Sizing coach battery for my style of B use B

[Crank]

My "new" '96 Roadtrek Popular's storage battery is dead. Recognizing wide variation in habits and conditions, what are reasonable estimates by owners for amp/hours drawn /24h? I need an estimate in order to determine what size battery to buy (I like to boondock for 3-5 days).

This whole question worries me because the available battery space is 7 1/2" x 11" x 11" hi. (With some serious hacking, I could slide a longer battery in and out of the aisle, bypassing the weight issue).

The main DC power uses I anticipate are lights (LED), water pump, small fans (?hr/day), occasionally laptop computer; possibly heater fan (although we usually avoid temperature extremes). We have a Fantastic Fan, but I don't remember if it runs off 12v or 110v. Also detectors and idiot lights.

I'm open to advice on choice of a battery system: I find choice complicated, given all the variables and uncertainties regarding nominal published capacities. I prefer one 12v battery for several reasons if I can get adequate capacity. But I have an adjacent storage area that I'll reluctantly use for a 2-battery system, if necessary.

I'm upgrading to AGM, a Progressive Dynamics 4645 charger/converter and a Trimetric monitor for visible data on state of charge, thanks to advice here a while back. (Plus there is a dongle read out for the inverter/charger: is it useful if one has the Trimetric?

Lifeline's RV battery sizing calculator compensates for inefficiencies and seems the best way of finding the TRUE AVAILABLE capacity of a battery. It indicates that their 12v GLP-31T battery can produce 5.3 amps continuously for 12h before exceeding 50% drawdown (~12.1v). Two Lifeline 6v GLP-4CT batteries would have almost twice the capacity but at twice the price. 2 12v might be as good, except that Trojan 6v batteries are more robust: maybe Lifeline are too.

I can get Trojan and Lifeline AGM locally (I'm told Trojan's C-max TRUE deep cycle batteries are not being made at present), but it's difficult to compare products, due to uncertainty about the assumptions and standards used to calculate nominal capacity.

I appreciate any responses to the several questions embedded here: most have been asked before, but perhaps from a different perspective.

[ptourin]

7.5 x 11 x 11? Your Lifeline 12v GLP-31T won't fit - it's almost 12.9 long. But aside from which battery...
Your typical use sounds similar to mine. Your FanTastic will be 12vdc. Mine draws 1.0, 1.3 and 1.8A on its 3 speeds. So it's not a gigantic draw. My LP Furnace draws 3.6A when it's running. LED's differ, but mine draw 0.22A each. You didn't mention a fridge - the draw on LP would be different depending on the fridge - mine is 0.23A when it's running. My LP HW heater draws about 0.55A. The water pump draws about 7A but of course it doesn't run very often. I have a MacBook Pro that averages ~2.5A - but I run it through a small inverter, and there's some current draw from the inverter too. Plus the parasitic draw - detectors, etc. Hope these are useful numbers for you.

I had a PleasureWay that sounds similar to your RoadTrek, but I didn't keep numbers back then. I now have a Leisure Travel Unity, which is a bigger rig - 2 house batteries instead of 1 - but aside from more lights, and a bigger fridge, I expect my usage is not too much more than with the PW. I assume that I usually run 95-110 aH/day, depending on what's running. That includes a lot of computer time - 20 aH worth - so you can save there. It includes 5 aH of TV watching and 11 aH for the furnace. 6 aH for 6 hours of vent fan, 4 for a few hours of the dash stereo. My phantom load is high, about 35 aH, partially because my LP is controlled by a solenoid so I'm drawing current whenever the LP is turned on, whether I'm using it or not. So you can get this number down a good deal.

Still - put together a realistic power budget and see where you come out. We could dry camp for a day with our PW, then had to drive around or plug in to recharge - it had a single battery with about 95 rated aH. Our current rig came with 2 of those batteries, and we could dry camp 2-3 days if we were really careful.

