How to add additional batteries

[REO]

I have done a careful measurement and I think I can place two group 27's in the generator room within 18 inches of the two group 27's in the engine room-maybe less depending on the location of the posts. I think I am understanding that the jumpers to parallel the 4 batteries need to all be the same length, and as short as possible. At 18 inches I may or may not need a bus bar since the current jumpers are already about 12 inches, and making a few jumpers a bit longer seems like a simple solution???
The video posted by rsn48 has convinced me that the group 31 firefly oasis battery is a very good option, better than standard AGM, if I can fit them in. But two statements in the presentation confuse me. First he states that lithium batteries cost 10 times as much as AGM. The presentation was in 2019. My online shopping shows a 200 ah at about $800. Several manufacturers at about the same price. That makes lithium well worth the small price increase. What am I missing? More importantly, he says that I will have to change all the charging parameters to accommodate the lithium. That may eliminate lithium, but what exactly does that mean. I will have to get a new battery charge anyway. What else would be needed.
This seems like it should be a fairly simple little project, but I'm amazed at how complicated it is.

 

[ranger58sb]

First he states that lithium batteries cost 10 times as much as AGM. The presentation was in 2019. My online shopping shows a 200 ah at about $800. Several manufacturers at about the same price. That makes lithium well worth the small price increase. What am I missing? More importantly, he says that I will have to change all the charging parameters to accommodate the lithium. That may eliminate lithium, but what exactly does that mean. I will have to get a new battery charge anyway. What else would be needed.
This seems like it should be a fairly simple little project, but I'm amazed at how complicated it is.

Might have been a true cost Lithium/cheap AGMs comparison then, although probably lithium never was 10x the cost of Fireflies.

Two things: first, lithium batteries need a battery management system (BMS), so the costs your seeing, if just for bare batteries, might not be the whole story.

Second, I've not seen anyone rave about lithium being used as engine start batteries.

That's just from my reading, though; no first-hand knowledge.

If you can fit in G31 Firefly Oasis batteries, you could also fit in slightly less expensive Odyssey Extreme PC-2150s (G31s), or Lifeline G31 XTs (125-Ah each)... so you might compare those costs too. And then there are also other even less expensive AGMs by East Penn/Deka, Trojan, etc.

And you could probably fit in 4x Lifeline 6Vs (at least 440-Ah total) too, assuming you have enough height. I think their horizontal footprint is closer to a G24, something like that... and if you have more extra height, the taller versions could add more Ah from there.

-Chris

 

[REO]

Thanks for that input. I saw mention of BMS, and figured that would add both cost and complexity. I'm going to stick with AGM's. You have given me some good options to check out. I don't have much height in the engine compartment space, so I'll focus on the ones that are 10" or less high.
I'm beginning to think that the jumper cables may not be a problem either. By relocating the generator battery I can now see that I can get the engine room batteries and generator room batteries right next to each other. It's an L shape, but they have only a 2" bulkhead between them. Am I correct that the trick is to make all jumper cables exactly the same length?
I'm also convinced that I should replace my 20 amp charger because it will take too long to recharge depleted house batteries at anchor. The battery wizard on the boat show video recommended a high amp 3 stage charger that can be tuned for the type of batteries it is charging. Any recommendations?

 

[Helmsman]

Thanks for that input. I saw mention of BMS, and figured that would add both cost and complexity. I'm going to stick with AGM's. You have given me some good options to check out. I don't have much height in the engine compartment space, so I'll focus on the ones that are 10" or less high.
I'm beginning to think that the jumper cables may not be a problem either. By relocating the generator battery I can now see that I can get the engine room batteries and generator room batteries right next to each other. It's an L shape, but they have only a 2" bulkhead between them. Am I correct that the trick is to make all jumper cables exactly the same length?
I'm also convinced that I should replace my 20 amp charger because it will take too long to recharge depleted house batteries at anchor. The battery wizard on the boat show video recommended a high amp 3 stage charger that can be tuned for the type of batteries it is charging. Any recommendations?

