Starter battery VS. Reserve Battery

[roland stockham]

There are good reasons for NOT doing this!
There are 2 fundimentally different designs for lead acid batteries that meke them suitable for different applications. A start battery has a large number of thin plates giving a large surface area exposed to the electrolite. This means it can supply lots of current for a short period. Capacity is normally rated in cranking amps not amp hour (although normally it will have a stated reserve capacity) even a small start battery of say 85a/hr will have a cranking capacity of around 450a, more than enough to start the engine. The down side is that those thin plates distort easily and if discharged to much tend to shed plate material so if heavely discharge it will gove a very short cycle life, generally only 150-200.
A deep cycle battery is the opposite it has a smaller number of thicker stronger plates and ideally designs like pockets or aditional alloys wich reduce shedding. This makes it very robust but it's reletivly low surfece area limits it ability to suppy high currents. when cycled between 100% and 60% SoC it should have a service life in thousands of cycles. To get the same cranking amps you had from the 85a/hr start battery you would probably need about 400a/hr in a deep cycle battery and still risk some damage and poor starting due to internal heat build up.
So yes a house bank will crank the engine in an emergency and a start battery has some reserve you could draw on in an emergency but they are not designed to be interchangable.
There is something that attempts a compramise between the two. Caravan/trailer batteries sometimes sold as marine dual purpose batterirs are in fact a heavy duty start battery. They still have quite a large plate area so have a cranking rating but the plates are heavy enough to give better cycle pergormance. Usually up to 100/1500. Like most compramises they are less good at both jobs. To get the same cranking performace the battery will be significantly heavier and more expensive than a propper start battery but will come knowhere near the cycle performace of a true deep cycle battery. it will also have a lower water reserve and be more easily damages by poor charging or over discharge. For a cruising boat ther are the work of all worlds. For a motor boat or small weekend sailor they can be fine. They are designed for motor homes or trailers wher they work fine as they get low cycle use and lots of charge time and can give a reasonable reserve for occasions when the vehicle is not running or plugged in.
So the ideal system for a boat is a small dedicated start battery plus a larger deep cycle house bank. The house bank for a cruiser shoul provide enough powerto finish a 24hr day at 80% SoC giving 2 days between charging. This should give many years of life. The caring system should be rated at about 20a per 100a/hr capacity which will recharge to 95%SoC in 4hrs and be given a longer charge fairly regularly to ensure 100% charge (min once a month)
Proper deep cyle batteries are either 6v or 2v and VERY heavy, if it is light weight and 12v it is not deep cycle whaterver the lable says!

[Jim Cate]

Originally Posted by ontherocks83

Motive T105-AGM | Trojan Battery Company

These are the T-105 agm's

I stand corrected... wasn't aware of these. Good luck with them.

Jim

[Tillsbury]

Originally Posted by Gary Mc

Hi my 2GM only takes 2-3 seconds to start. I would suggest that yours could use some attention. When mine got a little slow starting I had the injectors overhauled and it was right back to almost instant starting, even on cold weather.
Good Luck

This. Fix the engine rather than patch the problem with batteries. I'd say even 2-3 seconds was a very long time. All the diesels I've had have started instantly - before the key has made it all the way to the stop. You shouldn't hear cranking. Then you won't be as worried about the batteries.

[rom]

Originally Posted by Paul L

A simple, time proven system used by thousands of coastal and long distance boats. Why spend the extra money and time on a complex solution? What real problem would it be solving? There are plenty of other things on a boat to suck up your time and money.

House+reserve actually makes for a much simplier design. It may not work for everyone though. It works for me because I live on the boat, I like to manually check/test my batteries, I have a rather large house bank.

[Paul L]

Originally Posted by rom

House+reserve actually makes for a much simplier design. It may not work for everyone though. It works for me because I live on the boat, I like to manually check/test my batteries, I have a rather large house bank.

Might be, but I don't see how it has less components, wires or switches than the average house bank and starter battery setup. If you look on the previous posts in this thread you can see the suggestions on how to massively complicate things with low volt cutoffs, etc.

