Friday, June 23, 2017

Once Again I Pick the Dinosaur of Batteries

During my recent post on replacing the Tripp-Lite inverter/charger with an IOTA charger I mentioned that I was also replacing the batteries. Actually the battery replacement is what triggered the charger replacement. After all, despite its failed inverter the Tripp-Lite was still serviceable as a charger, but as long as I was going to be messing around in the electrical compartment anyway . . .

The death of, and need to replace my 200 amp-hours of battery is what prompted the replacement of the Tripp-Lite with the IOTA

It all started because the summers in Central Texas are a tad warm, with daily highs running from the low 90’s to the low 100’s for a good solid three months. During those three months the humidity runs in the 90’s as well, and with all that water in the air hanging on to the heat it means that nighttime temps only dip by 10 to 15 degrees.

Me, I’m pretty stubborn (or stupid depending on who you talk to) and continue to spend the majority of my day either outside or in the barn which is not air-conditioned, but the supplies in The Van that wouldn’t fare as well as I do under those conditions get stuffed into her fridge for the duration. Beans, rice, sugar, dried foods, toothpaste, deodorant, lip balm, and anything else that could be affected by prolonged heat, all goes into the fridge which is turned on to its warmest setting, in my case that’s 50 degrees in the fridge section and 42 in the freezer section.

So with new batteries in hand I gathered a few simple tools and supplies to drop them into place.

Which is why, even though I don’t do much camping during the summer, the 12V system still gets a decent workout.

Even parked in the partial shade of an oak tree and accounting for some cloudy days, the solar panel/battery combination has proven up to the task of keeping the fridge running all summer, but that doesn’t mean I skip keeping an eye on things. Every morning I stick my head inside The Van and check the fridge thermometer and the 12V system monitor panel.

Good thing too because one morning, pretty much without warning, the battery voltage had dropped to below 12 volts overnight despite less than a 20% discharge. (Yes, I knew the batteries were showing signs of aging but to go from low-normal to essentially dead that quickly was unexpected.)

After horsing the new batteries into the boxes the next step was to use a wire brush to clean up the eyelets on the ends of the cables

According to my records the current batteries have been in use for just shy of three years. Even accounting for the fact that they are lowly wet-cells that’s just barely long enough to be reasonable and – well – turns out that’s on me this time. My excuse? The time honored but true none-the-less; "I forgot"

Then to ensure a good solid connection that will conduct well and won’t corrode over time I smeared each eyelet with GB Ox-Gard (This stuff is conductive so watch where you smear it!)

After three frustrating rounds of maintenance-free AGM's, when I switched back to wet-cell because the performanceof the AGM’s was not justifying their expense I apparently didn’t pick up all my marbles and completely twigged out on topping up the water.  Yeah, that's right, I forgot. . . And when I did finally pull the caps there was no water to be seen!

I tried topping up the cells, which took about a half-gallon of distilled water between the two batteries, and then hitting them with an equalize charge, but over the next couple days I did some draw-down testing which only confirmed that I had killed them both.

Before connecting the batteries back into the system.

Oh don't get me wrong, adding water and equalizing helped and the batteries were still serviceable at a reduced capacity, but for how long? Based on my experience with those tiny but expensive motorcycle batteries, not very! (I have now converted all my small engines over to Walmart's $20 U1's. This usually means relocating the battery and building a new carrier but it beats the hell out of buying tiny little, and decidedly delicate, original replacements at $70 or more a shot!) I rely heavily on The Van's house batteries so would rather call them dead now than get caught short somewhere and have to deal with them on the road.

I'm pretty sure some of you started shaking you heads at my regressive choice of battery back there at the first photo, after all, that's the equivalent of choosing to drive a truck with manual transmission and crank-down windows and who in their right mind would do that in this day and age, right?!

Well read on!

Despite AGM’s looking better on paper (Granted, mostly marketing paper but paper none-the-less.) after carefully analyzing the actual costs of the three sets of AGM’s I had used up in a little more than ten years of real-life usage, I switched back to wet-cell three years ago because I could not justify the nearly 200% cost premium of the AGM’s anymore.

Now in the past three years there have been some amazing strides in battery technology and right now Lithium Ion are all the rage. Ohh goody!!  New toys!  

