Battery Talk - What is "Charge Cycle"

[Mustang65]

Everyday we hear that we should only discharge our batteries to 12.0Volts, known as the 50% rule, and you follow that rule to a "T". Then you look at the manufactures "Life Cycle Chart" for your battery, it says you should get about 1500 cycles using the 50% rule, with proper maintenance. Well, how long is 1500 cycles? Do you count the times that your battery is recharged? Once a day?

Good Question!!

The actual definition of a "Cycle" is the "Charge Cycle", so does that mean that if I bring my battery down to 50% that is one charge cycle? Actually, "NO"!! In the battery industry the guide lines for a charge cycle is the actual discharging of the battery till there is no power left in it, or 10.5 Volts (SG=0). 100% discharged!! But wait, you only discharge the battery 50%... what gives here.

Well, lets say you have a 100 Ah battery and on Monday you end the day only using 50% (then recharged to 100%), Tuesday 20% (then recharged to 100%), Wednesday 15% (then recharged to 100%), Thursday 15% (then recharged to 100%)...... Now you have your 100% discharge. So, 1500 cycles could take a long time. Oh, but wait don't forget to add "The AGING PROCESS" into the equation, some numbers for that are 10% a year and increasing as the battery ages... so your batteries Ah's at 100% charge are not going to be the 100Ah any more. IE: My 5 year old Interstate 85Ah batteries are at 40Ah now (fully charged), test results can be found in the RVing with SOLAR Social Group, under a post "The Numbers are In". Still darn good batteries and just like us aging we are not as strong as we used to be when we were younger. Still looking for a way to recharge my self again.

So "Number of Cycles"?
"In general, number of cycles for a rechargeable battery indicates how many times it can undergo the process of complete charging and discharging until failure or it starting to lose capacity"

The same holds true for any battery type, the numbers just change.



Don


My Registry

RVing with SOLAR

[vcbice]

Well, kinda. The 1500 rule is just a guideline, not hard and fast.

It does depend on how the battery was treated. In the old days of simple chargers there were many cases of abused batteries, overcharging, undercharging, etc. Now days most people have chargers designed by the battery folks that will do the "3 stage" charge and will properly do a 'maintenance' charge. Most also have a 'reconditioning' charge to help revive a battery.

Then there are environmental conditions. Extreme cold or hot weather will affect the life of the battery as well.

Last is the manufacturing. Some batteries just last longer than others, and is not necessarily related to the price or mfg advertising.

I've had batteries last for 5 or 6 years and others that only went 2 years, with the same relative usage.

[jimp]

Every time you discharge a 12v battery down to zero, you shorten the life of the battery. In some cases, a battery that is discharged 100% will not accept a charge, why do you think the battery manufacturers define the "cycle" the way they do?