Battery maintenance help

[Carverlvr2]

I realize this is an older thread, but hopefully not too old? I have the same year Ish and same model Ish boat, 2004 366 and I’m just learning the systems now. How do I know if my original onboard charger can handle AGM batteries? If so, can it handle mixed? Like flooded for the starting batteries and AGM for the house batteries?

[km1125]

There's not a whole lot of difference between AGM and standard flooded batteries in their charging profile. You might get a little more life out of the batteries with a charger that has an AGM-specific profile, but mistreat the batteries just once (like run them dead) and that advantage is likely gone.

[Carverlvr2]

Thanks for the AGM info! Ability to charge both types together helps explain what’s possibly going on in the boat. Two previous owners so there’s been some additions.
Ok. There’s the two OE chargers on the boat. A single bank that only charges the genny battery and (from what I’ve read) a three bank: a bank for each starting battery and one for the house battery plus the last PO added a second house (in parallel) to make that one big bank…easy enough, both are group 31 lead acid batteries and I’m assuming the same ah capacity. They’re also charged off the alternator(s).
Here’s the catch: The first owner added two SPP2150 Stinger AGM batteries for the stereo. They’re wired in parallel as one bank as well but the PO said they’re charged off the main charger too. That’s where I’m lost.
1. How can they be charged by the same bank on the charger as the two house batts but not all be wired together as one huge bank?
2. and each set possibly has slightly different ah capacities. The Stingers may be nearing 10yrs though.
3. And since the house is charged by the alternator, wouldn’t the stingers be too? Any insight is appreciated. I have 20+ yrs in automotive electronics but this is beyond my experience.

[bud37]

If it were me I would go thru all the wiring and batteries with a good tester, watch what is getting charged and when then see what is connected to what and at what point....for example some could be wired thru the battery 1/2/all/off switches if you have them. There really is no other way to tell what was previously done or changed by owners before.

Once you get that all drawn out , then will be time to decide on new batteries if that is the direction you want to go in.....my two cents anyway......good luck with it..it will be worth it, trust me.

[Carverlvr2]

I hadn’t thought about those switches. On this one I think they’re just on/off but will certainly look closer next time I’m out there. Thanks!

[km1125]

The PO may have added something like an VSR (voltage sensitive relay) to allow the Stinger batteries to get charged along with the house batteries. But, yes, if that was the case then the stingers would also get charged when the alternators are running.

But as Bud says, you really don't know what you have until you trace it all out and figure out what's been done since it left the factory.

And 10 year old batteries are living on borrowed time. They might still have enough capacity for your usage, but only a fraction of what they had when new.

[KyleR]

As an FYI, my OE house charger was a Charles charger and the data plate on it said it was for GEL type batteries only (see pic). It had been used for who knows how many years before me charging the house flooded lead acid batteries - probably not doing them any favors. But that's a different story. I never realized it until it died and I had to replace it. Just something to consider.

[km1125]

Source of the post As an FYI, my OE house charger was a Charles charger and the data plate on it said it was for GEL type batteries only (see pic). It had been used for who knows how many years before me charging the house flooded lead acid batteries - probably not doing them any favors. But that's a different story. I never realized it until it died and I had to replace it. Just something to consider.

GEL batteries are definitely a different animal and need the appropriate charger.

[Carverlvr2]

Ok, so I have the same Charles C charger, 5000 SP series single bank for the Ben and 60amp three bank. I can’t get to the back wall to take it down and verify it’s setting but found this clip from the manual that states their factory set for Gel. Did our boats originally come with gel batteries? Better question, how bad is that charging profile for the flooded lead acid batteries that are in there now?

[paulr]

Speaking of batteries. How do you determine the "state of health" of a bank of 5 batteries. Do you need the disconnect each battery? Is there a special test instrument? Or do you use a load tester like you would with a car?