Massive Electric Bucket: What is an electric bucket? An “electric bucket” is my description of our RV battery remodel. (I will explain later) How did the RV battery remodel work? This post describes the real testing results while camping off-grid with our new RV battery remodel. How much energy did we consume? Did we achieve our design goal? Real questions and real answers based on living with our new RV battery system.
Originally published June 2020. Updated April 27, 2024
Note: We paid for our electric bucket (battery remodel) but did receive some discounts and one free item to evaluate. This remodel is not sponsored by any company. This is also one of the steps in our electrical/solar conversion. We will include a massive solar panel system to recharge our new Massive Electric Bucket.
This post describes the test results of our Hybrid Mongrel Battery post and is intended to explain how each part of the Hybrid Mongrel Battery works.
Massive Electric Bucket
What is a Massive Electric Bucket? This is my description of how our new RV battery system works. As you can see from the pictures, we invested a big battery power investment.
Hybrid Mongrel Battery
Our new battery (electric bucket) includes the 600 amp-hours of AGM (lead-acid batteries) that came with our RV and nine lithium-iron phosphate batteries. The useable energy in the two combined systems is 300 amp hours of lead-acid battery storage — coupled with about 945 amp-hours of lithium storage.
The 600 amp hours of lead-acid batteries can only provide 300 amp-hours of energy storage to prevent their early death. The way the system is wired, the AGM batteries are only asked to run the lights.
The heart of our electric bucket is our lithium battery bank, which feeds our AC electrical system. The biggest user of AC power is our residential refrigerator, the biggest fridge I have ever seen in an RV and consumes lots of electricity.
When the residential refrigerator was installed in 2008 (when the RV was built), no one ever thought that our RV could operate for more than a few hours without outside electrical hookups. We just spent a week with our new batteries as the only electricity and used the generator to recharge the batteries while we were camping off-grid.
Recharging
This week, we discovered that the solar panels (also installed in 2008) are not functional. Although this was a disappointing discovery, it did make measuring the energy input into the batteries easier. However, we don’t have real totals on how much energy we put into the RV battery system over the last week. We were living, not just conducting tests.
I gathered lots of data on how much electricity we used. There are limitations on the money spent on buying measuring tools. I could only record some of the discharging and recharging – most of the data – not all.
For the last week, we ran our generator five times for about 12 hours. This produced a minimum of 1488 amp-hours of energy into our batteries. Our recharge rate was a constant 125 amps per hour into the battery. I say the recharge was a minimum number because while the generator was running, I also put an additional 72 amp hours directly into the AGM batteries.
To make things more confusing, I also used the lithium batteries to recharge the AGM batteries during the week. I figured I transferred about 300 amp-hours from the lithium to the AGM during the last four days, keeping the AGMs close to a full charge all week. I also recharged the engine battery by transferring energy from the lithium to the engine battery.
Monitoring
Because I did not spend money to buy more equipment to monitor the output, I did not measure the energy flow out of the AGM batteries. I monitored the energy flow out of the lithium batteries, which consumed 2355 amp hours over the week. On average, we used at least 336 amp-hours of energy every day. (this is more than two times the electricity versus our previous RV)
How do we monitor the energy input into our electric bucket? This link will describe what I think is the best part of our battery remodel. Battery Monitor
Wait a minute, the math doesn’t work! I used 2355 amp hours but only recharged 1488 amp-hours. What gives? The answer is that I departed with the lithium batteries needing 867 amp-hours of energy that we did not replace until our next campground.
How did I use 336 amp-hours of electricity a day?
Refrigerator and occasionally the water heater, microwave, and hairdryer. We even used the electric convection oven on the last day. We also used two computers and two TVs every day. No, we weren’t holding back. Prior to our week of off-grid camping, I was using an electric space heater — just for testing. At one point during the testing, I maxed out the capacity of our inverter, a trick I promise not to repeat.
So why do I call it a Massive Electric Bucket?
So why do I call it a Massive Electric Bucket? Because like a bucket and water, I can pour electricity into my lithium batteries as fast as I can – just like pouring water into a bucket. If I can make 200 or even 500 amp-hours of electricity per hour, I can pour it into the lithium batteries without hesitation. (For our system, the limit is how much per hour the other components will tolerate. The batteries could handle much more than the other parts of the system.)
A lead-acid battery is not a bucket.
All lead-acid batteries resist being recharged, and the closer they are to full, the more they resist until finally—hours later—they are full. Then, after lead-acid batteries are full, they begin to leak, needing a little trickle of electricity to keep them full. (Unlike lead-acid batteries, lithium does not leak and thus does not need the trickle to keep them charged.) Our Massive Electric Bucket doesn’t leak.
