Changing House Bank Battery Types

[TBill36]

Looking for some guidance and apologize if this was cover elsewhere, but I can't find the specifics elsewhere,

I currently have 2 100AH LA batteries as my house bank, which I believe should be sufficient for my needs. However, I've had instances of boiling and overheating one of the batteries and I'm thinking of going to either AGMs or LiFePo4 batteries.

Some background on how I use the boat.
I have an apartment size refrigerator and 5 cu ft freezer that are run off the inverter. Combined they take about 10 amps when running which I calculate as 50% of the time to be conservative. Occasionally, I'll go about 5 hrs without the engines or generator running. Even if I double that to account for LED lights for a few hrs I should be well within the 50% discharge.

I have a magnum MS2012 inverter with the charger adjusted to 60 amps max output.

The alternator is a Leese-Nevelle 90 amp with standard internal regulator.
I'm pretty diligent on maintaining water levels in the batteries, but I've boiled one of them dry on 2 sets of batteries now over the past 4 years. I'm done with battery maintenance.

I also have an ACR that connects to my start batteries and other 50A Leese-Nevelle internally regulated alternator.

So now I'd like to go either AGM or LiFePo4. If AGMs I'm thinking Trojan T105 AGMs at about $500 or Ampere Time LiFePo4 at 200 AH for $700.
I think AGMs are a direct replacement for the flooded LAs with a change to the charging profile on my inverter, but the LiFePo4s may need some alternator changes, like adding a Balmar external regulator which adds another $300 or so. With my needs, I don't know if I need this and would just go with the AGMs if it is required.

I also want to get rid of the ACR as it's causing alternator issues on the other engine and I'm not sure it's helping anything with 2 alternators in the system. My start batteries are never an issue and last many years. They have their own 20 amp charger. But if the ACR is left in, it might provide a charge path for the alternator if the Li BMS cuts the path to the alternator for some reason.

Any thoughts or guidance is appreciated.

 

[DavidM]

If you are willing to go with the low cost Amperetime lithiums, why go with expensive Trojan AGMs. For your needs a pair of Windynation or Renogy G31, 100 amp hour AGMs should work fine for about $400 for the pair. No change to your charger or alternator regulators.

David

 

[ranger58sb]

So now I'd like to go either AGM or LiFePo4. If AGMs I'm thinking Trojan T105 AGMs at about $500 or Ampere Time LiFePo4 at 200 AH for $700.

I think AGMs are a direct replacement for the flooded LAs with a change to the charging profile on my inverter, but the LiFePo4s may need some alternator changes, like adding a Balmar external regulator which adds another $300 or so.

Probably have to do a long-term cost/cycle estimate...

I would agree the change to AGMs is likely easiest with just maybe a change to charger settings. You could also compare the Trojan AGMs (they still make those?) with Lifeline GPL-xCT or L16 6V AGMs, and with Lifeline/Odyssey/Northstar 12V AGMs.

The LiFePO4 switch may also require a BMS, if it's not already included. (I didn't review the ones you mentioned.)

-Chris

 

[Bkay]

If your main objective is to avoid the maintenance on the batteries, then I think DavidM is on to something. Avoid all the drama of LiFePo system conversion and go with G31 AGM. Also, it sounds like you have some space to work with, so possibly 2 x GC-12 size AGM and get a little more Ah available without too much additional space.

I really like LiFePo technology, but it doesn't sound like you really need all the advantages it provides and are a candidate for AGM.

 

[TBill36]

Thanks for the replys. The reason I went with T105s was I could not find any decent discussions or recommendations for inexpensive AGMs. The T105s have a pretty good reputation. My plan was 2 6v paralleled together. The Amperetime batteries were pretty well thought of over in the solar word, so that and price is why I considered them. My gage of good Lead batteries is reputation and how much they weigh. I see the Windynation comes in at 67 lbs which is pretty good for a G31. I'll see if I can find any testimony for that brand, or if anyone is using them, I'd certainly like to know what they think. As I went down the path, the LiFePo started to look worth it for a few hundred $s more. But it looks like they add other complications that drive the cost up to where it's just not worth it.
Thanks again for the comments.

