Expected solar output.

[booster]

Yes, you are correct.

I do disagree with this, see post #32 above. The sun all day is only part of the equation, if the array isn't big enough compared to battery bank size in a lead acid setup there aren't enough sunlight ours in a day to get the bank full, and depending on how many AH you are discharged, many/most AGM setups with normally setup controllers will never get you totally full per the battery manufacturers recommendations unless you are starting at only about 10-15% discharged and are in good sun for a long day.


The only time that lithium and lead acid charge at about the same rate (if it is typical solar that lead acid will take all power available) is the area below about 70% SOC, then it takes something in the area of 6-8 hours more to get to totally full. If you aren't back to 70-80% by 11am, and already in amp tapering, in most cases you will not be able to get full that day, and you will not get there very often at all if your controller switches to float after a fixed time like many do at about 4 hours of absorption.


Lithium does not have that problem because the acceptance rate does not change appreciably all the way up to full and you are much more likely to get all of your capacity back that day. It is probably the biggest advantage of lithium, IMO.


We have been testing this for many years as we have a modest 300 watt solar array and 440ah of battery capacity now. In the past we have had combinations of 200 watt and 160ah and 270ah bank with the 300 watts. We are modest power users, normally in the 30-50ah per day. This means we are in the tapering amps right from the beginning of the day as we are starting at nearly 90% SOC so in decent sun we will be full by early to mid afternoon. We were in over 100% temps for 5 days in a row once, with good sun so we got down to about 80% some day because of continuous fan use and the frig using more power and we still made full by sunset those days. Our controller stays in absorption until it reaches a preset amp reading (2 amps in our case which is about .5% of bank capacity in AH and what Lifeline recommends for true full) so if the controller is saying we are full, we really are. Other controllers will commonly say you are full when you are not due to them not measuring if the battery is really full or not and just going be voltage or and algorithm.

 

[ilmor-ClassB]

The only time that lithium and lead acid charge at about the same rate (if it is typical solar that lead acid will take all power available) is the area below about 70% SOC, then it takes something in the area of 6-8 hours more to get to totally full. If you aren't back to 70-80% by 11am, and already in amp tapering, in most cases you will not be able to get full that day, and you will not get there very often at all if your controller switches to float after a fixed time like many do at about 4 hours of absorption.

This I did not know. Interesting.

 

[booster]

This I did not know. Interesting.

There is a lot of information on lead acid battery charging spread out over many different discussions.


You might want to read this article that showed testing of actual charge times for lead acid batteries. The charge time charts are quite interesting to be sure. It is a long read so be prepared for that.


https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/


One thing that is always needed to remember is that achieving very accurate charging and monitoring doesn't come cheap if you want to get to 100% fully charged consistently. There are very, very few shore chargers that can even do it automatically and the same with solar controllers. No automatic ones for alternator charging off the shelf.


Very many, probably almost all, either don't know they are getting poor charging and shortened battery life or do know but realize the costs of getting that very good charging aren't worth it and it is better for them to just accept the shorter battery life. In small, less expensive, battery banks that a lot of RVs with lead acid batteries have, this is often more cost effective, with the downside being a progressive loss of capacity in a shorter time.


The manufacturers of the chargers and monitors certainly know that their chargers do not get the batteries to truly full, but have chosen to let them underecharge to prevent the more rapid failures that overcharging can cause. Without more expensive measuring of the charging in real time they cannot prevent both accurately. The monitor manufacturers have pretty much given up on giving the users accurate information on if the batteries are really full or not and changed their defaults to show full when most batteries are quite undercharged because they know the chargers can't do the full charge anyway and it prevents complaints. Most monitors can, however, be reprogrammed by the users to get the correct settings. Monitors, however, by themselves can't fix bad charging but the can show you that you have it.

 

[SteveJ-ClassB]

Tail Current

Seeings how tail current was touched on, what is a good tail current setting? I have two 100 amp hour LA batteries. My parasitic load is .5 amps, .7 if the gas fridge is fired. The solar charge controller is a Victron SmartSolar 100/30. It does have a tail current setting and will use this for cutting off the absorption charge. It also has what they call adaptive absorption charge. The deeper it is discharged the longer it will stay in absorb assuming it does not bump up against the tail current. The battery monitor is not Victron so the controller has no idea how much of it's total output is going into the batteries. I can see it on the monitor.

