NEED VOLTAGE REGULATOR 14V 40 AMPS

[Ducky_Doug]

After starting my Chevy Duramax Deisel the alternator puts out over 15.5V
and then drops down after a few minutes. This caused my 400W Portawatt
inverter to drop out on high voltage. Is there a simple circuit using
mosfets, 2n3055, etc and using readily available parts to drop the voltage
down to <15V. Regulation isn't neccessary just want to keep the voltage
between the inverters shutdown setpoints.

 

[CBarn24050]

Your alternator should not put out that much, you need a new voltage regulator
or maybe a new battery.

 

[Fred Bloggs]

After starting my Chevy Duramax Deisel the alternator puts out over 15.5V
and then drops down after a few minutes. This caused my 400W Portawatt
inverter to drop out on high voltage. Is there a simple circuit using
mosfets, 2n3055, etc and using readily available parts to drop the voltage
down to <15V. Regulation isn't neccessary just want to keep the voltage
between the inverters shutdown setpoints.

View in a fixed-width font such as Courier.



50A L
p-ch ====
Vbatt o--+---------+ +------------+--uuuu---+--->
| v | | |
| ---- - |
| | ^sd |
+--[r]-----+--------+ - |
| | | +---+
[r] | | | |
| | | | |
| | | | |
+-------+------+ | | | ===
| | | | | | |
- [r] | | | [r] |
^ zd | | | | | |
- +----|\| | | +---|-+
| | |-\ | | | | |
| [r] | >---+ | [r] | |
| | +-|+/ comptor | | | |
| | | |/| | | | |
| | | | | | | |
+---+-------+--|---+----------+-----+---+ |
| | |
--- +--------------------------+
///

 

[Tam/WB2TT]

After starting my Chevy Duramax Deisel the alternator puts out over 15.5V
and then drops down after a few minutes. This caused my 400W Portawatt
inverter to drop out on high voltage. Is there a simple circuit using
mosfets, 2n3055, etc and using readily available parts to drop the voltage
down to <15V. Regulation isn't neccessary just want to keep the voltage
between the inverters shutdown setpoints.

Where is the inverter connected? If near the alternator, connect it to the
battery terminals; BOTH negative and positive leads. In my car, the battery
is under the rear seat. I often see over 15 volts under the hood/ at the
cigarette lighter. No damage to the battery in over 4 years.

Tam

 

[Ducky_Doug]

Thank you for your responses. A #1 welding cable runs from the engine
batteries and feeds the 400 watt inverter in the cab. The buss then
continues on to feed a 2500 watt inverter and 400 amphr deep cycle type
aux. batteries in the back of the service truck. This setup is duplicated
in two of our other sevice trucks and they also suffer from shut down of
the cab inverter which runs a computer and test equipment. The 2.5K
inverter is not a concern. This only happens on our deisel equiped trucks
and GM assures us that this higher first recharge voltage is normal to a
deisel due to its high output alternator. A resistive device is out as it
only acts as a current limiter.

 

[Winfield Hill]

Fred Bloggs wrote...

"Ducky Doug" Braun wrote ...

CBarn24050 and Tam/WB2TT pointed out that if the Portawatt inverter
were wired directly across the 12V battery terminals, then voltages
over 15V shouldn't occur. Can Ducky Doug comment on this?

50A L
p-ch ====
Vbatt o--+---------+ +------------+--uuuu---+--->
| v | | |
| ---- - |
| | ^sd |
+--[r]-----+--------+ - |
| | | +---+
[r] | | | |
| | | | |
+-------+------+ | | | ===
| | | | | | |
- [r] | | | [r] |
^ zd | | | | | |
- +----|\| | | +---|-+
| | |-\ | | | | |
| [r] | >---+ | [r] | |
| | +-|+/ comptor | | | |
| | | |/| | | | |
+---+-------+--|---+----------+-----+---+ |
| | |
--- +--------------------------+
///

Hmm, a bit easier said than done. What's a good choice for the
p-channel MOSFET, which should have Ron below 5 milliohms? This
FET will have a rather high gate capacitance, mandating a proper
gate driver. At which point the designer will begin considering
the attractive n-channel MOSFET plus driver solutions.

And the low-resistance 50A inductor will be fun as well. Using
a low-inductance part will help the designer to meet the low-
resistance requirement, but this will mandate higher switching
frequencies, which in turn mandates a serious FET gate driver.

 

[Fred Bloggs]

Fred Bloggs wrote...

"Ducky Doug" Braun wrote ...

CBarn24050 and Tam/WB2TT pointed out that if the Portawatt inverter
were wired directly across the 12V battery terminals, then voltages
over 15V shouldn't occur. Can Ducky Doug comment on this?

