Charging a Battery Bank

[RobWNY]

I am planning on upgrading my batteries to 4 6v batteries wired in series and parallel to have a 12v system with plenty of Amp Hours. There is a ton of information on how to wire things up but nothing on how to charge them both to top them off while boondocking and long term during the winter month's. Do I have to disconnect the parallel connection and charge them as 2 separate 12v banks (2 banks of 2 6v in series) or unhook everything and charge as 4 independent batteries or is there a charger that can charge all 4 batteries without disconnecting any of the battery connections? Also, what would be a good battery charger to get to accomplish the charging? I have an inverter generator and I'm looking at portable solar panels in the future to use while camping and will be storing the batteries in my basement during the winter month's. Thanks for your input.

[Joel_T]

I reinstalled the 75A when I realized it would function as an adjustable which is all I wanted anyway. After the failed 2hr try as a 3 stage and then plugging in the WFCO to "shore" overnight with no SG change, I tried the 75A charger set fixed at 14.7 using the 1800w generator. For whatever reason the batts didn't even register it was there, which probably means I've got something screwed up....just dunno what. Using shore power I hooked the cabled charger set at 40a up and voltage jumped to 16.1v and the chargers amp meter claimed 20a....my clamp-on is busted. SOC went from 0% to 100% ish SOC in 2 hours. That's great but faster than what I hear is reasonable. Here's a pic of my wiring. Controller, Charger, Inverters have a foot or so of #4 to terminals and then 5' of 2/0 to the batteries.

[BFL13]

Good news that you were able to recover the batteries according to SG. Of course you still have to prove them by loading them and seeing if they stand up to that, but fingers crossed.

For the battery gurus-- I am unclear how you can use equalize level voltages on the batts when they are not fully charged. In this case they were near dead flat. So what is that all about that you can only equalize a full battery?

It appears the near dead batts needed the high voltage to kick start them into recovering their SG, and a "gentle" approach did not work.
I don't see this as a case where a "smart charger" needs the batts to have at least some voltage before it will even operate. The converters did operate, but at a lower voltage level where nothing happened.

There are "unknowns" why the two converters did not operate but the portable charger did. We know nothing about the rig's set-up wiring etc and whether it is valid. We don't know if the installed (how?) PM 75 set to 14.8 was no use in getting the near dead batts going, or even if that was tried out-- only that the WFCO at 13.6 was unable to get them going. Last we heard the PM was removed from its installation, so when did it get to try this?

Anyway, back to one thing, which is testing the PM for 75 amps now there is enough battery to power the 1500w inverter with an 80 DC amp draw, eg, a kettle. That would also be a battery test before applying the PM 75, to see if they are ok now.

The poor OP is going through a lot of difficulties here, but good for him keeping his cool and us up to date--we are learning useful things here. 🙂

[Joel_T]

I followed your advice landyacht and after the 2nd hour, 4 cells at 1.275+SG and 2 at 1.265+SG. (A midlife 100% SOC I guess) I'll repeat to work on the 2 lagging cells but does it make sense that using a portable cabled charger it only took 2 hours to get there from 11.5v and 1.120SG which is basically zero SOC? Neither hard wired chargers I have even made a small dent in charging after 2 hours.

[MEXICOWANDERER]

16 volts connected is plenty high enough. Remember the actual equalization formula is to attain 16.0 volts with a 5% of amp hour capacity amperage limitation. Example 11 amperes at 16.0 volts for series 6 cells of GC220 battery.

How long the equalized battery stays equalized separates good battery brands from the pretenders. If there is anything on the face of the earth more revealing about the quality of a cyclable battery I am not aware of it.

From experience, I know a majority of GC owners have no idea that their 220 amp hour capacity rating is actually a lot lower due to sulfated plates. It's only when capacity drops even further to the point of in-your-face weakness that the RVer has the light bulb glow above his head. Of course the proper diagnostic use of an amp hour meter will show any loss of capacity. A hydrometer dip screams any chemical malfunction.

I have had to keep scumbag brand GC's at 16 volts overnight to see gains in electrolyte density. An overwhelming majority of these almost new batteries resumed uneven gravity readings almost immediately.

[landyacht318]

measuring unloaded voltage of a charger is not indicative of the max voltage it will allow when hooked to a battery.

Leave charger on until battery voltage climbs into mid 14's. Keep checking specific gravity accounting for the rise in electrolyte temperature.

If charger stops and flashes green light, Load batteries until voltage falls to 12.6v or below, then restart charge, then remove loads.

Lather rinse repeat until Specific gracity no longer rises or reaches 1.275+ on all cells. It might not ever do this unless voltage is allowed to go as high as 16.2v.

When that occurs ( 1.275+ SG) the battery will be indeed fully charged to its maximum remaining potential capacity, which is likely far different from the AS NEW capacity.

Massaging Sg back to the maximum is like a reset to 'as good as possible' for that battery at that level of condition. The battery should be easier and faster to fully recharge after the massage, but perhaps not.

Those of us who got sick of trying to outsmart the 'smart' 3, 4 or 22 stage chargers, find twisting a dial to a set voltage to be much easier than manipulating a smart charger with encantations and blood sacrifices to chango

[Joel_T]

After 60 minutes voltage 15.8. Five cells near 1.270SG with one staying at 1.250SG

[Joel_T]

landyacht318 wrote:
Withuot being able to bring and hold the bateries to a proper absorption voltage for a proper duration and possibly perform an EQ charge afterwards, there will likley be no improvement to the battery condition, and just a lesson in futility.