[wincrasher]

Ptourin - you can get a DC car adapter for your macbook pro and save the inverter losses. My 2014 vintage macbook pro is actually native 12v, so the adapter is just a magsafe connector on one end and a cigarette adapter on the other.

My old macbook (2011 vintage) had a small transformer on the car adapter to get it to the correct voltage - don't recall what it was, but it wasn't 12v native.

[ptourin]

My MacBook is 18.5vdc. I could get a DC-DC converter for it, just haven't gotten to it yet - I just did a web search and I see them for about $40.

But on my last RV I upgraded my entertainment system - the original system was 120vac and the RV had no inverter at all - DVD's and TV only with shore power. The Blu-Ray player I installed was 12vdc so I could feed it straight through. The HDTV was 19vdc so I got a DC-DC for it. Worked very nicely - the converter was very tiny and got warm but not hot.

Crank, I think that watching a DVD movie cost me about 5 aH, so the entertainment wasn't a big show-stopper.

But it seems your real problem is space. I was just looking at Lifeline and FullRiver AGM's, and most of the 12V sizes are more than 11" long - you're really limited by that length.

[Ridenfun]

Just went thru this issue replacing on my older 2000 Okanagan, which had a single sealed & vented box under a dinette seat. 12 volt options, regardless of brand were as follows:
Grp 24 10 7/8"L X 6 3/4" W X 8 3/4" H
27 12 7/16 X " "
31 13 x " 9 1/4

Trojan wet T105 were about 10"L X 7"W X 11 3.8"H and would just fit in the area if I removed the vented sealed box, which meant building a homemade vented box to the outside. They had 220 AH capacity (in series), biggest of all options that would fit, but heaviest and a very tight fit, and requiring most maintenance, which would have required removal to top up the batteries with water

In the end I used a single type 31, 99.9% pure lead AGM with 105 AH. with no need to direct vent (There was a Lifeline brand GPL31XT @ 125 AH, but couldn't source it locally in Canada and it was 50% more $ than what I chose for 25% more AH. I won't have enough capacity for my worst case, so will need to recharge, BUT these high lead content type will recharge at much higher rate than any wet cell without damage due to lower internal battery resistance (less head buildup I guess) and self discharge at very low levels when not being used, hence virtually no need to remove etc to keep them in good shape. I'm considering buying a cheap small genset, and using high amp charger to keep them topped up for longer stays off grid. It will depend on my actual usage needs.
Good luck in your choice, powering these class B units is limited due to the space available.

[cargovanconversion]

Sizing your batteries is a highly personal affair. Starts with calculating your amp use in detail. That leaves you with the amp/hours you need as storage.
The problem always is that amp use is an approximation and anything that follows are more approximations. Such as the seasons you are in, the location, solar or not, boondocking, etc.
Then, with a safe discharge maximum of 50% on lead-acid batteries, you probably should count on 40%, as batteries deteriorate over time.
If your dead battery was not caused by malfunctions or defective materials, you clearly will have underestimated your usage.
Purely based on your 3-5 day boondocking expectations and my personal experiences, I would say, get as much battery capacity as possible, but as I said before, your requirements may differ greatly and if you underestimate your usage, you'll end up with more dead batteries.
I wrote down some basic information about it here: cargovanconversion.com
That may help you with your decisions.

Van Williams

[ander]

my 94 dodge pleasureway had the house battery on the drivers side rear corner under the floor.
with our use we could go maybe 2 days if we really conserved on that one battery.

when i decided to add solar i just went the 2 6volt rout and made room and a box for them.
the last time we were off grid for 48 hrs straight with little charging (rain and clouds) we only down 30%...

a single battery was doable for us..but having the 2 6volts is soooo much more confortable.

[GtDad]

My PW traverse has vented battery box big enough for 2 group 27 batteries. BUT batteries in parallel are harder keep balanced. I ended getting two group 27 6V Agm batteries from batteryworld in vancouver. These are batteries design for Electric vehicle use, robust and safe. This gives me 210AH which is pretty decent. They charge very fast and sit at slightly higher Volts that wet cels. I have intellipower 9130 charger converter with the add on charge wizard controller.
So far this has been a fantastic setup..

