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A different look at lithium battery replacement
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Just to stir this pot a little bit is my amazement about battery power as relates to dry camping.
Almost every coach is equipped with a large capable, reliable long life diesel generator that we drag around with us everywhere we go. If we are not running between power poles why do we even care how much battery power we carry with us? Why not get in the habit of running the generator hard and often, even if it is just to run an A/C while we have a sandwich at a rest area?
The cost is likely going to be less than 1/2 gallon per hour or about $.90 and the frequent use of the generator frees us from giving a damn about how long we can go between auto-starts or if the wife should run a hair dryer while eggs are frying on the stove.
My batteries are for when I sleep, and that is not the case if I need heat or air because in those instances I am running the generator. All night long if necessary.
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Thank you guys the information is very helpful . I think my next move will be to replace my 21 year old Amana . She works great and I love how she blends however 100-150amp @ day seems a high price for a look . After all Form does follow function .
Jon, I also do not mind running the genny and there have been times i needed to run her due to poor park electric . Yes i did think about my neighbors but with temps in the 100 s i did not think any windows would be open .
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In the article I talk a lot about how running the generator is the cheapest, easiest, and best way to power your coach while away from a power pole. But, almost universal feedback I receive is owners just don’t like doing that. They think it disturbs the neighbors no matter how quiet the quiet box is and/or they think it stinks.
That single issue is what seems to drive much of the movement to lithium batteries. A little Robinson Caruso likely also plays a role, but the feedback I get is usually couched in terms of “how can I go longer between times I have to run the generator”. The answer is to measure battery capacity remaining when you first get up in the morning. No matter where you are or how you live in your coach you want 20% to 30% capacity remaining to make sure you do not run out of battery capacity in the middle of the night.
There are several ways you can fine tune your system and/or how you live in your coach to achieve that goal. Most of those steps are simple and inexpensive while others are costly.
A great place to start is by learning to live on better terms with the generator. If you are not willing to do that, then start by relieving your lead acid batteries of the burden of powering your 120VAC appliances through an inverter. That is the essence of this “Best of Both Worlds” approach.
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One additional note on residential refrigerators. All new refrigerators carry an energy use tag. This is a standardized way of estimating the number of watts per year that refrigerator is expected to consume. Armed with that info, you can calculate the assumed average number of amps per day of use it will consume whether powered through an inverter via your nominal 12VDC or 24VDC battery bank or via the power pole. Most brands and models will be about the same at a given price point and size. Only the highly specialized ones designed for marine or off grid use will be significantly different.
Before you change out a working unit, measure it’s real world power consumption in your coach by watching the amp draw on your inverter when it kicks on while you are not on shore or gen power or by using a watt meter if you can easily get to the power plug. Compare that to what you calculate a new refrigerator will consume based on the energy use tag.
Jerry
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Jerry, my repeated suggestions for owners to make extensive use of the generator is based to an extent on the fact not running one is a little hard on a system that may be taxed with some inverter / battery loads, but most of all because of inconsistencies.
We all own Prevost coaches which by all standards are described as luxury coaches. They are exactly that and I presume we buy them because we expect to live in luxury in them.
But if the biggest concern is managing systems so we get the longest time possible between generator operations that doesn’t make sense. I start my generator because I’ll be damned if I want to nurse my batteries by denying myself comfort and convenience. With my generator running I can set all four thermostats and run all four A/Cs so I am comfortable. I can watch TV, cook on the grill or stove or both, my wife can use a hair dryer, and we aren’t running back and forth turning switches on or off to save power.
The point is that it is bad enough having to do some energy management when on RV park shore power, but it is something we are used to and almost all the time no problem. But there are times on shore power if I want to grill outside and run the washer and dryer, plus keep the coach temperatures comfortable I am managing power by turning off some devices so I can use others. So much for luxury.
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Many thanks for this thread. I’ve been kicking around in my mind Lithium and / or solar to help run the microwave for mundane stuff like warm up a coffee or some food.
Seems the more logical all around approach is auto gen start for my 2005 Phaeton.
I read here on Prevost community as I have ambitions to join your ranks and like the level of comfort a Prevost provides.
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Auto-start to me is abuse of inverters and batteries.
Except for the older 3 transformer inverters, the A/C start and stop current draws are hard on inverters. To add to that we pay hundreds of thousands if not millions for luxury and comfort, and then we go down the road with just the front of the coach cool because we cannot run all our A/Cs on inverters.
