I sail a Cal 21. I' installing an autohelm 1000 I bought used. I wonder what battery I need to run just the autohelm. I'll only be using it intermittenly for short periods. Can anyone help?
battery size for autohelm 1000
- Thread starter steve fd
- Start date
This is one of those 'how big a bucket' do I need questions.
Check the current draw of the autopilot, multiply by how many hours you might use it between recharges, double that number to ensure you dont draw the battery below 50% of its rated output and you have your answer.
Check the current draw of the autopilot, multiply by how many hours you might use it between recharges, double that number to ensure you dont draw the battery below 50% of its rated output and you have your answer.
I have an ST 1000. I also got mine used on eBay.
I have two deep cycle batteries wired in parallel and I have never even seen the voltage drop on the meter after a day of sailing. I don't think it really uses that much juice. My guess is that the only time it is using any appreciable current is when it is actually adjusting the helm. And those occur in short bursts so .... not much juice over time. The amp calculation that @Don S/V ILLusion suggested is typically how you do these sort of analyses. But I suspect the amp draw listed on the ST 1000 specs is peak amperage and that only applies while it is adjusting the helm and not expected draw just from being turned on.
I have two deep cycle batteries wired in parallel and I have never even seen the voltage drop on the meter after a day of sailing. I don't think it really uses that much juice. My guess is that the only time it is using any appreciable current is when it is actually adjusting the helm. And those occur in short bursts so .... not much juice over time. The amp calculation that @Don S/V ILLusion suggested is typically how you do these sort of analyses. But I suspect the amp draw listed on the ST 1000 specs is peak amperage and that only applies while it is adjusting the helm and not expected draw just from being turned on.
So that means it's drawing about 1A when it's steering. Assuming it's steering 1/4 of the time, i.e., 25% duty cycle, that's only 1/4 of an Ah per hour. Sound right?
If that's so, I might hot-wire a Li-Ion car jump starter that I could almost put in my pocket, and recharge it from my car cigarette lighter on the way to/from the boat. There's one on Amazon that's 1.8Ah and has a a 12V 10A jack on it.
If that's so, I might hot-wire a Li-Ion car jump starter that I could almost put in my pocket, and recharge it from my car cigarette lighter on the way to/from the boat. There's one on Amazon that's 1.8Ah and has a a 12V 10A jack on it.
I get confused sometimes with these calculations. The specs in RitSim's post show "10W at 25% duty cycle". so wouldn't that already assume active steering 1/4 of the time? So if it was in use (not in standby mode) it would draw 10 Watts (at 25% duty cycle) which over an hour would be about .75 Amps so the 1.8 AH battery pack would last just a little over 2 hours (at 25% duty cycle). Is that right?
Not a lot of heavy lifting herein for you to verify yourself. It's always best to do your own due diligence
Oh, 18 is a lot more than 1.8.
But help me out. Isn't the 10W already at 25% duty cycle as it says in the spec? So I would assume it really draws 40W and then at 25% duty cycle as it shows in the spec that would be 10W so it would seem it actually consumes .8 amps per hour already assuming a 25% duty cycle. So I don't think you can multiply your 22 hours by 4. Not trying to be nit picky, I just want to know how to interpret the spec showing "10W at 25% duty cycle".
Thanks
Yup.. that kind of a spec means an average draw of 10 watts IF the pilot is working at 25% duty cycle.. Bad sail trim or rough conditions would mean a bigger duty cycle and more power draw.. so 10 watts is pulling an average 10/12 = 0.83 amperes.. so it'd be pulling 1 amp hour every 1 hour and 12 minutes.. or close to that depending on Mr. Peukert..
I don't think so. Could be an ambiguity in the spec., but please note that Watts is an instantaneous measure of power, in this case Volts times Amps, not a measure of power over time. Power over time can be expressed in Watt-hours. One Watt hour is equal to one Watt of average power flow over an hour. So, @kloudie1 is incorrect in stating "10 watts is pulling an average 10/12 = 0.83 amperes." At least I think that's what he's saying. I interpret that spec that it draws 10W at a 25 % duty cycle as meaning they assume a duty cycle of 25 %, so it would consume 10W-h/4 in a one hour period, or 2.5W-h per hour.
40 mA in standby.
In use the 1000/2000 manual says:
"Auto: 0.5 A to 1.5 A depending on boat trim, helm load and sailing conditions"
Doesn't mention duty cycle.
Yep, except never count on more than 50% of the battery capacity. Running a battery lower shortens its life.
Ken
for lead-acid, yes, not for litium-ion. Depends on the chemistry.