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ICC
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# Posted: 5 Oct 2024 15:54
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I don't want a lithium starting battery in a vehicle. I had a lithium in a trials bike for the weight savings. In cold weather the key was to turn on the headlight for a few minutes to cause the battery to warm from the discharge. Then it would crank the engine and start easy.
I don't know if a builtin heater would do any good. The heaters in any of the LFP I am familiar with work off the incoming charge current. The BMS turns the heater on-off as needed. But I have never looked deeply into the lithium heater thing as mostly I don't need them. So maybe some self heat? No idea.
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paulz
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# Posted: 6 Oct 2024 14:09 - Edited by: paulz
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Quoting: gcrank1 He runs an inverter off the starting bat which charges off the engine alt) to his LFP charger to keep the trolling bat charged up. He has been running this system all this year with great satisfaction
That sounds good. As mentioned in another thread, I think they make something similar for RVs, as some have switched their fla ‘house’ bats to LFPs.
Before I went to an in cabin bank and more solar, I used to take my then two LFPs back and forth for grid charging. Wouldn’t mind doing something like that again for winter; mount 2 LFPs in the truck that will charge while driving, and jumpers to connect to the cabin bank if needed. Might save some generator run time/fuel hauling and sound.
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gcrank1
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# Posted: 6 Oct 2024 15:05
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I usually have a mid-sized LA or the swap out LFP in the car, especially when I know the cabin bat is getting low; neither charges in the car; except for the old, tired SLA jump start pack on the acc 12v cig-plug in the rear. It has been handy for the old little 12v compressor for mostly tires though it could run our cabin led lights of a night.
As close as you are to home maybe only one 'back-up' in transit? (don't make too much work for yourself  )
Ive read that the LFP specific 12v to 12v chargers take the load off the alt (about $100?) but I don't know. I think they keep the alt from high amps into the low resistance LFP bat?
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ICC
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# Posted: 6 Oct 2024 18:13
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DC to DC chargers have an output limit, limited by their design. Some can be programmed for maximum current to safeguard the vehicle alternator. Maybe 18 amps, maybe 30, maybe more. If designed for charging LFP they also boost the voltage so the LFP could actually reach a 100% full charge. (The vehicle system voltage is not high enough to get LFP truly full.)
The LFP internal resistance is very low compared to lead-acid. If the connected LFP battery is discharged enough the vehicle alternator will be pushing out high current for an extended time. The alternator runs hot and dies.
I had a special Balmar alternator installed in my bus when I swapped to LFP house batteries. Capable of 170 amp continuous output it also had a temperature sensor and current limiting. $1200 several years ago.
My present van camper has tthe hd factory alt option and a 50 amp limited Victron DC-DC that works very well with the vehicle alt. $300 but I don't need to bother with carrying a generator, plus have rooftop solar.
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paulz
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# Posted: 6 Oct 2024 22:22
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I saw that Victron car charger that looks like it does both bat types. Still at the cabin escaping the unusual heat wave going on another day. Did a couple things, first I moved the Meanwells charger the gen uses and it’s loudish fan from inside next to the bank (and bed) to outside, no noise except for the outside gen of course.
While I had the 500AH bank disconnected, I jumpered in this 25AH spare Li battery I have just sitting around for a test run, in case one day I’m stuck with that for whatever reason. It did pretty well, ran the TV and fridge for about an hour and still at 13v afterward, though it did go down to about 12.7 when the fridge ran.
I missed a new in box LiTime 100AH on the local Craigslist for a hundred, darn, but watching my new Prime account for something..
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gcrank1
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# Posted: 6 Oct 2024 23:13
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That 25ah will run a lot longer if you don't run the fridge or other high draw devices off it. A fridge will stay cold for quite a few hours if you keep it closed.
It will do as much and more than my Ecoflow River 2 in terms of battery, just without the internal charger, inverter and various receptacles.
Will it fit in a plastic ammo can (Harbor Freight cheap)?
If so add some 'ports and posts', etc to make it an easy hook up. Lots of info online of such.
Be sure to fuse it!
