Basic battery charging and solar question

[Boins]

I have a Surveyor 245BHS with 2 6v batteries wired in series. The RV dealer told me that when I'm plugged in to charge, the trailer doesn't recognize when the batteries are fully charged and will keep charging. Off season, I always remove the batteries and periodically set 'em up with a battery tender.

If the trailer does over charge, what is a simple option to create an automatic cut off once the batteries are charged.

Also, I do a lot of dry camping and don't have a generator (I don't need to run the appliances or AC). Is there a simple solar setup that just gives a trickle charge to the batteries while camping? I'm not expecting a solar setup that does a fast recharge, just a trickle.

I'm new to this aspect of battery maintenance and just don't know what things I need to do this properly.

Thanks!

[westend]

If you want to understand how your 12V system is operating, you'll need to have a hand held meter. The meter will also serve as a diagnostic tool if you ever have a problem in the future. Harbor Freight either gives away at events or sells a $3 meter that is adequate for basic troubleshooting and voltage measurement. The learning curve is shallow.

The battery aficionado (I include myself, here) will also have a hydrometer to test the specific gravity of each cell in the battery. A hydrometer is the most accurate measuring device for measuring battery state of charge or establishing a baseline measurement for new batteries. Hydrometers are available online, the best being a Freas glass tube type. It costs $25 or such. Cheaper ones can be had.

Since the OP is just starting out with battery management, looking at the Mfg's website for charging procedures and levels will give a good head start. It makes no sense to advocate a three stage charger replacement if the charger only outputs 13.6 V and the Mfg calls for a charging voltage of 14.8 V on a regular basis. Most pairs of 6V in series that I've seen require charging voltages of 14.8 or higher. Feeding them 13.6 for long time service will shorten their life and reduce capacity.

I believe the necessity of a disconnect switch has been covered.

[scrubjaysnest]

Kayteg1 wrote:
Maybe your dealer knows something about battery charging, maybe not.
The only clear answer will give you a voltmeter hooked up to battery.
If your charger stops charging at 13.5V - it is good one. If goes above 14V -it is killing the battery.
Same with solar charging. You want the batteries to be around 13V in the afternoon. Check the battery manufacturer site what they consider discharged battery and go from there.

This is not correct except for the part about checking the manufacturer site for proper charging.

[webrx]

if you are going to go small, don't go less than 40 watts those little 10 and 15 watt trickle chargers were actually designed for cars to keep the radio memory from draining the battery, I have a 10 watt on top of my trailer that came with it, and while it may make up for parasitic loads, I dont trust it will top the battery off every day. I have a 40 watt and a 100 watt portable system. I used the 40 watt for years, and it would top off batteries by mid day or so the way we camped. The 100 Watt does the same only faster, usually before noon I am charged back up.

d

[Kayteg1]

You will not know how much solar you need till you try.
Bare in mind that batteries have enough power for your needs for few days even without solar. Worse comes to worse, you will need to start the engine for closing the slide.
With good sun 15W is plenty for keeping the battery topped up, but only you will know how much you use.

[Almot]

300W? I think SMK is right.

fridge in LP mode needs 12-15 AH a day, some detectors, LED lights, pumps, DW wants to run kitchen exhaust for an hour, or both of you want to run bathroom fan every time you take a shower or need a toilet just after somebody else had used it...
Total 20-25 AH a day.

100W panel, 6A max in a good sun (hm... in PNW? just look at this summer) - alright, "assuming" a good sun and no trees (no trees in PNW, really?) - alright, "assuming" a good sun - expect solar harvest 20-30 AH a day.

Yep, 100W won't be enough on some (or many) days. No problem if you boondock 2-3 days at a time, battery will gradually drop towards 40-50% by the day three. Big problem if you boondock for a week and weather isn't cooperating.

But... Portable solar over 100W becomes too heavy and bulky. 300W should better be installed on the roof. Not too difficult, but with what you mentioned about your electricity skills, it doesn't meet your requirement of "simple" either.

[time2roll]

Dealer is wrong. You can stay plugged in continuous.

I recommend 100 to 300 watts solar for your trickle charge.
Solarblvd.com has good prices to look at.

[Boins]

Almot wrote:

Boins wrote:

I think 15 watt trickle charger made by Battery Tender is what I'm looking for.

I doubt. 15W is barely enough to provide the charge that your 2*6V lose in 24 hours due to self-discharge. Good for storage and nothing more.

For your uses - lights, pump, slides - you need 80-100W solar.

100W Renogy suitcase $260.

100W solar kit $220. Single panel vs 2*50W of suitcase, less convenient. Prop it against the trailer tongue or make legs of PVC pipe.

Or buy 100W solar panel (many places, Home Depot have some), plus 10A controller, plus some wire, can be done for $160-200 total.

Thanks for the suggestions! Looks like I got a couple of options to consider.

