Battery Isolator

[boscoe99]

mucho complicado. 2-cycle engines not so good for charging, not like 4-cycle.
I got two batteries with switch, and one extra battery, not connected. when one battery dies, I switch to second one. so far haven't used third one yet. but same piece of mind will provide re-chargeable battery, like Portable Jump Starter Duralast 700.

Mucho complicado?

No, no mucho complicado.

Muy simple.

Nothing to do. It is all automatico.

[99yam40]

Let's take the starting battery. Before start it will be approximately 12.7 volts if it is fully charged. The relay in the combiner is open. After starting the motor the battery voltage will be slightly less than 12.7 volts. Once the generator starts feeding voltage to the battery the battery voltage will rise. Once the battery voltage reaches 13.3 volts the relay will close and parallel both batteries. The generator output of course will rise to more or less 14.5 volts. Both batteries will then be charged at the same time by the generator.

Just because I have never done it before, I would have to check with a meter to see if the voltage at the battery would take a period of time to come up over the set point with the motor running.

I would think the voltage imposed across the battery would be almost immediate when RPMs came up and generator started putting out. Of course I do not normally have a battery that is low on charge when cranking up to start out with.

It does sound like a good product

[boscoe99]

How quickly the starting battery rises to 13.3 volts is a function of the generator output current and the state of charge of the starting battery. In my case it would take about a minutes time before the relay would close.

I had two digital voltmeters in my boat. As soon as the motor started I would see a voltage rise on one meter. Upon closure of the relay I would then see the voltage rise on the other gauge.

If the house battery was low, here is what would happen. I would see the voltage rise on the start battery. The relay would close and I would see a voltage rise on the second battery. If the second battery was down on a charge it would draw a lot of current, in which case the voltage would drop on both gauges. The relay would open at which time I would see generator voltage only on the start battery. Shortly thereafter the relay would close again and both batteries would be in parallel and getting a charge. This process might repeat itself about three times before the relay would stay closed (voltage above its set point) and both gauges would indicate the same voltage all of the time.

When the motor was turned off both gauges would stay at about 14.5 volts. About several minutes later the voltage would drop below 13.3 volts and the relay would open, isolating the two batteries from each other. The combiner has an LED light that illuminates when the relay was closed.

In my case it took all thought about battery management out of the equation. At the start of the day I turned on two battery switches. At the end of the day I turned those same two switches off. Never a worry about having both batteries getting low on charge at the same time.