Floating vs Storage Voltage Question

[BFL13]

Moved this from another thread to open the topic generally. Question was if PD converters with the 13.2 storage voltage were compatible with floating voltage specs at 13.5 and above.
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Many (all?) battery specs have the same floating voltages (2.25 a cell or so) My AGMs did and also the flooded batts I have had.

PD's are used successfully with all those other batteries according to various reports

Trojan eg, has 2.25 too, and says not to float either flooded or AGM at all if they will be charged frequently. ("cyclic use"?) So the PD's "storage" mode at only 13.2v is confusing. Is "storage" really "float" or something else?

https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf

Float is supposed to just make up for self-discharge so 13.5-13-8 typical seems high for that, unless it is GC2 6s?

Resting voltage of a full flooded is more like 12.8 so 13.2 is more above that. My ordinary AGMs spec resting at full was 13.0 though, and nobody said a PD is no good with AGMs.

Now I am not sure what "floating" vs "storage" is all about. Anybody explain? Thanks.

[red31]

JCI in this ole spreadsheet shows 12.9-13.1 float forever!
the tab at the bottom "Marine Battery charging"

https://docs.google.com/spreadsheets/d/1csYoEciHDwUL2wxRO65H3Vj8gGdA8Paiw_Y-HcIvBBE/edit?usp=sharing

I've always thought of float as a voltage that neither charges nor discharges, Mex has talked of floating his 31AGM for years that maintains capacity.

[BFL13]

Battery specs that have "for cyclic use" 14.6v and "for standby use" 13.6v "Float" don't help RVers who do some of each.

An RVer wants to know what to do between trips. What is "between trips" called? Float or Storage?

There is no 13.2 in the battery specs (except that one from US Battery) If you are supposed to float at 13.2, why do the specs say Float is at 13.6? Trojan says don't do either if your between trips time is over a week (Wets) or over a month (AGMs)

If you go out and turn on the fridge a couple days before leaving, and it needs 12v to run that, and you have an inverter/charger, how are you going to supply the 12v? So is that your start of the next trip instead of when you actually leave?

If you are on 13.2 with a PD and go out there between trips and turn on a light, it jumps to 13.6. Does that ruin everything? Are you allowed to use your RV like a regular person or not? Phooey.

[pianotuna]

BFL13 wrote:
There is no data on what you lose in number of cycles /lifetime by floating when you really shouldn't between trips according to the guidelines.

Actually there is inferential data.

In my travels on the wobbly wide web, I found out SiO2 used in "float" situations have a life span of 18 years. If they are cycled to 50% the life span drops to 7.67 years.

In my case, the SiO2 may exhibit a lifetime guarantee, as I'm no longer full time--and the solar system will keep them in float between trips. In fact, I plan to not worry about cycling below 20%.

[MEXICOWANDERER]

It's been done. Thirteen point two volts at 35°F minimizes chemical activity but it has a time limit of about 4 months. Recharge the battery fully then put it back into suspended animation. The 13.2 volts must be applied constantly. Colder does not yield that much supeirority.

[profdant139]

You'd think that someone, somewhere, would have done a scientific study about whether trickle charging at 13.4 shortens the lifespan of a battery, compared to a more active method of battery management. And if so, by how much?

If trickling reduces battery life by (say) ten percent, then I am ok with continuing my lazy behavior. But if it cuts battery life in half, that's a different story.

[BFL13]

So maybe you are supposed to get the batts to true full first, and then not float them if not using them for a while (wires off), but if you have to float them for a while after reaching 14.x and staying at that for a while and then dropping to float too soon, you should float them for a while before going wires off just to get them full first. 🙂

But by then you will be getting ready for your next trip. What a PITA!

Meanwhile you should really stay at 14.x until at true full, so that whole thing with dropping to float early and then catching up on float does not meet the battery specs either.

So you can only do it "right" if your charger can be made to stay at 14.x till amps are down to almost zero (0.5a/100AH with AGMs), and hardly any RVers have that equipment to do that or desire to fuss that much.

It is so easy to just go on a Float between trips (not calling that "storage") except in actual storage for the winter for several months where there is no shore power. Now you have to do it "right".

There is no data on what you lose in number of cycles /lifetime by floating when you really shouldn't between trips according to the guidelines. Most of us never do as many cycles as we could with our batts, before they die from other causes, so would we even notice if they died earlier from floating when they should be wires off?

Having gone round and round on this, I think in our particular case where we have no lengthy winter storage, it is just too much bother to do it "right", so phooey on the whole thing. Sorry about that, Trojan!
It is what it is.

Each RVer has to decide what applies to his own case for what to do.

[pianotuna]

13.2 for 128 hours (7 days) also works.

[Gjac]

BFL13 wrote:

profdant139 wrote:
Bear in mind that there are two types of battery users on this forum: experts and the rest of us. Experts will (correctly) lavish attention on their batteries, getting maximum performance and longevity. And for that audience, it makes sense to carefully adjust the voltage of the charging system while the batteries are not in use.

For the rest of us, it is enough that we put the batteries on a trickle-type charger when they are not being used, and monitor the water. The manufacturers of the chargers pre-set those units -- there is no way for the end user to alter them, as far as I know.

The "set it and forget it" approach is not perfect but it is adequate for most RVers. But if your life depends on your batteries, you have to take a more hands-on approach.

Then, of course, there are the "do nothing at all" people who just let their batteries sit there and rot and then recharge them before each camping trip. (I used to be one of those folks before I learned how expensive that method really is.) The "do nothings" are not even reading this thread.

But they will, eventually. 😉

All true. Another thing is that most chargers that drop to float after a time at 14.x do so before the battery is completely charged.

