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Open Roads Forum  >  Tech Issues

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

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Naio

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Posted: 06/19/17 10:32pm Link  |  Quote  |  Print  |  Notify Moderator

MEXICOWANDERER wrote:


Then put the battery to work.



What is the best way to do that, given that I am in town now and have no 12v stuff?

Should I cycle it using a known load, e.g. a 300 watt heating which i think means 25amps dc?

Should I put my 900watt hot plate on it and make some bone broth? Is that too big a load?


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


MEXICOWANDERER

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Posted: 06/20/17 11:54am Link  |  Quote  |  Print  |  Notify Moderator

An alternative test is to just let the battery sit and take daily voltage measurements. But this takes time. Anything less than a week or two is not really useful.

AGM batteries are tough customers to test. They are accomplished "liars". A 90% charged AGM will load test so close to a 100% charged AGM that not even a "polygraph" can sort out the Pinocchio. CCA. Load testing, because it truly is intelligent and simple has almost disappeared.

A 500-amp adjustable load tester can be used to load a 180 ampere hour telecomm battery for a full 30-seconds at say, 250 amperes. Watch the voltage carefully. It should drop to an "X" amount of volts then remain there - within .2 - .3 tenths of a volt span. It should NOT continue to drop "quickly".

Stop the load draw.
Watch the voltage recovery

Each type of battery will recover differently. AGM batteries recover voltage much more quickly than say flooded antimony batteries.

Here is a symptom.
After a load test, voltage rises slowly from it's minimum during the load test. This is not a good sign. This is a sick AGM battery.

The trick is to find someone with an adjustable carbon pile load tester.

Lifeline has in PDF Manual format an excellent description of an AGM BATTERY CAPACITY TEST. This, by far is the best way to test an AGM battery but it requires expensive equipment and the test is involved.

So, all that can be done is to surmise test results using trends & tendencies.

Another home brew test is to make your own tester. Go to an auto parts store and purchase a 100-watt 12-volt light bulb. The bulbs look exactly like the old fashioned 120-volt screw-in light bulbs.

Then go to the hardware store and purchase a round ceramic base that the light bulb screws into. Splurge and buy the type with an on/off pull switch chain.

16 gauge wire is plenty big enough. Cheap battery clips will do fine

After you think the battery is charged. Disconnect charger and hook up the light bulb circuit.

Note the starting time. And the starting voltage of the battery

Switch on the light bulb

Allow it to burn for exactly 8 hours. Then shut it off.

At the moment after shutoff, what voltage do you see? Write it down.
Let the battery sit for six hours. Take another voltage reading. How high is it now?

Recharge the battery.

At 12.8 volts that bulb is going to consume 7.8 amperes

At 12.2 volts that bulb will will consume a theoretical 8.1 amps but the wattage factor is elusive at any but exact voltage.

Tricky? Yes? But this is not a computation of theoretically critical mass for plutonium. It is to allow for a general idea of what is going on.

If you want to, use Mr. Wizards, inductive panel ammeter.

Note starting amperage. Then take amperage and voltage readings hourly and record them.

At the end of 8 hours add up the 8 amperage readings. Then divide by eight.

At the end of 8 hours add up the 8 voltage readings. Then divide by eight.

The divided amp average is then multiplied by eight. This will give you a close-enough AMP HOURS CONSUMED result.

Do the same with the voltage. This will give you an averaged voltage for the test.

MULTIPLY the amp hour result by the voltage average result

This yields total watt hours. i.e. total volt/amp hours.

Mother Fletcher's Do It Yourself Battery Capacity Trends & Tendencies.

WARNING

Folks who would rather watch the Hog Holler 500 Live from Ahuwick, Mississippi, on TV may complain about this reply.

Naio

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Posted: 06/20/17 11:59am Link  |  Quote  |  Print  |  Notify Moderator

Well, I can let it sit and take daily measurements [emoticon]. The rest sounds a little too much for me, while I building new van, doing a year worth of upkeep on S&B farm in a summer, painting another house, and still sick...

Looks like I am on to the next battery, then!

Naio

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Posted: 06/20/17 03:57pm Link  |  Quote  |  Print  |  Notify Moderator

For today's project, I started with a battery that was at 12.66 after the year/s of storage. I was more csreful, did not start too high, he ked on it every 10 minutes. It kept creeping up, so I did not adjust the pot much. Started about 14.54 and it got up to 14.6 over a couple hours. Only taking an amp or 2.

Should I have turned it up more?

I had to go out, so I left it at the 14.6 and put it on a timer for one hour. Figured it couldn't get up to much naughtiness.

What should I do when I restart it? See if it creeps up more, or try to fiddle the pot for the extra 0.1v? Which might take an hour of fiddling... but maybe it important for what might be the last bit?

Gracias, and apologies if I am dense.

Naio

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Posted: 06/21/17 05:43pm Link  |  Quote  |  Print  |  Notify Moderator

Tell me if I did this right?

Got up today and this second battery was at 12.78. Fiddled it while watching for voltage un-sag, got it to 14.71v after an hour or so, but only taking about 1.25amps.