Good call. I would not go with lithium. Rather than go through all the reasons, take a few minutes to read through Jim Healy’s discussions on lithium. https://gilwellbear.wordpress.com/ this link should show you his second article on lithium batteries for marine usage.

In terms of how you cable the batteries, you can search that and the diagrams will pop up showing the best way to balance the amount of charges flowing though each battery. The thing to keep an eye on is the charge acceptance rate of the battery bank you build. If you have a 400 amp AGM bank, it will accept a higher charge from your alternator than a 400 amp wet cell. Running an alternator at max capacity can burn your alternator up. That is an even bigger issue for lithium’s.

 

[ranger58sb]

Am I correct that the trick is to make all jumper cables exactly the same length?
I'm also convinced that I should replace my 20 amp charger because it will take too long to recharge depleted house batteries at anchor. The battery wizard on the boat show video recommended a high amp 3 stage charger that can be tuned for the type of batteries it is charging. Any recommendations?

Yes, same length for all is best.

I've had good luck with the ProMariner (same as Sterling) chargers, with remote panel. Most recent was a 60A ProNautic. Can't say how they compare with others.

If you think you might want an inverter, changing to an inverter/charter now might be a decent option. We had the ProMariner 2000W pure sign wave one, which includes a 70A charger... and the built-in transfer switch is automatic.

-Chris

 

[Bacchus]

Thanks for that input. I saw mention of BMS, and figured that would add both cost and complexity. I'm going to stick with AGM's. You have given me some good options to check out. I don't have much height in the engine compartment space, so I'll focus on the ones that are 10" or less high.
I'm beginning to think that the jumper cables may not be a problem either. By relocating the generator battery I can now see that I can get the engine room batteries and generator room batteries right next to each other. It's an L shape, but they have only a 2" bulkhead between them. Am I correct that the trick is to make all jumper cables exactly the same length?
I'm also convinced that I should replace my 20 amp charger because it will take too long to recharge depleted house batteries at anchor. The battery wizard on the boat show video recommended a high amp 3 stage charger that can be tuned for the type of batteries it is charging. Any recommendations?

Same length cables to a buss bar is one way to balance a bank. Another is to have all paths through the arrangement the same length but each cable doesn't have to be the same.
Here is a good resource for balanced wiring.
https://www.google.com/url?sa=t&sou...UQFnoECAwQAQ&usg=AOvVaw1xnSa4_fWmzimYpjiXESM7
The alternative may or may not have an advantage vs buss bar, with your split location. You might play with the alternatives.

 

[rwidman]

My batteries are g27. About 12 x 6.5 x 8.5 inches. I think I can find space for something a bit larger, but not much. I'm going to do some online battery shopping to see what is available.

You may have to replace the battery boxes (if that's what you have), but group 31 batteries are not physically much bigger than group 27.

 

[Bacchus]

You may have to replace the battery boxes (if that's what you have), but group 31 batteries are not physically much bigger than group 27.

Agree.
Gp 31s are 12-15/16 L X 6-3/4 W X 9-3/8 H

I am planning on replacing my (3) AGM 8Ds with a pair of East Penn / Duracell GP31 AGMs for each - 2 for thruster / eng start and 4 for house
Note AGMs serve both applications well and are not the compromise that FLA start vs deep cycle posses. Many publish both CCA & AH specs for compariosn

 

[REO]

After clearing out some measuring room and carefully looking at the space in the generator room, I find that I can get 3 -4 volt firefly Oasis heavy duty batteries in the generator room. Boxed in a straight line and wired in series , 450 amp hours. About the same price as their group 31 version. These batteries are 17.5 inches high and have a smaller footprint. The brochure does not mention marine application, so I am going to call the company tomorrow to discuss. This set up frees up space in the engine room maybe for inverter/charger, and avoids putting the batteries in two different places.
The technology behind these batteries is promising and may be worth the extra cost.