[Almot]

Boins wrote:

I think 15 watt trickle charger made by Battery Tender is what I'm looking for.

I doubt. 15W is barely enough to provide the charge that your 2*6V lose in 24 hours due to self-discharge. Good for storage and nothing more.

For your uses - lights, pump, slides - you need 80-100W solar.

100W Renogy suitcase $260.

100W solar kit $220. Single panel vs 2*50W of suitcase, less convenient. Prop it against the trailer tongue or make legs of PVC pipe.

Or buy 100W solar panel (many places, Home Depot have some), plus 10A controller, plus some wire, can be done for $160-200 total.

[grizzzman]

Boins wrote:
Thanks for the sources. I have a lot to learn about solar before getting something. I don't understand energy lingo so everything I'm reading feels like I'm reading a foreign language!

EDIT:
I think 15 watt trickle charger made by Battery Tender is what I'm looking for. I don't use appliances when camping, nor do I plan to. I just want to keep the batteries charged for the minor light use (all LED), power slide out, power jack and water pump.

Perhaps an example will help. My 2016 trailer pulls .8 an hour with the frig on and the normal parasitics. So .8X24=19.2 amp hours. That's no lights,heater,water pump,etc. A 15 watt panel "may" (but not likely) net 7 amp hours in a day (in the summer) so what does the math tell ya? Solar blvd sells a 100 watt panel for about the same price. It's a bang for your buck thing.

[Boins]

Thanks for the sources. I have a lot to learn about solar before getting something. I don't understand energy lingo so everything I'm reading feels like I'm reading a foreign language!

EDIT:
I think 15 watt trickle charger made by Battery Tender is what I'm looking for. I don't use appliances when camping, nor do I plan to. I just want to keep the batteries charged for the minor light use (all LED), power slide out, power jack and water pump.

[Almot]

Boins wrote:
The RV dealer told me that when I'm plugged in to charge, the trailer doesn't recognize when the batteries are fully charged and will keep charging.

Bad converter or incompetent dealer. Check the voltage, converter may or may not need replacement.

Boins wrote:
If the trailer does over charge, what is a simple option to create an automatic cut off once the batteries are charged.

Decent converter or Trik-L-Charge.

Boins wrote:
Is there a simple solar setup that just gives a trickle charge to the batteries while camping? I'm not expecting a solar setup that does a fast recharge, just a trickle.

Renogy 100W suitcase is simple. It does what can be described as trickle charging (and a little more). No worries about cut-off, this will happen "automatically" every night, and its output amps are low anyway. IMO, not too cheap for what it offers.

"Fast" vs "trickle" - you should read up on 3-stage charging. Small solar isn't fast but high amps don't necessarily mean fast either, because at some point the battery becomes fed up and stops accepting high amps.

The bottom line is - fast recharge from 50% to 100% doesn't exist. People with generators charge it to 70-80% and call it a day. Then they charge it fully on shore power.

[MrWizard]

My wfco, when I had one
Did go to bulk, and did drop to float

Some people have had worst luck then others, with different make converters
I had bad look with powermax converters

[SoundGuy]

donn0128 wrote:
How old is your trailer?

Boins wrote:
Its brand new, the guy who told me was the service tech.

Then the "tech" doesn't know what he's talking about. Years ago, sure, but for at least the last ten years trailers of every stripe have been equipped with converters with at least a 3-stage charger that won't overcharge your battery. Likely as not you have a WFCO converter and while it's certainly not the best (none of any I've owned have ever gone into full bulk charge mode at the advertised 14.4 volts) it certainly won't overcharge your battery. If it's convenient to you to simply plug your trailer into shore power while it's being stored then do so and allow the converter's charging system take care of the rest.

[pianotuna]

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

If you use solar as a battery charger, one rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

https://www.dropbox.com/s/ziwfjk5dnt375cs/Solar%20system%20sizing.xlsx?dl=0

If you full time or use an inverter lots, then populate the entire unshaded area of the roof with panels. I'm considering replacing my awning with solar panels.

For a nice explanation of solar, try this link:


http://www.jackdanmayer.com/rv_electrical_and_solar.htm#The%20Golden%20Rules

[CJW8]

OK, here is the scoop. You need to get a volt meter. The battery indicator on your panel doesn't tell you much. 8 chances out of 10, your trailer will have a WFCO power center. Open it up and find out. While the newer WFCO converters are ok, they are far from the best thing for your batteries, especially being plugged in 24/7. The WFCO advertises 3 modes but it will never go to float mode and it will hardly ever go to bulk mode. A WFCO converter/charger is stuck at 13.6 volts most of the time. While this will not hurt your batteries, over time they will lose water so they will need to be checked every 3-6 months. That is why you need a volt meter, to know what is going on with your batteries. Also google "12 volt side of life" and read it. There is some very good information here. Your service tech is misinformed regarding this matter.