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Again, in normal cycling I **never** go below 12V / 2.99Vpc, nor above 14V / 3.5Vpc.

With quality cells, even if capacity not perfectly matched, staying in that range and gentle House currents, things just don't get unbalanced, not for years and years.

Many banks over 8 years old, 2000+ cycles, most zero loss of capacity, many still above rated. Starting to think calendar aging will end up mattering more than #cycles.

A far cry from EV usage of course, and I don't think you'd get that going up to 14.5V or whatever the stupid vendor specs are.

Key is (besides protecting from catastrophe of course) keeping SoC low until your loads need to be fed, never just sit at high SoC. Need to unlearn lead thinking.
 

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Discussion Starter · #142 ·
Lots and lots of back and forth discussions here. That's a good thing. Makes me stop and think. :D

It may seem weird to design electrical before even having van but that will drive camper van layout and design. Electrical is almost the first thing to install in a camper conversion. I can't let furnishing layout dictate the electrical system very much. :)

Now I've added a propane tank to the mix. Yay! :p

I hate low hanging underslung "stuff" on a traditional RV, otherwise I'd be tempted to buy and not build. Ground clearance is very important to me as I venture off pavement often.

Here's just one picture from last months 8000 mile trip. It took me 2.5 hours to go 16 miles to this spot (Point Sublime, AZ).

Now, what will meet my needs the best? FLA is best value and will take-up valuable space inside van unless I cut a hole in floor and make a box. AGM I can completely mount under van sideways. AGM also have lower Ri with it's benefits.
 

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Again, in normal cycling I **never** go below 12V / 2.99Vpc, nor above 14V / 3.5Vpc.
That is fine, but you still have to pick a Balance Point. You cannot just take cells from the distributor, hook them up in series. The SOC of the cells are all over the place. You have to equalize them at some SOC initially to start. If you are not using a BMS Botom Balance is default choice, Top Balanced is the last thing you want with no BMS.

At a minimum connect them all in parallel and walk away for a day to get them Mid Balanced to the same equal SOC voltage. From there it is easy to Top or Bottom Balance. Either discharge to 2.5 volts, or charge them to 3.6 volts.

If you are not going to run a BMS, you had better Bottom Balance, or you still risk over discharge. If you were to Top Balance and not run a BMS, you have set yourself up to over discharge at least one cell, the lowest capacity cell in the string.


Balanced is a poor term. Equalized is a much better term and makes more sense and easier to understand. Example Bottom Balanced we have equal voltage and capacity, a known reference point of 0 AH capacity @ 2.5 Volts @ 0% SOC. Hook the cells in series, and every cell has the exact same capacity. Top Balanced and all you have Equalized and know is 100% SOC @ 3.6 volts. Capacity is unknown and determined by the weakest cell. You can easily over discharge a cell in systems greater than 4S. Example 49 volts is good if you assume 3 vpc on a 16S pack with LVD set to 48 volts. If you had only known 1 of those 100 AH cells you bought is only 80 AH. That poor little weak cell is siting at 2 volts and all his mates are at 2.9 to 3.1 volts or greater fooling you into thinking everything is OK. That is what happens when you Top Balance. If you Bottom Balance that cannot happen. The cell voltages equalize as they discharge. and all arrive at 2.5 volts at the same time well below your LVD set point of 48 volts.
 

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That is fine, but you still have to pick a Balance Point.
I clearly stated I top balance.

My point is bottom or top makes little difference given the conditions I cited.

None of the cells ever get near either of the shoulders.

> If you are not going to run a BMS, you had better Bottom Balance, or you still risk over discharge.

No, as I stated I have redundant LVDs, all close to 3.00Vpc.

No cell has ever hit 2.9V

If the conditions I outline are followed none of these issues are significant.

I have lots of BMS **functionality**, for example isolation from the charge bus well above freezing ambient.

Loads buss isolated at much colder.

Most BMS do not do that, for me it is critical.
 

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I clearly stated I top balance.

My bad, I missed it.


My point is bottom or top makes little difference given the conditions I cited.

