road-runner wrote:
red31 wrote:
Trojan Battery's response...... the current must be lowered before the batteries reach a voltage of 2.35 volts-per-cell
2.35 * 6 = 14.1 . Am I wrong to interpret that as saying 14.4 at the battery, the common boost voltage, is too high? And no mention of battery temperature vs. voltage, either.
IMO the tech is not speaking accurately, that's all. You can't reduce what amps the charger is doing, but the battery itself does that, by having an "acceptance rate" for a particular voltage at a particular SOC. At any particular voltage, as SOC rises, the amps acceptance rate goes down--ie amps taper.
The acceptance rate in amps is higher with a lower SOC, or a higher voltage. As seen in my ugly graphs, the acceptance rate starts to go vertical to the left, so it is a case of diminishing returns to go higher amps at say 50% SOC once you are close to the vertical part.
The other thing that is always missed, is that the so -called constant voltage, Absorption Stage, is not at the battery, but at the charger. The battery does not reach the charger's voltage until the very end, and not even then really, when no spread between the two voltages means no more amps flow.
Once amps taper due to the battery acceptance rate at whatever SOC--(higher charging rate sooner at a lower SOC), battery voltage continues to climb towards the charger's voltage. The charger is what has the constant voltage as set for its Vabs, not the battery.
(y ugly graphs are with a 220AH bank with Vector chargers that have a pre-set amps tapering at 14 volts on the battery. So amps taper a bit earlier than you would see with a charger that went higher before amps tapered. However, the charger voltage keeps rising instead of staying constant, which keeps the amps higher during the absorption stage, so the over-all time it takes to do a 50-90 comes out even with a charger that lets things go a bit longer before amps taper. therefore the ugly graphs are still about right for regular, non-Vector, chargers.)
You can use the graphs for other size battery banks with the same amps of charger. It is proportionate. Double the AHs, double the time. 1/3 more AH and 1/3 more time, etc. However, as seen, you do not halve the time by doubling the amps!!! Diminishing returns on that.
So if you like 70 amps on 220AH, you can get the same gen time by using 140 amps on 440AH. It is all in proportion--and that is true whether you have AGMs or Flooded.
The usual limiter is your generator. It can only do so much in VA, which can only run so much of a charger (more in amps if the charger is PF corrected) So your gen time calculation starts there with the charger amps you can do with your gen. After that, it is all about how much battery bank you have in AH and how far down it is. Whatever, you would never try to go above 90% on the gen unless you are crazy :)
I have a Honda 3000 running 155 amps worth of chargers, and that's that. So my gen time is shorter with a 4 battery bank to do a 50-90 than with a 6 battery bank and a 50-90. I can't use more charger amps with the 6 batts, because the gen can't do that. It is maxed. that is my limiter.
