Interesting stuff on off-grid battery charging

[Volvo farmer]

I never knew this before. Big off grid battery banks should be deeply discharged once every three months or so. I've got Rolls/Surrette batteries and haven't been more than 10% into them for a year. Still learning new stuff, I am!

Time to go out and turn off all the solar panels for a few days :-)

http://www.rollsbattery.com/pdf/BU-RS-614.pdf

[Flux]

Yes it is interesting how battery manufacturers disagree between themselves and how information changes over time.

The lead acid battery has been around a long time but we still seem to be learning and as load conditions change so does the information on how to deal with it.

In the old days few batteries were floated, probably the only major float application was telephone exchanges.

Usually batteries were worked fairly hard in earlier installations. With the coming of solar much of the loading conditions have changed.

A few years ago most manufacturers stated that lead acid batteries on float did not need cyclic discharge.

I am inclined to agree that the occasional high discharge is beneficial as long as you can fully recharge immediately. I also think that an occasional discharge at high current is beneficial if the normal load current is low compared with maximum intended discharge current. It need not be to a high level of discharge to be useful.

What has been found best for VRLA and gell batteries doesn't always seem to best suit flooded batteries.

Flux

[aguillar]

I've asked Surette for wind turbine information equivalent to that in the bulletin which is purely for PV.

They have replied but no info yet..

[aguillar]

Helpful responses from Surette: [paraphrased slightly to read as one]

With a 2 step wind turbine charge controller such as with the Proven 2.5 it is really on and then off (i.e. float / below gassing).

In this case, look to set the regulator to the high side of the recommended settings.  Your primary concern is getting the batteries charged and, if this is not a problem with your existing settings, I would not change.  However, if you are experiencing trouble getting the final 10%, or so, into the batteries, I would recommend increasing the charge voltage.

Now, once voltages are increased, the concern becomes water loss.  If watering intervals (of any amount) are less than 60 days, this is a general indication that the voltage settings are too high.