That only works for 4S and 8S. Go to 16S or greater as explained in my last reply and now you are a setting duck for accidental over discharge. 48 volt LVD will not work because you can be as high as 50 volts with a dead cell on a Top Balanced pack. You eliminate the risk bottom balanced and still meets your objectives. It exceeds your objective and cost nothing. Just a change in logic.
 

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If Lipos are only used in RC vehicles, why are they found in commercial electric vehicles? If only 100 cycles, then EV's would stop working before the end of a year. Yes, Lithium Ion batteries are the most unstable, Lithium polymer being more stable, and LiFe batteries being the most stable.

Oh and C-rates for RC type batteries are typically much higher than 20C....just look it up to see how much hot air Sunking is blowing. Gotta love when people think they know everything because they did one install and are suddenly experts.

When considering the type of battery you want, make sure to look at how much charge they can take at a time. That will help determine what application you would like to use them for.


They cannot and is of no concern for scum bag spammer. LiPo is the last thing you want for a house battery or any application requiring long life as LiPo only have roughly 100 cycles in them. LiPo's are used in RC aircraft where C-Rates run 20C or greater continuous. Extremely dangerous lithium batteries notorious for catching fire.



They do have a application in EV used as Drag Racers where you can put a very small battery in, just enough for 1 or 2 runs. Some of the new ones claim 100C-Rate for 10 seconds which is all you need for a drag race. A 20 pound battery vs a 1000 pound battery.
 

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If Lipos are only used in RC vehicles, why are they found in commercial electric vehicles?
Just to be clear, "LiPo" means lithium-polymer, or battery of cells with lithium-ion technology and using a polymer electrolyte instead of a liquid electrolyte.

My understanding is that most EV battery cells do not use polymer electrolyte, but the Hyundai Soul EV does, according to Hyundai. According to one report the Hyundai battery is from SK Innovations, and is NMC chemistry.

I think that most people in these discussions assume that "LiPo" or "Li-poly" or "lithium polymer" means something specific about the chemistry, not just the use a (gelled) polymer electrolyte. Invalid assumptions cause misunderstandings. To avoid misunderstandings, what are the EIG cells which you are selling, GreenGyver? Are they the T020 pouch cells? If so, they are LTO cells; it looks like most small cells (including those used in the RC world) described as "LiPo" are probably LCO chemistry.

Yes, Lithium Ion batteries are the most unstable, Lithium polymer being more stable, and LiFe batteries being the most stable.
That makes no sense; lithium polymer cells are lithium-ion cells, and all of these are lithium-ion cell types:
  • lithium cobalt oxide (LiCoO2, a.k.a. LCO)
  • lithium iron phosphate (LiFePO4, a.k.a. LFP)
  • lithium ion manganese oxide battery (LiMn2O4, Li2MnO3, a.k.a LMO)
  • lithium nickel manganese cobalt oxide (LiNiMnCoO2, a.k.a NMC)
  • lithium nickel cobalt aluminum oxide (LiNiCoAlO2, a.k.a. NCA)
  • lithium titanate (Li4Ti5O12, a.k.a. LTO)
So "LiFe" batteries cannot be more stable than lithium-ion batteries, because "LiFe" (actually LiFePO4 or "LFP") are lithium-ion batteries.


Gotta love when people think they know everything because they did one install and are suddenly experts.
It seems highly unadvisable to judge anyone else's expertise based on your incomplete knowledge of their background. The number of installations is a poor measure of either knowledge or understanding, anyway.
 

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Just to be clear, "LiPo" means lithium-polymer, or battery of cells with lithium-ion technology and using a polymer electrolyte instead of a liquid electrolyte.

Today LiPo does not have a meaning, it is a Marketing Buzz word. You are correct in the sense in that they use a plastic or polymer electrolyte, to my knowledge no manufacture makes then because there is no application suited for them. Their Internal Resistance is so high make their Specific Power Density to low to be usable for most practical application except for maybe a clock.



In the RC World they do use the name LiPo which is really BS. Hard to nail down exactly what chemistry they use, but most from what I can tel are pouch LCO cells on steroids with a liquid electrolyte. A new new so called HV Graphene LiPo claim as much as 100C rate which again is meaningless, but me thinks those might be NMC variant because cell voltage is roughly 3.8 volts.


