Mobile Power Solultion

[sombrenote]

I am looking to see if you have a particular product, and I am having troubling finding it.

I need a supply/charger that will take a car battery which fluctuates between between 11 and 13.8 volts DC(in use), and output 12V (or more) contently using a battery backup (different then the car battery) supply.

So basically.

Input: 11VDC-13.8VDC
Output: 12-14VDC with battery backup

My problem is that the system I am trying runs great unless the voltage from its source drops to ~11.4 volts because the car is using external devices that draw a lot of power. I need a power backup that will let the power through when it is good, and use the battery backup when it is lacking.

Do you guys have anything like that?

 

[IRstuff]

websearch:

http://www.dogpile.com/dogpile/ws/r...e/iq=true/zoom=off/_iceUrlFlag=7?_IceUrl=true

http://www.powerstream.com/DC-UPS-1212-10A.htm

TTFN

FAQ731-376

 

[itsmoked]

How about a second battery and a charge isolator? Or just two batteries in parallel? If you are often dragging the battery voltage down below 12V you are drawing pretty heavy from it.

Have you actually measured the battery voltage at the battery terminals during a "heavy draw"? Perhaps you could run your sensitive device directly from the battery posts and not thru any shared wiring.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[bklauba]

Try these folks:

http://www.powersource.net/

BK

 

[sombrenote]

"How about a second battery and a charge isolator? Or just two batteries in parallel? If you are often dragging the battery voltage down below 12V you are drawing pretty heavy from it.

Have you actually measured the battery voltage at the battery terminals during a "heavy draw"? Perhaps you could run your sensitive device directly from the battery posts and not thru any shared wiring.

Keith Cress"

I have considered this, but people are telling me there are a few problems. My system is not the one dragging to voltage down, it is the buses lift, and glow plugs which do it. And that collapses my system. I have actually measured the battery voltage at the battery terminals during a "heavy draw". It does not seem to be a matter of shared wiring, because my power comes right out of the batter pretty much.

The problem people are telling me with an isolator and battery is that my system does not draw enough power (5A), to make sure the battery does not explode if it is always being charged by the isolator while running. I would have to connect the door to my battery to make sure it does not blow up, and I am not supposed to do that. A solid state breaker would work to stop it from charging, but then I would have to watch and flick the thing back on all the time.

Thank you for any comments people might make. I have really been recking me brain over this.

 

[sombrenote]

Will this thing work?

http://www.powerstream.com/DC-UPS-1212-10A.htm

If my computer is using about 5 amps while running?

 

[IRstuff]

Why wouldn't it?

TTFN

FAQ731-376

 

[waross]

The charge in a lead/acid battery is voltage limited.

The problem people are telling me with an isolator and battery is that my system does not draw enough power (5A), to make sure the battery does not explode if it is always being charged by the isolator while running.

Not going to happen with automotive batteries.
All you need is a battery of sufficient capacity to run your computer and a diode to charge it from the vehicle alternator. The diode will prevent any loads on the vehicle battery from being seen by the computer battery and will allow the vehicle alternator to charge the computer battery any time the alternator voltage is above the computer battery voltage.
Make sure that your connected equipment can survive load dump issues.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MacGyverS2000]

What are you attempting to run? It sounds like a mini computer... what is its purpose?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[roydm]

Sombrenote,
It seems really simple to me, I must be missing something. RVs usually have two batteries, each one charged thru a diode.
From each battery use another diode to feed your load that way when you're cranking the auxiliary battery will supply the load. The aux battery could be much smaller e.g. motorcycle type. Overcharging would not be a problem as they share the same voltage supply.
For the diodes feeding your load use one of the potted bridge rectifiers "SDA10211, 200V/15A Motorola" or similar bolted to the chassis to provide heat sink.
The battery charging diodes should be available in your auto parts store for about $50, you will probably need one of the larger ones, 70 Amps or more.

Another possibility would be to leave the charging circuit intact and just use one diode to feed your auxiliary battery with the load permanently connected. The aux. would never overcharge because the maximum voltage it would see would be main battery - 0.6V
Regards
Roy

 

[catserveng]

I will second Bill's solution. We have similar problems with PLC based controls on gensets, we will use a small battery with a blocking diode to power the PLC so when engine cranks and voltage drops the PLC will stay up thru the drop associated with the start cycle.

We have a lot of these systems in service with no apparent problems.

 

[itsmoked]

Excuse me WHO's solution?
Please note the first response to this entire thread.

I'm not getting paid a lot here, so I need all my existential pay.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[catserveng]

Sorry Keith,

Some days I just kinda skip thru these, I think a few people may have had similar ideas.

But isn't the warm and fuzzy of sharing knowledge reward enough?

 

[itsmoked]

LOL!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

I sorry too Keith
Great minds think alike
Roy Matson

 

[OperaHouse]

A good RV center should have this item. If you are into building things,

http://www.siliconchip.com

an Australian hobby site has this as a project. I had to make a similar circuit with a TL494 and parts form an old computer power supply. My camp is 12V with high wiring losses. If the wife turns on her reading light, I can't watch TV without one of these boosters.

 

[sombrenote]

Thank you guys for your input. It has all been very helpful. We have yet to decide what we are going to go with, but I hope it is some sort of battery diode solution. Those just get kind off expensive.

People say that just using an inverter is enough to 120VAC in order to power a 12VDC brick. I do not like this solution, but they say it still works even if the voltage drops to 9 volts.