[Crank]

Thanks for the informative discussion, everyone.

I did mention that I can hack the battery compartment and install a larger battery, which I will do.
But it appears I was asking the wrong question: not “how to size the battery system?” I should have asked a more fundamental question: “how to charge the batteries?”
I say this because I have done a lot of reading and made inquiries since my opening post. It appears that many (most) charging systems do not deliver sufficient voltage to fully charge the battery(s). AGM batteries need about 14.7 volts to attain full charge ( but csn accept more, which is why they can charge fast), and RV chargers don’t usually exceed 14.4v – at least I have not found one yet, and preliminary indications are not encouraging. This problem seems to be little known. I don’t want to be slowly killing my batteries by consistently undercharging them: they need to be fully charged every week or two to stay in good health.
It is unwise to draw down a battery more than 50% because doing so shortens the life of the battery (AGM batteries can be drawn down 70% on an occasional basis). If the battery is not fully charged in the first place, one can only draw it down about 40%: unacceptable! Forty amp hours out of a 100Ah battery, (a size which I was considering) probably provides enough power to run a small RV for two days, unless supplemental power (solar or generator) is available. I’ll need another battery.

So now my question is: does anyone know of a quality charger/converter that can deliver 14.6v or more, suitable for use with AGMs in a RV? Or can I use the old converter and just add a modern charger?- and if so, what?

[Crank]

Ridenfun, what brand of battery did you end up with?



Like me, you find it inconvenient to access the batteries. Well, with AGM, you only have to do so to check the terminals for corrosion annually (or less) because corrosion is very unlikely with proper protection (no leaking acid). You need voltage readings to monitor the performance and health of your batteries, so you can permanently wire in a voltmeter, located remotely.


I’m not sure what you mean by “using a high amp charger”. I hope you don’t mean what your words imply: the main point to realize is that it is worse for the battery (and dangerous) to overcharge it than to undercharge it. When supplementing with a stand-alone external generator, just plug the shore line into it, and the RVs charger/converter takes care of voltages to the battery including reducing charge to 13.2v when charged.
If you don’t have a RV charger/converter, then hooking up a DC charger directly to the batteries presents obvious risks, including overcharging, which can seriously damage the battery and is also dangerous because the only charge regulator is you. Beware of overheating. You have to know the highest safe voltage to use (at least 14.6v). You also need to know the state of discharge to determine for how long you can apply DC current without overcharging. It is probably unwise to aim at keeping the batteries literally “topped up”, because doing so requires a specific choreographed sequence of changing voltages best done every two weeks of so: rather, aim at boosting them to between 80 and 90% of total capacity. A fully charged 12v battery should measure about 12.8 open cell voltage (OCV, meaning there is nothing connected across the terminals: the only problem is that you must wait at least 4 hr in OCV condition for the battery cells to stabilize). You can install a purpose-built switch that can be turned off from outside your enclosure to break the positive connection and create a OCV condition. (The switch is useful for eliminating all current drain if you need to leave your RV for a few days. You would also need to add a trickle charger with an external switch if your batteries are to be fully isolated from a power source for some time.)


I am not an expert: therefore check everything I suggest with someone who is!

[Crank]

Ridenfun, what brand of battery did you end up with?



Like me, you find it inconvenient to access the batteries. Well, with AGM, you only have to do so to check the terminals for corrosion annually (or less) because corrosion is very unlikely with proper protection (no leaking acid). You need voltage readings to monitor the performance and health of your batteries, so you can permanently wire in a voltmeter, located remotely.


