Voltage Drop

[win222]

I recently replaced my 7 year old locator with a HDS-7 with the structure scan.

Now I keep getting a low voltage alarm on the HDS-7, which was set for 11 volts, I just changed it to 10 volts, but I'm concerned that this might damage some stuff if the voltage is too low?

Here are the voltage readings I took on my new battery:

12.6v at battery with nothing on

12.3v at battery with locators and dash on

12.3v on dash display with locators on

11.8v on HDS-7 display

If I use my bilge pump and have other lights on, the HDS-7 display can go to 10.8 volts and set off alarm, or if I use the power trim (with motor off) this also sets the alarm.

Do you think that the HDS-7 plus structure scan is drawing too much power off the wiring that was designed for older style locators? Should I run a new wire from the battery to power this stuff? I like it the way it is now so the toggle switch by the key shuts it off.

[Fishing Rhino]

The low voltage alarm is to tell you the state of your battery, not to protect the unit itself. I cannot be sure, but I have to think that the unit has protection from power surges or drops. You would not be able to change those settings.

Have your battery and charging system checked. They may be fine, but if the motor is not run enough the battery for starting and all accessories will gradually lose its charge. In that case, you'll need to charge that battery after each fishing trip to avoid the unpleasant surprise of your motor failing to start. I speak from experience.

The bilge pump will draw more amps than your HD7, and the power trim will draw more amps than the bilge pump. Running lights probably draw more amps than your Lowrance unit, but I'm not sure. Have a technician perform a load test on the battery. If you go to an Interstate battery dealer, they will usually do the test at no charge. Some of the chain auto parts stores may do it as well.

[Wayne P.]

A lot of people that upgrade to the newest equipment that requires more amps to operate find out that their boat wiring harness is just not adequate. Using the boat wiring involves several points that have resistance that causes a voltage drop. The switch is one of those along with any other connection along the wiring harness as well as the minimum wire size used. Your best option is extending the unit power cord directly to the battery with conductors larger than the cord conductors (14 ga or larger),and use a spade type fuse. Additionally, maintain your battery just like you do your trolling motor battery/s. Keep it completely charged and the terminals tight and free of corrosion.

[Todd Driscoll]

A lot of people that upgrade to the newest equipment that requires more amps to operate find out that their boat wiring harness is just not adequate. Using the boat wiring involves several points that have resistance that causes a voltage drop. The switch is one of those along with any other connection along the wiring harness as well as the minimum wire size used. Your best option is extending the unit power cord directly to the battery with conductors larger than the cord conductors (14 ga or larger),and use a spade type fuse. Additionally, maintain your battery just like you do your trolling motor battery/s. Keep it completely charged and the terminals tight and free of corrosion.

Very good advice. This is a common problem, especially with older boats. Run HDS power wires directly to battery and this problem will go away. Don't forget to include your 3 amp fuse link.

[win222]

Thanks for the advice, the battery is brand new, I replaced the starting battery with the largest multipurpose deep cycle battery.

The charging system is fine, I checked the voltage while the battery is charging and its 14 volts, so that should be ok.

I have a 3 bank on-board charger, so all the batteries get charged after each use.

I did notice that off the battery there is one 14ga wire that goes to a terminal block, that block feeds just about everything on the boat; I'm going to replace that 14ga wire with a number 8ga and see if that helps, if not, I will run a separate wire up to the locators.

[Way2slow]

Only two things cause the voltage drop you're getting. The battery is weak or you have one or more bad connections somewhere between the battery and the Sonar. The sonar only pulls 1.5 amps, that's not going to cause any significant drain. With all live well pumps running at once and all the electronics on, you are still pulling less than 20 amps, not enough to cause a notciable voltage drop on a good battery and good, clean connections. When you hit the tilt, yes you will get a little drop, but not what you say you're getting.

Start at the battery, diconnecting and cleaning every connection until it's bright metal. If you have crimp on wire connections, cut them off, clean the wire and install new ones. Many times the wire corrodes inside the terminal crimp.

Also make sure someone didn't use the accessory wire off the key switch. This is not good enough to run more than a couple of amps. You should have at least a #12 wire and prefer and #10 going directly from the battery to the Power Switch on the console and a 15 - 20 amp fuse or circuit breaker at the battery. If you know how to use a DVM, follow the voltage and fix connection that giving a drop when under a load. Be sure it's under a full load or you want get any drop.

[scrutch]

Only two things cause the voltage drop you're getting. The battery is weak or you have one or more bad connections somewhere between the battery and the Sonar. The sonar only pulls 1.5 amps, that's not going to cause any significant drain. With all live well pumps running at once and all the electronics on, you are still pulling less than 20 amps, not enough to cause a notciable voltage drop on a good battery and good, clean connections. When you hit the tilt, yes you will get a little drop, but not what you say you're getting.

Start at the battery, diconnecting and cleaning every connection until it's bright metal. If you have crimp on wire connections, cut them off, clean the wire and install new ones. Many times the wire corrodes inside the terminal crimp.

Also make sure someone didn't use the accessory wire off the key switch. This is not good enough to run more than a couple of amps. You should have at least a #12 wire and prefer and #10 going directly from the battery to the Power Switch on the console and a 15 - 20 amp fuse or circuit breaker at the battery. If you know how to use a DVM, follow the voltage and fix connection that giving a drop when under a load. Be sure it's under a full load or you want get any drop.

Don't forget to add a little dielectric grease after cleaning each connection before putting them back together. This will keep the corrosion from returning to that connection.

Permatex makes a good grease. I think they call it "Dielectric Tune Up Grease". You should be able to find it at your auto parts store.