low battery display on autopilot

[Earthcandys]

I have a Hunter 36 with autopilot. While using it last week I suddenly got a low battery warning on the display and autopilot stopped working. I have checked my batteries and the voltage is good and stable. When I turn it off and back on, it works for about 15 secs and then displays low battery and stops again. Any ideas?

Ron

 

[justsomeguy]

Any ideas?

Check wiring?

 

[smokey73]

What other loads were you running at the same time? I had a similar problem and have traced it to voltage loss between the battery and the electrical panel. "So - the simple answer check wiring" is probably correct. You have something dropping the voltage when under a relatively high current load such that you are seeing a lower voltage at the autopilot than the battery voltage.

 

[Captain Larry-DH]

You have a high-resistance connection somewhere, likely on the negative side. Look for corrosion. Open EVERY connection and screw terminal, test the strength of every crimp connection. retighten. If you don’t find anything, re-crimp each crimp connector.
A voltage tester won’t find this because it uses very low current. Poor corroded connections don’t show the drop unless pulling more amps. Think of it as a kinked hose - a trickle of water will come through and the kink doesn’t affect the flow, but open the faucet wide and the kink becomes a very noticeable limitation.

 

[HMT2]

I had this happen to me I checked all the wiring, rewired with larger wires. Still didn’t fix it. Finally, I took the brass buss bar off the negative side of the dc panel. There was no obvious “corrosion” but there was a patina where it connected to the panel. I took some 220 grit sandpaper to the whole buss bar, and made it look shiny and new, and Bob’s your uncle it was fixed. Has been for two years.

 

[Bill Roosa]

You have a high-resistance connection somewhere, likely on the negative side. Look for corrosion. Open EVERY connection and screw terminal, test the strength of every crimp connection. retighten. If you don’t find anything, re-crimp each crimp connector.
A voltage tester won’t find this because it uses very low current. Poor corroded connections don’t show the drop unless pulling more amps. Think of it as a kinked hose - a trickle of water will come through and the kink doesn’t affect the flow, but open the faucet wide and the kink becomes a very noticeable limitation.

A better diagnostic technique is to test the voltage drop across each connection. Just "cleaning everything up will not tell you anything if it does not fix th problem. to test you just set the multimeter to the lowest dc voltage setting and probe each side of the connection WHILE THE CURRENT IS FLOWING and with the boat set up just like it was when the problem occured. Just testing with the AP off WILL NOT WORK. Typical voltage drop is 0.1 or less volts at each connection. Voltage drop is additive so 10 connections with .3 volts drop will be a total of 3 volts drop at the (in this case) AP unit.

 

[danstanford]

There was a battery in the autopilot compass in my last boat. I had to open up the cover and there it was and the local electronics store had them on the shelf as they are used in other things.
Dan

 

[Kings Gambit]

I have a Hunter 36 with autopilot. While using it last week I suddenly got a low battery warning on the display and autopilot stopped working. I have checked my batteries and the voltage is good and stable. When I turn it off and back on, it works for about 15 secs and then displays low battery and stops again. Any ideas?

Ron

This happened to me some time ago, repeatedly as you describe. It never happens now after I upgraded my batteries to “true” deep cycle and take better care of them as MaineSail has described in here. Nothing else was changed. The easiest thing to do is recharge the batteries overnight shoreside (and check your water), so you know you have (or should have) a full charge, then go out and use it. I’m certainly not the expert on batteries as others in here are, so that might prove too simplistic of a suggestion compared to the others. But if your batteries are old, you might consider replacing and upgrading them.

Also, my understanding is that the autopilot will shut down to save batteries from becoming too depleted. How this is sensed and ”tripped” I don’t know, but I imagine the batteries would still have a working voltage, etc.

 

[Captain Larry-DH]

Also, my understanding is that the autopilot will shut down to save batteries from becoming too depleted. How this is sensed and ”tripped” I don’t know, but I imagine the batteries would still have a working voltage, etc.

