Planning Battery Upgrade--Need advice

[brooklyncowgirl]

Originally Posted by Blackhat6mike

Even Peukert's Law isn't a solid constant! I'm not trying to build a watch, I just want to know what time it is. I'm interested in the real life, no BS, no hype ability of some of my batteries including the ones in my home solar bat bank [D cells] I'll be happy with a generalization and not a carved in stone #.
There was a time when real deep cycle bats came with the amp hr rating stamped on the top. This seems to be a practice has been greatly reduced to only a few brands. Trying to explain to the guy behind the counter that CCA means squat in an RV or storage bank. They just don't get it.

Sears guy stared at me like I had two heads. I walked out, no sense in letting the blind lead the blind. Too bad, once upon a time they used to have knowledgeable people working there--maybe I caught a bad one--or maybe he's jus uncomfortable with women in the automotive department. Walmart--no one there to advise me--didn't think there'd be--I'm not going that route anyway.

Batteries + guy got it once I explained to him that it wasn't going to be a starting battery. He was willing to cut me a two for one deal on some Duracell 6 volts so that sounded promising. Then there's a local company called Tekris which sells both Interstate and Trojan batteries. They specialize in inverters and solar systems. That guy knew what I was looking for. I think we'll contract our dealer and find out what if any weight restrictions there are on our battery bracket before we make a final decision.

[brooklyncowgirl]

OK. First step done. Installed LED throughout. Next up battery. The cheapskate in me says "get a battery to match the current group 24 dual purpose. It's only a few months old. You'll double your capacity for half the $. When they die in a year or two get the battery of your dreams. Meanwhile
Use the $ to buy a 100 watt portable solar panel and use the generator as backup. The librarian in me says get what your research tells you you need. Right now the cheapskate is winning.

[TURBS]

Originally Posted by brooklyncowgirl

OK. First step done. Installed LED throughout. Next up battery. The cheapskate in me says "get a battery to match the current group 24 dual purpose. It's only a few months old. You'll double your capacity for half the $. When they die in a year or two get the battery of your dreams. Meanwhile
Use the $ to buy a 100 watt portable solar panel and use the generator as backup. The librarian in me says get what your research tells you you need. Right now the cheapskate is winning.

I'm on 5 years with my "dual purpose" interstate batteries "group 24"

TURBS
08 duramax tuned n modded
2011 32bhok Sabre
2015 camping "27 nights"

[Klipstr]

Originally Posted by brooklyncowgirl

OK. First step done. Installed LED throughout. Next up battery. The cheapskate in me says "get a battery to match the current group 24 dual purpose. It's only a few months old. You'll double your capacity for half the $. When they die in a year or two get the battery of your dreams. Meanwhile
Use the $ to buy a 100 watt portable solar panel and use the generator as backup. The librarian in me says get what your research tells you you need. Right now the cheapskate is winning.

I like your thinking. When you see what solar can do for you there is a good chance you will expand and get something that mounts on your rig so you don't ever have to fool with it again. If you do that well you can say goodbye to the generator and its noise forever.

A couple of month old battery won't be a killer for a brand new one (unless you really fried it by draining it to zero too many times). Certainly be good enough for a time, perhaps a couple of seasons.

When you are ready to expand to better solar, look at my blog and Handy Bob's blog.

Kelly

[camaraderie]

Originally Posted by brooklyncowgirl

OK. First step done. Installed LED throughout. Next up battery. The cheapskate in me says "get a battery to match the current group 24 dual purpose. It's only a few months old. You'll double your capacity for half the $. When they die in a year or two get the battery of your dreams. Meanwhile
Use the $ to buy a 100 watt portable solar panel and use the generator as backup. The librarian in me says get what your research tells you you need. Right now the cheapskate is winning.

I don't understand how a 100W panel is the answer to your needs. You will get at most...an average of 25amp hours a day from that panel...less than your single battery can provide and not enough to recharge it fully from 50% depletion. I think you need to understand FIRST...how many amp hours use you have daily when you are not plugged in somewhere. Then build your battery system to 2x that capacity....then get a solar panel set up rated at 4x the watts as the daily amp hours you need. (i.e. if you use 50 amp/hours a day you need 200 watts of panels. )

In the meantime...if you don't intend to do THaT analysis over the near term...the librarians decision should be the same as the cheapskates.

[brooklyncowgirl]

We took a trip this weekend and found we used around 35 amps a day--we're doing better now that we have the LEDs. No big problem since we had a generator with us but we hate the noise. Brings back memories of hurricane Sandy.

I found a 6 volt side by side battery box from Century Plastics that will fit my trailer bracket so right now I'm leaning toward spending the money and buying two 6 volt batteries.