I’m not sure what you mean by “using a high amp charger”. I hope you don’t mean what your words imply: the main point to realize is that it is worse for the battery (and dangerous) to overcharge it than to undercharge it. When supplementing with a stand-alone external generator, just plug the shore line into it, and the RVs charger/converter takes care of voltages to the battery including reducing charge to 13.2v when charged.
If you don’t have a RV charger/converter, then hooking up a DC charger directly to the batteries presents obvious risks, including overcharging, which can seriously damage the battery and is also dangerous because the only charge regulator is you. Beware of overheating. You have to know the highest safe voltage to use (at least 14.6v). You also need to know the state of discharge to determine for how long you can apply DC current without overcharging. It is probably unwise to aim at keeping the batteries literally “topped up”, because doing so requires a specific choreographed sequence of changing voltages best done every two weeks of so: rather, aim at boosting them to between 80 and 90% of total capacity. A fully charged 12v battery should measure about 12.8 open cell voltage (OCV, meaning there is nothing connected across the terminals: the only problem is that you must wait at least 4 hr in OCV condition for the battery cells to stabilize). You can install a purpose-built switch that can be turned off from outside your enclosure to break the positive connection and create a OCV condition. (The switch is useful for eliminating all current drain if you need to leave your RV for a few days. You would also need to add a trickle charger with an external switch if your batteries are to be fully isolated from a power source for some time.)


I am not an expert: therefore check everything I suggest with someone who is!

[ptourin]

This is sort of a cheap armchair suggestion <g>... have you thought of emailing or calling Randy at Best Converter? Lots of RV people seem to go to him - looks like he has a lot of experience with RV charging systems, and I expect he'll be able to quickly tell you which chargers are best configurable for AGM's.

[Crank]

Actually, Ptourin, yes. I did exactly that about a year ago, making it clear I wanted AGM, and I was recommended a 3-stage upgrade kit. I was unable to immediately proceed. Recently, I started looking for suitable AGM batteries, and came across comments that they require (14.6+v) and a hint that a lot of chargers are not up to it. I called Trojan to get their AGM charging specifications (14.7v) and checked some charger specifications: the recommended kit and the others put out no more than 14.4v (0.2v short is significant to attain a fully charged battery). An article by an electrical engineer & full-time RVer mentioned a lot of RVers have difficulties, having no idea their batteries are chronically undercharged.


Consequently, I called again to explain my concerns, and was interrupted with the impatient statement that he got lots of calls like that, and (basically) It was all nonsense, and I should just install the recommended upgrade kit and be happy… no technical explanation. I don’t expect rudeness or, as a scientist, accept statements without basis.



So I’ll be asking more questions elsewhere. Nothing is simple about the physics of battery charge and discharge, especially in systems that have variable inputs, like solar or generator, and varying sized battery banks. It is difficult to measure State of Charge (SoC) accurately in sealed batteries: the idiot light on your control panel that tells you “Full” is lying: it means: Good Enough” (for some). So it’s not surprising if most don’t know they may be starting out with 90% capacity, especially as few have training in the subject. I don’t, hence all the reading recently: I’m cautious about reaching conclusions because much on the web is opinion, certainty is rare, and with batteries, little is easily understood.


What next? I need to get the van operational. I may buy one AGM battery and the upgrade kit as a place to start, and test to confirm what I have learned or suspect. If the upgrade doesn’t deliver, I will make do until I find a solution.


“Nothing in the battery world is absolute.”

[ptourin]

Oh, this rings a few bells alright! I'm not at home and don't have some of my spreadsheets available, but I seem to remember that when I looked into AGM's, different brands recommended slightly different charging voltages. It would be so handy if these multi-mode chargers had pots so you could pick your own setpoints - I suppose they don't do that either because it ups the manufacturing cost or because it leaves more leeway for users to trash their batteries out of ignorance <g>... I've been going through the same thing with my LiFePO4 installation - we're still watching the SOC and turning the charger on and off manually as there's no consensus on whether leaving the charger connected will overcharge and cause battery damage.

BTW - I had somewhat the same experience at Best. My first call provided me with useful info, but when I called back with further questions I got the same sort of response. The situation with SmartBattery has been even more difficult - they seem to have sales staff and support/repair techs, but I haven't found anybody that really sounds like a support engineer (or any kind of engineer), and at this point I have the batteries but mistrust the info I'm getting about them.