But all sources and the manufactures of all LiPo cells only claim 100 to 200 cycles. Personally with over 200 LiPo cells in my posession, I have never seen a LiPo make it past 100 cycles before they puff up like a balloon and can no longer deliverr high current rates and are more of a Space Heater than battery as they get extremely hot trying to use them as intended.



As far as EV manufactures and EV batteries? Well what I do know if tou go to say Panasonic, and look at say the same cell they made for Telsa Roadster, the spec sheet only claims 500 cycles. Go to LG Chem and you are not going to find many cells that even go 500 cycles, but offer no warranty.



Does make one wonder how EV manufactures can offer such long warranties on their batteries when it is not possible on paper. I know one thing, commercial EV manufactures do what I do because that is where I learned to extend Lithium battery cycle life only charge up to 90%, and cut-0ff at 10 to 20% which should get you up to around 1000 cycles, and that translates to 5 to 7 years.



LTO cells you talk about will never likely be used in a EV, they pack a punch with respect to Specific Power as they do have the highest Specific Power Density of all the Lithium batteries which is what you want in an EV. However they have very low Specific Energy equal to lead acid. LTO if they can get the price down, which I never see happening, would be excellent for Renewable Energy Storage because they have the potential to be a very long lived battery.
 

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What will meet my needs the best? (FLA, AGM or....) and (200Ah, 400Ah, 600Ah or....)
Figure it out yourself. Sorry but that is your job.

If it were me, FLA all the way because they last a lot longer and from cradle to grave cost 1/4 that of AGM. Price out both AGM and FLA at a given voltage and capacity. AGM cost roughly twice as much per Kwh of capacity, and last roughly half as long as FLA. So when replacement time comes you end up paying 400% more in the end.

This is why I said you need to justify the added expense. AGM has it place, a very special niche application place. Like where extremely high charge/discharge rates, extreme cold environments of -40 degrees and lower, unusual installation orientation, extreme mobile applications like aircraft or off-road vehicles, or where spills cannot be tolerated and would threaten life safety.

My advice is sit down and have a good heart to heart conversation with your wallet. In the end, it is your job to figure out and decide.
 

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US market, best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, around $200 per 200+AH pair from BatteriesPlus or Sam's Club.

Deka-labeled same batts also sold at Lowes.
 

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Note some go AGM for spec'd high CAR thinking will reduce run-time charging from ICE.

In fact, as with all lead, the higher CAR only applies for the first hour or two, to get to 100% Full (per endAmps, required "most cycles" for longevity) still takes 6-7 hours total.

But yes for discharge, lower resistance means lower total capacity required for short high-current loads like microwaving popcorn, and less V sag than FLA.

Odyssey PC-2150 is an excellent example for that, true Dual Use, great for winching etc but also very good deep-cycling usage longevity (for AGM) if well coddled otherwise.

But as SK points out **much** more expensive "per AH per year" than even the priciest FLA.
 

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Charge acceptance rate.

Lifeline AGM can take .85C for example.

However that will last only a few minutes as SoC rises Amps accepted falls drastically.

More real life, with the same high-CAR AGM bank, the difference between a .4C available source and a .2C one may be only 40min over 6+ hours.

Now quality FLA might accept say .25C , but that tapers as least as quickly, so might add another 40min to the slower example above.

My point is spending so much more "per AH per year" for the purpose of faster charging, is IMO hardly worth it.
 

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However all that goes away with LFP.

Charge as fast as you like, they accept it all the way up the SoC curve.

In theory even 3-4 days' usage can be refilled in an hour with a big enough ICE source.

But I keep to .2-.3C charge rates for longevity's sake.

Even lower is better if convenient, enough solar would be ideal given a big enough roof.
 

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sportcoupe since you are in planning stages is a good thing, many fail to plan or think things out and you get what you deserve. Allow me to point a few things out, and what I have learned in my career.

First thing will strike you as odd, but for now forget AMP HOURS. Jest get that out of the equation and consideration. All it will do is cause errors. Amp Hours is a end result after all the calculations have been done. It is the LAST CALCULATION. In fact it is not a calculation, just a simple Conversion.. You are not consuming Amp Hours, you are consuming Watt Hours which is the real work, energy used, and what you use to calculate everything.

