New batteries dying quickly: help!

[Bambii]

We bought a used airstream with used batteries that were dying very quickly. We thought the best option would be to buy new batteries: two 6 volt golf cart batteries were recommended hooked up in a series. We have two1000 watt solar panels and 1000 pure sine wave inverter. First few days we got the batteries installed we had shore power.

We check into the campground around 2 and there was sun that day. The next day it rained all day and by that night the batteries were totally shot. We used a few lights, house fans, fridge on LP, the inverter with just a couple phones plugged in and the water pump.

I wouldn't think that would be enough to fully drain the batteries dead. Am I missing something? Does this sound reasonable? Are my batteries toast? Says the are rated for 232Amp hours- which seams like a lot. Do ppl not use the water pump and inverter unless using in that exact moment? (I.e.- turn on pump, wash hands, turn off pump?)

Tips, tricks, advice?

[Bambii]

Also- since the previous owners installed solar panels I assumed they also installed a three stage converter. But I'm not sure. Where would I find the converter located so I can check it out? Thanks!!

[mikeinca]

I'm sorry if this seems like an obvious question, but are you certain your new batteries were fully charged after installation? I know you said you were on shore power for several days but if the battery switch was in the disconnect position then your 6V batteries would have been bypassed and not charging. Did you take a voltage reading of the new batteries off of the monitor after switching to battery power? What did it say?

FWIW, we only turn on the pump and inverter when we need to use them. The pump shouldn't be an issue as far as power consumption (just noisy if it comes on briefly in the middle of the night) but I suspect the inverter is a parasitic load when turned on. Maybe you have others....

[uncle_bob]

Hi

In addition to the battery switch / charge issue above ...

Two 100W (rather than 1,000W) solar panels would be "typical" on a 25' trailer. Fitting 2,000W of panels on is tough without using outriggers.

A lead acid battery should not typically be run down past the 50% point. With a 220AH battery stack that would be 110AH. Ratings are at a discharge rate of 10 or 20A. A 1,000W inverter will pull 80 to 100A when running full on. At that discharge rate, a 220AH battery likely has a 160 AH capacity.

Batteries are a bit strange to charge. You will get to maybe 80% fairly quickly. Getting to 100% may take a day. It depends a bit on the charger and there are a couple of other variables. Being *sure* the batteries are topped up takes a bit of time on shore power.

A typical estimate for solar is that you will get 80% output for 8 hours a day. It will be a bit less on flat mounted panels. With 200W of solar you are doing very well if you get an average of 11A for 8 hours. A more reasonable number for a typical install is 8A over 8 hours. You will get somewhere between 1/4 and 1/3 of a 220AH battery from 200W of solar in a day. Looked at against the 110AH max you should use, that's half to 2/3 of the battery.

So 48 hours of operation and 110AH gives you just over 2A of drain. One fan pulls around 1.5A, two fans puts you over budget. LED lights vary all over the place, it's a good bet that a dozen of them put you over budget. The fridge probably pulls 1/2 A off of 12V while running on LP. Your inverter with almost no load on it (but turned on) probably pulls an amp or two. Add all those up, it's *very* easy to go over budget.

So what to check:

Assuming you are on shore power, check the breakers in the power panel. Check the 12V fuses. Checking the shore power converter it's self will require at least a multimeter. Best guess is that it's working. The solar charger is a separate gizmo on a typical install. Same set of checks for it.

You should have various monitor panels in the trailer. A proper solar setup should give you a monitor that at least shows charge amps and battery voltage. There should also be a battery monitor function on one of the other panels. When on charge, the battery / charge voltage should go up above 13.5V. A multimeter is a better way to check this.

Yes, it's a hassle. There are a lot of twists and turns above. Before going on further it's probably worth letting you do some poking and get back with some data.

Bob

[alano]

Don't leave the inverter on if you're not using it. The current drain is not insignificant. The water pump only draws significant current when water is flowing so I wouldn't worry about this one. I would expect you have two 100 W solar panels, not 1000 W panels. You have a total battery capacity of 232 AHr, but you shouldn't deplete them more than 50%, so you have a total of 116 AHr that are usable.

