Shallow & Deep Discharge Batteries

A deep-discharge type battery should be marked on the label. If it doesn't say "marine" or "deep discharge," assume that it isn't. USA-manufactured marine batteries are usually deep discharge types because they are commonly used with trolling motors and/or the reliability for starting fuel engines is needed (for obvious reasons).

Lead-acid deep discharge batteries are made with thicker cell plates and carriers, and some have slightly higher spacing between plates. When normal batteries are deeply discharged, it is not uncommon for the plates to warp, thereby shorting the cell, usually ruining it.

Working with new batteries, conceptually you would put a high load on each battery. The battery that maintains voltage for longer would be the starting, "shallow," battery although at some point the voltage would drop off sharply, as opposed to the deep cycle battery whose voltage would drop off more quickly initially, but then stabilize at a lower voltage for a longer period of time.

Very hard to do this sort of test without damaging the battery. Essentially the difference is which one will survive being deep cycled multiple times. Not hard to do but at the end of testing you've one less battery!

What's the context of the question. It's unusual for batteries to be totally unidentifiable, and once they're identified simply look up the specs?

You can test deep cycle batteries by using a home made carbon pile tester, we use a 10 amp, Use ohm's law to get the size of pile you needed. I am a Rehab Engineer at a Children's Hospital. For over 40 years I have been testing deep cycle batteries without burning them out. First-- Deep cycle batteries will develop higher voltages each time you charge for the 1st. 20-25 cycles. The life of a deep cycle is between 200-250 charges when used properly. discharge to 11.5 then cooled then charged to 14.5 (29)volts using a digital charger. Heat is the enemy. We recommend recharging only when the voltage gets near 11.5 volts. this is 23 volts in our wheelchairs which gives them between 20 to 30 miles (depending on temp). The three main types of deep cycle are wet (acid filled), sealed lead acid and Gel. Almost all new batteries are the Gel type. We use a Fluke 189 hooked to a Dell laptop to match discharge rates to pair the batteries. Our unused (stored batteries) are floated at 14.5 volts for up to 6 months then sent back to the Manufacture for exchange.

The problem in this instance seems to be using a test to distinguish between deep cycle and shallow cycle batteries. As far as I can see if you use the testing procedure for a deep cycle battery on a shallow cycle battery you're going to damage it before you've ascertained that it's not a deep cycle.

I found your post very interesting, based as it is on years of actual experience. I've always aimed at 11.5 volts for lead acid, it's nice to have this verified. One question though. The higher voltages for the first cycles? Does this mean they require higher voltages for complete charging or they have a higher output voltage? Also how do you verify when they are fully charged. Oops, that's two questions!

Try; www.batteryfaq.org - http://www.uuhome.de/william.darden/

I too have got both battery sorts available as our car batteries are NOT deep cycle, but our caravan battery is.....but all are 12 volt batteries.

I do not think that there is a simple test to distinguish one from the other safely, a point echoed by several other contributors.

If you cannot identify as to what battery type it is by manufacturers details or part numbers etc., then simply assume that it is NOT a deep cycle battery.....

Even with deep cycle batteries, I build my chargers to start to charge once the battery is down to 12.6 volts, and to continue to charge upto a maximum of 13.4 volts, why? you may ask.

Well the answers are fairly simple really, if you want to have a good but simple charging system, 12.6 volts is considered to be the point in the discharge cycle where most non deep discharge batteries start to degrade and 13.2 volts is considered to be the normal maximum voltage for a battery, but to achieve that or should I say, to "nearly" achieve that, you need a period of "overcharging".

By stopping the charging at 13.4 volts (relatively early), I do not actually get a completely "full" battery, which does not bother me at all, but I reduce the exposure to "gassing" drastically and in fact, in 4 years of light usage, but mostly constant charging (within the parameters specified), I have still not had the need to top up with distilled water as of now!! Which leads me to believe that the battery has hardly every gassed at all, as gassing is just the way a battery turns water into two gases, Hydrogen & oxygen......In the caravan, any gases are safely vented directly to the open air. SAlso, no nacked lights every near a battery of this type....

If you want to be more exact in your charging, you need to monitor battery temperature and voltage very exactly all the time, the charger becomes more complicated and therefore more prone to problems.

The normal car chargers are NOT suitable for chasrging anything really and if forgotten, can seriously damage a battery!!! I hate the damn things!!