MAC charger problem......SCR481717

[pinkfloydsound]

Hello all,

I'm helping a friend with his 2005 48v (6x8v) Yammy & have encountered an odd problem. Apparently he has had issues with this thing over time (bought it used). It has less-than-2yo Trojans in it but it hasn't been charging properly, ie just never seemed fully charged. It sat for a while w/o the charger on it so I had to use a 6v variable charger & crank it up to revive the cells individually to operating range for the MAC to "see" them. We got the pack up to around 46 volts, plugged the charger in & it appeared to start charging.
This is a MAC with the led's on the left of the front panel & 15A breaker switch on lower right. What puzzled me was after it went through it's start up sequence, it was only a minute or two before it switched to "80%" status. I read the pack voltage at around 52v right then. But 10 mins. later it was only at 51v..............about 45 mins. later it was still only around 51v. This thing should've been buzzing hard to charge the pack but it wasn't. But I'm not familiar with this unit, either. However, after searching & finding the troubleshooting guide for this unit (thanks CGTech), I found that this unit shouldn't indicate an 80% charge status until it sees around 2.35v per cell.........around 56v across the pack.........& I would imagine it shouldn't be done until the pack hits around 60v. My buddy texted me & said the charger now indicates that the pack is fully charged...........about two hours after plugging the charger in.
I'm fairly convinced that the charger has a problem & likely has for some time, even though it appears to be operating properly as per the manual. It doesn't get warm & neither do the cables. All the cells measured similarly. The cart is clean & all the connections are good. I've read a lot about the issues of these chargers but haven't come across this type of problem.
Has anyone else seen this? Faulty sense unit? Bad control board?

[cgtech]

Unplug and replug charger, and verify the on charge voltage. Batteries that sat dead don't readily start acting like good batteries. If numbers are still low, start checking connections, like inside the charger handle, and on the fuse inside the charger (early models had a window on the front, and a fuse inside the window that is known for troubles).

[pinkfloydsound]

Did the unplug/replug on suspect to no avail. It took a couple hours each to get the batts up to around 7.5 with the 6v charger. But I was encouraged that, going back through the batts after doing so, the ones we charged first didn't dissipate much at all while waiting for the others to be charged........good sign. Still, I figured these things would have the charger humming pretty good when we hooked it up.
I'll have a look inside the unit tomorrow some time & check what you suggested. I'm sure it could use a good cleaning anyways. I'll keep my fingers crossed that it's something obvious, but I never seem to have that kind of luck.

Thanks for the quick reply, cg.