I had indicated in a previous thread that I had some interesting observations when testing out some new software that I had written to show all of the data from my Xantrex XBM Battery Monitor on my 7Ē touchscreen monitor used in my Carputer system in the SMB.
Essentially after starting the van and the PC boots up I can look at what is going on with the house battery system. The biggest indicator is the current going in or out of battery. For my observations I concluded that a positive charge indicated that the Surepower separator had closed, while a negative charge meant that it was open (I will consistently pull about 4+ amps with the computer and accessories running). I have no solar so when unplugged my only source of charge comes from the vanís alternator. The start assist circuit is not connected to work all the time.
Day One Morning- Unplug van after starting and boot-up I show a small positive charge. Both Van Battery and House battery show relatively the same voltage (House is measured off XBM,Van is measured off of Scan gauge). Drive to work, a little over half hour, the Surepower remains connected the whole drive.
Day One Evening - It appears that both the House Battery and Van Battery are sitting at 12.9 volts ( I am using the cigarette lighter voltage meter , scan gauge is not on yet). Crank it up and after the system goes through booting, etc, I see that we have positive charge on the house battery and the voltage between the house and van are the same. Assumption, the separator is connected, the question I have is did they ever separate (they are supposed to separate at 12.8 +/- 2%). Without some further instrumentation I have to assume they were still connected. While driving home I put some of the charge lost during the day (refrigerator on). The voltage starts out around 14 volts and I am getting about a +5amp charge on the house battery. As I go home the voltage creeps down as does the current. I get home and do not plug in; we will let it sit overnight.
Day 2 Morning, check the voltage again, the XMB says the house is 12.87 the van battery is saying 12.8 (resolution only goes out 1 place). Anyhow the results were the same as yesterday evening, started up the van and I had a positive charge of about 5 amps. Voltage 14.0 to 14.1. Again as I drove to work the voltage went down and the charge reduced accordingly.
Day 2 Evening, check the van, the XMB says 12.7 the van says 12.8. I crank up the van and when everything is up and running I have about a 4.5 amp discharge on the house battery. This is in line with the consumption of the computer; I will also see it go up to 7.xx amps when the Norcold kicks on. The voltage has dropped slightly to 12.5 with the draw. Meanwhile the van battery voltage is reading 14.x volts and as I drive home it starts its gradual creep down as the van battery gets recharged. Just by the time I get home (roughly a little over Ĺ hour) I see the voltage around 13.4 Ė 13.5. The separator appears to engage as I now have a positive charge going to the house battery of 10 amps. Unfortunately I am pulling into my driveway, so I shut it down and again do not plug in.
Day 3 Morning, I check the house battery and it 12.67 volts, the van again is at 12.8 volts When I crank it up, again I see the same results as yesterday evening. There is the a discharge on the house battery of 4.5 amps and the van battery sits at 14.1 it again goes down as I make my drive to work. Again as it appears to get close to 13.4 volts on the van battery the separator kicks in. Unfortunately I have just arrived at work and I shut it down.
Day 3 Evening, A repeat of the morning, the house battery is a little lower the big difference is that I donít see the van battery ever get back to 13.4 before I make it home. By now the house is around 12.5 volts. So I decide to plug in for the night.
Day 4 Morning is a repeat of day 1 morning; we start out charged and remain connected
Conclusion - debate. While they say that the batteries will connect when one goes above 13.2 -13.5 volts there is also a statement about protecting the charging system from excessive load. It really appears to me that the separator really kicks in after it falls back below the 13.2 to 13.5 volt range. I did not actually time the event so it is possible that it is possible it is truly on a timer, although I doubt it.
While this may not be a huge issue, it does make an impact in my usage model. Typically in the summer I would also have the Starcool turned on at the same time. That means my current draw would be pretty large while I waited for the van battery to charge back up, and the van voltage to go below the 13.2 to 13.5 threshold. I donít think there are issues with my alternator providing enough as the Surepower originally had the start assist wired to the run circuit which basically meant it was connected while the van was running.
It may also mean that if you have a bad starting battery that your alternator will never drop back below 13.2 to 13.5, in that case you would not be charging the house batteries as expected and it may seem like the Surepower is not working.