Stuff I have read suggests a tail cutoff of 2 amps per 100 AH of battery. I currently have the tail current cutoff set at 4.5 for the two batteries and the .5 parasitic draw. Does this sound like as good of guaess as any?

Thanks.

On TDY near Shady Valley, TN. playing with my motorcycle on the fun roads.

 

[booster]

Seeings how tail current was touched on, what is a good tail current setting? I have two 100 amp hour LA batteries. My parasitic load is .5 amps, .7 if the gas fridge is fired. The solar charge controller is a Victron SmartSolar 100/30. It does have a tail current setting and will use this for cutting off the absorption charge. It also has what they call adaptive absorption charge. The deeper it is discharged the longer it will stay in absorb assuming it does not bump up against the tail current. The battery monitor is not Victron so the controller has no idea how much of it's total output is going into the batteries. I can see it on the monitor.

Stuff I have read suggests a tail cutoff of 2 amps per 100 AH of battery. I currently have the tail current cutoff set at 4.5 for the two batteries and the .5 parasitic draw. Does this sound like as good of guaess as any?

Thanks.

On TDY near Shady Valley, TN. playing with my motorcycle on the fun roads.

Tail current all depends on the battery type and the manufacturer's specification. AGMs are usually in the .5-1%C or .5 to 1 amp per 100ah of battery. TPPL will be lower, maybe as low as .1% for some. Wet cells commonly are speced at 2-4%C.


You have bumped of the Achilles heal of chargers that can't measure actual current to the batteries but can measure the amperage out of the charger. I know all about that because our first adventure into tail current was with a Blue Sea charger that worked that way. The tail currents are really small amounts of current in many cases so loads can be a large part of the current supplied. Throw in stuff like compressor frigs that come on and off and the charger is chasing itself around the block trying to figure out what to do in many cases.


Probably not what you want to hear, but what I found is that there was not a setting that worked consistently as our loads changed over time. 6-8 hours or more of charging usually covers a lot of other stuff on and off in that time. You kind of set yourself up for over or under charging. Probably not as bad as leaving it alone in the first place, but still not very good. Don't count on the algorithm to give you the right absorption time as it will calc it off of voltage that will also be influenced by loads and temps.



Victron is very stingy with their data of how all there stuff works together, but my guess is that the Victron charger could be controlled off a Victron battery monitor to fix all of the issue. How much extras communication stuff would be need is unknown to me because when I called them to ask the said all that has to go through one of their "certified installers". No way it is worth hundreds of $ to me to get a couple of simple answers, but Victron is used to working with well off boaters with deep pockets, so that is what they do.


Another option would be to use a Victron monitor and use the internal dry contacts and a relay to shut off the panels to the controller when you hit fully charged, but you would lose having the float charge. My guess would be that if you then turned the panels back on to the controller, it would check voltage and go to float but having never tested that I can't be certain. This might be the best solution as it would cost only a monitor and a relay with override.

 

[SteveJ-ClassB]

Booster, thanks. Kinda what I was thinking about having an actual Victron monitor. As I currently use el cheapo 12 volt "maintenance free" batteries I'm not gonna get too excited about enrichening Victron's pockets.

My current batteries came brand new with out Trek when we bought it exactly two years ago. They are Group 31 MHD from Interstate. They are truck starting batteries also designed for operating a power gate. They do have some cycling ability. I believe they started out at 105 AH originally. I am now hitting absorb charging at about 170 AHs. I did reset the monitor too 200 max about a year ago from my original 210. Once I get home in about a week and access to shore power I plan on hitting these batteries with a pulse type "refreshener" after equalizing them.

As these are not true deep cycle batteries I am pretty much fine with how they have held up over two years so far. We do about 4 to 6 months per year camping without shore power, though we seldom drop to 75%. This paerticular trip has had temps down into the low thirties on several mornings. With the shading here I can only harvest about 30 AHs/day which has exercised the batteries pretty hard, though not below about 40%.

The shore power inverter/charger is an old multi stage Freedom 1000. It's plugged in virtually 100% of the time at home.

Again, thanks for letting me use your brain.

 

[GallenH]

I have been consistently confused about tail current. Booster, I know that you have Lifelines as do I. Can you tell me what the tail current setting should be on a Victron monitor for a 100AH LifeLine battery?

Maybe it's not that simple..............

As I said: Confused.

What exactly is tail current? I don't see mention in LifeLine specs.

