Preface
When considering a leak in a sailboat's diesel tank, the first step is to rebuild the core of the 12V DC system.Wait... did I already lose you?
You might be familiar with the urge to chain projects together. When you remove the diesel tank on some of our boats, the primary 1/0 AWG battery cables are exposed -- likely, for the first time since commissioning. In the case of SV Rumour, these cables would be nearly 40 years old. Let's just say I succumbed to the notion rather swiftly. And, that notion to replace some core DC cables then festered into a plan to rebuild the entire system, with overcurrent and short circuit protection, properly sized conductors and a negative buss which wasn't primarily composed of the large diesel-sipping chunk of metal residing in the tiny dungeon under the companionway.
And then more notions. What about creating a larger capacity house bank? Oh look, that old DC distribution panel is looking pretty rusty. Should we consider battery state-of-charge and state-of-health monitoring? What about LiFePO4 batteries? We may need a more powerful alternator. What's the output of our current alternator? We should also think about fault protection in case the lithium BMS disconnects. . .
While the new diesel tank fabrication was underway I had plenty of time to imagine and re-imagine the DC system. I spent a fair amount of time honing a design which made sense and splitting it into phases which could be accomplished incrementally.
The Starting Point
I believe the DC system core on this E32-3 was pretty close to stock, save the pile of small changes made over time by various owners (eg. bilge pump wiring, 12V cigarette socket, the navigation and autopilot upgrade, etc).You can see from the diagram and photo, the wiring plan was simple, unfused, and utilized longer runs of 1/0 AWG battery cable to route everything through the Perko 1-2-Both switch on the main distribution panel. Running all positive connections through the Perko switch also leaves open the opportunity to accidentally turn OFF the Perko switch while the engine is running, which would cut connection to the batteries and cause a voltage spike and blow the alternator diodes. The engine was also serving as the main negative "distribution buss" for the entire life of the boat. This resulted in current being passed through the engine block which likely contributed to some level of electrolytic corrosion.
All of these issues are well-known and usually avoided when newer production boats are wired for direct current.
Design Goals
I wanted to solve a few of the issues above and create a simple DC system which would be easy to operate when everything was working and troubleshoot when not. The most important goals:- Replace as much of the core DC cables and wiring as reasonably plausible
- Provide common bussing, overcurrent protection, and short circuit protection
- Create a larger amp-hour house bank
- Install a separate dedicated engine starter battery
- Provide SOC and SOH monitoring for all batteries onboard
- Provide a roadmap path to LiFePO4 batteries for the house bank
Solution: Remote Battery Switches & New Core Cabling
I chose to use Blue Sea Systems Remote Battery Switches (ML-RBS, Model 7700) and remove the 1-2-BOTH switch out of the system. This provides the advantage of switching the House and Engine batteries as close to the battery/bank as possible while also removing the need for longer runs of large (eg. 1/0 AWG) cable. There would be less chance of voltage drop for high amperage draws, like the engine starter. This also removes quite a bit of cable from behind the main DC distribution/breaker panel which would make wire clean up easier.A nice side effect is being able to de-energize the engine separately from the domestic house bank and panel. I think of this as a minor security benefit since it would be more difficult for someone to hotwire the engine without access to the cabin.
Solution: Common Buss Bars, Fuses, and OCP
I chose ANL style fuses since the amperage ranges from 35A to 750A. ANL fuses also have windows which clearly show whether the fuse has blown or not. And they have attachment tabs which allow one to leave all the mounting hardware in place and angle the fuse out to the side to remove/replace.
For 24-hour circuits, I extended the primary distribution buss bar to a Blue Sea Systems 8-circuit ATC fuse block. This is where bilge pumps, power for the remote battery switches, and voltage meters would land.
I planned on a Blue Sea Systems MaxiBus 250A busbar (Model 2128) to mount on the engine stringer for the engine negative bus. This is an extension of the negative bus from the battery box with an attached 1/0 AWG cable to the engine block to support the connection needed for the starter. All negative ground wires which used to attach directly to the engine block would now land on that isolated negative stringer buss.
Solution: Parallel House Batteries & Charging
The solution will be to join these two batteries in parallel which will provide a single bank with 152Ah. Having two batteries is also a nice redundancy option in case one of the batteries goes toes up. I could disconnect the failed battery from the bank and still be in business until a replacement could be obtained.
Also interesting is the amp-hour math behind these depths of discharge. Let's assume I was to stay within the 50% DOD which is common for most SLA batteries. With a 76Ah house battery and a 76Ah Reserve/Starter battery only used in emergencies, there would be 38Ah usable. By combining the batteries, the usable capacity doubles to 76Ah. Now, assume 80% DOD. Separate batteries would yield 61Ah usable while the combined bank would yield 122Ah usable!
They will continue to be charged by the stock alternator for now, which I believe is a 55A Hitachi. For shore power charging I will be installing a Victron Phoenix Smart IP43 Charger in a 12/50 1+1 configuration. This configuration supplies up to 50A of ~12V charging to a primary bank. It also has a 1-4A trickle charger for a separate start battery. Both outputs utilize the same program, thus require the same battery chemistry to receive each charge. Since there will be a mix of AGM and LiFePO4 chemistries for a while, I will need to find another way to charge the starter battery.