Drop-in-replacement
If anyone cares to know, these batteries are easy to swap out for their current lead-acid batteries.
The batteries I installed are the standard drop-in replacement batteries many RVers use to swap their lead-acid batteries with much better lithium batteries. Of course, it is hard to call them replacement batteries because I didn’t replace my lead-acid batteries. Even more importantly, my lithium battery bank holds about six times the electricity than the batteries that came with my RV.
It is laughable that when the RV battery system was created, the battery was so small and the refrigerator was so large. I didn’t make any changes to my battery charging with the exception of controlling the charge to meet the needs of the lithium. Again you can review the changes in my post about my Hybrid Mongrel Battery and in the solar section of the blog titled RV Solar, part three, batteries — everything you need to know.
Design Goal
Can we live normally for at least two days, starting with a full battery, without adding electricity?
Yes. We collected 28 data points and went for 64 hours before our first recharge. I could have gone 72 hours before the first recharge, but we wanted to run the generator to run the air conditioner, which creates a recharge.
Can I run the air conditioner from the battery? Not yet, but yes, in the near future.
Do the lithium batteries hold (and are willing to give up) all the energy they are advertised to have?
Yes, we pulled our 867 amps battery out of the 945 amp hour battery before recharging. This means we pulled 85-90% out of the battery, and they were still in the happy range. The battery was 12.67 volts for voltage questions and only had 10-15% remaining charge. Do this once with lead-acid; the battery will need replacing sometime next year.
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Links
Battle Born BB10012 Lithium Iron Phosphate Batteries (8) = 105 amp. This is the heart of our electric bucket.
(Lithium iron phosphate batteries are measured at 105 amps; when new, they will degrade slightly in performance with use. After ten years, they are expected to lose only about 20% of their capacity.)
4/0 Battery Cables (I made our cables)
Lifeline AGM batteries = 600 amps (when new, 300 useable at 50% discharge, came with the RV
Magnum 2810 Inverter Converter (charger measured at 125 amps per hour) came with the RV
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Very clean cable work.
Cost for the Lithium Batteries?
Current prices are in the links for the components. Lower prices can be found typically on black Friday or secondary sellers. I outlined the price per watt of usable energy on March 19, 2019 post titled RV Solar Series: Batteries Lead or Lithium https://foxrvtravel.com/rv-solar-series-batteries-lead-or-lithium/
I thought you would damage a lithium battery by charging too fast. Do you really think that you can put 200 amps per hour without damage?
If you have a 100 amp lithium battery, you will not want to charge the battery at 200 amps-per-hour. This will cause excess heat during the recharge and make the life span shorter.
Best practice would be to slowly recharge a 100 amp-hour battery at perhaps 50 amps-per-hour and that would help increase the lifespan.
Since I have installed more than 900 amp-hours of batteries, I can recharge at a much higher rate than 200 amps-per-hour with no damage to the battery… but my fuse won’t allow more than 300 amps-per-hour and this protects other components in the system.
The batteries indeed are being recharged slowly even at 200 amps-per-hour.
I recently installed 3 LifeBlue 12300LT LiFePo4 batteries, rated at 300 AH each. These can be charged at 150 amps, EACH, for a total maximum of 450 amps for my 3-battery configuration.
Charging FoxRVTravel’s 8-battery configuration, rated 840 AH would probably allow a very similar 400+ amperage!
By adding an RS3000 inverter /charger with an additional 175 amp charging capacity to my existing MS2812’s 125 amp charging capacity, for a total of 300 amps charging capacity, I’m still nowhere close to the 450 amps limit for my 900 AH battery ‘bucket’!
FYI, now when running my generator, with 2 chargers operating at 300 amps total, my lithium batteries will fully charge in about 60% LESS time! I can only imagine what having ANOTHER 150 amps of charger capacity would do to shorten my generator run-time by an additional 20% or so!
Don’t forget that the lower the charge rate the less “stress” you put on the battery. Just because you could charge it fast, it doesn’t mean that you have to charge it fast.
Will fast recharging take life off your battery? Yes
Can you tell how much life is reduced, without side-by-side testing? No
How long will these batteries last?
Greg,
These batteries have warranties of ten years — or more. At the ten year mark, they should still hold about 80% of their rated capacity.
Life depends on discharge-recharge cycles which will exceed 3000 full discharges, possibly 5000 full discharges and recharges.
I expect that I will never have to buy batteries again in my lifetime…. for as long as I can RV. If I change RVs, my plan is to take them with me. Even after using them for the next ten years, they should have some good value.
Remarkable, Scott. Your deep knowledge and comfort with the challenge must also come from your days running a solar company?
What is AGM?
Absorbent glass mat. A type of lead-acid battery that doesn’t vent or need maintenance. It is the best lead-acid.
