battery question

[butchrobbins]

I have a battery bank of 2x4D batteries along with a 40amp 3 stage battery charger that when on the lowest setting or "float" charge provides 13.5V. I am a live aboard and run the charger constantly.

If the charger has a "float" feature is it still possible for the batteries to "boil" over?

 

[Don S/V ILLusion]

Batteries boil only if there is some problem such as a bad cell or is being over-charged at a voltage greater than 13.5. You probably already know keeping them on a float charge constantly will shorten the lifetime.

 

[Snotter]

You should get many years out of your batteries--even living a board. I, too, am a live-a-boarder. Do you have a battery temperature sensor installed for your charger? It is a must in my humble opinion. Though I haven't don't have one yet, you might consider installing a device for de-sulphating (not sure of the exact term) the plates. Also, an AC power supply for your refrigerator is nice for when you are at dock. I bought one off of ebay for 10$.

 

[Stu Jackson]

Why not simply disconnect your charger for a period of time every few days and "use" the batteries?

 

[Bill Roosa]

Battery chargers and boiling

Any decent battery charger should allow you to stay on shore power without fear of boiling the batteries. As you use current it will cycle on to recharge the batteries at whatever rate is appropriate. If I run the inverter to power the microwave the charger goes to 40 (max for my charger) for a few minutes then ramps down to float.

If your batteries are boiling then you either have a bad battery or a bad charger or most likely corroded connections somewhere.

99.44% of all electrical problems on boats are corroded connections.

First clean all the battery and charger and 3-way switch and ground connections. See if that fixes the problem.
If the batteries are still boiling take all the caps off and note the level of bubbling in each cell. They should all be the same. If one is bubbling madly and the rest are quiet then that cell is bad and the battery needs replaced. If they are all bubbling the same then suspect a charger problem.

 

[butchrobbins]

What did you get?

You should get many years out of your batteries--even living a board. I, too, am a live-a-boarder. Do you have a battery temperature sensor installed for your charger? It is a must in my humble opinion. Though I haven't don't have one yet, you might consider installing a device for de-sulphating (not sure of the exact term) the plates. Also, an AC power supply for your refrigerator is nice for when you are at dock. I bought one off of ebay for 10$.

The fridge is the thing. What did you get and how hard is it to convert from DC to AC

 

[butchrobbins]

I may just be an idiot....

I have a battery bank of 2x4D batteries along with a 40amp 3 stage battery charger that when on the lowest setting or "float" charge provides 13.5V. I am a live aboard and run the charger constantly.

If the charger has a "float" feature is it still possible for the batteries to "boil" over?

I really think I overfilled them. I cleaned everything out. Turned the charger off for 12+ hours and made sure there was no leak. Then turned the charger on. It boiled out of multiple cells. I checked the voltage and it was 14.7 during the first and second stages of charging as it is supposed to, then dropped to 13.5 during the float. Gonna check the charger output again on Sat.
thanks for the help

 

[Snotter]

The fridge is the thing. What did you get and how hard is it to convert from DC to AC

I bought a 5 amp PC-like power supply of off ebay that was made for some kind of CCD. My refridge draws about 3.5 amp in the steady state. The inrush current pushes the 5 amp capacity. I'd recommend hunting around for something slightly bigger than 5 amp. Use a single-pole, doubble-throw switch to swap the positive power wires on the DC side of your regrigerators power lead. The DC ground wires (battery and power supply negative wires) can be always connected. You will also need to put a switch in on the AC side of the power supply; or, simply plug the power supply into an AC outlet. A triple-pole, double-throw switch would be nice, illuminating the need for 2 switches.

 

[Hermit Scott]

I really think I overfilled them. I cleaned everything out. Turned the charger off for 12+ hours and made sure there was no leak. Then turned the charger on. It boiled out of multiple cells. I checked the voltage and it was 14.7 during the first and second stages of charging as it is supposed to, then dropped to 13.5 during the float. Gonna check the charger output again on Sat.
thanks for the help

I have 2x135 aH walmart batteries. I have had them for a couple of years now. I refiled them with purified water a couple of months ago and overfilled them. I was at the boat yesterday and there is still a little trickle that sometimes comes out of the vent on the side of the batteries. I was going to try to take some of the water out by absorbing it with a paper towel or something but I was worried about taking out electrolyte with it. So I opted to let it evaporate the water off it's self so it would leave the electrolyte. Apparently it takes a long time for that to happen by it's self.

 

[butchrobbins]

You're right

I have 2x135 aH walmart batteries. I have had them for a couple of years now. I refiled them with purified water a couple of months ago and overfilled them. I was at the boat yesterday and there is still a little trickle that sometimes comes out of the vent on the side of the batteries. I was going to try to take some of the water out by absorbing it with a paper towel or something but I was worried about taking out electrolyte with it. So I opted to let it evaporate the water off it's self so it would leave the electrolyte. Apparently it takes a long time for that to happen by it's self.

I went ahead and took some out and I think you're right. I put the hydrometer on them and most of the cells were in the "fair" range on the good end of the scale.
I wonder if there is a way to "boost" the electrolyte concentration with an additive?

 

[Chuckbear]

I went ahead and took some out and I think you're right. I put the hydrometer on them and most of the cells were in the "fair" range on the good end of the scale.
I wonder if there is a way to "boost" the electrolyte concentration with an additive?

Keep in mind that a hydrometer does not give you an accurate measurement so you should not use that to determine the electrolyte in your batteries. It simply helps you determine a trend or a distinct difference in one cell compared to another. The hydrometer reading is affected by the state of charge, how long the battery has sat once the charge is taken off and even the temperature of the battery compartment. Chuck

 

[Bill Roosa]

What is the resting battery voltage

No way to "boost" your electrolyte concentration except charge the batteries.
Not to be blunt but if "most" of the cells are "fair" are there any that are "not so fair"?
It would be helpful in diagnosing the situation if we knew the resting (2 hours off charger) voltage.
Since you live aboard we could alternately use the present voltage while the batteries are being discharged at a low (~5 amp) rate.