I’ve recently purchased a logomatic v2 and 1100mAh lipo cell for a gps logger project. All went well for the first two uses. But I only had 5min use the third time I switched it on.
So I performed a few tests, as I’m not sure if it’s a battery fault or the charge cct in the logomatic.
While charging, the logomatic draws 230ma, but there’s no voltage across the battery and the charger chip gets hot. Disconnecting the battery the logomatic current drops to 20ma, and the charging chip cools down.
Can I conclude from this, that the battery is at fault?
Looks like it’s a dead short.
Thanks guys, unfortunately it’s developed into that most dreaded fault, “the intermittent”
It’s now charging OK, I’ve no idea what I did, it suddenly came good. So obviously the battery couldn’t have been shorted. I’m just peeved with my self I didn’t think to measure the current into the battery while it had zero volts across it.
My thought now is the protection cct inside the battery, could that conduct 230ma without cooking???
And Guys, I don’t see how it can be the logomatic that’s faulty. It’s putting out charging current, but there wasn’t any battery voltage. Not even a mv absolute zero. Which also doesn’t make sense, what device can be at 0v with >200mA flowing through it, and still recover to work properly?
Unless of course, that 230mA isn’t going into the battery, but that is unlikely as the current dropped to 20mA when the battery was disconnected.
I guess I’ll have to wait on this and see if it happens again. Then I will measure current into the battery, and also see if I can swap some devices around.
Given what you are saying about batteries and voltages I have to ask. Where are you measuring the current and voltage, and how are you measuring current?
I’m measuring voltage straight across the battery. The current is what
the logomatic is drawing through it’s usb connection, I have a USB
tester in series with it. I’ve previously checked this device and
found it’s accurate enough.
As I said I’m vexed I didn’t think to put the multi meter across the
battery switch, to make sure where the current was going. I’m just
assuming, that because the current into the logomatic dropped, when
the battery was disconnected, that the current was going into the
battery.
I used it again yesterday, and it charged up OK.
But, I have one beef about the logomatic, it doesn’t appear to indicate when the battery is fully charged.
Battery voltage gets to 4.18, the current into the logomatic drops to 80mA and there it sits.
When the fault was on, the charge light went dim, so I assumed that was the fully charged indication, but I now think it was just the zero volts across the battery pulling everything else down.
It does seem strange battery charge behavior, but if everything is working other than the LED charge indicator turning off perhaps it is working as intended. I have encountered a couple lipo charge boards that just show the ‘battery charge’ light whenever USB is connected.
No Stephen, I only had 5mins use before the battery cut out, and there
was definately zero volts across the battery when i was supposedly
being charged. It definitely wasn’t working as intended. And now the
fault isn’t there. The charge light stays fully lit all the time it’s
plugged in to USB. There appears to be no indication of charge
completion.
If the problem is intermittent it could be the safety circuit built into the battery there are some that will shut down the battery if they got too hot/too much charge and need to be removed from the circuit before they will reset.
Just a note of warning, Never measure the current on a LiPo battery(Or really any battery) with a multimeter in ammeter mode without some resistance in series to keep the current to acceptable level. An ammeter is an effective short circuit so it will damage your battery and multimeter.
I’m talking about measuring the charging current, meter in series with
battery and charger.
And I had suspected the safety cct in the battery.
I had a close look at it today as previously suggested, and there do
appear to be a few loose strands of wire where the +ve red lead exits.
It doesn’t look like it can short against the black -ve lead though,
the insulation on that seems intact.
I had another problem today however that could be related. I hit a
very solid lump of accumulated weed while windsurfing and came to a
very abrupt stop. -10m/s/s says the GPS. The first file stops at that
point and a second file starts 2 seconds later. I’m fairly sure this
can only happen with an interruption to battery supply, Although there
are “stop” and “reset” buttons on the logger, it’s not possible to
accidentally activate them.
So this looks like a loose connection somewhere, or less likely a short?
That could also be the battery protection the circuit built in is also designed to protect against over discharge so when you hit the weed the motors may have tried to pull too much.
Sorry, did not mean to imply you were stupid, I am a Lab demonstrator for second year Electrical Engineering students so I have learnt never to assume that people know where the danger is.
Fair enough Clinton, we can never be too cautious, people’s feelings
are secondary to major burns.
No motors drawing current this is windpower.
It was a very sudden stop, I got thrown over the front of the
windsurfer, and landed in fairly shallow water. The GPS logger is
mounted on my head. It didn’t receive any impact, just a sudden
deceleration. Enough to activate an intermittent short?
A battery short could explain both symptoms?
The protection cct cuts in, battery voltage drops to zero, but the
charger still draws current
Yeah, it seems as though something is a bit more sensitive to movement than you would like. Is there something else you can power with the battery that will test to see if it id having the issue?
My thoughts exactly. I do have another DIY logger but physically it’s
set up very differently.
It would be a major reconstruction to swap batteries.
So I’m thinking maybe a light of some sort, with a solid attachment,
that I can shake about a little?
I’ve had several sessions now and the unit has behaved perfectly, so maybe I fixed it, when I ran the iron over a slightly suspect looking solder join to the board battery connection, I’m not sure. But I think I’ll shelve this problem unless it reappears. Thanks for the help gentlemen.
I had 3 files the other day, so the problem hasn’t gone away.
So I opened it up and had a play with it. Found the logomatic is sensitive to pressure. Maybe a cracked track or a dry connection? Trouble is it’s very hard to isolate, applying pressure anywhere can stop the logomatic recording, (buffer leds stop blinking).
30 nov, Think I’ve fixed the problem, there was junk in the gps socket and the plug wasn’t seating securely, after rectifying that I’ve had no more problems.
All I need now to make it a really good unit, is reduce the current
draw of the logomatic. I’m sure it’s doing a lot of things I don’t
need and it’s about three times the drain of the openlogger.
