Saturday, Oct 16, 2010 at 13:18
You're most welcome Stuart.
Your daily load budget looks to be in the vicinity of 60Ah (fridge: 2Ax24hr, lappy 4Ax2hr, lights: 1Ax4hr).
Due to
battery inefficiencies, you're looking at putting 70Ah back into it every day.
85% of that can be done by quick boost/ and a bit of absorption charging at 14.4~14.8V, and the remainder comes from the solar panel.
Using the 10A charger, the genny will have to be run for 70*0.85/10 equals almost 6 hours.
A 25A charger (which delivers the max recommended charging current for a 100Ah AGM
battery) takes 2.4 hours for the same task.
If 2.4 hours is still unacceptable, then there is an option which requires you to run the genny for only 50 minutes.
Batteries need to be of the spiral wound AGM type for this.
Select two of these 50Ah units wired in parallel.
The charger needs to be able to deliver 70*0.85/0.83 equals 72A, to achieve this feast.
Another option is to use two 25A chargers in parallel, in which case the run time is 70*85/50 equals 1.2 hours.
So these are your options.
For more information on the chargers and batteries, pls
check my profile.
@ Jason,
yes, when on a permanently powered site, definitely select 'power supply' mode.
In this mode, your batteries are being float charged (they only take in very little current during this), and the rest of the 40A on tap is for the loads.
'Power supply' mode is the same thing as a single stage charger permanently set to 'float' level.
Still,
battery temperature compensation is important for best
battery life, so attach the sensor to them.
Note that when left in 'auto', there is the real possibility that the boost voltage is kept up for extended periods of time.
This leads to over-charging and gradual loss of electrolyte.
I estimate this loss to be in the vicinity of 1~3 grams per hour.
In a typical 100Ah AGM
battery, you can afford to lose around 0.3~0.4 litres of water over its life.
So there you have it: if the
battery is left to dry out at the above rate for 10 hours every day, then the
battery will be toast in a few weeks time.
That's why the bulk/absorption stage needs to be controlled very tightly by the charger.
Any interference from concurrent loads during charging potentially shortens
battery life.
cheers, Peter
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