Battery for Start/Emergency House use

[Ward H]

This past season I used the OEM 1/All/2/Off battery switch and followed the practice of using my two GC2 6V house bank for house loads and starting. I used a 3 yr old Everstart MAXX-29DC battery strictly as a reserve battery. This battery has not been taken care of to ensure a long life so I may replace it this spring.

This winter I switched to a DCP switch for isolated house and start banks. Both banks have emergency off switches so I can easily isolate either bank, the use the combine position of the DCP to use either as a house and start battery.

The 220Ah GC2 bank is plenty for my day sailing and one or two nights out on anchor.

I've been reading a lot of threads on electrical systems and understand @Maine Sail 's comments that a deep cycle battery used as a starting battery should have a long life, batteries marked as starting or dual purpose are not the best for the purpose.
Then I recently read his thread about internal battery failures with most occurring in auto sized batteries such as G24, G27, G31 etc

This leads to my question for today.
What type of battery is best for use as a starting/energency backup house battery in the 100Ah range?
Pseudo deep cycle? True golf cart deep cycle? FLA? AGM?

I looked at one (Trojan T-2175?) but the costs was near $300. A bit over kill I think.

 

[dlochner]

This leads to my question for today.
What type of battery is best for use as a starting/energency backup house battery in the 100Ah range?
Pseudo deep cycle? True golf cart deep cycle? FLA? AGM?

Another question to ask, is the risk factor and how long will the battery have serve as a house battery?

If you are going offshore for a long time, then spend the money buy high quality batteries. If you are day sailing and coastal cruising, say never more than a few hours from a dock, then save some money and spend it on BoatUS Unlimited Towing.

 

[Ward H]

If you are day sailing and coastal cruising, say never more than a few hours from a dock, then save some money and spend it on BoatUS Unlimited Towing.

"If you are day sailing and coastal cruising"
That's what we're doing.

"spend it on BoatUS Unlimited Towing"
I bought it the week before we splashed our O'day 25 the first time. Used it the second week we were in the water. Auto renews every May 1.

I'm more curious than in need of a solution. Does he mean a $300-$400 AGM battery or a true golf cart type 12 volt battery or a pseudo deep cycle high quality $150 battery or is it really just dependent on risk?

The actual risk of us being stranded is really too low to be of real concern:
The house bank has to fail or I run it down below engine starting voltage (should take more than 3 days on the hook with our Ah usage) AND after having started the engine fine at the dock the starting battery fails about the same time as the house bank.

Thanks

 

[Stu Jackson]

comments that a deep cycle battery used as a starting battery should have a long life, batteries marked as starting or dual purpose are not the best for the purpose.
Then I recently read his thread about internal battery failures with most occurring in auto sized batteries such as G24, G27, G31 etc

Ward,

It's like information paralysis, isn't it?!?

Using deep cycle batteries for starting the engine usually means, to me from MS's contributions, that the deep cycle house bank can be used without harm to the battery to start the engine.

Then a simple automobile start bank is used in reserve.

This is the "now-standard" 1-2-B switch arrangement which you have mimicked with your switches, so switching isn't an issue. I leave mine on #1 house bank and use the reserve sometimes and keep checking it. I run the boat on 1.

Biggest deep cycle house bank & a cheap reserve bank as backup, reserve or start (always, like you). No need to spend $ deep cycle $ on a start bank. And if used sometimes for limited house loads, either it won't be for long or will be while the engine is running ('cuz you're motoring home to get new house batteries...).

That's the big picture logic.

 

[LeslieTroyer]

I'm old fashion - I like to have the house isolated from the start so I don't brown out or spike the electronics. So dedicated start and ability to start using the house. all should be the same chemistry (mine are not) so the ACR charges optimally all batteries. Look for CCA on the start and 20hr rate on the house.

Don't overthink it - it won't make as much difference as you might think.

 

[Ward H]

No need to spend $ deep cycle $ on a start bank. And if used sometimes for limited house loads, either it won't be for long or will be while the engine is running ('cuz you're motoring home to get new house batteries...).

This is true.

Don't overthink it - it won't make as much difference as you might think.

I know I am, I have a tendency to do so
and I know it won't.

 

[BigEasy]

Agree with Leslie, all batteries should be of same chemistry, so if you are using all gel or all AGM, there’s no cheap battery in the mix.

 

[TomY]

This leads to my question for today.
What type of battery is best for use as a starting/energency backup house battery in the 100Ah range?
Pseudo deep cycle? True golf cart deep cycle? FLA? AGM?

I looked at one (Trojan T-2175?) but the costs was near $300. A bit over kill I think.

I'm having great luck with a 'dual purpose' deep cycle/starting battery. I may have read they are not true deep cycle? At least 5 seasons old and still going strong and not showing signs of diminished storage. I've never been stranded with a dead starting battery on this boat in 20yrs of use.

This battery is isolated from the house bank except for charging through a dual output alternator(with sense wire on the house bank).

It gets a little more use than just starting. It also powers the anchor windlass. We often sail off anchor so this battery is discharged during retrieval without the engine running.

It's not a back-up for the house but is working great in this starting/windlass position(I think it's a Dura-last brand, from my local marine supply).