Have you looked at Iota Engineering? I had a memory that they had configurable 4-mode chargers, so I just took a quick peek at their website - the chargers with the IQ4 circuitry say "up to 14.8" for bulk, 14.2 absorb, then float and equalization modes. I didn't take the time to check what "up to 14.8" means - it sounds configurable, though possibly only through one of those choose-the-battery settings where you select standard or AGM. But they clearly have the capability of getting up into the high 14's, so it's worth a look. Sorry, more armchair commentary <g>...

[Crank]

Well, better than armchair commentary: a very interesting post.

I got lucky today: I found the charging rate for Lifeline batteries: they don't specify a bulk charge but their recommended absorption rate is 14.4v. So the kit I was offered will barely do the job, I suppose, although slowly: what do you think - there is 0v headroom? AGMs can take a higher rate of charge than 14.4 for faster charging. I'll probably take the easy way out, and install a kit. I'll take a look at the Iota first, though, although I probably don't have the knowledge to install it.

I fully agree that one needs to be able to set one's own charging profile, in view of the different types of battery now on the market. The buttons to select battery type are inadequate in view of the different requirement of Lifeline and Trojan, because one still gets a canned charge profile.

I have found more easy-install alternative upgrades for the entire converter/charger, which are easy to install, but I don't fully understand the differences between them yet.

[booster]

Lots of information in this discussion, and maybe I can help, or not, clarify some things,as I see them, after our several years of messing around and testing stuff.

The battery charging voltage for AGM being all over the map is very confusing. Lifeline is listing 12.6 on most of its cut sheets for the batteries, but still at 14.3/14.4 other places. I tested our 4 AGMs Lifeling GPL4CT six volts on the bench at both voltages, using our Magnum MS2000 and ending the charge when the amperage, measured with a shunt and Magnum monitor, quit dropping. Bottom line was that both voltages got them equally full, based on letting them rest, checking the voltage and then putting them on at charge of 14.3 volts to see the amps. No real difference, except the 14.6 got full a little faster, but generated a lot more heat (10+degrees in the battery) so had to be gassing more.

My conclusion, and from talking to Lifeline, is that many new multistep chargers are consistently undercharging the batteries with too short of absorption time as they are scared of overcharging and don't know how big your battery is or how far it is discharged. We have seen this in nearly every charger I have tested with fixed timers. Many will not even start a charge cycle unless the battery is seriously low, so no topping off possible. The exception is the Progressive Dynamics, which uses a fixed 4 hr absorption every time you plug in. 4 hours is going to be too long for small batteries, and too short for big banks, and doesn't consider how discharged you are, but with a Charge Wizard you can manually take it to float or absorption if needed.

On the damage to a battery by over or under charging. A huge overcharge will kill a battery quickly, but we are talking many hours/days at full charge voltage. Small amounts of overcharge are probably no more damaging than undercharges. The small overcharges will very slowly lose electrolyte and capacity, but won't get heat type failures, and the undercharges will slowly walk down capacity due to sulphation. Sulphation can be sometimes reversed by equalizing, now more commonly called "conditioning" for AGM batteries.

Now for the hard part--charging them right all the time, or often enough to keep them healthy, without overcharging from any source or combination of sources.

IMO, the only way to reliably charge to full, without overcharging, is to end the charge based on the amps to the battery from the charger, or return amps. It can be done automatically with the charger or manually by watching a battery monitor that runs off a shunt. All the sources need to be controlled this way, in our case 3 of them. Shore charger, solar controller, engine alternator.

There are very few chargers that will end the charge based on return amps, measured of a shunt. Magnum is one, probably Outback also but not certain. Chargers like Xantrex or Blue Sea that end the charge based on amps don't work right because they use an internal measurement of amps that can include your variable loads in the van which messes things up and causes overcharging.

