Thread: 12V caravan battery charging

Originally Posted by bee utey

As for amp-hours, the battery Ah rating is for a new battery under specified conditions and you'd be risking its life to draw all of it out. The 7Ah battery in joel0407's example can only supply around 4Ah at 4 amps load and then it would be quite flat.

Sorry mate.

Mis read it.

Happy Days.

Using "drivesafe" chart.

You woke in the morning and the battery was at 12.2v?
There was 95% sun on that day?
You watched TV for 4 hrs at 3.5amp/hr = 14AH.
You checked the battery again at 12.36v

So the battery still went up 10%, according to the chart, with 14AH coming out?

If the sun was already up when the battery was checked in the morning, the voltage could have been inflated by power coming from the solar panel. Meaning the battery could have actually been lower than that in the morning and actually charged more than 10% during the day.

If the batteries are 100AH each (just taking a wild guess here), 200AH total. Since 14AH came out then you needed more than 34AH to go in (34-14=20, 20AH being 10% of 200AH) to raise the level by 10%.

Given all the possibilities that could reduce the solar output then I don't think you have too much of a problem. Especially given you might have actually raise the level more than 10%.

Happy Days.

I just went back and read the original post again 310AH of storage. so 31AH needed to go up 10%, plus the 14AH that was used. That's 45AH of solar for the day.

Given we are in the middle of winter with the shortest days of the year. That probably isn't that bad? Maybe?

Happy Days.

Hi Pedro, this all makes interesting reading but I'm not sure if you have an equipment problem.
Firstly your panels, 310 watts worth I think you said, remember that's flat out down hill with a tailwind and a used car salesman's smile. Are they roof mounted or separate from the van and where is the reg in relation to the panels/batterys ? Are they facing north and tilted ?, just trying to get an idea of your setup. I assume your reg is set to Gel not sealed or flooded ? which should give 14 volts charge (no equalisation boost) and a float voltage of 13.7 volt. How many panels and what type(s), how are they connected and are they dioded ?
Sorry for the 1000 questions but am trying to get my head around what you've got.

If you've got power to burn why not disconnect the oldest and odd man out Gel battery from the string and see how the AGM's go ?
You could also perhaps connect the Gel only to the power supply and give it a good charge or as good a charge as a non battery charger can. This power supply is good for 18 amps at a settable voltage of somewhere between 10 and 14 volts, what's yours set at ? Leave all the wires connected together just disconnect the battery, maybe easier said than done without seeing what you've got .

As an aside what's this talk of 'amps/hour', there is no such unit, it's just a bull **** term invented by Waeco in their advertising. Current is measured in Amps, that's it, no minutes, no seconds hours or millennia, just Amps. Battery capacity is measured in Amp Hours, usually at a 20 hour rate. Both are different units giving different information, but there is no such thing as Amps/hour. One of the reasons I won't have a Waeco product is that any company that makes up it's own units or is too dumb to recognise a counterfeit unit is not a company I would trust. (rant over).

Deano

the panels are flat on the roof of the van, though I'm sure its only a matter of time till a caravan manufacturer has "self aligning roof top solar panels" (did we just invent something?).
just reconnected all batts,, Regulator(set at Gel) showed green untill the two AGM's were connected, then back to amber, system showing 12.78

just a quick question from left field--
The Morningstar reg has 8 cable ports, the two on the left for inwards solar, then two to the batts, then two for "sense" then load.
should the two inwards solar ports be the panels rated V output?

Originally Posted by joel0407

That's a bloody handy chart there. Thanks mate.

LR should have it in the D3/4 handbook

But then again most people don't read it......

Originally Posted by Pedro_The_Swift

............... The Morningstar reg has 8 cable ports, the two on the left for inwards solar, then two to the batts, then two for "sense" then load.
should the two inwards solar ports be the panels rated V output?

from the Morningstar manual.

...................Note that the middle 2 terminals are for sense (with the smaller wire slots in the case).

The solar controller connectors are (from left to right)

Solar +
Solar -
Battery +
Sense +
Sense -
Battery -
Load +
Load -

Re-check your wiring, hopefully it's just your description that's wrong .

The solar input voltage will vary considerably and is determined by sunlight, load and other variables, if it drops below around 14 volts you're getting nothing in. An MPPT reg will try and maintain the input voltage to the most efficient panel voltage, usually around 17 volts for a good '12 volt' solar panel. Your Morningstar isn't an MPPT reg but is a very good reg as far as regs go.
It's quite important to have the reg as close physically to the battery as possible and connected with large diameter wire to avoid voltage drop between the regulated output and battery. This is a very common error people make with portable panels with the reg on the back and 10 metres of thin cable to the battery, voltage drop in the cable means the battery charging is very inefficient. Your reg is a bit different here, the extra sense wires are there so that the reg can 'sense' a voltage drop between the reg output and battery and compensate for it. This is an uncommon 'facility' in solar regs.

Deano

Originally Posted by DeanoH

As an aside what's this talk of 'amps/hour', there is no such unit, it's just a bull **** term invented by Waeco in their advertising. Current is measured in Amps, that's it, no minutes, no seconds hours or millennia, just Amps. Battery capacity is measured in Amp Hours, usually at a 20 hour rate. Both are different units giving different information, but there is no such thing as Amps/hour. One of the reasons I won't have a Waeco product is that any company that makes up it's own units or is too dumb to recognise a counterfeit unit is not a company I would trust. (rant over).

Deano

Waeco advertising? amps per hour is exactly what amps is. Watts are probably a better measure of the power usage but when you want to calculate the amount of power it's going to use over a time period then,,,,,,,,Wait, I was going to say amps are better but I guess it really depends on where you come from and you industry. I am an Office Machine Engineer by trade (not doing it now) and I prefer to measure how much power thing will use in amps but some prefer watt/hrs. I played a fair amount with R/C and all batteries are measured in AH so it makes sense to measure everything in amps because you can work out how long the battery will last. It's a handy thing to know because sometimes its better to fit a lighter battery to a heli than go bigger just for the extra capacity and it will use more power carrying it. Some of the Lipo batteries I use can deliver 200amps@16.8-12v continuously for a couple of minutes. Then there are others that prefer watt/hrs like our house power bill comes in Kw.

Happy Days