 

[drb1025]

After clearing out some measuring room and carefully looking at the space in the generator room, I find that I can get 3 -4 volt firefly Oasis heavy duty batteries in the generator room. Boxed in a straight line and wired in series , 450 amp hours. About the same price as their group 31 version. These batteries are 17.5 inches high and have a smaller footprint. The brochure does not mention marine application, so I am going to call the company tomorrow to discuss. This set up frees up space in the engine room maybe for inverter/charger, and avoids putting the batteries in two different places.
The technology behind these batteries is promising and may be worth the extra cost.

I installed six 4v Fireflys for 900ah. They work great for marine application.

 

[ranger58sb]

After clearing out some measuring room and carefully looking at the space in the generator room, I find that I can get 3 -4 volt firefly Oasis heavy duty batteries in the generator room. Boxed in a straight line and wired in series , 450 amp hours. About the same price as their group 31 version. These batteries are 17.5 inches high and have a smaller footprint. The brochure does not mention marine application, so I am going to call the company tomorrow to discuss. This set up frees up space in the engine room maybe for inverter/charger, and avoids putting the batteries in two different places.
The technology behind these batteries is promising and may be worth the extra cost.

There are several threads about the Firefly 4V batteries on cruisersforum.com, and Bruce Schwab (Ocean Planet) often posts there.
Could well be a very good choice.

I'm not usually in favor of a solution where if one battery (in a bank) goes south, the boat engine won't run. OTOH, if you can have a separate generator battery... and a switch that lets you start the main from that genset batt... all good.

-Chris

 

[REO]

The wiring on my boat was all redone by PO several years back. It was a good job, just not right for my purpose. I'll keep the starter battery wiring and use a small agm. The generator battery will be removed and wiring will be rerouted to the starter battery. I also have a small jumper pack that I carry for an emergency. Finding the firefly's that will fit in the generator room really solved the main issues. One last question about equipment. I have a good quality three stage 20 amp charger. I could leave it wired to the starting battery and just use the new inverter /charger to charge the house bank. Seems like overkill on chargers, but why rip out a good system that is already there?

 

[ranger58sb]

One last question about equipment. I have a good quality three stage 20 amp charger. I could leave it wired to the starting battery and just use the new inverter /charger to charge the house bank. Seems like overkill on chargers, but why rip out a good system that is already there?

I think that's what I'd likely do, same reasoning. I went for years without a charger on the genset battery, and that worked well enough... genset alternator doing the charging...

But if I'd had a good spare charger hanging around and available, I wouldnd't have turned my nose up at it.

-Chris

 

[Jc180]

Sorry for the late add. Several thoughts:
1. AGM batteries generally require full recharging. Do you know if Firefly’s fall into this category? Down side is considerably longer gen set recharge runs for that last 10%.
2. Trojan 6 V golf car batteries can be watered remotely with their battery watering system. I use it and works great. It consist of a hand pump bulb (like your outboard motor fuel hose) and tubing to each battery vent.
3. Balmar has a solid state “Duo Charge” which allows one battery to charge another of different type. I have had two in service for over 10 years without issue.

 

[dhays]

3. Balmar has a solid state “Duo Charge” which allows one battery to charge another of different type. I have had two in service for over 10 years without issue.

I’ve had two that have been in service for 10 years as well. They are a great product but I’ve had two issues.

1. Don’t use a Duo Charge to charge a start battery for a Cummins electronic engine. They just don’t get along. Use an Echo charger instead. It works great.

2. The Duo Charge has a 30amp charge limit and will shut down if their is a prolonged demand for more than that from the battery to be charged. I have run into this problem a few times as the Duo Charge charges my Thruster bank.

Beyond that, I think they are great products and have been incredibly reliable. Besides the thruster bank, I use a Cuo Charge to keep my Genset start battery charged.

 

[Jc180]

Sorry for the late add. Several thoughts:
1. AGM batteries generally require full recharging. Do you know if Firefly’s fall into this category? Down side is considerably longer gen set recharge runs for that last 10%.
Again, sorry for the late add: need to consider voltage profile of Firefly batteries. Even though they can tolerate a lower state of discharge, if the voltage is also lower into the 11s range, then your hardware, especially danfoss (secop) compressors won’t tolerate well.