As far as solar panels go, I agree at least 200 watt would be ideal for our needs but as I said, I am cheap and want to do this a bit at a time. Whatever we end up doing we want to make sure we have the ability to expand to 200 even maybe 300 watts. If I understand this correctly the controller has to be at least a 30 amp controller or do I have this all wrong.

Has anyone had any experience with these sort of flexible monocrystaline panels? They're more expensive than the standard panels of course but I love the weight of these and the fact that they can be installed by adhesive or even (I'm not sure if I'd trust this) Velcro.

100 Watt Flexible Solar Panel with SunPower Solar Cells=

[camaraderie]

How did you measure that you use 35 amp hours a day without a battery monitor??

Remember that only 2 6 volts means if ONE fails...you trip is interrupted till you can get a new one. Not so with a pair of 12V's...but as long as you are comfortable with that...the 6V's will give you a lot of bang for your bucks.

If the goal could be 300 watts of solar in the future...300 watts divided by 12V is a 25amp current. Most panels are 17+volts which get converted to 12V (with some loss) so 30 amp controller should be more than enough. Try to get an MPPT type charge controller. Since it would be a miriacle to actually get the rated output from a panel...You could most likely get away with a 300 W setup and a 25amp controller. Important to use all the same panel for best performance.
I would not use flexible panels. They don't last as long and the lack of two sided ventilation reduces output significantly on hot sunny days.

(Those with some interest in actual performance of specific panels under lab test conditions may be interested in this link....actual measured wattage is the PTC value) Incentive Eligible Photovoltaic Modules in Compliance with SB1 Guidelines - Go Solar California

[brooklyncowgirl]

Originally Posted by camaraderie

How did you measure that you use 35 amp hours a day without a battery monitor??

Remember that only 2 6 volts means if ONE fails...you trip is interrupted till you can get a new one. Not so with a pair of 12V's...but as long as you are comfortable with that...the 6V's will give you a lot of bang for your bucks.

If the goal could be 300 watts of solar in the future...300 watts divided by 12V is a 25amp current. Most panels are 17+volts which get converted to 12V (with some loss) so 30 amp controller should be more than enough. Try to get an MPPT type charge controller. Since it would be a miriacle to actually get the rated output from a panel...You could most likely get away with a 300 W setup and a 25amp controller. Important to use all the same panel for best performance.
I would not use flexible panels. They don't last as long and the lack of two sided ventilation reduces output significantly on hot sunny days.

(Those with some interest in actual performance of specific panels under lab test conditions may be interested in this link....actual measured wattage is the PTC value) Incentive Eligible Photovoltaic Modules in Compliance with SB1 Guidelines - Go Solar California

Thanks for the input and the link. The 35 amps was very much a ballpark figure. I used a battery tester (one of those $15 Solar things and figured that when the battery got down to 50% that we had used 35 amp hours of power) as my battery is rated at 70 AH. At any rate 24 hours of camping pretty much depleted the battery by 50%. As we do not have a battery charger except for the controller on the trailer I can't guarantee that it was fully charged to begin with. According to my crappy little tester it was at 100%.

[camaraderie]

Originally Posted by brooklyncowgirl

Thanks for the input and the link. The 35 amps was very much a ballpark figure. I used a battery tester (one of those $15 Solar things and figured that when the battery got down to 50% that we had used 35 amp hours of power) as my battery is rated at 70 AH. At any rate 24 hours of camping pretty much depleted the battery by 50%. As we do not have a battery charger except for the controller on the trailer I can't guarantee that it was fully charged to begin with. According to my crappy little tester it was at 100%.

You're welcome....and all I'd add is that without an accurate assessment of your TRUE power use before investing in panels and a controller, you could make a very expensive mistake. Assuming you get the batteries first...suggest you get a REaL monitor second since you'll need one with panels anyway...then you'll know how much you really use and how much panel and controller power you need. Good luck.

[NorSnrub]

I had 2 12v and one failed and drew the other down. I couldn't tell which one failed. I now have 2 6 v and had the same batteries in 2 different trailers for 3 yrs.

[bob caldwell]

Harbor Freight sells Load checkers.

[Klipstr]

For smaller systems I would invest in more panels (assuming I have roof real estate to mount them) before I would invest in an MPPT controller. The gain on those is NOT as advertised. You may see a bit more power but unlikely to see 10% more. If you can get 17V panels use a good quality PWM controller. I like the TriStar and I also like the Trimetric. If you are going to buy the Trimetric meter you might as well buy their controller. That is what I used in my current rig. I have 600W of panels, the Trimetric meter and controller and two six volt crown batteries. Battery failure, if maintained properly, is unlikely. I would not focus on that.

