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Two years ago, I began a project to upgrade our TC batteries from AGM’s to LFP’s. Our complete TC DC system upgrade includes 320 W STC of PV on the roof, a Victron MPPT charge controller, a Victron DC-DC charger, a Victron Smart Shunt, and the 2x 100 Ah Battle Born LFP batteries.

I’ve been very happy with the specs and performance of the 2x 100 Ah Battle Born LFP’s, but I’ve occasionally wondered if their performance lives up to the hype and meets the specs. Over the past ~30 days, I’ve been slowly discharging the batteries in the TC with an ~3.5 W load. They hit the 200 Ah discharge target yesterday, so mission accomplished.

However, although programmed for 200 Ah of battery capacity, the Smart Shunt indicated there was still 17% of capacity left, and the 12.70 V voltage display also suggested ~17% remaining capacity.  These values suggest the low-load capacity of the batteries is 200 Ah / 83% = 241 Ah.

The discrepancy is explained by a battery behavior phenomenon known as the Peukert Effect, and the smart Shunt is smart enough to factor this into its SoC calculation. In this example, the battery capacity is higher than rated due to the very low load. I used the battery specs and data below to calculate the Peukert Exponent for this example to be 1.04 — very close to the 1.05 value I have programmed into my Smart Shunt. 😎

So, these two batteries weigh about 64 lbs. together and can deliver 200 Ah. It would take three or four Group 27 AGM batteries (~190 — ~250 lbs.) to match this performance.

All in all, I’m quite pleased with these batteries!

Safe travels,    
Jim / crewzer

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We just watched 2 hrs of sat Tv with lights on. 2 cheap group 27 5 yrs old flooded batteries and the control still says 12.6 . In the morning with the furnace set at 58 degrees it will say 12.5 then the sun will be up and in a few hours fully charged. I have to wonder why spend lots of money on lithium when the old technology works so good

@Gary posted:

We just watched 2 hrs of sat Tv with lights on. 2 cheap group 27 5 yrs old flooded batteries and the control still says 12.6 . In the morning with the furnace set at 58 degrees it will say 12.5 then the sun will be up and in a few hours fully charged. I have to wonder why spend lots of money on lithium when the old technology works so good

Because lithium batteries are 1/3 the weight, recharge 2-3x faster, last more than 3000 nights off the grid, and will not degrade in life if not fully recharged due to a cloudy short, winter day.  Besides, the inner nerd in me enjoys new technology. 

I camp off the grid 50+ nights a year mostly in AZ in winter.  A set of flooded lead acid batteries lasted less than 3 years.  These days, an equivalent lithium battery is not that much more expensive than flooded lead acid, and will last my lifetime.  YMMV

@Gary posted:

We just watched 2 hrs of sat Tv with lights on. 2 cheap group 27 5 yrs old flooded batteries and the control still says 12.6 . In the morning with the furnace set at 58 degrees it will say 12.5 then the sun will be up and in a few hours fully charged. I have to wonder why spend lots of money on lithium when the old technology works so good

Somehow I don’t think your two cheap Group 27 batteries would fit into my chosen dry camping lifestyle.  And I couldn’t get 5 years out of my last set of AGM batteries - At 3 years they were not holding a charge as well as they had when new - I don’t think they would have lasted another year.  The lithium batteries that replaced them were in their third year when I traded the 1685 in and the batteries were holding a charge as well then as they did when new.

This new trailer uses a little more power than my old one did.  I’ve been dry camping for 10 days and have used around 75-85Ah each night (one night was 116Ah - forgot to turn off the inverter when I went to bed).

So for me, your old technology doesn’t work so good.

@Gary posted:

We just watched 2 hrs of sat Tv with lights on. 2 cheap group 27 5 yrs old flooded batteries and the control still says 12.6 . In the morning with the furnace set at 58 degrees it will say 12.5 then the sun will be up and in a few hours fully charged. I have to wonder why spend lots of money on lithium when the old technology works so good

@TJeeper posted:

Because lithium batteries are 1/3 the weight, recharge 2-3x faster, last more than 3000 nights off the grid, and will not degrade in life if not fully recharged due to a cloudy short, winter day.  Besides, the inner nerd in me enjoys new technology. 

I camp off the grid 50+ nights a year mostly in AZ in winter.  A set of flooded lead acid batteries lasted less than 3 years.  These days, an equivalent lithium battery is not that much more expensive than flooded lead acid, and will last my lifetime.  YMMV

We're fortunate we have choices. I geek out on stuff too, like Keven. There are several other bullet points to consider in addition to Kevin's when comparing the cost of Li vs FLA chemistries and the camping advantages they offer.

  • Adding to his 3000 nights off grid is the advantageous lower cost of Li. Because of their longevity the overall cost is lower than FLA.
    • Drawdown: 50% SOC is recommended with FLA for max life and it seems with 5 yrs on yours, you don't exceed that too often.
      • Li can be fully drawn down (even below 32°) with out effecting the 3000 cycles Kevin notes.
  • Winter temperatures effects both battery chemistries when it comes to SOC cycling. FLA's charging rate will slow way down during its absorption stage.  On the other side, Li is limited to recharging above 32°

Just putting the above out there on Jim's @Crewzer's thread. Choices are made based on individual priorities.

Point: I found something similar to Jim's experiment by using inverted DC power to my fridge for the test. My goal wasn't the Pk value but rather to set the accurate zero point to calibrate my battery bank to the 702 Smart BMV. My final voltage was lower, 11.1 as I recall, yielding a total draw down of 368Ah from the rated 340Ah bank. That's about 8% more than the rated 340. The specs on the Dometic 702 in my TT states 2.7A ~AC equating to ~ 25Ah DC before inverter losses.

