gremlinman wrote: ↑
Tue, 08 May 2018, 15:31
I am on 73.00b though. I have 8 x 12v 120ah batteries. The led was flashing.
Ah, I failed to remember that you were on 73.00b. Flashing LED, so you are in bulk or absorb. All good.
I thought it would attempt to hold 56v whilst in bulk/absorb.
Sure, it will have 56.4 V as its setpoint. It can't get there straight away, though.
I notice when I charge with generator it usually goes up from ~50v to 56v
Your generator charging must be at a fairly high rate then; a lot more than 600 W of charge power. That will get the internal battery voltage up higher sooner, but will also raise the battery terminal voltage due to internal resistance.
and stays at 56v for a while before hitting 54v and staying there putting 1a into the batteries from the generator.
Right. The time it's at 54 V and ~1 A it would be in float mode.
Am I wrong in assuming when in bulk/absorb mode the voltage should be 56v ?
In bulk mode, assuming a constant charge current, and ignoring internal resistance for a moment, the battery voltage should ramp up roughly linearly (assuming lead acid batteries) from the initial voltage till the 56.4 V setpoint, at which point it changes to absorb mode. It should stay in absorb mode until the battery current drops low, and/or the absorb time has expired (if the absorb timer is used). The battery voltage should be constant at 56.4 V during the absorb stage.
Taking into account internal resistance, the battery voltage would be higher than the figures indicated above, by perhaps half a volt to over a volt, depending on many factors. The bulk stage will still finish at or near the 56.4 V setting, however. As the charge current reduces during absorb mode, the extra voltage due to internal resistance times charge current will reduce to near enough to zero.
So for the generator to have the voltage shoot up to around 56 V nearly straight away, you really must be overcharging the lead acid batteries. Here I mean charging at too high a current, not to too high a state of charge. They should only be charged at a rate of some 13% of their Ah rating. For example, a 200 Ah lead acid battery should only be charged at about 0.13 x 200 = 26 A. Another way to look at is that it should never be charged faster than 7.7 hours (1/0.13), from empty to full. But of course, lead acid should never be discharged more than about 20%, so more realistically, it should take at least 0.2 x 7.7 = 1.5 hours to take it from 80% to 100% SOC. Don't rely on the PIP's SOC reading for state of charge; it's extremely approximate for lead acid batteries, and completely useless for other chemistries.
Now with the variability of solar charging, the battery voltage will be all over the place, but you should be able to discern a rough ramp from initial voltage to absorb setting voltage during the bulk stage, then a rough plateau near 56.4 V during the absorb stage, followed by a stay at around 54 V after that when it stays in the float stage (unless the battery voltage drops a lot, triggering another bulk/absorb stage pair). Unfortunately, the only way to distinguish between bulk and absorb modes is from the last field of the undocumented Q1 command
, though a few monitoring systems display it. But you can't tell from the front panel.
[ Edit: added "all good". ]
[ Edit: added "The battery voltage should be constant at 56.4 V during the absorb stage." ]
[ Edit: "higher than the figure indicated" -> "higher than the figures indicated above". ]
Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.