Battery triple whammy

[ndutton]

A failure trifecta of poor design, worse maintenance and external forces out of my control

Last weekend I went to check on the boat and found, to my great disappointment, warm beer. My house batteries were way down, like 11 volts for both 2xGR31 banks (= 4 GR31 batteries total). It turned out my shore power cord plug had become dislodged at the dock box end, still partially in the twistlock receptacle but not making contact. Either a passerby stubbed his toe on the cord or maybe the strong winds jostling the boat in the slip did it but either way the result was the refrigeration drew down the batteries. No worries about low voltage damage to anything, of the few things I have on when away from the boat, the most vulnerable is the refrigeration and it has a low voltage cutoff feature that protects itself.

I thought I'd start the engine on the dedicated start battery that was isolated from the house loads, a design I've had since I rewired the boat 15 years ago, and let the 100 amp alternator do some serious work. No joy, that battery was dead too, now 5 dead batteries. OK, now I'm wondering if the engine start battery was indeed isolated. Dammit, I know it was so what is going on?

After very little checking I found the engine battery had dry plates. To my embarrassment I could not remember the last time I checked the water levels and to make matters worse, the engine battery was on one of two shore charger circuits 24/7 and it is a conventional lead-acid GR24 battery, not deep cycle. It was pretty clear lack of maintenance and constant charging cooked it but it was also clear its failure was unrelated to the dislodged shore power cord.

So how to make the system better?
I rewired the two shore charger circuits so each circuit goes to a house bank. No shore charging for the engine battery, it will now survive on alternator charging alone, same as a car. There are no sentinel circuits drawing off the engine battery so there are no losses at rest.

I replaced the engine battery and checked the water in the remaining 4 house batteries (all good, a couple of cells needed a minor top off), re-secured the shore power cable making sure it had an ample slack loop. If the deep cycle house batteries tolerated the deep cycle episode we should be good.

[sastanley]

Neil, I have no 120V on my boat. I keep my start battery up with a 5w solar panel + a $17 Amazon controller. Even if I was plugged into shore power, I would probably still isolate my little Gr24 start battery from that system. Your experience does remind us to check on our flooded batteries!

Sorry the beer got warm.

[lat 64]

Definitely sorry about the warm beer.

I'm just learning about agm batteries.
Is that an option for these incidents?

[ndutton]

I'm just learning about agm batteries.
Is that an option for these incidents?

I've limited myself to conventional lead acid batteries, others have different opinions. In fact, these days my preference for old battery tech is the outlier. Reasons for my choice:

• AGMs require a different charging profile (varying voltage) to perform well. That applies to all charge management on board, shore, alternator and solar in my case.
• The higher voltage portion of an AGM charge profile exceeds the voltage specifications on some of the 'appliances' I have in use away from the dock. As an example, the mfr's specification for my electric engine coolant pump maxes out at 14.4 volts. AGM bulk charge voltage is greater and according to the pump specifications, will reduce the pump's life.
• Think about what the higher charge voltage does to the electronic ignition voltage-current balance.

So, therefore and ergo, AGM's are not an option on my boat. Too bad because they pack a lot of punch for their smaller physical size. I tried one years ago without addressing the charging system. Over a Catalina weekend its performance was the worst I'd ever experienced. Besides, with the recent exception of destroying my conventional engine starter battery due to overcharging and shoddy maintenance, my batteries have given outstanding performance and longevity in addition to keeping my electrical equipment happy (within spec). My last set lasted 10 years before their performance began to drop off and remember, I'm running refrigeration off the house banks 24/7. The captain likes his Pacifico's cold.

My conclusion and again, for my boat, is the weak link in the system was me in terms of charging system design aggravated by poor maintenance. As a result of the lesson learned I've modified the design by not charging a conventional battery 24/7 and vow to modify my maintenance behavior. Part of posting the episode here is public admission of my responsibility, the first step in behavior modification.

[joe_db]

Definitely sorry about the warm beer.

I'm just learning about agm batteries.
Is that an option for these incidents?

AGM batteries will go dead too if not charged and can also be ruined by poor charging regimes, so not really.
I am not a big AGM fan myself. I have gel batteries which according to East-Penn Deka can do about twice the number of cycles before being worn out. Gels are ruined by overcharging and need specific regulator settings. AGMs need 100% top-off charging or they get ruined too and also need specific regulator settings.
Also note that many chargers will ruin batteries when left on 24/7/365. My charger has specific settings for various battery chemistries and a temperature probe on the battery. Correct voltages vary with temperature by a fair amount. It also backs off to about 13.2 volts when there is no load, the batteries are full, and it has been on a long time. It kicks back up when it senses a load and I think every few days for a bit.

[Dave Neptune]

Neil, certainly sorry about the beer. At least you can cool it down again.

