Confusing battery replacement

[Jeff F]

- I drew in an inverter with wiring but have no faith in it working as shown because I'm pretty sure I'll get feedback from the alternators working against each other. This is my main problem to solve.

Yeah, you still haven't addressed how to charge a single house bank from two sides. You're showing 2 independent 200ah house banks. Far better to have one 400ah. That's the challenge I was trying to address in earlier comments.

I chose to go with ML-ACR's to have each alternator charge a start and house battery and they allow me to parallel the start and house in the event of a low start battery.

Low start battery events are exceedingly rare in a properly designed system. It's not something you need a hardware solution for IMO.

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[SteveK]

OK, I've made a little progress.
- I've decided to go all AGM's with group 31's (925 CCA) for starting and Renogy 8D's (200 AH) for house for a total of about $1400. You only have to manhandle them once.
- I've shown the alternator connected to the house side as they will be the most depleted in the AM after a night at anchor as suggested by Rod Collins.
- I chose to go with ML-ACR's to have each alternator charge a start and house battery and they allow me to parallel the start and house in the event of a low start battery.
- I want to place a start and house battery on each side on the boat to better distribute the weight (200 lbs per side).
- The always on is for sump pumps, lights, etc.
- I haven't shown any fuses but will install them.
- I drew in an inverter with wiring but have no faith in it working as shown because I'm pretty sure I'll get feedback from the alternators working against each other. This is my main problem to solve.

I'm at about $2700 thus far plus a lot of labor.

Anyhow I hope the sketch helps to explain my thinking.
BTW- I downloaded and read everything pertinent by Rod Collins.

Your drawing. The two ACR have one input, one output. I am confused as to what purpose that serves to run through them. I thought ACR fed two battery banks as needed.

 

[NWpilot]

SteveK

Alternator output is directed to the house bank and the ML-ACR will allow some of the charge to go to the start battery.

 

[NWpilot]

Yeah, you still haven't addressed how to charge a single house bank from two sides. You're showing 2 independent 200ah house banks. Far better to have one 400ah. That's the challenge I was trying to address in earlier comments.

Low start battery events are exceedingly rare in a properly designed system. It's not something you need a hardware solution for IMO.

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Jeff, you're right. I thought I'd come across the answer with the ML-ACR's but when trying to combine the two 200 amp banks for the inverter it became a problem.

I took a look at the Victron site and will spend some time getting to know about dc to dc chargers, eg. isolated vs non-isolated. The unit descriptions read the same.

You said you were using the Victron units. Which ones are you using?

I'm basically hooked on the technical stuff. I study a unit until I understand how it works and then I can apply it. The sites seem to assume a basic knowledge of their customers which I don't have.

Chas

 

[Jeff F]

I'm basically hooked on the technical stuff. I study a unit until I understand how it works and then I can apply it. The sites seem to assume a basic knowledge of their customers which I don't have.

Yeah, it's tough wading through. You might look at some schematics. There's lots of good stuff but hard to find on the web site.

https://www.victronenergy.com/suppo...tem-orion-tr-smart-dc-dc-charger-non-isolated

I use non isolated and think that's common. No need to switch the ground typically.

https://www.victronenergy.com/media...er_-_Non-Isolated/en/general-description.html

I'm assuming that your alternators do not have external regulators. Is that the case?

 

[NWpilot]

Yeah, it's tough wading through. You might look at some schematics. There's lots of good stuff but hard to find on the web site.

https://www.victronenergy.com/suppo...tem-orion-tr-smart-dc-dc-charger-non-isolated

I use non isolated and think that's common. No need to switch the ground typically.

https://www.victronenergy.com/media...er_-_Non-Isolated/en/general-description.html

I'm assuming that your alternators do not have external regulators. Is that the case?

Jeff,

I have Leece-Neville 105 amp alternators and they're not externally regulated. From what I can see the charger will work with with my alternators.

I've looked at some of the schematics and they're really busy. I'll go over the ones you noted and try to make sense of the system

Thanks for your help.

Chas

 

[Jeff F]

It seems it's just the two of us left standing [emoji846]

So here's my thinking...

You want a single house bank and two start banks, with all being charged when underway or when on shore power. When at anchor, all loads are on the house bank.

You haven't talked about your house needs. You probably don't know, but just a rough estimate. That dictates the size of your house bank, and possibly the charging architecture and battery type. If you're planning for overnight followed by a day's run you're not overly concerned with recharge time.

