Starter battery bad- replace with dual purpose battery?

[KatBalouE350]

Sternwake, the charger brought the battery to full charch in about an hour and forty minutes then floated. I did like you suggesred and unplugged the charger, plugged back in and set to agm. It then read battery was at 97 percent. Will leave it as is overnight. Thank you SW for this heads up and directions  and everyone else for all the input. I have much to study!

 

[SternWake]

I am surprised it read 97 percent. the voltage should have been higher from the recent charging, well over 13 volts, and it should have seen this surface charge, and proudly( and wrongly) claimed 100%.

Often brand new batteries exhibit unexpected weirdness that goes away after the first discharge and recharge, in my experience. I bet the Shoemaker on the AGM setting will hold 13.6 or 13.7v overnight and stuff in the last few percentage points.

If you cycle the battery, I'd recommend plugging in again and floating overnight on the AGm setting whenever it is convenient to do so.

There is no danger that the battery will not start the car if not performed, but the lead acid battery ideally always wants to be 100% charged. This takes time to achieve and one can seriously offset any degradation if they choose to insure the battery is indeed fully charged, rather than thinking the alternator does so every time the vehicle is driven.

If everybody did this, batteries would cost less as they would last longer and be in less demand with much fewer warranty returns

 

[tripper]

I had a Costco grp 27 Marine Battery, I was pretty hard on it, only lasted 3 years.

I replaced it with a Trojan grp 27 Deep Cycle, I would say about 30% increase in real world capacity, excellent battery. There is at least one Trojan distributor in every major city, look on their website. I have no complaints about the Trojan.

I am testing out a grp 27 LiFePo battery that I got off of Ebay for $650 (new with built in BMS). It has been rock solid, drop in replacement, even looks like a conventional battery case. Kind of making up my own Bulk/absorb and float voltages on the fly. Right now 14v bulk/absorb and 13.2 float to be conservative. Battery is doing extremely well, holds a rock solid 12.9v under load, never sagging. I believe I would get more capacity at a 14.2 or 14.4 charge, but it hasn't been needed and supposedly lasts longer if you don't 100% charge the lithiums. So far the battery has been great, if you are considering $460 for a Firefly battery it is not that much more for a $650 LiFePo. The LiFePo is so LIGHT, maybe 1/3 that of the Trojan's weight.

Haven't had the LiFePo for years yet so I can't say about long term other than it should go for 8-10 years.