Quote:
Originally Posted by sailingharry
Do you have real life experience to back that up (in other words, have you used passive balancing and found that the cells get too far out of balance)? Some have indicated that if you routinely hit full charge and get perhaps an hour of day of balancing, passive balancing is sufficient. Then I hear others, such as yourself, indicating that much more balancing than that is needed even with good cells, and recommend active balancing.
It is sometimes very difficult to pick out the difference between theoretical benefits and real life benefits. And as an engineer, I am sometimes too eager to fall into the trap of theoretical perfection.
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This seems like 1 question but requires 2 answers...
To the 1st part - Yes, I do have experience of that situation.
My yacht sat in a marina berth in
Cape Town for several months while refitting, during that time I floated my 400ah house bank (originally well top balanced) at 13.2v (3.3v per cell) on
shore power.
As part of final prep I shut off
shore power and switched to
solar, I found it impossible to set 13.8v bulk/float without running into balance issues - as the bank approached 13.5v the balance went nuts with the high cell climbing into dangerous territory and there was no way my active balancer could keep up (rated at 5A but in reality only balancing at 150-300mA).
In the end I built an external device that could discharge the high cell at 5amps while at the same time
charging the low cell at 5A. I monitored all 4 cell voltages and flipped switches for hours until I eventually managed to get all cells with 10mV at 13.8v
To the 2nd part...
Since doing the above my
batteries reach float for a few hours more often than not, allowing the pathetic balancer to maintain balance.
So in my opinion if your cells are very well balanced and you are getting your bank to 13.8v or higher for a few hours very regularly you will probably be OK.