How to Maintain Deep Cycle Batteries

The Battery Genius knows a thing or two about maintaining your deep cycle batteries.  I'm going to teach you now, but before I do, I want you to realise the importance of doing ALL of these things in order to make your batteries last their longest.  Don't be that guy in Duluth or Cleveland that does ONE or TWO of these things and then whines because his batteries don't last. Flooded Deep Cycle Batteries require love.  So I will tell you how to love your batteries well and How to Maintain Your Deep Cycle Batteries.

First, I want all of you to raise your right hand and repeat after me:

"I, (state your name), solemnly swear to trust The Battery Genius do what he says so that my batteries will last a really long time. I will not flake and only do a couple of these things, only to regret it later."

First things first; New batteries should be given a full charge before use. Yeah, yeah, I know --  your new batteries come from the manufacturer ready to rock-n-roll, but ALWAYS charge your batteries fully before use, please.

New batteries need to be cycled several times (AND NO GREATER THAN 50% Depth of Discharge) before reaching full capacity and hitting their sweet spot -- Usually about 20-50 cycles should do it.  Most importantly, be sure to limit how deep you discharge these babies when you first start using them. That's right.  I said Babies.  Treat them like babies. You have to nurture and work them into the rhythm of how you will use them before you can really start working them.

Batteries should be watered AFTER charging UNLESS plates are exposed before charging.  If exposed, plates should be covered by approximately 1/8" of water.  Check water level after charging.  The water level should be kept 1/4" below the bottom of the fill tube in the cell cover.  A Pro-Fill watering system can eliminate the guesswork of proper fill levels and really help with maintaining  your batteries.

Water used to replenish batteries should be distilled or treated to not exceed 200TDS (Total Dissolved Solids...Parts Per Million).  Particular care should be taken to avoid metallic solids like iron.  You'll hear a lot of old salty battery dudes sitting around your local garage or battery shop sayin', "If it's clean enough to drink, you can put it in yer battery."  Don't listen to him.  Even if he makes fun of you for driving a mini-van and knowing nothing about batteries, DON'T put tap water or spring water in your battery.  Use distilled water.  You'll thank me.

Batteries should NEVER be discharged below 80% of capacity (approximately 1.8 volts per cell under normal load;  1.98 volts open circuit; 1.145 specific gravity).  "But, Battery Genius, aren't Deep Cycle Batteries designed to be discharged and recharged over and over,"  You ask?  Short answer, Yes.  However, anything past 80% DOD is only working them harder than they were designed and you risk speeding up sulfation of the battery plates. Knowing and using the proper battery for the job will help avoid excessive discharge.

Here's a hint on how to know whether or not you have the right battery bank for the job -- If your batteries won't completely charge in 8 hours, you're not using enough battery.

In situations where multiple batteries are connected in series, parallel or series/parallel, a replacement battery(s) should be of the same size, age, and usage level as the companion batteries.  DO NOT REPLACE JUST ONE BAD BATTERY!  Never put a new battery in service with a pack which has 50 or more cycles.  Either replace will all new batteries, or use a good used battery(s) with same cycle use.  If you use an older battery with the new, the older battery won't be able to keep up and will ultimately die or bring the new batteries down to its level, shortening their life.

Please, please, please, test your batteries every now and then (Four times a year).  Periodic battery testing is an important preventative maintenance procedure.  Hydrometer readings of each cell (fully charged) gives an indication of balance and true charge level.  Imbalance could mean that need for equalizing and is often a sign of improper charging or a bad cell.

Voltage checks (open circuit, charged and discharged) can locate a bad or weak battery.  When checking specific gravity, it is possible to convert the reading to what the open circuit voltage should be.  The formulas is to add .84 to the hydrometer reading and multiply by the number of cells.  Thus, a fully charged battery with a reading of 1.265 SpGr will have an open circuit reading of 12.63 volts.

Load testing will pick out a weak or bad cell when other test methods fail.  The point is to look the abnormal.  A weak cell or battery will cause premature failure or erratic function of companion elements such as batteries, navigation systems and other electronics.

DO NOT use a mismatched charging source of any type.  An undersized charger will never get the job done, no matter how long it tries.  An over-sized charger may cause excess gassing and heat that could possibly result in thermal runaway, and explosion! Explosions are bad.

Batteries are like muscles, Inactivity can be harmful to Deep Cycle Batteries.  If they sit for several months, a "boost" charge should be given; more frequently in warm climate (about once a month) than in cold climates (every 2-3 months).

Lastly, just like people, as batteries age their maintenancerequirements change.  Generally, their specific gravity is higher.  Gassing voltage goes up.  This means longer charging times and/or higher finish rates (higher amperage at the end of charge).  Usually, older batteries need to be watered more often or their capacity may decrease.

Hopefully, you're a little wiser today about your Deep Cycle Batteries than you were before you found The Battery Genius. To BUY Deep Cycle Batteries or any of the maintenance items mentioned here, visit Powerstride Battery for all of your battery and battery related accessories.

Mar 25th 2010 The Battery Genius

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