12V setup for camper trailer.

Terry, good to see someone on the same page. As far as 50% rule! that's just a good guide! ultimately you want to keep a deep cycle battery close to 100% all the time but in real life it's hard. I can guarantee that discharging battery's down to 20 -30% regularly will dramatically reduce battery life. Now if you don't care about buying batteries every year or two than that's fine! However, myself I have lifeline AGM batteries which are not cheap and do not want to be replacing them any time soon, this is why I have a shunt and bmi which tells exactly how many amps are either charging or discharging. This is handy for getting max amps out of your solar panel by adjusting the angle and watching the bmi.

Quote:

---

Originally Posted by Doc130

I can guarantee that discharging battery's down to 20 -30% regularly will dramatically reduce battery life. Now if you don't care about buying batteries every year or two than that's fine!

---

As long as a battery is properly maintained and not abused in other ways, this would only be the case if the battery was cycled down to 20% SoC EVERY DAY.

But for normal RV use, the battery will die of old age way before this sort of discharge had any effect on the battery.

Quote:

---

Originally Posted by loanrangie

I dont have a solar panel yet but will be buying one shortly

---

Hi again loanrangie, and setting up your solar first has a number of advantages.

When your trailer is not in use, if you have your solar set up so it can still be used at home, you can let your solar maintain your batteries in your trailer, removing the need to have to periodically connect a battery charger to them.

Also, as other have posted, try to fit the regulator as close to the batteries as possible but also make sure you connect the solar to the regulator and then the regulator to the batteries with decent size cabling.

Unlike when charging from an alternator, where you have the ability to supply a current over a given length of cable and any lose caused by voltage drop is made up for by the alternator being able to produce more current.

With any solar setup, there is a defined maximum current output of a solar panel, and while PWM and MPPT regulators can increase the voltage at the panel, if there is a voltage drop of any significance, anywhere in the set up, the current lose caused by voltage drop, can NOT be made up, and this will mean a current reduction at the batteries.

So use over sized cabling for you solar set up to keep voltage drop to a minimum.

One more point, the chart Terry posted is an OPEN CIRCUIT voltage chart and not relevant while you are using any form of lead acid battery.

OPEN CIRCUIT voltage charts can also be battery specific and they are only reliable if you have other info to factor in, such as others have posted above, like amps ( watts ) in and out.

If you just take a voltage reading when using a OPEN CIRCUIT voltage chart, the batteries have to be sitting in an unused state, No-Load/No Charge, for at least 6 hours but 24 hours is needed to get an accurate indication of the battery’s SoC.

And again, without other factors being known, using an OPEN CIRCUIT voltage reading has other potential drawbacks, like you can get an OPEN CIRCUIT voltage reading that indicates the battery is fully charged, but apply even a very small load and the battery can go flat in minutes.

The chart below is for getting a fairly accurate indication of the SoC of batteries while they are in use, with a small load of no more than 5% of the total current capacity of the batteries being tested.

For example, if you have 100Ah of battery capacity, the load needs to be no greater than 5 amps.

https://www.aulro.com/afvb/images/im...016/06/640.jpg

Sorry not to sure after comparing the two charts how this works Drivesafe?

You say that chart I put up is not relevant even though if you compare it with the one you put up it is basically the same.

I invite you to go back and compare the two charts and also read all of what I said.

Hi Terry and sorry mate, you are spot on the money, the two charts are the same.

I was on another forum, covering the same subject, just before I posted up here.

Brain does not working too well at that time of the day.

Cheers, Tim

Quote:

---

Originally Posted by drivesafe

When your trailer is not in use, if you have your solar set up so it can still be used at home, you can let your solar maintain your batteries in your trailer, removing the need to have to periodically connect a battery charger to them.

---

Hi Tim,

If solar is not being used to maintain the battery, at which point should you connect a charger to it? Is it bad to leave a charger (3 stage for instance) permanently connected when at home, or are you just wasting electricity?

Thanks,
Kelvin

Thanks Tim, looking at panels right now. One i'm looking at (120W folding ) comes with regulator and wiring for a remote reg setup and shows the ideal setup of reg close to batteries which none of the other sellers do, this makes me more inclined to go that way.
And if i wanted/needed to replace the reg it would be a simple task, using the panel for battery maintenance sounds like a good idea too.

Out of interest LoanRangie what price is the panel and reg?

Many of these solar kits you see on ebay etc might seem well priced at first glance but actually aren't very good value when compared the prices you often can get good quality panels and regulators for now.

If you have a good quality regulator like a ProStar 30 fitted next to the battery in the camper then not only can you see what your charge input is and what drain you are taking out of the battery but you can see how much charge you have left in the battery. plus you can add more panels later without a worry because the regulator is up to it and if you have good quality cabling then you can have the panels a little further away to follow the sun if you don't have a choice because where your parked.

Looking at sub $200 for a 120W folding panel, from the members here with similar panels i dont think i need to spend any more on the panel but possibly the reg at a later date if i need to.
If i was only buying the panel on its own i might spend more but in the next week i'll be a buying fridge, 2 x batteries and the panel plus associated wiring, sockets and cable etc to wire the camper.

I've got a relatively cheap panel and it works fine - I can get about 8.2 amps out of it in full sun, but that drops quickly when any shade is present. I believe the more expensive panels cope better and output more power in part shade.

Ideally I would mount mine so it runs all the time so keeps the batteries fully charged at all times while not in use (mine does this now) but is removable from its mounts so it can be moved around more easily at a camp site (which mine can't be)