Boiled starter battery

[TorMar]

Our Ericson 34 has two house batteries and a separate isolated starter battery. The starter battery is relatively new -3yrs old top of the line 27 series - and she would not start the diesel last week unless plugged in to shore power. She showed 12.32 volts, terminals were clean, cables were clean, but no oomph. When I looked inside the battery, the electrolyte was darn near all gone. Yikes, how can this happen?

The electrical specialist at the marina suggested the following scenario - and it made a lot of sense. I would sure appreciate some thoughts on how accurate this is.

When cruising, we tend to really draw down the house batteries, nav gear, laptop, VHF, fridge for a couple of hours each day, cabin lights, and when cold outside, good old Mr. Espar, and finally the anchor windlass. While at anchor we charge the batteries by running the diesel for 30 minutes twice a day. She has a 50 amp alternator. If at a Marina, we plug into shore powere and the charger takes over. It is the charging that boils off the electrolyte in the starter battery. The house batteries are seriously depleted and the alternator sends full 50 amp charge to them - yet the starter battery is probably still fully charged, but getting massive charging from the alternator, or the shore power charger. I was told that while the house batteries are charging, the starter battery is merrily boiling away electrolyte.

If that is indeed the case, we need to change our wiring and put some safeguards in place. Can anyone make suggestions?

Thanks in advance.

Tor

 

[stbdtack]

If your starter battery is tied into the house batteries when charging then the voltage will only be as high as the house batteries. That amperage from the alternator will flow where its needed most to bring the voltage up. If your Starter battery is full then most of the amperage will flow to the house batteries. Do you have an isolator, charging relay or manual switch?
Are you checking the levels on a regular basis? Lead acid batteries with a proper charging system should need water about every 6 months. How often have you added water over the past 3 years?
Lots of variables......

 

[Chris Miller]

Made the same mistake...

Hi Tor,
We made the same mistake with our lead acid deep cycles-
I'm going to sound scary dumb here- but the last time I had to add water to a battery was in my '68 ford pickup, so I kind of felt like deep cycle technology was in the jurassic period here-- So I discovered our group 27's with very low levels (they were having a lot of the same lack of power issues). I topped them up and things have been MUCH better. I think I probably took some life off of them in my ignorance, but they are working pretty well for now. We just keep a gallon of distilled water on board and use a (new) turkey baster. Depending on how often you go out, check them monthly and just top them up.
FWIW, I replaced our start battery this year with a "maintenance free" battery that supposedly requires no water addition, just to be on the safe side.
I'm sure some of the more knowledgable electrical guys will chime in here, but the turkey baster method is working pretty good for now. I'm looking into a duo-charge and smart regulator type system when I upgrade the charging system in the future to help with some of the overcharging stuff. Although those come with their own set of issues...
Chris

 

[NateHanson]

Ben's right that the amperage will mostly flow to the depleted house batteries, but the charging voltage will still be too high for the full starting battery and you'll boil it. I think you need a two-channel charging system. The two banks should be separately regulated since their usage is very different. That's my simple understanding.

Nate

 

[Tom Metzger]

Start batteries

Start batteries get very little use. For our diesel engines, typically, less than a quarter amp hour per cold start, assuming 80 amps to start plus 15 sec on the glow plugs. That means that you have hundreds of starts on a charge. There is no need to charge the start battery on a daily basis while away from the dock shore power. Nor is there any reason to have a battery larger than a group 24.

I have always recommended not charging the start battery from the alternator while charging the house bank. The first reason is it slows the house bank charging, and the second is that it cooks out the water. I keep my Off-1-Both-2 battery switch in the house bank position 24/7. Like most of us, I am rarely away from the dock more than a week at a time, and that is barely enough to require recharging the start battery.

Most of us don't bother to switch to the starting battery to start. It is there for emergency use only. Since I don't use it, I don't charge it while away from the dock and shore power. You do have to test the start battery periodically when it has been off of the charger for a few days or several hours, or what ever is a long period for your usage.

This discussion applies to why I don't recommend battery isolators, combiners, echo chargers, etc. You tend to overcharge the start battery and to slow the intended charging. It also explains why you don't need a monitor for the start battery. You don't discharge it.

Obviously, if you are on a mooring or you don't have a dedicated start battery this doesn't apply to you.

 

[u079721]

Let me second Tom's comments on batteries here. I too had a dedicated starter battery that I kept in reserve, while I used the house bank to both start the engine and run everything else. At the dock my two-bank charger did a great job of keeping everything healthy, but I wondered about what to do during a month long cruise.

So early on I installed a battery combiner. Then I noticed the same problem mentioned above - that after long periods of charging (during 28 hour motor sailing deliveries) the charging battery would lose water faster than the house bank. So I dissconnected the battery combiner for the deliveries to avoid that problem. I then checked on the status of the engine starter battery, and found that for a month long cruise, in which it was never used, it never needed charging. So the combiner turned out to be a waste of money. It was easier to just switch the battery switch to ALL for one day's charging every few weeks if needed then it was to remember to attach and then dissconnect the battery combiner.

Perhaps someone who has been out crusing long term can comment on the best way to keep a starter motor topped off, but I found the combiner to be over kill.

 

[Geoff Johnson]

I have an Optima blue top AGM starting battery that is isolated by a mechanical switch. Since I start the engine from the house batteries and because, as an AGM, it almost does not self-discharge, I basically just forget about it.

 

[Shadowfax]

I agree with all the above. I leave the battery switch on House all the time. The starting battery is for back up only. I'd also invest in a good quality "smart" charger, which should pretty much take care of boiling off the battery

 

[TorMar]

Thank you all for advice and sharing

Thank you for the advice and voices of experience. I'm leaning to the simple solution which appears to be taking the starter battery off the charging circuits, probably by adding a simple heavy duty cut out switch. That way the battery is protected from overcharging and when it does deplete, throwing the switch will see it charged.
I have to fess up though that I have not been thorough in checking the electrolyte level in the starter battery. I assumed that because it was so rarely used, it would rarely be charged, thus needing little care beyond checking cables and terminals. It just illustrates again how wrong we can be when we make assumptions about things we don't know a lot lot about.

 

[Chris A.]

More battery resources

Hi Tor,

This resource was recommended elsewhere on this site and I found the workshops very instructive!

Jack Rabbit Workshops

Also, Nigel Calder's book, Boatowner's Mechanical and Electrical Manual, has a detailed (almost too much so!) explanation of the battery issues on a cruising sailboat.

Cheers,

 

[rssailor]

Balmar duo charge

If you really wanted a trick system, install a Balmar Digital Duo charge and this will take care of your charging issues with the engine battery. Are you running a system with just a one two both switch? If so Just designate one as house and two as engine and just always start in two and run the boat in one.
Even better would be to just have two on/off switches with one for house and the other for engine. You could use another key type battery switch for your emergency engine start from the house bank. Ryan

 

[Brisdon]

The power that's going to your starter battery is being determined by what the regulator senses the condition of your house bank to be. So, yeah, you're cooking it. I have a Balmar Duo Charge and it works great. It senses when a charge is going into the house bank and then sips from that for the float needs of the starter battery. The added advantage of this device is that you can now remove the isolating diodes that are pulling down your voltage because the charger and alternator will now go straight to the house bank. It's a great way to go.