Many thanks. Glenn

 

[booster]

I have been consistently confused about tail current. Booster, I know that you have Lifelines as do I. Can you tell me what the tail current setting should be on a Victron monitor for a 100AH LifeLine battery?

Maybe it's not that simple..............

As I said: Confused.

What exactly is tail current? I don't see mention in LifeLine specs.

Many thanks. Glenn

Lots of people have never even heard of tail current. It is often called other names like return current or others and Lifeline doesn't even use a term for it in their technical manual. It is on page 19.


Be aware this is term that only is used for lead acid batteries, not lithium.



https://lifelinebatteries.com/wp-co...F-Lifeline-Technical-Manual-Final-5-06-19.pdf


I think the best, but longest name for it would be "absorption to float transition amps" as that describes what it does.



The manufacturer's of the batteries have determined that the best way to determine if a battery is actually full to 100% of it's capacity is to look at the amps it is taking from the charging source while at the absorption voltage. So you would be looking at the voltage for a Lifeline at usually 14.3-14.4v in absorption and holding steady. Amps to the battery will continuously drop over time in absorption so you watch the amps dropping and when they hit the manufacturer prescribed amount the battery is full. Very simple in theory but hard to do in the real world for most people with RVs because the chargers are not capable of doing that kind of charge control. Lifeline wants you to get to .5%C amps where the C is you battery rated capacity in amp hours.



So you settings in the Victron monitor would be 14.2v for absorption and .5 amps for tail/return/absorption to float transition for each 100ah of capacity.


The big problem comes in that it is almost certain that your shore and solar chargers will not get you there most of the time accurately. Mostly the undercharge so the Victron will never get to that low an amperage and never read that you got a full charge, even though it may say 100% of the amp hours have been replaced. This is because of charge efficiency that means it takes over 100% replacement of AH to get full, usually in the 103-115% range depending on the batteries and depth of discharge. Some circumstances can make them overcharge also.


When the monitor never gets to full, it doesn't recalibrate itself to the new, now known, full point, by throwing out the extra AH in that were lost to inefficiency. If it didn't do that it would be off by those AH in the next discharge cycle, and each time you don't get full the accumulate and make the accuracy worse. This is why, I am sure, that all the techs that install them leave them set at the defaults, which in a Victron monitor are very conservative and will show full at probably 80% of being actually full to the battery spec for tail amps.


This is not the monitors fault, though, it is the charging systems fault for not being able to charge properly. Getting capable equipment is hard to do and expensive. There is only one off the shelf charger that I know of that will do it automatically without going to a fully integrated system like a custom Victron install. There is one other charger that can be run to do it manually, but the user has to do the monitor watching and then tell charger when to go to float. A few chargers now look at the amps but the reading is internal so includes van usage which messes up the readings because the loads vary. They work a bit better if you compensate for the loads in you settings but still miss by probably up to 10% depending on how much load is on. Solar controllers are similar, and I know of only two that will charge to actual shunt measured amps to the battery.



There are many discussions on the forum about the equipment needed and procedures.


Almost all of the users decide the shorter battery life and reduced usable capacity are OK with them rather than spend the amount it takes to do it all really well. They set the monitor to what their charger is capable of in many cases by doing some tests. But some like me and few others have done what it takes to get to very good charging. It works well for me, but I do all my own installs and designs so I only have equipment and material cost. It still was not inexpensive though.


It will be up to you how deep you go into it all, but a good place to start is with doing the testing on your system to see how full it is really getting the batteries now. This can be done by spending time watching the Victron amps during charging to see what amps it is at when it goes to float.

 

[Mike-ClassB]

As in most things technical, it depends on who you ask, or what you read. I've had 2 Relion RB100-LT LiFePO4 batteries in my Navion for 3 years. I use a MB 220A alternator to charge them while driving, 300W of rooftop solar with a Zamp ZS-30A PWM charge controller to help, and plug in to shore power to charge them with a PD9245 converter/charger w/added Charge Wizard Pendant to "kick it up a notch" once in a while if the One Place monitor or Zamp CC voltage number looks a little low.

