Recovering a Odyssey

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Jul 17, 2025
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Hi, I have 5 year old 60Ah Odyssey, did not drive the truck for a couple of weeks and battery voltage was 10.5V. I have a very old and cheap 6A battery charger. Put that on and eventually the charge level meter was bouncing between 100% and 50% with voltages of 14.8 and 13.6 respectively so I think the battery is in a damaged state. When I remove charger and rest the battery voltage is 12.5V (50% charge). Truck starts OK but I ran it for an hour (alternator reads 14.1V) and no improvement.

I have ordered a proper 20A charger and per Odyssey method of reconditioning is to drain battery to 10.0V under load and then charge with AGM charger.

A few things I'm wondering -

I assume I can run the charger repair function on an AGM? It appears AGM's have a voltage limit of 15.0V but according to NOCO datasheet repair cycles are 16.5V. Is this OK because its not continuous? It seem that people have recovered badly damaged AGM's by using repair function. I would only use after above reconditioning procedure to reduce sulfation.

The reason for buying this battery is because I often park at desolate trailheads and although I will not intentionally deep discharge the battery I wanted a battery which has best chance of starting and also one where life wont be impacted as much as lead acid after discharges so less likely to end up with failed battery on the road.

My first AGM was a red top Optima bought about 20 years ago. That battery lasted 12 years even after a few deep discharges. One time the truck would not crank but I waited a while and it self recovered enough to crank. Needless to say, i was very happy with this battery. I then bought another red top but that lasted only 5 years after only 1 discharge, no better than a good lead acid. At that time buzz on the internet was that Optima quality went down so I decided to go with Odyssey. I knew about the very specific 14.6V charging requirements but since I would not intentionally discharge, I figured it would be OK. This appears not to be the case since Odyssey needs 14.6V to charge properly. I looked up Optima charge requirements and they are same as lead acid, 13.6 to 15.0 volts will fully charge.

So I'm thinking actually the Optima is probably better for someone who may have an accidental deep discharge on the road after all, since the Odyssey has such specific charge requirements. Probably a yellow top. Best solution is dual batteries but I dont car camp that often. I considered dual batteries at one point and I realized that a dual battery system with Odyssey would require a permanent DC input charger (fed by alternator) which adds cost and complexity.

Thanks
 
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NOCO does not make an Odyssey approved charger. While it is not mandatory to use an approved charger, these are the situations where it might be important.
https://www.odysseybattery.com/charger-comparison-tool/

"To get long life from the ODYSSEY battery, it is important that the battery is kept near full charge, approximately 12.8V. If there are electrical loads during storage, then the negative battery cable should be disconnected or an independent float charger used. Low power 2.0 amp chargers for storage charge will keep a fully charged battery fully charged but cannot recharge if the ODYSSEY battery becomes discharged."

I know plenty of friends that use Odyssey batteries with a regular AGM battery tender without issue. (I did on my Odyssey)

Is it possible your truck has developed a drain on the battery when parked? It is also possible the battery has simply prematurely failed.

Optima red tops are terrible. I went through three of them, all leaked. I hear their yellow tops which are a traditional plate type AGM are better...but I am done with that brand.
 
.....I assume I can run the charger repair function on an AGM? It appears AGM's have a voltage limit of 15.0V but according to NOCO datasheet repair cycles are 16.5V. Is this OK because its not continuous? .....
I say don't deviate from Odyssey's very detailed instructions about TPPL battery reconditioning. They say do not exceed 15.0V at any time during the procedure. The repair cycle on my ProLogix 20A charger did do some damage to a Northstar TPPL battery I had.
 
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A few weeks shouldn’t have drained the battery unless somethings drawing from somewhere. I’ve left my car set at Detroit airport for a couple weeks many times, even let it set for 5 weeks. @ $35 a day the companies light fluttered when I turned in that expense report.
 
A few weeks shouldn’t have drained the battery unless somethings drawing from somewhere. I’ve left my car set at Detroit airport for a couple weeks many times, even let it set for 5 weeks. @ $35 a day the companies light fluttered when I turned in that expense report.
Yeah, need to check the draw. Its an ancient truck also, 1998 Tacoma so should be low draw. Only thing different is I now have one of those USB charging adapters that shows the batt voltage.
I also got one of those small solar panels with battery float charger.

AGM's are now what you get at the chain auto parts stores if you get the longer life batteries. I got the store brand for another car and it is AGM but of course its not deep cycle. I doubt it requires 14.4V to charge though. I suspect in most cases in a mildly discharged Odyssey will fully charge at 14.0V - I think the 14.4V (and 40% of 10hr rating) is to "overcharge" it perhaps to improve life. My main mistake was using a weak, oudated charger. They say that proper charging replaces 105% of the discharge.

I happened to see in the Odyssey manual that the 15.0V limit is to prevent outgassing so I sent an e-mail asking if repair is OK? Will report back.
 
