Bulk charge

[Sylvain]

Hello everyone,
I just got a new charge controller for my portable solar panel.  This charge controller allows me to adjust bulk/float charge voltage.  I was wondering if I should set the controller to bulk charge up to 14.4v then above that it would float charge or should I set the bulk charge to 13.7v then float charge?

Thanks!

[DavidM]

What type of batteries do you have and how many? The answer to your question totally depends on that. Also what is the brand and type of your solar controller? Even though some let you adjust charging parameters individually, they usually have default settings for FLA, AGM, Gels, etc. that work fine.

David

[Sylvain]

David, the battery is a brand new Rolls 130ah flooded acid battery (not sealed).  We have only one.  The controller is a Chinese PWM charge controller and it's only for our portable solar panel.  The default setting for the FLA was 13.7v for bulk charging. 

Thanks!

[Merlin]

I looked up the specs for that battery and it needs a higher final bulk voltage at 14.7V. The voltage will start lower than that. Charging is usually accomplished in 3 stages by the controller. In the bulk stage the current (amps) input is held constant at the maximum available until the battery reaches it's bulk stage end point, which for the Rolls is 14.7V.  After the bulk stage, the controller should have an absorption stage where volts are held constant while the battery finishes accepting all the current it can take for a full charge. In the absorption stage the current gradually declines. The controller then enters the float stage where the volts "float" around 13.7V or so until power is needed from the battery. This is all a bit complicated with a battery that's in use, because use affects the voltage. For example, a battery under heavy use will never enter the float stage and may not even make it to the absorption stage unless a great deal of current is available (i.e. a lot more amps available than are being used).

Ok, so much for theory........check out the Rolls 130Ah group 31 12V battery specs yourself and see if the controller can be adjusted to make the battery happy. 

[Sylvain]

That's great information!  Thank you so much!  It looks like the charge controller can be adjusted to 14.7v.  I just hope it can deliver it though!  We have an inboard mppt charge controller which controls the charge of the panel on the roof of the CL.  This mppt charge controller doesn't have any adjustment but I believe it has a bulk charge end point of 14.4v which is quite close to 14.7v.  The sad news is that our converter (PD4540 I believe)will only charge it to 13.7v when plugged to shore of course.

By the way, the cheap Chinese PWM controller that we use with our portable solar panel has a small ldc screen which tells me the voltage of the battery but it doesn't tell me how many amps are going in the battery.  Is there a way to mesure that?  The portable panel is 120w so I should read around 7A when in full sun.

[kortm]

As for me, it's a great solution that uses solar panels in the RV. I researched some blogs and found this one interesting https://websolarguide.com/am-solar-flagpole-light/