Figured ok clearly not full, so maybe it is desulfating. Left it going, amps increased to about 3, then decreased again. Took it off 3.5 hrs after stabilized, 4.5 hours after start.

It was still at 14.71 at the end (checked hourly), and back down to about 1.25amps. Terminals 80 degrees.

landyacht318

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Posted: 06/22/17 11:49am Link  |  Quote  |  Print  |  Notify Moderator

While not personally familiar with the Megawatt, I do not need to constantly fiddle with voltage pot on my Meanwell if I do not want.

I can set it to 14.7v and the battery terminals will be somewhat lower than this depending on how many amps are flowing and how depleted the battery is.

When there are no dc loads on a charging battery, and the amperage increases to hold the same voltage, well Mex once said during teh screw31 thread, that this was the very beginnings of thermal runaway, and I stopped charging, or monitored heat build up closely when I saw this occur, on my old flooded battery. Never saw it on my AGM.

While charging slows a lot at 13.6v, compared to 14.7v, rather than turning it on and off, if you've got shore power I'd set MW voltage to 13.6ish, and let it go when you do not want to have to monitor it and then goose it to 14.7 when you can be there to monitor amperage and temperature. 13.6v is not going to heat a AGM battery at 77f ambient.

The Micropotentiometers provided with these powersupplies are not meant for constant adjustment. They are rated for only 25 or 50 cycles, and that is a Bourns brand( usually blue in color). Who knows what the cheaper orange ones are rated at.

I hope the simple instructions as to how to replace the provided pot with a 10 turn upgraded pot can be published soon. I've done it on the cheapowatt, and my Meanwell. I removed electronic guts from casing to do so, but I think Mex has a method for accomplishing this without removing the guts to access underside.

Removing the guts is pretty easy, but one should have new thermal grease for reassembly as the transistors using the casing as a heatsink.

MEXICOWANDERER

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Posted: 06/22/17 12:01pm Link  |  Quote  |  Print  |  Notify Moderator

Just to clarify...
When recovering or conditioning an AGM battery, amperage will definitely see spurts and slumps.

But during normal recharging, even from 20% state of charge, jumps in amperage, with constant voltage should arouse suspicion. Not alarm, merely heightened awareness. If monitored, thermal runaway at amperages of these small units is not sudden. Amperage ramps up and heat on battery posts is absolutely noticeable.


MEXICOWANDERER

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Posted: 06/22/17 12:14pm Link  |  Quote  |  Print  |  Notify Moderator

[image]




Supplier: MEAN WELL
Part No: RSP-1500-15
RoHS: Yes
Efficiency: 87(Typ) %
Type: Switching
Output Voltage: 15 V
Output Type: Fixed
Input Frequency: 47 to 63 Hz
Family: RSP-1500
Supplier_Package: N/A
Packaging: N/A
Maximum Output Current: 100 A
Pin_Count: 17
Number of Outputs: 1
Maximum Input Current: 17(Typ) A
Mounting: Desktop
Minimum Isolation Voltage: 3000 VAC
Operating Temperature: -20 to 70 °C
Dimension: 278 x 127 x 83.5 mm
Maximum Output Power: 1500 W
Output Connector Type: N/A
Input Connector Type: Screw Terminal Block
Style: Enclosed
Supplier Temperature Grade: N/A
DC Input Voltage: 127 to 370 V
AC Input Voltage: 90 to 264 V

Naio

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Posted: 06/22/17 12:15pm Link  |  Quote  |  Print  |  Notify Moderator

Thank you, both of you [emoticon].

One of my remaining batteries is at 12.35. Should I do anything differently with it, due to low SOC?

Will the Megawatt keep itself to 36amps, or do I need to wstch and lower voltage to keep amps from going too high?

Any other special considerations for that low a battery?

MEXICOWANDERER

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Posted: 06/22/17 12:30pm Link  |  Quote  |  Print  |  Notify Moderator

Naio,

According to your post you are doing everything correctly. The battery you reported on should be put into service and with those thick plates should give you long, trouble-free service.

A lot of this chatter deals with nuances. I should make myself clearer as to what is interesting versus what is important.

Once Delta T voltage slump is established, compensated voltage should be noted then can be dialed-into the initial power supply setting when voltage is pre-set meaning before the cables are connected to the battery.

For instance, my power supplies. Lambda, Meanwell, and Megawatt all slump when connected to battery. This means, the converter will show say 14.70 volts with cables disconnected, but then settle on 14.51 when connected. Voltage does not rise to 14.52

What to do?

Then, do not pre-set the disconnected voltage at 14.70. It will be .19 volts too low.

Twist the adjustment pot to 14.70 + .19 volt = 14.89

Disconnected pre-set voltage thusly will be set at 14.89

Monitor finish voltage to be sure this is a correct assumption and tweak accordingly.

Different types of batteries will have different amounts of Delta T voltage slump. Types of batteries, not size or state of charge.

Once the Delta T compensation is set, it is set.

Note it. Write it down on a strip of masking tape.

Example: 14.70 set to 14.89

13.30 set to 13.39

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