I've had no problems with any of it. Always plenty of battery power off grid.
I like the Battery University website for lithium battery charging and maintenance information. It's simple and concise for lay people like myself.
It seems to be in line with what I've been told about these beasties from retailers and manufacturers.
Keeping it simple seems to work for me. Go figure?
(I have a small class C, but may return to van life at any time. Keeping an iron in the fire, as it were, on here)

 

[booster]

As in most things technical, it depends on who you ask, or what you read. I've had 2 Relion RB100-LT LiFePO4 batteries in my Navion for 3 years. I use a MB 220A alternator to charge them while driving, 300W of rooftop solar with a Zamp ZS-30A PWM charge controller to help, and plug in to shore power to charge them with a PD9245 converter/charger w/added Charge Wizard Pendant to "kick it up a notch" once in a while if the One Place monitor or Zamp CC voltage number looks a little low.

I've had no problems with any of it. Always plenty of battery power off grid.
I like the Battery University website for lithium battery charging and maintenance information. It's simple and concise for lay people like myself.
It seems to be in line with what I've been told about these beasties from retailers and manufacturers.
Keeping it simple seems to work for me. Go figure?
(I have a small class C, but may return to van life at any time. Keeping an iron in the fire, as it were, on here)

I think you have to remember that nobody, at least that I have seen, is saying that less the optimum charging will make a lithium battey fail in 3 years, or maybe 300 charge/discharge cycles? What is said is that the life of the batteries will probably be shortened by and unknown amount. We have seen the FitRV first system fail early due to high temps, so we know it can, maybe, happen to any system.



A lot of this, at least for me, is based on the specs that the manufacturers have touted over the years. Early on, they touted 10,000 cycles at 100% discharge with no temp or charging different from what you have for AGM or wet cells. Many now are at 2-3000 cycles and with a varying amount of limitations on charging, temps and storage specs.


I don't think anyone truly knows how much damage, or not, is done under varying conditions as it takes many years to see the results.


Now that the costs of lithium have been going down quickly, it may not make a lot of difference unless you live in a cold climate where storage temps could be a big factor as you still will get a lot of cycles. The balance is if it is worth the now smaller cost penalty to use lithium compared to lead acid batteries and if the benefit vs detriments tilts the balance of that calculation.

 

[Mike-ClassB]

I think you have to remember that nobody, at least that I have seen, is saying that less the optimum charging will make a lithium battey fail in 3 years, or maybe 300 charge/discharge cycles? What is said is that the life of the batteries will probably be shortened by and unknown amount. We have seen the FitRV first system fail early due to high temps, so we know it can, maybe, happen to any system.



A lot of this, at least for me, is based on the specs that the manufacturers have touted over the years. Early on, they touted 10,000 cycles at 100% discharge with no temp or charging different from what you have for AGM or wet cells. Many now are at 2-3000 cycles and with a varying amount of limitations on charging, temps and storage specs.


I don't think anyone truly knows how much damage, or not, is done under varying conditions as it takes many years to see the results.


Now that the costs of lithium have been going down quickly, it may not make a lot of difference unless you live in a cold climate where storage temps could be a big factor as you still will get a lot of cycles. The balance is if it is worth the now smaller cost penalty to use lithium compared to lead acid batteries and if the benefit vs detriments tilts the balance of that calculation.

Keeping it simple, for me at least, means set it, and forget it.
I have no "fuel gauge" or other measuring devices to tell me the exact SoC of my 200Ah bank. I don't worry about it, and as I said, I always seem to have plenty of juice to overnight off grid. So far.
How many charge/discharge cycles have my batteries had? I have no idea, but like you, I'd like to think the manufacturer's estimates for how many I should get is a lot more than I'd get out of FLA/AGM technology.
How deep have I discharged them, before bring them back up? Maybe once I actually got down into the mid 12V range, but they had been sitting in the driveway for a few days, unplugged, mostly cloud cover, so not much help from the solar. I plugged in, hit the booster (no pun) button on the Charge Wizard Pendant, and they were somewhere north of 13.5V after an hour or two of 14V+ charge current from my non-lithium capable converter/charger.
What does all this mean? Search me.
btw, you're still in the '07 Roadtrek? Nice. We kept our '02 190P for almost a decade, and sold it for a decent number a few years back. May you get as many solid years of touring or destination travels and fun from yours.

