Battery compartment venting

Originally Lionheart was fitted with gel cell batteries. These batteries do not give off gas when charging (unless something goes very wrong) and therefore do not require venting of the battery compartment.

These batteries eventually wore out and were replaced with standard deep cycle lead acid batteries which do require venting. Often no forced venting is required. In the case of Lionheart the batteries are under the seats in the boatman's cabin and could very easily build up substantial quantities of highly exlosive gases during charging.

As a SmartBank was already installed, the relay output of this was used to provide power to two small fans (of a type certified for use in explosive atmospheres) which suck the gases out of the battery compartments.

I use the power save feature of the SmartBank so this runs the fans at approximately half speed which is sufficient during light charging. If permanent full fan speed was required there would be two ways to achieve this. One would be to disable the power saving feature of the SmartBank (see the owners manual), the other method would be to use the output of SmartBank to energise another relay which then feeds power to the fans.

(The SmartBank power save feature uses pulse width modulation techniques to reduce the power consumption of the battery paralleling relay by roughly 50%. It does this by providing a full power pulse to the relay to ensure fast and efficient relay closure then reduces the applied voltage by 50% - this same reduced voltage will also be applied to the fans hence the reduced operating speed).

In my case I preferred to not have the fans running at full speed all the time (due to the noise all night when on shorepower). So another (slightly modified) SmartBank was installed which operates at a higher voltage. This SmartBank provides full voltage to the fans when the charge voltage exceeds a higher level.

The result is the fans do not operate at all unless the batteries are being charged. Up to around 13.6 volts the fans run at half speed. Above this voltage the fans run at full speed. So at high charge rates the fans run at full speed. When on float charge they run at half speed and hardly make any sound at all.

Connecting the outputs of the SmartBanks simply involves 1 diode to be put in line to prevent the fan only SmartBank from providing full power to the split charge relay.

Click here to see the new simpler, almost free, way of achieving the same result with the latest SmartGauge software revision. Also includes a full wiring diagram.


Web site and all contents Copyright SmartGauge Electronics 2005, 2006, 2007, 2008. All rights reserved.
Page last updated 02/04/2008.
Website best viewed on a computer of some sort.