Battery Health

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Battery Health

Postby lfhoward » Sat Mar 30, 2019 12:23 pm

Hi All,

My 3 batteries were manufactured in 2/15 (4 years and a couple of months ago). I have been wondering how long they will last. They are deep cycle marine Group 24 batteries, the regular lead acid kind (not AGM).

I read the recent thread on desulfating with interest. http://www.tnttt.com/viewtopic.php?f=2&t=71499. I have an MPPT solar charge controller attached to a 150 watt high voltage solar panel, which keeps them topped off at 13.7+ volts during the day. A lot of the time while the trailer is parked there is no real draw (except to run the charge controller). My charger doesn't have a desulfating mode.

As a test, today I disconnected the solar and ran the lights and the Fantastic Fan on high for 10-15 minutes (probably a current of 4-5 amps). Voltage came down to 12.3 while the fan was running and seemed to stabilize there. With the surface charge burned off, I then turned off the lights and fan to let the batteries recover. Within 5 minutes the voltage went up to 12.6 volts. The temperature outside was 77 degrees F (25 degrees C).

From what I read, 12.6-12.7 volts is "full" on a resting battery at around 70 F. I have a sneaking suspicion that my batteries can't power my trailer for as long as they used to 4 years ago, but 12.6 volts at rest doesn't seem to be bad. Is my logic sound? (I know I should be measuring specific gravity of each cell but don't really want to go there, and I don't have the equipment.)

For those battery gurus out there, please give me your 2 cents. Are my 4+ year old batteries still ok, and how long should they last? (I don't let them go below 12.2 volts at rest, which I think is 50% charge on a hot day.). Thanks!!
My off-road camper build on an M116A3 military chassis:
http://www.tnttt.com/viewtopic.php?f=50&t=62581
Tow vehicle: 2008 Jeep Liberty with a 4 inch lift.
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Re: Battery Health

Postby tony.latham » Sat Mar 30, 2019 1:23 pm

From what I read, 12.6-12.7 volts is "full" on a resting battery at around 70 F.


I frequently struggle to try to understand the difference between volts, watts, and amps. Here's my belief: That resting voltage means it is fully charged but I don't think it indicates how many useable amps are in it.

But I'll be curious to hear what others think about this. :thinking:

Tony
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Re: Battery Health

Postby Esteban » Sat Mar 30, 2019 2:27 pm

I was able to bring my Subaru Forester's battery back from "the dead" with a Noco G3500 charger 2+ years ago. It may have been sulfated. The battery has worked reliably since then. I wrote more about that in Cosmo's thread about desulfating.
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Re: Battery Health

Postby MtnDon » Sat Mar 30, 2019 3:49 pm

tony.latham wrote:
From what I read, 12.6-12.7 volts is "full" on a resting battery at around 70 F.


I frequently struggle to try to understand the difference between volts, watts, and amps. Here's my belief: That resting voltage means it is fully charged but I don't think it indicates how many useable amps are in it.

But I'll be curious to hear what others think about this. :thinking:

Tony



You are correct. The voltage alone does not mean much. The non-loaded voltage might appear to be within limits but as soon as a load is applied the volts can fall. That is why the auto store uses a load tester .
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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Re: Battery Health

Postby John61CT » Sat Mar 30, 2019 4:39 pm

The load testers garages use does not tell much about SoH wrt deep cycling usage.

Their domain is starter batts, for cranking the engine, different world.

Since you started out with a battery not great for deep cycling anyway, it may last another couple years at most.

Is your use case mission critical and you **really need** reliability, as in powering a medical device, or living far from civilization?

If not cheapest easiest option is keep using it, then replace once the signs of it's imminent demise are obvious.

If so, cheapest easiest option is proactively replace it every 3-4 years no matter how healthy it seems.

The only real predictor* is a proper constant current draw-down from 100% Full, at the spec'd 20-hour current rate.

The proportion of time it takes to get to 10.5V, relative to that 20-hour Ah rating is its State of Health.

Industry standard is EoL at 80% SoH. Consumers may push past that, at increasing risk of "unexpected sudden failure" events.

It's pretty rare for lead batts to explode, and you do have a good containment box right?

