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techntrek
If anything those temperature-compensated voltages are a bit conservative (a bit low on the high-temp side, a bit low on the low-temp side). Ironic considering how [I]over[/I]-voltaged their charges have been in the past. From the Wind-Sun battery FAQ: "It will vary from about 2.74 volts per cell (16.4 volts) at -40 C to 2.3 volts per cell (13.8 volts) at 50 C."

Which translates to 16.44 volts at -40 F, to 13.8 volts at 122 F.
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bucdup
DanB;11495 wrote:
I just dont think I could trust Generac and their battery chargers/circuits again.


Permanently scarred huh? Kind of like when your woman cheats on you.
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Canada_Guy
techntrek;11496 wrote:
If anything those temperature-compensated voltages are a bit conservative (a bit low on the high-temp side, a bit low on the low-temp side). Ironic considering how [I]over[/I]-voltaged their charges have been in the past. From the Wind-Sun battery FAQ: "It will vary from about 2.74 volts per cell (16.4 volts) at -40 C to 2.3 volts per cell (13.8 volts) at 50 C."

Which translates to 16.44 volts at -40 F, to 13.8 volts at 122 F.


On the Windsun page, there is either an error in the text or the graph on that page. The graph shows a battery charge voltage of about 2.625 volts/cell (15.75 volts) at -40F and about 2.175 volts per cell (13.05 volts) at 122F.

From the chart, it's about 13.9 volts at 32F, about 13.5 volts at 68F and about 13.2 volts at 90F.

Based on the voltages on this chart, it looks to me that the Nexus charger will be overcharging the battery (surprise).

It also seems like Generac is using some strange algorithms. Charging for 18 hours, waiting for the battery to drop in voltage, then recharging, but waiting to check battery voltage. Just seems complicated.

My experience is in standby battery systems for telecom sites and battery ripple is the death of batteries. Any form of constant charging/discharging greatly reduces battery lifespan. Temperature compensated, constant voltage is the accepted norm for charging lead-acid standby batteries.
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ohmslaw
How does the controller know if there is a battery warmer connected to the unit? Would this not skew the ambient readings?
Tim
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techntrek
Canada Guy, I see what you mean. I hadn't taken a good look at that chart before.

ohmslaw, it depends on where Generac put the temperature probe. Best place is attached to the negative battery post, second best is taped to the side of the battery. I doubt its in either location...
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ohmslaw
I assumed the probe is in the controller. It is not at the battery.
Tim
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techntrek
That's where I would assume, too. There's a lot of thermal carryover in a battery because of its mass, its temperature is more of an average of what its been exposed to for the last few days. If the generator is sitting in full sun at 9 am on a fall morning a probe at the controller might read 80 F while the battery is 40 F and the air temp might be 60 F. The controller is higher in the box, fully enclosed (even on a 75 degree day the temps inside a car can kill), with little mass. The battery is low, high mass, and is more exposed to free-flowing air.

I'd say having a probe on the controller is better than not having one at all, but not nearly as good as a battery post probe.
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rico567
I measured 14.16 VDC across the battery terminals of my 5871 10KW unit this morning about 15 min. after a test run, ambient temperature probably @ 50F.
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Skip Douglas SkipD
rico567;11544 wrote:
I measured 14.16 VDC across the battery terminals of my 5871 10KW unit this morning about 15 min. after a test run, ambient temperature probably @ 50F.
I strongly suggest that you check the electrolyte level in the battery fairly frequently - monthly would be my suggestion - and record the results of inspections and how much water you have to add, if any.

With my battery maintainer running as the only charger, I've had to add about 1/8" to the electrolyte level in some of the cells only twice in the two full years plus since I switched over to the battery maintainer.
Skip Douglas
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rico567
SkipD;11545 wrote:
I strongly suggest that you check the electrolyte level in the battery fairly frequently - monthly would be my suggestion - and record the results of inspections and how much water you have to add, if any.

With my battery maintainer running as the only charger, I've had to add about 1/8" to the electrolyte level in some of the cells only twice in the two full years plus since I switched over to the battery maintainer.


Thanks, Skip. I'll put the electrolyte check on my monthly calendar. If I did find out I was overcharging / having to add significant water each time, how would I disconnect the Generac charger so that only the Schumacher (or etc.) battery maintainer was not getting unwanted "help?"
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genme
rico567;11546 wrote:
...how would I disconnect the Generac charger so that only the Schumacher (or etc.) battery maintainer was not getting unwanted "help?"
As far as I know, no one here has volunteered an answer to this question, yet. We're dealing with a charger built into the control panel on the Nexus Air-Cooled units. Hopefully, someone will be able to analyze the wiring diagrams and come up with an answer.
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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rico567
genme;11547 wrote:
As far as I know, no one here has volunteered an answer to this question, yet. We're dealing with a charger built into the control panel on the Nexus Air-Cooled units. Hopefully, someone will be able to analyze the wiring diagrams and come up with an answer.


This sounds par for the course with a lot of modern circuitry. If we're very, very unlucky, the charger will be integrated with the controller sufficiently that it will be very difficult to cut it out of the loop.....and however it might be done, I'd bet money that it will void the warranty.
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ohmslaw
genme;11547 wrote:
As far as I know, no one here has volunteered an answer to this question, yet. We're dealing with a charger built into the control panel on the Nexus Air-Cooled units. Hopefully, someone will be able to analyze the wiring diagrams and come up with an answer.


Removal of the T1 fuse will disable the nexus charger. I personally would let the Nexus charger do it's job.
Tim
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