That's right, absolutely NAC. Electrical question

Fri May 31 10:27:23 PDT 2013

Ah yes, but your battery powered devices as designed that way and have 
voltage compensation circuitry. A device that uses a AA battery likely is 
designed to work at ~1v and regulates it down to that until the battery 
depletes too far to even supply that.

-Cody

-----Original Message----- 
From: Britt Crowell
Sent: Friday, May 31, 2013 12:41 AM
To: Cody Forbes
Cc: quattro at audifans.com
Subject: RE: That's right, absolutely NAC. Electrical question

While I agree with you mostly Cody, I would add that most newer devices will 
work with in 1 to 2 +- volts of their rated requirements.
There are a lot of differences between 1.2V nimh/nicad, 1.5V alkalines, 1.6V 
NiZn and they are all higher when fully charged and still all work in an 2 
series configuration in my wifes digital camera. Start talking about 4 to 8 
series packs in other devices and the number get wild. (I do a lot of RC 
stuff)
Then you can get into the whole LiPo and LiFe batts.
Don’t know the hardware involved, but my guess is +- 1V won't matter much, 
+- 2V might start causing problems.
My suggestion was to have 2 deep cycle batts in conjunction with the regular 
starter batt.
Sounds like the user is using a CPAP to sleep.
But if it’s a major health issue, do what's safe, you can't enjoy life when 
your dead...

I love the Westy, really looking to get debt free soon and be able to do 
more traveling in a Westy type ride.
http://www.alisoncrowell.com/2003/2003-09-05_Lake_McConaughy/
The pics are of my best friends Westy. He just spent a lot of money the last 
year restoring it.

Britt

-----Original Message-----
From: Cody Forbes [mailto:cody at 5000tq.com]
Sent: Thursday, May 30, 2013 10:55 PM
To: Britt Crowell
Cc: <quattro at audifans.com>
Subject: Re: That's right, absolutely NAC. Electrical question

The line about "24v is 24v" is slightly misleading.

Two automotive batteries at full charge in series do not add up to 24v. A 
healthy automotive (and marine, etc) battery is 12.7v. In series you'd be 
supplying 25.4v which, depending on how sensitive the circuitry is, *could* 
be enough to let the smoke out. If he accidentally left it plugged in with 
the engine running the charging system would bring it up over 26-28v.

The device the customer needs may be relying on a nice clean 24v. Due to 
other loads on the system, charging system variations, and other variables 
that "24v" wouldn't be perfect and could potentially cause damage to any 
sensitive electronics. Diode ripple in the alternator can produce large, 
very brief (milliseconds), voltage spikes of both DC and AC current. It 
would still be wise to have a power supply device between the batteries and 
the load. It wouldn't need to be much more than a very simple voltage 
regulator. Electronics in the car don't have issues because they have built 
in power conditioning circuits. A device which has been designed with an 
external power supply is designed for a very good supply coming in and may 
not have much, or any, good power conditioning circuitry internal to the 
main device.

There's another caveat. If he's using it with the engine off (which was 
specified to me the case) this is obviously going to discharge the batteries 
by some amount. The voltage will drop as the batteries are depleted. It 
wouldn't take long before the output is less than 24v in which case a simple 
regulator can't step it back up to 24v. Again it depends on the requirements 
of the device; it may work fine at 20v, or it may quit at 23v. Plus you'd 
likely need a third battery in the morning to have enough juice to fire up 
the engine.

I've thought lots about solar powering things in a VW camper. My fiancé, my 
son, and myself lived in my Westfalia for about a year and a half. We also 
traveled to races in it for a couple years before, during, and after living 
in it until its demise when a HUGE tree fell and squished it flat. The long 
and short of it is that to be useful you'd spend a lot of money and add a 
lot of weight. I added a second battery and a couple small solar panels 
which made it good enough to run LED interior lighting at night as well as 
the water pump and the radio over a race weekend. To run much more than that 
shore power is still the most practical way by far.

-Cody Forbes (mobile)

On May 30, 2013, at 10:07 PM, "Britt Crowell" <britt at BrittCrowell.com> 
wrote:

> I agree with Tony, get rid of the 12-110-24, and just use two 12v
> batts in series, deep cycle preferably. Shouldn't any big deal to put
> in a charging system from the regular alt to charge 3 batt when driving.
> And/or a system to charge them when hooked to 120V hookups. 2 trickle
> chargers on the 120 system when at a campsite or charging going down
> the road. Little wiring and a switch or 2. 24V is 24V as long as the
> batt can push the Amps. No reason to convert to AC then back to DC
> when the numbers work out easy.
> VW Buses are part of the family! I want to put my spare 4.2L 32v V8 in
> one :-) Some good Bus pics here, I married the cute one.
> http://www.alisoncrowell.com/brittcrowell.com/2003/2003-09-05_Lake_McC
> on
> aughy/
>
> Britt
> -----------------------------------
> Or add a second battery, wired in series to the stock one for the
> purpose you need and pull from the two of them for 24V, and plenty of
> amperage so it won't go dead in short demand. This is exactly how
> older Cummins were wired, 24V starter and alt, 12V everything else.
>
> HTH,
> Tony
> **********************
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