So are you still convinced that you will be keeping the lead-acid batteries?
No, after I put the solar on, I may disconnect the AGM batteries. They just take too long to recharge.
If I put two hours of generator time into the lithium I get about 250 amps into the battery. To do the same thing with the AGM batteries it would take about 8 hours.
My goal for the solar is to put about 600 amps into the batteries over the course of one day of full sun with the panels correctly orientated, even in the winter. Perhaps I will cut the solar size, but I don’t think so. Since I am anticipating using about 400 amp-hours of energy per day in the winter I will be able to put in 1.5 times the energy I take out. My design should bridge two maybe three cloudy days and then be able to recharge nearly all the discharge in one day.
If I don’t get the sunshine necessary on the third day, I still have the generator.
I don’t think I will need the extra capacity or weight of the lead-acid batteries.
Looking at your graph, I noticed that you did not recharge the batteries each day. I thought you had to bring batteries back to full after every discharge.
If you have lead-acid batteries, the longer you leave them discharged, the shorter the life span. So the recommendation is to fully recharge.
This does not apply to lithium, in fact lithium loves to be somewhere in the middle. Not fully charged, not fully discharged. Not fully charging actually increases the life span slightly.
It is important to fully charge lithium for the purpose of balancing the cells but you don’t have to do it each time you discharge.
When we install the solar, I expect to see a full recharge more frequently, but for generator only, not charging fully is not a problem.
Just curious about the mixture of BB and Lion batteries in the same bank…..were you just experimenting??
I have 8 of the Lions in my Battery Bank and they’ve been rock solid with our 1600W of solar 😉
Paul, I just added the Lion UT1300 into the bank in parallel. You can get to me offline to find out why I made the mix. So far I haven’t noticed any functional difference but the Lion UT1300 requires a little different wiring.
Keep up the good work! I use my LiFePo4 packs in a variety of different applications and situations so I have me lots of opportunities for testing and observing.
I still think the #1 game-changer that I didn’t expect when switching to LiFeP04 was how quickly they recharge from whatever source you might have available.
I recently did a project where I took a solar-powered kayak challenge. I built a mount for my Kayak and put a trolling motor on it and ran it from several U1-12RT Valence LiFePo4 40ah batteries (charged by solar). I navigated the 17 miles around Lake Pactola and it worked way better than expected.
Fun project and it kept me moving as fast as two people continuously paddling!
Hey Scott, you never told me you used to run a solar company? I thought you were a Naval Aviator. I must be getting mixed up.. 🙂
I installed my first solar (thermal) collector in 1979 while in college. Then ran the company until I was accepted into the flight program. So yes, both.
Hey Scott- I haven’t seen anything posted yet on how many watts of solar panels you are planning on installing on your roof. Are you going to make them all tillable to increase your gains in the winter? I have lots of data on my 1280 watts of flat roof panels and my 400 watts of auxiliary tilted panels (for use during the low sun elevation months of November -Feburary) if any of that would be of any use to you.
-Scott H.
Scott, solar is so close I can almost taste it. But today we are sitting in Las Vegas in full sun and roasting in the heat. No way I am going on the roof in Vegas.
To answer your question, I am shooting for at least 1800 watts, depending on the panel size. All slightly tilted, but all with the ability to tilt up to 60 degrees so that none of them will be shaded, even a little bit.
This configuration will probably be six panels on each controller, (twelve total panels) series/parallel running about 75 volts down the wire to each controller. If this isn’t sufficient, I will add another controller and six more panels.
Scott
Eҳcellent post. I was checking tһis blog and I’m impressed!
Extremely useful info ρarticularly the last part.
Thank you and good luck.
Hello Scott! I have been following your blog for some time now. I also did not realize you have previous solar design experience.
Although I have been adding/experimenting with solar on my RVs since 2001, I still am looking for the “optimum” wiring design. I have 1750 watts of solar with my current configuration wired as 2 completely separate systems using 2 Morningstar MPPT 60s with the panels ALL wired in parallel, using 8 gauge and then wired to the controller & on to batteries, using all 2 gauge.
I have been experimenting with changing the panel wiring to various series-parallel configurations to determine the ‘best” solution based on shading concerns. I can’t say with real certainty which ‘really’ works best as I experiment while RVing in different locations. For now, I’m leaving it as an all-parallel configuration.
I would really appreciate any comments or suggestions
Felix, assuming your wire size choices are not resulting in serious voltage drop then parallel wiring is the best configuration.
You will always have a voltage drop with distance and if it is unacceptable then you will lose efficiency due to resistance in the wire. Most installers try to achieve a less than 3% drop. Because my voltage is high, my amperage is low and my drop is less than 1%.
Since your system is already running you can measure the drop and determine if you need to make any changes.