 

[fgarriso]

We use all AGMs. I know the LiFePo have advantages, but to cost of everything that goes with them is pretty steep.

 

[firehoser75]

Bill,
I am not a marine technician/electrician. However, my concern is with your charging system, based on your comments of "boiling dry" lead acid batteries several times (if I read that right). Unless you do not check the fluid level very often, there is no reason (that I am aware of) a properly operating charging system should boil dry a battery in good condition, in less than a month (I checked my fluid levels monthly and never even came close to exposing the plates).

A "regular internally regulated" alternator will not adequately recharge a house bank. Just saying, that is what I had on both my boats with battery monitors, and it never came close to doing a complete job. Often, even after motoring for several hours, I would only gain a very small amount of charge improvement, but at least, the charge did not diminish.

AGM batteries will remove the fluid checking, but they are more sensitive to being operated in a partially charged state than lead acid, and unless you regularly get them back up to a full 100% charge, they will have a less than optimal life. Maybe look at the Firefly Carbon battery??
Personally, I think you may need to have someone check out your entire charging system to avoid "killing" whatever new batteries you install.

 

[Bacchus]

I have switched all boat and motorhome house to AGM and will second David EMs recommendations.
I have Eadt Penn AGM on the boat 8 seasons and used Sams Club Duracell made by EP for the motorhome. You can by "higher quality" but IMO at Sams Club prices it would be hard to come out ahead on a $/AH/ life cycle.

 

[firehoser75]

I have switched all boat and motorhome house to AGM and will second David EMs recommendations.
I have Eadt Penn AGM on the boat 8 seasons and used Sams Club Duracell made by EP for the motorhome. You can by "higher quality" but IMO at Sams Club prices it would be hard to come out ahead on a $/AH/ life cycle.

Totally agree with this except, for an even better $/AH/life cycle cost, it is very hard to beat flooded lead acid golf carts from the Sams Club or Costco, etc. Yes, there are some advantages to battery technologies like AGM, and for certain situations they are the best choice, but for most, these reasons are not that important (other than preference ).

Being as a lot of boat owners actually "murder" their house bank batteries predominantly by regularly operating them in a partial state of charge (not fully recharging them between discharges), (or not giving them the correct charge profile) generally speaking spending more on "better quality" batteries usually means just costing more when time to replace them comes after a shortened life. The "longer expected" life from a "quality" battery will not be achieved if they are not treated (often recharged fully with the proper charge profile) and maintained properly.
Just some thoughts

 

[DavidM]

Well, I have had two Windnation G31, 100 Ahs each in my motorhome for about a year and they have worked fine. I like not having to check/add water but also their low self discharge rate relative to FLAs.

But I think that most AGMs including Duracell and Renogy could also work well. I have long suspected that there isn't any difference between starting and deep cycle batteries for AGMs, unlike FLAs.

Trojan is right there up with Lifeline in FLA quality, and I have no doubt that their T105, 6V AGMs would work great as well.

David

 

[BruceK]

Looking for some guidance and apologize if this was cover elsewhere, but I can't find the specifics elsewhere,

I currently have 2 100AH LA batteries as my house bank, which I believe should be sufficient for my needs. However, I've had instances of boiling and overheating one of the batteries and I'm thinking of going to either AGMs or LiFePo4 batteries......
Any thoughts or guidance is appreciated.

I`m with Firehoser, boiling/overheating batteries raised a red flag,that should not be happening. And 200ah of house battery sounds modest.
I suggest checking your charging systems. That resolved,AGMs sound a good choice.

 

[mvweebles]

Thoughts.

Renogy customer service sucks. Products are mostly okay if they work. If they don't, good luck with an RMA. I called on a DOA inverter and was #43 in line.

