Maintaining battery charge

BarneyB · 06-06-2020, 07:57 AM

Newby here, new trailer and new to RV'ing.

We have set up our trailer on our acreage, no access to power but we are keeping the battery charged by using a solar panel.

We are facing several cloudy/rainy days and I would like to know if I can maintain charge on my trailer battery by plugging in my vehicle and letting it idle.

Cheers and thanks for the help.

Goodspike · 06-06-2020, 08:35 AM

Not really clear what you're doing. Is the trailer just sitting or are you staying in it? If you're not staying in it, why not just flip the disconnect switch to conserve the batteries. It would mean you couldn't use the fridge, but most the other drains on the battery are pointless if you're not staying in the trailer. Whether your solar panel would continue to charge (maintain) the battery would depend on how it's connected.

As to whether it would charge the battery, that would depend on your tow vehicle. Mine would need to either be set to tow haul mode or have the headlights on, but either way it would be a terribly inefficient way to charge the batteries. A small generator would be a much more efficient choice, and I'm guessing it would probably be faster too.

**creativepart** · 06-06-2020, 11:02 AM

Not every 7-way connector is setup to provide power, but most are. And, I don't think you need your lights on or be in tow haul mode for it to work.

Not the most effecient way to charge, but it's "A" way to charge. Better would be to simply disconnect the battery cables so there are no loads on it. Leave the solar charger hooked up and you should be fine. Power can't flow back up into the solar panel so, it will charge when there is sun and not really discharge if there are no loads on it.

Better yet, take the battery to your garage, connect a low amperage Battery Minder and plug that in. Worry over.

https://www.amazon.com/BatteryMINDer.../dp/B00D7HZ6FC

DavidM · 06-06-2020, 11:15 AM

Well there are several issues to be resolved to answer your question:

1. Do you know how much parasitic load your batteries are under? My trailer only draws a few tenths of an amp or so while in storage if the fridge is off- CO and propane monitor probably.

2. How big are the batteries? How big is the solar panel system? Is it ever shaded other than clouds?

In any case the simplest thing to do is disconnect your batteries while stored. If possible connect your solar panel directly to the batteries. In the winter I remove my battery and take it home and put it on a trickle charger. In he summer months with just a few weeks between campouts, I disconnect the battery from the trailer by unhooking the negative terminal.

But others have pretty well answered the charging by plugging it in to your TV while running question. A much better way is to use a pair of jumper cables from the TV's battery to the trailer's battery and run the TV at idle for a while. Really wasteful of gas and pollution though.

David

Goodspike · 06-06-2020, 11:48 AM

Quote:

Originally Posted by creativepart

Not every 7-way connector is setup to provide power, but most are. And, I don't think you need your lights on or be in tow haul mode for it to work.

As I stated, that depends on the vehicle. For my Chevy Colorado (and I would suspect Silverados) you do. Those vehicles do not necessarily maintain a high voltage at all times the engine is running, so without tow/haul mode on it might not be charging your battery. My truck will go down to about 12.4 volts at times when running, and that probably wouldn't charge a distant (trailer) battery at all.

But yes, whether it will charge at all might be something else to look at in the manual of the towing vehicle.

**creativepart** · 06-06-2020, 11:56 AM

I think the charge line on the Chevy Colorado is hot all the time, even when the engine is not running and the key is turned off.

https://www.coloradofans.com/threads...nector.279634/

Goodspike · 06-06-2020, 12:10 PM

Quote:

Originally Posted by creativepart

I think the charge line on the Chevy Colorado is hot all the time, even when the engine is not running and the key is turned off.

https://www.coloradofans.com/threads...nector.279634/

Somewhat irrelevant in that without the alternator running the connection would not charge the battery, or might actually drain it.

But in any case, from the GM manual directly:

Quote:

The seven-wire harness contains the following trailer circuits:
. Yellow: Left stop/turn signal
. Green: Right stop/turn signal
. Brown: Taillamps/parking lamps
. Black: Ground
. Gray: Back-up lamps
. Orange: Battery feed
. Blue: Trailer brake

To help charge a remote (non-vehicle) battery, press the Tow/
Haul Mode button on the center stack. If the trailer is too light for Tow/Haul Mode, turn on the headlamps to help charge the battery.

But FWIW, I do typically disconnect the trailer plug when camping, just to make sure the vehicles are separated electrically (ignoring ground).

**creativepart** · 06-06-2020, 02:33 PM

Thanks Goodspike, I towed trailers for a dozen years and never ever heard of that increasing the alternator output for charging. It certainly wasn't in my OM. Even at 70 I learn something every day. Now, if I just could remember it all.

