Battery Question, Again

[Katdaddy]

Folks I come to you, hat in hand again to try to help me understand what is going on with my batteries. I have four 6 volt batteries in my camper. I bought new batteries in September last year. I brought them home and hooked them up to a dedicated charger to bring them up to full charge. We took a trip to Cades Cove in October. Last time I bought new batteries I stupidly left them on a float charge for an extended period and lost capacity. This time I have run then through a cycle ever month to six weeks. We took another trip to the Cove last month and when I checked the batteries they were only at 80%. I have a Boondocker converter/charger and I have checked it when I first plug back in and it is reading 14.15 volts.The batteries are dated 7/17. Any ideas or suggestions are most welcome.

[Katdaddy]

red31 wrote:
http://www.eastpennmanufacturing.com/wp-content/uploads/Renewable-Energy-Charging-Parameters-1913.pd...

Thank you. For whatever reason I have completely missed this.

[red31]

http://www.eastpennmanufacturing.com/wp-content/uploads/Renewable-Energy-Charging-Parameters-1913.pd...

[Katdaddy]

red31 wrote:

Katdaddy wrote:
I cannot find a spec sheet on these batteries

is there any reason you have not shared the brand/size etc of battery?

going on a month, is it some sort of secret?

My apologies. I did not realize that I had not named them. They are Duracell GC2 batteries from Sam's Club. I have four of them, dated 5/18. From what I can find they are made by Deka.

[red31]

Katdaddy wrote:
I cannot find a spec sheet on these batteries

is there any reason you have not shared the brand/size etc of battery?

going on a month, is it some sort of secret?

[BFL13]

Katdaddy wrote:
And thanks again. I truly appreciate all the help that you and everyone else has given me in my quest to properly maintain my batteries.
My converter is apparently already adjusting for the high temps. When I checked the voltage the other day while connected to the converter it was at 12.97. I was a bit puzzled by this, but you just answered it for me.

Except the standard issue Boondocker you have does not have temperature compensation!

There might be more "issues". Good thing you have that LK if need be to act as the converter.

[Katdaddy]

And thanks again. I truly appreciate all the help that you and everyone else has given me in my quest to properly maintain my batteries.
My converter is apparently already adjusting for the high temps. When I checked the voltage the other day while connected to the converter it was at 12.97. I was a bit puzzled by this, but you just answered it for me.

[BFL13]

Katdaddy wrote:
I cannot find a spec sheet on these batteries. I have looked and found some commentary by people who may or may not know what they are talking about. One said the SG on these at 100% is 1.266.
Going forward, I want to make sure I am doing this properly. Before I was cycling them down to about 50% and then recharging with the "smart charger" which turned out to not be so smart. Do I want to recharge at a fixed voltage in the future and if so what voltage?

Set 14.8 on the LK with no battery connected. When the batts get down to 50% or whatever, clamp on to recharge to 80 or 90% (another topic---how to tell when you are at 90%) and run them back down to 50%-repeat.

Once you have shore power, use the LK at 14.8 (for 77F) till they are full by reaching 14.8 at the battery post (indicating little or no amps flowing because same voltage as charger is set to.)

At this time the SG will not be up to your target after previously doing several 50-90s. Now you do a "recovery" session at 16v to get the SG up. Once it is up, add water to the proper level and go to your regular converter for the Float at 13.6, which will drop to 13.2 after a while.

However, since you are baking at 97F, and 13.2 is for 80F, you could set something a bit lower (at least 13.0) on the LK for the Float voltage and use that instead of the converter.

You can set the LK at other than 14.8 for temp adj voltage. A bit lower for hotter and a bit higher for colder. 15.2 at 35F, and 14.5v at 97F eg.

Scroll down to Mark's post with the temp/voltage table
http://forums.trailerlife.com/index.cfm/fuseaction/thread/tid/26669731/srt/pa/pging/1/page/1.cfm

Trojan says their 6v are full when SG is 1.277 and voltage is 12.75 (a pair). It does vary among brands and where they sell them--"temperate zone" or with higher SG for up North or lower SG for Mexico.

[Katdaddy]

I cannot find a spec sheet on these batteries. I have looked and found some commentary by people who may or may not know what they are talking about. One said the SG on these at 100% is 1.266.
Going forward, I want to make sure I am doing this properly. Before I was cycling them down to about 50% and then recharging with the "smart charger" which turned out to not be so smart. Do I want to recharge at a fixed voltage in the future and if so what voltage?

[BFL13]

So that is your SG to shoot for when recharging from now on. You can compare that full SG with whatever your battery spec sheet says is full SG to see how close to "as new" your batts are.

Seems like they are in decent shape, and now you will be able to keep them that way. 🙂

[Katdaddy]

BFL13 wrote:
Is that after some time at 16v? You were at that SG before. So if you did the 16v, is that where SG stayed (stopped rising)?

Yes the temp correction works that way. Hotter than 77F makes the electrolyte less dense, so the hydrometer bobber floats lower showing less SG.

Yes, this is after 16v and where it stopped rising yesterday. I waited the 24 hours and checked a little while ago.

[BFL13]

Is that after some time at 16v? You were at that SG before. So if you did the 16v, is that where SG stayed (stopped rising)?

Yes the temp correction works that way. Hotter than 77F makes the electrolyte less dense, so the hydrometer bobber floats lower showing less SG.

[Katdaddy]

BFL13 wrote:

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)

I read this with a bit of amusement. I am in South Mississippi and as I sit typing this my thermometer reads 97 degrees. I may have to wait until October for the batteries to cool down. The batteries temped at 90 when I checked them just a while ago. They were at 93-94 when charging. The SG on all batteries is 1.275 or a bit higher. If I understand adjusting for the temperature this should equal 1.279-1.280. Am I correct in this or do I want to see 1.280 regardless of temperature?

[pianotuna]

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.

[MEXICOWANDERER]

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.