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Open Roads Forum  >  Tech Issues

 > Proper procedure for checking battery sg

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Ezbagr

Illinois

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Posted: 10/12/11 11:45am Link  |  Print  |  Notify Moderator

After our boondocking adventure last week and having problems with the
4 6 volt battery bank {voltage would drop fairly quickly with very little amp draw from the bank} I am going to try and figure out what is going on with my battery bank. The fifth wheel has been hooked to shore power for 3 days and the pd4260 has been charging the batteries the entire time. What would the proper procedure be to check the sg in all
4 batteries?

BFL13

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Posted: 10/12/11 12:08pm Link  |  Print  |  Notify Moderator

Just dunk in the hydrometer at first and see what it says. Do all the cells in all batteries looking for ones that are out of whack with the others. Probably/possibly they will all be close but all a bit low.

For best readings, when you have a moment read an article on hydrometerology for how to take readings, and play with it some till you get used to it and get consistent readings. You don't need to be highly skilled


Mostly you are looking to see if the SG level is as high as when you first got the batteries and charged them up. If they are not taking any more amps in (ie are full) but SG is a bit less than when new, then you should try some desulfating to see if you can get the SG back up to where it belongs. That can take a week or two, so this is not a thing where you find out right away how things stand.


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mena661

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Posted: 10/12/11 12:08pm Link  |  Print  |  Notify Moderator

You need a hydrometer. It's like a turkey baster. You suck the acid into the tube using the squeeze bulb, read the SG, then squirt the acid back into the battery. Take a reading on all cells. SOC is dependent on the temperature but some of us have spreadsheets that help us out with that. Post your SG readings here and we'll help you out.


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Ezbagr

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Posted: 10/12/11 12:37pm Link  |  Print  |  Notify Moderator

Do I need to disconnect them from the pd9260 for a period of time?

mena661

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Posted: 10/12/11 12:49pm Link  |  Print  |  Notify Moderator

Ezbagr wrote:

Do I need to disconnect them from the pd9260 for a period of time?
I usually disconnect for a couple of hrs or so after the batts have been on float. I have let them rest for 8 hrs or so before. That amount of time is probably not necessary though.

trickyvic3

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Posted: 10/12/11 12:53pm Link  |  Print  |  Notify Moderator

When I check mine I unplug from shore power and turn on something that will draw power from the house batterys for a minute or two. This will remove any surface charge.

Then you should get a proper reading using a hydrometer.

BFL13

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Posted: 10/12/11 02:25pm Link  |  Print  |  Notify Moderator

When you do an overcharge/equalize the procedure is to stop the charge when SG stops rising. So of course that means you are still charging while taking readings.

There is SG lag which means your SG won't get to max until right at the end of the overcharge. It does take an overcharge to reach max SG too.

At the moment your converter goes from absorption to float you are around 97% SOC and SG will not be at its highest. You need to keep going into an overcharge and not go into float.

You can get a slightly better SG reading later after the overcharge is over when electrolyte "cools" ( fluid more dense,bobber rides higher) Same with temperature adjusted readings charts- unless in extemes of hot or cold temps--not worth the bother.

Matt_Colie

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Posted: 10/12/11 03:55pm Link  |  Print  |  Notify Moderator

Ezbagr,
First off, dump the hydrometer and get a refractometer (for reference look at EB item 370476704692). These do not require temperature correction and leave little open to subjective interpretation. (Rinse it carefully when you are done so you don't end up with little holes in everything.)

Now go looking for a weak cell.

Your PD9260 is about as good a converter/charger as you can get. But no matter what you do, Lead Acid(LA) batteries do not like to be charged in parallel. Every time you have had a deep discharge of the house bank, split them and let the PD bring them back to full density separately. Then put them back together.

This alone may solve your problem. Or, you may find the weak cell.

Matt


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renoman69

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Posted: 10/12/11 05:45pm Link  |  Print  |  Notify Moderator

Wow.... I have read about a bizillion posts on battery charging and have never read that LA batteries do not like to be charged in parallel. Anybody else have any thoughts on this?


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BFL13

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Posted: 10/12/11 06:09pm Link  |  Print  |  Notify Moderator

I think it is ok to charge them in parallel to a certain point, but to reach 100% in each battery IMO you have to do the overcharge to each one individually (6s by pair), especially if they are of different ages and types, like my 27s and 6s combo.

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