TerryIvybridge said:
Turns out the 100 amp battery is 100%. Been on EHU this last week and mover worked well. Just a .35v drop measured by multimeter after the uphill onto the drive. This was from 13.35v beforehand. Is it possible to buy the added 20 or so amps in order to boost the original battery? Wired in Parallel, could this work rather than the expense of a new 110 or higher amperage battery? Possibly be switched so as it would only come into play for such a manoeuvre? particularly after being off grid?
Hello Terry,
Unfortunately it's not quite that simple. If the present 100Ah battery is not being fully charged by the solar panel, adding extra battery capacity won't help, as neither battery will get fully charged.
In practice using a a caravan mover uses much less power than you might think. I have previously estimated that on average a mover will use less than 2Ah of battery capacity, so your 100Ah should be more than capable of running your mover.
If the mover is cutting out because the battery voltage is falling too low, and you have subsequently proven the battery to OK, then it's going to be more sensible to sort out the charging problem to make better use of teh battery you already have.
Solar panels are rated by the maximum power they can produce. Power is measured in Watts (W) and in electrical systems that is affected by the Volts (V) and Current (A). Fortunately Volts x Amps = Watts, and if your panel is 60W, I would expect that to mean if it was running at 12V it would be capable of pushing 5A of current through its wires. But the panels output will have other limits such as a maximum current, and a maximum voltage, so as the batteries terminal voltage rises as it charges, a solar panels ability to push current into a battery reduces.
If this is uncontrolled in other word if a solar panel is directly connected to a battery, depending on the equipment and the conditions, battery may be over or under charged.
That is one reason why a proper solar charge controller is important. Good ones can effectively match the best load conditions to enable a solar panel to maximise is power output, whilst at the same time ensuring the connected battery is correctly charged. But obviously if the solar panel is not big enough or the light conditions are not bright enough to cover any power used from the battery, the battery cannot be fully recharged by solar alone.
There can be other problems with trying to connect multiple batteries in parallel. If on battery is in poor condition relative to the other difference in terminal voltages will cause some very large currents to flow between the batteries when they are connected. This is potentially dangerous as wiring can easily overheat and could start a fire. Battery manufactures will tell you that when parallel connecting batteries, the batteries should be from the same batch and size, and in the same condition, otherwise any electrical load or charging will not be shared correctly, again possibly leading to dangerous overheating of wires or cells.