Rooma 400 series only runs a few seconds

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Rooma 400 series only runs a few seconds

Postby eteq » March 10th, 2010, 2:15 pm

I have an odd problem with a Roomba Sage I've had for a couple years now... I've been on a weird schedule the past few months and really did not properly exercise my Roomba. Now, whenever I try to start Roomba on his cleaning cycle, he backs out and seems to run fine for ~ 15 seconds, and then gives up complaining that his battery is dead. The thing is, when I plug him into the charger, he blinks green within seconds, indicating a full charge.

I tried resetting the charging process (holding the power button down with the battery removed) with no affect - it took a little bit longer to get to green, but the problem is still there. I also checked the battery voltage with a voltmeter and it's showing ~ 17 V, which I understand means its fully charged. What gives? Is this just a faulty battery that can't supply current, or some other problem? I'm fine getting a new battery but I don't want to pay for it if there's some other issue...
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Re: Rooma 400 series only runs a few seconds

Postby vic7767 » March 10th, 2010, 3:35 pm

If at all possible, it would be best to perform a load test on your battery to see what gives. You can see how to do that on my website under the "How Do I" tab.
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Re: Rooma 400 series only runs a few seconds

Postby bhylak » March 10th, 2010, 5:37 pm

I suggest you try a Roomba External charger. (20 dollars) It basically eliminates to options in one: The internal Roomba charging system and the charger. Even if it turns out to be your battery, these chargers are amazing!
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Re: Rooma 400 series only runs a few seconds

Postby mfortuna » March 10th, 2010, 6:13 pm

You can also run diaganostics and see if the charging circuit is functioning properly. Check the read me first topic.
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Re: Rooma 400 series only runs a few seconds

Postby eteq » March 11th, 2010, 3:54 am

Ok, I did a load test by connecting an ~10 ohm power resistor across the battery terminals - this should have resulted in a bit under 2 Amps, but the current immediately fell to ~ 1 amp (and the voltage was ~ 11 V)... but when I removed the load it bounced back to ~ 16 V. So does this mean the battery is faulty beyond repair, or is there something I can do about it? (I'd like to avoid getting the $20 charger, given that the home base charger has been great for me...)
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Re: Rooma 400 series only runs a few seconds

Postby Jubo » March 11th, 2010, 5:08 am

If the battery is the fault, does it help to get a rapid charger???
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Re: Rooma 400 series only runs a few seconds

Postby mfortuna » March 11th, 2010, 8:10 am

The battery can not handle the load. The voltage bouncing back is normal, all NIMHs/NICADs seem to do that. You still should run the diags to make sure your charging circuit works. You could also use the lamp to drop the pack voltage down to under 10V and see if the roomba takes longer to charge the battery. Don't discharge too far or you could damage the roomba.
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Re: Rooma 400 series only runs a few seconds

Postby Gordon » March 11th, 2010, 11:48 am

Jubo wrote:If the battery is the fault, does it help to get a rapid charger???
No.
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Re: Rooma 400 series only runs a few seconds

Postby mfortuna » March 11th, 2010, 12:04 pm

Gordon wrote:
Jubo wrote:If the battery is the fault, does it help to get a rapid charger???
No.


It helps whoever is selling it :)
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Re: Rooma 400 series only runs a few seconds

Postby eteq » March 11th, 2010, 2:25 pm

mfortuna wrote:The battery can not handle the load. The voltage bouncing back is normal, all NIMHs/NICADs seem to do that. You still should run the diags to make sure your charging circuit works. You could also use the lamp to drop the pack voltage down to under 10V and see if the roomba takes longer to charge the battery. Don't discharge too far or you could damage the roomba.


I'm not sure exactly which diags you're referring to in the first/sticky post... I checked the voltage on the charger and it's exactly what the charger says it's supposed to be outputting, is that what you mean? Or should I try to measure the current coming out of the charger? Or do you mean the 72 hour reset thing (I tried and that didn't help at all). I've also noticed that the battery does get a bit warm when I leave Roomba plugged in for a while, so something is definitely happening, although I don't know if that actually means anything useful...
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Re: Rooma 400 series only runs a few seconds

Postby vic7767 » March 11th, 2010, 2:38 pm

eteq wrote: I've also noticed that the battery does get a bit warm when I leave Roomba plugged in for a while, so something is definitely happening, although I don't know if that actually means anything useful...
That is exactly what you want to discover. If while charging the battery gets warm is an indication that the internal Roomba charging system is functional. There is a portion of the Roomba Built In Tests that will also charge the battery and the result you want to receive is a warm battery. Those test steps can now be ignored since you have proven that the Roomba charging system is functional. Again it would appear that you have a duff battery. "duff" stolen from Gordon.
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Re: Rooma 400 series only runs a few seconds

Postby eteq » March 11th, 2010, 2:55 pm

Ok, unfortunate but not too surprising given how much I've abused it recently... ah well, good to know that's the problem though. Thanks for everyone's help!
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