Sunday, March 20, 2011

Time for new batteries

Believe it or not, the batteries in the MV Independence have lasted for over eight (8) years.  The MV Independence uses three batteries - one 4D as a starting battery, and two 8D's as house batteries.  The batteries are all lead acid (flooded) batteries and not AGM or Gel batteries.  The MV Independence does have a permanent battery charger and while at anchor uses a small solar panel to help keep the batteries charged.

Using a hydrometer to see how "good"
your batteries are.
I am a "battery miser" and maybe that's why I was able to get over eight years out of these batteries.  However, as I tried to start the boat recently they're definitely dead.  I checked all the battery connections and they are all secure and good.  The battery voltage indicator at the helm showed that the batteries were good, that is over 13.5 volts.  But, as soon as you hit the starter button the sound was not of a healthy battery charge, rather that tell tale sound of a low or dead battery.  To confirm this I did a quick hydrometer check (specific gravity) and it showed that indeed all batteries are definitely low or dead.  A hydrometer is an essential tool that should be in every boater's tool kit.  It will definitely tell you what the status of your batteries are.  I knew last summer that my battery life was coming to an end - the windlass sounded slow, the starter was not crisp, and the voltmeter showed that it took a long time for my batteries to recover.

Eight years is a long time for the batteries to last.  How did I achieve this?  I've replaced almost all of my house lights with LED bulbs; I only run my refrigerator during daylight hours and then at a low setting (1-2); use a cooler for most items; carefully watch my battery voltage levels; use personal lighting devices versus using house lighting (lanterns, LED reading lights, etc.); and use an anchor light which runs from an independent battery.  Being a "battery miser" is not always fun.  The crew is always complaining about my concern on battery usage.  Maybe if I counted up the amount of money I've spent on ice I would be purchasing batteries every 4 or 5 years - I've never given it much thought.

Lately, I've been doing a lot of Internet research on what batteries to buy and where.  The cheapest option is to go to Sears and buy a "Die Hard."  This may not be the best option.  Instead, take an inventory of what your battery needs are and purchase an appropriate battery.  That is, identify the power requirements of your boat when it is at anchor, that is the refrigerator, lights, radio, and more and calculate the Amp Hours (Ah) required and compare that to the battery you are buying.  You never want to discharge a deep cycle battery more than 70% because it will never fully recover from this draining.  So, how does this all work?

Let's assume your Amp Hours (Ah) is 25 Ah counting all lights, refrigerator and more.  You might want to be a conservative "battery miser" like me and don't want to exceed 60% depth of discharge, giving you a 10% cushion.  Look at the chart and you'll see that 60% is about about 2 hours.  That will put you looking at purchasing a bit more expensive 200 Ah battery.  The cheaper battery might be only 125 Ah.  Multiply 200 Ah x 60% = 120 Ah (@ 2 hr. rate).  120 Ah / 2 hours = 60 Amps.  60Amps  / 25 Ah  = 2.4 hours.  So you're safe for another 36 minutes when your battery would be at 60% of depth of discharge capacity.  If you can lower your Ah you can run your batteries longer, for example  60 Amps / 20 Ah = 3 hours; or 60 Amps / 15 Ah = 4 hours!  You just need to decide how much power you want to use, or how much of a "battery miser" you want to be.  Conversely, if you chose the 125 Ah battery, you would only have 1.5 hours at 25 Ah!

What will take you the most time is inventorying your power consumption for a day at anchor.  I list each item (e.g., refrigerator, cabin lights, cell phone charger, radio, heater, etc.), the power draw in Amps for each, and an estimated time on or running for each, then multiply the time by the Amps to get Ah.  Some items may be only use mA or milliAmps which you have to divide by 1,000 to get the Amps. Add them all together to get your daily Ah needs. Don't forget to include your stereo which has a connection to the battery and uses power to display the clock!
Finally, rough estimates for a 4D flooded batteries deep cycle 200 Ah battery (lead acid vs. AGM or Gel) are about $170 versus over $400.  The $230 I would spend extra is not - in my opinion - worth it.  The argument of flooded versus other batteries could go on and on.  Yes, flooded batteries require more attentive maintenance - checking water levels, adding water, etc..  However, for me the flooded battery is my choice.  Flooded batteries have served the MV Independence for over 20 years. 

Stay tuned for an upcoming blog post on the project of removing and installing the new batteries.

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