MS 34HT Charging System Mods

I finally finished a write-up of an upgrade I completed on my '08 MS 34HT charging systems and thought a post here might be helpful to others.

My signature includes a link to my "Bacchus" website that I've created.
One section of the website describes boat projects I've undertaken.
One of those projects was modifying the MS charging circuits for both the main engine alternator and the shore powered charger.

Here is a link see - Alt & 110V Charging System Mods
or you can go to the "Bacchus" website link below and go to Projects Pg 4

Any questions or comments - fire away

Hi Don:


Yes Mainship's use of a diode isolator is a crappy way to do things. I owned the flybridge version of your boat in the mid 2000s and the wiring was the same except I had no genset and no stern thruster.


Had I really wanted to improve the DC system, I would have installed a high output alternator with external regulator like Balmar's, wired it to feed the house battery bank (4- 6v GCs) directly and then charge the starting battery and the thruster battery with a combiner. I wouldn't bother with isolating the starting and thruster batteries because those don't need much charging and the high voltage of the regulator in its absorption stage for the house batteries should charge them ok.


But that scheme would have cost at least a thousand dollars and some new 00 wire run, so I lived with what I had. As it turned out we never stayed on the hook long enough without motoring somewhere else that the Hitachi couldn't keep up ok.


David

djmarchand said:

Had I really wanted to improve the DC system, I would have installed a high output alternator with external regulator like Balmar's, wired it to feed the house battery bank (4- 6v GCs) directly and then charge the starting battery and the thruster battery with a combiner.

David

Click to expand...

David...
I though about doing as you suggest but couldn't justify the cost & work to do it. I don't particularly like the arrangement MS installed w/ start & house batt'ys together. I have considered separating them but the rewiring gets more involved than I cared to take on...for now.

We do spend a few days at a time on the hook but so far have found the current arrangement more than sufficient. I'll run the gen for AM coffee and usually to cook PM and that keeps batt'ys at reasonable SOC.

I generally run with both 8D start/house batt'ys combined with the Sel Sw... My rationale is larger banks stay at higher SOC and are better for the batt'ys.
If I ever run them too low I can fire up Gen set to charge and/or combine Gen batt'y to start main if I'm going to travel and charge via main alt.

Slightly off topic question for you...
Do you have any idea why MS would put fuses on both sides of the thruster batt'y On-Off Sw?
I get putting it one side - and I say the batt'y side of the Sw would be the logical one - but why on both?

Yes, particularly with your genset which will keep the batteries charged up on the hook, you don't need to spend the money on a high output alternator.

To your fuse question, the first fuse closest to the battery makes sense as it protects the wire from over current supplied from the battery if there is a short downstream. But the second fuse on the other side of the switch is unnecessary.

David

Hey Don,

Do you have an SOC on your house bank? If yes, where did you mount it?

Dougcole said:

Hey Don,

Do you have an SOC on your house bank? If yes, where did you mount it?

Click to expand...

Doug...
No...though about it but haven't taken that step. I did add remote to my house charger and monitor that way when using house charger at dock or when I run the gen. Mfg of SOC didn't recommend w the way MS tied start & house together...wasn't ready to tackle rewiring...yet. So far I haven't had any problems but keeping an open mind.

Thanks for the input. I guess I need to trace everything out first. I'm pretty sure someone was trying to work around a problem with this rig. I will go down the weekend and start tracing out and putting it down on paper. After that I can figure out what needs to be rewired.
Jeff.

your website and documentation are top quality, Bacchus. thanks for creating and sharing it