deep cycle battery

[rowdycowdy]

Gidday all

Just looking for a bit of advise on the benefits of a 12v deep cycle battery vs normal 12v batterys.
I am using it for an electric motor. I already had one a 12v 33ah deep cycle but due to ignorance of how fragile they can be I overcharged it and killed a cell. :'(
I am considering a 70-85ah this time to run my electric motor and sounder.
How much longer would I have with this type of output? and yes I know now to use an automatic charger!!!!!!!


Cheers!!

Rowdy

[joey_1987]

How big is your boat and what is the size of the motor? I would probably go something about 130amp hr because it is better to have more than less and also you don't ever want to discharge below 50% or you will reduce the life of the battery. Joey.

[BlitzBaga]

The automatic charger you are talking about, is it a small unit about 60 or 70mm square?

[oddbudman]

Use a deep cycle battery for an electric trolling motor. A deep cycle battery is more suited to the application than a standard battery and will cost you less in the long run. Standard batteries are more suited to starting car engines and other applications where large current is required in short bursts.


Lead acid batteries for automotive use are not designed for deep discharge and should always be kept at maximum charge, using constant voltage at 13.8 V (for six element car batteries). Their capacity will severely suffer from deep cycling, due to sulfation, or hardening of the lead sulfate. Specially designed deep-cycle cells are much less susceptible to this problem, and are required for applications where the batteries are regularly discharged. Also, marine batteries are something of a compromise between the two, able to be discharged to a greater degree than automotive batteries, but less so than deep cycle batteries. http://en.wikipedia.org/wiki/Lead-acid_battery

Battery capacity is measured in Amp hours (Ah) (smaller batteries are measured in milli amp hours (mAh) - thousands of an amp hour).

For example, a 12V 10 amp hour battery will be able to power a 1 amp load for 10 hours before the battery is empty.

Likewise, in a more real world application, a 12V 130Ah deep cycle battery will be able to run a Minn kota that uses 33A continusly when trolling for
130Ah / 33A
= 3.93hours

This figure is a tad optimistic (i haven't put in any losses) but it does give an idea on how to compare battery to battery.

Hope this helps.
oddbudman

[fishingrod]

Battery capacity is measured in Amp hours (Ah) (smaller batteries are measured in milli amp hours (mAh) - thousands of an amp hour).

For example, a 12V 10 amp hour battery will be able to power a 1 amp load for 10 hours before the battery is empty.

Likewise, in a more real world application, a 12V 130Ah deep cycle battery will be able to run a Minn kota that uses 33A continusly when trolling for
130Ah / 33A
= 3.93hours

This figure is a tad optimistic (i haven't put in any losses) but it does give an idea on how to compare battery to battery.

Hope this helps.


Yes, it is correct that all batteries have a Amp/Hr rating, but you need to read the fine print. The Amp/Hr rating is rating is normally given at a certain discharge rate.

Drawing 1 amp for 130 hours might be feasible. But it is unlikely you can draw a steady 65 amps for 2 hours from the same battery.

Ask the retailer for the full spec sheet and see if any discharge curves are available b4 buying.

What Joey said about not going below half capacity is also true. Most deep cycles will handle going fairly flat, but it will shorten their life long term. Never plan to go below half capacity