DIYbanter - View Single Post - lead acid battery charge-discharge

bert[_3_]

In message ,
writes
On Sun, 13 Apr 2014 02:40:49 -0700 (PDT), wrote:

On Sunday, April 13, 2014 9:24:29 AM UTC+1, wrote:

Following on from the thread about second use for old electric car
batteries: surely as end of life is reached for any cell the self
discharge increases and thus a higher proportion of the charge gets
expressed as heat?

if thats whats causing its end of life.

OK what modes of failure are there and how do they manifest
themselves?

If you mean electric power, you'd get far more heat for far less by
harvesting from the exhaust, or even the engine coolant.

I'm talking about 150W element heating 5 litres of water through 45C,
the unit costs ~£250 and requires 27Ahr from cold which takes about an
hour. I don't know how well it is insulated to keep warm during the
shift. So I may get more heat from the exhaust or a diesel heater but
the capital cost wouldn't warrant it.

As it is a tractor battery (644) will easily manage the demand but the
issue is will it get charged enough in the average commute (about 40
minutes). The split charge facility protects the vehicle battery as it
only closes above 13.5V but I need something to inhibit the heater if
the auxiliary battery falls below 50% DoD or about 12.2V.

AJH
Voltage sensitive relay as used on caravans these days?
--
bert