watch those meters

[Ralph Day]

Hi all

I stepped into a metaphorical renewable energy cow pat!

After reading postings on (another forum) from Jamie Surrette, and talking to Surrette's tech people, i decided to discharge my batteries to 50% as recommended (2x per year they say). With a couple of cloudy days, i set the dehumidifiers going, ate lots of toast, etc etc. This morning got up and was within 2 amphours of 50% on my T500 meter. Yes, that's the first smack in the head.

Before starting the genset i took a spec gravity reading, several to be exact. instead of the 1.200-1.800 ballpark i was in the soccer field at 1.140...between 20-30%! I always tell people NOT to trust the meters, read the sg's, ad nauseum (right Mario), and i got caught, stepped in, etc etc. Second smack in the head.

After 4.5 hours of charge, with about 80amps dc going in, i'm still only at 1.155 or so. The replacement of power is slow. Next time i do this, i will stay on the same playing field by cross-referencing the SG readings to the T500 and not walk out into the unknown field with nasty cows in it!

Funny, the SG readings and T500 readings when the batteries are fully charged are always accurate...1.265-1.280, full state of charge, depending on what voltage you check at. Live and learn.

A chastened,
Ralph
:o

[Paul Bailey]

Can the TM be rescaled for better accuracy/or re - teach to get tighter tolerances on the amp hours in or out..???? Your bat will probably like this 20% anyway on occasion due to its lift truck cell design. Paul:)

[Mark Parsons]

Hi Ralph,

Hopefully, you caught them in time and didn't do any damage.

Are you using Surrette batteries? Didn't know they made lift truck designs.

I am using the S-530's. Only 2 so far with some other UPS batteries. The plan is to scale up to 8 - S-530's configured for 24V. I am really flying blind at this time other than terminal voltage. My cottage doesn't see much draw yet anyway. I have a shunt in place now but no canned battery monitor. I was planning on using the PLC to integrate and monitor amp-hours in and out. I assume an accumulative error put your Trimark monitor out of whack? Would equalization throw the calculation out?

Any suggestions on frequency to re-master the amp-hour calculation to measured SG? Quarterly?

I looked at the algorithm that Outback use and they discount about 8% of the charging amp-hours as a starting point. I don't know what Bogaert use.

Regards,
Mark

[Ralph Day]

Hi Mark

The best thing to get is a good hydrometer. I have one, just didn't use it at the right time. Try Ontario Battery Sales on a search engine.

The genset ran for 9 hours before i shut it down. THe SG got up to 1.450 or so when i let the renewables take over. Lesson learned.

Ralph