Adjustable voltage booster?

[Glenn Ashmore]

I have lucked up on a Ecotech high output emergency vehicle alternator for
the boat project. This hyper expensive alternator puts out full output at
very low RPM which makes it very attractive for charging my bank of four L16
batteries. The problem is it is designed to output a constant 14.2V to
power all the lights and equipment a big fire truck needs. That is fine for
bulk and absorption charging but can fry the batteries once they get closer
to full charge. This alternator is rather unique. It has one section that
is permanent magnets and a second that is a field coil. When the magnets
can't supply the required current the field coil kicks in. When the magnets
output to much current the field coil is reversed to reduce output.
Obviously I can't use a normal external "smart" regulator so I need to find
another way to reduce the output voltage.

It does have a voltage sense line that goes to the battery which with some
experimentation I found that if you increase the voltage on that line the
alternator is fooled into reducing the output voltage by about the same
amount.

I need a circuit that I can switch into the sense line to boost the voltage
by about 1V so the alternator will drop down to a safe 13.2V when I am
motoring for a long time.

Any suggestions?.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

 

[Glenn Ashmore]

---
You bet!

If you can afford to be building a boat you can surely afford my
design services. Email me if you're interested.

On the contrary. That is exactly the reason I can't afford it.

Sorry, I had thought that this might be a rather simple question so I asked
here. Perhaps I should have asked in s.e.design where everyone was most
helpful last year in the development of my remote lighting and watermaker
controls.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

 

[John Fields]

I have lucked up on a Ecotech high output emergency vehicle alternator for
the boat project. This hyper expensive alternator puts out full output at
very low RPM which makes it very attractive for charging my bank of four L16
batteries. The problem is it is designed to output a constant 14.2V to
power all the lights and equipment a big fire truck needs. That is fine for
bulk and absorption charging but can fry the batteries once they get closer
to full charge. This alternator is rather unique. It has one section that
is permanent magnets and a second that is a field coil. When the magnets
can't supply the required current the field coil kicks in. When the magnets
output to much current the field coil is reversed to reduce output.
Obviously I can't use a normal external "smart" regulator so I need to find
another way to reduce the output voltage.

It does have a voltage sense line that goes to the battery which with some
experimentation I found that if you increase the voltage on that line the
alternator is fooled into reducing the output voltage by about the same
amount.

I need a circuit that I can switch into the sense line to boost the voltage
by about 1V so the alternator will drop down to a safe 13.2V when I am
motoring for a long time.

Any suggestions?.

 

[Don Young]

I have lucked up on a Ecotech high output emergency vehicle alternator for
the boat project. This hyper expensive alternator puts out full output at
very low RPM which makes it very attractive for charging my bank of four
L16
batteries. The problem is it is designed to output a constant 14.2V to
power all the lights and equipment a big fire truck needs. That is fine
for
bulk and absorption charging but can fry the batteries once they get
closer
to full charge. This alternator is rather unique. It has one section that
is permanent magnets and a second that is a field coil. When the magnets
can't supply the required current the field coil kicks in. When the
magnets
output to much current the field coil is reversed to reduce output.
Obviously I can't use a normal external "smart" regulator so I need to
find
another way to reduce the output voltage.

It does have a voltage sense line that goes to the battery which with some
experimentation I found that if you increase the voltage on that line the
alternator is fooled into reducing the output voltage by about the same
amount.

I need a circuit that I can switch into the sense line to boost the
voltage
by about 1V so the alternator will drop down to a safe 13.2V when I am
motoring for a long time.

Any suggestions?.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

I think the easiest method might be to add one or more diodes in series with
the output and connect the sense line directly to the alternator output. The
battery isolators used with dual battery setups might be suitable. If the
regulator circuitry is accessible modifying it would be very easy. There are
also electronic circuits that will also do this job but would take a little
design work.

Don Young

 

[[email protected]]

since this unit has a sense line, is there not also a calibration pot
somewhere on it that you can adjust down to suit your needs? To boost
by 1 volt means you'll need to build a power supply that switched the
DC across an inductor to boost up the voltage, then rectify it again
and add it to your original 13.2 volts. seems to me that a circuit that
would use a couple hi current diodes in series with the alternators
output would work for the motoring, and then use a high current relay
to enguage and bypass the diodes when the load increases to a certain
threshold point of your choosing.

good luck

 

[Ross Herbert]

I have lucked up on a Ecotech high output emergency vehicle alternator for
the boat project. This hyper expensive alternator puts out full output at
very low RPM which makes it very attractive for charging my bank of four L16
batteries. The problem is it is designed to output a constant 14.2V to
power all the lights and equipment a big fire truck needs. That is fine for
bulk and absorption charging but can fry the batteries once they get closer
to full charge. This alternator is rather unique. It has one section that
is permanent magnets and a second that is a field coil. When the magnets
can't supply the required current the field coil kicks in. When the magnets
output to much current the field coil is reversed to reduce output.
Obviously I can't use a normal external "smart" regulator so I need to find
another way to reduce the output voltage.

