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- Feb 1, 2015
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- 9,995
I have two deep cycle batteries on my fishing boat; one fore for the bow mount trolling motor and one aft for the transom mounted trolling motor, the sonar/GPS, and miscellaneous electronics. The aft battery also is used for starting the outboard. The aft battery has a few years on it and has been losing capacity although I'm not quite ready to chuck it yet.
The dilemma is this; if I use the rear trolling motor too much, I stand the danger of depleting the battery to the point that it won't start the outboard. While it is possible to pull start the motor, the cowling has to be removed and a length of rope used. Add to that, that it is a 50 hp. motor and takes a bit of oomph to pull start it.
A solution I tried was to purchase a booster which had rechargeable Li-ion batteries and can put just enough charge into the battery to start the motor. The problem with that was that the batteries don't do well when stored in a hot compartment on a boat. The first time that I needed it, it was totally dead.
However, it came to me last fall that I had another battery up front that I could use. I went on line and bought a DC-DC converter which would operate on a supply voltage between 8 volts and 16 volts and output a user set constant voltage between 12 volts and 60 volts and a user set constant current between 0 and 10 amps.
The idea was to provide a connecting cable between the two batteries and use one battery to boost the other. My boat has two sets of exposed charging posts so a 15' connecting cable and battery clips would complete the booster. Even a dead battery would generally have enough charge left to provide 10 minutes of charge at 10 amps which would be enough to start the outboard.
I bought a 15 ft. 16 AWG zip cord at the DIY for the input side and pulled a 3 ft length of zip cord from my collection for the output side. Two pairs of battery clips provided the connections. While it would have worked as is, I decided to add a digital volt/ammeter for monitoring the charge current and the output voltage.
The only actual machining was making a protective case for the electronics. I used a piece of .063" aluminum for the case cut into a cross configuration. Since I had eight blind cuts to make as well as a cutout for the meter, I decided to use the mill. I had eight inside corners which I filed square.
One of the case dimensions was 3" which was fortuitous was I could use a 1-2-3 block as a bending form. The other dimension was close enough to 2-3/8" that a 3/8" x 3/4" bar between the 1-2-3 blocks could be used for support. To make the bends, I clamped the blank to my RT using the two 1-2-3 blocks and strap clamps. A wood chisel allowed me enough purchase to start the bends and a piece of flat stock was used to bend the side close to 90º. A little bit of hammer work and I had nice crisp bends. The same was done to bend the 2-3/8" sides. With the box bent up, I used Miracle Rod aluminum braze to join the sides. After checking the fit of the meter bezel and the box to the DC-DC converter, I gave it a quick coat of flat black enamel.
The converter has two modes of operation, one which has an input voltage range of 8-16 volts and a second where the input voltage can range between 12 and 60 volts, selectable by jumper. I chose the former setting. A constant voltage/constant current supply functions so that neither of the settings will be exceeded. As a charge approaches completion, the charge current will be limited by the set maximum voltage and will drop to a lower value. I set the output voltage at 15 volts which is a safe short term charge voltage for a lead acid battery regardless of state of charge. I set the charge current at 10 amps.
Piece of mind....priceless!
The dilemma is this; if I use the rear trolling motor too much, I stand the danger of depleting the battery to the point that it won't start the outboard. While it is possible to pull start the motor, the cowling has to be removed and a length of rope used. Add to that, that it is a 50 hp. motor and takes a bit of oomph to pull start it.
A solution I tried was to purchase a booster which had rechargeable Li-ion batteries and can put just enough charge into the battery to start the motor. The problem with that was that the batteries don't do well when stored in a hot compartment on a boat. The first time that I needed it, it was totally dead.
However, it came to me last fall that I had another battery up front that I could use. I went on line and bought a DC-DC converter which would operate on a supply voltage between 8 volts and 16 volts and output a user set constant voltage between 12 volts and 60 volts and a user set constant current between 0 and 10 amps.
600W DC-DC Step Up Boost Buck Voltage Converter High Power Supply Module 16A | eBay
(Input 36V 10A=360W, input 48V 10A=480W, input 60V 10A=600W. Module nature: non-isolated boost module (BOOST) (can't step down). Output current: 12A MAX. More, the lower the charging current.). The circuit structure of the boost module cannot be adjusted in a short-circuit mode.
www.ebay.com
The idea was to provide a connecting cable between the two batteries and use one battery to boost the other. My boat has two sets of exposed charging posts so a 15' connecting cable and battery clips would complete the booster. Even a dead battery would generally have enough charge left to provide 10 minutes of charge at 10 amps which would be enough to start the outboard.
I bought a 15 ft. 16 AWG zip cord at the DIY for the input side and pulled a 3 ft length of zip cord from my collection for the output side. Two pairs of battery clips provided the connections. While it would have worked as is, I decided to add a digital volt/ammeter for monitoring the charge current and the output voltage.
Mini DC 100V 10A Digital Voltmeter Ammeter Blue Red LED Volt Amp Meter Gauge US | eBay
Current Testing range: DC 0 - 10A. - Display: 0.28" digital tube, Two color blue and red. You will be pleasantly surprised by our service. - Got a problem?. No Problem. This can only delay our service.
www.ebay.com
The only actual machining was making a protective case for the electronics. I used a piece of .063" aluminum for the case cut into a cross configuration. Since I had eight blind cuts to make as well as a cutout for the meter, I decided to use the mill. I had eight inside corners which I filed square.
One of the case dimensions was 3" which was fortuitous was I could use a 1-2-3 block as a bending form. The other dimension was close enough to 2-3/8" that a 3/8" x 3/4" bar between the 1-2-3 blocks could be used for support. To make the bends, I clamped the blank to my RT using the two 1-2-3 blocks and strap clamps. A wood chisel allowed me enough purchase to start the bends and a piece of flat stock was used to bend the side close to 90º. A little bit of hammer work and I had nice crisp bends. The same was done to bend the 2-3/8" sides. With the box bent up, I used Miracle Rod aluminum braze to join the sides. After checking the fit of the meter bezel and the box to the DC-DC converter, I gave it a quick coat of flat black enamel.
The converter has two modes of operation, one which has an input voltage range of 8-16 volts and a second where the input voltage can range between 12 and 60 volts, selectable by jumper. I chose the former setting. A constant voltage/constant current supply functions so that neither of the settings will be exceeded. As a charge approaches completion, the charge current will be limited by the set maximum voltage and will drop to a lower value. I set the output voltage at 15 volts which is a safe short term charge voltage for a lead acid battery regardless of state of charge. I set the charge current at 10 amps.
Piece of mind....priceless!
