Floating vs Storage Voltage Question

BFL13,

The best is to have the voltage vary with the temperature of the battery. That feature is available on most good solar charge controllers, and also on high quality inverter/chargers such as Victron.

13.2 works well when combined with the 15 minute boost charge at 14.6v every 20 hours.
Otherwise storage and float are the same thing as far as I am concerned.

Although if the battery has been floating in storage for an extended period I do find that first cycle is a bit weak and seems to restore on the first charge cycle. Might be virtually the same to let them just rest disconnected for storage.

Sure, but 13.2v at 85F is like 13.7 at 50F so 13.2 is way low for 50F. The question is why store (float?) at 13.2 when the spec is for 13.6 at 77F

Randy still has this float voltage table-scroll down, eg. I think there are better tables but gives the idea sort of.

http://www.bestconverter.com/Parallax-Paramode-with-TempAssure_c_104.html

US battery says float 13.02 at 80F

Nothing wrong with following the manufacturer's specification.

https://www.usbattery.com/technical-info/charging-instructions/

Lots of battery myths would be corrected if RVers would read the Trojan Users Guide.

Interesting about that US Battery float voltage for flooded at 2.17 per cell. Their AGM is 2.23

Meanwhile Trojan is at 2.25 for both types, and East Penn (Deka) is at 2.24-2.26 for AGM and 2.30-2.35 (13.8-14.10v) for flooded.

Seems they all agree on AGMs but are all over the map for flooded batts.

We have had many posts about how 13.8 is too high and how you have to keep adding water at that voltage, saying 13.2 is required to stop that. But the battery specs are as above for 77F.

EDIT--Note that Trojan says not to float floodeds if they are used more than once a week, but say for AGMs it is if they are used more than once a month.

time2roll wrote:
13.2 works well when combined with the 15 minute boost charge at 14.6v every 20 hours.
Otherwise storage and float are the same thing as far as I am concerned.

My original house batteries lasted 9 years with a PD-9180+wizard doing the above pattern
Their replacement went to Insurance Auto Auction with the rest of the Rig after the Semi clipped it. 6 years later.

wa8yxm wrote:

time2roll wrote:
13.2 works well when combined with the 15 minute boost charge at 14.6v every 20 hours.
Otherwise storage and float are the same thing as far as I am concerned.

My original house batteries lasted 9 years with a PD-9180+wizard doing the above pattern

X2!

9 yrs and could have gone a couple of more but wanted to make sure my home fridge wasn't going to run me out of battery.. And I am using a PD9160 with external Charge Wizard.

13.2V is what I have found maximizes battery life when not being used (AKA "Storage") combined with the PDs Charge wizard giving a short 14.6V bump every 20 hrs during storage.

13.8V in storage is way too much no matter what the temperature is, it WILL boil the battery to death if allowed for too long of time.

13.8V is the target charging voltage of a older automobile alternator/charging system from the 1980s and older.

Old linear converters had a fixed 13.6V and they boiled batteries to death. My first TT had a linear converter and it ate batteries for breakfast, lunch and diner, boiled quite a few batteries before I realized that I HAD to disconnect batteries while being stored, otherwise suffer the cost of another replacement.

And, I will say this, a few of the portable devices I have built for myself which use Gel and AGMs, well I set my charger voltage to 13.2V and they reward me with very long life.. One device with a gel battery is going on 15 yrs, still works although doesn't have the capacity it had new.

If you REALLY want to charge harder, then go with a fixed 13.8V supply and put it on a 24hr timer, give it 4-6 hrs of charge per day for storage.. That is what my local Ham club did for yrs for their backup emergency batteries.. Worked pretty well but with the advent of multistage charging it isn't worth the hassle to me.

Seems that a lot of folks here fuss and obsess way to much on batteries, folks like PD have figured out on how to build a converter which can maximize the life of your batteries without much intervention or fuss of the user.

Sure there are more "advanced" converters with temp comp and even different charge curves for different types of batteries but in reality that extra fuss might net you one more month of life, not years like folks think it will.

Ask Mex, I know he has built all kinds of charging schemes with all kinds of required human intervention.. Might give you a bit longer battery life, but at the cost of your own personal time which you can never get back.

Batteries you can replace, your own personal time you never can replace..

Best advice I can give is, batteries are a "consumable", each time you cycle it, you consume part of its life.

That harder you consume it, the faster you shorten it's life.

Shallow discharge followed by a quick recharge will net you with the longest life.

Over or under charge, will destroy a battery just as fast a deep discharge or allowing to sit partially discharged.

When I go to bed I never feel like I have lost a damned thing. I avoid hundred dollar trips for fuel and settling for 70% storage capacity because of I'll maintenance. To me there is nothing worse than destruction of plans because of early battery death. A Wal-Mart battery death cost me a hundred dollars out-of-pocket for surprise hotel room and restaurant meals. Figure it out folks. Spend an extra twenty bucks on a better battery or a hundred in penalty. I haven't got enough money to be cheap.

Still does not explain what is meant by "floating voltage" in the battery specs.

PD ISTR has the feature that if you are using the RV it will be at 13.6 "normal" and after a period of no (or is it low--how low?) "activity" it drops to 13.2v. If you go in the Rv and turn on a light or two it goes back to 13.6.

All those on long term shore power living in their RVs would be at 13.6 and their batteries are not disconnected.

If you keep your RV at home plugged in between trips what are you supposed to do? Is that "storage"? I go in ours a lot to do upgrades or whatever. I could disconnect the batts and be on converter but I have not been doing that.

According to Trojan, with flooded and once home and recharged, I should not leave them on Float if using the RV next week, but I should if not using it next week. If I have AGMs then I should not go on a float once they are recharged unless the next trip is more than a month later.

On solar full-time off grid, the controller will drop to 13.6 after it stays at 14.x for a time. You don't want to be at 14.x overly long, but you do want to be there till the batts are full.

I tried dropping to 13.2 in the afternoon after the batts were full and it was unsat. Got minus amps showing and voltage 13.1. RV was still being used. Turned it back to 13.6 and no problem. I think that is why they have 13.6 as "normal"

So what is "standby use" where they want you to do "float charging"?
Is there a draw on a standby battery from what it is connected to in a UPS scenario? Otherwise, why choose the higher float voltage instead of the storage voltage?

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?

The various battery guides are clear on what to do with a disconnected battery, but are not clear at all IMO what an RVer should do between trips. Even winter storage is confusing where some storage yards have power and some don't and with those some guys use solar "maintenance charging"

So that's another one--"maintenance" to go with "storage" and "floating"