 

[drb1025]

Sorry for the late add. Several thoughts:

1. AGM batteries generally require full recharging. Do you know if Firefly’s fall into this category? Down side is considerably longer gen set recharge runs for that last 10%.

Again, sorry for the late add: need to consider voltage profile of Firefly batteries. Even though they can tolerate a lower state of discharge, if the voltage is also lower into the 11s range, then your hardware, especially danfoss (secop) compressors won’t tolerate well.

One of the advantages of Fireflys is that they do not need to be fully charged, tolerating partial state of charge very well and without sulfation. Thus they are great for the way many of us boat.

 

[REO]

I spoke with Farron at Beta Marine. He thought the firefly batteries, configured as I described were a good option. He also told me that my alternator is internally regulated and is not a smart alternator. He is sending a wiring diagram and information on how to convert to a three stage smart regulator. I'm going to keep the current system, and evaluate how it does based on how we use the boat. Our plan is to spend a few days on the hook and then a day or two in a marina. Since the fireflys are supposed to tolerate less than full charge, and we can achieve full charge with a good three stage charger at a marina this may be a good system. When the dust settles from this thread I'm going to do some serious research on the best battery monitoring system. I'm amazed at how far I have been able to come in understanding my battery needs and options. I could't have done it without trawler forum. Again, thanks for all the help.

 

[ranger58sb]

I think that's what I'd likely do, same reasoning. I went for years without a charger on the genset battery, and that worked well enough... genset alternator doing the charging...

But if I'd had a good spare charger hanging around and available, I wouldnd't have turned my nose up at it.

Additional thoughts...

You can also keep the 20A charger connected to your new bank -- as well as the genset battery -- along with a new inverter/charger if you're going that way. Multiple chargers on the same bank can usually work and play well together, so you might gain a slight bit more "recharge speed" at anchor. Matching voltages to batteries for a brief time on anchor might not be as important as it could be for long-term charging at the doc.

And/or... we went for years without any charger at all on our genset battery. How many times to you use an external battery charger on your car? Probably zero, probably you alternator is all you've got. The battery's start load is immediately replenished (sorta kinda) by the engine battery as it runs.

I still think your 20A charger could be useful, but I'm thinking more about augmenting the inverter/charger (which maybe won't be much) and/or onboard backup if the inverter/charger goes south while you're out somewhere. Won't hurt to keep it on the genset, of course.

-Chris

 

[Bacchus]

Additional thoughts...



You can also keep the 20A charger connected to your new bank -- as well as the genset battery -- along with a new inverter/charger if you're going that way. Multiple chargers on the same bank can usually work and play well together, so you might gain a slight bit more "recharge speed" at anchor. Matching voltages to batteries for a brief time on anchor might not be as important as it could be for long-term charging at the doc.



And/or... we went for years without any charger at all on our genset battery. How many times to you use an external battery charger on your car? Probably zero, probably you alternator is all you've got. The battery's start load is immediately replenished (sorta kinda) by the engine battery as it runs.



I still think your 20A charger could be useful, but I'm thinking more about augmenting the inverter/charger (which maybe won't be much) and/or onboard backup if the inverter/charger goes south while you're out somewhere. Won't hurt to keep it on the genset, of course.



-Chris

I debated whether to connect t my multi bank charger to my gen start when I did some batty bank rewiring. I wasn't anxious to constantly be charging a small GP 24 batty in parallel with a large (2 - 8D) house bank.
I finally decided to not charge the gen batty on a regular basis along with my house & start.
What I did do thanks to another TFers suggestion was to replace by gen batty on/off switch with a 1-2-all switch, with same foot print & bolt holes, with a jumper to my house bank. The benefits are... let's me combine battys in a situation where gen batty is too weak to start gen ( hasn't happen yet) and it let's me "top off" the gen batty charge if I havent run it in some time to have the gen alt charge it up.
I like this set up and feel more comfortable having an easy back-up.

