The HOUSE batteries to be clear. The chassis or engine batteries are separate and require little, or in my case, no maintenance as they are sealed. Check yours.

When the time comes I will discuss the replacement of the batteries here. For now, it’s just a matter of keeping them corrosion free and watered, and occasionally equalized. (See next section)

There has been a surprising tendency for corrosion to start, especially on the hasp on the strap that secures the house batteries. (The chassis batteries are pretty well behaved in all aspects). Obviously there is some galvanic action and I am in the process of thinking about making that all a little better. Putting a sacrificial anode somewhere, like on a boat, comes to mind. Stay tuned. For now I occasionally clean with water with a little baking soda in there to neutralize any acid and I rinse liberally with a garden hose. Any sign of “cauliflower” is immediately addressed.

On edit: I have removed the straps. Problem solved. 20,000 miles later I have had little or no corrosion anywhere and the batteries haven’t moved at all. If the bus ends up in a position where the batteries come out I have MUCH bigger problems.

As far as watering…… I have never seen batteries use water like the house batteries, as in 4+ gallons a year. After reading around a bit this appears normal. So, water we do, about once every two weeks to once a month depending on use. There are automatic watering systems that people put in. I don’t see the need to spend the money and clutter the compartment up with hoses. NAPA sells a nice watering can which automatically shuts off when the level is correct. Put the spout in the hole, press down and release when it stops bubbling. Fast, easy and no mess. I think I paid $11 for the thing. Oh yeah, use distilled water. If you’re ever on a trip away from a CVS or similar (there’s a few places left that fit this bill) and discover you forgot to fill them you can run water through a coffee maker, which technically makes it distilled. Run a batch to clean it first and discard. Also, unless you are boon docking and run the generator once or twice a day to charge the batteries you can turn down the max amps the Magnum will pump in. (See the Magnum manual.) I dialed it down to 45A and have found that this reduces the water loss somewhat……

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(CAUTION: Battery acid is nasty stuff. Wear eye protection and rubber/latex gloves. Have water and baking soda on hand for cleanup.)


Stationary batteries are almost exclusively lead acid and some maintenance is required, one of which is equalizing charge. Applying a periodic equalizing charge brings all cells to similar levels by increasing the voltage to 2.50V/cell, or 10 percent higher than the recommended charge voltage.

An equalizing charge is nothing more than a deliberate overcharge to remove sulfate crystals that build up on the plates over time. Left unchecked, sulfation can reduce the overall capacity of the battery and render the battery unserviceable in extreme cases. An equalizing charge also reverses acid stratification, a condition where acid concentration is greater at the bottom of the battery than at the top.

Experts recommend equalizing services once a month to once or twice a year. A better method is to apply a fully saturated charge and then compare the specific gravity readings (SG) on the individual cells of a flooded lead acid battery with a hydrometer. Only apply equalization if the SG difference between the cells is 0.030.

During equalizing charge, check the changes in the SG reading every hour and disconnect the charge when the gravity no longer rises. This is the time when no further improvement is possible and a continued charge would have a negative effect on the battery.

The battery must be kept cool and under close observation for unusual heat rise and excessive venting. Some venting is normal and the hydrogen emitted is highly flammable. The battery room must have good ventilation as the hydrogen gas becomes explosive at a concentration of 4 percent.

So, in laymans terms, you “cook” them once in a while to keep them from falling asleep.  Now, mine have not been equalized since I’ve had the coach. The coach was built during 2016, who knows when the batteries were made…. so potentially they are 3 to 3-1/2 years old. It’s early 2020 as I write this. The dates were not punched out as a retailer would do when you buy it. Other owners on social media with coaches as young as 2016 (so a little older than mine, but not much) are reporting that their batteries are losing effectiveness and they are replacing them. Don’t know how they used and maintained them, mine have been used but not abused, and watered on time, fully charged with the proper profile, and never discharged more than 50%. (This is one reason why I installed the Battery Monitoring Kit) They are still performing quite well.

But the article states: First you should measure if they need it. Enter the hydrometer. A very high tech piece of equipment…..

