Strange battery behavior

[boywonder]

So.....I've got a typical setup with two 175AH AGM batteries for house batteries, and the stock motorcraft starting battery with a Blue Sea 7610 ACR.

300W of solar, Samlex controller wired to the house batteries, Xantrex LinkPro battery monitor wired into house battery ground.

Here's the symptom.....

Over time, even on long sunny days with plenty of solar watts, my battery monitor shows the batteries at say 95% even though the solar controller is clearly in float mode with little to no amps flowing.

I've convinced myself that the controller is in float mode by turning on a big load (like electric water heater) and watching the solar controller bump the amps way up if in full sun, as expected.

If I synchronize the battery monitor, it will once again say 100% then over the course of a few weeks it drops back down to say 95% or so. I've resynchronized several times over the past few months...same thing.

It would appear that the house batteries are going downhill fast, since by now I'm at 95% x 95% x 95% = 85% each time that I have synchronized.

I was thinking that perhaps the starting battery was dying so I opened the breaker joining the banks but the starting battery seems fine....

any ideas???

[rallypanam]

I have the same issue with my Xantrex. It actually says something on the screen like "resynch" or somesuch. I don't think it's the batteries, I think it's the monitor.

[boywonder]

Originally Posted by rallypanam

I have the same issue with my Xantrex. It actually says something on the screen like "resynch" or somesuch. I don't think it's the batteries, I think it's the monitor.

Exactly......

[rallypanam]

If you're lazy and ignore it, it keeps going down.. I think mine says 80% now, even when the battery is definitely full.

[ShuttlePilot]

I would suggest two possible scenarios if in fact batteries are healthy and all other equipment is operating properly.

1. Your solar controller is switching to down float voltage and not allowing a long enough absorb voltage to complete a full charge. This is common in a lot of charge controllers.

2. Your charge monitor's correction factor is a little off. It takes a more watts of energy in charge to replace each watt of power taken from the battery. Monitors correct (or make an assumption) to calculate that. One scenario where this looks like a big error is large temperature swings between when a battery is discharged and recharged and vise versa.

I'd dive deep into the instructions of both devices if something isn't obviously wrong elsewhere in the system.

Eric

[boywonder]

Originally Posted by ShuttlePilot

2. Your charge monitor's correction factor is a little off. It takes a more watts of energy in charge to replace each watt of power taken from the battery. Monitors correct (or make an assumption) to calculate that. One scenario where this looks like a big error is large temperature swings between when a battery is discharged and recharged and vise versa.

My house batteries are inside....near the controller, and I've got the controller temp compensation probe on the batteries........can't think of what else I could do here....

[Flux]

Can you adjust parameters on the solar charger?? I know the Bogart has a setting for different batteries and such things as a % Overcharge and % Finish Amps.

[JFlo]

I get some weird read-outs on my LinkPro monitor as well from time to time that I know are incorrect. So far, I'm not impressed with this unit.

[boywonder]

Originally Posted by Flux

Can you adjust parameters on the solar charger?? I know the Bogart has a setting for different batteries and such things as a % Overcharge and % Finish Amps.

...just float and bulk charge voltages...

[Scalf77]

I am kind of inline with ShuttlePilot. I believe the key parameters that target the linkpro to think it is fully charged are:

• F1.0 Charger's float voltage (Auto-sync parameter). This value must be equal to your battery charger’s float voltage. which is the last stage of the charging process. In this stage the battery is considered full.
  Default: 13.2V Range: 8.0 – 33.0V Step size: 0.1V
  
• F1.1 Charger's float current (Auto-sync parameter). When the charge current is below this percentage of the battery capacity (see Function F5.0), the battery will be considered as fully charged. Make sure this Function value is always greater than the minimum current at which the charger maintains the battery or stops charging.
  Default: 2.0% Range: 0.5 – 10.0% Step size: 0.1%
• F1.2 Auto-sync time (Auto-sync parameter). This is the time the Auto-sync parameters F1.0 and F1.1 must be met in order to consider the battery as fully charged.
  Default: 240sec Range: 5 – 300sec Step size: variable

Make sure the float voltage the monitor expect to see is the same thing being provided by the charger, Do you have any high always on loads that might be outside of the minimum current at float.

The obvious, which you probably already checked, make sure there are no loads that do not go through the shunt.

See if your charger let's you change the absorption parameters, some chargers let you adjust the minimum time and other parameters.

Happy Hunting
-greg