Open circuit on battery charger

[carparkthrasher]

Hi all,

Further to recent build weekend, thought I would dust off the EMaxx for some bonkers bashing while letting the paint dry on Blitzer Beetle. So I gather up my chargers and my 4 x 4500 NiMh Orion Rocket Packs with TRX connectors and set about charging them up. Now, these batteries are under a year old and have sat unused for about 3-4 months but have worked well in the past. Setting them up this time however, results almost immediately in an 'Open Circuit' error and the charger then standing down. Chargers all work well, Pro Lux 104 and this error is the same you would get if nothing plugged in, battery wise. I use a TRX to Tamiya adaptor so I tested all of these out with the dinky 1200 stick packs you get with Traxxas 1/16 cars and they work well so it has to be the batteries themselves. However, to have all 4 go has confused me!

My best guess is something wrong with the connector or wiring - ends look OK with minimal or no corrosion as these have never been through deep water like some of my packs. Wires seem OK and haven't got obvious breaks in them and through the clear shrink wrap, I can't see anything to horrendous. Any thoughts folks? The batteries came from Modelsport and they also did the install of the TRX ends and these have performed beautifully. What could have gone wrong internally to effectively sever all connections coming out of the stick pack?

Your time starts...............now!

Thanks!

CPT

[TA-Mark]

What charge state were the packs left in for storage? Should be around 40% charged.

Check the charge state of the pack with a multimeter/voltmeter. The voltmeter will also indicate if the plug has a bad terminal or a wire off.

[carparkthrasher]

What charge state were the packs left in for storage? Should be around 40% charged.

Check the charge state of the pack with a multimeter/voltmeter. The voltmeter will also indicate if the plug has a bad terminal or a wire off.

To be honest I probably dishcarged them to around 6.3 (as they are 7 cell packs, 8.4 volts) so 0.9 per cell, on the basis that I would be using them within a couple of weeks! Well, you know how plans change! So could it be that I have wickered them up somehow?

Forgive my ignorance but what is the best way to leave them charged to 40%? Run them down then charge them a 1C as normal but stop it at 30 minutes or so?

Thanks for speedy reply BTW!

[Backlash]

My guess is that your batteries have died..

What can and does happen with the larger capacity (4000mA+) NiMh batteries is that they self discharge if left sitting for a while.. This is why it is recommended that NiMh batteries be left partially charged if stored.. If the packs are left stored too long, then the cells can self discharge down to zero volts, and when this happens it usually results in those cells not wanting to accept charge anymore..

I would suggest that is what has happened to your batteries when you stored them for 3-4 months, and now each one has one or more dead cells..

If you have a digital multimeter, you can test the voltage at the traxxas connector, and also accross each cell to see how many have died.. With any luck you will have enough cells still working to make one or two packs..

[WillyChang]

own a multimeter?

probably broken chargelead, or possibly cracked a dryjoint in charger somewhere eg between PCB & case socket

[carparkthrasher]

My guess is that your batteries have died..

What can and does happen with the larger capacity (4000mA+) NiMh batteries is that they self discharge if left sitting for a while.. This is why it is recommended that NiMh batteries be left partially charged if stored.. If the packs are left stored too long, then the cells can self discharge down to zero volts, and when this happens it usually results in those cells not wanting to accept charge anymore..

I would suggest that is what has happened to your batteries when you stored them for 3-4 months, and now each one has one or more dead cells..

If you have a digital multimeter, you can test the voltage at the traxxas connector, and also accross each cell to see how many have died.. With any luck you will have enough cells still working to make one or two packs..

Thanks Backlash, re multimeter, for my sins I dont have one. Am looking at a Draper unit on Amazon to fill that gap in my hardware cupboard! So I guess I am using the meter to pass voltage into and through the pack which will then show if the cells are taking current?

Sorry, am very good at some tech but flounder a bit with the basics!

[Backlash]

If you have an old clockwork charger or charge leads, (i.e. older non peak detection charger) then one thing you could try is putting each pack on charge for 30 seconds or so, and then retry on your peak detection charger... DO NOT LEAVE THEM UNATTENDED WHILST ON CHARGE - CHARGE THEM OUTSIDE AWAY FROM ANYTHING FLAMABLE (the packs may explode) - CHECK THAT THEY ARE NOT OVERHEATING WHILST ON CHARGE (an overheating cell usually means that its dead and wont accept charge, and will often overheat in the first few minutes of the charge cycle) -

Re the multimeter, if all you are looking to use the meter for is hobby related (testing resistance, and voltages up to 24 Volts), and not testing higher voltages like those coming from your domestic power point / outlet, then you will get away with a cheaper unit.. A digital unit would be best..

What you will need to do is first test the voltage at the battery connector, and if this is a very low voltage, then you can assume that one (or more) of the cells in the battery has dropped to zero volts...

If you get zero volts at the battery connector, then you need to repeat the test where the wires connect to the battery.. If you get voltage at the wires to the battery terminals, but not at the connector, then you have an open circuit (a break) in one of the wires or joints somewhere in the connector or wires.. If you still test zero volts where the wires connect to the battery, then you need to test each cell individually..

A Cell that shows a voltage of 0.1volt or more may be OK.. Any cell that tests at zero volts is probably dead..

[carparkthrasher]

If you have an old clockwork charger or charge leads, (i.e. older non peak detection charger) then one thing you could try is putting each pack on charge for 30 seconds or so, and then retry on your peak detection charger... DO NOT LEAVE THEM UNATTENDED WHILST ON CHARGE - CHARGE THEM OUTSIDE AWAY FROM ANYTHING FLAMABLE (the packs may explode) - CHECK THAT THEY ARE NOT OVERHEATING WHILST ON CHARGE (an overheating cell usually means that its dead and wont accept charge, and will often overheat in the first few minutes of the charge cycle) -

Re the multimeter, if all you are looking to use the meter for is hobby related (testing resistance, and voltages up to 24 Volts), and not testing higher voltages like those coming from your domestic power point / outlet, then you will get away with a cheaper unit.. A digital unit would be best..

What you will need to do is first test the voltage at the battery connector, and if this is a very low voltage, then you can assume that one (or more) of the cells in the battery has dropped to zero volts...

If you get zero volts at the battery connector, then you need to repeat the test where the wires connect to the battery.. If you get voltage at the wires to the battery terminals, but not at the connector, then you have an open circuit (a break) in one of the wires or joints somewhere in the connector or wires.. If you still test zero volts where the wires connect to the battery, then you need to test each cell individually..

A Cell that shows a voltage of 0.1volt or more may be OK.. Any cell that tests at zero volts is probably dead..

UPDATE! Have now got a multimeter and tested at the battery connector and on 2 of them I get around 8.10 and the other 2 both around 3.63. So I am guessing that means the meter just picking up from the cells that work where as the charger reads the whole pack, finds a fault with some and then says NO!

[tamiya monkey]

the ones at 8v or so, might be ok, the others sound like they've had-it.