Battery capacity

[TG Twinkie]

How long will two 6 volt Interstate batteries wired in series with a 225 AH capacity last with a 280 watt load?
Is my calculation right?
280watts÷12volts=23.3 amps
225÷23.3=9.6 hours

[lewster]

Originally Posted by TG Twinkie

How long will two 6 volt Interstate batteries wired in series with a 225 AH capacity last with a 280 watt load?
Is my calculation right?
280watts÷12volts=23.3 amps
225÷23.3=9.6 hours

Depend on what level of voltage drop you are willing to tolerate for your definition of ' how long will they last.'

You should not draw any lead acid battery below 50% depth of discharge on a regular basis. Your 2 6VDC batteries connected in series will only provide 225 Ah of TOTAL capacity....which implies that you have 112.5Ah USABLE. Series connections increase voltage while the amperage remains the same.

At that level, you should get he following:
280watts÷12.4VDC (average battery voltage)=22.5 amps (approx.)
112.5Ah÷22.5A =5 hours.

Of course, you CAN draw a lead acid battery below 50%, but you either have to re-charge immediately or expect a shorter service life from the battery bank. Leaving ANY lead-acid battery in a depleted state of charge for extended periods will cause plate sulfation and eventual degradation of the battery capacity.

[sgschwend]

You will likely need to factor in the current draw. The higher current draw will result is fewer total AH delivered from the battery. There are curves you can find for lead acid batteries that should show you how that works.

[TG Twinkie]

If the load on the aforementioned batteries has a 50% duty cycle. Will the batteries provide more than the 5 hours of actual run time?
How long would it take a 45 amp 3 stage converter to recharge said battery to the full charge state given 112.5 AH have been consumed?
The current factor is included in the wattage number.

[lewster]

Originally Posted by TG Twinkie

If the load on the aforementioned batteries has a 50% duty cycle. Will the batteries provide more than the 5 hours of actual run time?
How long would it take a 45 amp 3 stage converter to recharge said battery to the full charge state given 112.5 AH have been consumed?
The current factor is included in the wattage number.

Depends on the internal characteristics of the converter. In a 3-stage charger, the initial phase (Bulk) generally applies the full current load to the batteries while increasing the charging voltage to the bulk set point.

Once at the Bulk charge voltage, the charger should then switch to the second charging phase (Absorption) where the charging voltage remains at the bulk set point and the amperage slowly tapers off as the battery accepts the charge.

Once at a pre-programmed transitional point, the charge state again changes to the third phase (Float) where the charging voltage tapers to the float voltage setting along with reduced amperage.

For example: with Lifeline AGM batteries, the bulk/absorb charging voltage is 14.2-14.4VDC. Assume that you are using a Magnum MS-2012 inverter/charger that has a 100 amp charging section. The charge cycle begins at the resting voltage of the depleted battery...... say 12.4VDC and will increase to the 14.2VDC setting during bulk phase....at 100 amps DC.

Once at 14.2VDC, the voltage will remain at that level and the charging amperage will begin to taper and decrease as the battery fills with charge. As soon as the charging amperage (still at 14.2VDC) drops and reaches the programmed transitional point of 1.5A/100amps of capacity, the phase will again change to float and will now be at the float voltage set point of 13.2VDC, where it will remain until a noticeable battery voltage drop is seen and the cycle will begin again.

An added bonus is temperature compensation, which adjusts the charging voltage to a pre-selected algorithm based on the actual cell temperatures at the batteries.

Unfortunately, there is not a single RV converter/charger that works this way. What you get is no temperature compensation and have to accept the manufacturer's pre-set voltages along with their assumed rate of charge acceptance.

It ain't rocket science, but only programmable chargers will give you the exact, adjustable charging parameters that assure proper battery charging every time in all conditions.

[TG Twinkie]

From this info I can assume it would take in excess of 5 hours to recharge the battery to it's fully charged state.
Even with a generator providing the "shore power"
One could assume you would be losing ground if you were to run the generator for 5 hours a day.
Given the time it takes to recharge the battery fully would be in excess of the discharge time.