Except Li-ion’s are pricey things with a capital P! so are even more worthy of a careful cost analysis.
and here’s what happened when I ran the numbers:

Then finally putting the tops back on the battery boxes and sealing them up. Very important with wet-cells since they out-gas as a normal part of the charge cycle and I definitely don’t want explosive hydrogen floating around inside The Van!!

* Li-ion batteries can be discharged to 80% as compared to wet-cell’s (AGM and gell too) 50%. With my 200 Ah setup that means that instead of 100 Ah of usable power I could get 160 Ah. I’ve been getting along fine with my 100 Ah but more is better, right? So add this to the nice-to-have column.

* Unlike wet-cell, Li-ion batteries can deliver their power at an incredible rate without damaging themselves, and can also be recharged at equally unbelievable rates if you have the equipment to do so. This is great for electric vehicles, golf-carts and mobile devices, but not so much for RV’s. With the limited capacity found in most RV’s because of space and funds, taking advantage of the Li-ion fantastic discharge rate would be a lot like the M16 I carried back in the dark-ages when I was in uniform. At 600 rounds per minute that sucker could empty a 30-round banana clip in seconds, but then what? “Ummm, time-out guys. I need to reload. . .”  So put this one in the ‘ehh, so what’ column.

* Even with the on-board smart-charge electronics necessary for the common man to keep Li-ion’s healthy over the long term, 200 amp-hours of Li-ion weighs in at more than 40 pounds less than the same capacity of wet-cell. And this only gets better if you figure it based on usable amp-hours. Great! Add this to the plus column.

* With the proper onboard smart-charge electronics, I can use my existing charge controllers, solar and shore-power, to keep the Li-ion’s topped up. Another one to add to the plus column.

* Li-ion’s are supposed to have a 2000 to 5000 cycle life-span compared to the wet-cell’s 500 to 1000. To be fair here let’s take the low end of both, which means I will have to replace the wet-cells 4 times for every one time for Li-ion, and if the life-cycle of the Li-ion’s trend towards the higher end it only gets better. Sounds like another one for the plus column, but for now let’s just hold onto that one.

So right now I have one in the nice-to-have, one in the ‘ehh, so what’ , and two in the plus column with a potential third to follow, Based on that the Li-ion’s are looking like a winner – but - 
When I said earlier that Li-ion’s are pricey, that might be an understatement! To purchase a fully tricked out pair of group-27 100 amp-hour Li-ion’s costs $2600, to replace my pair of lowly NAPA 8301’s cost $270. Broken down by usable amp-hours over expected life of the battery the numbers come out like this

Usable Ah per cycle
Expected Cycles
Usable lifetime Ah’s
Cost per usable lifetime Ah

This is rather simplistic, but even though the Li-ion’s are getting there in terms of cost effectiveness, they still cost a premium over the wet-cells; so lowly wet-cells it is.

Who knows, in 3 or 4 years when I’m in the market for new batteries again maybe the numbers will come up differently, but for now I’m sticking to the wet-cells.

Of course next time around I’m going to have to add in an estimated expiration date on both The Van and my ability to use it. If the longevity claims of the Li-ion’s hold up over time in actual RV-type usage, as opposed to electric car usage which is entirely different, extrapolating based on my experience with the wet-cells, one set of Li-ion’s could last 20 years and I’m not sure I see much sense in paying money to buy something for the next guy to use.

 In the mean time I’ve already added checking the water levels to my quarterly maintenance schedule.


  1. My AGM batts made about 4 years. My biggest plus is having them inside the Castle to keep them from attracting thieves. Several friends have lost their tongue mounted batts to crooks. My second plus is not having so much corrosion on the terminals during my coastal stays. My AGM batts were almost exactly twice what the wet cells cost.

    1. Four years is about what my AGM's lasted too. Since I can get three years out of wet-cells even when I completely abuse them and they cost half as much I stopped buying the AGM's.

      Of course in my case my batteries are inside in a couple of air-tight battery boxes vented to the outside so the switch was easy.

    2. Even on my trailer tongue my wet cells were very difficult to get to to check the water due to a protrusion of the trailer box. I got very lazy and went to AGM.