Have you tried a 12V deep cycle SiO2 silicon Dioxide battery?

[tacomabill]

Like this one:

Amazon.com: 12V 100Ah deep cycle SiO2 silicon Dioxide lead crystal battery w long lifespan up to 100% DoD, extreme temperature durability for solar, RV & off-grid backup. : Patio, Lawn & Garden

Amazon.com: 12V 100Ah deep cycle SiO2 silicon Dioxide lead crystal battery w long lifespan up to 100% DoD, extreme temperature durability for solar, RV & off-grid backup. : Patio, Lawn & Garden

www.amazon.com

I have read claims that they can be regularly dischaged down to 20% SOC and can be charged in extreme cold without damage. I had been researching LifePO4 but dont like the cold charging limitation. I need more Ah than my 100Ah AGM but only have room in battery box for one group 27 battery, so the ability to dischange low gives me a lot more usable Ah than my AGM.

 

[john61ct]

Just a lead battery.

Any AGM "can" be discharged below 50%, just needs replacing more frequently.

Firefly Oasis is the only one that actually does perform much better, but 100A costs $500+

 

[Rando]

With the exception of cold weather charging, the specs on these are almost identical to any other flavor of lead acid battery. They are not really comparable to lithium with regard to cycle life, energy density, recharge rate etc. There do appear to be some folks shilling these on some RV themed sited that are making some very unrealistic claims about their performance. In the end, they are just extra jellied gel-cells.

The low temperature charging 'issue' with lithium is a bit overstate and fairly easy to address if it does apply.

 

[tacomabill]

Even with a LifePO4, my fridge (IndelB/Truckfridge) has a low voltage cutoff that cannot be set lower than 11.8 volts so the deep discharge capability would not do me much good. I would have to also invest in another fridge with much lower cutoff, if such even exists. BTW, it is the fridge that is driving me to search form more available Ah since it is my only appliance. My only other option would be to tear apart the back end of the camper to make room for a larger, and maybe a second battery.

 

[bgflyguy]

If it's just power to the fridge you need, maybe something like this could help.

https://www.amazon.com/Converter-Automatic-12V-Waterproof-Transformer/dp/B07V8K6YZ6/ref=mp_s_a_1_3?dchild=1&keywords=12v+regulator&qid=1600965882&sr=8-3

 

[Rando]

The low voltage shutoff shouldn't be an issue with LiFePO4. The charged voltage is 13.2 - 13.3V and the just about dead voltage is 12.6-12.8V, so no where near your shutdown voltage. Fridges in general are much happier with the flatter discharge curve of lithium batteries.

 

[john61ct]

Even with a LifePO4, my fridge (IndelB/Truckfridge) has a low voltage cutoff that cannot be set lower than 11.8 volts so the deep discharge capability would not do me much good.

It would be stupid to allow anything to draw an LFP 4S pack down anywhere close to that.

2.99Vpc should be considered 0% SoC, even 3.05V for low current loads like a fridge.

That 11.8V LVC is to protect the fridge electronics, not your battery bank.

> tear apart the back end of the camper to make room

LFP occupies half the volume of lead.

 

[Madoxen]

As above sade Lifepo4 should not get that low, if the fridge keeps tripping off due to this i would take off the power leed from the fridge and replace with a much bigger cable, so many appliances come with power cords that are not good enough.

 

[67cj5]

"Some" AGM batteries can go down as low as 30% using as much as 70/80% of the batteries Capacity, My FLA Deep Cycle batteries can Go down to 30% meaning I can use 70% of their capacity, Although that might look impressive on paper The Problems start when it comes to putting the power back in to the Batteries,

If you are using Solar then you will need big panels and stay parked up for up to a couple of days at a time, If you are going to use a Battery Charger and a Generator then that can mean running the Genny/Charger for up to 16 hours +/- which is going to cost a heap in fuel not to mention the Noise it makes if there are other Campers near by,

A DC to DC Charger is another option but that will only work while you are On the road etc,

If you need your batteries to Charge quickly then AGM will Charge twice as fast as FLA, My Vehicle came factory fitted with an AGM Stop/Start Battery so the Alternator pumps out over 14.7-14.8v++ at Idle which works well, But when it comes to running my Fridge I bought a couple of Dometic PLB-40's because they can power the Fridge for a couple of days and they can be fully Charged in 2 to 4 Hours Via Solar or The Van/Campers Cigar Socket OR I can use the AC Supplied Charger via a Generator or Site Hook Up,

The PLB-40's are the fastest "Get out of Jail Free" setup money can buy, Although they are not cheap they have done away with me needing any fancy wiring and DC to DC chargers and they are 100% portable, So far they have performed faultlessly and If they are fully charged I can run the fridge from the Vehicles Cigar Socket which saves the PLB 40 Batteries for when I am parked up,

If you have enough panels on the roof then FLA batteries are hard to beat as are AGM batteries but if you are going to use a smallish G27 battery you need to have it hooked up to Solar "and" DC to DC charger 24/7,

Running 2 or 3 Big type 31 Batteries is not without it's problems, Yes they will run the fridge for up to 21 days +/- but getting the power back in and even with a 35A Charger "All" 3 batteries will not except more that about 16 to 18.5Ah So if you have 330Ah in total and you use 50% that's 165Ah, In theory at 18A is going to take 9.16 hours but in reality as the state of charge goes up the chargers output drops so that can take up to 18 hours +/- depending on the Quality/Brand of batteries used.

