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!

[Boon_Docker]

pianotuna wrote:
But the thread is about a specific AGM unit.

Boon Docker wrote:
The reference was to lead acid batteries.
Some AGM batteries can take a bulk charge up to 15.6v and float of 13.8v. Depends on the brand.
Just saying.

Well this thread sure had me fooled. You must be seeing something that I'm not seeing. I do not see any discussion about AGM ?????

[pianotuna]

But the thread is about a specific AGM unit.

Boon Docker wrote:
The reference was to lead acid batteries.
Some AGM batteries can take a bulk charge up to 15.6v and float of 13.8v. Depends on the brand.
Just saying.

[Canadian_Rainbi]

scrubjaysnest wrote:

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.

Correctd--Kayteg is wrong here. Lead acid batteries need a bulk charge of 14.6 to 14.8 or even a bit higher depending on manufacturer. After a given time (depends on size of battery, starting state of charge and manufacturer, (usually when charge current lowers) voltage will reduce. Constantly charging at 13.5 will likely result in a weak cell failing.

[Boon_Docker]

The reference was to lead acid batteries.
Some AGM batteries can take a bulk charge up to 15.6v and float of 13.8v. Depends on the brand.
Just saying.

[pianotuna]

Hi,

That's a good way to damage at least some AGM jars. One needs to research what the particular battery wants to have feeding it, if the owner wants long life for the bank.

Boon Docker wrote:
6v batteries in parallel require 14.8v (Bulk) and 13.5v (Float).

[allen8106]

Boins wrote:

donn0128 wrote:
How old is your trailer? I have kept my RVs plugged in 24/7 since 1976 with no seriour problems. Check battery water level monthly and quit worrying about things. Your dealer(I assume salesman) is an idiot.

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

If it's brand new the service tech is an idiot. I would venture to say that every new camper comes with some type of staged charger. Best way to know is to find your converter and look up the model number on the net and see what it will and won't do.

[Almot]

You need 25-30 AH a day with a very conservative use. Many people here will tell you that living off 30 AH isn't even possible. Half of this will be used by fridge.

Boondocker is right - to harvest that much, you need 100-120W panel. Double the wattage if it's cloudy.

[Boon_Docker]

A 50 watt will basically cover the parasitic draw per day. That will not keep your battery topped up 100 percent.
I would go for at least 100 watt, which will run you about an extra $50.

[Boins]

Boon Docker wrote:
Yours batteries have got to be close to being depleted. I wouldn't do that long of a trip too often, as your battery life will be shortened dramatically.

Yeah, we take a few long trips each year. That's why I'm considering solar as a charging option.

[Boon_Docker]

Yours batteries have got to be close to being depleted. I wouldn't do that long of a trip too often, as your battery life will be shortened dramatically.

[Boins]

webrx wrote:
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

Thanks for the advice! We just got back from a 10 day trip with no hookups. We were able to use power slide out, awning, tongue jack, water pump, fridge and LED lights. All sparingly but we had enough juice by the end to close it all up with power.

Now knowing that we are able to conserve very well, I think a 50W panel to top off the batteries will suffice.

[Almot]

Multimeter is a must to have in RV. It's not difficult to learn how to use it.

It will tell if battery is being charged, and - in absence of other means - will roughly tell how charged it is. More accurate than those OEM light indicators.

Important is to measure "open circuit voltage", i.e. when it's not charging or discharging. Quick check in the morning, with lights and fans turned off, before solar kicks in. Small solar chargers (even cheap ones), often have volts on display. More convenient than using a multimeter, just make sure that cable from charger to battery is beefy and short, otherwise it will read lower voltage.

Generic table though pretty close. Troian T105 would have 12.1V at 50%.

[Harvey51]

Could use an auto battery maintainer that shuts off when fully charged.
Ebay
I have several of those $5 ones and they work well, except the plastic power cord tends to crack in temps below zero F.
I have a vehicle that is seldom used and then only for a few minutes at a time. The battery is chronically undercharged even with a 12 watt solar panel maintainer. I think this is due to the panel being ineffective without a battery charge controller.

I also am a light user of electricity. The fridge is old with no fan or auto defrost. No TV. The microwave is our breadbox. With a 100 watt solar panel the batteries have not gone below 97% charge all summer (3 trips of 4 days each). I never plug in to shore power or generator.

I agree that the multimeter is an essential tool, great for seeing if the battery is being charged. But not so good for telling how charged it is.

[Almot]

With the OP stated loads, 2*6V will last 3-4 days without any charging before it drops to 50%. Most of this will be eaten up by fridge DC circuit in LP mode.

Being PNW, an average summer day with 100W solar could well be a "no charging" day. 6A max current turns into 0.6A when it rains, and in those parts it could rain all day. There is no remedy for that, other than 800W solar (then it would generate 6A in rain).

OEM panel with Christmas lights for battery "full-half-empty" isn't useful to tell when it's ~50%. At the very least they should get $3 multimeter and measure voltage without any loads. With solar it should be measured first thing in the morning, before solar kicks in, preferably without any loads like lights or fridge cycling.

[Boon_Docker]

6v batteries in parallel require 14.8v (Bulk) and 13.5v (Float).