The Horrors of Battery Maintenance

[Gary]

It's been less so long since I've been scootering I've been forced to do test discharges of the battery on my N19 to try and restore the battery capacity. I don't have a auto-cut-off on the discharge so I have to carefully monitor the discharge to stop it before the voltage drops below 21V and over-discharges and ruins the battery.

Yesterday I screwed up and forgot all about it leaving the battery forgotten for over 3 hours. When I remembered I rushed out and found it completely drained. The WATTS-UP meter was BLANK (no voltage to even drive the display).

I knew I'd just completely ruined the battery. The battery that was not 100% anymore anyway after 3 years and trying to maintain with test discharges had just been flushed down the toilet. $600 and all that effort wasted.



I charged it up again just to see if ANYTHING was left. The first charge barely brought the voltage back up to 21V.

But the second charge got the voltage back up to nominal voltage.

The test discharge (to verify the extent of the destruction) seemed not as horrible as I first expected. Actually as the discharge continued I continued to be surprised each reading that it was still going.

To make a long story short, instead of destroying it it actually completely restored the capacity of the battery. I got 14.4 Ahr terminating the discharge at 21.41V instead of 11.0 Ahr on the last discharge 9 months ago terminating at the same voltage.


Weird and amazing. I lucked out - big time!

[FW]

Hmmm, you might want to let Rodney know about that technique. I knew it sometimes worked on NiCads, but not NiMh.

If you want to be really brave, OFG-1 found a Lithium battery that should fit inside an N-19. It would take some work to get it mounted, weighted, and trimmed, but doable. Not any cheaper, though.

[Gary]

We talked to Rodney about the Li option when Kathleen's scooter battery had a couple cells die. We were planning to replace her's anyway. Resurrecting this one may be temporary or not but it is interesting.

[OFG-1]

While not quite as dramatic as yours Gary, I have been cycling my N-19 battery with a standard 1 1/2 ohm burn tester to see what I could recover. The first time, I ran it from 24.7 volts down to 19 volts, it took 42 minutes. After 3 cycles of 24.7 to 19.5 volts, I am up to 67 minutes. As expected, the curve from 21 volts to 19.5 volts is only about 8 minutes. I don't have the watts up meter. I am not sure how this will actually relate to run time,it seems that no one has a current draw curve for the scooter under actual conditions of say a diver with doubles and a stage at a certain prop setting. If anyone has that information, I would like to see it.

I ran the scooter in Indian for 5400 linear feet, about 36 minutes or so, and it did not cut off. When I bought the thing, I was consistently getting 115 minutes out of it. Last summer it was cutting off at 40. Caver95 charged me $150.00 to tow out of Indian, my AAA card did not cover it.

I know of another person that is completely discharging his pack to 4 volts, and your old one Forrest, and claims to have it back up 60 or so minutes.

This is the replacement battery that I am looking at :

http://www.batteryspace.com/highpowe...fuelgauge.aspx

I believe that 2 of them would fit in the hull, although that would really be expensive.

[FW]

I know of another person that is completely discharging his pack to 4 volts, and your old one Forrest, and claims to have it back up 60 or so minutes.

Darn, I wish I had tried that. I was only getting 40 minutes

[Sludge]

Let me semi-hijack this over to lead acids. The UV-26/18 I got this summer was kept indoors and periodically charged by the previous owner. But I was thirty minutes into my first dive on the 26 when it started slowing down. (The audible pitch of the motor had dropped about one step on the diatonic scale. If you don't read music, ignore that.) The 18 had about the same burn time.

After several dives (and charge cycles) it gets a little more, maybe 45 minutes before dropping. It has the cheesy little charger, what, 3 amps? I'm wondering if the whole problem is from not getting a full charge to begin with. Here's why:

With just about any battery charger I've owned over the past ten years (light, scooter, phone) I've done this: after the light comes on to indicate full charge I disconnect and after a few minutes I plug it in again. Most chargers will charge for a few minutes before indicating full charge. I've convinced myself this is giving it a little more juice. But the SS charger's light won't go to red when I do this. It stays green. I can come back a week later, or a month, and when I plug it in it will glow red for about half a second and go to green. I'm thinking the charger is so cheap it won't ever give me a good charge.

Any comments?

[OFG-1]

Any comments?

I don't know which charger you have. I have the Interacter with the UV-18 that i have. After a day, it will go back to charging for a short period. Lead Acid batteries store charge better than anything else. Get a burn tester, and cycle the batteries periodically down to say 20 or so volts.

Have a good read here:

http://www.batteryuniversity.com/partone-13.htm

[RN]

There are way too many of you not using your scooters enough. I'll tell you whatm leave al your scooters with me and i will regularly exercise them so this doesn't happen again.

[sskasser]

There are way too many of you not using your scooters enough. I'll tell you whatm leave al your scooters with me and i will regularly exercise them so this doesn't happen again.

Great idea, Rob! I, too, will sacrifice myself to help out my fellow cave divers with this serious problem!

[FW]

There are way too many of you not using your scooters enough. I'll tell you whatm leave al your scooters with me and i will regularly exercise them so this doesn't happen again.