Do I have a dedicated start battery?

[wingssail]

Originally Posted by Jammer

It is my experience that VSRs are flakey, and difficult to troubleshoot when they fail. YMMV.

While mine is a minority view, I believe that on a sailboat with a reasonable amount of solar, there is no reason to have a separate start battery. In that circumstance the only adverse consequence of a dead battery bank is that you might be late for work.


The concept of a separate "start battery" is a holdover from an era when electrical systems were less reliable and charging sources less diverse.

Sorry Jammer, there have been a few times when we needed the reserve power of our start battery to get the engine going. Using solar to recharge the battery will be pitifully slow (days, and sunny days at that). So for us we are glad to have a reserve (the start battery).

By The Way, Everything is difficult to trouble shoot. As our electrical systems become more complex we set ourselves up for down time of undetermined causes. It will only get worse. Every electrical device on the boat will eventually fail and we won't find it in the manual.

[GILow]

Follow the wire from the starter motor. There may well be a third battery hidden in some out of the way spot.

[Tetepare]

Originally Posted by smac999

or waking up at 4am to a draging anchor after 4 days of no sun. and the engine doesn't start. and you smash into the rocks.

Or you sail back to home port bashing into waves and tacking back and forth for eight hours, too bad with an engine could have done it in three.

A start battery isn’t old technology, it’s insurance.

I DID do this a couple decades ago, and killed the old batteries. Luckily I was able to get ashore and drag a battery a mile to the auto shop for a swap. Also lucky I had FLA. If I had to find LI I would have been SOL.

[JimsCAL]

The 2 equal batteries and a 1-2-Both-Off battery switch is typical of older boats. My 1985 Cal 33-2 came that way. Until you upgrade the system, the thing you need to watch is keeping both batteries charged. Without an ACR or something similar, it will require when running the engine to have the switch in Both and remembering to switch back to 1 or 2 when you shut then engine down. If you leave the switch in Both you risk running both batteries down.

[S/V Illusion]

Originally Posted by wingssail

S/V Illusion, this advice implies some sort of battery combiner, VSR, or other automatic device. While this is recommended by most electricians and preferred by many boaters, it is not a "must have" unless the OP wants it.

He, (and you) presumably still has a eyes, a brain and fingers to turn switches, so that level of automation is still optional.

Don’t know how you got from “check your charging circuit” to what you wrote.. it’s a simple suggestion to be applied universally

[DoubleD]

GILow, thanks for the suggestion of tracing from the starter. I've assumed there is not a third battery somewhere as the 110v battery charger is connected to the two Dynos. But you never know.



DD

[wingssail]

Originally Posted by S/V Illusion

Don’t know how you got from “check your charging circuit” to what you wrote.. it’s a simple suggestion to be applied universally

I was just responding to this: "whatever charger you have to ensure both batteries are charged properly regardless of the switch position" (emphasis mine).

"Must have" doesn't sound like a suggestion.

The OP is presumably a new boater. I just wanted to make it clear that "must have" is an opinion (and possibly a valid one) but not a requirement for all.

[flyingfin]

Originally Posted by smac999

or waking up at 4am to a draging anchor after 4 days of no sun. and the engine doesn't start. and you smash into the rocks.

True Dat!

[Happ]

Originally Posted by DoubleD

Jammer, I'm not sure if I tried to start the engine with switch off. I'll try that later today when at the boat.



Tetepare, Maybe my question should be, do I have a dedicated house battery? My concern is accidentally drawing down both batteries, such that I cannot start the engine.


thank you

Since the batteries are the same it doesn’t matter which is which. Pick one or two and call it the house. The other is your starter. Easy. It is better if your start battery is a proper starting battery built for that purpose though.

[GrowleyMonster]

Two batteries with an 1/BOTH/2/OFF switch is a tried and true configuration. Run house loads on one or the other, not both at once, and you know you can't run both batteries down at the same time. You should always have one that will start the engine.With FLA batteries I start the engine with the switch on BOTH and let them both charge as they will. If one battery is very low you should start on just the charged one, then switch to BOTH. You might well prefer to charge them one at a time. Talk to your electrician about this, and decide for yourself. Just don't let one go without charging. The reason that OFF is not between A and B, or 1 and 2, is so you don't momentarily run the alternator without a load and a sense voltage for the regulator. You might be surprised to know that disconnecting the batteries from a running engine's alternator will immediately toast the rectifier diodes. That's one vulnerability that nobody has figured out a practical and simple idiot proofing for, for some reason.

https://www.amazon.com/DROK-Percenta...s%2C122&sr=8-5

Something like the above display is cheap insurance against depleting the batteries while thinking you have plenty of charge left. These units need to be tested before you trust them. They do not eliminate the need to check the water and also the specific gravity on a regular basis, maybe weekly. There are better, more accurate, and more dependable battery monitors but I used one quite similar to that one on my 48V EP system on my electric boat.

