Some battery temperature data during high amp recharge

[landyacht318]

Northstar group27 AGM battery. 90Ah capacity.

5:58AM 53Ah from full, 12.1v under 0.8 amp load
62.2f battery, 61.3f Ambient

Apply Meanwell's 40 amps set to 14.9v( accounting for voltage drop on wiring at 40 amps)
35 minutes later at ~14.6v at battery terminals, amps begin tapering from 39.1.
Temperature 73f
~1 hour later 14.6v accepting 21 amps...... 78.9F.

~ 5 hours later accepting 0.4 amps at 14.5v, 72F, ambient ~67.4f

Battery warmed more than expected. Ambient temperature only increased 6 degrees during the ~6.5 hour charge.

Thermocouple sensor tip located on side of case, on middle cell, mid height with a big blog of arctic silver thermal grease held in place with black Gaffers tape and one layer of reflectix over that surrounding 4 battery sides.

More glad than ever I can control the voltage the alternator is allowed to maintain when driving. The 14.9v the original VR allowed, combined with a hot battery, has to have been bad for this AGM, which is on about deep cycle #350, yet still performing admirably, as long as it gets this high amp recharge every so many deep cycles.

Battery located Not in engine compartment, but under van body behind driver's seat. The sensor's location allows it to read engine heat when driving and it takes a minute or 3 after engine shutdown for an accurate battery case temperature reading. This engine heat in this location is also more than expected. Longer highway drives likely help heat battery much more than expected in this location.

Overall, I greatly underestimated battery temperature rise during charging, and when alternator charging, this heating can be even more pronounced, and detrimental when voltage is allowed to be held up in the high 14's.

I've been using this 4 channel K type thermocouple device, and so far have sensors located on battery, alternator casing, and voltage regulator transpo540HD added heatsink.

http://www.amazon.com/Perfect-Prime-4-Channel-Thermometer-Thermocouple--200~1372%C2%B0C/dp/B0142HFA0...

[landyacht318]

The depth of discharge was not quite as deep this time, and it did have a fair load on it right before I started charging, unlike the previous test.

Battery got upto 82.2f this time. The battery monitor was out of whack, it was saying 1Ah from full while the battery was still accepting 2.2 amps. In my experience it takes about 1.75 more hours to taper from 2.2 amps to 0.4a at 14.5v with this battery.

[MEXICOWANDERER]

Now, start "shocking" the plate structure with joules of impulse energy. Measure the impulses by kWh of energy (joules/second would be more accurate) then measure apparent changes in electrolyte density. Ooooooo where did all the "missing" energy go?

Examine the DUT plates 4X - 10X diopter and the answer will jump out at you.

[MEXICOWANDERER]

Welcome to the wonderful world of electro-chemistry. Laminar plate / electrolyte occlusion. Isn't this fun?

[pianotuna]

Look at the temperature of the battery. My guess is that with an initial low temperature (ratings are done at 77 f , 25 c) that affects the rate of charge. Then the jar warms up and gets "back on track".

landyacht318 wrote:

Started at 64.2f, now upto 70.1f

I am curious as to why the initial voltage yoyo occurs some times, and not others.

[NinerBikes]

It probably has to do with chemistry, why the voltage is staying low this time at high amperage. More resistance?

[landyacht318]

Another high amp recharge happening now from 50%, ~48AH from full.

This time the voltage did not rise fairly quickly to 14.5, then drop to 14.0, then take ~25 more minutes to rise back upto 14.5v at a steady 38 amps.

Right now the monitor is saying 9Ah have been returned, battery voltage 14.0 and accepting 38.4 amps.

Started at 64.2f, now upto 70.1f

I am curious as to why the initial voltage yoyo occurs some times, and not others.

[MEXICOWANDERER]

I prefer VOLTAGE LIMITING. It's easier to type.

[wwest]

A 1000W MSW inverter Connected to, powered by, the engine starting battery, ONLY with the engine running, powering the onboard controlled charge converter will allowing deep cycle batteries to be charged without boiling the electrolyte.

[MEXICOWANDERER]

If you suspect electrolysis is overwhelming the battery recombinant capability, carefully examine the ends and sides of the battery. The walls will noticeably bulge before venting.

A similar thermal test should be conducted on a 5% antimony flooded battery, using constant voltage 14.8 volts (unlimited I) to gainsay the hypothetical theory-bound wolf-cries of novice theorists. Temperatures does rise, eventually. But reading articles penned by amateurs posing as experts can be thwarted by doing one's own tests. Voltmeter, Ammeter, Pyrometer, eyesight, and use of frontal lobes.

By the way, high voltages for AGMs should be reserved for conditioning and capacity restoration. Excessive positive plate shedding should be avoided.

[pianotuna]

Hi,

Yes, it is a starved acid AGM. Great that it is serving you well.

[landyacht318]

It is an AGM battery with certain recombinant abilities, and no listed upper limit on initial charging amps.

Whether the vent has opened and allowed some gas to release is an unknown. What I can say is the battery performs very well, and behaves much better after a high amp recharge from 50% to a 0.5% capacity amp tapering at absorption voltage. Behaves much better than a low and slow solar only return to full.

While I can notice it lost some of its violent engine cranking ability in its ~32 month lifespan and 350 deep cycles, based on voltage alone during discharge for the AH removed to the 50% range, I can detect no loss of total capacity. I am sure there is capacity loss, but in 100% to 50% depletion levels, I am not seeing any obvious signs of it, and am impressed with this battery, so much so that i no longer have a dedicated engine starting or house battery but use this one battery for both duties, and without fear.

All my available charging source's voltage, can now be precisely controlled, which was not the case when this battery was new and first started cycling. I was a the mercy of my vehicles voltage regulator, which was bat **** crazy, and a Schumacher sc2500a, which loved to go to 16+ volts at 25 amps and make any battery gurgle and gass.

MexWanderer set me up with an adjustable alternator voltage regulator, and turned me onto the adjustable voltage power supplies, and my solar controller is adjustable too, So I've got all bases covered, and a hard working hard cycling well performing high$$ AGM battery.

[pianotuna]

Thanks for taking the time to document this.

During the 78.9 temperature you are exceeding the gassing voltage.

At 72 also exceeding gassing voltage.

Here is a truncated table.

At 59 gassing voltage is 14.655

At 68 gassing voltage is 14.49

At 77 gassing voltage is 14.34

At 86 gassing voltage is 14.19