Good Sam Club Open Roads Forum: Understanding length of time for absorption & finish charge
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 > Understanding length of time for absorption & finish charge

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wopachop

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Posted: 04/03/20 07:10pm Link  |  Quote  |  Print  |  Notify Moderator

Im referencing the Trojan guide for charging flooded batteries. They are a mix of old 8v Trojans and newer 8v Generic Brand. I have the charger set for 2.45v per cell. (i didnt temp compensate, weather app says its 65F right now)

Trojan says to do a maximum of 4 hours absorption. At that time im still not dropping to the 1-3% finish charge range.

I can tell the charger to drop to a constant current charge. Which i just did its at 2a for a 170ah battery. My question is how long do i leave it on the constant current finish?

Ive read the Trojan guide over and over and all im seeing is " The finish phase ends when the battery is fully charged." How long is that?

My charger does have a setting on what % to stop the charge at. I will have to check what its set to. I messed with it a couple months ago. Lets say i set it to 3%. That means when the charger hits the 3% finish charge the length of time would be zero. But that could be well passed the 4 hour absorption charge.

Does a smart charger for flooded batteries have a time setting that automatically switches to a finish current? I would like like to use my charger to mimic what the smart chargers do. I dont have to wait for the 4 hour maximum absorption time to drop the voltage.

I also dont have to follow Trojan 100%. When i ask advice before there were other brands people linked. I bookmarked their instructions but have not looked recently.

Oh...i do have a tool to measure specific gravity. I dont think i want to dip it in these old batteries. I try to keep the tool all nice. Its only been used on my brand new 6v. I suppose the answer to my question is going to be that i cant use time. You have to use SG. Geez great.

What about an educated guess on timing? New batteries versus older batteries. I swear some of these have to be 10-15 years old now.

edbehnke

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Posted: 04/03/20 10:34pm Link  |  Quote  |  Print  |  Notify Moderator

I'd love to know what this is about. What kind of RV are we talking about?

I guess I never heard of 8 volt batteries being used in an RV.

All I can say is don't mix old batteries with new batteries.


eddie and sandie
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landyacht318

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Posted: 04/03/20 10:37pm Link  |  Quote  |  Print  |  Notify Moderator

Gee, I need to get from point A, to point B, but my tires are new, and I don't want to get them dirty.

[emoticon]

Use the hydrometer/ refractometer, and rinse it after each use, and before putting it away rinse it a bit better and dry it.

When Amps stop tapering at absorption voltage, and start rising, call em done, is another method.

Or are you afraid of wearing out the spring on your DC Clampmeter's clamp?

I've had the absorption stage take 4 hours and I've had it take 14 hours, and I certainly wont be venturing a guess on your batteries.

wa8yxm

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Posted: 04/04/20 05:08am Link  |  Quote  |  Print  |  Notify Moderator

wopachop wrote:

Does a smart charger for flooded batteries have a time setting that automatically switches to a finish current? I would like like to use my charger to mimic what the smart chargers do. I dont have to wait for the 4 hour maximum absorption time to drop the voltage


First did you mean to type 8V or did you mean 6V?
Due to the way you worded the rest of your post.. the answers are the same no matter which you meant.. But I've not seen an 8/16 volt RV. only 12 volt (Two six in series make one 12). I also make many typos.

Now.. to answer the question above yes and no depending on the charger.
Some (IE Parallex 7300T switch modes based on an internal clock
Some (most smart chargers I suspect) Measure current and voltage.

Some.. are not as complex as their instructions.

For example my Progressive Dynamics wizard Controlled speaks of 3-stage charging but as I recall the output voltage in "Bulk" mode is the same as in "Absorption" (The current drops is all) And from what I can tell that is the best.. From my voltmeter readings (I have a volt meter on a wall where I frequently look at it.. (Across from what is sometimes called "The Throne" you know the room where you use that roll stock everybody is panic buying now days. I'm a frequent flyer there for ONE reason, occasionally for TWO) anyway I see it dropping to "battery only" voltage from time to time so I think the wizard is basically pausing the converter in order to check battery voltage and changing modes based on that.

But the bottom line is there are many ways to do it and different multi stage converters may use different systems.

Oh the parallex 7300T that' T for Two and Two for Tea (As the old song goes) is a TWO stage.. bulk for a period of time THEN float. no absorption.


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Vintage465

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Posted: 04/04/20 07:11am Link  |  Quote  |  Print  |  Notify Moderator

This is way over my head. My solar charges my four 6v using 14.8 volts and when I see the Panel voltage gauge jumps to 20v on the gauge and my battery voltage is over 13.5v..........it's done.


V-465
2013 GMC 2500HD Duramax Denali. 2015 CreekSide 20fq w/450 watts solar and 465 amp/hour of batteries. Retiring in 2021, then look-out road, here we come!

MEXICOWANDERER

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Posted: 04/04/20 07:46am Link  |  Quote  |  Print  |  Notify Moderator

No can do ACCURATELY.
Chemistry by derivites?
Slightly less inaccurate guesswork?

A census count after sundown by the number of rooms lit?

2oldman

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Posted: 04/04/20 08:06am Link  |  Quote  |  Print  |  Notify Moderator

I'll bite.. why are you using 8v batteries, and OLD ones at that?

BFL13

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Posted: 04/04/20 09:11am Link  |  Quote  |  Print  |  Notify Moderator

Trojan's IVI approach needs a special charger, not easy. Yes their 4 hour time does not fit their other statement that times will vary.

IMO ignore all that and use this approach even with Trojans, only use Trojan's voltages with theirs. This is an IV method which is a lot easier to do with the available chargers. Note the times to end each phase.

And yes, believe the hydrometer.

https://www.eastpennmanufacturing.com/wp........able-Energy-Charging-Parameters-1913.pdf


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wopachop

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Posted: 04/04/20 11:19am Link  |  Quote  |  Print  |  Notify Moderator

Interesting BFL13 that link is saying max absorption time is 12 hours. That would make more sense for what im seeing. At the 4 hour make the current is still well above the 1-3% finish charge.

Makes sense Landyacht has seen it take 14 hours.

The 8v's really help to rinse the conditioner out of my hair.
(thats a joke)

wopachop

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Posted: 04/04/20 11:28am Link  |  Quote  |  Print  |  Notify Moderator

landyacht318 wrote:

When Amps stop tapering at absorption voltage, and start rising, call em done, is another method.

Or are you afraid of wearing out the spring on your DC Clampmeter's clamp?
Im confused by amps tapering, and then rising. I dont think im following exactly what you mean.

The charger itself is listing the amount of amps. (although i have used a clamp meter to check what the charger says and then how many amps are actually going through the wire next to where it attaches to the battery.....i had to make bigger cables because of excessive drop)

I set the charger to 10% of C20. On my old batteries it hits 2.45v in like 10-30 seconds. The amps taper down and maintain the 2.45v. Problem was that at 4 hours of absorption the charge current was still higher than 3%. Looks like the answer to my question is to leave it hooked up. Even if it takes 14 hours. (the newer batteries hit 2.45v in about 2 mins....which makes sense because the c-rating of my old batteries must be toast)

Note these are batteries that i fully charged 6 months ago. They have been sitting unhooked in the garage.

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