Center Console Boat-Multiple Batteries Cranking & House Low Voltage

Q&A and troubleshooting
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1

I have a 2018 center console fishing boat with 3 Yamaha 425 XTO outboards. I have 3 cranking batteries and I also have 3 house batteries. All batteries are acid lead. Since we re-powered with new engines our cranking batteries are good and being charged fine from engines through the Yellowfin BEP VSR distribution from the manufacturer. The cranking batteries are showing 14 V on the engine command link and holds steady and the house batteries showing 12.6 V. however when we turn on the 4 live wells the house voltage drops to 11.9 V and never recovers until you turn off the live wells. I have spoken to a few shops and been informed me that Yamaha 425 alternators generate enough to keep the cranking batteries charged and then they only trickle charge the house batteries by design to ensure that they keep power stored in cranking batteries. Now if this is true the only option is to install a DC-DC charger that would rob some power from the cranking batteries to charge back up the house batteries and trick the engines brain to keep the cranking batteries charged while we are pulling power to the house batteries to keep them charged at a safe and healthy 12.6-12.8 V with the pumps running. We had 1 house battery originally but now we have added 2 more so we have 3 house batteries and they are all paralleled together to provide a longer life span but this issues is still there. We do have a massive house draw because we are running 24” screens, sonars, radars, water pumps, lights, radar, seakeeper 4 and 4 livewell pumps. We can run 2 pumps if needed and volts are better but then cant run all our bait wells. The 2 extra batteries were added to aid in the low voltage and for the seakeeper 4 that was recently installed.

I have seen online that people are using the DC-DC charger to achieve this charging issue and having great results if done properly to get the power distributed to the house to be able to run all of the electronics at a safe voltage.

I have purchased 3 Orion DC-DC 12/12-50A (bluetooth Adjustable) units as I have seen mixed information as to whats needed and how to properly run the units and adjust the outputs.

Do you run the DC-DC units single to each battery or do we run them to the buss bars directly from the engines that then feed the batteries? How would we get the unit to feed the house batteries also from this type of set up.

3 Cranking batteries on each their own perko switch with BEP VSR

3 parallel switches incase batteries would ever get weak to crank engines. (batteries are parallel and daisy chained)

3 House batteries all in parallel and when not in use has a trickle charger to keep everything charged (Noco Genius Genpro 10X4)

If anyone can help I would be greatly appreciated for all input. Thanks in advance

2

If all batteries are lead / AGM , then I would use an ACR from each of the starter batteries to a common house bus. Forget the dc/dc converter, these are only needed for voltage changing or current limiting.
ACR’s will connect once the starter batteries are charging, and disconnect once the engine stops.
It would also be possible to set up a “start parallel” bus, where any 2 or 3 starter batteries can be paralleled, by a 2 position battery switch.

3

Thanks for your response Mike.

Im not fluid in this situation and have mixed information but Isn’t that what we already have with the current set up with the 3 cranking batteries running power to the VSRs which should be already charging the house batteries. However we are told Yamaha is controlling/regulating their output therefore and large current draws will never get the supply it needs based off the current configuration. Yellowfin somehow overlooked this back then and always been a issue when you add more electronics and other things like we have now a days. Our factory set up is suppose to do this just like you explained however when we swapped engines to the new ones we are just learning that Yamaha is regulating alternator outputs and only concerned with keeping Yamaha alive and their components like their brains and components and the cranking batteries, they dont product more once they are taken care of for some reason. That info came from a Yamaha rep.

Any thoughts?