I cruise full time on our boat too. The house bank gets monitored as I watch it recharge during the day. Starter battery gets 'monitored' when I start the diesel.

[Maine Sail]

About the only time a "house + reserve" system would be used is on a boat that already has an existing 1/2/B switch. If that is the case, and it's not worthwhile to do a switch re-configuration, then it can work. Just be sure you check/test the reserve bank occasionally to ensure it is operational when or if you need it.

1/2/B Switch Thoughts & Musings (LINK)








.

[Q Xopa]

Originally Posted by john61ct

http://www.cruisersforum.com/forums/....php?p=2982422

From "Variation" onwards

Ok, yes clever concept.

I see from your links that you frequent many forums.

Have you actually seen this set up in action?

I can see what the concept is and trying to achieve. Larger capacity so less Pherkert effect at higher SOCs. Then an auto disconnect of your the seperate sub banks.

However Im not sure I can see what is actually being gained here.

Firstly as you said it is extra complexity.

Phukert effect, is generally for Lead batteries not so much for LFP.

Also, depending on the duration of the load that is dragging the bank/s down. For a short duration load it should work well.

However for a longer duration load this will make the situation worse. Ie dropping the 'sub bank' off line will leave the existing connected bank as a lower capacity and it will make the situation worse drawing down that bank faster.

Aircraft do something similar, 'Load shedding' with seperate busses, usually termed 'essential' and 'non essential' busses. The theory is in an emergency, usually a generator dropping offline, the bus tie opens dropping the non essential bus offline.

Of course a bunch of lights also come on to let the pilot know that now might be a good time to start turning things off, that he can do without, to prolong his battery remaining time.

So in the above aircraft way of doing things- it senses a supply shortfall and automatically cuts the useage rate. Also notifying the operator they may want to consider making further cuts to the usage rate.

But in your suggestion the system will automatically sense and reduce the supply. But if the load useage remains the same, ie not manually managed it could be a worse scenerio dropping the Main SOC faster.

I cant really see what you have gained over a Start/ House setup with you suggested arrangement.

Its always interesting to hear how others are handling these issues. There are certainly some clever people out there.

Like most of this it comes down to how we individually want to manage our Power.

[daletournier]

Originally Posted by Maine Sail

About the only time a "house + reserve" system would be used is on a boat that already has an existing 1/2/B switch. If that is the case, and it's not worthwhile to do a switch re-configuration, then it can work. Just be sure you check/test the reserve bank occasionally to ensure it is operational when or if you need it.

1/2/B Switch Thoughts & Musings (LINK)








.

I have a 675ah house bank and 225ah reserve all T105's, the boat came that way.

Right or wrong I have them combined most of the time giving me one large 900ah bank.

My reasoning is I dont want lead just sitting there "just in case", seems a waste to me, also theoretically I should get a longer life out of my larger bank.

My redundancy is in the form of a Lifpo jump pack, and a generator. Both can get the engine going in the event of a battery failure.

When offshore I do separate the 2 and keep the smaller bank in reserve, but normal cruising they are combined.

We have stuff like the jump start battery, honda gensets,solar panels etc that we never had in the past, this gives us options.

[ontherocks83]

Originally Posted by john61ct

Trojan's AGM are not that great for deep cycling usage.

Better off with Lifeline, Odyssey or Northstar.

And your empirical data of this is from...............?

[Pete7]

Originally Posted by john61ct

Trojan's AGM are not that great for deep cycling usage.

Better off with Lifeline, Odyssey or Northstar.

What evidence do you have to support this statement please.

Pete

[Maine Sail]

Originally Posted by john61ct

Trojan's AGM are not that great for deep cycling usage.

Better off with Lifeline, Odyssey or Northstar.

And you know this as a fact? Considering Trojan's current Reliant AGM's are relatively new (brand new AGM factory finished only 2.5 years ago or so) I'd love to see the data behind this absolute statement.

[ontherocks83]

Originally Posted by Maine Sail

About the only time a "house + reserve" system would be used is on a boat that already has an existing 1/2/B switch. If that is the case, and it's not worthwhile to do a switch re-configuration, then it can work. Just be sure you check/test the reserve bank occasionally to ensure it is operational when or if you need it.

