On 5/11/2013 8:14 PM, tom wrote:
Hi Tom.

What you want is a 3 stage charger. The guy who said the old "clunk",
relay based, chargers are best is way off base.

A decent 3 stage charger lets you set a number of things, all of which
are tailored to your specific battery string.

I have a set with an 80 AH and an 160 AH AGM 12V battery. I charge
using a 200W solar array through a maximum power point 3 stage charger.
The MPP part isn't relevant for you, but the 3 stage adjustments plus
a battery temperature sensor are. You can set battery finish voltage
per manufacturer specs at a specific temperature and then the sensor
drives the rest based on current temperature. The 3 stages finish the
charge the correct way and don't overcharge the string or cause
excessive water loss.

tom
K0TAR



Oops, forgot what I had. Put the string together last year from a 9
year old 66AH and a 4 year old 133AH battery. Each removed from a UPS
system. I've had the 66AH for 6 years on intelligent solar controllers.
Got the 133 last summer for $100 used. Upgraded my solar array to
200w from 33w and upgraded the controller to a 25 amp Solar Boost 2000e.

They sat from November to end of April with no charging. I checked the
voltage last week before I pulled the camper out of the garage for its
first light of the year - 12.80 volts. That is in the excellent range
after 5 months idle.

Best buys on AGM batteries is to look for 3 to 5 year old ones being
rotated out from data centers that demand high reliablity. They are
usually rated for at least a 20 year life. And are 0 maintenance to boot.

tom
K0TAR