Battery Safe Mode?

[25yearslater]

Here is a strange situation that perhaps I might find an answer to. In March of this year I purchased 2 Group 27 Dual Purpose batteries from Autozone. The last few times I tried to start my engine battery #2 failed to provide enough power. Battery #1 is fine. I have rotated between using the two to keep them charged. Returning the offender to the store they ran a check and found it at 23% charged. When I tried charging the charge indicator rose to 60% then fell back to 23% several times. The battery is currently at 98% at Autozone after they charged it. I explained I was charging at 10 Amps and they recommend 4 as anything above that causes the battery to return to safe mode. Any technical explanations for this phenomenon?

 

[Don S/V ILLusion]

My first suggestion is never to take advice from anyone who tells you a battery has a "safe mode".
If you charger works on one battery but not another, there is only one variable in this scenario.


Batteries have a rated acceptance rate of somewhere in the order of 20% of their rated capacity. Not knowing what batteries you have, I can't tell what that equates to in charge rate but certainly you can.

 

[Stu Jackson]

Don's right, you got a lemon. Return it and get a true deep cycle battery. Dual purpose batteries are not good for either start or deep cycle. A really dumb marketing idea.

 

[Maine Sail]

"Battery safe mode."......:Liar:

As Stu said get some good deep cycle batteries made for deep cycling.

Here's a hint about good quality deep cycle batteries, they do not have the little charge indicator hole/window.......

Starting or hybrid "dual purpose" batteries simply do not hold up well to cycling applications.

Also remember that it can take 10+ hours to fully charge a battery from 50% SOC to 100%. You may also have a parasitic drain on that battery..... 4A vs. 10A should make no difference what so ever except for how long it takes to bulk charge..

 

[Mike B1026]

Don't some batteries have to have so much voltage in them, before some chargers will properly charge them? I vaguely remember something about AGM's and charging. Seems like you had to hook a very low battery in parallel to a charged battery to fool the charger. Maybe that was what the guy was referring to as "safe mode" (for the charger)??

 

[25yearslater]

Here's where it all stands. 2 identical batteries. No chargers other than the alternator on the engine. Simple 1/2/Off switch. No loads of any type as entire system is switched off at dock. Just had some less than pleasant words with surly kid at Autozone over situation. Bottom line, Autozone will not honor warranty. Since I had planned on yearly replacement batteries guess who won't be on the list of vendors. I knew safe mode was a crock of crud. Nice part about buying two at a time is if one fails in identical use it's easy to tell where the problem is. Thanks for the confirmation information. You guys and gals are the best. Next year straight deep cycle batteries.:cussing:

 

[Don S/V ILLusion]

Here's where it all stands. 2 identical batteries. No chargers other than the alternator on the engine. Simple 1/2/Off switch. No loads of any type as entire system is switched off at dock. Just had some less than pleasant words with surly kid at Autozone over situation. Bottom line, Autozone will not honor warranty. Since I had planned on yearly replacement batteries guess who won't be on the list of vendors. I knew safe mode was a crock of crud. Nice part about buying two at a time is if one fails in identical use it's easy to tell where the problem is. Thanks for the confirmation information. You guys and gals are the best. Next year straight deep cycle batteries.:cussing:

Good plan with one exception. Buy good quality deep cycle batteries and take proper care of them and they will last 5 or more years.