Electric plan for 3 banks with Battery monitor

[Sea Angel1]

I have 2 active battery banks - 12 V each), 1 for motor (55 HP) start (100 Ah) and 1 for service (2 batteries in parallel, total 200 Ah). 1 spare battery (100 Ah). This one can be switched separetely on to each bank.
Charging: alternator 115 A through a 3 pole diode bridge - master volt 1603
for 3 banks (motor - service - spare)

PV max 300W, in practice appr. 12 and 18 Amp between 9 am and 5 pm
Wind Gen: strongly varying - in general up to 0 -15 Amp (4 Bft).
Controller output only for 2 banks. this is not sufficient, because spare bank is not being charged. Manual switching required to keep fully charged.
Location: east Med
experience: sufficient charging power in summer.

I want to improve the system and install a Victron BMV battery monitor on the service bank.
A proposal how to improve this system, including the wiring up of the shunt for the motor and spare battery would be much appreciated. A schematic would work out ideally.

[tkeithlu]

I can't begin to design a system for you.

Conceptually: You have input sources and output uses. The goal is total interchangeability. Rig it so that any source can be sent to any battery. Then rig it so that any battery can do any job in a pinch. In my case sources are shore, genset, backup genset, and alternators on the engine (2) and genset (1). Users are house, emergency panel battery, start engine, and start genset. Since the negatives are all bonded, one jumper cable, just the positive side, can reach any battery to any battery, so I can overcome either a failed source or a failed battery in a few minutes. I can parallel the two start batteries if the engine battery is weak, and charge the genset battery from the house bank.

In your case, yes, you need another contoller, so all your sources are ready to go, and then a way to route each source to each bank. Ditto on the down side.

That's as much redundancy as you can get in the system.

Oh, and in mine, there is also a small genset with a pull-cord start. I could wake up in the morning, find the entire boat at 0.0 VDC, pull the cord, and bootstrap the entire system back up and running.

[Adelie]

Philosophical question, what is the point of having the “spare” battery?

I would start by adding the spare battery to the house bank. It sounds like it is not being appropriately charged on its own. I wouldn’t change wiring, just always keep switches set to have this battery in circuit with house bank. This will:
A. Prolong the life of the “spare” battery because of more regular charging.
B. Decrease the rate of discharge per battery (lower C rate) in the house bank which will:
1. increase the usable capacity of the bank more than just the amount of the extra battery (Peukert effect)
2. it will increase the cycle life of this bank because your depth of discharge will be lower.


You have a start battery. If that has trouble starting the engine then try starting off the house bank. If you are feel you need double redundancy the get a Lion auto jump started or super capacitor jump box.

[Sea Angel1]

Hi there,
First of all I wish you a all a happy and healthy new year and good winds from the suitable directions. Also thank you for your input and good ideas to get the most out of the stored energy.

[skipmac]

HI Sea Angel1

I will second the recommendation to go to two banks, one house, one starting.

There several good reasons for this. The best one is that it is better for the life of the batteries. If your house bank is larger capacity then in normal use you will discharge the batteries less than you would if you had a smaller bank. The lower you discharge the batteries the shorter their life.

The other main reason is that is simplifies the wiring, charging, monitoring, etc.

After studying the different setups I decided this is the best way to go.

- One start bank or one per engine for twin engine boats
- One house bank
- ALL charging sources go directly to the house bank. Unswitched but through a fused connection.
- Install an automatic battery combiner from the house to the start battery. I use a Yandina Combiner 100 but Balmar and other companies make these. Then every time the house batteries are being charged the start battery will also be charging BUT as soon as you stop charging the house batteries the start battery is automatically disconnected so it is always charged but never accidentally connected to the house systems and discharged.
- Install a 1-2-Both switch for emergency use if a bank is discharged. I installed mine to feed the starter system as I think it more important to start the engine in an emergency. If the house bank dies I can use jumpers to temporarily power the house from the starter.

[tkeithlu]

I've become a proponent of the "spare" battery that can be isolated from the rest of the house bank because of the location of all the rest of the batteries - as low as possible because weight distribution. That means they are close to an unwanted and unexpected influx of sea water, AKA "sinking," as well. That's the OMG moment when you need your radio.... My spare is behind the instrument panel about eight feet above the house bank.

Ideally, and I'm thinking about it, there should be a diode between the house bank and that battery to keep the spare from discharging when the house bank goes under.

[skipmac]

Originally Posted by tkeithlu

I've become a proponent of the "spare" battery that can be isolated from the rest of the house bank because of the location of all the rest of the batteries - as low as possible because weight distribution. That means they are close to an unwanted and unexpected influx of sea water, AKA "sinking," as well. That's the OMG moment when you need your radio.... My spare is behind the instrument panel about eight feet above the house bank.

Ideally, and I'm thinking about it, there should be a diode between the house bank and that battery to keep the spare from discharging when the house bank goes under.

For this application I completely agree. A small, spare, emergency power source could be a lifesaver and I have just the right spot for one behind my nav panel.