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| Trying out battery desulfator |
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| Rick Law:
Back in December of last year, I started a thread about using epsom salt to revive SLAs. https://www.eevblog.com/forum/chat/epson-salt-in-lead-acid-battery/ The conversation drifted to using pulse-device for SLA revival a bit. Cheap desulfators are readily available but web research shows desulfation requires much better equipment. Given how cheap those cheapies are, I was going to try anyway... and I did. Folks here may find the results interesting - measurable improvement but no meaningful improvement. Here are the details for those interested. I have 3 kind-of-dead SLAs and I tested it with the best of the three and it is originally rated at 22AH. This battery was not maintained for a few years, it would "fully recharge" in sub-seconds and went back to dead on any load. After trickle-charging, it was holding 12.6V and was able to deliver a few minutes of charge before January 7. For testing, I use a 20 Watt 12V car light bulb as load. Each run, I merely timed how long it takes for it to drop from full charge 13.6V to 10.5V. It will start at about 1.7A when battery is full, down to about 1.5A at 10.5V. 10.5V is low, but according to their spec, this is what they discharge to for the 22AH number. Except where noted, the in-between days/hours were times when the desulfator was connected - So, approx 24hrs of desulfator run between discharge runs, except the last which was 2 months of pulsing from 1/28/20 to 4/3/21. As expected, but not as hoped; it did something, measurable but not meaningful. Run time is measured by an INA219 with an Arduino NANO 210107 - 6m58 (before any pulsing) 210108 - 7m44 210109 - 25m57 210110 - 23m13 210112 - 29m51 210112 - 21m43 (Before interruption) 210117 - 16m41 (Resumed from interruption) 210118 - 13m50 210118 - 11m46 210119 - 10m16 210119 - 0m03 (Interruption) 210121 - 13m47 210121 - 11m41 210124 - 14m35 210128 - 11m23 210128 - 10m33 210403 - 24m09 Yeah, it improved from 7 minutes to 24 minutes of 1.5A. For a 22AH SLA, 24 minutes of 1.5A is still a dead battery. Measurable improvement but not a meaningful improvement. I do notice that at lower amp discharge, it improved more - but I did not collect data on that so I don't know for sure by how much. Oh, a few words about the pulser. The sticker said it pulses at 10KHz, it actually pulses at whenever it can, probably when the capacitor is charged enough or something like that. As measured by my Hantek 6022BE USB Scope, I can clearly see an "attempted pulse" (very low amplitude pulse) at 64KHz. Every 4 pulses or so (that makes it around 20KHz), it builds up to a larger pulse at about 0.5V. At longer intervals, it has much larger pulse at over 1.25V. There are times that it couldn't do the larger pulse. The pulse amplitude varies depending on the state-of-charge of the battery. The scope output is attached. I know the "Battery Desulfator" isn't going to do much, but I was hoping for a bit more. I do not regret "wasting" $15 for this thing. It was fun experimenting with it. Edit - correction made, the battery was not maintained for longer than 12 month that I initial wrote, that was a different battery. This one was a few years... |
| james_s:
You might have gained just as much simply by charging with a normal charger and discharging with the lamp several times. The desufator may work better on a conventional lead acid battery. The SLA type I have never had any luck trying to revive once they go bad. I've gotten significant improvement by adding distilled water to the cells but not enough to to really be worthwhile. When I've looked inside old SLA batteries they were always completely trashed, the plates crumbling to dust. |
| T3sl4co1l:
A gel cell I ruined last year, I tried pulsing much more aggressively than that (what is 0.5V supposed to do anyway? what a quack device). I didn't notice any significant change in V(I) curve, under high voltages (>18V), or after some time (thousands of pulses). Tim |
| Rick Law:
--- Quote from: james_s on April 04, 2021, 05:50:01 am ---You might have gained just as much simply by charging with a normal charger and discharging with the lamp several times. The desufator may work better on a conventional lead acid battery. The SLA type I have never had any luck trying to revive once they go bad. I've gotten significant improvement by adding distilled water to the cells but not enough to to really be worthwhile. When I've looked inside old SLA batteries they were always completely trashed, the plates crumbling to dust. --- End quote --- It was an "SLA" but still just a flood-acid battery. The openings are glued with rubber caps over it. Late last year, I tried refilling the low-level cells with distilled water. Gaining nothing, I emptied them and refilled with car battery acid which should be 50% H2SO4. That didn't gain much either. Desulfator was the last bullet in the chamber. --- Quote from: T3sl4co1l on April 04, 2021, 05:53:27 am ---A gel cell I ruined last year, I tried pulsing much more aggressively than that (what is 0.5V supposed to do anyway? what a quack device). I didn't notice any significant change in V(I) curve, under high voltages (>18V), or after some time (thousands of pulses). Tim --- End quote --- Yeah... I was not expecting much from these cheap toys. Web research (from a graduate conference paper) shows they got 95% recovery at 1MHz pulsing, but not sure what amplitude was it that they used. I can't say this cheap toy doesn't work. It is measurable improvement, just not meaningful. |
| tautech:
Played with desulpfators years back and they weren't much good until you optimized them. 7A @ 60V @ 1 KHz into SLA's and LA's was the best I achieved using custom flybacks and MOSFET ON times nearly to magnetics saturation. First use in anger of good current probes for both monitoring currents into magnetics and scoping the magnitude of the current produced. Powered only from the battery being pulsed it was normal to get a battery voltage improvement overnight despite the pulser was being powered by the battery all the time. |
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