The Phoenix Smart IP43 has a bluetooth app for monitoring and configuration. It also has an remote triggered power on and a programmable relay. I'm not sure how I might use the remote and relay, but it's nice to have options for the future.
Solution: Separate Starter Battery
In order to have a guaranteed start for the Universal M25 engine while retaining the house bank for more domestic appliances, there needs to be two things in place:- A separate starter battery with enough cold cranking amps to start the engine
- A method to charge that battery separately
Some reports state the M25 starter is rated at 1000W.
1000 / 12.5V = 80A.So, for #1 above I chose the Dakota Lithium 25Ah with 300CCA. It's a LiFePO4 battery which can be charged at ~30A (which is above 1C for those of you who like to nerd out on battery math). There are other options for small lithium starter batteries, which usually have smaller amp-hour capacities. There are some small draw appliances in the starting circuit, like the electronic fuel lift pump and several gauges. With 25Ah capacity, the DL+ will start the engine and plenty of extra capacity to run the starting circuit loop appliances even if it doesn't receive a charger immediately.
To keep this starter battery charged, I'll be using a Victron Orion-TR Smart Non-Isolated DC-DC Charger (Model 12/12-30), which can charge at up to a current of 30A. The DC-DC charger will take it's input from the main distribution buss connected to the house bank. The starter battery, charger, and related buss bars will be connected to the engine through another Blue Sea Remote Battery Switch. The Orion TR series has automatic engine run detection which will turn on the charger when the input side voltage raises to the configured level. This eliminates the need to run another wire to the starting circuit to command the DC-DC charger to turn on. The Orion-TR also has a bluetooth app for monitoring and configuring the unit.
Solution: Battery Monitoring
I wanted battery bank monitoring to include both state-of-charge (SOC) and state-of-health (SOH) tracking. it seems like the Balmar SG200 is the prize of the ball. The SG200 has a simple interface on a single 2" gauge and learns over time to determine SOH and other characteristics of a battery bank. I'm also considering moving to Balmar for the alternator and external regulator in the future. I found the SG230 Kit from Balmar comes stocked with Bluetooth and NMEA2000 connectivity, so that battery and charge data can be accessed by other devices on the NMEA2000 network.All negative connections on the DC system are routed through a single SmartShunt. This will be mounted as close the house bank as possible -- in the battery box.
Solution: Future LiFePO4
Building this new core system with combined AGM house bank and separate starter battery should pave the way for lithium conversion. Dakota Lithium has Group 24-sized LiFePO4 batteries with 135Ah each, which would push the house bank up to 270Ah total with a much more reliable DOD.In order to make the switch I would also need to upgrade the alternator for more current and install a voltage regulator and related protection devices to avoid blowing up the alternator if the lithium BMS shuts down.
New DC Design
Implementation in Phases
Most of the product choices and changes described above only cover the core implementation of the DC system for Rumour. Foreshadowing commentary sheds a bit of light on future changes and it was necessary to split these implementations into separate phases. And, there are additional product choices to make for those future phases.Phase 1: Rebuild the DC Core
- Combining AGM batteries for a larger house bank
- Splitting out a dedicated engine starter battery
- New wiring, fusing, distribution bus bars for the core
- New charger for AC shore power charging and DC-DC charging for engine battery
Phase 2: New DC Distribution Panel
- Replace the original Ericson DC distribution breaker panel
- Clean up and re-terminate DC connections behind the panel using terminal strips and buss bars (similar to the journey started here)
- Install the remote battery switch controls for House and Engine banks
- Finish the installation of the SG230 battery monitor
Phase 3: Alternator & Voltage Regulator
- Install and configure an external Balmar Voltage regulator (probably the MC-618)
- Install a more powerful alternator (probably from the Balmar XT series, ~170A)
- Install an alternator protection device
Phase 4: LiFePO4 Batteries
- Replace the AGM batteries with LiFePO4 sized equivalents (probably Dakota Lithium DL+ 135Ah)
Phase 5: Solar & AC Inversion
- Install solar panels and MPPT controllers
- Install AC Inverter for running small appliances (eg. laptop chargers, drill chargers, etc)
Since the aggregate of these phases is a long-tail project, I'll attempt to document and show the work of the phases in the pages that follow. More to come!
Inspiration & References
- https://ericsonyachts.org/ie/ubs/power-update-3-product-selections.966/ (thanks @goldenstate)
- https://ericsonyachts.org/ie/ubs/po...renogy-noco-lithium-installation-w-costs.969/
- https://ericsonyachts.org/ie/thread...universal-m25-and-similar-size-diesels.20458/
- https://ericsonyachts.org/ie/ubs/part-1-a-novices-guide-to-panel-reorganization.143/
Edits & Updates
- 2023-12-05: @bigd14 noticed there wasn't a method for backup starting if the starter battery failed. I neglected to mention in the article above that I left a service loop in the 2AWG cable running between the engine battery buss and the starter. This extra slack could house a small battery switch to cut the starter over to the house bank if needed. This would assume that the house bank would always have enough CCA to turn the engine over. The current AGM batteries definitely do and the Dakota Lithium DL+ 135Ah Group 24 LiFePO4 batteries I'm looking at for the future have 1000CCA each.