Specs on the Echo-Tech alternator
http://www.eco-techalternators.com/pdf/Specificationsheet-14VR1.1.pdf

Since the alternator has a 14.4V set point a battery will not "fry"
when fully charged because the battery voltage and the alternator
voltage will be equal at the set point, hence zero charging current
will be the case when the battery is fully charged.

The whole idea of having this alternator in emergency vehicles is to
ensure that the battery is not discharged by heavy loading at low rpm
such as when idling with pumps, radio etc going flat chat. The
alternator supplies the bulk of the load at such times with the
battery supplying instantaneous short duration peaks. However, when
the vehicle is cruising and the battery loading is light the
alternator simply maintains the battery voltage at 14.4V without
pushing undue charging current into it. I'm sure that the battery on
emergency vehicles would also be "fried" if your assumption was
correct, and that really would set a new standard for the word
"emergency". They would be on the radio requesting a new battery
during an emergency if this was the case.

I doubt that you would have any worries with the alternator as is.

 

[Ross Herbert]

Specs on the Echo-Tech alternator
http://www.eco-techalternators.com/pdf/Specificationsheet-14VR1.1.pdf

Since the alternator has a 14.4V set point a battery will not "fry"
when fully charged because the battery voltage and the alternator
voltage will be equal at the set point, hence zero charging current
will be the case when the battery is fully charged.

The whole idea of having this alternator in emergency vehicles is to
ensure that the battery is not discharged by heavy loading at low rpm
such as when idling with pumps, radio etc going flat chat. The
alternator supplies the bulk of the load at such times with the
battery supplying instantaneous short duration peaks. However, when
the vehicle is cruising and the battery loading is light the
alternator simply maintains the battery voltage at 14.4V without
pushing undue charging current into it. I'm sure that the battery on
emergency vehicles would also be "fried" if your assumption was
correct, and that really would set a new standard for the word
"emergency". They would be on the radio requesting a new battery
during an emergency if this was the case.

PS: Sorry, they would be on the mobile phone cos the radio wouldn't
work due to a fried battery

 

[Glenn Ashmore]

Specs on the Echo-Tech alternator
http://www.eco-techalternators.com/pdf/Specificationsheet-14VR1.1.pdf

Since the alternator has a 14.4V set point a battery will not "fry"
when fully charged because the battery voltage and the alternator
voltage will be equal at the set point, hence zero charging current
will be the case when the battery is fully charged.

The whole idea of having this alternator in emergency vehicles is to
ensure that the battery is not discharged by heavy loading at low rpm
such as when idling with pumps, radio etc going flat chat. The
alternator supplies the bulk of the load at such times with the
battery supplying instantaneous short duration peaks. However, when
the vehicle is cruising and the battery loading is light the
alternator simply maintains the battery voltage at 14.4V without
pushing undue charging current into it. I'm sure that the battery on
emergency vehicles would also be "fried" if your assumption was
correct, and that really would set a new standard for the word
"emergency". They would be on the radio requesting a new battery
during an emergency if this was the case.

I doubt that you would have any worries with the alternator as is.

The problem is wet cell batteries start outgassing at 14.2V. That is not
really a problem with an emergency vehicle that only runs for a few hours a
day without any accessories working but a cruising sailboat may motor for
several days at a time.

It looks like the diode idea might be the answer with a relay to switch them
in and switch the sense line from the battery to the alternator output.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

 

[Ross Herbert]

The problem is wet cell batteries start outgassing at 14.2V. That is not
really a problem with an emergency vehicle that only runs for a few hours a
day without any accessories working but a cruising sailboat may motor for
several days at a time.

It looks like the diode idea might be the answer with a relay to switch them
in and switch the sense line from the battery to the alternator output.

I assume that you read the literature on the Eco-Tech website eg,
http://www.eco-techalternators.com/pdf/Eco-Tech305-IAlternators-240AmpsatIdle!.pdf

Note that at the bottom of page 1 it says that the output voltage when
fitted to a vehicle is regulated to 14.1V.

On page 2 under Equipment Savings it refers to the non-requirement for
load shedding devices. This would seem to indicate that overcharging a
battery will not happen.

If you have any concerns then it might be a good idea to explain your
situation to Eco-tech via http://www.eco-techalternators.com/order.htm
and see what they have to say. If you don't need to do anything then
you might be worrying without good cause.

 

[Rich Grise]

I have lucked up on a Ecotech high output emergency vehicle alternator for
the boat project. This hyper expensive alternator puts out full output at
very low RPM which makes it very attractive for charging my bank of four L16
batteries. The problem is it is designed to output a constant 14.2V to
power all the lights and equipment a big fire truck needs. That is fine for
bulk and absorption charging but can fry the batteries once they get closer
to full charge. This alternator is rather unique. It has one section that
is permanent magnets and a second that is a field coil. When the magnets
can't supply the required current the field coil kicks in. When the magnets
output to much current the field coil is reversed to reduce output.
Obviously I can't use a normal external "smart" regulator so I need to find
another way to reduce the output voltage.

It does have a voltage sense line that goes to the battery which with some
experimentation I found that if you increase the voltage on that line the
alternator is fooled into reducing the output voltage by about the same
amount.

