Charging system question

[JoeC]

Kayak73 and others:
I converted the fridge to 12 VDC compressor, mostly because I don't like using gas as it has failed me several times and finally some bug plugged the stack and wouldn't work at all on gas. I would have needed to pull the unit out and disassemble the stack to fix it. Instead, I had the unit converted to compressor.

I am getting the rig ready for a several month tour of Alaska. Lithium batteries, solar power on the roof, and conserving propane for cooking and heating. The weakest link now is fresh water and dumping and we've got that down pretty well. 10 days on 45 gallons of water. Hopefully, dump stations are not going to be difficult to find.

[Kayak73]

I've read of several folks converting the fridge to 12volt dc compressor. The cost varies depending on the kit but if you had issues with LP, good enough. I would love to trade my 12vdc compressor unit for any one of the LP units we owned in the past, I never had a single issue with any of them, they ran for a very long time and had little impact of the propane tank at all.


I suppose that's why there are different RVs equipped differently - so we can all talk about the relative merits/disadvantages of all these things.


I'm happy with the performance of my 12vdc compressor fridge now that I can make it run dry camping but I sure would have been happier with the old LP units. The compressor fridge holds temps great, I can store ice cream hard although I can't eat it but DW does that. Somehow she stays skinny and eats all that stuff I can't. I gain weight just watching her eat.



I don't even like to put on paper or here what the total cost of this conversion is with lithium and solar and the fridge change to compressor. But...it is not my rig and if it makes you happy - good deal. These things are just made to tinker and modify, I like that.


I always have a small grill and a backpackers stove in the rig. That keeps heat and smells outside the rig. The little backpacking stove is tiny but boils water in a heartbeat (short minutes) for the French Press and good coffee.


I know you have already bought the right book for the Alaska tour, milepost thing but you should be fine with dumps and fresh water.


Have fun!

[al1florida]

As far a cost of lithium goes, versus 6 golf cart batteries which provide 690AH capacity.
-- You can use 5 lithium batteries, with 500AH capacity,for around $5000 so the cost is a little less than $7000. However that $5K is still way more than the cost of 6 golf cart batteries for about $600 at Costco/Sam's Club. Yes I am kind of nit picking, but $2000 is not chump change.
-- Unless you have the means to spend $5000 or more, or just really want the lithium, the other considerations need to be considered. Frequency & length of dry camping, ability to get lead acid to 100% charged, weight, space requirements, ability to install batteries inside living area and probably more. Many of these have been touched on already in this topic.

[creativepart]

Actually, to compare the costs of 690AH battery bank you should compare it to purchasing four 100AH LiPo batteries. Because only 1/2 of the amps available in the 690AH bank are usable - 345AH of usable storage. Four 100AH LiPos would provide nearly a full 400AH of usable power.

Sure $220 worth of 6v batteries provide a usable 100AH of 12v of deep cycle power just like the $1,000 LiPo (that's a 5/1 cost ratio) but the comparison only takes into consideration the most basic features - AH and Voltage.

There is a benefit to batteries that have no maintenance, weigh 1/4 as much, charge faster and last longer. And any comparison of price MUST include the value of these pluses.

If a person can't afford the cost of LiPo batteries then it's a moot point. They will not buy them no matter how capable they are. If one can afford this upfront extra cost they'd be foolish to not consider them seriously.

[jcurtisis]

Originally Posted by Kayak73

jcurtisis,


Here's what the lead acid buys the OP, John Vista. Functional, operating 12volt power for his rig.


To get those amp hours in LiFeP04 costs $7000.00 cool green cash. He could save weight, the batteries last longer perhaps and they recharge faster.


Price point is 10:1 which makes it a financial decision for most folks. My take is pretty simple, all those saying we should dump that much cash into lithium might want to provide a long term low interest loan or even set up a freebie donation pool where the proponents and advocates of lithium just dump cash into the pool so us poor, unrefined, tasteless and misguided owners with FLA or AGM can become part of the elite group...


Let's see, he went FLA for 1/10th the cost. He can replace those 10 times before reaching the cost of lithium. Even if he abuses the batteries and they only last 4 years that's about 40 years of batteries in his rig - doing exactly what he needs. I don't believe any of the info about it being cheaper in the long run to buy lithium. It certainly is not today, it is simply spin by proponents.


Say you spent the $7k - can you get a replacement at Costco, Sam's, the local battery shop? How long will the company be in business who sold you the $7k setup? Say 10 years from now?


LiFeP04 is very desirable - just not practical for me yet. Maybe when at least two companies can post usage instructions and install instructions which agree. When RV techs won't hammer the system if it has to go in the shop, an unlikely thing since they usually kill even FLA. When the price point is perhaps 2:1 or even 4:1 I will consider it a viable solution.

