Hi Guys,
Things went South with the paper design for a while but we are back on track
with our product.
Originally the output current rating was 5A at 13.8V. I thought this may be a
bit low for a 400AH 1/2 bank
so I doubled it to 10A. It was easy to re-design the transformer and pick a
lower resistance FET and a
higher current rated Schottky diode but the current sense resistor dissipation
increasing from 5W to 10W
screwed up the power dissipation budget for the board as well as the box.
Currently the plan is to use a
ferrite core current transformer with a 20:1 ratio to reduce the power
dissipation at the sense resistor
to a low 0.5W and give us higher efficiency.
Preliminary Specifications :
Input voltage range : 8.4Vdc to 15Vdc.
Output current rating : 10Adc (Vin=12V, Vout=13.8V) TBD based on operating
temperature range.
Minimum efficiency : 85% (Vin=12V, Vout=13.8V, Iout=10Adc)
Operating temperature range : TBD
ON/OFF toggle switch. (Left side of the box. Up is ON)
EQUALIZE/FLOAT SWITCH (Right side of the box. Up is EQUALIZE)
Three green LED's to show charge rate. (Approx 25%, 50%, 100%)
Wiring through 4 X 16AWG wires to a 4 gang terminal block at the bottom
surface.
Internal Fuses
Internally adjustable float level (Pre calibrated to 13.8V adjustable to
12.5Vmax fully CCW to 14Vmin fully CW)
Internally adjustable equilize level (Pre calibrated to 14.8V adjustable to
13.5Vmax fully CCW to 15Vmin fully CW)
Bulkhead mount box (Mounting hole pattern (4" X 6") Hardware TBD
Height : 5.5" max
Width : 8" max
Depth : 2.5" max
Waterproof to 10ft depth TBD
Price target $300
Functional Description (copied and pasted from a previous e-mail)
1. Start the engine, and begin charging. (with the battery switch in "BOTH"
position)
Continue charging until the battery voltage reaches the maximum and the
regulator
begins to taper down the charge current.
2. Shutdown the engine
Shutdown when the current drops to 80% (recommended) or 30% or 99%.
Just know that when the charge current begins to taper down, the efficiency
of the charging process also begins to go down.
3. Flip the battery switch to "BANK 1" on odd days and to "BANK 2" on even days.
The Equalizer LED's will first indicate "CHARGING" and then "FLOATING" and then
"CHARGED".
The cycle timing will depend on the Ampere Hour rating and condition of your
batteries.
4. Flip the battery switch back to "BOTH" position.
I am building the prototype, to make sure it meets the latest specs.
I would like to send this prototype (free of charge) to a volunteer to validate
my (DVT) design
verification testing. The DVT validation volunteer can keep the prototype and
also get
a 50% discount on a deliverable unit if he/she wants it as a spare.
The DVT volunteer should tell me the A/H rating of his dual house banks, and
the diameter of the
terminal studs behind his battery switch, and how long wires he needs from
where he wants to
install the equalizer to the back side of the battery switch.
Again, please let me know if you disagree with any of these specifications.
Now is the time to evaluate and implement the suggested changes.
Now I have to talk my wife into spending $3,000 for a new scope and a current
probe to do the lab testing.
You guys are killing me :-)
Wait, I remember Ben Okopnik said he would buy the DC/DC. I wish he would give
me a part number !
Happy sailing
Ahmet Erkan
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