Your FLA batteries will last a lot longer if you don't let them discharge below about 50%. A 40% charge level won't kill them any time soon. A 30% charge level is survivable but letting it go that low repeatedly can significantly shorten your battery life.

When sailing, your batteries get sloshed around a bit, and this helps to keep your electrolyte (the acid and water solution in the batteries) mixed up, helping to avoid stratification. It is still possible to get some plate sulfation, but overall, a good continuous jostle is good for the batts. If you ever spend a lot of time at a dock where the batteries don't get shook up, you should give them an equalizing charge once in a while, maybe monthly. This is a deliberate overcharge, resulting in significant outgassing and temperature increase, and must be done carefully, and monitored. Consult your local marine electrician. Almost ZERO "smart" chargers will do a proper equalizing charge. The voltage is too low and there is no temperature input, so the algorithm is incomplete. Get the straight dope from the maker of your batteries, for the specific numbers for the recommended equalizing cycle. As an example my 48V bank got a full bank manual equalizing charge of 64V. The open circuit resting voltage fully charged was 50.9 to 51 volts. If you isolate a FLA battery for about 12 hours and check the voltage, you get a pretty good idea of the charge level from the voltage. Without the rest, and without having all charge sources and loads disconnected, the voltage is not a good indicator of state of charge. My bank's maintenance or float charging voltage was 54V. My charger would sometimes automatically go into a "pseudo-equalizing" cycle if I turned it off and then back on, but would never reach true equalizing voltage, and timed out after one hour, as I recall. The way I equalized my batteries was with a 2kW Variac and the salvaged rectifier from an old welding machine. This requires VERY good ventilation and careful monitoring of current, voltage, and temperature.

BTW never top up the water on a discharged battery. Just cover the plates, charge, and then fill the charged battery. When charging, the battery "makes" water and you can overfill if you don't allow for that. The true electrolyte level is observed when the battery is fully charged.

Trojan has an excellent website with a lot of technical details and suggested charge parameters, and if you can't get the straight dope on your deep cycle FLA batteries, you won't go far wrong by using the data from Trojan.

Many batteries you will find in boats are not true deep cycle batteries. Many are "marine" batteries, designed as a compromise between a full deep cycle battery and a starting battery. DO NOT treat them as deep cycle, using Trojan's parameters for equalizing! Contact the manufacturer. Also do not EVER let that type of battery get down to 30% SOC!!! Probably the best reasonably priced true deep cycle batteries are GC-2 size golf cart batteries, and that is what I used in my electric boat. I love the form factor and for the price, they are very rugged, long lived, and dependable. You can get them for around $90/each if you shop around. (HINT: Don't forget to check Sams Club!)

I hope you have a good hydrometer, and you check and record your specific gravity. This is almost as important as checking the electrolyte level of the cells.

It would be a good idea to hand over hand follow your wiring and make a diagram of your entire battery, starter, charging, and switchboard feed system, including any loads connected directly to the batteries. Understand your system so you don't ever make a disastrous modification, and so you can better troubleshoot your system.

It is a really good idea to install a solar panel or three. Running your diesel for bulk charging cycle isn't so bad, but topping off with the diesel, unless you also need it for motoring, is grossly inefficient. With solar charging, you can top up the batteries and keep a float charge on them any time you have sunshine on the panels, with no concerns about engine wear or low load prolonged operation, or fuel efficiency. Wasted power from solar is not really a big deal. You can use the extra juice for heating hot water, or making water. Do your homework before installing and hooking up stuff.

[MVDarlin]

Normally #1 is the house bsnk and #2 is the start battery. Given your reported low electrolyte levels I recommend you disconnect and test each battery with a load bank tester. This is the only sure way to find a bad battety. Voltage checks alone may not reveal a bad battery. Also, consider replacing all with AGM sealed batteries to avoid acid spills. This is a special concern in sailbosts that heel at sharp angels. If you need to replace one battery it is recommended that all are replaced at the same time. Do not mix battery types and get deep cycle batts. And yes keep them segregated and turn the batt switch to #1 when you shut down the engine.. Nothing more disturbing than to wake and find you can't start your engine at some remote anchorage because you left your inverter on overnight. Remember to switch to all when the engine is started.

