12V Regulation

N

nate chase

New member
Apr 26, 1999
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Just purchased an DC to AC inverter off the internet (Netmarket.com). Got a
VERY good deal on a small 600 watt one ($80). What I wanted to do was run a
laptop up in the cockpit of my '75 GB with mapping and GPS (Global
Positioning Satellite) software. The inverter will help the laptop run off
AC instead of it's batteries. The software is really great if you haven't
seen it goto http://www.travroute.com/products/copilot/default.html and take
a demo.
Anyways, the inverter runs right off the engine battery but it has low (10v)
and high (14.7v) voltage shutdown to protect it. My problem is the
alternator is putting out 15V almost all the the time and this shuts down
the inverter (and the laptop). I thoght about adding a 12V regulator between
the battery and inverter. Anyone got any better ideas such as a way to
adjust the alternator output slightly lower? Any thoughts would be
appreciated...
Nate Chase, '75 Glenbook, Omaha, NE
 
Nate --

If you have the stock 10 or 27-SI Delco alternator, you may need to replace
the internal voltage regulator to get your voltage within tolerance. High
voltage is often caused by an internal short in the regulator. These
Delcotrons use an internal IC based voltage regulator that is not
adjustable.

You should not have to use a voltage regulator ahead of your inverter.
Nominal battery voltage should be 13.8v when going down the road.

Also, Delcotrons often reach a slightly higher 'eagle' voltage when cold
that is much higher than their output voltage at operating temp. You might
consider warming everything up thoroughly before opening the tool box (and
the alternator).

Hope this helps.

Mark Grady
'77 Kingsley

PS - You'll get much longer life out of your batteries, headlamps, HEI
module and refrigerator if you get your voltage in the right range.

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailto:owner-gmcmotorhome]On Behalf Of Nate Chase
> Sent: Tuesday, April 27, 1999 9:01 AM
> To: GMC (E-mail)
> Subject: GMC: 12V Regulation
>
>
> Just purchased an DC to AC inverter off the internet
> (Netmarket.com). Got a
> VERY good deal on a small 600 watt one ($80). What I wanted to do
> was run a
> laptop up in the cockpit of my '75 GB with mapping and GPS (Global
> Positioning Satellite) software. The inverter will help the laptop run off
> AC instead of it's batteries. The software is really great if you haven't
> seen it goto
> http://www.travroute.com/products/copilot/default.html and take
> a
> demo.
> Anyways, the inverter runs right off the engine battery but it
> has low (10v)
> and high (14.7v) voltage shutdown to protect it. My problem is the
> alternator is putting out 15V almost all the the time and this shuts down
> the inverter (and the laptop). I thoght about adding a 12V
> regulator between
> the battery and inverter. Anyone got any better ideas such as a way to
> adjust the alternator output slightly lower? Any thoughts would be
> appreciated...
> Nate Chase, '75 Glenbook, Omaha, NE
>
 
>Anyways, the inverter runs right off the engine battery ....

Don't run the inverter off of the engine battery. An engine battery can
only withstand a few charge/discharge cycles before its shot. Much better
of running the inverter off of the house battery.

>but it has low (10v)
>and high (14.7v) voltage shutdown to protect it.

This will probably not be a problem if you connect to the house battery.
The longer cable lengths will likely cause enough voltage drop to keep you
out of trouble. But, if you still have high voltage problems, add a battery
isolator between the battery and the inverter. It will give you about a .7v
drop. Be sure to use one that is large enough (like twice the current
rating of your inverter) and be sure to use big enough wire. A 600 watt
inverter will draw something like 60+ amps at full load. I would suggest
6awg wire. Its a little overkill on current capacity but it will have less
voltage drop so when you are parked you will be less likely to have the
inverter drop out on you.

>My problem is the
>alternator is putting out 15V almost all the the time

Thats pretty close to normal. The alternator output voltage will be a
function of temperature (colder is higher) and the voltage drop in your
electrical system. The alternator regulates the voltage at the field
terminal not at the output terminal. I think the range is typically 13.5
(hot) to 14.5 (cold) for a perfect alternator. But its not unusual to get a
few tenths drop between the battery and the field terminal. So the battery
voltages are usually a bit higher.

Hope that helps.

Dave
73 Sequoia
 
You can buy a small DC voltage regulator to run the lap top and similar
devices that need a constant DC. Radio shack should have one. Why not run
the laptop off DC instead of converting it to AC than back to DC?

>Just purchased an DC to AC inverter off the internet (Netmarket.com). Got a
>VERY good deal on a small 600 watt one ($80). What I wanted to do was run a
>laptop up in the cockpit of my '75 GB with mapping and GPS (Global
>Positioning Satellite) software. The inverter will help the laptop run off
>AC instead of it's batteries. The software is really great if you haven't
>seen it goto http://www.travroute.com/products/copilot/default.html and take
>a demo.
>Anyways, the inverter runs right off the engine battery but it has low (10v)
>and high (14.7v) voltage shutdown to protect it. My problem is the
>alternator is putting out 15V almost all the the time and this shuts down
>the inverter (and the laptop). I thoght about adding a 12V regulator between
>the battery and inverter. Anyone got any better ideas such as a way to
>adjust the alternator output slightly lower? Any thoughts would be
>appreciated...
>Nate Chase, '75 Glenbook, Omaha, NE
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
"The beautiful Mohawk Vally"
 
As to Inverters, suggest you find the biggest cable you can... starting with a
number 1 or so. I think the bigger will be safer. I have a 1500 w and used a
#1 cable as it is possible to have some 100 to 150A running through it.
al

> >Anyways, the inverter runs right off the engine battery ....
>
> Don't run the inverter off of the engine battery. An engine battery can
> only withstand a few charge/discharge cycles before its shot. Much better
> of running the inverter off of the house battery.
>
> >but it has low (10v)
> >and high (14.7v) voltage shutdown to protect it.
>
> This will probably not be a problem if you connect to the house battery.
> The longer cable lengths will likely cause enough voltage drop to keep you
> out of trouble. But, if you still have high voltage problems, add a battery
> isolator between the battery and the inverter. It will give you about a .7v
> drop. Be sure to use one that is large enough (like twice the current
> rating of your inverter) and be sure to use big enough wire. A 600 watt
> inverter will draw something like 60+ amps at full load. I would suggest
> 6awg wire. Its a little overkill on current capacity but it will have less
> voltage drop so when you are parked you will be less likely to have the
> inverter drop out on you.
>
> >My problem is the
> >alternator is putting out 15V almost all the the time
>
> Thats pretty close to normal. The alternator output voltage will be a
> function of temperature (colder is higher) and the voltage drop in your
> electrical system. The alternator regulates the voltage at the field
> terminal not at the output terminal. I think the range is typically 13.5
> (hot) to 14.5 (cold) for a perfect alternator. But its not unusual to get a
> few tenths drop between the battery and the field terminal. So the battery
> voltages are usually a bit higher.
>
> Hope that helps.
>
> Dave
> 73 Sequoia
 
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