So the very first step in the process is sit down, be careful what you ask for, and determine how many watt hours you need in a 24-hour day. It is pretty easy to do. If you are not sure, ask. In a nutshell find how many Watts each gadget and gizmo uses, and then multiply by the number of hours you expect to run it in a 24 hour period. Example say 50 watts x 3 hours = 150 watt hours. Add them all up and say you get 1500 Watt Hours per day.

OK Solar and RV's I am afraid to say are very challenging. They do not play well together. There are many obstacles to overcome. To determine panel wattage all data sources assume ideal conditions, and in an RV you cannot even get close. Example we are looking for Sun Hours. Depending on where you are at and time of year can vary. In general 5 Sun Hours in Summer, and 2 to 3 in Winter. That assumes absolutely no Shade Issues from sunrise to sunset, at optimum tilt/orientation angle, at moderate cool temps. That would mean parking in Full Sun with no shade in eye site. Park at the perfect angle to orient panels solar south. Then have a way to elevate the panels off the roof so they can stay reasonable cool, and provide the proper tilt angle. See any problems doing that, and be confident you got it right? Good luck with that.

But lets say you did get it right. What panel Wattage is required? That is where we need Sun Hours and Daily 24-Hour Watt Hour Usage. If you want to pay more money than necessary, use an inexpensive PWM Charge Controller. If you use a PWM Controller Panel Wattage = [Daily Watt Hours x 2] / Sun Hours. Example 4 Sun Hours and 1500 wh. 1500 x 2 / 4 = 750 watts minimum. Did you ask yourself why PWM is more expensive?

Now if you want to save money, make things efficient, less material less space required, use a quality MPPT Controller. They will cost you 5 times more than PWM. OK with a MPPT Controller Panel Wattage = [Daily WH x 1.5] / Sun Hours. So 1500 wh x 1.5 / 4 = 562 watts. 550 watt sis close enough.

As for Controller is easy. Run through the MPPT panel wattage 550 watts. Minimum MPPT Controller Amperage = Panel Wattage / Nominal Battery Voltage +1 volt per 12 volt of battery. You already know 12 volt battery + 1 volt = 13 volts. So 550 watts / 13 = 42 amps so you are looking at a 40 to 45 amp controller minimum for either PWM or MPPT. They both wil delive the same current, PWM just needs a lot more wattage than MPPT.

However that is not the only place you save a ton of cash with MPPT. If you use PWM you must, and I say MUST use very expensive low voltage 12 volt battery panels. You must also wire all the panels in Parallel. Two last things you never want to do. Low Voltage battery panels wil cost 2 to 5 time $/watt of Higher Voltage Grid Tied Panels. Being lower voltage means smaller wattage panels. 180 watts is about as big as 12 volt battery panels come in. At 750 watts means 5 x 150 watt panels wired in parallel. Once you have more than 2 parallel Strings is going to require expensive Combiner, and Fuse/Breaker assemble. After Combined you will be running 45 amps to the Controller Input which requires some heavy 6 AWG cable to figure out how to run in. Also mean racking hardware x 5. Not what you want to do and the biggest error almost all DIY's make. We call it Stuck Inside A 12 Volt Toy Box mentality. Don't do that.

Smart Money is to use much less expensive Grid Tied Panels and MPPT Controller. GT panels run at much higher voltage which means much lower current and more panel wattage up to 300 watts per panel. All you need is two or three panels all wired in series. Example use 2 x 275 watt panels = 550 watts. With the panels wired in series panel current to the Controller Input will be around 9 amps which means a single 14 AWG wire, no fuses or combiners to deal with as they serve no purpose. I use a 20-amp cartridge type at the controller Input for a Disconnect Device. Otherwise if required like PWM to be located at the source; the panels.

OK all the work is done, what size battery? Well again we need Daily Watt Hours, nominal Battery Voltage and most important number of all is HOW MANY DAY RESERVE CAPACITY. In a stationary system would be a 5-Day Minimum reserve. In real application gives you 3 to 3.5 cloudy day coverage before you run your generator. Determined over years 5 day sis the sweet spot economically getting the most bang from your buck making the batteries last as long as they can yielding maximum energy storage.