Getting a charging source to do what is needed, seems to be impossible when there is anything 'smart' and 'automatic' involved, and the WFCO is a drooling knuckledragger that tries to be smart and automatic.

Get the batteries to 14.8v, hold them there until amps taper to ~1% of capacity. Then slowly Raise voltage to 16.2v, hold then there until specific gravity no longer rises or amps start increasing along with a fast rising battery temperature.


Adjustable voltage power supplies might be manual chargers, requiring a human to decide what voltage to allow and for how long, but at least they can actually fully recharge a battery and not require sacrifices to chango while hopping backwards of one foot counterclockwise chanting 'just fine; just fine, everything will be just fine'

Hooked cables to the pair of 6v batts using my old Centeck set on 40amps....can't adjust anything. Only accepting 20a...I think. No reading from Trimetric. This charger has the voltage steady at 16.1v instead of up till now only 13.6v. So far after 30 minutes the bubbling fluids read 1.250SG uniformly over the 6 cells. I'll just keep an eye on SG and temperature?

[landyacht318]

Withuot being able to bring and hold the bateries to a proper absorption voltage for a proper duration and possibly perform an EQ charge afterwards, there will likley be no improvement to the battery condition, and just a lesson in futility.

Getting a charging source to do what is needed, seems to be impossible when there is anything 'smart' and 'automatic' involved, and the WFCO is a drooling knuckledragger that tries to be smart and automatic.

Get the batteries to 14.8v, hold them there until amps taper to ~1% of capacity. Then slowly Raise voltage to 16.2v, hold then there until specific gravity no longer rises or amps start increasing along with a fast rising battery temperature.


Adjustable voltage power supplies might be manual chargers, requiring a human to decide what voltage to allow and for how long, but at least they can actually fully recharge a battery and not require sacrifices to chango while hopping backwards of one foot counterclockwise chanting 'just fine; just fine, everything will be just fine'

[BFL13]

Maybe try tipping them on their sides for ten minutes and then go upright again. That worked with my old 27s to get the SG up more.

Any voltage you have now might be coming just from the little acid they have, all near the bottom, with water on top. Since the charger isn't getting things going, maybe tipping to mix what is there will be something it can grab to and improve?

Note the highly scientific battery expertise there. Or first kill a chicken and let seven drops of fresh chicken blood fall on the positive posts of each battery--not the neg posts, or it won't work.

Did I mention we need a battery guru or two to help out here? 😞

[Joel_T]

Phantom loads are all that should be distracting charge amps. I'll check though. These batts are about 3 years old. Only a third of the time, or maybe half, used dry camping down to 50%...not even that much very often. The rest is plugged in or solar....all winter....except this winter I've monkeyed around dropping them to what I believed to be 50%...more than once. Don't check SG that often so while it would greatly surprise me, that 50% SOC could have been near zero....eeshhh. Also will re check Trimetric parameters. I noticed Crown said to limit dropping below 1.125SG???? I suppose I "limited" that but how do you drop below zero?

[BFL13]

A stray thought---A charger will supply other loads first, then anything left over goes to battery charging.

Any chance the WFCO is supplying amps to something else in the rig and that's why you aren't getting any amps to the battery bank?

[MEXICOWANDERER]

Just a fast note...

A Megawatt with a removed pot and pot terminals connected 0.0 ohms will deliver 16.28 volts open circuit.

[BFL13]

Only time I have with this, the guy's 6s were down near flat, but my Vector charger (does 14.6) was able to start (so the batts had at least 4 volts or the Vector would not have started--if that happens use jumper cables first, then switch to the charger)

Amps began very low and slowly rose and voltage slowly rose over the first couple hours. Then things got normal and amps started to taper again as normal. I think you can get away with doing that at least once and the batts will recover, like leaving the lights on in your car.

I don't know what the correct answer is here, IMO your amps should be rising slowly. T2R suggested not too much voltage, but how much is that? Time for a battery guru to help out. Maybe start a new thread on this to catch somebody who knows? Probably not many people following this thread anymore.

[Joel_T]

Red31 those specs make more sense. Don't understand the value of or why the other specs.

BFL13 The Crown specs I have are several years old. (Can't find newer other than Crowns generic that Red31 found.) I've read that some mfg's are increasing their Vabs from the "old" typical 14.4 to 14.8 or in the 15s. I'd probably ignore the 14.22v suggestion.

My batts SG is still 1.125- and the WFCO is trickle charging only at 13.6v with 1a in. At this rate 100% SOC is 2 weeks out or maybe never at this point. Might later try 14.8 from the PowerMax.

[BFL13]

https://www.solar-electric.com/lib/wind-sun/Crown-CR-260-specs.pdf

Looks like they want Vabs to be 14.22 (2.37) and fully discharged SG is 1.124.

But then they say do a "finish" near the end of the absorption stage to 2.65 = 15.9 So you will be twiddling the pot during a recharge, although it will max at 15.5.

Good luck with that for the average RVer and his typical converter 😞
Looks like PowerMax is right to have the adjustable voltage feature on all their new converters coming out (LK model) that goes to 15.5, although even that is too low for some battery specs it seems.

I suppose the other converter brands will have to respond to all these higher battery voltages one of these days. I can't see how the fixed three-stage converter that is no good for anything can last in this situation. Going to make it hard for the average RVer who just wants to push a button and go have a beer!