Charging RV batteries

System

I am interested in getting a solar charging system for my two deep cycle batterys on my 21 foot travel trailer. Often I park in the middle of a field for four to five days, and would like to have a solar panel for recharging the trailer when I use lights or pumps. I really don't want to get a Honda generator, since I detest the noise, even as quiet as they are. Any suggestions on what would be best for me. Not interested in $$$$ systems... just want to be able to use the blower on the furnace, or some lights at night. thanks in advance... New kid on the block.

mike95490

Re: Charging RV batteries

marilyn t wrote: »

Not interested in $$$$ systems...

A 200W panel runs about $920. That can place about 800W into a battery in winter.
Another $250 for good charge controller

My wild guesses:

320Wh A couple of 20W lamps for 8 hours in winter
800Wh A 400w, 12V furnace blower (8 hrs, 15min on per hr)

Need less heater, a sweater, or more solar

System2

Re: Charging RV batteries

Okayyy... so you are saying that I either spend $1000 or I can't recharge a travel trailer during the day to use lights at night? BTW I set the thermostat at 50 and usually don't even do that. I can get a couple of nights out of my double deep cycle batteries in 40 degree weather, but if I dont' move (ie:hook up to the vehicle and drive a couple of hundred miles to recharge) I need to somehow recharge the batteries. Typically, I can get up to 5 days out of the deep cycles before I am in danger of running out of battery in summer use. However, I do need battery for the refrigerator, water pump, furnace fan, and lights. I was hoping to be able to recharge with a reasonably priced solar unit. Am I all wet?

icarus

Re: Charging RV batteries

Read up on this site and as they say, "do the math" Calculate all your expected loads/time (watt/hours/per day)

Be advised that if you are drawing your batteries down to more than 50% you are killing them! Most of us prefer not to draw them down more than 20-30%.

"Deep cycling" of even deep cycle batteries will lead to premature failure. For example if a battery is rated for 500 cycles of 50%, it might get 5,000 cycles of 20%.

Tony

mike95490

Re: Charging RV batteries

marilyn t wrote: »

However, I do need battery for the refrigerator, water pump, furnace fan, and lights. I was hoping to be able to recharge with a reasonably priced solar unit. Am I all wet?

No, just uninitiated. The panels are a huge cost, but they do have a 20+ year lifetime.

An electric fridge will take a lot of power. Do you have a propane option for it ?

Changing your lights to LED's will reduce a lot of power draw. Expensive at first, but you save a lot of power, even over flourscents. I have no idea what the draw of the furnace fan is, but if you can read the label off the motor of it, and guess how many minutes/hr it runs, that will go a long ways to guessing what you can do. But PV panel and controller are going to run you $ 1100 or so. You could get a smaller panel, but you will run out of power, just as you do now.

System2

Re: Charging RV batteries

I think I am being misunderstood.

This is an RV that I use occasionally, not for living in. It is winterized and put up for 6-7 months of the year, with batteries removed and put inside the house on a trickle charger. I am interested in keeping batteries charged for several days while I am parked in the field somewhere, specifically this August in Utah, and then Colorado.

The refrig is on propane, with very minimal electric needs for the thermostat controls. One, maybe two lights are on for maybe 1 hour, usually less. Water pump us used sparingly since I only carry 25 gallons of water total, and I can make that last 5 days. The furnace is also propane, and for example was used for two nights on a recent trip into N.Dakota to keep the trailer at 50 degrees overnight when there was ice on the water outside. I have plugged into a honda 2000 and it is capable of recharging, but I need to do it almost daily. If I drive to another location, and it is at least 4 hours, then the batteries recharge off the car while driving. The trailer was sold to me 10 years ago with only one battery, and I added the second in order to get another day or two out of being parked, unplugged.

What I am looking for is a portable solar panel, that I can set up on day one of a 5 day trip, that will keep the batteries up and charged. I know it will extend the life of the battery, but would go a long way to making life easier on the road since I could use a light after dark without worrying about running out of power on day 5.

I have seen small $150.00 solar panels with alligator clips that look like a decent alternative to a honda generator. Are they capable of doing what I want? is that possible, or do I really need a big system?

BB.

Re: Charging RV batteries

It all depends on how much power you use...

