Boiling Batteries

[Frigast]

Hi,

When I came on board my C30 the other day, I realized my batteries were boiling. I shut of my battery charger and sake of good order also disconnected my shore power. I was puzzled as to why they were boiling as I hadn't been on board for a few days and I would have thought that the batteries were fully charged. What puzzled me even more was 10 min. after disconnecting all power the batteries were still boiling.

I have 2 Flooded Lead Acid Deep Cycle 75 AmH which are being charged by an OLD Pro Mariner 30 battery charger (see attached photo).

I am thinking that my battery charger is over charging the batteries, but I would be very pleased to hear your input on my situation.

Thanks!

//Frigast

 

[dlochner]

I am thinking that my battery charger is over charging the batteries, but I would be very pleased to hear your input on my situation.

That would be correct thinking. Be careful when removing the battery charger, it weighs about 35 pounds! A nice new Sterling/ProMariner charger will weigh in at 5 lbs. and not murder your batteries.

https://shop.marinehowto.com/products/sterling-procharge-ultra-battery-chargers

https://marinehowto.com/installing-a-marine-battery-charger/

 

[Frigast]

Thank you for the swift reply @dlochner
I have actually been looking into a new battery charger (specifically the ProMariner series), but I'm still trying to wrap my head around the sizing of same. As per the article you have linked a "minium of 10%" is advised. Is this of my total battery capacity or per battery? In my case 150 AmH total capacity vs. 75 AmH per battery.
I had initially been planning to update to a ProMariner 1220p.

 

[dlochner]

The Sterling chargers and the ProMariner chargers are the same except for the graphics. Different branding for the same charger.

Size the charger for the total size of the battery bank plus some extra for house loads which might be on when charging. With ~150 ah of battery bank, a 20 amp charger would be sized correctly. If you ever think of increasing the size of the battery bank, say go to 2 6v golf cart batteries, which would yield about 200 ah, then you want the next size larger, 30 amp charger.

Spend some time on the MarineHowto.com page to read and understand batteries and charging. Time well spent.

 

[Stu Jackson]

which are being charged by an OLD Pro Mariner 30 battery charger

Nope, that charger is MURDERING your batteries.

Here's why:

http://c34.org/bbs/index.php/topic,5078.msg43151.html#msg43151

I would never, ever plug that POS in again.

You may also be interested in the rest of the topics in that linked thread. We call 'em critical upgrades for a reason and most of them apply to your boat, too.

Critical Upgrades http://c34.org/bbs/index.php/topic,5078.0.html
and this one, too:
Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

Good luck.

Dave's right, BTW. As far as battery charging is concerned, it all depends on how you use your boat. But even if you're a marina hopper, when it comes to the charger, bigger is usually better, since battery acceptance will determine the output anyway. You could do a price comp between say a 40A and 60A and see if there's much difference.

 

[Ward H]

Excellent links by Dave and Stu.
When reading the links to the marinehowto.com website, you will note in the one on choosing a battery charger, the author talks about the difference between the 20 amp and 30 amp Sterling chargers. Mainly the beefier connections for the cables to the battery bank.
For that reason I'd suggest you go with the 30 amp charger. Then your covered if you decide to upgrade to two 6 volt true deep cycle batteries which will give you 230 amps total capacity. Your 75 amp batteries are probably group 24 batteries. The GC2 6 volt batteries will fit in the same foot print of a group 24. It will be a few inches taller.
If you have the built in dual battery compartment under the starboard bench seat, the GC2s will fit, even with the extra height.
Remember that FLA batteries should not be discharged more than 50% of their capacity. That means you currently have 75amps of working capacity. With the GC2s you get 115 amps working capacity.

And you may need new batteries after cooking them for a while.

 

[dlochner]

And you may need new batteries after cooking them for a while.

I'm not sure that is a "may need" question, I think it is a will need statement, there may be a little more life left in them, however, a new set of batteries is in your near future.

 

[gettinthere]

An alternate possibility is that some lead broke off one plate and joined that plate to an adjoining plate causing a runaway. I had that happen with one of my Trojan T-1275s. That battery was at 150d while the other batteries were at 90d. If you had boiling of all the batteries then probably the charging but if only one, then broken plate.