 

[ranger58sb]

I debated whether to connect t my multi bank charger to my gen start when I did some batty bank rewiring. I wasn't anxious to constantly be charging a small GP 24 batty in parallel with a large (2 - 8D) house bank.
I finally decided to not charge the gen batty on a regular basis along with my house & start.

That was why I eventually took our genset battery off of our original 40A charger on that boat. Two 300-Ah banks (at the time), and the third bank was a 68-Ah G34, roughly similar to a G24 I think. Noticed some higher temps one day on the small genset battery, confirmed the generator engine had it's own alternator, did some thinking, disconnected that battery.

The charger manual did indeed mention potential issues with disparate size banks. OTOH, when I bought into the new-to-me Odyssey batteries at the time, the tech at Odyssey Southeast told me he thought it wouldn't be an issue. But then it eventually turned out (seemed to me) there may indeed have been a size disparity issue...

Another small benefit was that the whole 40A became available to the two larger banks; not a huge improvement, but I reckoned every little bit helped when we wanted to recharge at anchor.

(I later added another charger to one large bank, and an inverter/charger to the other... and the original 40A charger was also still in service and available to augment one or the other or both.)

-Chris

 

[REO]

I think I will use the existing charger as wired and add a charger / inverter to the house bank. Last time I purchased an inverter was 25 years ago, so I will need to do some research. We will have a lot of 110 volt stuff (air conditioner refrigerator, microwave, cook top, coffee maker, tv /dvd, etc.), but I see the inverter used for the microwave, coffee maker and tv. Everything else needs the generator or shore power. I may wire specific outlets for inverter only to avoid an accidental draw down.

 

[ranger58sb]

We will have a lot of 110 volt stuff (air conditioner refrigerator, microwave, cook top, coffee maker, tv /dvd, etc.), but I see the inverter used for the microwave, coffee maker and tv. Everything else needs the generator or shore power. I may wire specific outlets for inverter only to avoid an accidental draw down.

We used the inverter/charger for all (excepting fridge) AC outlets. That in turn meant all open outlets (laptop charging and so forth) but also TV/entertainment system, microwave, coffee maker. Didn't have to use inverter for fridges (though I could have), since ours were already AC/DC units.

Never really had an issue with accidental draw down; it was easy enough to just pay attention.

-Chris

 

[Flatswing]

Consider keeping generator gel start battery isolated from system & just check that it’s alternator works regularly with a clamp on DC meter. Rather than adding the expense of complex wiring & switches that I can mess up, I carry HD jumper cables long enough to jump generator house or starter batteries for the inevitable screw up/failure.
As others have suggested, Upgrading your battery charger to a 60A & using same battery chemistry for house/starting may significantly reduce the bulk phase/cut your gen run time.

 

[REO]

I think I've settled on the batteries and wiring arrangement. Fortunately almost all of my current 12 volt wiring will be usable. The battery combiner between the house and starting battery will work. The 20 amp charger can stay. A new 450 amp hour house bank, of firefly batteries combined with AMG starting and generator batteries should give me sufficient power and reliability. The current wiring includes a 1-2-both switch, and Blue Seas battery combiner I also plan to carry a portable jumper, just in case. I need to make a decision on a new charger / inverter, but I think I have enough info at this point to start the final search.
My next task is to get the new engine out of the bed of my truck and installed in the boat. After the engine is in I have to do some research on battery monitors, but I'll start a new thread for that topic. I noticed that this thread has appeared as a new listing. I hope I didn't inadvertently do that.

 

[Caballero II]

OK. What is ACR, please?

 

[Helmsman]

OK. What is ACR, please?

It is an automatic charging relay. The way I think of it is an automatic battery switch which parallels two batteries for charging and separates when them when the charge is not present. Here is an article that goes a little more in depth.

https://marinehowto.com/automatic-charging-relays/

Hope that helps!

 

[Caballero II]

That helps quite a bit. Good article which I will try to save somehow.