Woo Hoo..New AGM Batteries

landyacht318 wrote:
I find Voltage goosing from float to absorption and watching the amps is very revealing with my AGM. If they quickly taper back to low levels, all is good, if they do not, then the battery was floating at too low a voltage, or not fully charged.

With a ~50f degree battery I found that 13.6v was too low, and a 14.7v spike needed an hour to taper back to below 0.5% of AH(20hr)

Not unexpected, but nice to see theory proven with measurement tools, and adjustable voltage power supply.

Yes, 13.6 is too low for float at 50F.

It is 2:39PM CDST in OKC and I just checked and my 48F temperature AGM is being floated at 14.24V by the MS TS 45 PWM solar controller. That is the beauty of a temp-comp charger. IMHO, no goosing needed.

HTH;
John

I find Voltage goosing from float to absorption and watching the amps is very revealing with my AGM. If they quickly taper back to low levels, all is good, if they do not, then the battery was floating at too low a voltage, or not fully charged.

With a ~50f degree battery I found that 13.6v was too low, and a 14.7v spike needed an hour to taper back to below 0.5% of AH(20hr)

Not unexpected, but nice to see theory proven with measurement tools, and adjustable voltage power supply.

Trends and Tendencies

Thicker mat telecom batteries live in a world all their own as far as electrical characteristics are concerned. On the opposite side of the aisle, Concorde's pricey mat allows for closer plate spacing and that skews charging characteristics.

On long-term float I occasionally zot 14.40 volts and watch the amperage. If amperage is 1.0% AH or less I terminate the zot. Sometimes I see 3.0 - 4.5 amperes. Electricity is predictable. Chemistry is predictable. Electro-chemistry is not - not by a long shot.

4:30 am

Voltage 12.84
Load 1.7 amps
87.4% SOC

BFL13 wrote:
"I think that would just screw up the readings, I don't think the charge rate would hold consistent over the set up time of setting meter..."

AFAIK as long as the draw is higher than the charge, the chargers will hold constant amps even if the draw varies but stays higher. The 75 would need to be set nearly the same voltage as the 40 doing 20 of course.

Sounds complicated!

i would have to measuring the charger/or converter, i would have to rewire to put the shunt in the charge line only (instead of on the battery post), to measure only the converter/charger supply amps

i don't think i'm going to do that, the converters already amp meters, but the shunt is on the batteries, and there are multiple cables

if I got really serious, i could make a short in cable to go between the shunt and the battery, put a hall effect sensor around it
and use both the clamp on and the hall effect meter to get a consensus and calibrate the power meter amps to that reading

BUT not tomorrow or even this week

MrWizard wrote:

...
Maybe the coffee maker to heat a pot of water, that is fairly even Resistive load,
...

That's what I tried to do when calibrating the same meter ('cept mine only goes to 100A), boil a liter of water. It should have been about 75A but then discovered my new 1/0 cables are too big for the clamp-on. Arrgggh.

So instead I let the batteries draw down, and on a sunny day my Rogue gave them its max at ~31.5A, and I calibrated the meter at that. You do what you have to do.

Another problem was setting the 0a. For some reason it was very touchy. Close to zero, the "+" button would actually reduce the A, and at another time it would increase the amps.

For a nominal (when new) 447Ah battery bank, I just set the max to 215Ah (half the maybe-actual? 430Ah of the mis-matched relatively new GC2s). That way the full-battery re-adjustment is not so tediously long.

After the last boondock, I fully charged the batteries normally (14.9V absorb to ~0.6% of Ah), then equalized at 16V for an hour, and then declared them full and reset the Ah counter.

"I think that would just screw up the readings, I don't think the charge rate would hold consistent over the set up time of setting meter..."

AFAIK as long as the draw is higher than the charge, the chargers will hold constant amps even if the draw varies but stays higher. The 75 would need to be set nearly the same voltage as the 40 doing 20 of course.

Sounds complicated!

I think that would just screw up the readings, I don't think the charge rate would hold consistent over the set up time of setting meter
The LED light strips have a real consistent load
Although much lower than my max discharge or recharge rates

I did use the clamp on to compare load readings to the power meter , with fans lights fridge and pc

I did not compare with the inverter powering the MW
Perhaps tomorrow, I'll do a comparison reading
I can have dw push the buttons and heat a cup of coffee while I use clamp on and compare to the power meter

Maybe the coffee maker to heat a pot of water, that is fairly even Resistive load,
YES less than the mw, but more than something else except the vacuum or the hair dryer
Switching power supplies and motors cause the inverter load to go all over place

Can you disconnect the inverter from the shunt to be battery direct, run the inverter to pull 100 amps or so, and run the 75amp and the 40 amper at 20 amps to get 95 amps steady charger total across the shunt to then be able to calibrate the meter at 95 (near the 100?)

my meter discharge and recharge readings were drifting from NEW,
faster higher discharge rates, slower lower longer recharge rate

meter not showing full, even when down to just a few amps charge rate

so Friday, i re-calibrated the power meter, the instructions recommend checking this every month
i had not done this in about 6 months
any way
fully recharge batteries to the point of 0.5 percent capacity charge rate ( in our case 3.7amps or less )

turn off all DC loads, turn off inverters, turn off all charge sources including solar ( flip off CB )
turn on only straight unregulated DC led lighting, all LED light strips
use clap on meter to measure amps load (yes inline DC amp meter/multi-meter would be better )
perform zero default reset of power meter
set amp discharge reading to match measured clamp on reading
set AH capacity 675
set AH current state 675
compare voltage reading with digital MM

turn everything back on

saturday run full charge mode, shut down 8pm last night
before bed unplug power strip for PC/TV
parasitic down to less than 2 amps, volts 13.04

this morning Sunday 6am
SOC 88.2 percent , 596 AH, overnight use 79 AmpHr
load 3 amps, volts 12.74

this included PC use until midnight aka 11pm, no electric blanket, no heat at all
until 6am when i lit the oly cat to remove the chill

the 95 percent SOC reading is now much higher charge rate, top tapered quite as low as before, around 24amps charge rate

the big thing was the shunt 'load' reading, was reading high on discharge and low on recharge

instructions say to calibrate at the highest current you expect to measure, to test with another meter and set amps reading to match
trouble is i have no way to supply a 100+ amp steady measured DC load while adjusting the meter, so i have to settle for using my LED lights
the inverter heating MW bacon for 12 seconds, pulled 125amps above existing PC and lighting loads
will double check tomorrow