Start the generator and load it up. The generator is not going to get glazed cylinder walls by loading it heavily, and its life is going to be in the 30,000 to 40,000 hour range. Those generators are meant to run hard and often.
Inverter energy is not free. The alternator is being seriously loaded, and the engine is putting power into running the alternator. It take energy to keep those batteries charged.
Just start the generator and let it sip its less than 1/2 GPH while you enjoy every comfort and luxury the coach has to offer.
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Hi Jon,
Understand what you are saying about the hardships of using Inverters to run a couple roof top or Cruisair units when driving.
However, since our coach has OTR air…are we ok using just inverter power for running the refrigerator, lights, etc.? (Would guess generator would be needed anytime we use convection oven/microwave?)
We will soon be heading out West to CA…and, just want to ensure we are not improperly “training/draining” new Lifeline house batteries.
Chassis batteries are new – but, would expect alternator to care for keeping those fully charged.
Didn’t know if there were additional concerns or things we should be doing for crossing deserts this time of year?
Thank you…just starting to drink from the fire hose and have a LOT to learn. 🙂
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The inverters are not strained at all by normal use of plugs, fridge, TV, etc. and that’s all you need when traveling. Yes, I recommend using the genset for high draw issues such as the convection/microwave and A/C. Our Country Coach has dash A/C from the engine compressor as well as an engine A/C compressor for kitchen and/or bedroom so we can also cool those areas without involving the inverters. It’s Country Coaches version of OTR air without the loss of all of that space.
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All that space that Bill applies to the room needed for OTR is 1/4 bay on each side of the bus for the condenser and evaporator. The remaining bay space is taken up with the fuel tank, sandwiched between the OTR components.
If having another 1/2 of a bay is why folks buy a not OTR coach I cannot imagine how much stuff is carried in the bus.
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1. After abusing our new (2014) AGM batteries by relying on the auto-start for a couple of years, I learned that the Watch-Dog generator auto-start starts the generator at a house battery voltage lower than what is the lowest the AGM batteries should be drained to. Hence the damage.
Now I monitor the AGM house battery voltage and turn the generator on when the house batteries hit about 24.4 volts; 12.2volts for a 12 volt coach.
2. The big 50DN alternator that’s driven by the Detroit Diesel in back doesn’t put out high enough voltage to fully charge the house batteries. I can’t remember the exact numbers, I think Jon knows them off the top of his head. I discovered this fact after running for seven or eight hours on a long trip (and the inverters pulling juice from the AGM house batteries to run the refrigerator and whatever other 120V AC things are running), then stopping for the night in an interstate rest stop, and checking the house battery voltages. I realized the voltages were somewhat below what I’d see after being plugged into shore power over night. This fact has been confirmed by the “smart guys” on the PC Forum a number of times.
After learning this additional fact, now after running all day and then dry camping for the night I will make sure to run the generator for a while to “top off” the AGM house batteries.
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I think Dick is now doing it exactly right.
Generally Prevost has set the 50DN regulator at about 27.7. Keep in mind we are using a bus shell and a bus just has 4 start batteries and that voltage is actually pretty accurate for fully charging those start batteries because of the engine heat they are exposed to.
That voltage is inadequate for the house so the practice of running the generator after a day of driving allows the inverters to top the batteries off, going from bulk, to absorb, to float. Partial charging allows the AGM batteries to get sulfated plates which has the effect of reducing their available amp hours.
If you switch to Li batteries they can tolerate partial charges, but the practice of running the generator at the end of a day of driving benefits the generator, AGM batteries and allows for luxurious living without any energy management.
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I’m on the same page as Dick, but……
I’m going to use a 12v example for simplicity. You unhook from shore power and your batteries are on float at 13.4. You drive all day with the alternator charging at 13.7 volts. You get to your campground and plug in and your inverters immediately go to bulk/absorption charge then in time to float.
So if you started out with 13.4 batteries, charged all day at 13.7, why in the hell would you want a full charge cycle at the end of the day thinking the batteries are not fully charged?
This should be interesting.
Jeff and Lindsay
91 Marathon XL -
Using Lifeline AGM charging specs bulk and absorb is about 28.4 volts. But with some alternator outputs limited to 27.7 the batteries are being maintained, but not fully charged.
When inverter power is applied such as from shore or generator power, most inverters will start out with bulk voltage as soon as power is supplied topping off the battery charge. That small amount of voltage difference is what the batteries benefit from to deal with sulfation. When properly charged the inverters will then go to float to maintain the battery.
None of this applies to Li because they are unaffected by partial charging practices.
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