Charge Controller ?

keyturbocars

I have been planning to hook up 520W of solar panels directly to my battery bank. The battery bank voltage is regulated by a dump load. For my solar input, I plan to make up a small electrical box with a 15A ammeter, a circuit breaker, an 85A blocking diode, and then hook this up directly to my 48V battery bank.

By hooking up my 4 panels (48V nominal) directly to my battery bank and using my existing dump load system to keep battery voltage under control, then will I be losing any solar power efficiency versus using an expensive MPPT charge controller?

I know that the battery bank will pull down the voltage of the solar panel output, but will the solar amperage then automatically be boosted by just hooking up directly to my battery bank?

Hopefully this makes sense. I'm just thinking that if P=I*V and solar volts are dropped by battery bank pulling it down, then the amps should naturally go up. I might be missing something, so that's why I'm asking.

Thanks,

Ed

BB.

Re: Charge Controller ?

keyturbocars wrote: »

By hooking up my 4 panels (48V nominal) directly to my battery bank and using my existing dump load system to keep battery voltage under control, then will I be losing any solar pane power efficiency versus using an expensive MPPT charge controller?

Solar panels are, for the most part, current mode sources... Their output current from Vmp to 0 volts is pretty close to a fixed current that is proportional to the amount of sunlight hitting the panel.

MPPT works because Vmp can rise as panels get cool (subfreezing climates are ideal). P=I*V... I is fixed for a given amount of sunlight. V rises as temperature drops.

I know that the battery bank will pull down the voltage of the solar panel output, but will the solar amperage then automatically be boosted by just hooking up directly to my battery bank?

No, the current of the panel will be about the same... So, the P=V*I will be lower, because the battery is setting the panel voltage.

Hopefully this makes sense. I'm just thinking that if P=I*V and solar volts are dropped by battery bank pulling it down, then the amps should naturally go up. I might be missing something, so that's why I'm asking.

The only way to get "optimum" amount of power from solar panels is to use an MPPT solar charge controller.

Shunt controllers are typically used for Wind and Water Turbines... These guys will over-speed if there is no load.

So they are connected directly to the battery bank and use shunt controller to drain excess current/power from the battery bank once it is full...

Solar panels can be turned on and off, and be operated at less than full available power without any damage/problems. That is why people typically do not use shunt controllers--The PWM/MPPT controllers also generally do a better job of charging the battery bank than shunt controllers.

-Bill

keyturbocars

Re: Charge Controller ?

Thanks for the good explanation Bill.

mike95490

Re: Charge Controller ?

Don't forget, your panels need to produce about 63V at max power, to charge a 48V bank. Absorb is about 57V, and Equalize is about 60 or 61V.

keyturbocars

Re: Charge Controller ?

Thanks for the info Mike.