DC, right?

The specs also say I cannot use the AA batteries for CD writing and reading, that the unit must use the AC Adapter.

Therefore I need a portable power pack sized to run this unit, full time, for about 12 hours per day, and then be able to plug it in over night and recharge it so it can do it again the next day, for 4 -5 days in a row.

Many of the power packs I see on the market have auto battery boosters cables, a light, a radio and other accessories, that I do not need, but I suspect I'll have to take. All I really need is the power pack that can be recharged and, I guess, the inverter to run the AC adapter.

Can you folks help me choose the right size of power pack and if you have any suggestions for a specific brand and model, I'd be glad to hear it.

I'd also consider assembling the parts myself into a suitable case, making my own power pack, but I suspect buying the ready made unit will be a lot simpler.

Thanks

 

[IRstuff]

Why not just an auto battery with an on-the-shelf inverter to power the AC adapter?

see:

http://www.yuasa-battery.de/englisch/download/NP_D_Engl.pdf

Assuming that your AC adaptor can source 1 amp at 9V, and assuming 40% adaptor/inverter efficiency, you need to supply about 20 W continuously, which is about 1.7 A at 12V, which requires a 24 Ah battery



TTFN

FAQ731-376

 

[itsmoked]

Can't you run the unit on 9VDC and still run the drive? You've only stated you can't run it on the measly AAs not that you can't run it on 9VDC. It would be much better to stay in the DC realm.

What is the labeled OUTPUT of the adapter?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[PeterAL]

Yes a 24 Ahr battery, and an inverter, and a battery charger will do the job. And, i'll probably end up with an off-the-shelf power pack.... my question was what size power pack should I get?

As for staying in 9 volts DC, that would be the most efficient, wouldn't it. The Roland site does not tell us the OUTPUT of the adapter, and I only assume its 9 VDC. I have a friend who has one of these units and I'll get them to check.

But again, if I stay in VDC, I'll still have to buy an additional charger.

I'm looking at a unit available locally and I'll probably get it unless one of you experts points me elsewhere. Its this unit:

http://www.canadiantire.ca/AST/brow...acks/PRD~0111823P/Eliminator+PowerBox+800.jsp

Thanks very much for all your help. I love forums.

 

[itsmoked]

If you go the inverter route you should try to get one that is twice the AH your device really needs as you wil be suffering double conversion losses and getting a pack that provides about the energy demanded means you will be over discharging your batteries. B A D L Y. Expect about 10 cycles before failure. Also expect capacity shortage starting about the 5th cycle.

You need at least twice the required AH. This is why you want the efficiency as high as you can get it because you also need twice the capacity demanded by those inefficiencies.


Look at this:

http://www.powerstream.com/daa-1209.htm

You need 540mA x 9V = 4.9W

converter 70% efficiency => 7W

7W/12V = 0.6A

0.6A x 12hrs = 7.2Ah/day

If you charge every night then you should use a 14.4Ah or larger battery.
Common LA size is 17Ah.
See:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P174-ND

An excellent charge is found here:

http://batterytender.com/battery-tender-plus-12v-at-1-25a.html

Keith Cress
kcress -

http://www.flaminsystems.com

 

[PeterAL]

Now you have me interested in building it from parts... I needed a project!

The battery you mentioned is the Panasonic P174-ND and weighs 14.3 lbs.

The converter only weighs 7 oz. and charger is 3 lbs, so all the parts, plus cables, etc will not exceed 20 - 25 lbs. I can lug that to where its needed easily.

I'll be looking locally for a sturdy, rugged, tool box or something like that, in which I can mount the parts.

Thanks for your help. As the project continues, I'll take some pictures and share them with you.

 

[PeterAL]

It just occurred to me... is there any special need for ventilation for the battery, converter or charger?

In use, the battery and converter will be in a building at a trade show.... a convention center.

I see the battery is sealed, so I assume if I carry it at a shallow angle from time to time, it won't damage anything.

When charging, the setup will likely be in a hotel room, getting charged for the next day's work.

Any special environmental issues I should know? Fumes? noise?

Thanks

 

[PeterAL]

Ok, more questions...

If I put all these parts into a carrying box of some sort and hook them up together, will they conflict with each other?

The converter is wired to the battery, and so is the charger. Is there any risk of damage to the converter while charging? Is there any risk of damage to the charger while using the battery/converter combination connected to the recorder?

Or will I have to disconnect one element while using the other?? If so, I guess some sort of switch might be handy.

