Category Archives: batteries

Cold Weather Care and Feeding of Batteries

A recent discussion and some questions on the subject of batteries gave me the idea to sum up what I have on the subject in hopes that it will help other folks’ batteries to last longer.  For the RVer who wants to stay quiet, a good, reliable battery bank is the way to keep so many of those systems that make camping life so comfortable going, and most of us can’t afford and don’t want to buy those expensive new batteries often.

There are a number of strategies when choosing batteries for your RV/Camper.  Some people choose one single large battery, like this ‘universal replacement’: 

12v 200ah Solar Power Battery – Deep Cycle (Electronics)

List Price: $359.99 USD
New From: $374.50 USD In Stock
Used from: Out of Stock

This one has a rating of 200 Amp-hours (It would last for 200 hours under a constant 1 amp draw, or 1 hour at a 200 amp draw) at 12 volts DC, which is the usual power system for your regular vehicle and most RVs.

Some folks like to use golf cart batteries, as they can be obtained used, and even as 6 volt batteries, can be hooked up in series to make a 12 volt output and are often fairly cheap, like these (new):

Sealed AGM Gel Golf Cart Battery 12 Volt 35 Amp Hour – 4 Pack (Misc.)

List Price: Price Not Listed
New From: 0 Out of Stock
Used from: Out of Stock

These, hooked up as two sets of series connections by a parallel connection would yield 140 Amp-hours at 12 Volts DC.

Now, the ones above are AGM (Absorbant Glass Mat) batteries. This technology became popular in the early 1980s as a sealed lead acid battery where the acid is absorbed by a very fine fiberglass mat, making the battery spill-proof, and means that it can be mounted in any direction. These batteries have very low internal resistance, are capable of delivering high currents on demand and offer a relatively long service life, even when deep-cycled.

AGM batteries are maintenance free, provide good electrical reliability, and are lighter than the flooded lead acid type (which I’ll mention in a moment). They stand up well to low temperatures and have a low self-discharge, but the major advantages are a charge that is up to five times faster than the flooded version, and the ability to deep cycle without ruining the battery. AGM batteries offers a depth-of-discharge (DoD) of 80 percent, while flooded batteries are specified at 50 percent DoD to attain the same cycle life.  The downsides are that they tend to be heavier/bigger per Amp-hour and higher costs than flooded batteries.

A flooded battery might be a cost- and weight-effective choice, looking something like this one: 

Trojan T-1275 12V 150Ah Flooded Lead Acid Golf Cart Battery FAST USA SHIP

New From: $279.00 USD In Stock
Used from: Out of Stock

This battery would give 150 Amp-hours at 12 Volts DC, but with a smaller, lighter battery.  The downside of this battery is that you have to make sure the battery is topped up with distilled water, as it will off-gas explosive hydrogen gas and other corrosive gases (so it has to be placed in a vented compartment). You can get around some of the work of topping your battery(ies) up with an automatic system like this one

RV Trailer Camper Electrical Battery Watering System Single MP-2010

List Price: $43.69 USD
New From: $43.69 USD In Stock
Used from: Out of Stock

which makes it a simple job with a a hand pump to fill once you install the hose to each of the cells of the battery(ies).

Another problem with flooded batteries is that a full discharge (50%) causes strain on the battery, and each discharge/charge cycle permanently robs the battery of a small amount of capacity (Unnoticable at first, but each subsequent discharge takes more capacity from the battery). Most of the flooded types will have a life of about 200-300 cycles, while the Lifeline batteries that we got are rated for 1000 cycles.

When it comes to cold weather, AGM batteries have another couple of advantages over flooded batteries in that they are much more likely to survive a freeze intact, and loose less of their charge over the same length of time.  This last is probably the most important of the two, as the trick to keeping a battery healthy over cold weather is keeping it charged.

As the weather gets colder, the effective Amp-hours in a battery drops, while at the same time, its voltage capacity rises.  This means that your charger has to be able to cope with this.  There are a number of ‘Smart Chargers’ out there, like these: 

NOCO Genius G3500 6V/12V 3.5A UltraSafe Smart Battery Charger (Automotive)

List Price: $59.95 USD
New From: $59.95 USD In Stock
Used from: Out of Stock

BLACK+DECKER BM3B 6V and 12V Automatic Battery Charger / Maintainer (Automotive)

List Price: $16.79 USD
New From: $16.78 USD In Stock
Used from: Out of Stock

NOCO Genius GENM2 8 Amp 2-Bank Waterproof Smart On-Board Battery Charger (Automotive)

List Price: $99.95 USD
New From: $99.95 USD In Stock
Used from: Out of Stock

or as units built into converters like this

PowerMax PM3-55 110 V to 12 V DC Power Supply Converter Charger for Rv Pm3-55, 55Amp (Wireless Phone Accessory)

List Price: $116.93 USD
New From: $104.34 USD In Stock
Used from: Out of Stock

The thing about these ‘smart’ chargers is that they will automatically detect the charge that your battery has and adjust their output to give your battery what it needs, from ‘bulk charging’ (up to almost 90% charge) through the ‘absorption charge’ (to charge the last 10-15% of the battery) to ‘float charging’ (which keeps the battery full at a constant lower voltage) and even the maintenance cycle of ‘equalizing’ charging (which highly charges the battery to prolong the battery life by removing sulfur from the plates).  A regular charger like you might have in the garage for your  car generally has settings for either a ‘starting charge’ (lots of amps you use to try and get the car started with a dead battery), a ‘bulk charge’ (To bring the battery to a full or near full charge), and a ‘float charge’ (to keep the battery full), though it doesn’t pay any attention to the battery that it’s connected to and continues to do what the switch is selected to, which can easily over-charge a battery and leave you with sulfur corroded plates.

Some people winterize their system by removing the batteries from their RV/campers, and keeping them warm. This is a perfectly acceptable way to winterize, but for batteries with larger Amp-hour capacities (and especially those that are heavier AGM batteries or built into specialized compartments) this can be a lot of work. You still have to remember to keep the batteries charged, or you might lose a cycle of life through discharge as they sit.  Also, if you have the flooded batteries, taking them out is a great time to top them up, and pay more attention to keeping them charged, as they’ll discharge faster than the AGMs.

Also, if you’ve heard that you can’t store your batteries on concrete over winter, as long as your batteries are in a plastic case, you can disregard it.  This adage comes from the time when batteries were produced in wooden cases, and the wet wood sitting on the porous concrete meant that the concrete would slowly leach away the water from your battery.  The only concern with modern batteries is if you can get your fingers underneath to lift them back into their places so you can get going again in the warmer times of the year.