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 > Battery Question, Again

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Katdaddy

Petal, MS USA

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Joined: 08/25/2003

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Posted: 07/11/18 09:17am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

Your batteries aren't too bad, but need to be fully charged.

When you get the LK use that to bring them up to 16v and let them stay there while you spot check the SG for when it stops rising. Could take a few hours and you have to be there so plan your time.

*Read up on how to do an equalize first!!!* You will get acid spitting and holes in your clothes so wear old clothes that don't matter. Glasses or goggles for the eyes. etc.

Read up on an equalizing charge. It said to monitor amps while charging. I have searched the web with no success as to how to do that??? Showing my ignorance once again.


Little by little, one travels far - J.R.R. Tolkien
There ain't no surer way to find out whether you like people or hate them than to travel with them. - Mark Twain

BFL13

Victoria, BC

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Posted: 07/11/18 09:47am Link  |  Quote  |  Print  |  Notify Moderator

Katdaddy wrote:

BFL13 wrote:

Your batteries aren't too bad, but need to be fully charged.

When you get the LK use that to bring them up to 16v and let them stay there while you spot check the SG for when it stops rising. Could take a few hours and you have to be there so plan your time.

*Read up on how to do an equalize first!!!* You will get acid spitting and holes in your clothes so wear old clothes that don't matter. Glasses or goggles for the eyes. etc.

Read up on an equalizing charge. It said to monitor amps while charging. I have searched the web with no success as to how to do that??? Showing my ignorance once again.


Ignore that about the amps for Flooded batts. Amps is for AGMs since you can't see their SGs.

Are you using the LK as a portable with cut off jumper cables (at least #6 copper for a 60 amper, #4 cu for higher amps) in it and keeping the installed converter for when on shore power? Like this (which you can do with any brand of deckmount converter to make it a portable charger)

https://www.boatandrvaccessories.com/products/powermax-pmbc-55-charger


1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI

Katdaddy

Petal, MS USA

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Posted: 07/11/18 10:13am Link  |  Quote  |  Print  |  Notify Moderator

Thanks for that. Yes, using the LK as a charger. That pot for adjusting the voltage is VERY sensitive. I like finally having this capability. Thanks again for the suggestion.

BFL13

Victoria, BC

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Posted: 07/11/18 10:39am Link  |  Quote  |  Print  |  Notify Moderator

Katdaddy wrote:

Thanks for that. Yes, using the LK as a charger. That pot for adjusting the voltage is VERY sensitive. I like finally having this capability. Thanks again for the suggestion.


Luckily it doesn't matter if you are off by a bit to the second decimal place, but it does matter to the first. EG, as Mex has said, there is a big difference in how the battery acts at 15.7v and at 16v. That 0.3v is huge for getting some batteries to full SG where 16v does it and 15.7 does not. Some batts get there ok at 15.7.

Don't forget to set the voltage on the LK before connecting to the battery or else you will get a wrong reading. When you are charging and you want to change the voltage you can tweak it but you won't know exactly what you tweaked it to until later when the battery gets there.

It all works better once you do it a few times. "On-the-job training"!

Katdaddy

Petal, MS USA

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Posted: 07/11/18 10:41am Link  |  Quote  |  Print  |  Notify Moderator

MEXICOWANDERER wrote:



There WILL BE one or two cells that will be slightly more reluctant to recover to 1.275. You can find these by checking all cells right after shutting off the charger. Mark them, these are your go-to cells when you believe a hydrometer test is in order down the road. No sense in stabbing 12 cells when there are just one or two delinquents. Put the batteries with the weak sister cells in the most accessible location for dipping.


Thanks for this tidbit. It answered one of my questions before I even had the chance to ask.

* This post was edited 07/11/18 11:59am by Katdaddy *

Katdaddy

Petal, MS USA

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Posted: 07/11/18 08:33pm Link  |  Quote  |  Print  |  Notify Moderator

MEXICOWANDERER wrote:

USUALLY 12 cells with a uniform 1.260 gravity are not badly sulfated

I would perform a current limited TOP CHARGE on these batteries.
With current limiting here is some help.

Stage one. Four hours at 14.4 volts after which are all 12 cells bubbling slightly? Good. Disconnect. Let set for 2 hours then recheck gravity.

Some cells not bubbling?

Increase voltage to 14.8 and repeat top charge but only for 2 hours
Are the reluctant cells now bubbling? Same drill. rest 2 hours than recheck gravity.

You have a weak sister cell? One that resisted 14.8 volts? It will need to be amperage limited to 11-amps at an 8-volt top limit. Full equalization then you need to keep an eye on it. Starting at 1.260 gravity this would be quite unusual.

There WILL BE one or two cells that will be slightly more reluctant to recover to 1.275. You can find these by checking all cells right after shutting off the charger. Mark them, these are your go-to cells when you believe a hydrometer test is in order down the road. No sense in stabbing 12 cells when there are just one or two delinquents. Put the batteries with the weak sister cells in the most accessible location for dipping.

Remember the chemistry change continues after the charging current is removed. I've found two hours to be a rational wait.


OK, did this. Voltage reading after 2 hours 12.71, SG on all cells at least 12.75 with a couple at 12.80. Am I good now or do I still need to do an equalizing charge?

BFL13

Victoria, BC

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Posted: 07/11/18 08:49pm Link  |  Quote  |  Print  |  Notify Moderator

You only ever do an equalizing charge after getting them to full. You are close enough to that to now do a real equalize at 16v and get them desulphated as much as they can be.

It will take a few hours, even half a day--"depends"

It will take more than just two hours for sure with those, with their history . Eight hours is not unusual.

Your battery spec data sheet will say what the resting full voltage and SG should be at 77F. do the equalize, let them rest for a day and check the SG--it will be higher next day when they cool down after the overcharge. (SG is higher with cooler electrolyte--more dense)

BTW--SG is decimal different from voltage. Eg SG 1.275/Voltage 12.75

Katdaddy

Petal, MS USA

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Posted: 07/11/18 09:12pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks. I did know that about the SG, just can't type. LOL

MEXICOWANDERER

las peƱas, michoacan, mexico

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Posted: 07/11/18 10:24pm Link  |  Quote  |  Print  |  Notify Moderator

It would not be considered unusual to gain 5-6% in usable amp hour capacity by gaining from 1.275 to 1.280 if the original specific gravity was 1.280 (not uncommon).

Not always a positive point but the stronger the electrolyte, the more reactive the plates.

The ease or difficulty in which a battery reverts to full specific gravity is what I harp about.

Mark the weak sister cells. And later on deal with them first.

pianotuna

Regina, SK, Canada

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Posted: 07/11/18 10:39pm Link  |  Quote  |  Print  |  Notify Moderator

KatDaddy,

If you do equalize at 16 volts be certain to disconnect the battery bank from the RV. Computer boards are not rated to tolerate 16 volts. And are expensive to replace.


Regards, Don
Full Time in a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

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