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So measure we do. The batteries installed are World Wide batteries. This appears be a re-label of known brands, except we don’t know for sure which one here.  The World Wide web site speaks highly of their product but give zero data or models. Not sure what the game there is. A search of the model T105-OE leads to the Trojan website. The specs jive, the color is wrong. The pictures are inconclusive. But that’s a decent brand. Let’s hope they built it and World Wide labeled it.IMG_3790.jpg

Anywho, according to the article I should only equalize if there is a difference between cells of .030 or higher…. (Not the same as .03  If you’re nerdy enough Google “significant digit” lol.) So lets take a close look at the instrument:

There’s a specific gravity scale from 1.000 to 1.300 Then there’s a little thermometer to give us temperature correction. Good news, 80ºF is zero correction and that happens to be the temperature today. So, I’ve topped off water, fully charged them,  we’ve disconnected it for about an hour to let it rest and we’re looking for the specific gravity in each cell, as well as any differences between cells. At 75ºF a fully charged cell should  be 1.255 to 1.275 The difference between cells should not be more than .030

(As an interesting aside…. I always thought the thermostat got it’s low voltage from the AC unit. Nope….. dark. No AC for an hour….. hmmm…..that wasn’t in the plan….)

So… what batteries do we have here? 4x6V DC…… Lets number them 1-4, and cells 1-3 for each battery. Which one is which matters not, but for future reference I did this:

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  • 1-1 = 1.200
  • 1-2 = 1.250
  • 1-3 = 1.200
  • 2-1 = 1.225
  • 2-2 = 1.250
  • 2-3 = 1.225
  • 3-1 = 1.250
  • 3-2 = 1.275
  • 3-3 = 1.280
  • 4-1 = 1.260
  • 4-2 = 1.250
  • 4-3 = 1.270

So here we see that #1 and #2 are a little tired,

NOTE: I’ve been told if you have the old style remote with just the 6 lights you cannot use it to equalize. You could use a battery charger with that functionality built in. The newer programmable remotes have this capability. I do believe there’s been folks that upgraded their remote to the programmable model, plug and play.

Use your book. If you don’t have one, download it from Magnum. First, determine which revision remote you have. (Page 16 in the book) I have 2.8, the book applies. Then we go to page 26. This tells us that we need to be charged, ie in float mode. That being the case push and hold the ON/OFF/CHARGER button until the message EQUALIZING appears.

Interestingly the MAGNUM book also addresses the question “How often?” and has the same answer “Once a month to twice a year depending on use” AND they say to measure SG and equalize if over 0.015, which is only HALF of what Battery University recommends.

So, now we’re equalizing. Yup… we are cooking them….. on purpose. (BTW those amps fairly quickly dropped into the 30’s and 40’s) And she’s bubbling…. you can hear it.

It’s off gassing Hydrogen which is explosive. Compartment door open, no smoking or open flames. And, the book says measure SG. When it no longer increases you’re done. Well…. let’s see how far we get. After one hour, turned off the equalization and topped off the water. Let it sit for 2 hours on a less than 1A float charge. Then took readings, which were slight improvements but #1 and #2 still not where they should be. Gave it another hour, although when improvement stops you’re done. So here’s where I was at after the second hour:

  • 1-1 = 1.270
  • 1-2 = 1.260
  • 1-3 = 1.260
  • 2-1 = 1.285
  • 2-2 = 1.285
  • 2-3 = 1.285
  • 3-1 = 1.260
  • 3-2 = 1.270
  • 3-3 = 1.260
  • 4-1 = 1.285
  • 4-2 = 1.285
  • 4-3 = 1.270

So….. what do we have here. First off, the reading across the three cells of each individual battery are more even.  Secondly they are on average 4-5% higher, and #1 and #2 even more improved than that. They are now all well within the range of a fully charged lead acid cell, in other words pretty healthy.

So, a little emery cloth on the battery cables, a nice rinse and a squirt of corrosion protection on the terminals and we’re good to go. Stretching the life of your batteries through proper maintenance saves MONEY!


We’ll revisit this on a regular basis.

Update: March 2021 and at almost 5 years old the bank is holding up OK. Hygrometer slightly “out of the green into the white” (although the sun was on the compartment so I got to add a few points according to the scale) so another equalization. About two hours worth and that’s all she took. Back into the green. All cells look the same. Good to go!