Very roughly, for example, a $150 solar panel will be around 30 watts... Based on the sun light available, over rated solar panels (everybody does it), and losses through charge controllers, inverters, and batteries, it will give you around 60-90 watt*hours of useful energy per day (this is a conservative rating--summer in the southwest, you might do slightly better if the panels are tilted up into the sun--installed flat and used elsewhere not during the summer--you will get less)...

Say you use:

10 amp * 12 volt * 5 min / 60 min per hour per day = 10 watt*hours for water pump per day
5 amp * 12 volt * 60 min / 60 min per hour per day = 60 WH per day
1 amp * 12 volt * 120min/60min per hour per day = 24 WH per day
===================================================
94 watt*hours per day usage...

So, under good conditions, a 30 watt panel will just about keep you even, or a slight deficit on a day's use. If you are not using any power (storage, light use), such a panel will more than keep the battery fully charged.

Say you have two 100 amp*hour (20 hour rate) x 12 volt deep cycle batteries and you want them to last a long time, so you want to not discharge them below 50%.

100 AH * 12 volt * 50% = 600 Watt*Hours of useful energy...

And, it is recommended that you don't let them fall below 75% capacity and stay that way without recharging the next day--that would give you about 300 watt*hours of useful energy. If you fall below 75% state of charge--then you should hook up the generator and recharge the battery bank.

-Bill

mike95490

Re: Charging RV batteries

marilyn t wrote: »

I have seen small $150.00 solar panels with alligator clips that look like a decent alternative to a honda generator. Are they capable of doing what I want? is that possible, or do I really need a big system?

Most of the $150 panels are TOYs, they will barely produce any power. They are fine for a small light on an outbuilding, that comes on one or 2 times a week. They are good for trickle charging a stored vehicles battery, so it does not go dead.

http://store.solar-electric.com/poup20wa12vo.html
20 watts of power, $170.

After a full day of sun, it would provide enough power to run an incandescent light for 15 minutes, maybe. Unless you are very miserly in you electric use, a small $150 watt panel will not make any noticeable difference. it will make a difference if you were starting from no power, and you could use a LED light for a couple of hours a night off it.
It's the same as running your Honda generator for 45 seconds, what a small panel puts out in 1 day.

System2

Re: Charging RV batteries

So both of you are basically saying what I want to do is impossible for that amount of money.
Okay... that is what I wanted to know. Thanks everyone.

BB.

Re: Charging RV batteries

Not impossible--but we still don't know how much power you will want to use...

Also, most small solar panels cost almost $10+ per watt, while larger ones are $5.00 per watt or less--the killer is shipping costs for single panels if you cannot find a source locally.

For long term use (9+ months out of the year), solar can be pretty competitive. For occasional short term use (summer weekends), a small Honda eux000i generator is hard to beat--even with the cost of gas.

-Bill

System2

Re: Charging RV batteries

I guess I don't know how much power I need either. Lights are fitted with bulbs like an auto tail light. They can't draw too much power. The only power the frig uses is electronic controls... all cooling is propane. Occasionally, I turn on a ceiling fan for 5 minutes. The water pump is turned off 95% of the time, and only uses electric when I turn on a faucet.

Like I said, two deep cycles installed on the trailer work just fine for up to 5 days. the trailer batteries recharge on a long drive, and when I get home, it gets plugged into the garage, and propane frig switched to electric. the batteries are always recharged when I get home, and stay charged between trips. I have tried to get info regarding wattage usage of the water pump and refrigerator, but can't find 'wattage' use, just volts / amps.

Regarding small generators... any thoughts on the Kipur, vs Yamaha, vs Honda? Reliability etc? I know Kipur is less expensive, but is it 'cheaper' too?
thanks.

niel

Re: Charging RV batteries

for your general info,
volts x amps = watts

i'd also like to know if you have them on a float charger or some multistage charger for ac? if you leave a standard automotive battery charger on your batteries they will exceed the max voltage and start boiling out the electrolyte as most standard auto chargers have no regulation in them. also when you say they last 5 days, if that is to the point of dead then your batteries won't last long. a small pv and controller may help you stave off this extreme discharge, but a bigger pv would be even better. being this is for mobile use you can get some pvs cheaper as they are seconds and/or non nec rated from sunelec.com. even briefly being charged via the alternator may help to keep them from being totally dead, but standard alternators are incapable of delivering a full charge to your batteries, just so you know.

mike95490

Re: Charging RV batteries

marilyn t wrote: »

Regarding small generators... any thoughts on the Kipur, vs Yamaha, vs Honda? Reliability etc? I know Kipur is less expensive, but is it 'cheaper' too?
thanks.