Kayak 73
Thanks for the input, but I'm not sure what you meant by "Here's what the lead acid buys the OP, John Vista. Functional, operating 12volt power for his rig." (too cryptic for me) and I don't understand where you got the $7000 price tag you referenced. Perhaps we are talking about different applications. My goal is to double the power available from batteries for dry camping.
I am simply comparing the amount of usable amp hours for two 12V lead acid batteries rated at 100 amp hours each (comes standard in my 2018 Navion) to what one needs using Lithim Iron Phosphate (which turns out to be one 12V Lithium battery). One lithium battery is $650-$1000; the Lead-acids are about $150-$300 (but one needs two of these to equal one lithium). Lithium will last 5x - 10x the lead acid, so the quick cost of ownership (same usable Amp hours) is for Lead Acid=$150x2x5=$1500 (best; could be $6000 high end) VS lithium=$650-$1000 (depending). Plus Lithium has less weight, no venting issues, no corrosion issues and no maintenance.
SO to achieve my goal, it seems I can achieve this with two lithium 12V batteries for ($1300-$2000), use the same battery space I currently have, drop my weight by about 25 lbs, have no maintenance and no corroded terminal issues for 5-8 years. I really can't do this with Lead-acid without growing my battery "footprint" in a vented space (I don't think I can actually solve the vented space issue without exten$ive mods) and adding about 84 lbs.
I could actually (for about +6 lbs total weight and minor mods in a cargo space next to the existing battery tray) add a third lithium battery and get triple the power available. Might actually think about that.....
It seems that to achieve my goal to double my available battery power, I can do this with Lithiums and save about 25 lbs weight, pay half the cost of ownership, have zero maintenance and no expen$ive space modifications.
My remaining question relates to what if anything needs to be changed in the existing charging systems and inverter (if anything). Hopefully the two lithiums will be a simple swap out event (with some battery holding mods needed for sure).
I'm not seeing the down side here....

[Kayak73]

For ALL the lithium proponents...you are all stretching the limits a lot. First, lithium weighs 1/2 as much as FLA, exactly almost.


Second, every usage chart I have found on LiFeP04 states the cycles estimate at 50% SOC and a charge rate of .5C. Now sure, you can dump em lower than that just like FLA or AGM and they will take the abuse a bit better. They will take the larger discharge far better than FLA or AGM with no damage so that's fair just realize you are at the lower estimate of cycle life going 90%.


My take and every one selling them says if you need 150 AH usable you need 300AH whether LiFeP04 or FLA or AGM. That's the longevity rating. If you are thinking about taking lithium down to 90% - you won't be happy long - but it's your cash so go for it.


Finally it is not about "being able to afford it". It is rather about making a sound financial decision for many of us. The risk and cost is not justified to me at this price point.


The price point is clearly 10:1 at this time. 300AH or FLA Trojans cost $1 US dollar per AH, 300AH of lithium is just over $3000.00. No you can NOT reap all the benefits and claims of long life etc. by taking them down 90%, at least according to the charts the manufacturers provide.


I'm not changing my opinion, clearly those who have them are not either so I'm dropping out. It is just difficult to see so much stated which appears inconsistent with facts.


And last thought is the OP needed six batteries, not two. That is exactly where I got the $7000.00. Battleborn, whatever you pick is running around $1000/100AH right now. Could he drop down a battery, yes, safely no doubt. Should he regularly use them at greater than 50% discharge - not if he wants that long cycle life. I know, I know - lithium is magic, lithium is wonderful, I am wrong.


Oh yes, if you really think you can replace two 100AH batteries with one 100AH lithium - I doubt it seriously but it's not my money.


If I put in LiFeP04, which I probably will around this Fall or next year, I will definitely try for 300AH total just to actually be comfortable in the rig and not worry about the batteries. I won't drop down to 150 AH or 200AH probably, just doesn't make sense to me.


When all is said and done the lithium packs are a nice solution if you need them but everyone does not or does not think the cost is justified.

[Kayak73]

There is one big advantage using LiFeP04 no one mentioned - The voltage does not diminish during discharge like FLA or AGM. The things really deliver even greater than 50% discharge while FLA voltage drops down significantly past 50% and soon will get below usable voltage and battery damage.



To say that another way you still have 100% capacity up to the maximum rate of discharge.

[creativepart]

Bill, not trying to argue, but you have some facts incorrect. The main one being that usable Amp Hours in Lithium batteries are the same as lead acid.

Unlike Lead acid batteries, LiPo can be drawn down to 20% SOC or lower regularly, repeatedly without hurting the batteries.

Here’s a quote from BattleBorn’s website:

Most lead acid batteries experience significantly reduced cycle life if they are discharged more than 50%, which can result in less than 300 total cycles. Conversely LIFEPO4 (lithium iron phosphate) batteries can be continually discharged to 100% DOD and there is no long term effect. You can expect to get 3000 cycles or more at this depth of discharge.