But you are not going to do that. Not required for an RV. You do not use them every day 7 x 24 x 365. RV minimum is 3 days with or without solar. That will give you two full days of run time before you need to do something. Rest is easy and as promised Amp Hours is just the end result with no mistake and taking Peukert, Charge Efficiency, wire losses , and all losses have been accounted for. So now we know daily wh, battery voltage, and reserve time. Battery AH = Daily wh x Reserve Days / Nominal Battery Voltage. So we have 1500 wh x 3 / 12 volts = 375 AH

However forget all that work. We used optimum conditions you have no way in heck to do. By the time you de-rated everything from ideal would require well over 1500 watts of panels. Two real expensive charge 60-amp controllers at 12 volts. A lot more current than FLA can take, but AGM could if money is no object.

Make it easy in an RV determine daily wh, 3--day reserve capacity. Find Capacity which is the same 375 AH battery. Accept the fact Solar is not going to be your primary power source and treat it as Supplemental Power. Use an Electronic Battery Isolator to allow engine alternator to do charging. If driving daily or every other day will be your primary power source assuming you are driving a few hours. If you add solar can add a day to that. Carry a generator and charger. Size Genny to run the loads and charge battery at max rate.

Want solar with that? Easy peazy money bags. Size panel wattage and controller to supply roughly C/10 charge current or as much as you can afford without going over C/8. No need to waste money on something that is not your primary source Panel Wattage = C/10 Current x Nominal Battery Voltage + 2-volt per 12 volt battery. 38 amps x 14 volts = 532 watts. 2 x 250 watt panels and 40 amp MPPT Controller. Even with Solar still requires a generator and/or driving if you spent that $75 on an Electronic Battery Isolator.


Last comment on the RV battery type. 3 days FLA, AGM, LFP, or ABC--123 makes no difference. All will work with above.



So go figure it out.
 

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Another approach.

If you use lead, and live long periods off grid, you must have solar.

If your roof is less than 30' long, then fill it up with panels.

Maximum watts per sq ft area, jigsaw approach different sizes if necessary, and ideally using panels rated over 40Voc.

Then match up like panels and buy Victron SmartSolar SCs rated to handle the wattage (amps), e.g. 75/15 handles 200-250W worth.

______
Now, bank sizing, you say 400AH LFP is enough, if lead that's 600-700AH or so, prolly fine for everything but the aircon.

Best to go over a bit rather than under, or if you might need more, do it before the original bank's too worn.

If you find the solar input is not enough to get you to 100% Full (per endAmps) at least a few days per week, then get an ACR / VSR hooked up to tap into your alternator while driving, and do that high-amp charging in the early AM, keep usage down, give the solar a chance.

Still not enough? Get an inverter genny and a well-matched mains charger. Same early-Bulk routine as above.

Of course, regular access to shore power trumps all other sources.

Done.
 

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Discussion Starter · #160 ·
CAR - good info there. I figured it was tied to Ri.

Low Ri is preferred. I don't want my inverter shutting down under full load after only an hour on a full charge battery pack due to voltage sag tripping inverter min voltage.

Battery type must survive washboard dirt roads for hours and off camber situations at times. This is no street-only RV.

Primary charge will be electronic relay. Mains charger to give good charge as needed. Van will be driven daily for work and off grid on vacation trips.


I took a stab at daily AmpHrs

12 V DC Appliances and Watts/Amps/Ahr
Furnace fan 48 4.0 16
Light, LED 8 0.8 4
Propane alarm 3 0.2 5
Refrigerator 36 3.0 36
TV 36 3.0 12
Water pump 48 4.0 8


120 V AC Appliances and Watts/Amps/Ahr
Aircon 410 3.4 14
Coffee Maker 800 6.7 7
Cellular phone charger 40 0.4 2
Computer, Laptop 150 1.3 4
Microwave 1000 8.3 8

Watts/Amps/AmpHrs
DC Loads: 193.58 15.0 82.3
AC Loads: 2410 20.2 34.9


Days usage per week:3.0
AmpHrs per day:117.2
AmpHrs per week:351.7
 
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