Add a second battery

[NorCal Gordo]

My 2720 has only one battery. Any downside or cautions to adding a second in parallel? Thanks!

[rickst29]

No cautions or warnings, except to be sure that they are the same type (e.g., both flooded-lead-acid, both AGM, or both Lithium).

You can't mix AGM and Flooded cell together with good results, because "flooded cell" lead-acid NEEDS occasional equalization, whereas AGM will be WRECKED by that process. Lithium and Lead acid also don't mix well, because they work at different voltages.

[ShrimpBurrito]

You can also do two 6-volt batteries in series, which will allow you to use true deep cycle batteries (with thicker plates, as opposed to "marine/RV deep cycle batteries"). They are often used in settings like golf carts, among others, which don't require any cranking amps. That allows for a deeper discharge without damaging the battery.

Dave

[MrGallegos]

How often should flooded-cell battery water levels should be checked?

[Bill]

How often do you check the battery in your car? If you are like a lot of us, not very often. There isn't really any kind of fixed interval because it depends on several factors such as temperature (a bit more often in hot weather), battery age (more often as the battery gets older), and charging conditions (never leave a battery on a garage-style charger for more than an hour or so). A battery also has a substantial cushion between "Full" and "Needs water now".

For normal usage, I'd suggest you start by checking it once every couple months. You will probably find that this is more often than needed, and you can back off a bit. If it needs water more often than this, something is wrong. Most likely it is being overcharged.

The most important thing is that when your battery needs water, use only distilled water (buy a gallon in your supermarket - it's cheap), never tap water. I found this out the hard way, many years ago. It really does make a difference.

Bill

[rickst29]

Originally Posted by MrGallegos

How often should flooded-cell battery water levels should be checked?

It also depends on the "Power Converter" within your particular TM. The original "Parallax" Power Converter in older model years (such as yours), are notorious for overcharging batteries and causing water levels to drop. The newer "WFCO" models, from years after 2006, are notorious for leaving batteries under-charged, and will almost never need added water. They instead cause earlier damage to lead plates, when "phantom loads" (such as the gas detector and radio) consume all of the "float mode" power which the Converter is willing to put out.

If you were to leave a Parallax-based TM plugged in all winter long, I would expect to find the batteries in need of more water every 3 weeks or so. (So I would not do that - I would instead plug in the TM for only a few days, and then pull the plug and let the batteries "rest" and slowly decline for 2-3 weeks before plugging the TM again. The maximum length of time between plugins varies according the total size of your batteries - a "big" set of batteries will last much longer much than a single small one. (Because the "phantom loads" are a constant draw, and run down a single small battery much faster).
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In both cases, a quality "battery tender" unit would be better for the batteries than the internal "power converter", and probably avoid any need to add water during the winter.
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The Parallax alone is especially dangerous (if left plugged in all winter, without adding water). If left that way, the batteries would almost certainly be ruined by springtime due to low water levels.

[wrenchami]

Back to the original question, Not only should batteries connected in parallel be the same make, model and capacity, but also of the same age. Adding a new battery in parallel with an identical but older battery won't work well. The age difference will cause an imbalance between the two resulting in one battery being overcharged and the other undercharged, contributing to their early demise.

That said, I converted to two 6 volt batteries in series on the front frame for the reasons stated earlier in this thread. I included a disconnect breaker on the positive lead feeding the trailer to separate the battery bank from the WFCO unit and added a quick disconnect connector on the batteries for an external 3 stage charger. When in storage, I open the breaker and keep the batteries charged with the external charger. When getting ready for travel, I disconnect the external charger, switch over to the WFCO and fire up the fridge, etc. a few days in advance and leave with a known full charge on the batteries. Just my best practice.