Charging Issues - solar bulk charge =12.65v, alternator=14v

[sgtPluck]

Hello experts,

I have a bit of a mystery with my charging system for my AGM batteries.

I have solar panels with Victron BlueSolar MPPT Controller.

It is showing Bulk charge with a voltage of 12.65 volts while getting 122w of power and apparently putting 9.4a of current into the battery (see attachment)

That voltage seemed low to me, so fired up the engine, and my balmar a-5 regulator was showing

battery voltage 14
charge voltage 14.4

Which would seem like a normal bulk charge current.

Is there some normal circumstance that would explain why my MPPT controller would register such a low voltage as compared to the alternator? Or do I need to start troubleshooting?

Thx!

[kmacdonald]

It looks like it only takes 12.65 volts to supply the max output (9.4A) of your solar panel. As the battery charges the acceptance will decrease and that voltage should rise. It should rise to where you have set the bulk charge voltage at. It then goes to absorption stage. Depending on the SOC and bank size, it could take quite a while.

[sailorboy1]

It’s because it’s putting in as much as it can. As the state of charge goes up the voltage will go up.

The engine alternator does a higher amperage so it is higher, but it too will go up to full absorption voltage as the state of charge increases.

[StuM]

That tells you that your battery SOC is so low that it only requires 12.65V to push all of the available 122W into it at 9.4A.



If the Controller were at 14.4V, that same 122W would only be pushing at about 8.5A into the battery.

[zboss]

While I agree with the above it wouldn’t hurt to check the battery voltage at the wires on the Victron controller end at at the battery end to be sure you are not losing too much voltage.

[leftbrainstuff]

Those controllers will only charge when panel voltage is greater than 5V above your battery voltage. Is your panel voltage normal? Seems low.

[thomm225]

Your Victron Controller is working perfectly.

Your battery is still charging up to float which is usually defaulted at 13.8 volts

[kmacdonald]

Originally Posted by leftbrainstuff

Those controllers will only charge when panel voltage is greater than 5V above your battery voltage. Is your panel voltage normal? Seems low.

Nope. The panel voltage displayed is 16.21V and that's not 5V above battery voltage. Operating voltage on most 12V panels is about 17V. Do you mean 0.5V above battery voltage?

[kmacdonald]

Originally Posted by thomm225

Your Victron Controller is working perfectly.

Your battery is still charging up to float which is usually defaulted at 13.8 volts

It's still in bulk charge mode. Says so in the display he posted.

[a64pilot]

The first question ought to be want Time was it? If morning then of course it’s normal cause the battery is low and the panels can only output 10amps and that isn’t enough to get to absorption voltage.
My bank early in the morning I can throw 185 amps at it and it still takes 20 min to get to absorption voltage, where of course it comes out of bulk and current begins to diminish. This is with a generator of course.
With my Solar, I stay in bulk to at least Noon starting out with low voltage / current and eventually getting up to over 50 amps at absorption voltage, but that takes hours to get to.

[conachair]

Originally Posted by kmacdonald

Nope. The panel voltage displayed is 16.21V and that's not 5V above battery voltage. Operating voltage on most 12V panels is about 17V. Do you mean 0.5V above battery voltage?

He's half right with 5v. The controller needs the panels to get to 5v above battery voltage when the sun comes up to start up. After that it can be less as the victron works its magic.

Database snip below shows it clearly going into bulk which is mode 3 even though in this case the mains charger was on float. It's in the manual.

[kmacdonald]

Originally Posted by conachair

He's half right with 5v. The controller needs the panels to get to 5v above battery voltage when the sun comes up to start up. After that it can be less as the victron works its magic.

Database snip below shows it clearly going into bulk which is mode 3 even though in this case the mains charger was on float. It's in the manual.

Interesting. Thanks for posting that. I guess you need to make sure the panel you use with that controller has a high enough open circuit voltage start the controller.

[thomm225]

Originally Posted by kmacdonald

It's still in bulk charge mode. Says so in the display he posted.

Exactly, like I said. it's (still) charging up to float.

[sgtPluck]

Thanks for the for the tips. Sounds like all is well, but I'm still a bit confused as the manual says:

> 1.9.1. Bulk
> During this stage the controller delivers as much charge current
> as possible to rapidly recharge the batteries.

And the bulk charging voltage according to the manual and the setting I have the controller is : 14.4v. I guess what's confusing is it doesn't say anywhere that this is the maximum voltage for this phase.

So is the explanation that the maximum current (meaning amps) would be delivered at the lowest voltage that is enough to overcome the voltage on the battery?

Before the sun came up the battery was reading 12v (low for an AGM, but there was a light trickle load on it all night so I'm not sure if that qualifies as resting voltage). So in this scenario the while-charging voltage came up from 12v to 12.65 and was putting in maximum current at that voltage.

[kmacdonald]

The maximum current available was being delivered to the battery with a lower voltage than the 14.4 maximum bulk stage voltage. As the battery reaches a higher state of charge (SOC) the voltage will slowly increase until it eventually reaches 14.4 volts. If it only came up to 12.65 volts the battery is no where near full yet. Keep charging it.