[GrowleyMonster]

Originally Posted by MVDarlin

Normally #1 is the house bsnk and #2 is the start battery. Given your reported low electrolyte levels I recommend you disconnect and test each battery with a load bank tester. This is the only sure way to find a bad battety. Voltage checks alone may not reveal a bad battery. Also, consider replacing all with AGM sealed batteries to avoid acid spills. This is a special concern in sailbosts that heel at sharp angels. If you need to replace one battery it is recommended that all are replaced at the same time. Do not mix battery types and get deep cycle batts. And yes keep them segregated and turn the batt switch to #1 when you shut down the engine.. Nothing more disturbing than to wake and find you can't start your engine at some remote anchorage because you left your inverter on overnight. Remember to switch to all when the engine is started.

That is right, voltage doesn't tell you when a battery is losing capacity necessarily, only the state of charge. A load test is required to reliably detect loss of capacity. With well maintained batteries less than a couple years old, loss of capacity should not be an issue, though. Still it is good to have a load tester and also know how to do a manual full discharge load test, which should be done annually after about the 5 year mark. Resting voltage IS a very good indicator of state of charge, though, and with a digital voltmeter or battery monitor this is dead simple to do, and more accurate than s.g. due to possible stratification.

Replacing the entire bank at once is also highly recommended, but check the date on the batteries, and also try to get batteries from the same month. The ones on the shelf right next to each other could have a half year difference in date of manufacture.

Personally, I dislike AGM or other closed cycle batteries in place of proper FLA batteries because they cannot be maintained properly. They do have their uses, but I wouldn't use them as a main bank on a sailboat. I know that they have their fans, and for someone who is too lazy or technically challenged to monitor and maintain FLA batts anyway, AGM would be superior. When there is no practical means of installing them on a secure and level foundation or in a proper battery box, AGM is better. On a motorboat, which often has a VERY violent motion, AGM might well be better. I have never had problems with electrolyte sloshing out of my FLA batteries. Of course I have never had a flat knockdown or a rollover either. I have to admit I am too much of a fairweather sailor to ever see much of that.

If batteries are lined up so that the long axis of the cells is parallel to the centerline of the boat, there should be no problem with electrolyte sloshing out or uncovering plates. With most batteries, that means that a monoblock 12V battery should be installed crossways to the keel. Remember, electrolyte does not travel across the battery between cells. A lot of guys get this wrong.

[Ballsnall]

Originally Posted by MVDarlin

Normally #1 is the house bsnk and #2 is the start battery.

With a basic setup like this I prefer to think of it as you have 2 start batteries for redundancy as the house loads are run off of either start battery.

As has been posted you switch to position 1 or 2 or even Both if both batteries as charged and start the engine then switch to Both with the engine running to change both batteries. When you stop the engine you must switch to 1 or 2 but never Both as your house supply then switch to the opposite battery to restart your engine then back to Both once it's running.

With the advent of cheap lithium jump starter packs, you could comfortably rewire this system to a single bank and just keep a jump starter onboard for emergency use.

[wingssail]

Originally Posted by Ballsnall

With a basic setup like this I prefer to think of it as you have 2 start batteries for redundancy as the house loads are run off of either start battery.

As has been posted you switch to position 1 or 2 or even Both if both batteries as charged and start the engine then switch to Both with the engine running to change both batteries. When you stop the engine you must switch to 1 or 2 but never Both as your house supply then switch to the opposite battery to restart your engine then back to Both once it's running.

With the advent of cheap lithium jump starter packs, you could comfortably rewire this system to a single bank and just keep a jump starter onboard for emergency use.

No, not a good plan. If you switch to "both" then plan to switch back to "1", sooner or later you will find you have run down both batteries because you forgot to switch back. This is why people have battery combiners, and the such.

Me? I have such a system as yours except my battery "1" is much bigger than my battery "2". And I never switch to Battery "2" or "Both" unless my engine does not start on Battery "1". Then I switch to "2" (not "both"), start the engine, let it charge "2" for a bit, then switch back to Battery "1" and let it recharge Battery "1".

So I stay off of Battery "2" almost all the time. About once a week I check if the boat will start on Bat "2". If it doesn't. I charge up Batt "2".

This is why people buy combiners and VSR's and other devices to make up for their lack or memory.

[Ballsnall]

Originally Posted by wingssail

No, not a good plan.

I agree it is not ideal, just trying to explain to the op how a basic single charge source dual battery setup was designed to operate. If he wants to upgrade then I'm sure there are better options depending on his requirements.