Going lithium does take some expense and effort. But I know of no one who has made the swap that has regrets. Especially with a relatively modest house bank as OP.

Check out SOK 200ah LFP for arounf $1k delivered.

https://www.sokbattery.com/products/12v-206ah-lifepo4-lithium-iron-phosphate-battery-pack

Peter

 

[Bacchus]

Firepower
No argument re FLA can't be beat for pure economics.
I hate the maintenance due to corrosion and the higher probability of poor maint leading to premature death in spite of my good intentions. I'm willing to pay the AGM premium to avoid those issues.

Well, I have had two Windnation G31, 100 Ahs each in my motorhome for about a year and they have worked fine. I like not having to check/add water but also their low self discharge rate relative to FLAs.

But I think that most AGMs including Duracell and Renogy could also work well. I have long suspected that there isn't any difference between starting and deep cycle batteries for AGMs, unlike FLAs.

Trojan is right there up with Lifeline in FLA quality, and I have no doubt that their T105, 6V AGMs would work great as well.

David

David
Both East Penn and Trojan have confirmed your suspicions when I asked their tech reps. AGM GP31s and AGM GCs work equally well as starting or deep cycle.
They didn't elaborate but I assume the AGM plate & support are the same vs different when looking at FLA. Many / most AGMs AGMs will spec both AHRs and CCA/MCA reflecting their dual performance.
Some misunderstand the distinction and fall back to the generalization that a dual purpose FLA is a pair compromise and not best suited for either use.

 

[DavidM]

Thanks Don. When you think about it there are three things that differentiate deep cycle FLAs from starting FLAs.

1. Plate thickness. Deep discharge of thin plate FLAs will soon result in plates that look like swiss cheese. You need enough plate material to deal with the lead sulfate that can collect in the bottom with deep discharge. See next item.

2. More room at the bottom for sulfate build up on deep cycle FLAs.

3. More room at the top for extra electrolyte on FLAs before exposing the plates.

And of course, caps to check and add electrolyte. It is surprising how many SLA batteries are advertised as suitable for deep cycle use. NFW!

None of these apply to AGMs given the way they are built.

David

 

[Bacchus]

David
Exactly my thinking. Neither EP not Trojan elaborated but my assumptions are along the same lines as you stated.
No need for depth below plates... no sulphation sluffing off
Plates are supported by mat and thicker plates not required
No flooding so space above plates meaningless.

 

[TBill36]

Again - thanks for the help.
As mentioned by Tom, I do want to address the boiling as it should not be happening, unless it's the house alternator or the ACR. I'm taking both alternators to the shop on Monday and plan to do away with the ACR. I had the same boiling issue with a different inverter/charger that I was measuring 70 charging amps on and it was not temperature compensated. Replaced it with the Magnum which is temperature compensated and able to control charge output. Still boiled a battery.
So checking alternators, eliminating the ACR, and going to batteries that I don't need to water should make it as basic as it gets. For the extra $s, it may still be worth going with the T105 6v agms as there are less cells that can fail than going with 12v. Still on the fence with that one.

 

[tpbrady]

I don’t see where the ACR could be the issue. It doesn’t change overall amps being output, it just combines two banks together when the voltage on either bank reaches 13.6v and isolates them when the charging source goes away. Kind of sounds like one of the charging sources is not playing nice. Do you have the Magnum battery monitor? If not consider getting it as you can see state of charge and more importantly amps in and out. Another alternative is the Victron Smart Shunt. That allows you to see the amps in and out using a smartphone and Bluetooth. No wiring except right at the battery bank.

Tom

 

[BruceK]

Regarding the charger, are there variable settings? Is it set to the correct battery type? There should be settings for charge cutting in, charging voltage, charge cutting out, and equalization. The last is a potential battery hammerer, raised charge voltage and pulsing, the idea being to belt any sulfation back into solution. I used to find my FLAs needed topping up post equalization, which may be set to happen once a month.
It may be something else, but to me this is a real possibility.

