Equipment | Battery management

Battery management

The DC 'house' batteries on a sailboat are the powerhouse for the boat. Good batteries and power storage management is really important to me, especially on Jocara where we use a lot of power for electronics! We burn up around 250-300 AmpHours a day! Let's start with the batteries themselves.

Jocara carries 8 x 6-volt Trojan T105 batteries, configured as 4 x 12-volt pairs, as her main battery bank, giving us 620 Amp-Hours storage at 12 volts. The Trojan T105's are fully-flooded lead-acid deep-cycle batteries intended for use in golf carts, where they need to be able to give high transient output and be able to withstand being run very low. They are not a high-tech as sealed lead acid or gel batteries, but are perhaps the most robust and long-lasting, as well as being considerably less expensive than other types.

I write the purchase date and cost in paint pen so I know roughly when they can be expected to start degrading and what it might cost me to replace them! I also tie a short length of line so I can lift them out of their tray under the floor and still count all ten fingers. In the picture you can see 6 of the batteries (the other 2 are in an adjacent compartment), together with a little black temperature sensor block that the Xantrex DR charger/inverter used to monitor battery temperature (part of it's control to avoid overcharging or charging too rapidly)

The house battery bank is charged by our 12-volt generator, solar panel and a high-output (120 amp) alternator driven from a pony shaft on the main engine, externally regulated by a Xantrex smart regulator.

This external alternator regulator from Xantrex is a 'smart' 3-stage charger that also allows for engine warm-up, ramps up the alternator load and gives a complete diagnostic readout via a set of LED's in the sealed but transparent potting compound. It is virtually indestructible, pretty-much waterproof (all the innards are potted) and when your alternator burns out or gets flooded when the cooling circuit on the motor leaks or boils over, this keeps on working and can be used on any other alternater you choose to fit.

An absolutely critical component of the battery management system is the charge monitor, without which I would only have a crude idea of how the batteries are doing. The charge monitor isn't just a voltmeter... Measuring the voltage is useful, but doesn't tel the whole story by a long chalk.

This 'oldy-but-goody' monitor from Xantrex (which came with the DR charger/inverter) gives voltage, current draw, percentage storage remaining, net amp-hours drawn since last full charge and can also be used to monitor the battery efficiency (how much energy do you lose in a charge-discharge cycle?) to give early warning of battery degradation or need to top up the water levels. It also has low voltage and low charge audible warnings and whole lot of other bells and whistles. This panel also used to control the DR charger/inverter and had temperature sensors on the battery. here it is set to display the amps draw (or charge rate). Now I just use it to monitor the battery state.

We also have a 40 Amp-Hour single 12-volt battery in a separate compartment, recharged by the usual standard-output (40 amps) alternator on the main engine with integral regulator.