You may not have a three-stage converter. It's not that important since you probably have a three stage battery charger integrated with your solar charger. I don't have a three-stage converter. I'm just careful to not leave the batteries connected to the converter on shore power for extended periods.

My guess is that the fan and inverter running all day depleted your batteries. For small appliances like cells phones, it's more efficient to run a small plug-in 50 W 12 V inverter rather than keeping your 1000 W on all day.

Check your user manual for the location of your converter. What solar charger was installed in your AS?

[Bambii]

Oops! Yes a typo- my panels are 100w not 1000w 😬 the batteries were fully charged. We mostly use the inverter for our weboost. I guess we can use it selectively only when charging devices. I also started running the one fantastic fan at a time. Maybe the battery is ok and we just need to budget better. I was kind of hoping for more 🙄 Would having AGM batteries be better than the 6 volt as far as longevity of discharge? Also at what point in amps are the batteries 50% depleted? The
batteries were 12.8 fully charged. I've heard the standard airstream battery meter isn't very reliable. Maybe we will upgrade at a later date. Thanks everyone!! Great advice.

[uncle_bob]

Hi

The batteries should be about 12.7 if the chargers are both completely turned off. With any charging taking place they should be well over 13V. I would not trust the built in meters. Spend $20 and get a cheap multimeter from Home Depot or Amazon.

The amp hours in a pair of AGM's would not be any better than what you have now. If you can find the space for more batteries, that would help.

The WeBoost can be run straight off of 12V. There is no need to run it via an inverter. The same thing is true of USB charging of a variety of devices.

A generator (even a small one) would extend your "off grid" time by quite a bit. It would weight less than more batteries and would give you significantly more margin.

Bob

[dmbecke]

12.1 is usually the 50% mark

[Al and Missy]

What unclebob said. When you operate a weboost or charge phones from the inverter you start with 12 volts, the inverter changes it to 120 volts, then the power supply for the weboost or the phone charger converts it back to low voltage DC. The inverter efficiency is likely horrible with a light load. Figure out how to operate as many things as possible from 12 volts directly. Use car chargers for phones, iPads, get televisions that operate from a "wall wart" power supply that puts out 12 volts or operate them from small inverters. Using. 1000 watt inverter for 100 watts of load is very inefficient.

Al

[alano]

One of the best tools I could recommend is a battery monitor. These devices measure the current into and out of the battery and they will tell you with great precision how much battery capacity you have consumed in mAhr or as a percent. I can look at mine and see at a glance that I've only consumed, say 20% of my capacity and can start shedding loads when I'm approaching 50%. A battery monitor helps ensure your batteries will last a long time by helping you avoid over discharging them. A volt meter can tell you roughly how much battery capacity has been used but the voltage that you measure is highly dependent on the load. A battery monitor has not such issue.

[Rgentum]

Alano & others on this blog have recommended a battery monitor, & I see they are available on Amazon for approx. $25. My problem is where to install them in my 27FB??? I'd like to install them in the vicinity of the 3-stage charger, but so far I don't see a convenient place to do so, one that has easy wiring access to the electric panel & also doesn't impede access to or with other cabinets etc. Any ideas?

[uncle_bob]

Originally Posted by dmbecke

12.1 is usually the 50% mark

Hi

Well ... that depends...

All the magic voltages will change as you get away from 70F. How much they change depends a bit on which chart you believe. At the temperatures you are likely to see in July, you could be at 50% at anything from 11.95V up to a bit over 12.1V. Proper charging voltages vary even more than that with temperature.

Do batteries life a long and happy life if discharged only to 49.9% and die an immediate death at 50.1%? Of course not. They will live longer if run to 60% of capacity than regularly running down to 40% left. The failure rate depends on a bunch of things so there is no one size fits all number. Best practice is to stay above 50% and to be *very* concerned about running them dead flat (as in < 11V).

Next toss in the fact that there's more than just lead and acid in a lead acid battery. Put a little of this or that in there and the voltages all change by as much as 8%. All of a sudden, 12.0V becomes 12.96 or 11.04V. This is part of why an "old charger" targeted at one chemistry may not be the best thing for new batteries with a slightly different chemistry.

