I spent the last few weekends renovating part of Iris' electric system. I already mentioned in a previous post that I replaced the Vetus 108Ah house battery, which had lost capacity over time. To prevent this from happening again I removed the most trouble-prone part of the system: the 1-2-both switch, and replaced it with a a more reliable microprocessor controlled battery combiner.

A classical 1-2-both switch can fail; it can be turned off with the alternator charging, destroying alternator and electronics; it can be left in the "both" position, flattening both batteries or one can forget to put it in "both" while charging and find oneself with a dead battery at the most inopportune moment.

The solution I opted for consists of a dedicated starter battery, directly connected to the starter motor and the alternator, and a dedicated house battery connected to the distribution panel through a simple on-off switch. The house battery is connected to the AC shore power charger. Both batteries are connected to the Cyrix 80 battery combiner. The battery combiner is a microprocessor controlled heavy duty relay that automatically connects the batteries in parallel when one of them has reached a preset voltage, and disconnects when the voltage decreases below float level. When the combiner senses that the starter battery has reached its connect voltage it will engage to allow for parallel charging of the other battery. Likewise, it will also engage if the house battery is being charged by the battery charger. I chose for the battery combiner instead of the typical diode isolators, because the latter introduce a voltage drop leading to undercharged batteries which could be desastrous over time. Below you see a scheme of the new setup.

As can be seen on the photograph at the top of this post, I also renewed the panel on which the new elements are mounted, and included on it a basic voltage indicator and the waste water level indicator.

Future electricity projects might include replacement of the battery charger with a more intelligent one, including an Amp-hour monitor (instead of the voltage indicator) and tidying the cabling behind the distribution panel.