I would like to ask you to illuminate us with just what your bad experience was with the AGM you tried. I know a few using them that did not and will not change their charging schemes to the AGM specs and left the charging systems as they were for L/A batteries and have no troubles to claim.

When I bought the Bene it had AGM's and all seemed OK. About 6 months after purchasing the start battery went south and I replaced with another AGM. Just after installation my shore charger shot craps. I removed it and was surprised to see it was old school L/A charger and no AGM switch. I replaced with a new charger that was switchable and have been satisfied with performance of it and the batteries. An admission; I did not check the regulator on my Balmar and still have not~my bad, but no issues in 4 years. I am mounting a switch this year to "disconnect" the alt field so when motoring during the day I can use the "solar" while cruising, certainly reduce loads on the belt and engine and even save a bit of fuel.

I also installed a set of solar (300 watts) and a Victron controller with AGM settings. I often do not plug in when I get back from the island and leave the boat for a week or so until the next trip thanx solar. This does exercise my 2 grp 31's at night and by noon in the winter we're back to float. When I know I won't be down for a while I do plug in.

My batteries are starting to age and will need replacing in a year or so I think. I am thinking of going to 3 ~ 31's if I go back to L/A which will give me about the same wattage for safe cycling instead of 2 more AGM's as the cost is about the same. I lean to the AGM's on this boat as the batteries are really hidden under the aft cabin bunks which makes checking a PIA.

Never had any problems with the L/A in 50 years so they are tried and true. I have also had no problems with my AGM's of which the charging scheme was not changed by the PO and still no problem.

Dave Neptune

[ndutton]

My AGM experience

Following shore power charging (fixed point) and a Catalina crossing under power (alternator also fixed point) of my single Optima yellow top AGM (BCI 34, 750 cca), my cabin lights started going dim within an hour after sunset. Loads on during that time were:

• 8" LCD TV = 1A
• refrigeration = 2.2A @ 50% duty
• Halogen cabin lighting = 10A

That calcs to roughly 12 amp-hours drawn on a fresh charge before a noticeable performance drop.

[Dave Neptune]

Did you have the battery checked? Optima has a very good reputation, did they offer to replace and or test?

Dave Neptune

[sastanley]

Dave, I had a buddy with a Bene 343, and I remember helping him haul the PITA Trojans in and out of that aft berth!

[ndutton]

Did you have the battery checked? Optima has a very good reputation, did they offer to replace and or test?

Dave Neptune

No Dave, for me it was one and done. I went back to what had performed well for me for decades, old school lead-acid batteries. I'm not faulting the AGM technology or Optima in particular, the battery was not charged properly with my older fixed point systems but with lead-acid batteries that had a history of performing well and lasting 10 years I didn't have much appetite for a complete charging system rework. Add in the electronic ignition voltage/current balance and the risk of cooking coils with the higher AGM charge voltage. No thanks.

Considering that this episode was my fault all the way I'm not motivated to go the AGM route as a remedy. My old tech battery system works well as long as I don't abuse it.

[joe_db]

No Dave, for me it was one and done. I went back to what had performed well for me for decades, old school lead-acid batteries. I'm not faulting the AGM technology or Optima in particular, the battery was not charged properly with my older fixed point systems but with lead-acid batteries that had a history of performing well and lasting 10 years I didn't have much appetite for a complete charging system rework. Add in the electronic ignition voltage/current balance and the risk of cooking coils with the higher AGM charge voltage. No thanks.

Considering that this episode was my fault all the way I'm not motivated to go the AGM route as a remedy. My old tech battery system works well as long as I don't abuse it.

Wet lead-acid batteries are harder to kill than anything else. One overcharge and my $600 gel battery is done.

[lat 64]

Well!
Ask a question and ye shall receive.

I asked because I just bought a used hipster campervan with a 217 amp hour Northstar agm house battery.
Its charged by a couple solar panels on the roof and managed by a controller that has several charging profiles, flooded lead acid, agm, Lion, Lifepo, etc.
I hoping to get the skinny on this system before I screw it up.

I'm trying to educate myself on the new techo stuff as the world will drag us kicking and screaming to electric modus.
My new ebike kit is Lion, so I'm having to learn that as well. Very particular charging parameters for sure.

Can't fault old school one bit though, old '85 toyota 4runner original battery lasted eleven years before being retired. I attribute that to a well-balanced charging system that I kept maintained.

Charge ahead,

Russ

[joe_db]

I just found out my new (to me) car has two batteries and the aux battery (house loads) died and it was $200 to replace it because only the dealer has the codes to reset the battery management system. The aux battery is an AGM too.

[ndutton]

Post-sortie debriefing

Although the symptom seemed catastrophic (5 dead batteries), the causes were simple to find and easily fixed. Regarding charging a conventional battery 24/7, what was I thinking? I got off easy on expense too, one GR24 battery.

Lot of drama