Most devices that have a low-voltage shutoff have the threshold set too low to leave a "working voltage". For example, my refrigerator shuts off at 10.5 volts. That's dead flat (a battery damaging level). AP's tend to give low voltage alerts on the display.. IDK if they would shut down before killing the house bank, but it'd probably quit steering first (but with power remaining on).
I have a low-voltage-disconnect (LVD) output on my solar charge controller that lets me set the disconnect level and reconnect level for my fridge. (You can also buy stand-alone LVD devices for around $100 give or take.) My batteries are more expensive to replace than whatever food I might have left in the fridge. To preserve my batteries; I set the LVD level at 11.9 and the reconnect level at 12.1. This way it doesn't come back on until my batteries are being charged.

 

[sailme88]

I have a Hunter 36 with autopilot. While using it last week I suddenly got a low battery warning on the display and autopilot stopped working. I have checked my batteries and the voltage is good and stable. When I turn it off and back on, it works for about 15 secs and then displays low battery and stops again. Any ideas?

Ron

By any chance is the unit a Raymarine ST4000?

 

[Secret sail]

My wheel drive st4000 did the same thing... low battery... started zigzagging... I ordered a new one.
When I dismantled the old one I found the NMEA 183 and power connections corroded. I cleaned them all up and it worked fine! Sold it to somebody else and then fitted the new one which is far better

 

[Captain Larry-DH]

better diagnostic technique is to test the voltage drop across each connection.

It should be under load. If it’s not under load it might be too low a drop to measure.

 

[Captain Larry-DH]

My wheel drive st4000 did the same thing... low battery... started zigzagging... I ordered a new one.
When I dismantled the old one I found the NMEA 183 and power connections corroded. I cleaned them all up and it worked fine! Sold it to somebody else and then fitted the new one which is far better

I probably would have kept the old one as a spare.
(But when I die, my wife will need to call for a dumpster)

 

[Kings Gambit]

Most devices that have a low-voltage shutoff have the threshold set too low to leave a "working voltage". For example, my refrigerator shuts off at 10.5 volts. That's dead flat (a battery damaging level). AP's tend to give low voltage alerts on the display.. IDK if they would shut down before killing the house bank, but it'd probably quit steering first (but with power remaining on).
I have a low-voltage-disconnect (LVD) output on my solar charge controller that lets me set the disconnect level and reconnect level for my fridge. (You can also buy stand-alone LVD devices for around $100 give or take.) My batteries are more expensive to replace than whatever food I might have left in the fridge. To preserve my batteries; I set the LVD level at 11.9 and the reconnect level at 12.1. This way it doesn't come back on until my batteries are being charged.

Well, the OP did not say what the "good" voltage was that he saw after the autopilot stopped working.

 

[peterwynndavies]

Was it windy, was the engine running, was the fridge on? The wheel pilot has a tiny motor which gets overpowered too easily ...the strain gets too much and it shuts down.
Reef early, turn the fridge off, turn the radar off.

 

[HandsOnTech]

I don’t know that this solves the OP’s issue, but it seems like an appropriate place to document my autopilot troubleshooting exercise.

Symptoms:
The autopilot would run correctly for the first 5 to 10 minutes. Then the wheel would stop adjusting. If I nudged the wheel with my hand, it would start working again for a minute or two. This worked for two or three iterations and then quit working entirely.

Process:
I called Raymarine and was assured that the problem was that the power cables to the drive were of inadequate gauge. Wasted time and money replacing them. No change.

Called again, spoke to a different tech who assured me it was the drive transistors. Wasted time and money ($300) replacing the drive circuit board. No change.

Gave up. A year later I thought “This is silly, having an autopilot and not using it “. Called again and spoke to a third tech who immediately said the problem is worn brushes in the drive motor. Correct! A previous owner may have left the autopilot on for weeks or months at the dock, wearing down the brushes with constant minor adjustments.

 

[All U Get]

I probably would have kept the old one as a spare.
(But when I die, my wife will need to call for a dumpster)

Don’t you ever wonder if she has one for a spare, hopefully with a bigger, newer boat.

 

[Captain Larry-DH]

hopefully with a bigger, newer boat.

I told her to find someone else when I die. Maybe he’ll like boats