You've got good alternators but relatively crude regulation. You'd rather not spend $1,500+ on external regulators. The downside of relying on existing regulators is that a) the alternator is not heat protected, and if run at full capacity for long periods it will likely die a premature death, and b) the charging profile is sub optimal and somewhat arbitrary, so your battery choices are limited.

That argues for old school SLA start batteries, with each engine charging its own start battery. The alternators and AC charger will keep them happy. Simple and reliable.

How to charge house? Use a pair of 30a chargers, each drawing on a start battery. Configure them to only turn on when the source battery is being charged, either from alternator or shore power. They'll be independent but should play nice with each othe

This gives you completely independent regulation of your house bank, so you're free to choose your chemistry of choice.

The downside is that your recharge rate is capped at 60a, but that's probably NBD. That's offset by the maximum 30a additional load on the alternator, which prevents alternator overloading.

Upside is that you can use existing cabling to start batteries, and everything new is only carrying 30a, so easy and relatively cheap to do correctly.

A single 200ah AGM may be sufficient for a 'starter' house bank. Or two. Whatever. With a good quality charger your options are open and the batteries should be well cared for.

I'd also add a shunt to your house bank. I use the Victron Bluetooth unit, and at something like $125 it's a no brainer. The chargers will give you good voltage monitoring on the start batteries and house bank, so between them you'll have good insight into the system performance.

Maybe others can poke holes in this. I'm happy to have this critiqued.


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[SteveK]

I really need the help from experienced boaters about a new battery system.
My 30' Tolly has twin 120 HP diesels and each has an 8d battery. The electrical loads are split between the two batteries with most of the load on the starboard battery.

My current thinking is that the batteries were oversized so they could share the starting and house loads as according to sources it should take only 440 CCA to start the engines and I assume the 8d's to be much larger (sides are hidden from view). Both batteries need replacing so I'm looking at starting from scratch with a new setup, but also watching the cost.

What I'm thinking is to isolate one start battery and use the other one plus a house bank (200 A) to power everything else. I also have decided on AGM batteries because of their increased drawdown and lower maintenance. I would use one engine alternator (105A) to charge the isolated start battery and the other alternator to charge the the start and house bank.

Questions:
- Do I need an 8d battery to start a 220 cu.in. diesel engine? I'm an old guy and the thought of muscling 150 lb batteries in the bilge is depressing. A Trojan AGM 31 has 730 CCA and only weighs 67 lbs.
- Many sources I've read say there is little difference between start and deep cycle batteries and you can use a deep cycle for starting.
- Most AGM batteries I've looked at take a max charge of 60A, but I have 105A Leece-Neville alternators. How do I limit the charge to 60A?
- For the start/house side I assume I could use an automatic charging relay to manage the charge between the needs of the start and house batteries.

To those who have suffered through my confusing story, am I taking the right approach to this and making proper decisions?

Had to remind myself what the question was. It seemed like the solutions were given.
My personal preference is to have one start battery for both engines, one engine charges start and the other the house bank. No need for ACR or DC-DC setups. As mentioned a standard alt will not charge full tilt and the house batteries may not get topped up when running, so exterior regulator is needed. I have used a cross over and charged the house bank only with both engines, that will get a higher charge for a while.
As Jeff mentioned a shunt is needed to monitor results

 

[Bacchus]

Had to remind myself what the question was. It seemed like the solutions were given.

My personal preference is to have one start battery for both engines, one engine charges start and the other the house bank. No need for ACR or DC-DC setups. As mentioned a standard alt will not charge full tilt and the house batteries may not get topped up when running, so exterior regulator is needed. I have used a cross over and charged the house bank only with both engines, that will get a higher charge for a while.

As Jeff mentioned a shunt is needed to monitor results

I'm in violent agreement w Steve on this.
Why complicate the system unnecessarily?
Why separate battys for starting 2 engs? If you want insurance via redundancy use 2 - GP31s as a start bank and charge it from one existing Alt. Even internally regulated alts do an acceptable job with start battys. The draw is high for starting but time is short so AH needing replacement is fairly small and completed with a fairly short run.
Size house bank based on your needs and pick your chemistry... FLA least $, SLA mid $, AGM about 2X FLA $, Li only if it really makes sense for needs. You could get by with existing alt but if you want to optimize the charging system add external regulation and program for the house bank chemistry and size chosen.

An emergency batty Sw to connect house & start provides another level of insurance. Monitor for house w accurate V for start bank provides a wealth of info to confirm systems are operating normally and SOC for house.

