[SOLVED] RD Tech DPH5005 inrush current problem with battery pack - Page 1
Forum section: electronics / testgear

author: electr_peter
author_rank: Unknown
timestamp: December 31, 2021, 12:44:21 pm
content: I ran into issue with DPH5005 when using external battery pack Ultimate Speed UMAP 12000 A2. When DPH5005 is switched ON (output is by default disabled and unloaded), battery pack immediately shuts-off (presumably due to over-current "protection"). This is really annoying.I ran few test on startup conditions:Battery pack is capable of 11-13V at 8A continuous, shut-off limit is around 9.5A.With 12V input, DPH5005 PSU consumes 32 mA (less than factory, because fan board is disabled with thermo switch)To startup, PSU need needs DC 12V with at least 180 mA current limit (tested with DC PS with CC), otherwise it does not start - it is stuck consuming maximum current limit at 3.0-3.1V.Inrush current measurements (with 12V 60A supply) showed peaks of 76A (capacitor charge with switch bounce), 1.6ms delay with no current, then 3.7ms period with 17-20A current. Second inrush depends on when PS was last turned on.Due to very high peak currents, DPH5005 triggers battery pack over-current protection and cannot start-up (only after few tries) - almost unusableI can connect directly to internal battery, but that would eliminate over-discharge protection.What can be done to slow down protection in battery pack or reduce inrush current to <9.5A? I would be fine with limited (say 100W maximum) input power.EDIT:solution was found, see post below.

author: electr_peter
author_rank: Unknown
timestamp: December 31, 2021, 06:33:03 pm
content: 12V output is controlled with 3 TPCA8024 N-type mosfets in series (?), 2 shunts (0.01, 0.003) and IC in 20 pin SSOP(?) package with marks "L6034AAF FYBI57S". Pretty complicated, not so easy to add RC time filter as it is tight and pins assigned for over-current protection are unknown. Video teardown on the same battery pack, relevant PCB from 19:50500A Car Jump Starter from Lidl - unboxing and teardownI think inrush current limiting on DPH5005 would be better way to go forward. I saw significant sparks on banana connectors, switch in PSU case suffers from inrush sparks everytime.

author: electr_peter
author_rank: Unknown
timestamp: January 07, 2022, 11:55:32 am
content: RD Tech support suggested to add soft-start circuit. I am looking at simple NTC solution, as only slight limiting (few) is required on startup.

author: electr_peter
author_rank: Unknown
timestamp: January 19, 2022, 06:16:46 pm
content: 1.5nominal NTC solved the issue with failed start-ups from battery bank. However, at 7-10A input current NTC heats up too much IMO, I will add soft-start circuit with MOSFET bypass.By the way, NTC heat-sinking under constant current is pointless and counterintuitive.

author: electr_peter
author_rank: Unknown
timestamp: April 12, 2022, 11:46:28 am
content: Quick update - I have solved the start-up issue quite a while ago. Added soft-start circuit (low value NTC in parallel with N-type Mosfet and some RC delays) reduced inrush current. DPH5005 now works from 6-50V and up to 10A input current from battery banks. Sparking (on input) is also less severe.