Two Advanced Marine conversions experienced problems with battery chargers last week after particularly deep discharges. I've been a strong advocate of the DualPro PS-4 chargers, and have installed many, including in our own Ericson 27. Last week, San Francisco Bay hosted the Blue Angles and many others to perform for several hours to the delight of many. The Tradewinds Sailing School had their Catalina 30 out, and it spent many hours running under power, far more than usual. It came back with fully depleted batteries, and was plugged in dockside upon its return. The next day, the chargers were showing odd levels of charge, having been plugged in all night. Normally, the boat charges fully overnight. We felt the charger, and it was piping hot, a condition which caused one or more of the chargers to drop out. This probably had happened the day before as well, and as a result, the boat had gone out without a full charge in each battery. After 24 hours on the now fan cooled charger, we had all green LED's, thank goodness. The second boat, a Columbia 27, had a similar situation when the charger timed out.
Brian, the Mainfuse at Trunderstruck-EV, advocates bulk charging for just this reason. He's had several instances where a fresh string has been ruined by an individual charger dropping out and one or more batteries being reverse polarized. Consider that the string current flows through each battery equally, and when a cell is only partially charged, that same current will gradually cause the voltage on the weak cell to reverse as a result.
In conclusion, I'll still use a multiple output charger for equalization every so many cycles, but from now on, all new conversions will get chargers for the entire string. Leaving the dockside with one flat battery is far worst than leaving with a partially charged string. Thanks for the advice, Brian. I wish I had listened the first time...
Arby Bernt
Advanced Marine Electric Propulsion
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