Problems changing from AGM to Flooded
For years my system has remained the same , panels feeding flooded batteries through a Morningstar TS60 PWM charge controller with a temperature sensor . Three weeks ago I changed from Flooded to Trojan AGM batteries and reduced my bank from 605 amp/hrs to 392 amp/hrs as I was struggling to maintain the 10% charge rate required and as my consumption at night was only between 60 and 100 amps my thinking was that I would still be well within the 50% DOD recommended .
new AGM batteries are giving me concerns I didnt anticipate . My
input and consumption is small but has always been consistent and
predictable however for some reason the new batteries have changed
everything . The flooded ones would not reach the set voltage around
29 volts until between 1pm and 2pm at which point I would have around
110 - 130 amps in rising through the absorption/Bulk to between
180-220 amp/hrs by the time charging ends .The new AGM reaches almost
the same voltage by around 11am by which time I have only half what I
would normally receive in Bulk . Because the Bulk charge allows all
the available current into the batteries while the adsorption charge
doesn't I am left with a decreasing input that insufficient to fully
charge the batteries in the remaining time available which was never
a problem with the flooded batteries . Previously I would see a
total of 180-220 amps/hours input , now I get only between 115-130 .
I have compared the Bulk charging amps and confirmed they are no
different than they were with the Flooded batteries so the loss isn't
there , its due to the change from Bulk to Adsorption far earlier
with the AGMs . I know these batteries have a lower internal
resistance which is promoted as a good thing but I cant see how .
hours between 11-2 when I would receive the greatest input is lost ,
by 2pm i am getting only a third of what I would have with the
Flooded batteries .
have experimented a bit to try to understand more about the situation
. This afternoon my incoming Amps were just under 10 so I turned on a
65 watt electric blanket and the incoming amps immediately went up to
just over 12 amps . My system is 24 volts and the voltage at the time
was 29 Volts as I was in Absorption . Am i being too simplistic and
naïve to assume that the increase input was because the batteries
were previously regulating the current coming is through resistance
and my turning on the electric blanket lowered their resistance to
allow the corresponding amps in or is it coincidental and wouldn't
be as precise as it appears to be , ie: sudden 65 watts out and
controller raises the input it allows in by approximately the same .
Of course I could keep a larger load on the system all day and that
would increase the amps coming in but they would be used during the
day so counter productive .
voltage shown just prior to charging while the batteries are at there
lowest is around 24.45 which from the voltage/SOC guide in Trojans
guide appears to indicate that I have cycled down to 50% .
Unfortunately I cant get a completely at rest voltage as there is
always 40 watts consumption for the Inverters self use , Internet and
a 500va UPS . I dont think 40 watts load is going to have much effect
on the voltage .
found out that these batteries need to show 0.5% end amps to be 100%
full , I cant get that low , again I don't know what effect the
40watt load makes to the end amps current either .
Victron Smart 150-70 MPPT Charge Controller
24 volt Battery Bank 4 x 6v 400 Amp/Hr Trojan L16 AGM
Victron 1200w Multiplus Inverter/Charger