Sorry if all this worries you but getting a useable system that works is a minefield if you do not have the Battery Space and Panel Space, So to Avoid all that is why I went with the PLB-40's and the weight saving is awesome. works out like 150Lbs Vs about 20 to 25Lbs,

Hope that helps.

 

[john61ct]

Yes AGM has higher CAR than FLA but only in the early (CC/Bulk) stage.

In reality, because amps drop drastically in the later stages, going even from 50A to 400A only saves say 20min over the 7+ hour charge cycle required to get back to 100% Full.

And AGM needs to get back to that 100% (as per endAmps) as often as possible, and in a narrower profile range for longevity, compared to FLA.

Only Oasis Firefly has decent lifespan regularly going below 50%, but you need to run the capacity restore protocol regularly. And their lifespan will be much longer staying above 50% most cycles.

True all those issues go away with an LFP bank, just be aware of the cost per Ah.

Note that having a huge bank is not the problem if your charge sources are limited living off grid. You just need to make sure your consumption stays well below your available inputs.

A decent battery monitor helps with that.

A good rule of thumb is every $1 spent on conserving / reducing electricity consumption is worth $5 spent on production hardware.

The specific combination / sizing of alt+DCDC, solar and genset required will vary greatly case by case.

 

[67cj5]

Yeah Spot On there Ay,

I tested my bank of 3 FLA's and then I tested using 2 and now I am down to testing one Vs power used Vs Charging times, The 3 would have been nice to use because of the run time but I just can't get the power back in In under 6 hours, Or charging them for 3 or 4 hours over 2 days, So now I am test just one of them to see if I can run my Heater and Boot Dryer for the winter months so hopefully I can run them for a couple of days at night and then charge them after 2 or 3 day for a couple of hours.

Even running the 35A AC Workshop Charger all 3 batteries won't except more than 17.5 / 18Ah when first switched on and that number drops as time goes on,

 

[john61ct]

For a depleted lead battery, 6hrs is not enough to get to 100%

whether one unit or three makes no difference.

If you are willing to stop at say 90% and accept short lifespans, then maybe 4-5hrs in enough, and the Amps available might make a 40-50min difference.

Again, the key is stopping consumption at a point below your input Ah, just do without until you can increase the latter capacity.

 

[67cj5]

Yeah that's why I am running the fridge from the PLB's and using the FLA's only when I need to use the Dryer or the Heater that way I can keep on top of it, My lighting is all solar powered and they have a run time of well over 12 hours and I bought 8 of them so while I am using 2 the rest are enjoying the sunshine

The AGM in the Van has been messing about for a while so I changed that today, The original one started messing about when it was just over 2 years old So Now the New One is fitted I am going to Blast the old one on the charger and then try running the Repair mode on the big NOCO and see if that fixes it, It worked on my Brothers AGM which he now uses in a battery box so it has come back to life, Hopefully mine will do the same,

 

[john61ct]

That's really just a waste if timev IME best is buy top quality, care for it best you can, once signs of wear are detected, plan on replacing soon.

Really well coddled, FLA can go 12+ years cycled daily.

AGM anything over 5-6 is pushing it.

But abused even the best bank can be murdered in a short season.

 

[67cj5]

I think the Ford Dealer let the Vehicle sit without running it or charging the battery because it was 2 years old when I bought it 9 months ago and now I have had to replace the Genuine Ford battery,

Your right about the FLA's, Mine are 3 and a half years old and after 24 hours off the charger they read 13.4v +/- when I pair 2 of them they will run my ARB 47L for 48 to 50 hours before they drop to 12.8v, I have never taken them below 70%, Never had Batteries this good, I only wish the Van could Run one of them instead of the Stop Start AGM,

If I run them for a week or 2 I then Charge them up at around 12A then when they reach 14.8v I switch the Charger to a lower setting which drops the Voltage down to 13.8 and then the Voltage climbs back up to 14.4 to 14.8v then I switch it off and let them sit, The reason for running them up to 14.8v is because Battery University say 14.4 is good for normal charging but 14.8v removes any Calcium Build up caused by the slow discharge from the fridge or sitting for a while and so far it seems to work well, Once fully charged I run the NOCO's Repair mode and then let them rest before I use them again for a day or 2,

Overall I am really happy with the power they can provide.