 

[Maine Sail]

A G24, 27, 31 DC is a slightly more robust version than a starting only G 24, 27, 31.. Any decent quality DC vesrsion, such as Crown, Trojan, US Battery, Deka etc. will work fine as a reserve for many, many years. We have a number of them out there used as starting or reserve banks that are in excess of 10 years old. The same battery, deep cycled, usually lasts considerably less than half as long.

The batteries that fail internally are almost always in house banks that are well beyond their prime and below 80% SOH..

 

[Ward H]

Tom, 5 years and still going is good to know.

A G24, 27, 31 DC is a slightly more robust version than a starting only G 24, 27, 31.. Any decent quality DC vesrsion, such as Crown, Trojan, US Battery, Deka etc. will work fine as a reserve for many, many years. We have a number of them out there used as starting or reserve banks that are in excess of 10 years old. The same battery, deep cycled, usually lasts considerably less than half as long.

The batteries that fail internally are almost always in house banks that are well beyond their prime and below 80% SOH..

I bolded what clarifies the comments I read in Maine's battery failure thread.

Thanks everyone.

 

[thinwater]

Just curious.

How many of you have ever had to use an emergency or reserve battery to start? I've never drawn my house bank that low, not on any boat I've owned. Not sayin' it can't happen, but unusual, I would think. Sailboat engines are small and don't take monstrous amps, not given the bank size you likely have.

I'd also be thinking about how I could bootstrap using solar or wind, probably isolating one battery. I would think a good size panel layout and a few hours on one battery should be enough to kick it over.

 

[FastOlson]

What works for one person may not be ideal for another... but I put in a spiral-cell AGM 12 volt battery for a reserve/emergency bank over a decade ago. It's still fine.

Our last 'emergency' need for it was a couple of years ago when our 9 year-old house bank suddenly became a 10.5 volt bank early one morning while we were weekend cruising. That house bank was a pair of Trojan T-145 golf cart batteries (flooded technology).
I replaced it with the same model GC batteries. Trojan T-145+

I 'test' the spare battery several times a year to start the 3-cylinder diesel and it always works without a problem. Given that the charging curve for the AGM is similar to our flooded batteries I just charge the AGM several times a season - shore power charger or from the engine alternator. It has very little self-discharge anyway. Actually, I would have used flooded technology for that spare battery, but the only good place to create a box for it was under the aft cabin berth; no way to add water to cells there.
"Everything's a Compromise" , as someone used to tell me. And in the end... "all solutions are temporary."

And if still in doubt, just follow Maine Sail's advice...

 

[dlochner]

Just curious.

How many of you have ever had to use an emergency or reserve battery to start? I've never drawn my house bank that low, not on any boat I've owned. Not sayin' it can't happen, but unusual, I would think. Sailboat engines are small and don't take monstrous amps, not given the bank size you likely have.

I'd also be thinking about how I could bootstrap using solar or wind, probably isolating one battery. I would think a good size panel layout and a few hours on one battery should be enough to kick it over.

A couple of times. The battery was old near its end of life and unknown to me the alternator was not charging it due to blown diodes. It was only the second or third season with the boat and I didn't have any way to monitor the SOH.

The next time was a delivery in a new-to-me boat. Sitting in the double lock at Lockport, NY, the engine wouldn't turn over, the boat tried to get sideways in the lock. (A boat with a 55 foot mast on deck can't turn around in a 45 foot wide lock.) Turns out the PO had rewired the boat in such a manner that it would have given @Maine Sail a heart condition and the start battery was not connected to any charging source and I couldn't figure out how to use the house batteries to start the boat. And it had the Yanmar intermittent start switch issue.

That was the first fun moment on the delivery.

 

[Hello Below]

Just curious.

How many of you have ever had to use an emergency or reserve battery to start?

Great question for the Monday Morning SBO Poll.

 

[LeslieTroyer]

I do have a low voltage disconnect switch on the fridge it will alarm if house bank gets low.

 

[TomY]

Great question for the Monday Morning SBO Poll.

Never but my present boat came with a pair of auto jumper cables. Simple way to connect to the house bank. But I took them off after a few years. It's a sailboat, afterall...

 

[thinwater]

Great question for the Monday Morning SBO Poll.

Seriously, I am just curious. Since all of my boats have had outboards (my last was a 34' cruising catamaran) it was never a serious concern. They were electric start, but you could wrap a line, which I practiced. Just the same, despite a good bit of cruising, I never had a battery drop that low. Yes, I've replaced batteries, but I guess I caught them before failure.

 

[Sailm8]

I carried an aux jumper/starter battery but it only lasted about 3 years when it would not take charge. Luckily, I didn't need them. I now just have jumper cables. My Yanmar starts almost instantly so long periods of cranking are not necessary.

 

[LeslieTroyer]

I cruised on a Pearson Ariel with a MD1 Diesel engine. It had a unique starter/generator that got it started and generated about 20A of power. All belt driven. Halfway thru the cruise above Nanimo the bracket for the starter generator broke. I started the motor using a hand crank and compression release. A task I would be hard pressed to do today. I’ve also started a TR3 I once owned when the starter broke. You can’t believe the looks I got when cranking it.

 

[Benny17441]

The best backup battery is that one that is just "good enough" for the anticipated emergency. Too much battery and you are wasting money. On many occasions I have used an automotive type battery pack as a backup in case of emergency.