Solar MPPT to house or starter with DC-DC connection?

[ss2016]

I have a 150Amp alternator which charges a 300AH house bank and a 100AH starter sealed lead acid batteries through an Argodiode. The Argodiode senses the o/p voltage on the output to the starter battery and compensates the voltage loss across the diode.

I added a 100W solar panel to keep the batteries topped up through a Victron MPPT when in the marina which charges the house bank. Also, a DC-DC Victron from house to the starter battery. (Coming from sail I have a major concern about the engine not starting!)

I have noticed that on a 2hr run the alternator does not get the house batteries back to a full state of charge. I am wondering if I used the solar to charge the starter and dc-dc to the house bank if this would cause the alternator to work a little harder resulting in a better state of charge in the house bank.. The logic for this, and I am far from sure its correct, is that with the dc-dc feeding from the starter battery to the house bank while the engine is running , would slightly lower the starter voltage, thus causing the alternator to work a little harder. This would result in a higher o/p voltage not only on the starter bank but also the house bank.

Thoughts? Experience? Thanks.

 

[simonfraser]

on my mobos the alternator / solar charges the starter battery first
then a victron cyrix battery combiner to put the spare charge into the house battery

 

[PaulRainbow]

I have a 150Amp alternator which charges a 300AH house bank and a 100AH starter sealed lead acid batteries through an Argodiode. The Argodiode senses the o/p voltage on the output to the starter battery and compensates the voltage loss across the diode.

I added a 100W solar panel to keep the batteries topped up through a Victron MPPT when in the marina which charges the house bank. Also, a DC-DC Victron from house to the starter battery. (Coming from sail I have a major concern about the engine not starting!)

I have noticed that on a 2hr run the alternator does not get the house batteries back to a full state of charge. I am wondering if I used the solar to charge the starter and dc-dc to the house bank if this would cause the alternator to work a little harder resulting in a better state of charge in the house bank.. The logic for this, and I am far from sure its correct, is that with the dc-dc feeding from the starter battery to the house bank while the engine is running , would slightly lower the starter voltage, thus causing the alternator to work a little harder. This would result in a higher o/p voltage not only on the starter bank but also the house bank.

Thoughts? Experience? Thanks.

I think it's worth a try, as you have all the equipment to do it. The limiting factor is the resistance of the lead acid house bank, which you might be able to mitigate somewhat by setting the absorption voltage from the DC-DC charger to the max permissible for the batteries.

 

[ss2016]

Thanks! I might have to get one longer cable made up.