 

[TBill36]

I do have the Magnum battery monitor and it is set to LA batteries. I also set the limited of the max charge to 60 amps per the C calculation for 200 AH. Whenever you turn off the Magnum, it starts up in absorption stage even if the batteries are full. But it will quickly reduce amps to negligible amount until it goes to float.

The ACR complicates things in my head. From what I understand, when one alternator senses the voltage from the other it shuts down that alternator. So I would not get the output of both alternators anyway even under a high load situation, which is why I added the ACR in the first place. Also, I don't want any more than 60 amps going into the bank, so maybe if both were to contribute I'd exceed that for some amount of time. Also, maybe the 90 amp alternator senses the starting batteries and keeps dumping amps into the house bank, even if the start batteries are up. I think I'm OK with a 90 amp alternator as that is the max output and I don't think they sustain that very long. With my usage, I try not to charge the battery bank with the alternator. If I'm down, I crank up the generator and use the charger so I don't cook the alternator. But somehow, I think my alternator is putting out too much under some running condition. I've measured output at the dock with elevated RPM and it seems to be OK and tapering down when I measure it, but every once in a while something is over charging - and from what I can tell it's happening when my engines are running and the alternators are operating. I do run the inverter when I'm running the engines, so maybe somehow the alternator is not sensing the charger amps and vice versa and dumping too much into the bank. Part of the reason I'm eliminating the ACR.

 

[tpbrady]

An alternator doesn’t sense voltage per se from the other alternator and shut down. A “dumb” internally regulated alternator senses voltage on battery bank and keeps at or below its rated voltage output. The question is while charging how many amps are going into the batteries at what voltage. In most cases a large number of amps indicates something wrong in the battery bank and too many volts something wrong in the charge source. Either one will not be nice to the batteries. The BMK can tell you a lot.

 

[Kit_L]

Joining to see where this thread concludes. I installed a Victron BMV-712 and shunt in my last vessel, and it was excellent, showing amps in and out, as @tpbrady said. It was easy to see imminent battery failure via this device, again in the case of the last boat.

 

[TBill36]

I think I may have found the culprit - overcharging. My current bank is 2 12v 100 amp hr batteries. One of them was dry with plates exposed. I ordered new 6v agms to replace them. In the mean time I refilled the low battery and then left engine room lights on mistakenly overnight. I measured about 6v on the bank. Started the engine and raised rpm to 1500 to get alternator working and turned on the Magnum to charge. I measured 80 amps going into the batteries - 40 was coming from the Magnum and 40 was coming from the Alternator. Ran for about 10 minutes and the Alternator measured 140F. Shut down the engine and left the charger on over night. The next day the charger was still putting 20 amps into the batteries and the one that had been dry measured 150F. Shut it down and took the compromised battery out and left the other battery connected to run pumps, lights, etc. until I get the new batteries.

So the bottom line is I was applying too many amps to the 200 amps system. .2C says I shouldn't have exceeded 40 amps. The 80 amps was probably boiling off the water quickly and then runaway heat up shorting, warping plates etc.

I don't have room for additional batteries without moving them away from the short run to the inverter, and I don't need any more capacity for my use other than the potential over charge. I don't want to downsize the alternator because it would then be undersized for when I'm up and running using all my electronics and other stuff.

I'll see what the charging amps are with the new AGMs. If still too high, I won't run both charging sources at the same time and hopefully keep it under 40 amps.

 

[firehoser75]

I am happy for you that you discovered an issue with your charging system before that issue "ruined" your new AGM batteries! AGM batteries are even more sensitive to being treated poorly than flooded lead acid. A suggestion: It may be in your best interest to hire a qualified marine electrician to come aboard and check out your charging system to ensure it will not only meet your needs, but not actually "murder" your new batteries. Unless there are many or very difficult issues, I am reasonably sure the electrician would only require an hour or two to test out your setup? Then you could be confident all would be working as needed.
Up to you how you spend your time and money. Good luck.

