Yet another battery thread

[epretot]

Thanks. I have had a few people suggest the 6 volt. I'm leaning toward 8 - 6 volt lead acid.

Lithium is just crazy expensive as you know. I assumed electric would be the single biggest expense. Looks like I was right.

[someguy]

https://www.youtube.com/c/WillProwse/videos

https://www.youtube.com/watch?v=3U4ZfQ_IToI

https://www.youtube.com/watch?v=Rp8Hspi4BC4

https://www.youtube.com/watch?v=WVxvBkeY0UY

https://www.youtube.com/watch?v=iy3hga_P5YY <- Best RV battery testing I've seen.

At 18:37 in the video, the cheapest lifecycle battery cost is lithium at 9 cents/KWh stored, versus 19 cents for flooded lead acid.  His lithium batteries were Battleborns, which are crazy expensive.   

The best value in batteries, by far,  is used Tesla battery packs. $1000 for 5.2 KWh usable.   

[dtcerrato]

Scott Crosby has 12 of those Battle Born batteries and enough solar wattage to run a mini split AC & plenty for other stuff in his Silversides completely off grid.
We're of the dinosaur type and stay with flooded lead acid - pinching nickels as 5 group 31 FLA house bank cost half of one of those Battle Born.

[windtrader]

Probably already chimed in here but lithium is far superior in nearly all performance aspects: better capacity to weight, better charge and discharge rate, better durability, better reliability. Cost at retail is higher than LA. DIY 90% less than retail. You need to do some learning but busnuts are generally a DIY crowd so at least check it out and don't let the neigh sayers close the door to a far superior power storage system.

[someguy]

We're of the dinosaur type and stay with flooded lead acid - pinching nickels as 5 group 31 FLA house bank cost half of one of those Battle Born.

My RV presently has a battery box that holds 6 GC batteries.   I'll be replacing them with lithium.

If you watch the last video, even the stupidly expensive Battle Borns are much much cheaper than lead acid in the long run.  Lead acids have very poor performance compared to what they are advertised as. 

[someguy]

FWIW, the cheapest battery is no battery, ie reduce the electrical load.  What do you need to run in your bus such that you need a big battery ?

I converted all the light fixtures to LED except for 2.  I've given up trying to run AC on lead acids.  It is a hopeless goal due to the Peukert effect.  The fridge will run on propane.   The microwave gets run once in a while, but only for a minute or two.  Rarely longer.   Our cook top is propane.  The water pump hardly uses any power.

We have 600W of solar.   I suspect a Tesla battery module would last a long, long time in our trailer as it sits.

I'm on the Starlink waiting list.   Apparently they draw about 100W or 2.4KWh/day.  That is quite a lot when boondocking, but maybe it wouldn't been to be powered 24 hours ? 

There is a big push to residential AC fridges in RVs these days.  A 10 cu ft fridge uses about 300 KWh/year, which is 1 KWh per day, including auto defrost.   I wonder if that can be turned off ?     

[windtrader]

Starlink @ 100w/hr is likely the running draw. I'd be very surprised if the standby draw is more than 5w.


1kW a day for a refrigerator is trivial for a decently sized lithium battery bank. One other benefit many overlook beyond the hard comparisons is the increased usability and comfort by having 120v always on. Once we agree we are not of the roughing it crowd, it sure is be "at home" with all the modern electrical conveniences at the flip of a switch or the twist of a knob. Pole huggers won't notice but the enhanced luxury to the off grid boondocking experience is truly transformative in a positive way.

[someguy]

Nope, Starlink draws about 100 watts, all the time.  The current version anyway.

https://www.loveyourrv.com/starlink-satellite-dish-internet-first-look-setup-test-on-the-rv/

Furthermore, the dish itself has a built in heater.   In the case of snow or frost, the heater is turned on to remove the build up.  This draws more power.

[someguy]

1kW a day for a refrigerator is trivial for a decently sized lithium battery bank.

Sure, but everything has a cost.  Right now Battleborns are $800 for a 100ah 12V battery.   At 80% DOC, you'll get 1KWh of storage per battery.

[epretot]

I'm convinced lithium is better. However. Budget is a consideration.
I will have a generator as well

Without getting into all the details here, I want to be able to go anywhere anytime and have power.

We will have a residential ac fridge, minisplit, lighting, outlets, exhaust fans, etc. I would love to have a dehumidifier.

propane stove and water heater.

We have no use for a microwave. However, we use the instant pot a lot.

As I said before, starting from scratch, so...

[buswarrior]

There is a big push to residential AC fridges in RVs these days.  A 10 cu ft fridge uses about 300 KWh/year, which is 1 KWh per day, including auto defrost.   I wonder if that can be turned off ?   

