Battery Installation Details

Upgrading The Battery Bank

The 435 Battery box  measures 22.5" X 30.25"X 9.5" deep and is located below the cockpit.  It is made of welded aluminum and is bolted in place. It has an outward turning 2" flange around the top, with a seperate, single-piece plywood lid,     With the lid removed, the batteries are partially accessible from either aft cabin.  The electrical connections are made on the port side.    

The one-piece plywood cover is secured to the flange with machine screws and easily-dropped nuts, and it has a 2"X2"  (approx) cleat around its perimeter.   It is bulky and inconvenient in use, and access is more difficult than it needs to be. In this case Alubat did the minimum required to meet only the most basic requirement.  Thankfully it can easily be improved.

Cables enter the battery compartment through randomly-drilled holes on the port side.   There is no positive bus bar, and no fusing at the batteries,    Over time, accessories with a mishmash of fuse styles (or none) have been stacked on the various battery terminals. none labelled, most with no means of disconnect.  The cables intrude into the box, interfering with battery installation and removal.   

The house bank's 4 group 31 batteries were connected in parallel with heavy, well-made jumper links.  With the limited clearance to the conductive cockpit sole above, caution is required when working here, especially with top-terminal batteries.  

The starter battery was/is also in this box, furthest aft.  Access is particularly inconvenient.   

The photos below show:

• how access is restricted by the cockpit, 
• how the cabling was installed and intrudes into the box.
• The many live connections that must be made in an awkward, confined space.    

Below left you can see that batteries must be placed in the box or removed from it in a fore and aft orientation.  Below right shows a pair of terminals in the cockpit locker that were connected to the starter battery.    Presumably this was to provide for boosting or charging.  This DIY hack has been removed, and I will eventually relocate the starter battery to a more accessible location, probably in the port side cockpit locker. 

What to do?

  With the upgrade from 4 group 31 to 2 group 4d (ish) lithium batteries, it became a necessary to re-think the stowage of the batteries, and opportune to upgrade the installation with a bus bar, circuit protection, and a safer, more orderly layout.  There's plenty of opportunity for improvement.

Scope

1. determine battery orientation  ensuring:
1. optimal use of space, 
2. minimal wiring
3. tool-less method to install/secure/remove batteries. (small ratchet straps?)
4. must be easy to reconfigure with - at most - basic woodworking tools.    
5. Battteries must be well secured
6. Ideally, either house or start betteries could be removed while leaving the others in place.
2. design/install distribution and circuit protection for current uses and future expansion
1. Likely this means locating the bus bar and fusing outside of and adjacent to the battery box for better access, however it must then be protected from accidental contact.    
2. it should be easy and safe to disconnect each battery while leaving the other(s) in use.
3. a ATO/ATC "blade" fuse block may be required for some low-current accessory connections.   
3. Improve the cover
1. Cut the existing cover in a fore and aft direction. 
2. Incorporate a tool-less means of securing the cover so that either side can be quickly accessed. 
3. Ensure that terminal fuses can be inspected and replaced from the port side.   
4. Incorporate storage into any unused space if possible.
5. Insulate the interior sides of the battery box to reduce the risk of contact with a live conductor.
6. Provide clearly marked storage for spare fuses nearby.

The Physical part - Thinking inside the box.

Due to the size and shape of the batteries and the restricted access to the box, satisfying the above critieria is trickier than it first appears.  Particularly item 1.6, as the batteries must be placed in the box in a fore-and aft orientation  and then rotated atwhartships if that is the intent.  This creates a bit of an assembly puzzle.   I decided to create a mdf mock up of the box and batteries in the shop to experiment with different approaches.  

I ultimately decided to arrange the batteries as pictured, with a hold down system comprising several oak rails.   I firmly bolted two 2" wide rails 2" above the bottom, at either end of the box.  In the photo these can be seen at each end of the narrow ends of the box. Note that the postive terminals are at what will be the forward end of the box.   The 2" space around the perimeter creates a protected space for the cables and potentially terminal fuses. 

30" long, 2"X2"  movable rails, running the length of the box, are placed in the empty box,  under the raised. fixed rails, which then prevent them from lifting.  The batteries are placed between these.  A ratchet strap can be looped around these movable rails to secure the house batteries.   Wooden blocks can be used in the remaining space to further secure movable rails (and therefore the batteries) laterally.  No tools required.

Parts of Oak

The mdf protoype worked well, so a more refined version was committed to red oak.  Will post pics when the varnish dries.   You can see the short end rails with the M8 bolt holes, and the movable rails with the added refinement of a cleat to secure the hold down strap.  

The Electrical Part - Safe and Simple?

Circuit Protection at Battery box

https://marinehowto.com/battery-banks-over-current-protection/

Based on the info above and the cabling already in place, the following circuit protection should be incorporated. 

1. Battery 1 terminal fuses @150a
2. Battery 2 terminal fuses @150a
3. Inverter charger 1600w/70a (100A)
4. Small inverter.  (40A)
5. 70A Alternator via smart regulator (verify cable, regulator output)
6. House loads (125A per dwg, s/b fused already - where?)
7. Future water maker (100A circuit?)
8. 200W (450W future) PV (50a)
9. 200W Sailgen (50a) 
10. Wind (50a)  **  The wind generator may be retired.

That’s a lot….  Too much in fact.   It will be consolidated.

Bus bars, circuit protection and monitoring

After having purchased the necessary bus bars and breakers to upgrade the DC distribution, I struggled to design a safe and compact electrical layout that would work in the limited space available.  This brought me back to Victon, and their Lynx range.   I had previously ruled this out as being much too expensive, but...   it isn't.     While the lynx shunt wasn't absolutely necessary it provided the opportunity to further consolidate components.   The Lynx Power-In has been "hacked" to incorporate fuses.  (google it) 

The larger fuses and breakers are of a type and rating to protect in the event of a dead short.   This is a topic worth investigating.    So, I wet about building a sub assembly on a piece of scrap polycarbonate that could be fastened to the side of the battery box.   

This too tok some thought.  

 Below you can see the space around the perimeter of the batteries and the oval holes at either end for the battery cables.     The pairs of battery cables will fasten the bus bars (red and black covers in the photo.)  There is very little cable exposed.  

There are fuses on each battery terminal and a very fast fuse in the lynx shunt.  

All other cabling will enter at the bottom of the Lynx power in, where it connects to a fuse and the bus bar.  The shunt is correctly located between all grounds and the battery Hopefully I can simplify and remove some of the massive amount of cabling and trunking that runs beside the battery box!  

Notes

Fuses required 

CNN350DIN.   Fast fuse for dead short, in lynx shunt.

Mbrf for terminal fuse disconnect battery.  There is a problem here in that either end of the wire will remain live.  For disconnect it should be at the lynx shunt.  

Mega (50.8mm) fuses within the lynx shunt.  

Littelfuse makes mega/AMG fuses as low as 40a