Why do battery needs a float current?
I mean, when it's full, floating and there are no loads? To fight the self-discharge, alright. But it draws a bit more than self-discharge would require. I have 300 AH AGM bank, self-discharge ...
Forum Discussion
PS: I shouldn't have made fun of BFL13. It's just that I envy his Trimetric monitor :)...
He was right that "monitor" needs power, and my controller as a monitor needs power too. There is 5% loss in MPPT conversion, yes, but there is also a fixed amount of power that controller draws all the time: 0.9W typical operating power, 1.5W maximum (with backlight and other things On, though they were Off in my case). Let's agree on 1.2W - easier to divide by 12V - so 0.1A is accounted for, 0.2A still remains.
3 other possibilities:
1) 10ft #8 booster cables (20ft total 2 leads) from controller to battery. (There is also a voltage sense wire so let's not go into voltage drop). This resistance shouldn't result in 0.2A current, no?
2) As I couldn't clip booster cables to controller posts, I clipped them to a pair of scrap wires #12, each piece 1ft long, and screwed those wires to controller posts. So there is additional resistance in these #12, and also on all the jaws of the booster.
3) I've badly damaged my AGM during 10-11 months storage when they self-discharged to 60% SOC, as described in other post. Though this SOC is not terribly low, and other than mysterious runaway Float current the batts behave well. Load-test of one battery with 100W 12V bulb (repeated twice) showed that it has retained its full capacity - and then cr-appy Chinese bulb burned out so 2 other batts were not tested. But they all show the same daily AH intake if floated one by one.
He was right that "monitor" needs power, and my controller as a monitor needs power too. There is 5% loss in MPPT conversion, yes, but there is also a fixed amount of power that controller draws all the time: 0.9W typical operating power, 1.5W maximum (with backlight and other things On, though they were Off in my case). Let's agree on 1.2W - easier to divide by 12V - so 0.1A is accounted for, 0.2A still remains.
3 other possibilities:
1) 10ft #8 booster cables (20ft total 2 leads) from controller to battery. (There is also a voltage sense wire so let's not go into voltage drop). This resistance shouldn't result in 0.2A current, no?
2) As I couldn't clip booster cables to controller posts, I clipped them to a pair of scrap wires #12, each piece 1ft long, and screwed those wires to controller posts. So there is additional resistance in these #12, and also on all the jaws of the booster.
3) I've badly damaged my AGM during 10-11 months storage when they self-discharged to 60% SOC, as described in other post. Though this SOC is not terribly low, and other than mysterious runaway Float current the batts behave well. Load-test of one battery with 100W 12V bulb (repeated twice) showed that it has retained its full capacity - and then cr-appy Chinese bulb burned out so 2 other batts were not tested. But they all show the same daily AH intake if floated one by one.