*without huge lab-grade instrumentation costing many thousands
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Re: Battery Health

Postby lfhoward » Sat Mar 30, 2019 9:05 pm

It’s not a life or death situation like with a medical device, but my wife and I will be camping where the overnight lows could be in the 40’s and I want to make sure our Roadpro electric blankets will have enough juice to keep us warm. They draw 4.6 amps each, so we couldn’t run them continuously. I imagine turning them on to warm up, then off, and layering with lots of quilts. If we get cold in the night we could again warm ourselves up and then click them off. Repeat as necessary. The blankets are new, so this is an experiment.

Our trailer is insulated with 3/4” of styrofoam in the walls and 1-1/2” in the ceiling. The floor has 2 layers of interlocking gym mats. It should be warmer in there with us in it than the ambient temperature outdoors. I also have the solar panel which should replace some of the amps during the day that we used at night. The max charging amps I’ve seen on a sunny day was about 7, but it’s usually around 4-5 when the battery is bulk charging. If these were 80 amp hour batteries initially, the trailer had 240 amp hours of storage when the batteries were new, so 120 usable amps. If I conservatively say the battery bank holds only half of the juice it once did, that would be 60 usable amp hours. 2 blankets draw 9.2 amps. 60/9.2= 6.5 hours of power, which should be fine if we don’t leave the blankets on continuously. On the charging side, if there are 6.5 usable hours of good sunlight and we get 4.6 amps out of the panel, we make back the equivalent of 1 blanket worth of power during the day. But we are only camping 2 nights.

Lots of assumptions here! I am trying to be conservative in estimating my batteries may only be half as good as they were when new. If they are worse, we could end up without enough power for the blankets. Worse case scenario we have to go home early. I would like our camping trip to be fun though.
My off-road camper build on an M116A3 military chassis:
http://www.tnttt.com/viewtopic.php?f=50&t=62581
Tow vehicle: 2008 Jeep Liberty with a 4 inch lift.
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Re: Battery Health

Postby lfhoward » Tue Apr 02, 2019 11:51 am

I ordered a desulfation device to see if it helps recover some capacity in my battery bank. It came today.

Image

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https://www.pulsetech.net/pp-12-l-powerpulse-12-volt-battery-maintenance-system.html

There are many knockoffs of this on eBay and Amazon, although this one is made by a US company. It gets 4.5/5 stars on Amazon and most people report an improvement in storage capacity in their older batteries within a couple weeks to a month. It’s designed to be attached to the battery and runs off the current in the battery to generate electrical pulses to encourage the sulfur deposits on the plates to go back into solution. It would very slowly drain a battery except that mine are charged every day by solar. People on Amazon reported no issues with this interfering with the electronics in their rigs or their solar charge controllers. I got it because I don’t have a place to plug in a charger where I store my trailer, so a desulfation cycle would have to be powered by the trailer itself.

I’ll report back whether it seems to work.
My off-road camper build on an M116A3 military chassis:
http://www.tnttt.com/viewtopic.php?f=50&t=62581
Tow vehicle: 2008 Jeep Liberty with a 4 inch lift.
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Re: Battery Health

Postby lfhoward » Thu Apr 04, 2019 3:34 pm

I installed the PowerPulse device on the battery bank today. Fingers crossed!

Image

Little blinky LED says it’s working... :thinking:

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My off-road camper build on an M116A3 military chassis:
http://www.tnttt.com/viewtopic.php?f=50&t=62581
Tow vehicle: 2008 Jeep Liberty with a 4 inch lift.
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Re: Battery Health

Postby Sparksalot » Sun Apr 07, 2019 5:11 pm

I keep looking at your battery box and wondering how much weight you have on your tongue.
Done? Surely you jest. A teardrop is never "done".

The Compass Rose build thread: viewtopic.php?t=23213

Inspiration: http://tnttt.com/Design_Library/Trailer%20for%20Two.htm

It's got a cop motor, a 5.3 LS plant, it's got cop tires, cop suspensions, cop shocks. ~ Elwood Blues
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Re: Battery Health

Postby lfhoward » Sun Apr 07, 2019 8:55 pm

Sparksalot wrote:I keep looking at your battery box and wondering how much weight you have on your tongue.

Probably 150 lbs or so. The Jeep’s hitch can handle 500 lbs of tongue weight and the rear springs are beefy for the 4” lift. The trailer has a landing leg with a built in jack so I don’t have to lift it.

Image
My off-road camper build on an M116A3 military chassis:
http://www.tnttt.com/viewtopic.php?f=50&t=62581
Tow vehicle: 2008 Jeep Liberty with a 4 inch lift.
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