How Long Should Batteries Last Boondocking?

[bobwilcox]

Originally Posted by Mark_K5LXP

The hooey being tossed here about batteries having 50% "actual" or "usable" capacity and such is crap. When challenged, no one who says this can provide any supporting data to prove it, so going forward just know that batteries have all the Ah and cycle life the manufacturers say they do.

'Crown' makes quality deep cycle batteries, for different applications...from their website:

https://www.crownbattery.com/news/wh...hers-die-early

"A deep cycle battery is a lead battery designed to provide sustained power over a long period and run reliably until it is 80% discharged or more, at which point it needs to be recharged. It is important to note that although deep cycle batteries can be discharged up to 80%, most manufacturers recommend not discharging below 45% to extend the life of the battery"

I agree with the battery monitors (I use victron). Using the monitor, Trip breakers to figure out where the amp drain is. Also converting lights to LED will help. I don't winter camp, but do desert camp and it freezes. I use a heavy comforter, and I don't run my furnace until morning before I get up, and I start and run a Mr. Buddy at the same time (usually for 15 minutes +/-)

I would think that 70 AH is a little small. For any RV. I can't imagine someone recommending that size.

[rainmanlarry]

We have the same problem with the heater draining the battery. We just switched to Lithium for $350. We also bought a new monitor. I measure the charge going into the battery. If weak, it should read 14.4 volts, then taper off.

[KJLarson]

70ah ain't going to cut it, just not enough amp hours to do much of anything. I got rid of the little battery the mfg installed and put three 100ah AGM SLA VRLA deep cycle marine/RV batteries in it's place. I run multiple 120 Vac items (2K watt inverter) plus all the 12 Vdc stuff for a couple of days before recharging is needed. My 2K inverter generator will recharge all three batteries in about 3 hrs. My suggestion is to bite the bullet and upgrade the batteries.

[MechEngrSGH]

You are likely having multiple problems, starting with lies told to you by the RV manufacturers (I am a former plant engineer for Safari Motor Coaches);
1) Voltage-based 'battery gauges' (indicator lights) cannot accurately report battery status, especially when batteries suffer capacity loss (which you likely have due to improper charging). To accurately understand how much usable energy you have in your battery, and how much your equipment uses, you need a more sophisticated battery monitor which measures energy in and out of the battery rather than estimating charge based on voltage. These are not expensive and very necessary.
2) To maintain the health of LA batteries they must be frequently and COMPLETELY charged. Charging deep cycle batteries from an alternator in a system that also contains a starting battery is rarely done well. Deep cycle batteries charge more slowly than your starting battery. Newer vehicle alternators also, intentionally undercharge the starting battery and have low system voltages for fuel efficiency reasons. These virtually insure your house batteries will not be properly charged (although they may appear to be). It would be best to assume that you can get some charge from your alternator but without another source that can provide a FULL and FREQUENT charge, your batteries will die an early death.

It is a fallacy that you can get a good charge from your alternator (new vehicles are worse than old at charging). If you want to use your vehicle alternator to recharge your battery, buy a DC-DC battery charger. Optionally, get a substantial solar charging system.

[Charlesland]

It's a long shot, but check to see if all connections are good. I assume you have 2 house batteries. Disconne t and test each separately. Fully charge it, check the voltage with a volt meter (should read about 12.5 volts fully charged with the charger disconnected. Then put a load on it - preferably one that you know the current draw.
Lead acid batteries should last longer than 18 mo the if they have been cared for properly - not allowed to fully discharge, stored fully charged.
If the batteries test good, check for parasitic loads - something drawing current that shouldn't. I bought a clamp on ammeter that measures dc current (most dont) and it is a great tool to chase problems. Our furnace draws less than 10 amps. 2 70 ah batteries should do fine for a nite.

[dtucker300]

Originally Posted by DesertRatz

My Rig: 30' Minnie Winnie 2004 E-450 V-10

My batteries are lead acid interstate brand 70AH 18 months old.

So, after driving all day until 5pm, and the panel shows FULL CHARGE, or batteries were dead by 4 am. We had a couple 12v overhead lamps on for 3 hours, and we'd had the furnace blower coming on about 3 times per hour for 5 minutes each time between 8pm and 4am. At 4am, i heard the furnace delay clicking trying to come on but no dice.

I got up and the panel showed one LED, and one overhead light would barely glow. I turned the engine on for 15 minutes and the panel indicator jumped to read Full Charge. We ran the furnace for Free minutes and the batteries were dead again.

Feels like I'm not getting much out of my batteries, but we don't have a lot of non docking experience.

Comments?

What does anyone know or think about the new Lithium Iron Phosphate batteries that are supposed to last 10 years? Do you need any new special equipment or can you drop them in like the lead-acid deep cycle batteries and charge them with special alterations?

[plumber64]

Sounds like the guy who picked the batteries is not fully versed in the unusual RV electrical world. Might be more expensive but next time go to a certified RV service facility. Not necessarily a dealership, but someone who works on RV's on a regular basis and will give you the straight skinny on batteries.

[rarebear.nm]

Originally Posted by dtucker300

What does anyone know or think about the new Lithium Iron Phosphate batteries that are supposed to last 10 years? Do you need any new special equipment or can you drop them in like the lead-acid deep cycle batteries and charge them with special alterations?

It all depends.

Most lithium batteries being sold for RVs should last about 10 years. Depending how they're treated. Some are much better than others in part because of the built-in battery management systems.