From what I've heard, honda and yamaha are tops. No idea on the record of kipur.

icarus

Re: Charging RV batteries

Automotive tail light bulbs burn ~ 15 watts! They put out the light of 15 watts. A 15 watt cfl will put out the light of ~60 watt bulb! A not insignificant difference.

Tony

BB.

Re: Charging RV batteries

Yes, converting from filiment to LED or CFL's will save you a lot of electricity...

When you say the batteries last you 5 days--is that five days and they go "dead" or 5 days, and they still have an unknown amount of power?

If 5 days and dead--that would indicate that you should not run more than 2.5 days between recharging to keep the battery above 50% state of charge--going below that will dramatically shorten the life of the batteries.

Also, letting them sit below 75% state of charge for a number of days before recharging will also shorten the life of the batteries.

-Bill

System2

Re: Charging RV batteries

Everything on the trailer is standard issue from manufacturer except the second battery. I say I get 5 days, that means the 'battery minder' inside the trailer goes from 'full' (four dots) to 'low' (one dot). At one dot, I get a warning that the refrigerator is needy of power to run properly. Lights still turn on, but I try and find a way to charge up when I get to 'two dots'.

I am very reluctant to hook up to the van and run the van for hours in order to recharge the trailer if I intend to stay in the same location, hence the original question. I have no idea how far the batteries have discharged, at one dot. I tend to get 3-5 years out of a battery. The 'recharging' by plugging into electricity, also is through standard installed power cord on the trailer. It is used to plug in if parked in a campgrounds with power., and intended for recharging batteries also. When plugged in, batteries are not used, and I can use the trailer and it's air conditioner just like I am in a motel. NO limit on usage of anything. On battery, I am VERY conservative, and of course the air does not work.

I have to believe that leaving the trailer plugged in will not harm it

mike95490

Re: Charging RV batteries

marilyn t wrote: »

I have to believe that leaving the trailer plugged in will not harm it

I used to believe in the tooth fairy.

It all depends on the type of charger installed in the trailer for shore power. If it's a brain dead automotive charger, you will cook the batteries after a month.
If it's a true 3 stage charger with float, then you are fine. With batteries having lasted you 4 years, you can't have been treating them all that badly.

Earlier, you mentioned you had a honda generator you used - then you asked about other generators too, do you not have one now ? I mention it, because maybe using the honda to charge the batteries 1x a day for half hour, may be all you need. no solar, just half hour with generator.

System2

Re: Charging RV batteries

I THINK the stuff factory installed on the trailer should be proper for leaving it plugged in. Maybe there is a tooth fairy after all.

Originally I posted this thread to see if there was a simple solar way to recharge during summer sunlight while parked out in the pastures. I am tending to lean towards a generator, and the honda previously mentioned belonged to someone else. I had longed for a cheaper solution than a $1000 honda but if that is what I will need I guess I had better suck it up. I have been getting along fine for about 10 years without either solar or generator, but am looking at a three week trip the end of August. I will drive from Michigan to Utah, park without plug in for 5 days, drive 4 hours to Meeker Colorado, park for 6 days, then go on to Sturgis for another week (600 mile drive) I am not concerned except for the mid stretch where there will only be 4 hours of charging for another extended stay without plug in.

This precipitated this whole discussion.

mike90045 said 1/2 hour with a generator... do you recommend the 1000 or 2000? I tend to live by the rule that more is better and you never know what you might need it for so am leaning towards the 2000.
Again... thanks. for all the info from everyone.

Glenne

Re: Charging RV batteries

Hello Marilyn,

I am a camper also that has recently added some solar cells to increase the time camping without running the generator. We have a motorhome that has 2 12v batteries for the coach. We recently returned from a trip to Colorado where we camped by a river for 13 days. With the help of this forum I was able to get by without running the generator on the motorhome to charge the batteries. We had to use heat at night along with the waterpump and lights. I did go to town once to dump and take on more water. I am sure the alternator on the motorhome did help charge the batteries while doing that. I have one 85 watt pannel and 2 45 watt pannels on the roof of my motorhome using a charge controller that is not that great. I am pleased with the performace of the solar pannels on this trip. We have camped there in the past and if I was able to get 3 or 4 days out of the batteries until the battery lights were down to one light we were lucky. I recently found out that the little lights on the battery minder were not a great indicator of the battery condition. When only one light is out, battery voltage is at a point that could lessen the life of the batteries. These guys on this forum know what they are talking about. Ask on this forum before you buy solar components for your camper. I didn't and purchased a controller that is not as good as it should be. By the way, when we got our first motorhome I left it plugged in all spring, summer, and way into the fall, so we could go camping at a moments notice. I did have to replace the batteries the next spring. The dealer told me that the battery charger in it killed the batteries. They said that it is not made to be connected all of the time, just the time you are actually camping. They did not replace them under warrenty as I thought they should.