The poster that suggested a very detailed power consumption study is spot on: you can't know what you need until you know what you need (that in honor of Yogi Berra).

The key to successful solar implementation on an RV is in two parts: understand your usage so you can size your batteries and thus your array and make dang sure you wire it all properly using the correct wire sizes everywhere. The most common mistake in installation is wire that is too small for the runs used resulting in insufficient voltage at the batteries during charging. The whole system becomes a waste for want of a buck or two more in wire.

[pgandw]

Originally Posted by NorSnrub

I had 2 12v and one failed and drew the other down. I couldn't tell which one failed. I now have 2 6 v and had the same batteries in 2 different trailers for 3 yrs.

Couldn't agree more. I had 2 size 24 12V in parallel. For some reason, and unknown to me, the converter 30 amp fuses (to the battery) blew. In desperation, I put a 10 amp charger I had on the batteries - it would not handle both at once. So I recharged one battery at a time, but did not get them exactly equal, or one battery had failed (unknown to me).

When I hooked up the 6 gauge parallel wires, the wires promptly melted their insulation and glowed cherry red. The off-gasing of the lesser charged battery had flames at the glowing wires and at the vent at the battery cell cap. With electrician's pliers (gripped on the rubber coating) I cut the wires, which put the fire out.

I replaced with two 6 volt golf cart batteries from Costco ($150 for both). 116 AH available instead of 80AH from the 12V batteries, no risk from unequal battery charges. A lot less expensive than I expected. The batteries were a perfect fit for my existing battery box. And yes I added one of those marine shut-off switches to isolate batteries from camper when desired/needed.

Since our A-frame is set up for long weekends, and not extended stays, I feel much more confident with the golf cart 6 volt setup. I have more capacity, and easier to maintain. If for some unlikely reason one of the batteries dies, we go home earlier on the weekend - the same as if we ran out of propane or water.

Photos to follow.

Fred W
2014 Rockwood A122
2008 Hyundai Entourage (minivan)
camping Colorado and adjacent states one weekend at a time
last trip - last weekend, 4 days in Lincoln, Nebraska

[Klipstr]

HandyBob told me a story about melting a pair of jumper cables between his big battery bank and single battery on the ground. The objective, obviously, was to charge the battery but since the battery was so discharged, the current was so large that it fried the cables. Lesson learned. There is a reason that battery chargers have intelligence in them to avoid this exact scenario. Battery to battery: no such smarts. And with two different batteries, different in age or type or manufacturer, you are likely to have current flowing between the two which you do not want.

Decide on your battery "bank" layout and then build it with new batteries and the correctly sized cables. There is even an argument that the cable lengths should be equal to do this correctly! I don't subscribe to that as the wire is usually fairly large and the runs fairly short so voltage loss is minimal.

[brooklyncowgirl]

Klipstr, I really wish I'd read your last post yesterday morning instead of this morning because I got off the fence and got a mate for my old battery (same size, type, make).

Given the size restrictions and the flimsy looking construction of the battery bracket, two group 24 batteries seemed to make sense. We don't have an exact measurement of our load yet but roughly speaking we know that 24 hours of camping drains our single battery by 30-50% a day. With the need to run the furnace in cold weather and a weekend trip planned for two weeks from now the extra battery power seemed important.

I've installed car batteries, in fact I helped my daughter install one on her car the other day, but have never connected two batteries. You guys have pointed out some great resources so we should be able to do this without disaster.

My plans are to disconnect the existing battery move the battery box. Put the new battery and box in place, measure the cable runs then go out and buy the connecting cables. Once it's all in place we'll do the cable runs, cross our fingers and hope that nothing blows up then connect the trailer and pull out the battery disconnect switch.


A few questions:

1. Do the cables connecting the two batteries need to be the same gauge as the cables which connect the trailer to the battery or will any cable available in my local auto parts store do?

2. The dealer told us that the new battery is around 75% charged. Should the two batteries be at around the same charge before connecting them?

3. The dealer (the same dealer we bought the trailer from) told us that we should discharge the two batteries as far possible then charge them. It will take a couple of discharge/charge cycles before they are totally synced. Is this correct?

4. Anyone know a good You Tube video for doing this job. I've found that whenever doing something new that You Tube is my friend.

[pgandw]

Originally Posted by brooklyncowgirl

1. Do the cables connecting the two batteries need to be the same gauge as the cables which connect the trailer to the battery or will any cable available in my local auto parts store do?

2. The dealer told us that the new battery is around 75% charged. Should the two batteries be at around the same charge before connecting them?