@Gary posted:

We just watched 2 hrs of sat Tv with lights on. 2 cheap group 27 5 yrs old flooded batteries and the control still says 12.6 . In the morning with the furnace set at 58 degrees it will say 12.5 then the sun will be up and in a few hours fully charged. I have to wonder why spend lots of money on lithium when the old technology works so good

I support Gary's position that for his needs, lead acid is just fine.   If you stand back and look at his point, most that argue for lithiums are making an apples-to-oranges comparison.   

Gary probably doesn't spend the equivalent of two months off grid per season or the equivalent of a year in his camper by treating it like a home.   Therefore, it's a rather unfair argument that somehow his technology is a poor choice.   Like he, we're occasional recreational users, and have never suffered zero power after a couple of days of use because of our camping style when we powered with lead-acid.   

Yes, we have lithiums in our camper, but it was not a choice due to them lasting the next 60 years at 50 cycles a year, charging faster, etc.  It was more out of curiosity to learn something about the new technology than anything that drove the decision to install lithiums and not 'need' as the sales pitch ALWAYS sounds like.   

Last edited by Doug, aka Atchafalaya Man

I agree with Doug above, ever since the dawn of LFP's  it's been an option to fit YOUR camping style. Lead acid won't support Harriets load requirements and they have allowed ours to grow into alotta inverter comfort use. I was happy to shed lead but for some it still works. I was initially real happy to sleep in a real bed, have hot water and a fridge. Now flip a switch for coffee, warm a sausage egg biscuit in the microwave and run the AC for lunch all on battery and sun power. What's next? a fuel cell and hydrogen power? 

@satek60 posted:

I agree with Doug above, ever since the dawn of LFP's  it's been an option to fit YOUR camping style. Lead acid won't support Harriets load requirements and they have allowed ours to grow into alotta inverter comfort use. I was happy to shed lead but for some it still works. I was initially real happy to sleep in a real bed, have hot water and a fridge. Now flip a switch for coffee, warm a sausage egg biscuit in the microwave and run the AC for lunch all on battery and sun power. What's next? a fuel cell and hydrogen power? 

Totally agree, right now I get by quite comfortably with two LA batteries, 200w of portable solar and a generator for a backup. A week of dry camping is not a problem for me. My needs may change in the future, but for now I don’t feel the need to upgrade.

We got by on deep cycle LA batteries for many, many years. However, as our needs / wants / demands for more comfort, more activity, and more gizmos have increased to satisfy our growing interest in boondocking / dry camping, our requirement to generate and store more useable electrical energy has also grown.

We now carry two e-bikes, and a 48 qt electric cooler to supplement our three-way fridge. Our solar panels, DC-DC charger and 2x 100 Ah LFP batteries meet our energy needs for these gizmos (plus our iPads, phones and watches) as well as the “usual” camper loads (fans, lights, etc.).

Our portable power station powers our microwave and provides backup for the main batteries. We don’t carry a generator, and we might start carrying a DC electric blanket.

LFP batteries have allowed us to boondock / dry camp more comfortably and for longer periods, and have also reduced our payload by ~200 lbs. This new technology works for us.

Safe travels,    
Jim / crewzer

Since I went with lithium house batteries, a portable power station, and solar charging, I have been discovering options to do things differently……., for example, when boondocking or dry camping I appreciate being able to reduce dependence on propane for cooking or other things. I no longer need to run the propane generator if I need 120vac for most things. Although I use the microwave for the majority of my hot meals, I’m currently thinking seriously about buying an induction cooktop. I also use 120vac to power an electric coffee maker, toaster, crock pot, space heater, hair dryer, vacuum cleaner, and eBike battery charger.

@Nutman posted:

Since I went with lithium house batteries, a portable power station, and solar charging, I have been discovering options to do things differently……., for example, when boondocking or dry camping I appreciate being able to reduce dependence on propane for cooking or other things. I no longer need to run the propane generator if I need 120vac for most things. Although I use the microwave for the majority of my hot meals, I’m currently thinking seriously about buying an induction cooktop. I also use 120vac to power an electric coffee maker, toaster, crock pot, space heater, hair dryer, vacuum cleaner, and eBike battery charger.

Hair dryer?

@Nutman posted:

Since I went with lithium house batteries, a portable power station, and solar charging, I have been discovering options to do things differently……., for example, when boondocking or dry camping I appreciate being able to reduce dependence on propane for cooking or other things. I no longer need to run the propane generator if I need 120vac for most things. Although I use the microwave for the majority of my hot meals, I’m currently thinking seriously about buying an induction cooktop. I also use 120vac to power an electric coffee maker, toaster, crock pot, space heater, hair dryer, vacuum cleaner, and eBike battery charger.

We too have a coffee maker, toaster hair dryer and vacuum cleaner; we don't usually carry a crock pot or instant pot but sometimes if the outing requires it we do. And of course I have fast charger for my Dewalt tools I carry. We use the microwave a lot too.

We enjoy camping a lot, but a 72 years old we no longer relish roughing it but doing things the easy way.

@R&V Spiker posted:

Hair dryer?

@Chuck3006 posted:

Oft times having a wife means having a hair dryer. The redhead I married 53 years ago has turned into a platinum blond and she wears it long, so she keeps one in the trailer. you know, happy wife and all that.......

That was intended as a funny. Larry has no wife, girlfriend and what hair he has is always under a hat.

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