24V options for windlass/thruster

[jonlgauthier]

I want to convert the "manual" paralleling system for the 24V bow thruster for my boat. Right now, the windlass is 12V, but I'd like to upgrade it to 24V operation. A previous owner rigged a panel that will series-connect one of the house banks to get 24V. It's currently a safety hazard - you have to remember to switch to 24V before you use the bow thruster, and you have to remember to switch it back after.

I would have gone to a full 24V system for the entire boat, but it would require changing out all the 12V equipment. So I'm looking at two options:

1. Install a dedicated 24V bank, and keep it charged with a with a relatively inexpensive 120Vac/24Vdc charger. The drawback would be we'd have power the charger from the genset or an inverter drawing off the main house bank. Doable.
2. Make up a 12V/24V paralleling relay and trigger it from either the breaker for the windlass and thruster, or get fancy and trigger it from the windlass footswitches and the thruster control.

I searched the forums and haven't found a comprehensive howto or description of #2. Seems easy enough, but can anyone comment from experience on either of these two options, and point me to a reference site?

BTW: I'm re-engineering the 12Vdc power system on the boat - dedicated engine starting battery and genset starting battery, and am looking at ~800Ah of Trojan 6V AGMs for the house bank. I do have space for two grp 27/31 12V batteries up front if I do go the dedicated 24V route. I'm still trying to decide on a charging system - the new Westerbeke/Century 120hp diesel has a beefed up 190Ah alternator with external regulator, but I'm having trouble finding an AC marine charger that outputs in the 200Adc range. I guess I could go the modular route like an AmplePower system - any recommendations? I have an electrical engineering background, so start with details if you can.

Thanks!

[jonlgauthier]

So, no one's got a hybrid 12V/24V system?

[JimsCAL]

How about going with a full 24 volt system (using four of your 6 volt batteries in series) and run half the 12 volt services off one pair of batteries and and half off the other? Similar to how 120V/240V service is run in homes.

[jonlgauthier]

The hard thing about half and half is to truly split your 12V systems - half the load on one side and half on the other. Not to mention replacing the new engine's 12V system (starter, alternator, instrumentation, etc.) with 24V equivalents.

Granted, if all things were equal, 24V thru the whole system would be the way to go, but the only thing demanding 24V right now is the seldom-used bow thruster - and the more-used windlass (assuming I do the 24V upgrade). IOW - 99% of the time, 24V isn't being used...