Depending on the refrigerator controls, the auto-defrost can be interrupted. Seek out the operating logic, and choose the place to interfere. I would install a switch, rather than just disabling it, so you can engage the defrost on your own terms. This will help get your ingenuity running: https://en.wikipedia.org/wiki/Auto-defrost

The other monster power hog in some residential refrigerators is the HEATER around the door to prevent condensation. The early adopters were quick to get that wire disconnected.

The refrigerator schematic is mission critical to making good moves for both.

happy coaching!
buswarrior

[luvrbus]

Times have changed in Rving back in the day you had 1 or 2 batteries for the house with 12v lights or propane lights no inverters  and times were good now people have batterie banks worth more than the rv. I have one of the electrical hogs and can afford the Lithium batteries but my AGM batteries do the job lol so did the golf cart batteries in my other RV's. So called boondocking has changed too now people want to set and watch satellite TV with their AC running in the middle of no where, the world just keeps spinning

[sledhead]

There's no magic bullet.

You need lead to make amp hours. The more you want, the more you need.

Cruise a few battery sites, do some back of napkin math, be sure you are getting your math into similar values, build up to your target voltage for each example and cost your price per amp hour. You'll also find 8 volt batteries, as well as 6 and 12.

Beware that many 12 volt batteries are NOT the proper deep cycle batteries a busnut needs. If it says marine or RV, be very very suspicious...

For the install, get them stacked, in a pull out rack, made by you for the purpose. Too many people waste a ton of floor space, laying them all out.

Size the rack to house the taller Trojans, or L16 battery cases, if you ever feel inspired to go there in the future, and you need total access to the tops, to inspect and top-off water levels. The easier it is to inspect, the more likely it will get done...

The Lithiums are all the rage, but require more than a decades' worth of battery money to get going. Totally unnecessary expense in a vacation coach, and many full timers don't need them either.

Again, apples to oranges, you need their whole cost, lithium cells AND the BMS, if it isn't included, in cost calculation comparisons.

happy coaching!
buswarrior

x2   

I got 10 years out of the 1st set (6 x 6v GC bateries ) and the ones I have now are on year 6

way less cost but yes you will need to add water sometimes

dave

[chessie4905]

I have 4-4d deep cycle batteries. Interstates. Adding water tends to be a pita but that config is what was there when purchased coach. May consider an automatic waterer for it. Won't  go to the newest greatest because to many changes in the battery engineering and prices keep dropping per kw. Then a new type comes out, etc. etc. Plus the specific charging requirements. Don't  boondock enough to justify solar and expensive systems. Maybe in future, but probably not though.

[someguy]

I got 10 years out of the 1st set (6 x 6v GC bateries ) and the ones I have now are on year 6 way less cost but yes you will need to add water sometimes

Golf cart batteries are rated for 750 cycles.   https://www.golfspan.com/golf-carts/best-golf-cart-batteries  And as Morton's video shows, they degrade fast.  A single 6V battery will deliver about 450 watt hours per cycle.   750 cycles x 450 wh per cycle = 337.5 KWh of storage per lifetime.   They cost $100.  $100/337.5 KWh = 29.6 cents per KWh stored.

Battleborns are 100ah @12V, rated for 3-5,000 cycles.  They cost $800.  They will deliver a full 1 KWh at 80% depth of charge.   3,000 cycles x 1KWh = 3000 KWh of storage per lifetime.   $800/3000 KWh = 26 cents per KWh stored.

Tesla battery packs are 5.2KWh usable, will last for 2-3000 cycles.  Sell for $900-$1000, plus a BMS.  2,000 cycles x 5.2 KWh = 10,400 KWh of storage per lifetime.  $1000/10,400 KWh = 9.6 cents per KWh.

Your 6 GC batteries will cost $600.   A used Telsa pack will cost $1000, plus another $1-200 for a BMS controller.   So it is $1200 versus $600 for no watering, twice the capacity, way better load performance, and 3-4x the life. 

This dude is saying 500 cycles for a Trojan and only 300 cycles for a Costco battery.
https://www.youtube.com/watch?v=RO4N_V4Azvc

His energy stored math is wrong on two fronts.  1) Battery voltage does not stay at 6V as the battery is discharged, especially if discharging at a higher rate.   2) You don't get 232 ah at 80% depth of discharge.  You get 80% of 232 = 185Ah.  Big difference.

You'd need 5.2/450 = 11.5 golf cart batteries to get 5.2KWh of usable storage.  They'd last for 750 cycles, versus 2-3,000.