Outback Charge controllers/Xantrex Sinwave + invertor/charger

Re: Outback Charge controllers/Xantrex Sinwave + invertor/charger

Some reading:

Deep Cycle Battery FAQ
www.batteryfaq.org
Trojan Battery User's Guide (English)
Trojan Battery User's Guide (Spanish)

Does the SW+ provide constant charging? Should I turn on EQ Charge? Am I correct in my assumption that the Outback Charge controllers only collect PV voltage and maximise to SW+, and SW+ charges Batteries and with enough stored energy, Inverts to A/C?

The Inverter/Chargers only charge if you have the generator up and running--Normally, with the price of fuel, you will want to minimize runtime, so a good way to do this is:

We normally recommend generator charging if the battery bank is below ~75% state of charge and you have cloudy weather forecast--start the genset early in the morning and run to get the batteries back above 80-85% state of charge (below ~75% state of charge, batteries "sulfate" fairly quickly and if left for days/weeks/months below ~75% state of charge will lose capacity).

If the batteries are below 50% state of charge, start the genset right away to get them recharging. Batteries discharged often below ~50% state of charge will have less cycle life.

If the batteries are below 20% state of charge, stop any loads and get them recharged... Below 20% state of charge, it is possible to take a weak cell dead and even "reverse charge" a cell which will cause it to fail now or in ~1-2 weeks).

If I understand your questions correct.... Think of the battery as the heart/center of your power system. For a first approximation--The Outback charge controllers take solar power and send it to the battery bank:

• Bulk: When batteries are low, will send out as much current to the batteries as it can (maximum of solar array and maximum output rating of charge controller--depending on sun and # of watts of solar panels). Bulk will continue until the batteries are ~80-90% charged.
• Absorb: When batteries reach charging set point (around 57-59 volts), the charge controller will hold the charging voltage and the batteries will naturally limit the charging current to smaller and smaller amounts. Down to ~1% of Bank AH capacity (i.e., 500 AH battery bank, ~5 amps minimum current when bank is full). Outback can be set to time the Absorb cycle to ~2-4 hours... Useful to not confuse charge controller if you have other loads running at same time.
• Float: Battery is fully charged... Controller will back down to ~53-55 volts. Batteries can sit at this voltage "forever" and not be over charged or slowly discharged.
• Equalize: Batteries are "overcharged" to get weak cells back up to fully charged... Will not "fix" batteries with problems, but will recharge a weak cell in a series string of fully charged cells. Too often/much equalization will damage/quickly age a battery bank. Read the Trojan manual about when to equalize (or your battery mfg's manual).

And for inverter loading--look at the battery bank directly... How much charging the solar charge controllers are doing (or not) should not affect the day to day operation of the inverter(s) unless you get to their cutoff voltage (typically around 42 volts). Normally though, you should not be taking your battery bank below ~46 volts in normal day to day operation.

If you have a lot of parallel batteries (personally, my recommendation is to avoid more than 2-3 maximum parallel battery strings--more strings become difficult to keep sharing current equal. If you can, get larger AH batteries and keep the number of parallel strings down (to one--my preference--However, that may not always be possible).

I would suggest getting a DC Current Clamp Meter (here is one model that is inexpensive in the US--about the minimum price I have seen that will do the job. $60 USD... Otherwise, you can spend $300-$400+ for a very nice Fluke or other good quality True RMS reading meter).

Use the current clamp meter to measure current (during heavy charging/discharging) in each parallel battery string every week or month... If you see a string that is not sharing current with the DC current clamp meter--you know that something is wrong and can fix it before the batteries fail.

You can also use a digital volt meter to monitor the voltage at each battery to make sure they are reasonably matched in voltage. And even check each cable voltage drop with the 2 volt or 200 mV scale (if too little drop, perhaps not enough shared current flow; too much drop, perhaps a failing cable/cable connection).

Lastly, with lots of parallel strings of battery banks--each back should have its own fuse/circuit breaker. This will help prevent a shorted battery from catching fire by pulling huge amounts of current from the other batteries strings.

I will stop here--lots to read and I am sure you will have more questions.

-Bill