Boiling the Batteries — WildSnow Field HQ Tiny House

Post by blogger | June 7, 2012      

Portahut and tiny house plans. 65-874 square feet.

WildSnow Field HQ 'tiny house' has solar electric.

WildSnow Field HQ 'tiny house' camp trailer has solar electric that needs periodic upkeep.

Our panels are a pair of Koyocera 135 watt units.

Our panels are a pair of Koyocera 135 watt units. During winter, they only get sun for about three hours so we overdid the amount of panel for our install, nothing worse for a PV system than too little panel that leads to a permanently undercharged battery bank.

We saved money on our solar system up at our “portahut” tiny house by using conventional lead plate batteries that need water now and then, along with what they call “equalization.” The idea is that crud builds up on the battery interior and you zap the things with a controlled overcharge (around 15.5 V) to knock it off, along with letting your charge controller do voodoo that gets the batteries voltage “equalized” so one battery isn’t operating at higher voltage than another and thus constantly trying to charge the lesser battery. The process is supposed to happen once every few months (some say once a month). Our Blue Sky controller can equalize automatically once per month, but automating the process produces lots of flammable hydrogen at who-knows-what time of day. Better to be in manual control and switch on the equalizing when you’re not cooking or otherwise operating a nearby open flame in your “tiny house.” Here is how it went:

Battery pair (shown sideways) with some baking soda to neutralize acid seep. Some folks recommend not messing around with baking soda as you can accidentally drop some inside the battery and mess up the acid solution. With a modicum of care, that's not a problem, and in our situation I felt it was more important to neutralize any acid that got on the exterior of the battery. Eye protection mandatory when working with flooded batteries, by the way.

Trojan battery pair (shown sideways) with some baking soda to neutralize acid seep. Our solar consultant at Sunsense Solar here in Carbondale recommended hooking up a charger from our generator to make sure the batteries got max charge for the equalization process, hence the charger clamps you can see in the photo. Turned out that wasn't necessary as the batteries possessed a full charge due to summer sun and light use. The batteries are Trojan L16H, 6 volts 420 amp hours each in new condition at room temperature.

Battery fuse holder for solar system at backcountry skiing camp.

Battery bank connects to controller through a 30 amp blade fuse. I had to access the DIP switches on the charge controller by taking the controller cover off, so I disconnected all loads and sources before messing around with our expensive Blue Sky 2512 charge controller.

Blue Sky controller and IPN Remote Display, showing our battery voltage.

Blue Sky controller and IPN remote display, showing our battery voltage before we started the equalization process.

Removing cover from charge controller.

Removing cover from charge controller so we can access DIP switch settings. As mentioned above, at this time we're leaving the automatic equalization disabled, making it so we have to access the switches each time we want to equalize.

Inside back of controller, DIP switch number 4 indicated by arrows.

Inside back of controller, DIP switch number 4 indicated by arrows.

Battery cell cap, with boil seepage.

Battery cell cap, with boil seepage. Before we began the process we added some distilled water to each cell, then topped off when done. I found that equalizing with the caps off seemed to make less acid mess, but again, eye protection mandatory while messing around.

I’m still not sure the upkeep and hydrogen venting issues with this type of battery are worth the initial cost savings when compared to sealed batteries. For example, when used during winter in a small cabin, you don’t want to be venting in any way that could introduce hydrogen into the interior of your structure. That means a venting system that works with exterior air, thus cooling off the batteries and reducing their capacity. More, even if you set up automatic equalization for flooded batteries such as ours, you still have to check the water level and clean up acid seepage. My advice is to seriously consider spending the extra coin on maintenance free batteries for this sort of small-scale solar install.

Whatever the case, now you know what’s involved with manual equalization and you’ve got an overview of “tiny house” solar battery issues.

See our portahut tiny house category.


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6 Responses to “Boiling the Batteries — WildSnow Field HQ Tiny House”

  1. Scott Nelson June 7th, 2012 4:49 pm

    wow, $859 for a set of plans? $50k for a built unit? I need to go back to being a carpenter… Maybe we could start a subdivision somewhere around here called “Wildsnow acres” filled with tiny houses.

    BTW, I think we need to T&G the inside of your hut Lou, like all those luxury tiny houses in your links.

  2. Lou June 7th, 2012 5:05 pm

    Scott, I was at Lowes today getting a water heater (don’t ask) and saw a paneling display. A brief fantasy ensued. Then the reality hit me of just how great 1/4 inch CDX is for interior paneling (after sealing and aging to prevent formaldehyde problems) and I got with the program. Sorry, there won’t be any T&G in the portahut (grin). Lou

  3. Lou June 7th, 2012 6:06 pm

    That does seem a bit steep for a set of plans. On the other hand, if they’re good plans that work, they might be worth their weight in gold for a person who’s not a carpenter/builder. I can figure out this stuff in my sleep, but that’s because of years of experience…

  4. John Gloor June 7th, 2012 7:49 pm

    Lou, what is the reason for using two 6v batteries in series over one 12v battery with 800 cranking amps? Or using two 12v batteries in parallel for even more run time as long as you solar charger could handle it.

    My old military truck runs on two 12v batteries in series (24V), and I have been fighting different charge levels in each battery. It is the same series setup you are using. I have been thinking of getting a single 24v battery, but they are much more expensive than two 12v batteries.

  5. Lou June 7th, 2012 8:05 pm

    Hi John, I have no idea why, but it’s super common. I think it has to do simply with what’s available on the battery market. Perhaps factories that make batteries tooled up back in the days when all cars were 6 volt, and they just never made the change for their bigger flooded type batteries. But really, I don’t know.

    Also remember that the solar PV batteries have to be deep cycle. They don’t have “cranking amps.”

    But really, I know little to nothing about this issue. The guys at Sunsense or our other solar companies could probably answer in 30 seconds. Or perhaps someone can chime in here? Lou

  6. John Gloor June 10th, 2012 12:43 pm

    Lou, I saw the “420 amp hours” printed in your article, and had a brain fart and typed cranking amps. They are completely different ratings.

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