Battery gurgle

[canicon25]

Hello,

I am new to using a solar panel with my RV. I have a 120W panel and a Renogy Voyager 10Amp PWM controller. My batteries are 2 6VDC flooded in series. I have a simple question. When I hook up my batteries to the panel the controller begins to charge the batteries at a little over 14V. Very soon my batteries start making gurgling noises. Is this normal?? I don't hear this sound when plugged into shore power (my onboard converter/charger is an Elixir ELX-45). Just wondering if these battery noises are normal when on solar?

Thank you!

 

[Gary RV_Wizard]

Not unique to solar - it's the sound of a high rate of charger "boiling" the electrolyte inside the battery. That can happen when charging at a combined high voltage and amp rate. But it doesn't seem that a smart 10 amp solar charger like the Voyager should cause that, at least not by itself.

I wonder if your old Elixir 45 probably is also pushing in amps @ 14+ volts. What level of voltage does the Elixir produce with the solar disconnected? Is it possible it too is charging at 14+ volts at the same time? Typically the solar charger voltage is high enough to make the converter/charger think the battery is fully charged and drop into float charging (around 13.3v), but the Elixir isn't very smart. It might be overcharging by adding it's output to the Voyager amperage.

Frankly, replacing the Elixir with a modern smart converter/charger would be a wise move, but its not a real cheap solution. Here is some info and some more at Elixir Replacement Converter.

 

[canicon25]

Hi. When I have the solar panel hooked up I am disconnected from shore. According to the Elixir manual it seems the maximum DC voltage output with no load is 13.5-13.6volts. The output of the solar controller is about 14.2 volts at about 4Amps ( not an overly sunny day). I have read that can be normal for charging but really want to make sure.

 

[Gary RV_Wizard]

It's generally accepted in vehicle 12v systems that 14.4v should be the max voltage applied and preferably only for relatively short periods, say 30 minutes. That's sort of a de facto convention for max vehicle alternator voltage. So yes, a steady 14.2v can result in over-charging and gas bubbling up fast enough to make noise. However, the Renogy Voyager claims to be a 4-stage smart charger and ought not be be pushing that hard except when the battery bank is low, i.e. only when doing bulk charge. And bulk charge is usually time-limited to make sure it doesn't overdo it.

The smart charging logic, though, is predicated on the batteries being in good operating condition and reacting normally. A weak or shorted cell can distort the feedback the charger sees enough to fool it into poor decisions. I wonder if that might apply here?

 

[Mark_K5LXP]

In the interest of allaying any concern, the effect you're observing is "gassing", the formation of hydrogen and oxygen by dissolving water through electrolysis. Contrasted to the term "boiling" which infers a thermal component that has other more serious implications.

Deep cycle batteries in particular require period of time at a specific elevated voltage for a complete charge cycle. This is the absorb phase, about 4 hours is what is typical for this cycle at 14.4V. Some chargers/converters are smarter about this than others but this is the "spec". During this time the battery will gas, if you look inside the cell you will see a light "fizz" action going on. This is primarly what causes loss of electrolyte that requires periodic replenishment with distilled water. As bubbles of gas build on the plates some of it can become trapped temporarily, until something gives and the bubble rises and makes a "blurp" (technical term). Perfectly normal and expected during absorb phase. Once the charge is complete and voltage is reduced or removed whatever gas remains between the plates will ultimately work it's way out.

Now, the bad cell that Gary mentions is a different story. The input voltage is the same but instead of being evenly divided across six cells, it's only across 5 cells so the voltage per cell is much higher than normal. The battery will gas heavily and if left unchecked will get pretty warm, and ultimately dissolve all the electrolyte. The bad cell is enough to scrap the battery but consequently drying out all the other cells seals the fate.

Mark B.
Albuquerque, NM

 

[Gary RV_Wizard]

In the interest of allaying any concern, the effect you're observing is "gassing", the formation of hydrogen and oxygen by dissolving water through electrolysis. Contrasted to the term "boiling" which infers a thermal component that has other more serious implications.

As Mark says, "boiling" is a misnomer because the action in a battery is rarely heat-driven, but it's the common term for excessive "gassing", i.e. where the electrolysis bubbling is proceeding at a high enough rate to cause significant water loss. Sometimes called "out-gassing", meaning that bubbles are physically escaping via the vents holes in the cells.

So some degree of gassing is normal but a lot is not.

 

[Cameodon]

I would like to say thank you Gary, Mark and Canicon for this very informative thread. I currently have 2/100 watt HQST solar panels permanently mounted on roof af 5th wheel, in parallel (soon to be 4 panels wired series/parallel, to a RENOGY 40 amp MPPT controller to 3 120 AH wet cell deep cycle battery's wired parallel to on board Inverter. (2021 Crossroads CAMEO 5th wheel). I had one of the batteries in a somewhat poor state. I wrongly figured "well its better than nothing so I'll continue to leave it wired up until I can afford to replace it) When home and plugged into 110 so's to run 1 A/C for moisture reasons I disconnect (pull fuse) from the solar. The weak battery boiled the electrolyte dry. I wondered why on just that one battery.. Now reading this thread I know!! thanks again everyone! I purchased 2 more like battery's so no the system will have 4 110 AH deep batteries, which I plan to set up parallel with same length cables to all. Thoughts please??

 

[Mark_K5LXP]

The 4 parallel cables ensures they'll share power as equally as practical but if the batteries are a mix of old and new, you'll get a bit less service life as a set. Depending on how you use them they may still die of other causes first so maybe not a big deal, but for "optimim" performance they'd be a matched set. That being said, I would run a "blended" pack until it expired anyway, as you might as well use them up first. Then let the next set be "optimium".

Mark B.
Albuquerque, NM