I need a circuit that I can switch into the sense line to boost the voltage
by about 1V so the alternator will drop down to a safe 13.2V when I am
motoring for a long time.

Look for an RV show, or RV dealer near you, and ask for an "isolation
diode". In vehicles with a separate engine battery and "utility" battery
(like a fire truck - in RVs, they call it the "house" battery), they
boost the alternator output voltage by the Vf of a diode, so that the
alternator can charge both batteries but their outputs are isolated.

Depending on what kind of amps you're going for, you could be looking
at some pretty hefty diodes, e.g.:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=398254&Row=43989&Site=US

If you're only charging one battery, you only need one diode, or you could
try fiddling with the regulator, if you're brave and know what you're
doing.

Good Luck!
Rich

 

[Rich Grise]

On the contrary. That is exactly the reason I can't afford it.

Sorry, I had thought that this might be a rather simple question so I asked
here. Perhaps I should have asked in s.e.design where everyone was most
helpful last year in the development of my remote lighting and watermaker
controls.

Don't worry. This is the basics group - no question is unwelcome here.[1]

We try to keep the signal-to-noise ratio up, to give newbies someplace
where they'll feel welcome no matter how new they are.

Occasionally, one of the regulars forgets which group he's addressing
- please ignore them.

Have Fun!
Rich
[1] well, as long as it's got electronics in it somewhere. ;-)

 

[Don Young]

The problem is wet cell batteries start outgassing at 14.2V. That is not
really a problem with an emergency vehicle that only runs for a few hours
a day without any accessories working but a cruising sailboat may motor
for several days at a time.

It looks like the diode idea might be the answer with a relay to switch
them in and switch the sense line from the battery to the alternator
output.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Switching the diode(s) and sense line should not be necessary. The
alternator can still provide full current output when the battery is below
the regulator control point.

Don Young

 

[jasen]

I need a circuit that I can switch into the sense line to boost the voltage
by about 1V so the alternator will drop down to a safe 13.2V when I am
motoring for a long time.

an LM555 powered from the battery (via the ignition switch) that drives
a capacitor-diode pump (cockroft-walton multiplier) to produce a higher
voltage (about 26V), this higer voltage is the regulated using a LM317
with the ref pin connected to a voltage divider (across the battery supply)
that puts it 0.2V below a your ideal voltage. the altenators sense line
gets connected to the 317 output which will be about 1V above battery
voltage.

if it breaks your battery will probably get baked, so check the
data sheets etc for how to use them, and make it solid and waterproof.

Bye.
Jasen

 

[Glenn Ashmore]

an LM555 powered from the battery (via the ignition switch) that drives
a capacitor-diode pump (cockroft-walton multiplier) to produce a higher
voltage (about 26V), this higher voltage is the regulated using a LM317
with the ref pin connected to a voltage divider (across the battery
supply)
that puts it 0.2V below a your ideal voltage. the alternators sense line
gets connected to the 317 output which will be about 1V above battery
voltage.

if it breaks your battery will probably get baked, so check the
data sheets etc for how to use them, and make it solid and waterproof.

Thanks, I will do some research on that idea.

I am getting conflicting information from the battery makers. All the books
and Surrette, the super high quality deep cycle maker, insists that wet cell
batteries should not be held above 13.2V for more than 4 hours after
reaching 85% charged. The Trojan, #2 in deep cycle wet cells, engineers
say 14.1 is OK as long as the amperage does not exceed 10 to 15A. If that
is true the stock regulator should be OK.

Time to delve into the physics of battery charging .

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

 

[Ross Herbert]

Thanks, I will do some research on that idea.

I am getting conflicting information from the battery makers. All the books
and Surrette, the super high quality deep cycle maker, insists that wet cell
batteries should not be held above 13.2V for more than 4 hours after
reaching 85% charged. The Trojan, #2 in deep cycle wet cells, engineers
say 14.1 is OK as long as the amperage does not exceed 10 to 15A. If that
is true the stock regulator should be OK.

Time to delve into the physics of battery charging .

Glenn, I just re-read your original postto check on the type of
battery you were charging and noted there were 4 x L16 - which appear
to be aimed at renewable energy (solar) applications. You are planning
to use them in a marine environment.

Rolls/Surrette recommendation concerning the use of their solar
batteries in mobile and marine situations appears at the top of this
webpage http://www.semarine.com/SolarBatteries/SolarBatteries.shtml

Other than that, info gleaned from the Trojan website seems to
indicate that their batteries should be charged on a daily basis at
14.8V (as would be the case for a vehicle), 13.2V float charging, and
15.5V equalizing (not really applicable for your case).

Since the Eco-Tech alternator is a constant voltage regulated charger
set at 14.4V, - and based on the manf's document I referred to earlier
saying that a vehicle battery would read 14.1V fully charged, I can't
see why your batteries would be fried. If it were me, I would simply
try it by taking the boat out for a day and checking to see if
excessive gassing occurred. One trip would not cause any damage, and
if they did gas, then you could add your diode dropper or whatever.
Why do it if it isn't necessary?