This is UNBELIEVABLE!

[KyleR]

Okay, just started going through our electrical system yesterday to better understand how things are wired up and doing some general cleaning/maintenance in the process. I COULD NOT BELIEVE WHAT I FOUND!!

And FYI - these batteries were installed in 2020 - by supposed "professionals".

First, and the least of the problems - the "house" deep-cycle batteries are the type you need to check the electrolyte on and has the removable caps. Unfortunately, the caps are under a big sticker that says "REMOVE THIS LABEL AFTER THE BATTERIES ARE PLACED IN SERVICE TO MONITOR ELECTROLYTE LEVEL". The label was still firmly affixed and had obviously never been removed. So I pulled the label on both batteries and fortunately all plates were still fully covered but the level was just barely over the top of the plates. Not sure how full it should be but obviously they had never been checked or maintained.

Second - and more dangerous - the house batteries and the starting batteries were installed BACKWARDS!! There are two 1000CCA starting batteries, two 800MCA deep-cycle batteries and one generator starting battery. The deep-cycle batteries were connected to the main engines - one per engine. Okay - not terrible, but not ideal. However, the two 1000CCA starting batteries were wired in parallel and connected to the house loads! Everything I have ever read/watched warns about the dangers of using starting batteries as a deep-cycle house batteries. And I think I have watched just about every youtube video Jeff Cote from Pacific Yacht Systems has put out!

So today I am working through all of this and correcting everything. The boat has pretty much been a "marina boat" and never seen much time away from shore power so I am guessing that has something to do with why the batteries are holding up as good as they have.

Anyway, just wanted to share my latest saga and hopefully encourage others to verify your systems - especially if you didn't do the work yourself!

[km1125]

It's not at all "dangerous" to have starting batteries wired in parallel, nor is it "dangerous" to use them as a house supply. If they're frequently deeply discharged, as house batteries sometimes can be, then their longevity would be compromised but that's more of an economical issue than a safety one.

Good find on the electrolyte levels though. Surprised how many folks don't maintain the flooded batteries properly, which is probably why a lot fail earlier than they should.

[KyleR]

It's not at all "dangerous" to have starting batteries wired in parallel, nor is it "dangerous" to use them as a house supply.

Thanks for the reply. Wired in parallel wasn't my concern - it was the starting battery being used as a deep-cycle battery that was my concern. That arrangement seems to be a big no-no among the electrical world due to people who frequently discharge them much deeper than they should. For those "on-top" of their maintenance and routines, probably not an issue. For others who just "use it until it dies" - probably not the safest way to use a cranking battery (nor the most economical). Thanks again!

[g36]

Like mentioned it's not dangerous and as you stated it was dock queen so yes the previous owner would have found out his batteries were discharged quicker and probably wouldn't have lasted very long if he had anchored out much with the arrangement . Best rule to make lead acid batteries last is to try and only discharge 1/2 their capacity for longevity. If treated well they can last many years.

[Viper]

Ya using them that way isn't dangerous, they just won't last as long. Where are you located, does she get winterized every year? By the marina staff?

[KyleR]

Ya using them that way isn't dangerous, they just won't last as long.

Here's just one of many videos by Pacific Yacht Systems about using cranking batteries as deep-cycle. Sounds pretty bad to me - but I'm not an electrician by trade. The info starts at the 1:50 mark:

Many other videos I could link to but they're easy enough to find if you want to look.

Where are you located, does she get winterized every year? By the marina staff?

Yes, she was winterized each year by the previous owner and I have receipts for all 9 years of it being performed. And it looks like the winterization was done my the marina staff. We plan on heading south soon though and hopefully will never need another winterization! The boat is in Wildwood, NJ.

[Viper]

I wouldn't be surprised if the cables simply got hooked up wrong in the Spring after a Fall disconnect for the winter.

[Viper]

I get what he's saying about the potential for a catastrophe but that's in all cases of the wrong type of battery being used for the wrong purpose, and you can still have that type of catastrophic failure using the correct battery type if you allow fluids to drop too low where there is a shorted cell. So the danger isn't as much about the wrong type as it is about proper monitoring and maintenance. But ya, you should always use the correct type of battery designed for a specific load if you want your batteries to last as long as they were intended to.

[bud37]

Ya, a touch overly dramatic in my opinion. It would have been nice had he explained how to properly maintain your battery bank regularly to keep that very specific event from happening in the first place instead of focusing on it happening just because it was the wrong battery type, I mean how many boats are using the wrong battery types as we speak here, my guess more than a couple...

[Phrancus]

Terrible material that does not explain anything clearly, just lost of effects and drama on consequences of not knowing what's going on. Not a good thing on a boat where you might find yourself far away from others and need to get creative. Better to know a bit about where trouble can come from.

If you don't understand the underlying technology, you might think that the whole boat is in danger due to exploding batteries immediately after you turn on a lightbulb powered from a starter battery. Ridiculous and no point in making this kind of material.

What the simple basics are in my opinion:

starter batteries are made to produce a short kick of power to start an engine.
Lot's of amperage in a very short time. (how much a battery can do this is written on it: CCA (cold cranking amperage) with a value. High value: lots of power in a short burst.
This is the only thing to measure if you want to know if a battery in your car is still good (enough for coming winter). The other value (A) shows how much electricity it has inside it to draw that power for that short kick from. Bigger = more often.

A characteristic of a starter battery is that it is built in a way that it can deliver that kick but that way also has a drawback: it damages when the battery gets too low in power contained. Rule of thumb: 50% from what A is written on it, is what you can take out. And here is the underlying issue: if you do go lower than that: it gets damaged and when doing so it can start to boil when charging which means it is producing heat and gas. That gas is explosive and the damage causes a short circuit sooner or later and that is the dramatic finish of it all.

So can you use a starter battery for your house load? Yes you can. In fact, that popular guy in the video does mention that softly. Continuously you cannot because you will get under that 50% very quickly and you have few means to keep an eye on that to react quick enough. For a short time, small power needs you can choose to do so. But remember: a simple light in the trunk drains your car battery overnight so you don't have that much power in stock to draw from. Add up all your power drawing stuff (a good idea to do by the way, understand your boat) and you can figure out how much power you need to stock up. Lots of websites to help you with that.

A house battery with the same content (A) cannot produce the kick in power as mentioned above. But it can deliver that power for a longer time. It is built to not short out or get damaged when drained far (don't remember the figure but 10 or 20%) and the more modern ones have a monitoring display on it. Same physical volume, more power to take out and when it's empty, no damage.

sidenote: if your starter battery is emtpy but your house battery is not, preferably you would charge the starter one from the house one and then start rather than trying to pull a lot of power from the house battery. I wouldn't be so fussy when my engines are warm and only need a short crank but when cold I'd rather not. Charging from battery tot (empty) battery is not a great thing to do though; very high amperages flowing and if that empty one is empty due to an internal problem you're causing more harm than solving anything.

Next comes the more modern batteries that have completely different technology and characteristics. Much more power in smaller volume, great for sailing boats. Also more complex and costly.

The rest of it all is marketing and such: faster charging, controllers built in/on, monitoring, and a lot of speak using many cool materials that promise much greaterness over other brands.

Bottom line: draining a starter battery over 50% causes damage and becomes dangerous. Use a house battery to avoid that from happening.