PDB Posted September 14, 2023 Share Posted September 14, 2023 (edited) I've purchased a secondhand Taranis QX7S which has the following battery in it and I was expecting more flying time from the battery or maybe I am expecting too much? Charging using the FrSky charger via the TX charging port, when the charger light goes out OpenTX reports the battery is at 7.2v and I've set a low battery alert at 6.5v and I was hearing this after only 40-50 minutes of flying. Checked the telemetry files from last night and it confirms during the session of 5 flights TxBat(V) started at 7.2v dropping to 6.5v, on checking OpenTX this morning it reports the battery at 6.9v. In OpenTX what sort of reading should be expected when it is fully charged and what would be the right number to be set for a low battery warning? Edited September 14, 2023 by PDB Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted September 14, 2023 Share Posted September 14, 2023 I'd suspect the battery, friend has QX7 and easily gets a full days flying out of it. Put your battery on a discharge/charge cycle, say 300ma discharge cut off at 6v, 600ma charge, for 2 or 3 cycles and see how the battery performs. 1 Quote Link to comment Share on other sites More sharing options...
Mike Blandford Posted September 14, 2023 Share Posted September 14, 2023 Fully charged you should see more than 7.2V, more like 8 or more. If the battery is dropping 0.7V, but started at 8V, it would still be 7.3V. There is a setting to make the value you see match the battery. You need to measure the battery voltage, with the Tx on, and adjust the displayed value to match. Either the battery is poor or this setting is incorrect. Mike 1 Quote Link to comment Share on other sites More sharing options...
PDB Posted September 14, 2023 Author Share Posted September 14, 2023 4 minutes ago, Mike Blandford said: Fully charged you should see more than 7.2V, more like 8 or more. If the battery is dropping 0.7V, but started at 8V, it would still be 7.3V. There is a setting to make the value you see match the battery. You need to measure the battery voltage, with the Tx on, and adjust the displayed value to match. Either the battery is poor or this setting is incorrect. Mike In OpenTX there's the "battery range" function which I understand is just a visual meter, on first charge 7.2v was shown in the TX UI so I set the "battery range" separately from 6.5-7.5 to get a warning at 6.5v. Sounding from what yourself and Frank have said the battery is hosed so I've now ordered a lipo. Thank you both. 👍 Quote Link to comment Share on other sites More sharing options...
Mike Blandford Posted September 14, 2023 Share Posted September 14, 2023 No, that is not the setting I'm referring to. It is in the "HARDWARE" menu as "BATT CALIB". This calibrates openTx to display the correct battery voltage. You need to check this whatever battery you are using. Mike 1 Quote Link to comment Share on other sites More sharing options...
Philip Lewis 3 Posted September 14, 2023 Share Posted September 14, 2023 Charge the battery fully then check the voltage with a multi meter, then as Mike has said adjust to the same voltage in Open TX, I would have thought 6V would be a more appropriate cut off (but I don't use NiMh batteries for anything so don't really know). 1 Quote Link to comment Share on other sites More sharing options...
PDB Posted September 14, 2023 Author Share Posted September 14, 2023 (edited) Thanks all, don't know much about electric stuff but keen to learn so multimeter ordered and update you on the results.👍 Edited September 14, 2023 by PDB Quote Link to comment Share on other sites More sharing options...
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