You can then toss in AGM vs flooded to bring in a whole different set of variables.You can also toss it the ever present "you get what you pay for" variation between manufacturers and models.

Yes, batteries are really weird.

Bob

[AirRiggie]

Depending on the model of weboost you are using...most of them actually use 5 or 12 volts, but you were provided with a 110v to XX volts DC converter. Using your 1000w inverter to power those weboost is actually VERY wasteful as far as power consumption goes. Find out exactly what is tha power requirement of your weboost, ie. 5vdc,2amps...and get yourself a DC-DC buck converter to match the power requirement...it is more efficient that way, just make sure you have the proper connector, voltage and amp rating.

[bibbs]

For your phone just use a 12v to USB lighter socket converter. Simple cheep easy!

[alano]

Originally Posted by Rgentum

Alano & others on this blog have recommended a battery monitor, & I see they are available on Amazon for approx. $25. My problem is where to install them in my 27FB??? I'd like to install them in the vicinity of the 3-stage charger, but so far I don't see a convenient place to do so, one that has easy wiring access to the electric panel & also doesn't impede access to or with other cabinets etc. Any ideas?

You won't find a good battery monitor for $25. A good monitor measures the battery current continuously. It does this by using what's called a shunt resistor, which must be installed in series with the battery. Just the shunt resistor alone costs about $30. Check out AM Solar's page for a selection of quality battery monitors.

[uncle_bob]

Hi

Any decent battery monitor will require you to put a shunt right at the battery or at least in a wire that goes only to the post on the battery. Either way there is a hassle factor involved. Without that hassle, you just are reading voltages and guessing at what's going on. A cheap multimeter will do a better job reading battery voltage than any other gizmo you might buy for a similar price. A multimeter, a stick on thermometer and a printed table will probably do the best job, but it still does not do as good as a shunt based device.

Bob

[AirRiggie]

Just in case aome of you still need an inexpensive multimeter that will be beneficial in troubleshooting in situation like these...i would recommend a DC clamp ammeter. I use this unit and it DOES measure DC amperage on the clamp...no need for breaking the circuit and mo need for a shunt resistor. This unit works on the Hall effect principle and of course it also have the regular stuff like resistance, voltage...also for this particular unit, it has a temperature probe, and it also measures frequency.
The meter is Uni-T model UT210D.
I bought mine from a seller in Nee Jersey on Ebay for about $30.00. YES it measure both DC and AC current. WARNING, make sure you purchase UT210D....this series has 210A, B, D and E...A, B, and C only measures AC current
Model E does not have temperature and Hz measurement.

[paiceman]

Its the inverter is my guess. They eat batteries even when you are not actually using them if you leave anything plugged in. As an example, a phone charger will pull when plugged in even if there is no phone attached. If you push the inverter button on the panel off, it's actually still on and your 110V power is running thru it.

On our trailer, a 2017 Classic I can actually go to the inverter and turn it completely off, which I've done and the panel then does not come into play. But, our 110V does not run thru the inverter on our model. We simply don't use it and if we need something charged when no shore power we use a small hand held inverter OR plug the charger into our trucks inverter. A meter will help in your search.

[TouringDan]

Like others have said, don't go through an inverter to charge cell phones, etc. Install some 12v receptacles and USB adapters and use these. Also install a permanent DC voltmeter. This allows you to read your battery voltage easily. All are available from Amazon for about $10 each.

We usually drycamp and have two golf cart batteries. We usually start out at 12.8 volts. After 4 days we typically are not below 12.4 volts. Power is used for LED lights, water pump, charging phones and iPad and use of the Endless Breeze Fantastic fan as needed. No solar as we really don't need it.

Dan

[AirRiggie]

The inverter itself...depending on model, even without load is a parasitic load...my 1000w inverter without load measured at around 0.5 amps...if you leave it on even when not in use is consuming 6 amp-hours a day ! Some models actually consume more than that...the electronics ckts needs power just to be ON.