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Forum Index : Solar : my LYP battery equaliser at work
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Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
2014-10-09_115020_04-10-2014_log.compressed.pdf This PDF shows the 24 hour battery log on a sunny day. The effect of the equalising is clearly shown as the day progressed. 2014-10-09_115227_05-10-2014_log.compressed.pdf This PDF shows a 24 hour period when there was cloud, rain and sunshine at times. The battery still got up to equalising potential. The big dip in the graph in the morning is caused by the electric kettle. The smaller dips are the two fridges cycling on and off. The battery bank is 24V, 200Ah of LYP winston batteries. In parallel are 400 Ah of sealed lead acid batteries which are always on float level, they are for in case if the lithium low cell voltage (set at 3.2V) should tip - has not happen yet. Batteries are charged from 2Kw of solar panels. Daily consumption is around 3KWh which equals ~75-80% of electric power. My inverter is too small to connect 100%. Klaus |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Very interesting Klaus. Can you tell us more about the hardware? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Glenn, it was discussed at length here What is shown on the pics of the above URL are my early attempts at this idea. It has progressed a great deal since, to the extend the individual cell charge is being sensed by a picaxe program and charge transfer done as required by the lo cell from the hi cell. That process runs as long as the battery bank accepts charge in excess of 1A or so - no point wearing out the relay contacts during non charging times. It is also necessary to add shunt regulators to each cell to prevent the individual cell voltage rising too high, the supercap system was shown being too slow for that during the equalising time. Klaus |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Nice. Been thinking of building something along the same lines. I was planning to use a PicAxe circuit across each 6v battery, isolated with a couple of optocouplers to a master control, probably a Micromite. The individual PicAxe's would monitor the battery voltage and send the data to the master controller. The master then sends a signal back to any PicAxe reading high, and the PicAxe would PWM a dump resistor. Each PicAxe would have its own power supply off the batter its monitoring. Calibration would need to be done manually, and checked every month or so, as a PicAxe reading wrong would pull the battery bank out of equalization, not good. No two circuits are ever the same. But been no rush to build a equalizer, my battery bank has remained well equalized since I first fired it up almost 3 years ago. The most I see is 0.03 volts difference between each 6v battery. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Glenn, I assume your 6V batteries are lead acid types. Don't forget the picaxe chips run on 5V so monitoring 6V+ is not straight forward. Your picaxe/ dump resistor plan sounds complicated. I would just use a suitable heatsink on a series shunt regulator at the battery terminals. Using a TL431 (quite cheap @ RS electronics) you can precisely adjust at what voltage the shunt springs into action. A big heatsink (for a TO220 darlington) is only required if the battery is way out from the others, once they are equalised they stay that way and the darlington does not even get warm at full equalising voltage. At least that is what I experience with my LYP battery bank. Klaus |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I see no problem with monitoring the 6v as its just 2 resistors in a voltage divider, but where it can be tricky is a 5v supply from the 6v, as a basic Vreg needs 1.2v above the output voltage to work, but then again there is LDO regs and other methods to solve that problem too. I do question what sort of RF will be generated by PWM a resistive load?? Pete. Sometimes it just works |
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