Good Luck,

Glenn

mike95490

Re: Charging RV batteries

marilyn t wrote: »

mike90045 said 1/2 hour with a generator... do you recommend the 1000 or 2000? I tend to live by the rule that more is better and you never know what you might need it for so am leaning towards the 2000.
Again... thanks. for all the info from everyone.

If you can, find the label or model of the charger built in. I doubt it feed the batteries more than 20 A @ 15V (300 watts). A bigger generator will not recharge the batteries any faster than the charger will charge them. And your charger was sized for just 1 battery, not two, so it may take a while longer to recharge both of them. So, with that guess, I'd say stick with the smaller , EU1000i . Use the auto throttle, and a new one, given oil changes and clean air, should last you a long time. I suspect the 2000 will burn more fuel, because it can't idle back any more.
Anyway, that's my feelings. You can also look into buying some replacement 12v LED light bulbs - many stores on fleaBay have them, just look up the bulb # you have, say its a #57.
bulb is $8, shipping is $6, so buy all at once, combine shipping charges. Make sure you can return if not liked. For way under $100, you can reduce you power draw, and make your batteries last much longer between recharges. Warm/Soft white is best looking color, White is often blue/green tinted. Maybe a amber one for the porch bulb. (bug lite) If you have a light you often read with, maybe get a 10 watt halogen bulb for it. Good color, if you can't stand the color of the LEDs

If you want very fast charging, you can get a aux charger, but the harder you charge the batteries, the more it wears them out.

n3qik

Re: Charging RV batteries

marilyn t

The built in charger will be your AC/DC breaker box. Give us a model #. Then we can get you more info on the charger.

The last dot/LED is when the battery voltage is at 11 to 10.5 volts.

System2

Re: Charging RV batteries

Going away for the weekend. Iwill try and find the answers to your questions. Thanks for all the help guys.

System2

Re: Charging RV batteries

Just wanted to add a quick note. Most converter/chargers in RVs (trailers too) are at least 40 amp. I frequent another RV specific forum where I've read multiple accounts of 1000w generators being inadequate to the task. They trip their overload breaker because of too much current draw. I suppose it would work if you isolate all other power draws during charging. My thoughts are similar to Marilyn's in that it's better to have too much than not enough. I have a Yamaha EF2800i generator. It doesn't even break a sweat when charging my batteries (stays at idle RPMs). I fill the 3 gallon (I think) tank at the beginning of the Summer, and it lasts all season.

icarus

Re: Charging RV batteries

Most floating neutral generator won't power most big chargers very well. Often times they take many multiples of the output of the charger to run well. The exceptions are (that I know of) are the Xantrex Tc series and some Iota chargers.

The honda eu inverter series will run most chargers quite well, if the generator meets the minimum KVA of the charger. A Xantres TC 20 will run on a eu-1000 quite nicely at idle, but it won't run a TC 40 even though the rough numbers suggest that it should. For example:


"You have an 850 W generator which can surge to 1000 W and try to power Truecharge 40, but the charger never reaches the 40 A charge current level despite the batteries being heavily discharged. What's happening?

The Truecharge 40 is being starved of AC power during bulk mode.

Calculate:

(43 Amps x 13.5 Volts)

---

= 1150 VA
(0.80 efficiency x 0.63 power factor)

1150 VA is the power required by Truecharge during bulk charge.

Although Truecharge will still operate down to 90 VAC input, the drawbacks to an undersized generator are:

- The TRUECHARGE cannot provide the full bulk current of 43A, therefore it will take longer to charge deeply discharged batteries.
- If the generator operates at it's maximum output for a prolonged period it may overheat the generator before the TRUECHARGE goes into the lower power absorption charge.
- We recommend you use at least an 1200W continuous duty generator, and we recommend a 12A AC source in the manual. An alternate solution would be to use the lower power TRUECHARGE 20."

This is from the Xantrex site.

Icarus