As to needing special equipment, again it depends. Some RVs may already have lithium ready equipment such as inverters, converters, etc. If not already present you're probably facing an upgrade of at least some of these components. Another detail, is that lithium batteries will use all of the amps they can draw from the alternator. This can lead to overloading the alternator and burning it out. There are multiple ways to deal with this issue.

[Micky601]

They can be tested and did you put fridge on propane

[Isaac-1]

Originally Posted by dtucker300

What does anyone know or think about the new Lithium Iron Phosphate batteries that are supposed to last 10 years? Do you need any new special equipment or can you drop them in like the lead-acid deep cycle batteries and charge them with special alterations?

I just upgraded to LiFePo4 batteries in my coach last month, in general I feel that they are better, though each person needs to judge the trait differences with Lead acid for themselves. I also feel that LiFePo4 have reached the point where they make economic sense when amortized over the service life of the battery. My total DIY cost for installing 420 AH of LiFePo4 batteries (a pair of 210AH drop in batteries with smart bluetooth BMS), along with a Renogy 50 amp DC-DC charger with integrated MPPT solar controller, and various cables, fuses, distribution blocks, etc. came to right at $2,000, batteries alone were just under $1,500. Part of this expense was moving my battery bank to an underutilized kitchen cabinet from the exposed under the entry step battery tray, as LiFePo4 batteries don't like temperature extremes, and will not charge at below 32F, or discharge below 14F.


As to those traits mentioned above, this is not a simple better or worse, there are complex issues here, a lot of which involves throwing out many of your preconceived notions of care and feeding of a battery that has came from over a century of living with lead acid batteries in vehicles. For example unlike lead acid, LiFePo4 does not need float charging, and actually last longer if stored long term with 50-70% state of charge, something that would potentially kill a lead acid battery.

[Marine359]

Originally Posted by rainmanlarry

We have the same problem with the heater draining the battery. We just switched to Lithium for $350. We also bought a new monitor. I measure the charge going into the battery. If weak, it should read 14.4 volts, then taper off.

Most LiFePo4 that I’m aware of do not store 14.4v. 14.4 is the charging voltage, and you monitor will show 14.4 when charging, but the battery does not store that. Nominal 100% SOC should be between 13.5 and 13.7v depending on make of battery. I think this is the case with most LiFePo4, but I can’t be sure because I’ve only read specs for about 6 makes before buying mine.

[Charlesland]

Do the math. You need to estimate what percentage of the time your fridge is cooling and the amps it draws. A 5 amp load at 120 volts requires 50 amps at 12 volts (120 volts divided by 12 volts = 10). If the fridge cools 50% of the time, it draws an average of 25 amps (50 amps times 50%).
If you have 12 volt lead acid batteries totalling 250 amp hours, and if you follow advice to only discharge to 50%, then your batteries could operate the fridge for 5 hours (250 amp hours x 50% /25 amps) IF the fridge is the only load on your batteries.

[KanzKran]

Originally Posted by LarryinID

Can’t imagine why anyone that actually camps would consider a residential fridge. They are for people that only use their RVs with shore power.

Originally Posted by Charlesland

Do the math. You need to estimate what percentage of the time your fridge is cooling and the amps it draws. A 5 amp load at 120 volts requires 50 amps at 12 volts (120 volts divided by 12 volts = 10). If the fridge cools 50% of the time, it draws an average of 25 amps (50 amps times 50%).

FWIW, my AC/DC Norcold draws around 5A on DC power, and less than 0.5A on AC. It ran about 40% of the time when I timed it, so about 2A continuous equivalent.

My puny 300W of solar has no trouble keeping the 600Ah battery up, and in fact, it kept it up when one of the three solar panels wasn't connected (from the factory ). But it helps to shut off unneeded loads, including the inverter when it's not needed, and the propane solenoid valve (1-2A continuous; can't remember exactly which), and the wifi access to the Xantrex inverter/charger, etc.

One issue with true residential fridge/freezers is that the published current draw includes the defrost heater, which runs infrequently. This is where I'd try to get first-hand information on actual current draw of the compressor and controls (no defrost) when making a selection as I suspect the current draw for the compressor is very small compared to the published figure.

A spot check of our kitchen fridge, counter depth but big with bottom freezer, reads 1.5A (shows 8.5A on the data plate), but the big and old side-by-side in the basement reads 4.7A (shows 11.6A on the data plate).

Of course, I have no idea what the compressor duty cycle is for either, which is critical to know. Or I could stick a Kill A Watt on there and measure a day's worth of running. But that doesn't help anyone shopping for a fridge unless someone has already done it and can report power figures for a given make and model.

[bobwilcox]

Originally Posted by LarryinID

Can’t imagine why anyone that actually camps would consider a residential fridge. They are for people that only use their RVs with shore power.

Not true. I just switched to a residential fridge, when my Norcold quit. I only boondock (generally) , and also run an oxygen concentrator at night. The fridge (10cu ft) draws 33 watts average (66w compressor 'on') 50% cycle average.. So that's just over 7 amp hours per day.

I have 4 100AH LiFePO4, in series, so run 48v. 800 watts solar on the roof. This time of year is the hardest, with short days. But southern AZ is pretty sunny. I had to run my generator to charge once 10 days ago. I average 25% discharge overnight.

Propane is more expensive than my solar, and propane is no longer my limiting factor, in staying out.