Suggestions on shutting down a system?

santaigo · June 2011

I'll soon be installing my PV system in Baja, we visit for a week or so at a time, 3 or 4 times per year. That means that for two or three months, the system is not being used. How should the system be configured when I leave? Assume that there will be no one available to check the system while we're gone.

Two 195 watt 12v PV
Xantrex C60 charger
two, maybe four, 6 volt golf cart batteries, wet
Xantrex MSW 1500 watt inverter/charger

My normal MO is to leave early in the morning, but this means the batteries would not be fully charged if I shut everything down. I do have available a 15 watt 12v panel from an old Harbor Fright system that maybe could be used in some way.

Here are some suggestions I've received so far:
1. Turn everything off after fully charged and hope for the best.
2. Turn 12v disconnect off and leave charger on - should hold at float.
3. Get a small PV designed to trickle charge.
4. If only two batteries, take them home with me and keep them charged.

How do you guys handle this?

BB. · June 2011

Re: Suggestions on shutting down a system?

The end goal--to keep the batteries >75% state of charge while unused... However you achieve that goal is fine.

So, my suggestions:

Charge with genset until >80% state of charge; leave on solar panel for float charging:

4 batteries * 6 volt * 225 AH golf cart * 1/0.77 derating * 0.01 float charger = 70 watt minimum solar array for float charging

Recharge batteries to 100% state of charge and come back every 1-3 months and recharge.
Leave one of your 195 watt solar panels on roof for float charging.
Take batteries home and place on good quality float charger or cheap charger with lamp timer set to charge ~1 hour per day to keep float charged.

Note that keeping the 4x batteries on a 70 watt panel is very close to not needing a real battery charger--but if you are worried about theft, get a very inexpensive 8-10 amp charge controller with the 70 watt panel.

-Bill

Cariboocoot · June 2011

Re: Suggestions on shutting down a system?

Missing information: how long will you be away? One month? Six?

Normally you just make sure the water is topped up, shut down the inverter, and leave the charge controller & panels hooked to the batteries. Since there is no use, the daily recharge will be very short and the batteries will stay in Float most of the time. In your hot climate there is possibly more concern with water loss. A temp sensor for the batteries is a must. If you leave for a long time without charging, the self-discharge of the batteries could be serious, even if you could charge before going away.

This is an instance where AGM's become an attractive option.

SCharles · June 2011

Re: Suggestions on shutting down a system?

Cariboocoot wrote: »

Missing information: how long will you be away? One month? Six?

Normally you just make sure the water is topped up, shut down the inverter, and leave the charge controller & panels hooked to the batteries. Since there is no use, the daily recharge will be very short and the batteries will stay in Float most of the time. In your hot climate there is possibly more concern with water loss. A temp sensor for the batteries is a must. If you leave for a long time without charging, the self-discharge of the batteries could be serious, even if you could charge before going away.

This is an instance where AGM's become an attractive option.

I agree. Why not just leave the system operating, without the inverter? If your batteries can be so fitted, I would suggest some HydroCaps. With them, I add water to my batteries twice a year and, at that, only a very small amount.

But, in any case, I don't see why you cannot leave the panels and controller working away.

techntrek · June 2011

Re: Suggestions on shutting down a system?

You definitely don't want to leave them disconnected for 2-3 months over the summer. Self-discharge will take them into the danger zone before you get back. In the coolest winter months you might get away with that time period, but a quick check online says even then you are between 45 and 68 F which isn't all that cold. Those are only averages so you could go much warmer. Heat buildup inside a closed up building sitting in the sun would put you back in the danger zone even in winter. So I don't think onsite storage is an option for you if you must store your PV array when you leave.

If theft isn't a worry, as others have suggested leave the batteries connected to the charge controller and PV. All year long. If you must take the PV array down you'll have to take the batts home with you. If your place is in the shade you might get away with leaving them there over the coolest 3 months.

rplarry · June 2011

Re: Suggestions on shutting down a system?

When I leave for the summer months, I leave my panels, cc and batteries on so that they get charged every day. I use agm batteries so water usage is not an issue. In your case either take the batteries with you or water them up as they are supposed to be and see what happens.
Larry

icarus · June 2011

Re: Suggestions on shutting down a system?

As all have suggested, leave it running, turn off th e breakers for the loads. Top up the water. If you are worried about too much water loss, buy hydro caps, or build an auto watering system.

Try to keep the batteries as cool and as well vented as possible.

Tony

Suggestions on shutting down a system?

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