Reviewing Solar and batteries for retirement

[bdoyle]

Hello, I have a fiver that hasn't had it proper share of use and we are now getting ready to fix that issue. We tend to dry camp but will utilize campgrounds if available. We had solar (120 X 2) and inverter (Xantrex 458 2500 combi) installed in 2003. Batteries have always been an issue due to lack of use and maintenance. I have gone thru 2 sets of batteries (6v X 4) and ready for a third set. Uses lots of water and was thinking that the solar was cooking them. Controller is a Mark PV 22 by Specialty Concepts. Charge was set to 14.4 but I just backed it down to 14.1, so I hope to make them last a bit. We tend to hit the batteries hard in the morning but they can charge up all day with the solar.
Usage:
Hair dryer: 1600 Wts 20 min 53 amps @ 12v?
Coffee maker 870 Wts 20 min 29 amps @ 12v?

Maybe I need 2 more batteries for a bank of 6.
Thanks!
Brian Doyle
Silver Springs, NV

[bdoyle]

I was looking at the larger 300 watt panels to replace the 110s if they was dead. But they look to be functioning properly and I think I can add one more 12v panel up there. Saw a kit with 2 that was over 600 watts. I also just ordered the PWM controller. Oh well...

[Almot]

Max it up, then. One 24V panel @280-300W will take less space than your existing two 110W. You will need MPPT controller with this one.

[bdoyle]

Almot wrote:
Though, the OP 220W doesn't qualify as big.

Those were installed 15 years ago, big improvement over the single 100W I had on my first trailer. Should probably add a third but there is not much real estate up on the roof.

[Almot]

I have a feeling that Westend does what I do, - no loads unless absolutely necessary, i.e. only fridge circuit in daytime. Then it's easy to deduce AH going to battery, given AH of controller output. With a big solar it is "almost" same thing, as system goes into float before noon. Though, the OP 220W doesn't qualify as big.

PS: thought of getting MS 45, but Don Piano steered me in another direction, and was right. Was lucky to get Rogue 30 before they stopped making it. Can change charging parameters right on the controller interface and see AH for a day or longer periods on the same display. Without computer (it has this functionality too, but I never needed it). Few years later Chinese started making controllers with this level of convenience, though not nearly as much adjustability of charging profile.

[MrWizard]

bdoyle wrote:
Forgot to mention, I do have the flow rite watering system installed. Makes thing much easier.

Hair dryer: She says she uses the low setting. With a Kill-A-Watt meter it is using 300 watts. It supposedly takes 5 to eight minutes to dry. 30 amp load plus inverter?
Hopefully steps in the right direction...

should be OK!
1/5 the power for 1/3 time
BIG difference over your OP numbers, 1600w for 20 minutes

[BFL13]

"... see a total of AH delivered to batteries,..."

Ahem, ahem. We know better than that! Ahem, ahem. 🙂

(For others reading, the controller only knows its output, some of which goes to the batteries and some goes to loads.)

[westend]

FWIW, I use a Morningstar MPPT-15 controller. the charge voltage and charge duration can be changed using the included MSview software and a computer. The temperature compensation feature works well, also. Within MSview, an owner can monitor real time charge current, access graphs of daily charge levels, see a total of AH delivered to batteries, either daily or for longer periods. With the MPPT-15 it's also possible to schedule an "equalize" charge event.

My experience with 6V batteries indicate that 14.8 V is a good level of charge voltage for 6V batteries.

[BFL13]

Crabbypatty wrote:
I have had Trojans t125 on my other TT for 10 ....... In our new to us I added 428 watts solar and bought the TriMetric 2030. The Tri Metric measures all kinds off things but I keep it set on Battery %. Simple read. .........

You will get into trouble that way. The %SOC is based on correct entry of battery AH capacity, which changes quite a bit with temperature, plus the AH counter.

The problem is that the AH counter gets out of whack and needs a reset. You can only reset it when the batteries are truly full as seen by hydrometer for Wets or by ammeter (no amps in)with AGMs.

So unless you keep those things current, your battery % figure will be wrong. A member here had that happen because he believed his monitor's % SOC and never cross-checked that with resting voltage per AH count, which you can do with the Trimetric.

The AH counter gets out of whack by not having the exact charge efficiency on a recharge, which us hard to get right, so you use the default for that. EG, you might find your batts are only truly full by hydrometer when the AH counter has gone up to Plus 15AH. Meanwhile, the Bogart instructions have had you at "Full" long before that. ( I really disagree with how they have that organized--I don't use that at all with my Trimetric)

Also, beware of the Tri with solar--read the part about disabling the automatic reset of AH. Otherwise it will reset the AH count every evening when it gets dark and solar charging stops. That can't help the %SOC figure either.

Just mentioning all this in case you really are not cross-checking the %SOC.

[bdoyle]

Forgot to mention, I do have the flow rite watering system installed. Makes thing much easier.

Hair dryer: She says she uses the low setting. With a Kill-A-Watt meter it is using 300 watts. It supposedly takes 5 to eight minutes to dry. 30 amp load plus inverter?
Hopefully steps in the right direction...

