Battery advice please

[andrewbartlett]

I am planning to use my Simrad TP10 Autopilot on my recently aquired small cruiser that has no electrics at present. I don't plan to have any other electrical devices . I have a suitable marine/leisure 12v. battery. My plan is to make a wooden box to take the battery ,wire the battery up to a female socket suited to the plug on the autopilot andaway I go under Autopilot!? To begin with recharge the battery at home from time to time and perhaps organise a solar charger panel if all goes well. Is this seemingly simple plan fundamentally floored in any way ? Do I need an earth in addition to the negative earth on the battery for example and perhaps an in line fuse?

 

[charles_reed]

I am planning to use my Simrad TP10 Autopilot on my recently aquired small cruiser that has no electrics at present. I don't plan to have any other electrical devices . I have a suitable marine/leisure 12v. battery. My plan is to make a wooden box to take the battery ,wire the battery up to a female socket suited to the plug on the autopilot andaway I go under Autopilot!? To begin with recharge the battery at home from time to time and perhaps organise a solar charger panel if all goes well. Is this seemingly simple plan fundamentally floored in any way ? Do I need an earth in addition to the negative earth on the battery for example and perhaps an in line fuse?

Did just that on my first boat in 1978 - the autopilot was the Autohelm Mk 2. The battery also provided power for the depth sounder and the Doppler log I fitted. I finally fixed up a rectifier on the Johnson outboard, to recharge the battery, though I'm not certain it had any significant effect.
Fused the feed for the autopilot but not the log or depth-sounder. Being DC you only need two wires +ve and -ve.

 

[andrewbartlett]

Thankyou Charles, very encouraging.

 

[VicS]

I have just about always had an autopilot ... one of the early analog MK1 Autohelm 1000 models ... still going strong.

I tried recharging the battery from the outboard .. at first a Volvo Penta with a bridge rectifier added to the AC lighting output and later with an Evinrude with built in charging coil and rectifier.

Unless motoring an awful lot the outboard does not produce enough power to keep the battery charged.

A small solar panel is the way forward. Since fitting one, and its only 5watts, I have not had to take the battery home for charging.

No you dont need an earth. Just positive and negative.

Use heavier wire than you expect to for the max current draw of the autopilot to avoid volts drop.

Fit a fuse as close as possible to the connection to the battery positive. Rated little larger than the current requirement of the autopilot but less than the max safe working current of the wiring.

Be warned though that electrical systems on small boats tend to grow: Autopilot, navigation lights, cabin lights, echosounder, log, VHF, GPS or plotter


.

 

[JumbleDuck]

I survived 20+ years with a 21' boat with electrics but no on-board charging at all. I didn't have an autopilot, but I did have tricolour, VHF radio, echo sounder and cabin lights. I could easily get a week (including a couple of overnights) out of a charge, and I carried a battery charger and a winning expression. I never had any difficulty in find somewhere to let me charge the battery when I needed to. So yes, I think your plan is perfectly practical.