For Solar, you also need a charge controller that ends charging on return amps of a shunt. It should also have a very low minimum absorption time so that if you are sitting outside, on the shore charger, or with fill batteries, you don't want a long absorption time every day (minimum time overrides the return amps). There have been batteries destroyed by this issue. You also don't want a fixed voltage solar as you need it to go to float, obviously. Blue Sky makes nice shunt controlled charge controllers, as do others, I am sure. Morningstar's are mostly just timers, so not good

For charging of the alternator, you need to be able to turn on and off the connection with some sort of relay, and you also need to be able to see the amps going to the battery (which you would be able to see on either the shore charger, or solar controller remote as they have built in monitors). As long as you watch the amps to end charging, don't sweat the voltage off the alternator all that much as long as it is in the range of 13.8-14.6v as you won't be over or under charging using the amps to control.

As for how often is needed to get totally full, I have never gotten any really good information and it is really untestable in the home world. Most of the manufacturers say 5-7 charge cycles or so, which can be days to weeks to months of use, so don't go by time alone IMO.

From what I have seen on the bench tests, the Lifelines drop voltage very slowly with no load, if they are taken totally full. They will still be at 13.0 volts after a couple of months. To me it seems silly to be putting the approximately .2 amps into them (440ah) on float during that time as my guess it is not all that great for them when that full. When we are camping, we will have the charger set to go to float after a charge cycle to power our use and leave us full. When stored the charger will be set to "silent" mode which will do a full shutoff of charging, and then it will monitor the voltage after that, when it hits set voltage (probably 12.8v for us) it will run another return amp controlled charge cycle.

Without getting the information about amps going to the batteries, it is very, very hard to determine actual state of charge your batteries. Using voltage is a moving target as the batteries age, when you check etc, and with AGM you can't confirm the actual SOC by specific gravity.

Doing all the controls necessary for having maximum capacity available from full charges, and the battery life saving features is not particularly cheap, and I do think there is a real question of how to do things. You could buy several sets of batteries for the cost of getting the equipment to charge the best, if you already have a system in place. If you are starting from scratch, the extra cost is much smaller to do it right.

[Crank]

Thank you for taking the time Booster, another great post!
You confirm a number of things I have found from some of the more analytical and thoughtful posters and other sources.


You have covered a lot of ground, and identified some areas of uncertainty, because of inability to measure plus multiple uncontrolled variables. It is too much for me to assimilate all at once.


So, since I am the OP, and have a simple set-up, I am going to try to use your information to find the best practical (but probably not optimal solution for me.) If I can get some agreement on that, then it provides a place for others to start.

I only have a 19’ Roadtrek, set up for 2 riders. The only 120v load I anticipate without shore power will be a laptop for an hour or two if there happens to be a signal. I will travel infrequently, for 3-14 days, initially at least. Water and waste tank capacity restricts boondocking to about 3-4 days before a night of “shore leave” and serious recharging.


I am contemplating installing about 200Ah of Lifeline storage (it looks like their 14 -15v charge requirement will be more easily satisfied than some) in the moderate temperature conditions I will choose. I am going to replace the charging portion of my old 1 stage Magnatek with SOMETHING 3-stage that seems a good choice, and a Trimetric with shunt. I have no solar to complicate things, but I do have an Onan generator which I hope not to use, but could to restore some charge, but perhaps not to attempt fully charging the batteries. (I should be able to use shore power often enough for that.)



“Progressive Dynamics uses a fixed 4 hr absorption every time you plug in. 4 hours is going to be too long for small batteries, and too short for big banks, and doesn't consider how discharged you are, but with a Charge Wizard you can manually take it to float or absorption if needed.”

That’s the closest I have seen to a specific recommendation, Booster, and they happen to make a swap-out charging unit (PD4645) for my Magnatek, a cheap solution for me. They seem to be a volt short in output, however, below 70 degrees F: PD says:

· BOOST Mode 14.4 Volts - Rapidly brings RV battery up to 90% of full charge.
· NORMAL Mode 13.6 Volts - Safely completes the charge.

Can a lower voltage bring up the charge … to what ... what is the endpoint here?

