MPPT controller and PWM controller charging the same bank of batteries?

ILFE

Greetings:

I currently run a PWM (ProStar 30m) controller. I am going to purchase an MPPT 30 ampere controller (Midnite Kid) next, along with another 300 watts of panels, to expand my system.

Would I be better off splitting my panels and batteries, and running one controller on each (smaller) bank? Or, would it be fine to wire both the PWM and MPPT controllers in parallel, to a single, larger bank? I was thinking that it would be better to isolate each as an independent system from the other, no?

vtmaps

Re: MPPT controller and PWM controller charging the same bank of batteries?

ILFE wrote: »

Would I be better off splitting my panels and batteries, and running one controller on each (smaller) bank? Or, would it be fine to wire both the PWM and MPPT controllers in parallel, to a single, larger bank? I was thinking that it would be better to isolate each as an independent system from the other, no?

You can do it either way. There are both advantages and disadvantages to each way. A lot depends on your loads... does it make sense to split them into two systems?

A major consideration is batteries... If you want to use a particular battery (e.g. cheap, mass produced, golf cart batteries) but need more capacity than a single string, it may make sense to have two systems each with a single string, rather than one system with parallel strings.

Another consideration (in favor of two systems) is redundancy.

Some folks have two systems with different system voltages. Usually they started out with a 12 volt system and expanded by adding a 24 or 48 volt system (because many/most components of a 12 volt system cannot be recycled into a 24 or 48 volt system).

--vtMaps

Cariboocoot

Re: MPPT controller and PWM controller charging the same bank of batteries?

You can run two controllers of different types on the same battery bank. Occasionally it causes problems. Usually this is because the two controllers will not 'agree' on the battery Voltage and charging set points. As such you have to set one as the 'master' controller and accept that the other (usually the PWM) is only there to add to current during the Bulk stage.

The older MPPT chargers (like the venerable MX60) could become confused by the PWM's pulsing, but it seems that with improvements made to the designs that no longer happens.