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hunter44102 (Computer) (OP)
30 Jun 06 11:03
I just bought a XPower 1500 (by Xantrex). This unit contains a 60AH AGM lead acid battery and a built in 1350Watt Inverter. It is a portable and quiet generator based on batteries. It comes with an External 'float' type smart charger.

So you are supposed to charge this guy up, and then use it to power any AC power devices, or even 12V devices.

Problem is, they repeatedly state in the manual that you have to disconnect the external charger while you have devices connected or drawing power.

Is this due to the battery, inverter, or the charger?  And if so, is there a way to allow this.

The example of why I would want this, is a backup power to a Sump pump or other intermittent device. I would want to be able to keep float charging it, even though devices may come on and draw some power.

Here is the exact quote:
"CAUTION: Do not use xPower1500 to operate any AC products or DC accessories while charging with the AC Charger."
IRstuff (Aerospace)
30 Jun 06 14:34
Because you'll destroy the battery

TTFN



DanEE (Electrical)
30 Jun 06 21:03
You really need to ask Xantrex why the caution.. It's dependent upon their particular design.  There could be a number of reasons..  

A couple of possibilities....

1) You can destroy the battery as mentioned above if the charger is not a "smart" charger (meaning microprocessor controlled) to avoid getting into a situation where the charger locks up in absorption mode and overcharges the battery.

The standard 3 mode charger can not tell the difference between battery charging current and external load current and will tend to lock up in absorption mode when current is going to an external load (in your case the inverter).

Here is a reference with a little more insight on the subject. The last 3 paragraphs describe the scenario (yours) that can happen when external power is being drawn while the charger is in operation.

   http://www.ibexmfg.com/appnotes/app06.htm

2) Some small consumer inverters/UPS (with self contained batteries) are designed such that the battery as it runs the inverter, the battery is referenced up to some intermediate voltage e.g. one terminal of the 12v battery at 50 volts above ground and of course that would put the other battery terminal at 12 volts higher e.g. 62volts above ground.  

I have an inexpensive APC UPS unit that does this... It also puts huge voltage spikes on the battery as the SCRs trigger in the inverter.. simply put, this unit was not designed to operate with anything else attached to the battery or, using a larger external battery source.  Attaching an external charger could get into issues of exceeding the peak inverse voltage of the charger diodes or other insulation breakdown issues..

------------------------------------------

In God we trust. All others state the facts and cite references.

hunter44102 (Computer) (OP)
30 Jun 06 21:53
Dan - Thanks for your understanding of it, and the link. This is exactly what I was looking for.

It sounds like many of the chargers that rely on current measurements can be fooled by the load. I am guessing the Xantrex 5A model I have may have this issue.

It sounds like I may want to get a charger that looks more at voltages, or can sense load currents, like the ones mentioned in the article.
 
I know the Solar charge controllers actually have a load connection on them, at least for the lighter loads. This way it can know when there is a load. Also there is an LVD that can disconnect the load if the battery gets low.
B3188 (Military)
5 Jul 06 14:16
Essentially the load switching "On" while the charger is charging "On" makes a direct connection
from power source to your load
through the inverter ON and the Charger ON.

That is normally quite bad to do.

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