Lead-calcium battery charging - advice?

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larrywa
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My RE system: FlexPower Two
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Mate3 v3.015.005 (works excellent!)
Hub 10.3,
PV:1000W east@45, 600W west@45, 2400W south@19 deg.
Battery:48v @ 130Ahr Crown batteries, deep cycle <$380 for 6.25kWh

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Lead-calcium battery charging - advice?

Post by larrywa » Fri Aug 16, 2019 12:00 pm

I finally gave up on burned out lead-antimony high maintenance batteries after my fourth set now, and picked up some lead-calcium types. I am running a 48v system using a PowerFlex II system.

I think I have most of my float, bulk and equalise settings figured out. Geee these things don't boil or heat up! They are almost indestructible! Took them up to 62Vdc and the current just drops to about 2.0 amps after the batteries have taken all the current they want. I figured there was a bad 12v cluster. Then I discharged them to about 70% and I had to restrict my charge currents. They take massive amounts of current when they want it. I guess that is what the Cranking Amperes rating is all about....lots of plate area, compared to a deep cycle battery.

So far I am impressed, more than any deep cycle batteries I have burned out.
This bank is, at a guess about 110 AmpereHours, Group size 31, starting battery. Lead-calcium plates, sealed vent plugs. Maybe some pressure relief but I don't see them. Standby usage only. Maybe discharged once or twice per year. Cut off at 42 vdc. See how that goes.

Anybody have ideas or recommendations on settings for these batteries? Thanks in advance.

raysun
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Re: Lead-calcium battery charging - advice?

Post by raysun » Fri Aug 16, 2019 12:27 pm

The manufacturer would be the best source for charging settings.

Batteries meant for float service have a fairly special makeup, distinct from batteries meant for cyclic use. Also, batteries meant for motor starting applications are substantially different from batteries meant for deep cycle use.

Calcium reduces self-discharge, but the positive lead-calcium plate has the side effect of growing due to grid oxidation when being over-charged.

I'm not expert, but I've never seen a 48V lead/acid battery that will withstand 62V charging and unlimited charging current for any great length of time. If 62V is held through the Absorb phase (where the charge current steadily declines to a minimum) I'd expect there would be a good deal of gassing that would not be recombined by the catalyst in a VRLA (sealed) battery. The vented gasses would result in permanent loss of capacity.

larrywa
Forum Guru
Posts: 354
Joined: Thu Jun 25, 2015 11:25 am
My RE system: FlexPower Two
2 x GVFX3648s,
2 x FM80s,
FNDC w/3 shunts,
Mate3 v3.015.005 (works excellent!)
Hub 10.3,
PV:1000W east@45, 600W west@45, 2400W south@19 deg.
Battery:48v @ 130Ahr Crown batteries, deep cycle <$380 for 6.25kWh

ISY994i HA, Insteon, X10, Philips Hue, MiLight bulbs & RGBW strips
WebControl 8 as weather station stuffing
ISY994 variables via REST interface

Raspberry Pi3 x 2, Pi1 B+

Re: Lead-calcium battery charging - advice?

Post by larrywa » Fri Aug 16, 2019 4:24 pm

raysun wrote:
Fri Aug 16, 2019 12:27 pm
The manufacturer would be the best source for charging settings.

Batteries meant for float service have a fairly special makeup, distinct from batteries meant for cyclic use. Also, batteries meant for motor starting applications are substantially different from batteries meant for deep cycle use.

Calcium reduces self-discharge, but the positive lead-calcium plate has the side effect of growing due to grid oxidation when being over-charged.

I'm not expert, but I've never seen a 48V lead/acid battery that will withstand 62V charging and unlimited charging current for any great length of time. If 62V is held through the Absorb phase (where the charge current steadily declines to a minimum) I'd expect there would be a good deal of gassing that would not be recombined by the catalyst in a VRLA (sealed) battery. The vented gasses would result in permanent loss of capacity.
The manufacturer is not to be found and I doubt they would even know. (China?) You just stick them on the tractor and whatever it charges them to is what you get? LOL They have no ampere-hour rating or even reserve capacity, which is probably a better rating than most ampere-hour ratings. It's the same thing except it is based on a 25 ampere load (for smaller sizes) and fits most actual usages when required to perform. Heck my two OB inverters draw 4-500 Watts just idling with no load. Thank goodness they self stage, dependant on PV output.

The 62 volts doesn't draw much current, if the cells are all charged. EnerSys docs recommends their lead-calcium cells be taken to 2.7v/cell (=64.8v) and held for 44 hours after the current stabilises to a constant rate over 24 hours. That equates to about 80 hours of brutal equalise. This is the only recommended for initial phase-in of the bank, though. After that it appears they recommend about the usual 2.33v/cell (=56v) average based on a chart with specific gravities styles and plate formulae.

They do warn you about having too low of a charge causing problems with them, but the high end comes with warning also.

Interesting thing is, I have played with the float settings on a fully charged bank, and 58v, 56v, 54.4v, 54.0v, 52.4v, and 52.0v all draw the same charge current while floating. Now OB's metering did a ridiculous thing, metering every connection, except the battery, so that battery current is always the sum of three shunts that may vary from each other by more than the quantity I am trying to measure. I have a DC clamp ammeter but with only 0.1A resolution. It's pretty coarse measurement for trickle charge evaluation.

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