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paulz
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# Posted: 7 Oct 2024 12:05 - Edited by: paulz
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Yes the fridge is a definite drain on off grid living. Mine is on the low draw side of things with its small size and compressor design. This week was a rough one too with 90 degree temps, unheard of at my coastal location. Fortunately winter is different. About a year ago I moved the fridge outside the front door, where temps are closer to the settings, doesn’t have to run often. A bonus for the weakened winter solar bank.
Ive followed the LP fridge threads brought up here, a possibility…
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paulz
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# Posted: 19 Oct 2024 12:06
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I get the flexibility part but why would 2 100ah batteries give more power?
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ICC
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# Posted: 19 Oct 2024 13:22 - Edited by: ICC
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Depends. Depends on the battery and how one defines more power.
More instantaneous power? If I use SOK, for an example, they have 12 V 100 AH and 12V 206 AH batteries. Both have a max recommended continuous discharge rate of 100 amps. If we connect 2 of the 100 AH batteries in parallel we would have the equivalent in total capacity of a 12 V 200 AH battery. But we could theoretically draw up to 100 amps from each of the batteries at one time for 200 amps total. The single 12 V 206 AH battery could only supply 100 amps.
However the two 12 V 100 AH contain basically the same watt-hours of total energy as one 12 V 206 AH battery. (OK, the 206AH battery has a slight advantage of 6 AH)
If you have a bigger inverter and need the greater amp draw, 2 parallel batteries make sense. For smaller maximum loads a single battery is simpler. If redundancy enters into your thinking that changes things. And if you search you might find batteries with different discharge rates that could work better for person A but not person B.
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Steve_S
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# Posted: 19 Oct 2024 21:33
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OOoppppssss a Math Error snuck in !
@PaulZ I believe that is likely more of a reference to Wh as opposed to deliverable Amps.
12V/100AH = 1280Wh/1.2kWh.
12V/200AH = 2560Wh/2.5kWh
A 100AH Battery (with 100AH cells) can ONLY deliver 100A continuous discharge & accept 50A Charge.
A 200AH with 200AH cells can deliver 200A Contiuous & take 100A Charge.
-* BMS limitations excluded. Most BMS' will allow for some limited (a few seconds) of Burst Discharge sometimes that is a factor of 1.5 or 2.0 X the default continuous output. Again, dependent on the BMS used.
2x 100AH Standard Battery Packs can output 200A continuous collectively & take 100A Charge collectively as well. Their Collective Surge handling is also improved (helps with motor starts like a well pump/AC/Freezer etc).
NB: Surge Handling by a BMS is generally capped @ 1.5X normal Rating for 5 Seconds only. Some stretch that capability a bit or do other things to allow for large surge handling.
The BONUS of 2 Battey Packs is that if one shuts down for any reason the other keeps going (unless they are both at Low Volt Cutoff).
More packs in Parallel divides both the Load & Charge by the number of packs. It is also far gentler on the individual packs which increases lifecycles considerably.
The GOTCHA !
Many companies are flogging Low Cost 12V/24V-100AH Battery Packs BUT they use 50AH cells in parallel because 50AH cells are cheaper than Snail Boogers now and very cost effective. This also effectively handicaps the pack because they are 50AH cells (regardless of being in parallel with another).
As most of you know, I am now running with 7x280AH Packs which can deliver 1400A Standard as I use 200A BMS'. Even if my Inverter pulls 250A (that's my cap) Each pack contributes 35.7A to deliver that total of 250A draw. Now the Shocking Part... The BMS' I use along with the cells I use can surge handle 2800A without as much as a blink.
An FYI: LFP can do a Short Dump - Meaning 100% Power Dump without a BMS to control it of 5C to 8C depending on Variant. a 100AH Cell can actually short dump 500-800A in Full BURST which would heat it up fast & cause internal shorts (very very bad).
Fridge: I use an Energy Star rated Danby/Magic Chef which is tagged for 220kWh per year. Start Surge (2 seconds) is 11A from my 24V system, Running uses only 4A from the 24V bank. This is what is seen at the Battery Bank (not the AC side of the fence). I can watch both the DC & AC sides and know exactly what is happening real time.
Hope it helps and adds some perspective.
