Care and feeding of my batteries while I am on vacation?

[Clifford]

Ok,

I am planning on taking a week or so off this December.

I have a small array...

4. x deep cycle batts...
   
6. x Siemens 48's.
   
   

So far, my max charge has be a bit under 20 Amps hrs a day, with generally less than 4 amps max in the early afternoon.  Still hoping it will be better next summer.

I believe that I am running around 70% - 80% charged on the batteries, but it is hard to say for sure because of the big plateau in the charging curve.

So...  here is the dilema.

My charge controller seems to draw 3-5 watts off of the batteries, and seems to be incapable of running off of solar power only.  I really don't like that aspect of it.

What happens if I get a foot of snow (or an inch of freezing rain, or a combination of the two) with the panels plugged into the charge controller.  Hopefully it would sluff of in a couple of days...   But, there would be the risk of running the charge controller for a week while generating ZERO POWER, and slowly draining my battery array.  Probably not enough to be critical...  but certainly enough to be frustrated coming home to a dead array that could take a month to recover at my rate of charging.  It wouldn't be a good scene.

I could split off a smaller array of panels...  say 1, 2, or 4 panels which should effectively give me trickle charging around 1-2 amps max distributed over 4 batteries.....   Probably hard to over charge them on that.  A diode, of course, would protect me from discharging, and I would hopefully come home to a 100% charged array.  And, there wouldn't be a worry about snow.

I guess the last option is to throw the isolator switch on the battery array, and basically do nothing while I'm on vacation.

What are other's thoughts?

Thanks,

Cliff

[TomW]

Clifford;

I say just top them off good before you leave and disconnect the batteries from the controller and the controller from the panels. They should be fine sitting a week if fairly well charged. I would be concerned with the controller seeing high volts from the panel with no battery load is why I would unhook it from the panels if no batteries are in circuit.

I don't know your panel specs or your battery size so cant say if I might approach it differently. But, if you have 1000 AH of battery charged by less than 30 or so amps you could just let it charge the whole time with just a blocking diode and eliminate the controller. Sure seems like you could safely push 10% of your AH rating into batteries with no ill effects for a week from solar with no load. Especially in winter.

Just my opinion which may not be held by others.

Cheers.

TomW

[Nando]

The charge controller should not draw that power from the batteries.

A good charger should draw a maximum of about 500 micro amps or less ( the resistor network to set the charger controller voltage limits).

Like Tom says, it is best to have the battery bank disconnected for the week or so you will be away --- make sure that the batteries are charged prior departure and isolation.

Nando

[ghurd]

The controller should be able to handle open circuit volts from the panels.

I would just throw the isolater switch, or pull out the fuse between the battery and controller.

But I am lazy.

What kind of power-hungry controller is that?

Sounds like it is using 2%, 24/7, of the peak amps. 2% x 24 hours= 48%, 4.5 solar hours a day... Thats 12% of the daily power just to run the controller?

That is bad.

Maybe try a Morningstar SS-20, and not have to worry anymore?

First cup of coffee, so I might be wrong.

G-

[tecker]

  I would consider a full checkout of the conttroller . Sounds like a bypass circuit would give you some extra power and a good idea of what your panels can

produce . If on a good day you get a the batteris topped off the controller has to go.

[wine_guy_3]

I'm confused.
Wouldn't the controller just stop charging when the batteries are full? say 13.5 or 14 volts?

[mab]

this is a very old thread!

But reading the OP suggests that the controller wasn't over-charging the batteries, but that the issue seems to have been that it was draining the battery significantly even when there was no solar input.