I just replaced a pair of 10 yr old SLA Alliance battys (made by East Penn) in my motorhome starting a Cummins ISB 6.7. Battys showed normal V but only about half of rated 950 CCA after 10 yrs and still started the eng OK. I went with NAPA SLA with 1000 CCA rating (also made by East Penn).

 

[FlyWright]

Had to remind myself what the question was. It seemed like the solutions were given.
My personal preference is to have one start battery for both engines, one engine charges start and the other the house bank. No need for ACR or DC-DC setups. As mentioned a standard alt will not charge full tilt and the house batteries may not get topped up when running, so exterior regulator is needed. I have used a cross over and charged the house bank only with both engines, that will get a higher charge for a while.
As Jeff mentioned a shunt is needed to monitor results

I'm in violent agreement w Steve on this.
Why complicate the system unnecessarily?
Why separate battys for starting 2 engs? If you want insurance via redundancy use 2 - GP31s as a start bank and charge it from one existing Alt. Even internally regulated alts do an acceptable job with start battys. The draw is high for starting but time is short so AH needing replacement is fairly small and completed with a fairly short run.
Size house bank based on your needs and pick your chemistry... FLA least $, SLA mid $, AGM about 2X FLA $, Li only if it really makes sense for needs. You could get by with existing alt but if you want to optimize the charging system add external regulation and program for the house bank chemistry and size chosen.

An emergency batty Sw to connect house & start provides another level of insurance. Monitor for house w accurate V for start bank provides a wealth of info to confirm systems are operating normally and SOC for house.

I just replaced a pair of 10 yr old SLA Alliance battys (made by East Penn) in my motorhome starting a Cummins ISB 6.7. Battys showed normal V but only about half of rated 950 CCA after 10 yrs and still started the eng OK. I went with NAPA SLA with 1000 CCA rating (also made by East Penn).

Couldn't agree more with both of you! Question asked and answered well, OP decides to go another direction. Happens all the time. Hopefully he'll understand the simplicity of the best solution. This is exactly how my 34 is set up.

WRT batt switches, I moved mine out of the ER so I can access them immediately from the help without the need to enter the ER.

An SOC monitor is essential in making sure it all is working as planned.

 

[NWpilot]

I have received an abundance of information and advice from the people here on the TF and certainly appreciate it. Digesting all of it I had to make a choice of which approach to take based on the existing system and conditions in my boat. I'm sorry if some of you feel slighted if I didn't take your advice.

Here's the reasoning behind my decisions:

- I want to retain my existing battery wiring and switches because of expense and difficulty in rerouting.

- I have to rewire most of the low amperage wiring because the previous owner tapped both start batteries and both battery switches to power various items.

- I have estimated my house load for an overnight at anchor at about 150 AH, doubled it to 300 AH for 50% drawdown and rounded up to 400 AH. I plan on installing 2 each 200 AH deep cycles for house. On my overnight trips I plan to run a min. of 4 to 5 hours per day and theoretically the house bank will charge in about 3-1/2 hours from 50% discharge on the 30 amps or so from the DC-DC charger. On short trips I wont be using the house bank much.

- Everything I have read says I can start my 220 cu.in. diesels with about 500 CCA and I'm going to try and start one with a single 925 CCA battery. If that works I'll install one on each side. I have a third battery switch to link the two together in an emergency. One of the start batteries will be isolated with only an auto bilge pump wired to it. The other start will carry the ignition and minimal accessories. That is basically how it is wired right now except for the Rube Goldberg stuff.

- This approach allows me to use the maximum of my existing wiring and battery platforms and adds little to a very crowded bilge.

- This system means I need to buy two DC-DC chargers for $450 and perform minimal wiring. I had planned on adding a shunt anyhow.

I really do want to thank everyone for their knowledge and advice on my situation. I'll let you know how it works out, good or bad.

Chas

 

[ranger58sb]

I'm sorry if some of you feel slighted if I didn't take your advice.

Wouldn't worry about that. Most everyone here knows you're the one closest to the issue, and solutions from afar can't really see all the detail you can see from up close. Nor are we constrained by your budget, if that turns out to be relevant.

And sometimes, probably often, alternative solutions are meant to be useful for other readers too... even if they turn out to be a different path from your chosen plan.

Enjoy!

-Chris

 

[NWpilot]

Thanks ranger,

I saw the post turn into a battery discussion and many other issues that will help others that read this thread.
You're right about my personal situation. When I bought the boat I knew about a steering issue and fuel line issue. The survey only mentioned that the wiring connections were not up to ABYC standards, but the wiring is a birds nest and I have very little latitude to make changes to major systems without a lot of work.

Chas