[bdoyle]

Well, as a bit of an update:
1) run with a new set of costco batteries for now. If I can get them to live then goto something better later on.
2) Coleman Campstove drip coffe maker. Propane vs batteries. Should work out ok.
3) Morningstare Prostar PS-30M controller. Panels seem to be working ok but controller might be lying to me. Looking for better charging modes. Unloaded panels output 20.6V and 12amp. They are shell solar 110 panels (2X) but 15 years old. Will add RTS and battery voltage sense wire.
4) Probably replace Xantrex and coach controller with a bit more modern controller/charger and a separate inverter. No decisions on that yet.
Thanks for all your help, much to digest.
Brian

[2oldman]

Crabbypatty wrote:
Our new to us TT is beginning its 4th season ou!

Does that mean you bought it used 4 years ago?

[jharrell]

MEXICOWANDERER wrote:
Some higher end inverters have a "load seeker" circuit that turns the inverter on when it sees a load.

But is it a universal truth that the larger the inverter, the larger the idle draw? Some I used to see had ridiculously high idle currents. My Trace is adjustable but I have it set for a minimum 50 watt draw before it comes on line.

My Magnum 3000w has a "Search Watts" feature that does that, but its very annoying with my RV microwave as it pulses every second to detect load and the microwave beeps and resets the clock as it does so.

Otherwise its about a 30w draw with no load for the inverter just being on. Smaller inverters definitely draw less at idle something like the Morningstar Suresine 300w looks like about 5w at idle and it also has a search mode that pulses as well going below a watt.

I made a Youtube video of my Magnum in search mode to show how it functions for another forum: https://www.youtube.com/watch?v=l_jqzY1wNDU

[Crabbypatty]

I have had Trojans t125 on my other TT for 10 years when I sold them, still going strong. We dry camped with a generator. Our new to us TT is beginning its 4th season with the same batteries that I bought new for it. The key to batteries when dry camping whether solar or shore power, is to not let them draw down below 50%. You can check the battery charge with a simple volt meter and a chart (download one at Trojan) or fancier is a battery meter hard wired. For 10 years I used a simple volt meter plugged into the cigarette plug by the tv and Velcro to the wall. Worked Great. In our new to us I added 428 watts solar and bought the TriMetric 3030. The Tri Metric measures all kninds off things but I keep it set on Battery %. Simple read. I have never had to add more than a splash of water. So I think that two things could things could be happening. Your charger is over charging to high a voltage and or you have drawn your batteries down to far. We also have a Xantrax inverter. I found that the entertainment circuit, runs the TV's and some outlets front and rear. I removed that from the 110Volt panel and plugged it into the inverter. Its that way all the time. When dry camping I just turn it on. We watch TV movies, charge our phones pc, etc and when lazy, use the electric coffer pot.I also hanged all the interior lights to LED. We dry camp as much as FHU . I hope this helps you!

[Ski_Pro_3]

pianotuna wrote:
Hi skipro3,

So how do you size the wattage needed with no data? Or the amp-hours of battery bank? (Gosh, honey, the batteries are dead and the 50 watt solar panel doesn't seem to be charging them fully)

I agree that panel failure is rare--but it does happen and did to one of our members here.

Sizing is fairly fixed if it's an RV. The very cheapest battery and solar panel are the ones you don't have to buy. What I mean is that the first thing to do is reduce the load. LED lights, 2 speed fans, more efficient fans, etc. A few dollars on energy efficient loads saves a whole lot on battery and solar sizing.
Once the load is reduced as much as reasonable, a decent clamp-on amp meter will tell you what the loads you do have draw. My LED lights draw .1amp. My old incandescent bulbs drew 10amps. Meaning I can run 10 LED lights for the same amount of power it took to run just one.

Once it's determined what the loads add up to, battery size and duration needs to be decided. Do you need 1, 2, perhaps 3 days of overcast or rainy weather where the temps are low enough to need the heater on 50% duty cycle after dark? Do you camp where the sun can even reach solar panels on your roof? Are there roof obstructions that will partly shade some of the panels? Are you able to park to optimally capture solar energy? Lots of variation. For us, I have 2 banks of 2 each 6 volt batteries, each bank 200ah of gross capacity. At 50% discharge, that's 200ah of storage without any charging. I use approx. 35ah on my worst case camp conditions; overcast, below freezing night time temp weather. Meaning I can last 3 days without any charging before I dip below 50% drain on my batteries. In order to recover a day's use of 35ah, I have 250 watts of solar panels that will peak at just a hair under 10amps output. 4 hours of peak sunshine will recover my batteries. 8 hours of partial, mottled sun will do the same. Anything less and eventually I'll have to run the genny. More likely I'll run the genny for an hour or so, with the AC output powering my on board charger that outputs up to 35 amps. A tank of fuel will run my genny for 8 hours. I figure I got at least 2 weeks of marginal sunny weather w/1 hour every other day genny use capacity based on my worst case load use.