Would two 100 Ah batteries fall within that too small and too large window?

Am I close to a “good-enough” system for my needs, given that perfect is unattainable? The "needs" are a well charged battery bank at the beginning of the trip and a reasonable battery life. What would you change?

Booster, I did not understand your comment about (over?) charging with the alternator while driving. Any time one leaves shore with a fully charged battery, the alternator will be trying to charge the Lifelines if the controller does not prevent it, so switch off the relay you suggest installing and forget about it until some charge is used up? “As long as you watch the amps to end charging” - how do I do that, unless with the Trimetric, and what am I watching for, 14.6A? And how do I do it from the driver’s seat with my foot on the gas keeping the alternator churning? (I have not had time to study how to install or use the Trimetric yet on a charger that is not set up for it).

I have seen the advice to fully charge the AGMs at the end of a trip, and that certainly would seem to make a continuous float charge redundant. Just need to equalize once in a while. But the Progressive Dynamics goes to float at 13.2 v and equalizes every 21 hr for 15 minutes at 14.6v, which seems excessive to me. The only option I can think of is to put the shore power on a timer that runs it for a cycle every week or two or something similar.

Thanks for your generous help.

You are right, SoC is a bitch! Let's have another shot of tequila!

[eric1514]

There comes a point in time when you have to ask, "Do I own the battery or does it own me?"

Eric

[ptourin]

Many of the power centers are like your Magnetek - the bottom section has a converter/charger unit and the upper section is fuses and breakers. So if you get the right replacement for the converter/charger, it's a matter of unbolting and sliding the old one out and sliding a replacement in - you keep the power center but replace the converter/charger. I just did this in my present LTV MB when I moved to lithium batteries.

The Lifeline site says that they recommend the same voltage for bulk & absorption modes - 14.2-14.4v. Then they recommend a float voltage of 13.2-13.4v. So that Progressive Dynamics PD4645 upgrade converter/charger is close - both the boost and equalization modes are 14.4v, which is quite good. Their normal mode is 13.6, which is a bit high, and their storage mode is 13.2.

Their WFCO 8945 upgrade is also about the same - bulk is 14.4, absorption is 13.6 and float is 13.2. Same voltages as the PD4645, but they use more standard terminology to describe it.

I don't know enough to want to comment on whether these voltages are close enough or not - Booster has looked into this stuff in much more detail than I have. But I was surprised at the charging voltages you mentioned - I'd take a peek at the Lifeline site again, as it looks to me like they clearly want 14.4 for the main charge phase on their RV AGM's.

[Ridenfun]

I ended up buying a Motormaster Nautilus XD AGM, size 31 from Canadian Tire (in Canada) as I could not source an AGM 6V solution locally. This is their top AGM model, (they have 2) with 99.99% pure lead. It is rated at 100 AH and 220 min RC, but unlike the same brand basic AGM will provide 400 cycles at 80% discharge and 900 cycles at 50% discharge levels which is much better than even their standard AGM. Also capable of accepting fast charging. We'll see. I needed to get a battery to use to go camping last weekend so couldn't delay any longer. Even though only 100 AH, it will accept deeper discharges still with good recycle numbers and has a full 3 yr replacement warranty.
We'll see how it goes, but I wanted/needed AGM to avoid having to go to a sealed and vented box as with wet and I didn't want to have to build a box capable of even 1 type 31 battery. If this turns out to be insufficient for any reason, I'll repurpose it to my sailboat next year as it also has a very low discharge rate when not in use.(claim is "up to 2 years on a full charge with no loss of capacity".
Was interested to read others comments re recharging. I have a separate battery charger (not the converted in the van) that I used (this once) to top this battery up after I'd used it. The charge has settings for wet lead acid, AGM and Gel type and selectable amp charging rates. It recharged from 70% full reading (I forget the voltage but can also display that) in about 23 minutes at 6 amp which seemed quite fast to me. The battery didn't even feel warmer once charged, which I believe is a great sign.
Again, we'll see how it really lives up to the claims.