Thanks

 

[IRstuff]

Most batteries will generate hydrogen during charging, so good ventilation is a must.

Your circuitry should be disconnected from the battery during charging. A typical charger will put out several volts above the battery nominal voltage to essentially "push" the power back into the battery. The higher voltage could potentially damage the inverter, although it should be designed to handle the voltage range.

TTFN

FAQ731-376

 

[itsmoked]

In this case you should not have a problem hooking up the charger and leaving it hooked up. It should not discharge the battery if the charger is unplugged but remains hooked up.

The DC-DC should even handle running while the charger is powered because the charger should not put out more than 15V which is the input rating of the DC to DC.

There should also be no hydrogen evolved in this case. I would probably NOT ventilate the case unless it will never see rain. Instead I would run it with the lid ajar. Or you can ventilate it and not worry about it.

If you do ventilate it you want some holes near the bottom and some near the top.

You should certainly give it a test before your show. You want to make sure things don't get too hot in the resulting box.

A tool box is a good idea that would allow easy handling. It will also provide storage for the cords.

I would also add a fuse to your output, 1A. So if the cord gets shorted you don't lose everything.

One last feature I'd add would be an in-line set of connectors. The reason is for the unexpected. In a trade show you could easily have someone catch the cord with something. You want the plug to just un-plug not yank the device you're powering off onto the floor. A straight in-line connector set will do this. The one in the device will invariably be at right angles to any pull and NOT automatically unplug.

Good luck.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[PeterAL]

Thanks guys... you have all been a great help.

I will follow up with info and pics as I get this going.

 

[PeterAL]

In looking at the converter, I see another one offered by the same supplier... will it do the job as well? I see that its switchable allowing me to use this unit for other devices.

Thanks

http://www.powerstream.com/daa-1209.htm

 

[PeterAL]

I cannot seem to make the link work for that page... the model number of the one I mean is PST-DC292.

Its the second or third one down the list.

Will that one work as well?

 

[PeterAL]

here's a link that works:

http://www.powerstream.com/dc6.htm

 

[itsmoked]

Looks okay to me.
Have at it.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[PeterAL]

"The time spent in reconnaissance is never wasted"...

I dunno who said it first, but it appeared several times in the books of one of my favorite authors, Ted Allbeury.

I've been mulling this whole project over in my head today and trying to come up with an idea for a suitable carrying case for it. I had planned originally to use a heavy duty plastic tool box, but in order for the battery to sit upright, I'd have to get a box that is quite long - 20 inches, or so.

So I cast around looking for a box that was sturdy enough to carry the battery and other parts, tall enough so it could stand upright, and with a handle on the top. And finally I discovered the ideal box - an ammo box! With the configuration detailed above, the 50 caliber ammo box will do the job well, I think. Here's a link to what I mean:

http://www.usmilitarysurplus.com/surpluscatalog/product_info.php?products_id=841

Should work well, no?

Then I started thinking about trade offs. Based on the design above, I'll be carrying this box back to the hotel every night and recharging the battery on the hotel plug in.

What would it take to have a setup that would last the whole show?

Typically;
Friday 12 hours
Saturday 12 hours
Sunday 8 hours

Total 32 hours

Then I went back to KC's calculations, as shown above, and tried to bend my head around it, using 32 hours and using the other multi-output converter.

Here's what I got:

9V @ 2.1A = 18.9W

converter efficiency 73% X 18.9W = 13.7W

13.7W / 12V - 1.14A

1.14A X 32 hours = 36.5 Ah

Double that = 72 Ah and that equals a BIG battery or two smaller ones. I abandoned my math calculations there, and I now assume that if the previous battery is 20 lbs weight, this new configuration is probably going to weight 50 - 60 lbs, more than I want to lug in. I'd probably end up with some sort of wheeled dolly arrangement - just not worth the aggravation.

So, KC, I'm staying with our original design and I'll be carrying the unit back to the hotel Friday and Saturday nights to recharge it.

Can I have your input, comments and suggestions?

Thanks

PeterAL

 

[itsmoked]

Fine. Just one adjustment.

Gelcells can run in ANY position. So stop worrying about keeping the battery upright.

Now can you use a smaller toolbox?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[PeterAL]

Ahah!!!

 

[IRstuff]

18.9W/73% = 25.9W

25.9W / 12V = 2.2A

2.2A * 32 hr = 69 A*hr

Then, double it...

TTFN

FAQ731-376

 

[PeterAL]

Yeah, I'm not surprised my math was wrong...

Thanks