 

[booster]

Keeping it simple, for me at least, means set it, and forget it.
I have no "fuel gauge" or other measuring devices to tell me the exact SoC of my 200Ah bank. I don't worry about it, and as I said, I always seem to have plenty of juice to overnight off grid. So far.
How many charge/discharge cycles have my batteries had? I have no idea, but like you, I'd like to think the manufacturer's estimates for how many I should get is a lot more than I'd get out of FLA/AGM technology.
How deep have I discharged them, before bring them back up? Maybe once I actually got down into the mid 12V range, but they had been sitting in the driveway for a few days, unplugged, mostly cloud cover, so not much help from the solar. I plugged in, hit the booster (no pun) button on the Charge Wizard Pendant, and they were somewhere north of 13.5V after an hour or two of 14V+ charge current from my non-lithium capable converter/charger.
What does all this mean? Search me.
btw, you're still in the '07 Roadtrek? Nice. We kept our '02 190P for almost a decade, and sold it for a decent number a few years back. May you get as many solid years of touring or destination travels and fun from yours.

I think that is my point. If the price is low enough and the expectations not overly high (like they were a few years ago), lithium will probably turn in to a moderately longer lasting system than AGM and a moderate cost increase. Many will be fine with that setup. It is similar to where the more mature AGM market is now. You can get much better charging and longer life by getting better (expensive) charging equipment but most choose to accept lower life instead. With lithium it will all come down to how long people keep the system before moving on. AGMs will last 5+ years even with moderate care, and lithium should be at least double that, so how many purchasers will still have it if and when it fails?



We have had our 07 C190P since October of 2009 when we bought it new as a on the lot a while leftover. It was one of the very first produced with new roof style and new kitchen and rearranged locations for the charging system. We still have never seen a floorplan that we like better plus it fits through our garage doors so that is a big deal as none of the new ones will. Our mods and tweaks make it very easy and convenient to use for our style of camping so we will likely have it a long time more. Our handling improvements have made it a true 800+ mile per day (freeway) driver and at 70mph and no white knuckle even in high winds so it suits us very well.

 

[Mike-ClassB]

I think that is my point. If the price is low enough and the expectations not overly high (like they were a few years ago), lithium will probably turn in to a moderately longer lasting system than AGM and a moderate cost increase. Many will be fine with that setup. It is similar to where the more mature AGM market is now. You can get much better charging and longer life by getting better (expensive) charging equipment but most choose to accept lower life instead. With lithium it will all come down to how long people keep the system before moving on. AGMs will last 5+ years even with moderate care, and lithium should be at least double that, so how many purchasers will still have it if and when it fails?

So, that would make me a trend setter? I've always like to be a little ahead of the curve. I'll let you know when they fail, purely for statistical purposes.

We have had our 07 C190P since October of 2009 when we bought it new as a on the lot a while leftover. It was one of the very first produced with new roof style and new kitchen and rearranged locations for the charging system. We still have never seen a floorplan that we like better plus it fits through our garage doors so that is a big deal as none of the new ones will. Our mods and tweaks make it very easy and convenient to use for our style of camping so we will likely have it a long time more. Our handling improvements have made it a true 800+ mile per day (freeway) driver and at 70mph and no white knuckle even in high winds so it suits us very well.

I've done some stuff to my Navion (got a list of about 20 improvements/upgrades or more) to make it more liveable, too. Some is purely mechanical stuff, and some is personal convenience stuff. Just a week ago, I had to remove the buck converter proopane solenoid voltage reduction fix. There wasn't enough current available to keep the valve open. I had Lichtsinn add a Stay Longer propane T to the system, and it wouldn't have worked with the voltage reduction mod. Oh well....
Got a couple more that I may get around to, but I'm also looking at the EKKO as an alternative to the Navion, so I'm still deciding which way to go before adding anything more. The EKKO has a lot of standard equipment that makes it look more like the (almost) perfect small class C, and the AWD Ford Transit chassis makes it more of an all weather rig. But that's class C talk, and this is the B Forum.
Take care, y'all.

 

[GallenH]

thanks for your reply, booster!

glenn

 

[GallenH]

Follow Up Question

This last week I again camped along the CO river and deployed my 100W portable solar panel and didn't drive the RV again until I left, 4 days later. I have a single 100Ah LifeLine. When I read the solar controller on the panel at 10:00am the morning after arriving it read 5.7a even though the idiot lights and my Victron said "full." Not sure why this discrepancy existed. At about 1:00pm the same afternoon, solar controller was reading .9a, and at 4:00pm it was reading .3a. Full bright sun the entire time.

Can someone help me interpret these readings?

thanks.glenn