How do you determine DOD?

90cummins

I'm adding a battery backup to my on-grid solar system to make it off grid capable .
It was suggested that the easiest way to achieve this is with a Schneider Electric (Xantrex) XW4024-120/240-60 Inverter/Charger.
I'm also looking at the Trojan T105RE and possibly the L16RE-A batteries.
I have used Trojans battery life calculator and the L16RE-A when discharged to 20% have a life of 4100 cycles while giving me more than my basic needs.
My question is how do I know when my battery is at 20%DOD? Does the Xantrex have an alarm that can be set to alert me?
I'm seriously considering purchasing the inverter and (4) L16RE-A thru RES Supply because there is a flat fee of $149.00 shipping on the total order.
All the other battery vendors required a core and the shipping was hundreds of dollars.
Another reason is that by using L16RE-A's I will be able to avoid a possible parallel string.
Thanks
90cummins

Cariboocoot

Re: How do you determine DOD?

If you want accurate DOD results from a meter you need a battery monitor. It keeps track of the current flowing into and out of the battery bank. There are several of these available including the venerable Trimetric, the Victron, a new one from Schneider, and the MidNight Classic's WhizBang Jr add-on (comes with them these days) which will actually control the solar based on SOC. Read about some of them here: http://www.solar-electric.com/batteries-meters-accessories/metersmonitors.html

Plowman

Re: How do you determine DOD?

I use the charge controller's outgoing voltage and amps to get a general idea of SOC, but mostly I obsessively test my batteries' specific gravity with a Hydrovolt hydrometer. It's getting bothersome. I plan on buying a Trimetric next paycheck.