Do the slides run directly off the house battery, when hooked to shore power?
Like everything else , the load will operate from the higher voltage source. If the converter is at 13.6 and the battery at 12.7, then the slide will operate from the converter until its loaded voltage from running the slide and whatever else is on, gets to 12.7, then the battery will start to help out.
That means, with a battery connected and on shore power, both will share in the work at some stages of play, such as when the slide comes over the hump coming in where most power is required.
The converter may be able to do it all by itself if no battery is connected. Some rigs say you need the battery to run the slide, but that just means they have the slide motor pos and the converter pos on the battery pos terminal.
What they really mean is that the converter and slide motor pos must be connected to make a path, so with no battery, no path. Use a vice grips or other clamp to join the two wires with no battery, and you are back in business on converter only.
I have a Coachmen tt with two 6v batts. After 3 or 4 days boondocking, running the lights, water pump, heater fan, etc, the batts get pretty low. Should I get a roof mounted solar panel or would a portable trickle charge type panel that sits outside do the job? Thanks, Don
Not much info there (how low is "pretty low" in volts?), but all solutions mean don't get the solar trickle charger.
If you don't want to nail a panel or two on the roof then you could have a portable solar set-up instead with enough wattage that would do you some good. You might also like to have a Honda 2000w gen.
Usually, it is a good plan to have some solar plus the Honda 2000w so you can keep on camping off grid whatever the weatherman delivers.
Can't suggest much without knowing more about the whole situation--how long off-grid is wanted?, can you carry more batteries?, etc.
AFAIK, the problem occurs where the one battery is in worse enough shape than the other. That could be with same type or different types. If they are different types, but all in good shape then nothing bad happens supposedly.
My test here is to see if the two same type batts are different enough in "shape" to matter, using Mex's test for that.
I should do this same thing with my four 6s in series parallel, now all on a float as one big 12.
I found the test where I had done this before to check self-discharge rates on my 27DCs I had back then. Could be used for comparison with these used T-1275s, to help verify the results in a few days:
Posted: 11/29/10 09:21am Link | Print | Notify Moderator
So three "identical" 27s banked for a month and floated at 13.4v did ok, SG held up. Did a cycle down to 75% anyway (not needed)and recharged to 16+ volts recovery method, now trying other way. Separated batteries and let sit. Only 10 days in but interesting results so far.
Voltages by batteries No 1,2,3 where 1 and 3 are from 5/08 and 2 is from 3/10. (EDIT Perhaps I had that mixed up and the last was the newer battery)
Was 13ish volts next day after removing charge to 16+ so start with day after that by Day number:
1- 12.86, 12.87, 12.89
2- 12.83, 12.82, 12.88
3- 12.80, 12.78, 12.86
4- 12.79, 12.76, 12.85
5- 12.78, 12.74, 12.85
6- 12.78, 12.74, 12.84
7- 12.78, 12.74, 12.84
8- 12.77, 12.73, 12.83
9- 12.77, 12.73, 12.83
14- 12.76, 12.72, 12.82
20- 12.74, 12.71, 12.80
All SGS still ok, no sign of lower than when started. (1.275ish--slight variations among cells--the SG of the higher voltage battery 3 is same as the others)
It's not very exciting, but at least it is something to do with batteries! :) Mex says the low cell sucks from the others. I am waiting to hear how come all the 1.275 cells in Battery B are sucking from that one 1.300 cell, but its SG keeps getting higher!
I'll do another report on Monday and that should settle this whole crazy T-1275 saga one way or another. (So far they seem at least as good as any of the pairs of 6s I have)
After one day, voltages have dropped to 12.93 and 12.90, maintaining that 0.03v difference while losing some surface charge.
Mex says that a tenth of a volt is significant for this difference after four or five days, so unless this difference becomes greater than 0.03v in the next few days, it must be "insignificant?"
Decided to try out Mex's tests on my two "previously enjoyed" T-1275s where I have noted before that one seems to be in better shape than the other based on higher average SGs, although each has variations among its cells for SG.
This should tell whether they can be left in parallel safely for a long term float on one charger, or need individual floating with two chargers.
Here's a tip to understand the reality of same type of battery has different chemical attributes according to its state of charge or age.
Fully charge all batteries
Wait 4 or 5 days, then measure the voltage potential of each battery
Take a hydrometer reading then reconcile it to voltage of each battery.
A tenth of a volt is significant, two tenths is worrysome when you are trying to balance batteries.
To amplify the test, apply 14.8 volts after fully charging the batteries. Note that the cells with the lowest gravity and lowest initial voltage boil first.
Cells that droop after charging, actually CONSUME power. Roaches check in but they don't check out, time. The worse the cell the hungrier they get. Some are the eqvt of a 20 watt load on the other cells in the bank.
So to get started, where they have been on individual floats for a while at different voltages (13.5, 13.4) been watered a little in some cells after last overcharge(affecting SGs), I put them in parallel, gave them a quick overcharge at 15v for an hour, and got , while still being charged, 14.94v each.
I watched as they started to show bubbles, but did not see anything obvious which cells started to bubble first. Not boiling anyway, just small bubbles coming up in strings.
So next step is disconnect everything and let them sit for four or five days and check voltages and SGs. Meanwhile, after an hour I took an initial set as a benchmark sort of with surface charge still present:
Battery A (the good one?) 13.43v
Battery B (the also ran) 13.40v
Battery A 1.275, 75, 70, 90, 75, 75
Battery B 75, 75, 1.300, 75, 75, 75
So now must wait a few days and see what happens.
