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Open Roads Forum  >  Tech Issues

 > Got my new (used) batteries!! Now, how do I rejuvenate them?

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CapnCampn

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Posted: 06/22/17 03:36pm Link  |  Quote  |  Print  |  Notify Moderator

MEXICOWANDERER wrote:

THE LOWER THE POTENTIOMETER RESISTANCE THE HIGHER THE VOLTAGE

Sooooooo.........

Why not use the onboard potentiometer? Preset it to whatever float voltage seems acceptable?

But

Instead of an external potentiometer like a 10-turn pot

Use a wind up 6 hour Intermatic Timer
With a resistor in series?

Resistance is cumulative, so a test will be needed to discover what resistance of resistor is needed to achieve a timer controlled absorbsion charge voltage. Big deal. A timer and resistor makes a 2-stage charger.


That's an interesting idea, just parallel the timer/resistor combo with the existing pot. When the timer is on, the parallel resistance is lower than the pot itself -> higher voltage. When the timer turns off, the additional parallel resistance leg is removed from the circuit, raising total resistance & lowering voltage again to the preset float value.

I like it. [emoticon]

CC

MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 06/23/17 09:49am Link  |  Quote  |  Print  |  Notify Moderator

Good señor CC

Your comment encourages me to keep fooling around with this stuff. Hmmm...two timers would make the process true three-stage. Lowest resistance, top charge, mid resistance bulk charge. High resistance, float.

I am researching adequate thermistors. Epoxy package. JB Weld to battery CABLE CLAMP. Used as a pull down resistance. Goes in series with timer lines. Only needs to sweep about 66 ohms from 0F to 100F. Did I mention my German temp switches that open circuit at 110F ?

If it doesn't exist.......make it exist.

Make America Less Stupid Again...(no political affiliation)

Naio

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Posted: 06/23/17 09:54am Link  |  Quote  |  Print  |  Notify Moderator

MEXICOWANDERER wrote:

. Did I mention my German temp switches that open circuit at 110F ?


Oh, that is NICE!


3/4 timing in a DIY van conversion. Backroads, mountains, boondocking, sometimes big cities for a change of pace.


Naio

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Posted: 06/27/17 11:24am Link  |  Quote  |  Print  |  Notify Moderator

Weather is no longer boiling hot, so today I will resume battery project.

I am a little concerned because, going over the thread, I see you guys told me repeatedly that voltage slump should be the same for all the batteries and I should not need to keep twiddling the pot, but that is not my experience. I have to do it anew for each battery. Does this mean something?

Naio

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Posted: 06/27/17 11:29am Link  |  Quote  |  Print  |  Notify Moderator

FYI, I emailed John Marles and he says

Quote:

No it will not limit at 36 amps. It s a 90% duty cycle power supply. You have to run it under 90% duty at 36 amps. It is only made to charge a standard car batteries one at a time. Other larger batteries may draw too much.


So I was skating on pretty thin ice with my 29a the other day.

Naio

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Posted: 06/27/17 11:33am Link  |  Quote  |  Print  |  Notify Moderator

Also he said he would sell me one of his power cords with inline rocker switch for another project (I got a 24v meanwell on ebay), $10 incl shipping.

Naio

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Posted: 06/27/17 01:19pm Link  |  Quote  |  Print  |  Notify Moderator

Summaries and updates.

(I have named the batteries in order of SOC when I got them, which is not the order I messed with them in. May be a bit confusing, but to me it makes sense!)

A:
12.68 when got it.

Third one to charge.

7-8 amps start at 12.70. Went down to 12.61, up to 10 amps, 105 degrees. 10 mins later got higher, and hot to the touch, so disconnected.

Mex said may be bad cell, let it sit and check voltage without charge next week

12.83 today.

B:
Did this one second.

12.66 before start. Only took an amp or 2 to start, amps increased to about 3, then decreased again. Took it off 3.5 hrs after stabilized, 4.5 hours after start.

After sitting overnight, only 12.87.

12.80 today.

C:
Did this one first. 12.47 before I began.

Nearly 29 amps at 12.70 to start. Did not realise volts would keep rising. 15.20 after an hour, fiddled it down to 12.67, 15amps, but then disconnected bec uncertain.

12.97 in am so did not charge more.

Next day, 12.94 after about 40 hours rest. Put it at 14.74v, took 3-4 amps, for 4 hours, not warm, then increased amps. End of the run was at 12.68v, 6.3 amps, and barely warm

13.04 today, a week later. Lookin' good!

D:
Have not touched this one yet. 12.35 when it arrived, and today.

Naio

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Posted: 06/27/17 01:19pm Link  |  Quote  |  Print  |  Notify Moderator

What should I do with battery A? That is the one that got hot.

I put B on the MW. Taking 2amps (decreasing) starting at 14.44v (increasing), letting it unsag.

I am thinking to check C next, to verify that it is done charging but I sure think it is.

And then start on D, keeping volts low enough to limit amps to 25-30.

Unless y'all tell me otherwise!

pianotuna

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Posted: 06/27/17 01:26pm Link  |  Quote  |  Print  |  Notify Moderator

I would charge battery A again and see if it gets hot. If it doesn't--then just use the darn thing.


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.

MEXICOWANDERER

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Posted: 06/27/17 01:34pm Link  |  Quote  |  Print  |  Notify Moderator

John Marles is a very savvy, honest individual. No, those power supplies are not supposed to "max out" hour after hour.

This is why I investigated, and found the top three weak points in the Megawatt, experimented, and deduced the three answers to reduce failure rate at over-max loading.

I have had one of my modified 36-amp (400 watt) Megawatts producing maximum amperage for eleven days straight. With an ambient temperature in excess of 90F.

The few mods I did renders the Megawatt near bulletproof.

Get a wire grill screen guard for the original fan.

Cut the segments out of the aluminum case cutout leaving a large hole
Attach the wire fan guard. An immense increase in air flow

Put small legs under the Megawatt case. Otherwise most of the air inlet is blocked if sitting flat.

Replace 2 largest capacitors with Panasonic low ESR 105c 680uf 200 volt units, the replacements are slightly smaller.

Replace 2 schottky rectifiers (30 HSQ 100) with EIGHTY AMPERE, 150 volt rectifiers. Both grades of rectifier are identical physically.

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