So if you disconnect after the charger says they are full, you miss the following time at 13.6 when the batts might get a little more charging towards true full.

I am not clear how long on float you need to be after a time at 14.x to finish the recharge so you can disconnect. It might not even be happening. There is SG lag, so the apparent improvement in SG next day after being on Float since the recharge might just be that the SG has caught up, not from more actual charging.

I think this is very true, I don't have any sophisticated equipment to check this but I have noticed over the years of dry camping if I float my batteries at 13.2v after my "Smart Charger" says full, for 3 days before I go camping I can go 2 more days before my 2 6v GC batteries get to 50% SOC. I don't often stay in the same CG for 7 days but I have done this about 15 times on these batteries. From 5 to 7 days to me is significant. Now granted maybe I was more careful about light usage but I firmly believe that 13.2-13.6v constant charge helps.

[BFL13]

pianotuna wrote:
Hi BFL13,

Did you get a 2nd SiO2? I thought you were using flooded six volts for the "house" loads and just using a single SiO2?

I put the 6s back in the MH and ordered another SiO2. Cost is crazy but makes the whole TC set-up a lot more tidy. The second one did not cost as much as the first. You should get a good deal on buying so many at once.

[pianotuna]

Hi BFL13,

Did you get a 2nd SiO2? I thought you were using flooded six volts for the "house" loads and just using a single SiO2?

[BFL13]

profdant139 wrote:
Bear in mind that there are two types of battery users on this forum: experts and the rest of us. Experts will (correctly) lavish attention on their batteries, getting maximum performance and longevity. And for that audience, it makes sense to carefully adjust the voltage of the charging system while the batteries are not in use.

For the rest of us, it is enough that we put the batteries on a trickle-type charger when they are not being used, and monitor the water. The manufacturers of the chargers pre-set those units -- there is no way for the end user to alter them, as far as I know.

The "set it and forget it" approach is not perfect but it is adequate for most RVers. But if your life depends on your batteries, you have to take a more hands-on approach.

Then, of course, there are the "do nothing at all" people who just let their batteries sit there and rot and then recharge them before each camping trip. (I used to be one of those folks before I learned how expensive that method really is.) The "do nothings" are not even reading this thread.

But they will, eventually. 😉

All true. Another thing is that most chargers that drop to float after a time at 14.x do so before the battery is completely charged.

So if you disconnect after the charger says they are full, you miss the following time at 13.6 when the batts might get a little more charging towards true full.

I am not clear how long on float you need to be after a time at 14.x to finish the recharge so you can disconnect. It might not even be happening. There is SG lag, so the apparent improvement in SG next day after being on Float since the recharge might just be that the SG has caught up, not from more actual charging.

[BFL13]

No equalizing with SiO2. Same as AGMs but with regular AGMs you can do a "recondition". I have my C's 6s sitting with no wires and will recharge when they get down a bit in voltage (spot checking with multimeter, since the Trimetric monitor draws power so can't be left on the battery with no wires on battery)

I have the chassis battery floating on the converter though. There is a case where you must leave a charger on between trips since it has loads on it (maybe not so much with a 1991) Solar is off (array to controller side disconnected)

No idea how to do it with a Trickle start with house no wires on, and no converter, only an inverter/charger. PT will have to invent something.

The TC has the SiO2s. I pulled the Chev's Stud 1 fuse so the chassis batt and the SiO2s are not in parallel (I gather there is nothing wrong with that, but I still don't feel good about doing that--so I don't!)

If not using the truck for a while I put a maintainer charger on the truck battery. I was going to float the SiO2s, but now I want to do the no-wires between trips but they are hard to get at, so I will have to arrange a disconnect switch to the battery post where I can get at that. The converter can still do the 12v.

It might be a case with the SiO2s and the TC scenarios we have, that I might as well just float them and to heck with it. Be easier for sure.

[pianotuna]

BFL13 wrote:

pianotuna wrote:
Hi BFL13,

I've heard, for greatest longevity, long term storage for Li is 40 to 50% state of charge. Not what I want.

If you are on shore power for a while, you can do that if you have a converter to make your 12v, but not if you have an inverter/charger. (An inverter /charger must be connected to the battery to operate at all--it needs the 12v from the battery to run its own systems)

It might be worth the approx $130 for a converter to rig up and by-pass the inverter/charger for 120v too somehow. If all you have is a single 12v Walmart batt, then it would not be worth the bother probably. What if you have a $3,000 Li battery bank and are spending the winter on shore power at some resort?

Hi BFL13,

I did leave my oem converter in place but unplugged, so I have that covered.

I think it is possible with an inverter/charger to set the charge rate to zero. I may be wrong about that. I have successfully set the maximum charge rate to 111 amps, down from the "flat out" 129 amps design.

I normally leave the solar maintaining my batteries during storage periods.

I chose to have enough solar to equalize the battery bank.

[pianotuna]

BFL13 wrote:
My SiO2 modified AGM battery guide says do not leave it with a small load on it or it will sulphate slowly. So would any battery in an RV with the disconnect open but the LP alarm still on.--if you don't take the wires off the battery and have a small load like that on, should you be at 13.2 or is that "using" the RV so you should be at 13.6?

This is an important statement.

SiO2 are a special case.

I've always left the main battery disconnect off, but the inverter "on" (in the sense that it is connected to the battery bank) so that the Trik-L-Start will keep the chassis battery charged from solar.

Having it that way means that the chassis battery, when the key is turned to "on" is in parallel with the house bank.

My solar is set up to equalize once per month. When I go to SiO2 I had planned on turning that feature off. Perhaps that is wrong headed of me.