5mv/cell/degreeC

MEXICOWANDERER wrote:
Hint:
I found linkage between voltage and resistor error in my DMMs. Therefore I now periodically verify with an ultra precision 5ppm calibration resistor. And I have no idea why this works :)

Heh, if this thing gets to the point where I can't re-calibrate it any more, I would have a hard time figuring out which resistor to swap out. And Rogue's website is no longer with us, so no help there.

Besides, my soldering skills aren't what they used to be. So, a new toy, rather, mppt controller would be what happens.:)

scrubjaysnest wrote:
Bruce,
You want me to PM RickST29, he is still using a Rogue; or do you still have an acct on the TM site?

Ken

Thanks ken. But think I got this issue resolved with the VTRIM recalibration.

Batteries are at 10C this morning and they went into absorb at about 0.4-0.5V higher than the set point. Just about right for 5mv/cell/degreeC. So I'm a happy camper.

Been a long time since I've been on the TrailManor site!

Hint:
I found linkage between voltage and resistor error in my DMMs. Therefore I now periodically verify with an ultra precision 5ppm calibration resistor. And I have no idea why this works :)

Bruce,
You want me to PM RickST29, he is still using a Rogue; or do you still have an acct on the TM site?

Ken

I have a separate VOM that agrees with the Rogue's display when connected to the Batteries, so the actual measurement of V seems ok. Temperature measurements also seem reasonable.

But it turns out that the Rogue's set point calibration was way off. IOW you set it to 13.2V float @25C but it uses 13.6V at float.

Didn't used to do that and I dunno when it changed ... perhaps when I rewired everything going to 4 GC2s from two.

Anyway, Rogue allows you to adjust the VTRIM value +- 0.5V (on a scale of +-20). Adjusting to -15 out of 20 seems to have fixed the baseline @25C set points. Bit disturbing that so much correction is required.

Now I'll re-monitor what it does at less than 25C and see if it properly follows the 5mv/cell/degreeC setting.

Last I checked my Morningstar, via data dump, it was right on the money. It's set at 3mv. The rogue from all I've heard are very good.

I would verify the accuracy of my monitoring and measurement devices just to be absolutely certain.

westend wrote:
What controller do you have?

Roque 3048 (now defunct).

It may be that my problem (actual measured/displayed absorb and float V exceed settings) is not the temp compensation, but the actual V calibration. Just noticed that the Rogue can be calibrated so I'll look at that next.

Thanks all for checking my caclulations.

What controller do you have?

You are correct. If you expand the temperature range you'll see a significant change in charge voltage. For example, at near freezing your Float voltage will be maintained at almost 14 V, and at 100 deg. F the Float voltage will be maintained at around 12.8 V. The Bulk and Absorb rates will all be correspondingly higher, too.