How often do you top up open cell batteries?

[Heckler]

We have about twice your battery capacity, more solar capacity plus wind charging. We have only LED lights and an efficient well insulated fridge so I expect our amp hr consumption per day to be similar. The only difference is you will be pulling your batteries down by about twicw the percentage discharge compared to my battery bank as you are about half thr battery bank size. So, does this impact on water consumption? I have found some information on an American webiste that also suggests my batteries are designed for low water comsumption. I dont how they can do that but that is what it says.

Is the water loss a function of heat, ie boiling off or chemical reactions?
Stu

 

[Chris_Robb]

So from what people are saying, does bank size have anything to do with water loss? Our battery bank is probably equivelent to about 900 amp/hr at 12v. We are hardly dropping them over night. Last night I left the inverter on to charge some equipment up. Its been on for 24 hours. Battery bank this morning is at 25.3v with the inverter on. Its 0630 in the morning. Battery temperature is 30degC. So larger battery bank less water loss for the same amps removed daily? Just a guess!

The reason for not having to add water is that your batteries are not gassing. (statement of the obvious)

This might mean that you are never fully charging them or getting nowhere near fully charged. Not that familiar with 24V systems, but doubling the charge rate for 12V batteries - ie 14.4V minimum ie 28.8V, you should see 28.8V reached for some considerable period of time before you go to float voltage (13.8 x 2 = 27.6V). If you decide that you dont needed anymore charge when you have just hit 28.8V and stop charging your batteries will be AT MOST 80% charged.

It is a common misconception that when batteries reach the designated voltage they are charged - they are not! If you are not reaching at least 28.8V then you probably could charge your batteries harder by adjusting the output up (alternator controller) and get much faster charging.

 

[crisjones]

For open lead acid batteries you should be very happy that you are having to add water, this indicates that the batteries are reaching gassing voltage and will be fully charged or very near to fully charged, obviously excessive water usage is not good as this indicates excessive gassing and probably overcharging. If open lead acid batteries are not using any water then they are never getting fully charged and the actual useabl capacity will get reduced over time due, mainly, to sulphation of the plates.
We have a bank of three Rolls Deep Cycle batteries giving a total of 1070AH, I normally add around 2ltrs of water to each battery every 3 or 4 months. We live on board full time and hardly ever use mains charging for 7 months of the year, only solar and alternators. The batteries are now 11years old and a capacity test a few weeks ago indicated that they still have very close to the original AH capacity available so I hope they last for another few years yet.
Generally batteries get an easier life these days than they might have 8 or 10 years ago, mainly because solar is now much cheaper so lots of people install as much solar as they can. Batteries do not get discharged as much and are more likely to get fully charged reasonably often, the two main factors for maximising battery life.
Some people might think our battery water consumption is a bit high but if it means the batteries last 11 years and counting then I am not too bothered. Distilled water is much cheaper than new batteries!!!

 

[geem]

The reason for not having to add water is that your batteries are not gassing. (statement of the obvious)

This might mean that you are never fully charging them or getting nowhere near fully charged. Not that familiar with 24V systems, but doubling the charge rate for 12V batteries - ie 14.4V minimum ie 28.8V, you should see 28.8V reached for some considerable period of time before you go to float voltage (13.8 x 2 = 27.6V). If you decide that you dont needed anymore charge when you have just hit 28.8V and stop charging your batteries will be AT MOST 80% charged.

It is a common misconception that when batteries reach the designated voltage they are charged - they are not! If you are not reaching at least 28.8V then you probably could charge your batteries harder by adjusting the output up (alternator controller) and get much faster charging.

My batteries are normally showing 29.4v by mid-day. If I remove the covers I can see them gassing but clearly they are not gassing enough to need topping up in six months of continual live aboard. We often see 12-13amps (at 24v) going in to the batteries on the solar regulator. In addition the wind generator pushes another couple in. The batteries get fully charged every day. By mid afternoon or earlier they go to float.
Using Mr Google suggests that lead-calcium batteries use less water than lead antimony. Lead calcium in normal in leasure and starting batteries (basically the same things). Antimony is normal in true deep cycle batteries so may explain the variation on water use in batteries to some extend. I think Trojans 105s are antimony as well

 

[TQA]

I have 6 Trojan wet cell golf cart batteries fitted about a year ago. They are not deep cycled on most days dropping to about 75% and charged from a 400 watt solar array controlled by a Blue Sky controller.

I have yet to add water.

 

[geem]

I have 6 Trojan wet cell golf cart batteries fitted about a year ago. They are not deep cycled on most days dropping to about 75% and charged from a 400 watt solar array controlled by a Blue Sky controller.

I have yet to add water.

Thats interesting since we are both in the Caribbean and therefore both running relatively hot batteries. What size bank is it?

 

[macd]

We have about twice your battery capacity, more solar capacity plus wind charging. We have only LED lights and an efficient well insulated fridge so I expect our amp hr consumption per day to be similar. The only difference is you will be pulling your batteries down by about twicw the percentage discharge compared to my battery bank as you are about half thr battery bank size. So, does this impact on water consumption?

That reckoning makes sense but (assuming you have a battery monitor) you might like to compare it with our typical nightly deficit, which is about 50 to 60Ah (11 to 13% discharged). As I suggested above, water usage might be presumed to be higher if the batteries spend a substantial proportion of their charge time on 'boost' charge, i.e. the final 10 to 15% of a full charge cycle, which ours clearly do. I suspect that many open batteries which don't use much water actually don't spend sufficient time in the boost phase to ever become fully charged (which Chrises Jones and Robb both suggest above). Incidentally I confirm charge status by regular hydrometer readings, so can be pretty confident that 100% charged is precisely that.

Using Mr Google suggests that lead-calcium batteries use less water than lead antimony. Lead calcium in normal in leasure and starting batteries (basically the same things). Antimony is normal in true deep cycle batteries so may explain the variation on water use in batteries to some extend. I think Trojans 105s are antimony as well

Trojan T105s are certainly lead-antimony, which does indeed inherently gas more than lead-calcium (as well as having a higher rate of self-discharge).

 

[geem]

That reckoning makes sense but (assuming you have a battery monitor) you might like to compare it with our typical nightly deficit, which is about 50 to 60Ah (11 to 13% discharged). As I suggested above, water usage might be presumed to be higher if the batteries spend a substantial proportion of their charge time on 'boost' charge, i.e. the final 10 to 15% of a full charge cycle, which ours clearly do. I suspect that many open batteries which don't use much water actually don't spend sufficient time in the boost phase to ever become fully charged (which Chrises Jones and Robb both suggest above). Incidentally I confirm charge status by regular hydrometer readings, so can be pretty confident that 100% charged is precisely that.



Trojan T105s are certainly lead-antimony, which does indeed inherently gas more than lead-calcium (as well as having a higher rate of self-discharge).

Our only major consumption at night is the fridge. We have tested the consumption of that alone with an hour run meter and an ammeter. We average quite a bit less than you over night which would explain why we are fully charged a little more quickly. The high battery voltage at 0600 each morning also confirms the very low nightime current use and certainly doesnt suggest the battieries are not reaching full charge during the day. The solar regulator is also entering float mode during the afternoon again confirming fully charged batteries.