Proper connections

[ChuckWmson]

I use 2 solar panels connected to a battery charge regulator, a PBR 12-9 by ETA engineering.  I have 2 battery banks with 2 6 volt golf cart  batteries in each bank.  It seems that it would work to have the positive from the PBR connected to each battery bank allowing both banks to be charged at the same time, although not as fast as connecting to one bank only.  I also use a diode to keep each bank separated from each other.

Do I have my ducks in a row or do I need to consider something else?  If a better wiring method should be considered I am open for suggestions.

Chuck

 

[Gary RV_Wizard]

I don't see a problem with the parallel wiring, but remember there is a voltage drop across a diode. That might hinder charging a bit.  Perhaps the electronics mavens can comment on the diode effects and maybe suggest ways around it.

 

[Jammer]

I don't know if I'm an electronics maven or not but I do know that you'll see a 0.7 volt drop across the blocking diode, which is enough that the charge controller won't charge the banks properly unless you have a way to adjust its voltage setpoints.

A better approach would be to use a battery isolator.  There are electromechanical ones -- big relays basically -- and there are solid state ones.  The solid state ones (the good ones anyway) use MOSFETs instead of diodes, which don't have a voltage drop across them (there is a slight series resistance).  I like ones Powerstream sells but have never actually used one, caveat emptor.

http://www.powerstream.com/battery-isolator-solid-state.htm

The advantage of the electromechanical ones is that they aren't really affected by overvoltage or brief overcurrent conditions.  They do wear over time and will eventually fail from mechanical wear, corrosion, and contact pitting.

The advantage of the solid state ones is that they don't suffer that sort of cumulative "rust never sleeps" sort of degradation.  On the other hand if you short a battery through them even briefly they're toast, a situation that will also prevail if they ever see more than 18 volts or so, even for a fraction of a second.  Pick your poison.

 

[John From Detroit]

I will go one farther than the person who mentioned the voltage drop.

When you have, as you do 2 pair of six volt batteries, there is an advantage to hooking them in parallel, also a possible disadvantage. but ... Well..  Let me explain the issues.

With the two batteries on an A/B/ switch, as you have them if you run power through diodes, the lower charged bank will be charged by the current, the higher state of charge bank will just sit there This will continue till the SOC balances then they both charge.  BUT,  when one bank runs down all the way.. Hopefully the other bank will be charged and ready to work and you know you need to charge more.

HOWEVER, there is an effect (Starts with P and I can never remember the name) which basically says "The faster you draw current, the faster still the batteries run down"

That is to say if you draw say 11 amps off a pair of six volt  They last about 20 hours. to empty or 10 till you really should recharge.

Draw the same 11 amps off TWO PAIR in parallel and it does not just double to 20 hours usable run time (40 totally dead) but more like 25 or 30 due to the slower discharge speed.


Thus I'd forget the diodes, I'd also set that A/B switch to "BOTH" and yes, I'd leave the switch in place because if one pair developes a problem.. you can thus easily isolate the bad pair till you get to ye-old- house of batteries.