Goodspike · 06-06-2020, 05:48 PM

Quote:

Originally Posted by creativepart

Thanks Goodspike, I towed trailers for a dozen years and never ever heard of that increasing the alternator output for charging. It certainly wasn't in my OM. Even at 70 I learn something every day. Now, if I just could remember it all.

Part of it is new, but I'm not sure how new. They figured out that keeping the voltage at over 14 all the time isn't good for battery life. It can overcharge the battery.

I've been following my voltage lately due to my truck sitting around for extended periods due to Covid-19. With the starting value being under 12 volts it will charge at about 14.5 for maybe 30 miles or more. After that it will start to drop and then vary, getting down to 12.5 or maybe lower at times (not sure how low). I think it's also affected by temperature, but I'm not sure how.

Due to this behavior threads over at the Colorado Fans forum will sometimes be posted by an owner who is convinced there's something wrong with their truck! Often they've even had the truck a long time, but maybe installed a new battery and started monitoring their voltage for the first time.

BarneyB · 06-07-2020, 10:43 AM

Quote:

Originally Posted by Goodspike

Part of it is new, but I'm not sure how new. They figured out that keeping the voltage at over 14 all the time isn't good for battery life. It can overcharge the battery.

I've been following my voltage lately due to my truck sitting around for extended periods due to Covid-19. With the starting value being under 12 volts it will charge at about 14.5 for maybe 30 miles or more. After that it will start to drop and then vary, getting down to 12.5 or maybe lower at times (not sure how low). I think it's also affected by temperature, but I'm not sure how.

Due to this behavior threads over at the Colorado Fans forum will sometimes be posted by an owner who is convinced there's something wrong with their truck! Often they've even had the truck a long time, but maybe installed a new battery and started monitoring their voltage for the first time.

Thanks Goodspike, we are staying in the trailer and have determined that we will need a generator at some point just for this situation.

Cheers

Barrie

BarneyB · 06-07-2020, 10:49 AM

We are staying in the trailer at our acreage which is about 90 minutes from home so removing the battery and charging it is not an option. (I do have a battery minder and kept the battrery on though the winter.) I have decided to buy a generator to use in thisd situation.

Thanks for the feedback and help.

Quote:

Originally Posted by creativepart

Not every 7-way connector is setup to provide power, but most are. And, I don't think you need your lights on or be in tow haul mode for it to work.

Not the most effecient way to charge, but it's "A" way to charge. Better would be to simply disconnect the battery cables so there are no loads on it. Leave the solar charger hooked up and you should be fine. Power can't flow back up into the solar panel so, it will charge when there is sun and not really discharge if there are no loads on it.

Better yet, take the battery to your garage, connect a low amperage Battery Minder and plug that in. Worry over.

https://www.amazon.com/BatteryMINDer.../dp/B00D7HZ6FC

Blubugger · 06-14-2020, 05:29 PM

Quote:

Originally Posted by BarneyB

Newby here, new trailer and new to RV'ing.

We have set up our trailer on our acreage, no access to power but we are keeping the battery charged by using a solar panel.

We are facing several cloudy/rainy days and I would like to know if I can maintain charge on my trailer battery by plugging in my vehicle and letting it idle.

Cheers and thanks for the help.

That would approximate the results you would expect trailering/traveling. So, It is a good practice. Remember also, the best thing you can do for your house battery is to "cycle" it. Put a load on it [turn a light on, run a fan etc.] all under battery power only [no PV, no charging. Use the battery for a short period. It certainly helps to have an LED meter to show your battery charge/discharge state. That is why they are called "deep cycle" and that keeps them in tip-top condition.
Good travels!

BobC · 06-14-2020, 07:08 PM

I don't think there's a need to do so. If have a battery disconnect switch so you can eliminate any parasitic loads (but leaving the solar panel connected), you shouldn't have a problem. A disconnected, fully charged battery should be OK for at least a couple of months, if not more, depending on its condition, and your solar panel will extend this indefinitely despite cloudy days.

If you don't have a disconnect switch, it's an easy install, preferably on the negative side, thereby avoiding accidental shorts. There are many varieties. I installed one of these (waterproof) on the top of my battery box and secured the handle with a cord:

https://www.amazon.com/Zoostliss-Bat...2182351&sr=8-8

Others mount directly to the negative battery post but they would require removing the top to operate them. This second type, since it's fully exposed, should always be on the negative post:

https://www.amazon.com/Ampper-Batter...182463&sr=8-10

pobstlmo · 06-14-2020, 07:53 PM

Get an exercise bike, put a generator on it and pedal your way to a full charge, you need the exercise anyway, well that’s what you wife says on Tik Tok!