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I have a battery minder 2012 agm charger. It’s made supposedly for higher end agms, Yuasa, oddysey and some others but I just have a clarios agm made for Nissan in the wife’s 2024. Before I bought it, I called battery minder and their tech guy told me it would overcharge my battery. 355 spider turned me on to unplugging the temp compensation which did lower the charging voltage. My next batteries will probably be oddysey…just because. I can tell you for certain, that everyday driving without charging will discharge my wife’s agm, way more than those same habbits will discharge my car (same model) but older that has a flooded battery, same alternator set up. I’ve simply concluded that agms aren’t made for today’s smart charging systems. Now in a 98 Tacoma? I have no clue.
 
I have a 14 yr. old Odyssey in my Harley. Yes it was installed in 2011 to replace the factory battery. Still cranking strong. Always on a BatteryMinder 1.5 temp compensated maintainer when in the garage. So much for specific charging routines Odyssey recommends.
 
Why not just buy a $75 jump pack and before you head out on your hike, pop the engine and put it near the battery. Leave a note on your steering wheel so you dont forget about it before starting the car. I just figure leaving a jump pack in a car that will reach maybe 130 degrres for days at a time would not be good.
 
I have a battery minder 2012 agm charger. It’s made supposedly for higher end agms, Yuasa, oddysey and some others but I just have a clarios agm made for Nissan in the wife’s 2024. Before I bought it, I called battery minder and their tech guy told me it would overcharge my battery. 355 spider turned me on to unplugging the temp compensation which did lower the charging voltage. My next batteries will probably be oddysey…just because. I can tell you for certain, that everyday driving without charging will discharge my wife’s agm, way more than those same habbits will discharge my car (same model) but older that has a flooded battery, same alternator set up. I’ve simply concluded that agms aren’t made for today’s smart charging systems. Now in a 98 Tacoma? I have no clue.

I think the newer cars have much more draw when off because of alarms and the safety systems. On the review for the solar trickle charger one guy said he has a new 4Runner (which he does not drive frequently) and lost 3 batteries before he wised up and got a trickle charger.

I measured my current draw with nothing on and its only 10ma so I think what happened is battery was repeatedly undercharged because of low use and short trips when used. I did one reconditioning cycle and battery ended up at resting 12.7V so it improved. Will do again as they say good to do more than once.

I think commodity AGM's are fine for cars because it appears if you buy the longer life batteries thats what you get by default (and many cars come with AGM's now) although I searched on "can you use AGM battery in any car" and they say some older cars may overcharge AGM's. Odyssey float is 13.5 - 13.8 and most old alternators run 14V. Some cars that came with calcium batteries run much higher voltages so that is what they may be warning against. From what I can tell, overcharging really means that it will cause the acid to boil.

If your newer car sits for more than a week at a time I would get a trickle charger, the solar type are more convenient IMO. Conventional lead acid may only last for 2 deep discharges and then fail later without warning. The advantage of even commodity AGM is they can survive many discharges. Also, they give warning when they are end of life so it may prevent you from being stranded. On my Optima I noticed when it finally was end of life it gave plenty of warning as I noticed cranking was a bit slow and this persisted for weeks. When I replaced it still cranked the engine.

What kills batteries is sitting at a low charge level for extended periods because it causes sulfation buildup. I thought the repair mode on the chargers was marketing but I saw a reference to a study that was done and it does work but it has to be done correctly and for an extended time. I saw a post that claimed only Batteryminder and Foxsur do it correctly. If you have a dead battery and charger with repair mode its definitely worth trying and many people have reported recovering a dead battery. I'm waiting on a response from Odyssey on this.
 
I have a 14 yr. old Odyssey in my Harley. Yes it was installed in 2011 to replace the factory battery. Still cranking strong. Always on a BatteryMinder 1.5 temp compensated maintainer when in the garage. So much for specific charging routines Odyssey recommends.
I think that’s a testament to the power of using a charger of any kind.
 
I think commodity AGM's are fine for cars because it appears if you buy the longer life batteries thats what you get by default (and many cars come with AGM's now) although I searched on "can you use AGM battery in any car" and they say some older cars may overcharge AGM's. Odyssey float is 13.5 - 13.8 and most old alternators run 14V. Some cars that came with calcium batteries run much higher voltages so that is what they may be warning against. From what I can tell, overcharging really means that it will cause the acid to boil.
Odyssey wants 14+ when charging. Whether by a car alternator or wall charger.
Float is different, and can be lower...but is temperature compensated. It can be over 14vt if your garage is in the teens or twenties, but can be 13vt if it is in the mid to upper 90s. I have run AGMs in many cars without issue...a 1978 Ferrari 308GTS (Optima red top), to 2001 BMW 540, and many many other cars that never came with an AGM originally. Never had an issue and always longer life than a flooded battery. The issue with batteries is they are fickle products and seems there are always outliers, like a flooded Toyota oem battery that lasted 14 years in my Tundra...or the two crappy flooded East Penns that failed in less than two years each. Or the three red top Optimas that all leaked in less than two years each. (no more Optima for me, or East Penn)
 
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