| General > General Technical Chat |
| equipment malfunction with old Nicads |
| (1/2) > >> |
| loop123:
I have an equipment that just cant run or work if the old Nicads are present. Can old Nicads somehow cause a short or something? Also is it not when the charging is on while circuit is being used. The circuit is using the voltage from the charger? So how can old bad Nicads make the circuit not work as if the circuit is depending on the batteries even when charging? Is this possible? Anyone has similar experiences? |
| Kim Christensen:
Old NiCads do tend to fail shorted. Many of those old circuits used a constant current charger (charged at 10% of battery capacity) that supplied enough current to charge the batteries but not enough to run the product. So with something like that, you'd need a good set of batteries for it to work. |
| loop123:
--- Quote from: Kim Christensen on January 20, 2024, 05:56:58 am ---Old NiCads do tend to fail shorted. Many of those old circuits used a constant current charger (charged at 10% of battery capacity) that supplied enough current to charge the batteries but not enough to run the product. So with something like that, you'd need a good set of batteries for it to work. --- End quote --- I used a 24V Meanwell GST60A24-P1J AC/DC switching adaptor. The batteries are 2 sets of 7.2v Nicad batteries. So there must be a constant current charger within the circuit. But even when the adaptor was used, the equipment couldn't run. It was only after I removed the Nicads they it could run again. Are their circuits where if there are batteries inside, the 24V adaptor DC was suppressed, and only when the batteries were removed, that the AC/DC adaptor got reactivated? |
| tggzzz:
--- Quote from: loop123 on January 20, 2024, 05:23:52 am --- I have an equipment that just cant run or work if the old Nicads are present. Can old Nicads somehow cause a short or something? Also is it not when the charging is on while circuit is being used. The circuit is using the voltage from the charger? So how can old bad Nicads make the circuit not work as if the circuit is depending on the batteries even when charging? Is this possible? Anyone has similar experiences? --- End quote --- Yes. Here's a writeup of one piece of equipment showing how the designers protected against the consequences. https://www.eevblog.com/forum/testgear/fluke-8125a-military-dmm-teardown/msg2540730/#msg2540730 There's a worse example of NiCds being a pain... Tek 1502 TDRs have a (fortunately) unique PSU where the NiCd charging is controlled by a PUJT and SCR. The equipment is protected against failure by preventing the internal SMPS operating if the NiCd battery voltage is too low (i.e. discharged) or too high (i.e. missing). That means it won't work on the mains without an operational battery. To compound that, even when switched off, the batteries are discharged at 1mA. That leads to the requirement that the battery pack must either be removed or charged once a month, but not for more than 16 hours since the charger's crest factor damages the battery. Consequently, if you obtain a Tek 1502 with a battery pack, the cells have usually disintegrated to produce a hazmat toxic waste site. Shame, because the 1502 is still a delightful instrument to use. Oh, make sure the sealing is still intact before you operate it in driving rain or store it under 30cm of water :) |
| AVGresponding:
--- Quote from: loop123 on January 20, 2024, 06:30:39 am --- --- Quote from: Kim Christensen on January 20, 2024, 05:56:58 am ---Old NiCads do tend to fail shorted. Many of those old circuits used a constant current charger (charged at 10% of battery capacity) that supplied enough current to charge the batteries but not enough to run the product. So with something like that, you'd need a good set of batteries for it to work. --- End quote --- I used a 24V Meanwell GST60A24-P1J AC/DC switching adaptor. The batteries are 2 sets of 7.2v Nicad batteries. So there must be a constant current charger within the circuit. But even when the adaptor was used, the equipment couldn't run. It was only after I removed the Nicads they it could run again. Are their circuits where if there are batteries inside, the 24V adaptor DC was suppressed, and only when the batteries were removed, that the AC/DC adaptor got reactivated? --- End quote --- How are you connecting the external PSU to the DUT? |
| Navigation |
| Message Index |
| Next page |