1/2/B Switch Thoughts & Musings (LINK)






.

That's a great write up. Thank you!!! I do have an existing 1/2/both/off switch and was planning on doing almost exactly what you described for a set up. The big thing you described that I did not think of was having the alt wired directly to the house bank with a charge bus and isolation switch.

I'm not quite sure how that would look though, would you happen to have a drawing or description as to how it is set up? I think the confusing part for me is if the house bank shorts out and you isolate it, how is the reserve bank then connected to the alternator?

On Edit: Ooops sorry I found the diagram at the very bottom of your write up. I missed it the first time. Thank you again!

[a64pilot]

I have two banks a 220 AH and a 440 Ah bank, I gang them together as one with the 1,2, B switch set always to B. I don’t echo charge or anything fancy.
I do not believe a “starter” battery is required to start my little 40HP Diesel, 660 AH of deep cycle bank can easily do it, with no problem.

When I eventually lose a battery I can isolate to one bank by merely changing the switch until I can reconfigure. If somehow I didn’t pay attention to what is going on and kill the bank to where I can’t start the engine I’ll either just wait until Solar can charge it up or crank the Honda and charge it that way.

A battery bank is a source of power, that all, quite like a fuel tank. I don’t see the need for multiple fuel tanks because I can’t manage fuel level and don’t see the need for these multiple banks myself.

Finally, you don’t see low voltage cut off’s for a lead acid bank because one won’t work, the reason one won’t work is because the voltage sag under load is too high, if you had a low volt cut off, every time you went to start the engine in the morning with a discharged bank, it would cut out, or any other large load like a windlass, or an inverter etc.

However should you desire alerted to a low voltage condition, there are other ways, the ammeter in the picture for instance has alarm set points for both high and low voltage, my low volt alarm limit is set at 12V, it’s adjustable of course so you can set it wherever you want to.

[daletournier]

Originally Posted by a64pilot

I have two banks a 220 AH and a 440 Ah bank, I gang them together as one with the 1,2, B switch set always to B. I don’t echo charge or anything fancy.
I do not believe a “starter” battery is required to start my little 40HP Diesel, 660 AH of deep cycle bank can easily do it, with no problem.

When I eventually lose a battery I can isolate to one bank by merely changing the switch until I can reconfigure. If somehow I didn’t pay attention to what is going on and kill the bank to where I can’t start the engine I’ll either just wait until Solar can charge it up or crank the Honda and charge it that way.

A battery bank is a source of power, that all, quite like a fuel tank. I don’t see the need for multiple fuel tanks because I can’t manage fuel level and don’t see the need for these multiple banks myself.

Finally, you don’t see low voltage cut off’s for a lead acid bank because one won’t work, the reason one won’t work is because the voltage sag under load is too high, if you had a low volt cut off, every time you went to start the engine in the morning with a discharged bank, it would cut out, or any other large load like a windlass, or an inverter etc.

However should you desire alerted to a low voltage condition, there are other ways, the ammeter in the picture for instance has alarm set points for both high and low voltage, my low volt alarm limit is set at 12V, it’s adjustable of course so you can set it wherever you want to.
Attachment 200473

Exactly what I do for the same reasons.

[Group9]

Originally Posted by Dockhead

You say "of course", but in a lifetime of cruising I've never in my life seen a lead-acid bank on a cruising boat with low voltage cutoffs, which is a concept developed in connection with lithium batteries.

We have a Xantrex controller on our boat that has a voltage cut-off (we have AGMs) and FLA battery for our generator (and is charged separately from the house bank with it's own dedicated charger). But, it also has settings for FLA's (but, not Lithiums, which one of the reason we probably won't ever go there, because I don't want to have replace the whole system, which we are pretty happy with at present).

Not only can you set it to cut off the battery bank at any particular voltage, it also has a setting and is wired to fire the generator off at any particular voltage (although we leave this feature in the "off" position, because I just don't like the idea of my generator cranking itself up without any input from me).

Plus, we have 540 watts of solar. So, I know our batteries can be recharged, even if our generator breaks down, and the Xantrex controller malfunctions.