T&T: Wiring diagram for adding inverter to DC system (long)

[Truelove39@aol.com]

We have been working on a similar project, and thought that sharing  what 
we've learned might help answer some questions.
 
We're giving our Balmar 95-165A alternator a big brother to help it  charge 
our 1500Ah AGM house bank. We'll replace it with a Balmar 95-210, which  is the 
same machine with larger windings. The 165 is now driven by a 1" serp  belt 
(Lugger 668D); an engineer at Lugger told us that belt will drive the  Balmar 
98-310 as well; we considered that machine but opted for the 210 for the  sake 
of interchangeability as we already have another 165 on  the wing engine. 
We'll mount the 165 in place of the original 40A  start battery alternator and 
drive it off the front pulley with two 5/8"  v-belts. These belts are overkill 
but will eliminate any slippage if they  get a little loose, say, on a long 
passage. These are good machines with  oversized bearings and are cheap to 
maintain - we replace bearings and  brushes every 2000 hours. Unless they get too 
hot, they should last a long  time. Currently, we limit our 165 to 90% or just 
under 150A and it never exceeds  180F degrees in a 120F degree engine room 
 
The start battery (for main and wing engines) is a single 4D and is now  
charged via an Echo-charge unit. We tried a combiner, but didn't like the  idea of 
simply switching the 4D on and off-line with the 8D house bank. There's  an 
emergency parallel relay in case the start battery fails. 
 
The fields of both machines will be supplied from a single  Balmar MC612 
regulator. According to Balmar, this is the only  regulator capable of supplying 
enough field current to drive both machines  to full output. The Xantrex XAR12 
will work too; it is almost identical, but is  a bear to program. The engineer 
at Balmar told us that the different  alternators' outputs will be 
proportional, that is, they should both  put out their respective rated current. He said 
it's important to splice  (solder) the 2nd field wire no more than an inch 
away from the regulator,  and to change the regulator supply fuse to 15A. Even 
though the available  output will become 375A, we will use the regulator's "amp 
manager" to limit  outputs to 90% unless alternator temperature dictates a 
lower number. This  will give us 337A, and as our underway load is around 40- 
60A we'll have at  least 277A, or 18% of capacity available for recharging the 
house bank. We  may just buy another 210 at some point and keep the 165 as a 
spare. This would  give us an output rate of 300A or 21% of capacity. All these 
charge rates  are maximums (at 12V) and will decrease somewhat as the voltage 
climbs during  bulk charging. 
 
We also learned that ammeter shunts should only be used at 66% of  their 
continuous rating. This is because if they get too hot their resistance is  
permanently changed and the calibration will be off. We could not match the  
original ammeters but since one was a 150 and we needed a 300,  we will replace the 
existing 150A shunt with a 300A shunt. Since  they both have a 50mV output, the 
meter will read 150 when the current  is actually 300. We will simply put a 
"X2" label on the ammeter. 
 
Initially, we Googled for the best price on the alternator, but got  
something like 40% off list from Defender, who beat our best quote by almost  $100. We 
had also been shopping for a good battery monitor, and recently  purchased a 
Link 2000 on Ebay. We have the Link 2000R on the sailboat and have  been very 
happy with it. Balmar has a lot of good information on alternator  selection 
and pulley sizing, etc. on their website. _http://www.balmar.net/_ 
(http://www.balmar.net/)   We get our shunts  from Deltec. 
_http://www.deltecco.com/catalog.html_ (http://www.deltecco.com/catalog.html)    We like switchboard shunts 
rather than meter shunts as they have a lower  profile. Jack Rabbit offers a 
200-0-200 or 300-0-300 ammeter with  shunt  _http://tinyurl.com/y7r9eu_ 
(http://tinyurl.com/y7r9eu)    
 
No connection with any of the above companies.
 
 Regards,
 
John
"Seahorse"
lying Jacksonville FL