Mex says a low cell draws from the others. Battery A has that lower cell at 70 there, which is always the low cell when taking SGs. Battery B has that crazy high SG cell, which is always high like that.
Not a clue what that might mean, can't fix it, it just is!
If Mex is reading, is this a proper start? Do I check daily or just wait four days? (I doubt all the surface charge will be gone in only four or five days, but we'll see)
This shows the essentials although it is for the smaller 130w size panel. It all lies at the back of the roof bungeed to the cargo railing when going down the road, then I can undo it and prop it up somewhere like here against the air cond shroud. I learned to use a rubber mat under where it pokes into the roof.
I then used the same tray for my contraption last year, photos in this thread.
This past summer with a new contraption, I did not have a tray for the other panels in that, and I got that flexing when strapping them down onto the contraption, so lesson learned. Next contraption coming up for the new big 24v panel is to make a tray for it and put that tray into the new contraption.
If you can avoid a wire nightmare there is nothing wrong with your idea
That does look a lot like my battery compartment!
Based on this reply and the others in the thread, I have decided, as with many other things, it's ok if I only do it a little. :)
Quoting Mex "It's when the charging ceases that the problems arise." I get charge them together and then disconnect them from one another after charged!!!!
Yes but that isn't much use when you are still camping and want them still banked. Ok at home on a float with more than one float charger.
I would like to clarify what it means for camping. I will do the float separately, that's easy. Is there a time factor for how many times camping you can get away with it for instance?
OK so I continue to have them separated for recoveries and floating at home.
But I am just not seeing where having them separate at home, then going camping (no solar) for four days with them banked doing say three 50-90s, then returning home and separating them, is going to end up with one set eating the other.
I would likely do that three times by mid-April, then it is on to the seasonal off-grid site with solar.
I always have a "less than optimal" battery set-up. Seems like a case of "perfection being the enemy of good enough?"
Our trailer's manual comes with several schematics which are very helpful in seeing how it all works, but you don't get a wiring layout for your actual trailer, so it is a complete mystery what routes the wires take behind the walls and in the ceiling.
Here is one of their drawings (which I have scribbled on) from the manual as an example:
I agree they flex a lot anyway, and I don't like it when they do. I doubt the extra holes matter much.
What I do is run two bars across the back of the panel, which helps stiffen the panel. I then have a wooden tray that takes all the strain of being supported, tilted, etc, with the panel just lying in the tray, strapped down cross bars to tray.
It has to do with small differences in resistance that end up causing much larger imbalances. The terrible thing is that jars on the "ends" of chains never ever get fully charged. And you, of all folks, know exactly where lack of 100% charging leads.
None of them gets to 100% while camping, even on solar. I don't care if some get to 98% and others only to 96% that day. They all get to 100% individually for sure when I do their recovery sessions at home.
When just camping no solar and doing 50-90s the 90% itself is not very exact for the bank, and who cares if each battery is a little different in SOC when I stop the gen? What I do care about is getting some Peukert on the way back down to 50% for the extra AH.
What do I get as a benefit in return for losing that Peukert value?
Seems like being penny wise and pound foolish to me, but "everybody says" do it right or else bad things happen. I am asking what those bad things might be and just how bad they are, so I can do a risk assessment that applies to how I do things.
For the time I would be camping with them banked, they would never get to 100% anyway. They only get to 100% when taken there separately at home (or if I ever did the split bank trick with solar)
So that leaves keeping them on Float at home as the only time they might be prevented from staying at 100% if connected mixed after being "recovered", from what PT mentions. If they are all at 13.4v will one set eat the other?
I am trying to understand if there is some sort of evil interaction current eddying nasty business that goes on that harms them during normal discharges and recharges and on Float. I don't care if one set only gets to 97% while the other set gets to 98% on a day's worth of solar. That gets fixed when doing the 100% recovery they all get later separately.
The available amp hours from a battery is dependent on how fast you withdraw them. You will get more total amp hours from the three batteries if they are connected and sharing the load.
Right, but the question is does it matter if they share from different locations? Obviously there is the usual argument for balanced banking, but even with unbalanced, eventually the 'downstream' batteries catch up. Over time one gets worked harder etc etc.
What I am asking in particular is whether, when unbalanced and accepting that, does even matter if you draw and discharge from the same set of battery posts as long as you get 12v from wherever you hook up to with whichever thing you are connecting? Why do they all have to go on the same set of battery posts (or do they have to?)
I was proposing to bank them all together while camping off grid, sometimes for weeks at a time, where they would be discharging and charging together.
They would get solar and converter charging as required, never getting to 100% and not going below 50% either, then going home and separating them to get ("recover") each to 100% individually.
Then they would go on a Float together or separately (I have several float chargers) till the next camping session.
Mex said that was bad. Has he changed his story? Did I not understand the Oracle the first time? This really matters for how I set up the trailer with wiring etc.
I can't remember (if I ever knew) why you are supposed to have the loads and the chargers all on the same battery posts in a bank.
Say you have three 12s in parallel. What's wrong with having an inverter wired to one of the 12s, the converter to another of the 12s, and a second inverter on the third 12? Also you might have one solar controller on any one of those three 12s and another controller on a different 12.
Ideally everything should be balanced and you put all your goodies "across" the whole bank. But what if you have short wires and that is just not possible or convenient? What terrible things happen if you "tap" in or from any place you can get at?