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paulz
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# Posted: 20 Oct 2024 14:32
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Thanks guys. I’m still confused by all the specs and numbers but it does sound like the 100s are a better bet, provided you get the 100ah cells not the 50s. I’m still planning, hoping my old bank makes it through winter but have been doing a bit of bottom feeder market watching, however sounds like those probably have the 50 cells.
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Steve_S
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# Posted: 20 Oct 2024 14:54
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There are of course assorted Vids on YT with teardowns and many are actually eye opening (ones to avoid) but there are also many that standout as excellent quality products that we well assembled using top notch parts.
One company that sells 100AH Packs actually uses 105AH Cells to ensure the customer really gets 100AH for the long run lifespan, and the cost difference between 100 & 105 cells is literally pennies at wholesale.
Thing is, Battery Cell Duties (NON-EV) go up by 25% by the beginning of 2026 (pending on state of Gov in USA).
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paulz
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# Posted: 21 Oct 2024 14:10
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Wow, up 25% tax next year?
I wouldn’t know who or what to believe on YT. That’s why we have you.
I see prices heading down towards 100 bucks on Amazon, maybe the holiday season.. But those would be the low quality ones I’m sure. The name brands I see mentioned here, SOK, LiTime, are still much higher..
I’m at the grid for a few days of medical this week, cabin powered off so should get some good solar charging, should read 13.4 or 5 when I return, which quickly drops tp 13.2 when power goes back on. That will drop to 13.0 with overnight draw of 5 amps or so (4 140 amp batts). I did run the generator last week, mainly for testing or running the washer, puts in 80 amps.
Anyway thanks again, glad you’re still here watching. Hope you and your daughters are doing well.
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Steve_S
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# Posted: 21 Oct 2024 14:49
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That is what Biden put in place, of course that "could" change if the Orange Grifter and the Ketamine Junky have anything to do with it. Let us hope that Sanity Prevails !
Unfortunately, I never really recovered from the Necrotic Pneumonia and my physical capacity has really taken a beating. Things are just getting worse & faster now... lots of stuff being cleared out, given away to disposed of. We figure having to list this place mid spring for fast sale and I should have a few months to actually do something I always wanted to do, provided I can physically manage it. One Last Hurrah of a trip, is my hope.
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paulz
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# Posted: 22 Oct 2024 14:14
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Sorry to hear that Steve. Several of my friends our age are also touring the globe, not ‘last trips’ as far as I know, just an old man dream thing. Me, I don’t have the mental capacity for that at present, just commuting between the house and cabin once a week will have to do for now.
Along similar lines, do old lifepo4s give out similar to lead acid, just notably wear down, or is there a ‘better do something quick’ knee in the curve?
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Steve_S
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# Posted: 22 Oct 2024 16:42
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TBH I have never seen LFP's die from age or being worn out. I have seen then die from abuse though and you sure as heck haven't abused them.
Assuming we are talking about Valence batteries.
The only thing I can suggest is to charge each one up to 14.6V (3.650vpc) with low amperage after 14.2/3.550 (<5A) till they totally charge and take no amps at all. Let them settle for 2 hours & test the voltage to see where they really are at. Should be around 13.5V is nice & healthy.
Depending on your gear (sorry I don't remember) you could do a load/capacity test to see how many actual AH you have in each battery and how long it takes for them to cutoff.
If the pack is compromised and dying, the discharge will be faster and you won't have the AH, indicating it's time to replace them. If you've lost over 20%, it's time, as that will only drop faster. This is based just on standard LFP practices & info, some cell companies state 25% before rapid decline starts.
Hope it helps
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gcrank1
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# Posted: 22 Oct 2024 18:07
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Ime with LA the available AH fall off/ie, they deplete much quicker when dying; Ive taken a few to where the voltage read good but they only could take an easy load for < 1 hr. I sure got my nickel out of those, lol.
Thus far Ive heard/read of no-one getting to anywhere near that 'end of life' with LFP. My reason tells me that since we aren't supposed to take LA to 50% anyway (when good) that we have LOTs of use left in LFP to get anywhere close to that in performance.
I suspect that my LFPs will outlive me.
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