50A L
p-ch ====
Vbatt o--+---------+ +------------+--uuuu---+--->
| v | | |
| ---- - |
| | ^sd |
+--[r]-----+--------+ - |
| | | +---+
[r] | | | |
| | | | |
+-------+------+ | | | ===
| | | | | | |
- [r] | | | [r] |
^ zd | | | | | |
- +----|\| | | +---|-+
| | |-\ | | | | |
| [r] | >---+ | [r] | |
| | +-|+/ comptor | | | |
| | | |/| | | | |
+---+-------+--|---+----------+-----+---+ |
| | |
--- +--------------------------+
///

Hmm, a bit easier said than done. What's a good choice for the
p-channel MOSFET, which should have Ron below 5 milliohms? This
FET will have a rather high gate capacitance, mandating a proper
gate driver. At which point the designer will begin considering
the attractive n-channel MOSFET plus driver solutions.

And the low-resistance 50A inductor will be fun as well. Using
a low-inductance part will help the designer to meet the low-
resistance requirement, but this will mandate higher switching
frequencies, which in turn mandates a serious FET gate driver.

Not to mention blowing out the inverter filter capacitors with excessive
ripple current....

 

[Kim Clay]

After starting my Chevy Duramax Deisel the alternator puts out over 15.5V
and then drops down after a few minutes. This caused my 400W Portawatt
inverter to drop out on high voltage. Is there a simple circuit using
mosfets, 2n3055, etc and using readily available parts to drop the voltage
down to <15V. Regulation isn't neccessary just want to keep the voltage
between the inverters shutdown setpoints.

How about a single diode in series with the Pos input of the 400W
inverter (with large heat sink). Diode will drop 0.7V @ 40A= 28W of heat
to get rid of.

Maybe 1/2 of a battery isolator or use both diodes of a 2 battery
isolator & strap both diodes in parallel. You will need good air
circulation to dump the heat.

The inverter may drop out quickly due to low volts if used without the
engine running. The diode will drop a constant 0.7V or so. If the
inverter was set to dropout at 10.5V it would now drop out at ~11.2V.

In your case this may not be a problem.

Just an idea - Kim

 

[Winfield Hill]

Winfield Hill wrote...

Fred Bloggs wrote...

50A L
p-ch ====
Vbatt o--+---------+ +------------+--uuuu---+--->
| v | | |
| ---- - |
| | ^sd |
+--[r]-----+--------+ - |
| | | +---+
[r] | | | |
| | | | |
+-------+------+ | | | ===
| | | | | | |
- [r] | | | [r] |
^ zd | | | | | |
- +----|\| | | +---|-+
| | |-\ | | | | |
| [r] | >---+ | [r] | |
| | +-|+/ comptor | | | |
| | | |/| | | | |
+---+-------+--|---+----------+-----+---+ |
| | |
--- +--------------------------+
///

Hmm, a bit easier said than done. What's a good choice for
the p-channel MOSFET, which should have Ron below 5 milliohms?
This FET will have a rather high gate capacitance...

A few possibilities (through-hole packages only). Note the
high gate capacitances.

part Vdss Ron Ciss
number ohms pF
------ ---- ----- ----
IRF9540 100V 0.2 1400
IRF9Z30 50V 0.14 900
IRF9Z34 60V 0.14 1100
IRF5305 55V 0.06 1200
FQA47P06 60V 0.026 3600
NDP6030PL 30V 0.025 1570
MTP50P03 30V 0.025 4900
SPP80P06 60V 0.023 5033
IRF4905 55V 0.020 3400
2SJ555 60V 0.017 4100
STP80PF55 55V 0.016 5500
SUP90P06-09L 60V 0.015 9200
FX70UMJ 30V 0.012 11140
SUP75P05-08 55V 0.008 8500

 

[Tony Williams]

Thank you for your responses. A #1 welding cable runs from the
engine batteries and feeds the 400 watt inverter in the cab. The
buss then continues on to feed a 2500 watt inverter and 400 amphr
deep cycle type aux. batteries in the back of the service truck.
This setup is duplicated in two of our other sevice trucks and
they also suffer from shut down of the cab inverter which runs a
computer and test equipment.

It might be better to route directly from the engine
batteries to the aux battery. Then distribute from
the aux battery to the inverters. In this way the aux
battery has a better chance of functioning as an
additional shunt voltage regulator.

If the problem still persists then maybe a bit of
brute force and ignorance would solve the problem.

Have two meaty diodes in series with the supply to
the 400W device, with automobile-type high current
contactors holding shorts across the diodes. If the
upstream voltage exceeds 14.5V then unshort one diode,
and unshort the other above about 15.5V. Have about
a 0.5V comparator hysteresis. Maybe cool the diode
heatsinks with a 12V fan when a diode is unshorted.