Marine battery box setup critique

[questionsandanswers]

Inspecting battery box on a friend's newly purchased boat:



Looks messy. Any reason why the PV inputs of the battery box would be filled, but all devices are connected directly to + and -? No DC bus?

-Can't find bus bar - should this be bonded? Should it be re-wired so devices are fused through a bonded bus bar, using the box closed? It looks as if in the cabin, each device is individually fused (some lights are directly connected to the batter)
-As far as I know, no inverter present, only DC - anyone seen a setup like this?
-PV inputs filled (unknown capacity). No engine present (sailboat only) so no other means for grounding. Unsure how they are grounded, or if they need to be.
-Battery monitor shows 13.3v float
-Shows full charge but only 36.7 aH capacity- is the battery dying?

Open to suggestions on next steps how to make sure this is usable and safe.

 

[wholybee]

Several issues there. Add both positive an negative buss bars, so that there is only one wire coming off the battery terminals. Add an MRBF fuse on the battery. Replace all those cheap crimp terminals with quality heat shrink type like ancor. Make sure the battery is secured so it can't move.

You can not tell much with voltage on a Lithium battery. Probably the monitor is programmed wrong, and that is why it is only showing 36.7Ah of capacity. What brand monitor and charger?

 

[sailingcal21]

What size boat? Adding buss bars would clean it up. However, after a few years the owner will be chasing down lots of inline fuse issues. I'd suggest that a DC panel be installed along with a battery switch.

 

[questionsandanswers]

It's a 24' but very spacious. Not sure what brand of monitor + charger, will have it checked.

Looks like the following could be done based on above advice:
-MRBF - inline to DC devices
-Secure battery
-Close lid, attach battery terminals to inside of batt. box
-Buss bars to + and - of battery box
-Battery switch
-Heatshrink + better quality terminals to above setup

Thanks

 

[mikefitz]

In my view the main issue is lack of fusing. Evert conductor connected to the battery positive terminal needs overcurrent protection suitable to protect that cable, The protection should be as near the battery as practical.
suggestions,
fuse box, either a 6 way or 12 way

ST Blade Fuse Block - 6 Circuits with Negative Bus and Cover - Blue Sea Systems

Compact ATO® / ATC® fuse block consolidates branch circuits and eliminates the tangle of in-line fuses for electronics and other appliances.

www.bluesea.com

MRBF fuse,
https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

Work out the maximum loading on the battery, this will allow you to select the value of the MRBF fuse and the cable within the battery casing, and external to the fuse box. Connect the MRBF fuse holder and fuse to the battery positive, cable to the casing terminal. A negative cable of the same rating from the battery negative to the case terminal.

With the same gauge cable connect the positive and negative from the case terminals to the fuse box. 8 AWG cable and a 40 amp MRBF fuse would be my guess.

The circuits can now be connected to the fuse box, different sized ring terminals may be needed. Fuse each feed to/from the fuse box to suit the appliance/charger and cable connected.

Its useful to have battery isolation subject to solar regulator tolerance on being disconnected from the battery.
If an isolation switch is used this is fitted between the battery case positive and the fuse box.

To avoid possible solar controller confusion/damage there should be a switch in the panel feed to the solar controller to disconnect the panels.

Mike