Circuit diagrams for a grid 2260 psu

[arlaneenalra]

Well, I figured out why it's not running The inductor is in line with one half of the AC between what looks like an isolation transformer and the bridge rectifier. I could probably jumper it, but it looks like it's part of a filter of some sort so I'd rather not, it's big enough and with a small enough number of turns that I might be able to rewind it if I can find some good magnet wire, but I'm not sure lf the state of the rest or the psu.

 

[JDat]

Start by beeping and drawing primary AC schematics including FULL BRIDGE RECTIFIER (c) and Electrolytic capacitor.

 

[arlaneenalra]

That's a reasonable approach and I can go down that route if I have to, but I was hoping someone already had one on hand. Mostly so to track the original value of that inductor in case I have to rewind it.

Looking at it, I may be able to add a small jumper to the burned through wrap and throw it on an LCR meter, though I'm a not sure what impact that would have on the inductance. Probably negligible, but I don't know how accurate it has to be for this purpose.

 

[larz_dub]

Here's my solution to modernizing the PSU for NiCd and NiMH batteries. Those battery packs take 8xAA or 8xSub-C size cells, depending on the version / capacity. This Tenergy smart charger seems to work fine on both. I've only run a few complete power cycles but so far, so good! BTW, the new NiMH do get the batteries back to 2-3 hours run time.

 

[arlaneenalra]

I'm guessing that's only wired to the "charge"pins on the connector and not the main power pins?

 

[larz_dub]

I kind of cheated because the "Smart Charger" already has it's own voltage sensing, and basically ignore the charge controller that's embedded in the battery packs. I picked up some 8-pin mini DIN connectors. Here's how I wired the charger red and black wires to the DIN. Note the charge pin is active in low state (tilde) so this is in charge mode by default. Like I said, I've only run a few charge cycles but everything seems to work, so far. Here's page C3 from the GRiD manual. BTW, I've done this on both size battery packs running both 2260 and 2270. The Tenergy charger is perfectly matched to the Tenergy NiMH cells I used to rebuild the batteries so I'm feeling pretty good about this approach.

 

[larz_dub]

Update on the Smart Charger setup. It does charge but really needs the temperature sensor to function properly. I'm running back probes and thermal profile on this setup to sort out a long term plan. The past full charge from being completely drained got hotter than it should. I guess Delta V sensing is getting tripped up with the existing charge controller intact. Seems to behave okay on 0.9A charge but got extra hot on 1.8A so I would advise against that for now.

 

[arlaneenalra]

There's usually a correlation between the charging rate and capacity of the battery being charged. At least with some Li-Ion chemistries thenrule of thumb was to charge at about 1/2c if I remember correctly. So a 1200mah battery would be charged at 600ma or so. I don't know the rules for NiMH batteries but it is a concern. You also have to be careful of having a drain as part of the charging loop. So if the machine and charger are on the same circuit, it can munge up the charging current a bit and cause problems. NiMH and NiCad are more forgiving on the charging current than Li-Ion but I'm not sure how much more forgiving or what's safe.

Hmmm, the little board inside the battery has some transistors on it, I'm going to have to trace that out when I pull mine apart to rebuild it ... I wonder what they're doing there ...

 

[larz_dub]

Yuuup. That's the embedded charge controller. As another experiment, I soldered a Timya header directly to the power and ground header of the battery connector inside. I'm directly charging the cells, bypassing the charge controller. With the back-probe on the connector, the smart charger is a lot smoother and consistent. That might be because the cells are mostly charged already so it's float vs. bulk. Out of time for this project but back at it in a few days.

 

[Compgeke]

Yuuup. That's the embedded charge controller. As another experiment, I soldered a Timya header directly to the power and ground header of the battery connector inside. I'm directly charging the cells, bypassing the charge controller. With the back-probe on the connector, the smart charger is a lot smoother and consistent. That might be because the cells are mostly charged already so it's float vs. bulk. Out of time for this project but back at it in a few days

I see you've got the battery pack open. Are these glued or ultrasonically welded from the factory? Got a PenExec of some description recently but don't want to completely destroy the battery pack opening it up.

 

[Compgeke]

Can't edit so update: Managed to get it opened. Glued together. Squeezed it in a bench vice enough to break the glue bond and it came open reasonably easily from there.

 

[larz_dub]

Sorry for the delay, I just got back to town. For the batteries, I have a flat screwdriver blade that fits the gap between the clamshells really well. It's extra wide, maybe 3/8" and works great to insert in to the slot and twist a little. I work my way around the battery a little at a time, twisting until I hear a pop then moving to a different location and repeating. I've done a few of these and the results are pretty good, slightly marring the plastic here and there but mostly a clean process. I have temporarily been taping them back together but planning to sparingly use a touch of super glue in strategic locations. Still thinking about that before I do it.

 

[larz_dub]

Good news - I've got the $20 Tenergy smart charger sorted out and performing perfectly in all modes including with and without load. With matched Tenergy cells @ 9.6V, the 2.4ah pack takes < 2 hours to charge and runs for 2 hours and 45 minutes on a 486 / 2270. The problem with the earlier wiring diagram is that the embedded NiCD charger was competing with the new NiMH delta-V sensing logic. For this to all work, the old charger needs to be electrically disabled while leaving it mechanically intact. Basically, if you wire the NiMH charger directly to the cells and bypass the old controller (cutting some traces), it works great. I also replaced the old thermal detection with the new thermistor that came with the smart charger and it works perfectly. It's great but the finished charging circuit is no longer compatible with the old batteries and cant be used on batteries that have not been upgraded and modified. Because of that, I won't be offering this as a service.

I took a bunch of pictures and notes but didn't have time to do a full schematic. With that said, I do have 1 more battery pack to rebuild and will do a step-by-step procedure document and share it here for posterity. The new setup does significantly outperform the factory PSU and batteries.

 

[arlaneenalra]

Do you reuse the internal 5 pin connector when rebuilding? Or do you have a part number for it?

 

[larz_dub]

Yup, just left the 4 power pins in place as-is and cut the traces to the rest of them. Then re-used 2 of the cut traces for the thermistor and soldered the leads directly to the din on the board. I'll do a step-by-step guide later this week. Turned out great! loving the fast, safe charging and long-lasting NiMH cells.