An interesting exchange with Kurt Dilworth on battery management and creating a DC Load Table  

From: Doug Lindal 
Sent: Tuesday, June 01, 2004 9:42 AM
To: Kurt Dilworth
Subject: Battery management 

Kurt: 

Just enjoyed a night on a state park buoy in South Puget Sound and have a couple of questions for you about battery management. 

We were on the hook for a total of 18 hours, from 2:00 PM to 8:00 AM the next morning. We watched our inverter usage and carefully monitored Amp Hour consumption. Most of the time we were drawing between 6 to 10 Amps according to the meters (the needle gauge on the 12 Volt panel and the Link 10). Only big consumption was for the microwave and a hair dryer for 5 minutes each. We ate dinner on another boat so no usage then. Watched a movie for 90 minutes using the TV and 12 volt DVD player, left the anchor light on for 8 hours and ran the Espar for an hour in the morning. Total Amp Hours consumed according to the Link 10 was 195 which is roughly what you get if you multiply 10 Amps usage times 18 hours.  

Big concern was that the Link 10 showed a red bar on top this morning as all the green bars were gone, indicating we needed to charge the batteries. This doesn't sound right, I thought, with our extra battery that we should be able to spend two, or even three days, on the hook without running the generator? How many Amp Hours can we safely consume without dropping below the 50% level?  Does our usage sound extreme or out of line, do we need to be more frugal?  Maybe it is as simple as the Link 10 green/red bar 'gas tank gauge' needing adjustment?  Anyway I thought I'd just report all this to you and get your opinion.

Many thanks! 

Doug Lindal

************* 

From: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it   
To: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Sent: Wednesday, June 02, 2004 8:49 AM
Subject: RE: Battery management 

Hi Doug, 

The total battery capacity with the inverter package is 600 amp hours.  You should be able to use 300 amp hours before recharging if you want to discharge your batteries to 50%.  The Link 10 meter has an adjustable warning system to tell you when it is time to recharge your batteries.  The factory default is set to 100% discharge which means that the meter would not show dead batts until 600ah were used (if the total capacity was set to 600 ah).   

To set up the Link 10 monitor: 
First set battery capacity to 600 ah. (page 21 of your Link 10 manual)
Second, set the discharge floor to 50% (page 32 “F09” function in Link 10 manual) 

This should get you going on the right track. 

The inverter panel has three switches.  The first just toggles between configure, off and display on.  The second switch toggles the inverter on or off and the third switch toggles the charger on or off.  The charger switch should be left in the on position at all times.  This is so when you plug the boat into shore power, the inverter automatically turns into a battery charger.  When you disconnect from shore power, the charger will automatically stop.    

Kurt

*************  

From: Doug Lindal
Sent: Sunday, June 06, 2004 5:58 PM
To: Kurt Dilworth
Subject: DC Load Table 

Kurt:

I am writing to follow-up on my e-mail and your response regarding ‘battery management’ while on the hook.  Using 300 Amp Hours as my limit I started building a table showing DC loads.  I have copied it below for your review.   

My problem is that despite studying the various owners manuals I couldn’t find all the wattage or amps for some of the electrical items and on others I was guessing as no manuals exist. Could you look this over and make comments and corrections please?  I think a cleaned up table would be very useful for other tug owners and is something you or Dave might want to share via at e-mail or at the rendezvous this fall. 

Doug

*************  

From: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
To: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Sent: Monday, June 14, 2004 2:04 PM
Subject: RE: DC Load Table 

Hi Doug, 

Here are some numbers we came up with on an inverter boat for a typical day. 

Kurt 

PS.  Remember that all devices that use an inverter to power them (television, outlets, microwave) will use a 10 to 1 ratio of dc to ac power.  For example, the television may only require 1A of AC power but it will take 10A of DC power to create that 1A of AC. You will see that the microwave and a hairdryer will consume lots of power.  The windlass is tapped off the start battery and not the house, therefore you can eliminate it from your list, but can add some numbers for the lights. 

DC Load Table for an 34’ American Tug