Lithium Titanate Oxide Cells

[Gary Hammond]

Hi Bob,

Just watched your video. Very impressive performance out of these little cells!

You remarked at one spot in the video about the wiggly graph curves with the CBA. I was having the same problem with my CBA and the voltage was lower on the chart than a separate volt meter directly across the battery. Turned out to be heating and voltage drop on the input connectors to the CBA. Someone else posted earlier about this happening to theirs as well. So I removed the connector and soldered the input wires directly to the contacts in the CBA. That cured the problem and I now get smooth curves and more consistent results.

I thought at first that the CBA's internal circuity was going bad. Turned out it was only the connectors, which showed no visual evidence of making a bad connection.

[BobZilla]

Haha Bob, you got me. I should've watched the video first, but I was waiting until my lunch hour to do that.

Wow, those cells have some pretty awesome power density. They do "fall off the cliff" pretty quickly at around 13v though. I think they will do great on solar. If you have a charge controller/inverter where you can program the min/max charge and discharge voltages you should be set.

Good to hear you're working with 18650's too. I joined a DIY Powerwall forum where some guys are doing some amazing things. I'm not going that big either (yet, at least) but it is interesting. Maybe we should start a thread on that, don't want to hijack your thread here.

Looking forward to hearing about your Edison cells too. I have a few that I bought second hand, I think they were used by the Japanese in the war. Start a thread on those too and we can share...

John K.

Yea I know in hind sight it was a little goofy to present these cells with half a charge as I did. I will make some full charge curves some time later and I might try charging on one of my SS builds instead. About the cliff at 13v, I noticed it too and it seems to be about 13.25 or so. Now I could remove one of the cells to bring that down but I did the 6 cells thinking that if I do not have to charge fully then it would be easier on the cells over the long haul. From what I know about any lithium it is the upper voltage that wears them out the most. Kind of the opposite of working with LA where we intentionally push them high.

You have original Edison cells? Wow if that is what you have then please do post about them, or join in once I get a thread for mine started. I do not have the originals, I have the new Chinese plastic version. I had read all about the originals and wondered how that technology could have slipped away. The plates are not even part of the active material as I'm sure you know so other than changing electrolyte or physical damage there is nothing to go bad on them. Supposedly they will last 30k cycles or more.


Gary,
Thanks for the tip. I think I remember you talking about the deans connectors awhile ago too. I may have to do as you suggest. I have used those same connectors on my machines for awhile now and have not noticed any issue but on those I soldered them myself. Do you think it is the actual contact point in the connector or could it be a poor solder job on the CBA? I know that if you do not solder that little blade on really well these connectors can perform horribly. I found the trick is when soldering it on to strip the wire all the way back to be even with the plastic case and then solder all the way back to that point. It makes the whole thing nice and stiff so when you go to push the pin up in the housing you do not get any buckling which leads to poor connections.

[Gary Hammond]

Hi Bob,

.....................................Gary,
Thanks for the tip. ......................................... Do you think it is the actual contact point in the connector or could it be a poor solder job on the CBA? ...........................

I really can't say for sure, because I don't remember seeing any evidence of either arcing or poor solder joints on the contacts. It's been awhile since I corrected the problem by soldering the wires directly to the contacts inside the CBA. What I do know is that it has worked flawlessly since I did this!

[BobZilla]

Anyone remember this old setup?



I have not run this SS in a few years. I got it out and re-did some of the wiring. It's running in branch output.

In the picture if you look close you can notice the LTO batteries on the floor there. I want to do a post on these two starting from the same charge state but in this charge one was already way ahead when they started. I went back today and watched Mr. Bedini's videos in the SH Oscillator thread and this machine was what I had built back then trying to replicate his branch circuit. Damm I miss him and I didn't even know him.

[BobZilla]

Hello group,
I did a charge run on the machine from the last post in branch mode. It did very well but I am not posting the chart because I had to stop charging several times and then come back and turn it back on. These batteries are so small that I could not leave it running while away for fear of over charging so it was not a clean run. I will try to do another one and capture it for you to see all in one shot though.

I can post the discharge from that run however. What we see here are both batteries connected in parallel to double the capacity. They were charged up to about 16.7v which is basically a full charge for a six series (2.8v per cell). These are supposed to be 2.9AH cells so I actually got more out than the rating. The discharge was done at 1A.

I don't like posting this without a charge run to go with it but at least you can see the curve on these things.

[BobZilla]

I have noticed after doing a few more runs that without bringing these cells up to a full charge you do not get a good capacity discharge back out. What I mean is if I charge to say 15v on one pack I will only get about 1.5AH back out but if I run up to 16.8 I will get 3AH or more out. The last little bit on the charge makes a huge difference. My original thought was to run these sort of in the middle of their range but now I am not so sure on that.

I think I will remove a single cell from the packs so that a FULL charge takes it to about 14v instead of 16.8. This way I can still hook it up to an inverter but get a full discharge from it. The trouble as-is was that the inverter will not accept 16.8v, in fact anything past around 15v will not work on most of my inverters. It would work fine as a 6S if I was not using an inverter or if I don't mind the shortened run time but these things are so small to start with that I think it's better to at least get the 3AH back out of them.