Also, 6v lead acid batteries routinely weigh 60+ lbs each as opposed to ~27lbs for LiPo. It takes two 6v to make 12v, so that means 2-6v batteries weigh about 120lbs. So, weight savings are indeed approaching 75%.

Today a 100 amp 12v Battleborn costs $949 each.

So, there really is a 5/1 cost difference not your stated 10/1.

[al1florida]

Originally Posted by Kayak73

For ALL the lithium proponents...you are all stretching the limits a lot. First, lithium weighs 1/2 as much as FLA, exactly almost.

Second, every usage chart I have found on LiFeP04 states the cycles estimate at 50% SOC and a charge rate of .5C. Now sure, you can dump em lower than that just like FLA or AGM and they will take the abuse a bit better. They will take the larger discharge far better than FLA or AGM with no damage so that's fair just realize you are at the lower estimate of cycle life going 90%.

My take and every one selling them says if you need 150 AH usable you need 300AH whether LiFeP04 or FLA or AGM. That's the longevity rating. If you are thinking about taking lithium down to 90% - you won't be happy long - but it's your cash so go for it.


Finally it is not about "being able to afford it". It is rather about making a sound financial decision for many of us. The risk and cost is not justified to me at this price point.


The price point is clearly 10:1 at this time. 300AH or FLA Trojans cost $1 US dollar per AH, 300AH of lithium is just over $3000.00. No you can NOT reap all the benefits and claims of long life etc. by taking them down 90%, at least according to the charts the manufacturers provide.


I'm not changing my opinion, clearly those who have them are not either so I'm dropping out. It is just difficult to see so much stated which appears inconsistent with facts.


And last thought is the OP needed six batteries, not two. That is exactly where I got the $7000.00. Battleborn, whatever you pick is running around $1000/100AH right now. Could he drop down a battery, yes, safely no doubt. Should he regularly use them at greater than 50% discharge - not if he wants that long cycle life. I know, I know - lithium is magic, lithium is wonderful, I am wrong.


Oh yes, if you really think you can replace two 100AH batteries with one 100AH lithium - I doubt it seriously but it's not my money.


If I put in LiFeP04, which I probably will around this Fall or next year, I will definitely try for 300AH total just to actually be comfortable in the rig and not worry about the batteries. I won't drop down to 150 AH or 200AH probably, just doesn't make sense to me.


When all is said and done the lithium packs are a nice solution if you need them but everyone does not or does not think the cost is justified.

IMO the reality of lead acid versus lithium is somewhere in the middle.
Kayak73 is arguing the worse possibilities of Lithium. Others are arguing the best possibilities.
The truth is somewhere in the middle.

Just like so much of what is going on in this world, "I am right, you are wrong" or "I am the winner, you are the looser". The reality is in the middle. Things are not black and white, they are varying shades of gray.

As a user of lithium for 3 1/2 to date, I would not switch back for any reason that matches our style of travel.
One example: If we were to change our travel to only dry camp 1-3 days once a month or 3-6 times a year and then back to shore power, and we had a RV which had lead acid batteries then I would just stay with lead acid.

I also have extensive experience with flooded cell lead acid. About 30 years of not knowing the proper charge/discharge procedures and design. Went through lots of batteries. Then about 9 years of extensive use with a 2000 watt inverter so we could power all we use, including a microwave. That is also when I installed a battery monitor that showed the AH's used and replaced. What a world of difference.

About depth of discharge:
-- Yes you CAN take lithium to 20% SOC (use 80% of the capacity). Should you consistently discharge to 20% SOC? I don't and won't. I absolutely would not design my system to operate that way. I designed my system to use 30-50% of capacity. Sometimes this means I go down to 30% SOC and then back to 60-70%, but that doesn't impact lithium, like it does lead acid.
-- Can you take lead acid down to 50% consistently? Sure you can. However according to Trojan's documentation: Take their battery to 75% SOC and you get around 3000 cycles. Same battery down to 50% SOC and that drops to 1500 cycles. Take that battery to 20% SOC and the cycles drop to around 700. That is under laboratory conditions that means getting back to 100% charged before the next discharge. Getting back to 100% SOC seldom happens in real life. (You MUST have a battery monitor that shows AH's used and replaced to KNOW if you get to 100%. Battery voltage doesn't hack it.)

In my 9 years of use of lead acid, once I finally learned the proper care of them, I only took the batteries down to 70-75% SOC to occasionally 60% SOC. I also worked pretty hard to get them back to 100% at least every week, usually no longer than every 5 days.

Anyways, One size does not fit all. There isn't a right or wrong. Lead acid works just fine for many or most folks. Lithium works very well for those who have heavy demands on their batteries.