Originally Posted by David Rive
This coming weekend I want to install a new Raymarine A128 MFD on my boat. The installation manual says not to connect it to batteries that are used to start the engines. So here is my problem - the boat has two Group 31 AGM batteries, one for each engine. There is no separate house bank, because the previous owner was always connected to shore power - he never anchored out. High on my to do list is the creation of a new house bank, but it just has not been done yet. So if I connect the new electronics through the panel to my 2 starting batteries, am I going to damage the Raymarine unit, as its instructions seem to suggest?
Perhaps each of your batteries supplies separate house functions, too?
We have two battery banks that each do triple duty: start, half the house, and bridge (one for electrics like nav lights and so forth), one for electronics. These batteries can be paralleled on demand in case of starting issues, and we also have a separate stand-alone genset battery. It's apparently quite a common set-up.
Rather than creating a separate house bank, I just added capacity to each bank. What started as 2x Group 29s (I think) each bank from the builder is now 3x Group 31s each.
Our plotter -- and all other electronics -- are connected to our starboard bank. We (mostly) remember to have all that stuff turned off when starting that engine. The few times I've forgotten, it's caused a reboot on the MFD and a low voltage alert on the A/P, so far nothing worse.
I might change that starboard bank to 4x golf cart batteries whenever necessary to replace the current G31s -- even more capacity, and enough cranking amps to start that engine.