DF300AP Low Voltage Alarm

[white diamond]

I am getting a "low CAN bus voltage < 9" alarm once and a while when cranking the engine. It has only happened when the engine is already warm. Both of my batteries are a few years old but have all new cables and battery switch. All connections rechecked. Both batteries were fully charged and reading 12.4 and 12.5 volts before cranking and it has happened when switched to either battery. Any ideas?

[Moonlighter]

Those batteries still look low to me.

See this info on battery charging and scroll down to the table in yellow.

https://www.emarineinc.com/Batteries-Maintenance-101

This states that batteries showing 12.4 to 12.5 V are only between 80-85% charged. Did you get a reading on how low they dropped when you were cranking?

Be a good idea to have them fully charged up, then load tested. This will tell a more complete story.

Also, there should be a inline fuse in the network power cable connection. Remove it, clean and reinstall it to be sure its clean and the fuse holder is likewise in good condition.

[redlowrey]

Start your engine on both batteries, your batteries are probably down a bit and Suzuki ecm's don't like low battery voltage. The reason, there is no built in software for voltage drop, that is why they want you to install batteries with huge cca capacity so the cranking voltage will not drop below 10 volts. Go to a Suzuki car yard and lift the bonnet and have a look at the size of the battery, and you will get a shock.

[white diamond]

My batteries are 800 MCA. I guess I will need to buy new 1,000 MCA batteries.

[redlowrey]

My df 140 started beeping about eighteen months ago when starting on one battery, I just start it on two.

[Harper]

My batteries are 800 MCA. I guess I will need to buy new 1,000 MCA batteries.

800 MCA should be plenty. The thing is, you cannot depend on any outboard to fully charge the batteries. Every time I go home from a weeks fishing trip, the batteries go on a charger, right after the boat gets cleaned. I always do that before I put it away. And if it sits for a couple months I hit it again with the charger before trailering to the coast.

Consider that that 4 liter engine has only a 54 amp alternator, and it's charging two batteries. A car engine that size would have 80-100 amp alternator standard or 150 amp heavy duty for a single battery.

My batteries are seven years old now, and have never given me a problem.

[ChrigelKarrer]

I have 2 800 mca batteries on my 29ft DF300AP rib,
one for the engine, one for the electronics and a Perko to combine them in case of a dead battery.
In the last 3 years i never had a problem with low voltage using only one battery.
As your low CAN bus error comes up when cranking, your batteries probably have problems to deliver all 800mca during cranking due their age.
You may get another set of 800 mca batteries (or at least the engine battery) and install a PERKO in between.
The engine battery should be a starting battery like the Optima Red Top and they claim also that they recharge faster.
Chris