3. The dealer (the same dealer we bought the trailer from) told us that we should discharge the two batteries as far possible then charge them. It will take a couple of discharge/charge cycles before they are totally synced. Is this correct?

4. Anyone know a good You Tube video for doing this job. I've found that whenever doing something new that You Tube is my friend.

1. The battery cables must be at least the same size as the cables which connect the trailer to the battery - they can be bigger without problem. Anything you buy at the auto parts store will typically be bigger (smaller number on the wire gauge). I would not use anything less than #6 gauge wire between the batteries.

2. The batteries must be at identical voltages when you connect them (which usually means BOTH fully charged). See my post several posts above as to what happens when they do not have matching charges (voltages). It was not pretty; I was only too glad to switch to two 6 volt golf cart batteries (fit in the same battery box). You are slightly more at risk for mis-matching since one battery has been used more than the other.

3. Again, both battereis must be at the same voltage (hopefully same charge) BEFORE connecting the two together.

4. There are many diagrams on the Internet. Ideally, the negative wire to the camper goes to the negative post on one battery, and the positive wire to the camper goes to the positive post on the other battery. Link cable #1 goes from battery A positive to battery B positive. Link cable #2 goes from battery A negative to battery B negative. Both link cables should be same length.

hope this helps
Fred W

[camaraderie]

@BCG... Go here for the youtube vid you wanted. FredW has it right.

https://www.youtube.com/watch?v=kd0qwLE5aNI

[Rbertalotto]

I've got to chime in here. My 19 RR had a single 12 V deep cycle battery when I bought it. I replaced it with two group 31 AMGbatteries that I bought from Sam's Club for $179 each. (Bought batteries July 2015) Easily the best deal going. I then installed 280 W of solar on the roof. I changed out all the light bulbs to LED. I have use the trailer on five different three day weekends. Three of the five weekends I required heat at night. On three occasions temperatures got down to the 30s during the night. One night below freezing. So therefore furnace was running every 20 minutes with thermostats set at 60 degrees. Upstate New York and New Hampshire where the areas I was camping. So therefore I was not getting the best sun on the solar panels. I have yet to turn on my generator. Using the 12 V system within the trailer to charge my various electronic devices and to watch TV for approximately two hours a day and run the over stove ventilation for approximately 15 minutes a day and the fan in the bathroom a few minutes a day I have never depleted the batteries more than 20% . Even during a partly cloudy day the batteries were back up to 100% by the end of the day. I am using a trimetric to monitor the battery condition. I am very pleased with this system and it satisfies my needs more than 100%.
This is real world experience.

[Klipstr]

Originally Posted by Rbertalotto

I've got to chime in here. My 19 RR had a single 12 V deep cycle battery when I bought it. I replaced it with two group 31 AMGbatteries that I bought from Sam's Club for $179 each. (Bought batteries July 2015).

I chopped the quote. This is exactly my experience with three different installs. If you do not need to run your air conditioner then you can almost certainly get by with solar and NO NOISY GENERATOR! Without worrying about running out of juice on day three of a long weekend!

I like the fact that this system is relatively modest (no offense intended: I love your system) and it works great! I always put more panels up then are technically necessary. In my case the lowest percentage I have ever seen on any of my rigs was 75%. And in most cases the batteries were recharged before the sun got high in the sky which meant I only was one time where my batteries were taking all the amps the panels could produce. That system was a bit over 1000W with a Tristar MPPT 60 CC. Saw right at the 60A before the CC would clip. We were flat charging the four Trojan T105s that day!

If you need 110V AC you can put in a decent 2000W inverter (skip the battery charging models and the automatic switching models to keep the cost down) and run your microwave, coffee maker and toaster. If you have those kind of loads, however, you probably need four batteries rather than two. If you just need 110V AC to run the TV, use one of the cigarette lighter plug in 300W inverters.

There are so many ways to skin the electricity cat in your RV without resorting to buying a ding dang generator! And installing solar on your rig is damn fulfilling emotionally! Your significant other will be wowed by your prowess!

And the more people we convince of this the less noisy generators we will have to listen to.

Converting the noisy to the sun, one rig at a time...

[brooklyncowgirl]

Thanks to all for your advice. Right now I'm charging my old battery to get the charge equal to my new one. I'll install the boxes tomorrow and then do the hook up.

Next up buy and install a proper voltage monitor and start calculating our actual usage and plan our solar array.

One bit of bad news. My dealer told us that installing panels on the roof would void the roof warranty. We may have to go portable until it expires. Not the worst thing in the world especially in the northeast where you can't always park in sunlight.