Hi Bill (and Stu),
I sketched out Bill's suggestions and this is what I have come up with so far:
https://docs.google.com/drawings/d/1VRENYHbv6qBBLnnyforSkuSci7X3w7Uar0T5L6tdx54/pub?w=960&h=720
The goal here was for me to understand what I'll be wiring by drawing it out but two questions remain. One, does the alternator only charge the house batteries and two, does the solar panel (controller) only charge the start battery? Besides those two issues does the sketch seem accurate to what you were suggesting? Also, if I were to add voltage meters where would they go in the drawing?
Thank you,
Alex K.
Primetime
My suggestions would be:
#1 Use the house bank for everything including starting, keep it simple..
#2 Use the start bank as an emergency / reserve bank. Paralleling a dissimilar battery during discharge is not recommended. During charging it is fine but during discharge I would advise against it.
#3 Battery Monitoring - What works well for Bill generally works less well for the vast majority of boaters. A good battery monitor is $155.00, less than groceries/beer for one weekend. Each 0.1V is 10% of your banks capacity, how accurate is your volt meter? I have yet to see more than 1-2% of boaters who can keep accurate track of battery SOC via voltage alone and do so somewhat well. This is not to say it can't work, but those I know that can do it, accurately, are few and far between.
I have NEVER installed a single battery monitor for acustomer that did not RAVE endlessly about how great it was and how they should have done this long ago, how it is the best value for the money of any boat upgrade they've done, and how now after 30 years of boating finally understand "charging" etc. etc......
I have had customers text me at 2:00am just to say "Got up to check the anchor and glanced at the battery monitor. Everything was so good with the bank I decided to leave the fridge on and not have warm food in the morning, THANKS! Never would have done that without the monitor." The next morning I got another text saying that I just saved him $65.00 in steak, chicken and other foods that his wife would have thrown out had the fridge gone above 40F.
#4 Switching - If you reside on a dock and your batts start every weekend full then just use the house bank and ignore the starter battery until you need it in an emergency. If you only do a one week or two week cruise you can get by with no charging of the start battery as self discharge over two weeks is a non issue. Keep it simple leave it set to HOUSE. Needless switching back and forth leads to errors I call HEF, or human error factor. I am on my way out the door in a few minutes to install a Balmar Duo Charger for a customer who killed both banks last summer by forgetting to switch back to the HOUSE bank after charging BOTH banks.
#5 Charge Routing - Route all charge sources, solar, wind, alternator, battery charger etc. to the house bank. If the alt is still fed through the "C" post of the batt switch using the house bank accomplishes the same thing. DO NOT SWITCH THROUGH OFF with the engine running if the alt goes through the battery switch. I have to rebuild numerous alts every summer due to blown diodes from passing through OFF with the engine running. Have a Yanmar alt on my bench right now with blown diodes.
#6 Charge Management - An ACR, Echo Charger or Duo Charger are invaluable tools for many boaters. They fully automate the charging of the start/reserve bank without the need to ever touch the battery switch. Leave it on HOUSE and the charge management device takes care of the START battery. They never forget to isolate the banks and never forget to charge them. These devices are very, very reliable so reliable that one of them, the Yandina Combiners, carry an unconditional lifetime warranty.
HEF is real (perhaps not for Bill
), I deal with it all the time and charge management devices, like the battery monitor, is one of those items my customers LOVE..... The cost of these items is small in comparison to changing a battery bank every two to three years or getting towed or burning up a starter due to low voltage/current.
On average I would say my customers who've done nothing but a battery monitor and charge management device get 2-3+ more years out of a bank than they did prior.
An ACR and Victron BMV-600 will run you about $255.00. My advice on this is not from an n=1 pool of data. It is from doing this for n=LOTS of real customers who use their boats in the real world and have had real issues with short battery life, blown diodes from constant switching, HEF etc. etc..
I even had the daughter of a customer come up to me on the dock and personally thank me because her daddy was no longer a "electricity scrooge"....
Keep in mind that starting an M-25 will use fractions of an Ah of capacity from the bank. This is why devices like the 15A Echo Charger never need more than 15A of current to keep a start battery "topped up". Most often a start battery will be taking less than 2A of charge current, after starting, and this usually drops to under an amp relatively quickly...
Many ways to skin the cat. I still suggest a battery monitor and then a charge management device if you are on a mooring or off cruising. It seems you already have a charge management device? As long as it is not a diode isolator, I would keep it.