 

[Kit_L]

I'm glad you discovered this as well. I want to add that some models of AGMs are even less tolerant of overcharging that FLAs—for example, a popular AGM here can only tolerate 30amps during the bulk phase; see here:

https://www.aussiebatteries.com.au/batteries/deep-cycle-agm/140ahx-12v-agm-deep-cycle-battery

The key info:

Bulk charge: Initial Charging Current less than 30A.
Voltage 14.5V @ 25oC
Temp. Coefficient -30mV/oC

Please do check this critical spec. on your new AGMs, and make sure it's not exceeded. Best of luck, and @firehoser's suggestion is an excellent one, IMHO.

 

[tpbrady]

Since the bank was essentially dead when you started charging it, drawing 80 amps would not be unexpected. The alternator and Magnum were both contributing amps. Since the battery that was dry before you left the lights on overnight, it was probably mostly discharged and was drawing down the other 12v battery connected to it. The lights contributed to discharging the bank, but the dry battery was more than likely the culprit. I can't see where the chargers were at fault. It would seem to be the battery bank. Normally when I am charging batteries, I only want a single charging source that I can monitor so I know exactly how it is performing. While the BMK can tell you the total amps being sent to the batteries, it won't tell you what each charging source is providing unless you can individually measure them. That's why I shut one down unless I think the battery bank needs it. In my case I have 700 AH, with a 200A engine alternator and 120A Victron Charger. Either one can normally satisfy the charging requirements for the bank.

The alternator in your case has no advanced charging profiles so it was probably providing most of the amps to the batteries when it was running while the Magnum was following its charge profile: bulk, absorption, float. The alternator was heating up because it was working pretty hard. When you got there in the morning, the Magnum was still trying to charge a bad battery so the amps it was putting out were being converted to heat and not a chemical reaction to restore a charge.

I think the bad battery was the problem that can be tested by simply isolating it and measuring the voltage across the terminals after it has been sitting for a few hours. There are 6 cells putting out 2.1 volts or so each when fully charged. If after sitting you see only 10 volts or less across the terminals there are one or more bad cells. The other 12V was probably damaged in the process so your plan to replace both with 6V batteries in series is good. Just watch the BMK for voltage/amps in and amps out when not being charged as that is a good indicator of what is going on. Don't blame the alternator yet.

Tom

 

[SteveK]

I find this thread an interesting learning topic.
I have found answers in bits and pieces except for this link that has it all covered.
Fisheries Supply Battery charging 101

Here another link How to Calculate the battery charge rate which suggests charging at 10% of the battery Ah

 

[ranger58sb]

Some makers just tell you their recommended charge rate, no calcs required.

Odyssey and Lifeline come to mind, but I'd guess others too...

-Chris

 

[TBill36]

I agree with Tom for the most part. The compromised battery was certainly skewing the data. I'm sure it's got shorted cells as the case is bulged and it was hot when charging - even when full of water. The 2 batteries connected together were pulling about 6 amps when I first checked and found the one dry. The magnum stays on all the time when the boat is docked. I don't think the amp draw changed much once I filled it. Then I went away and left the lights on and the charger off.
- With the batteries down and then the engine running, I took the measurements on both the leads coming from the alternator and the charger. They were both putting out about 40 amps. The alternator about 45 and the charger about 35. The total measured going to the house bank lead was 80.
- What I don't know is how it will behave with uncompromised batteries. I suspect that if I run the new ones down to 50% and then turn the charger on and run the alternator, they will peak at close to the 80 amps and then quickly taper off. If it tapers off to 40 amps pretty quickly, I should be OK. Hopefully the alternator will be something less than 40 amps by itself.
- I'll probably dial down the charger to put out something like 30 amps max. It will slow down my charge time, but I'm in South Florida and the generator gets used quite a bit for the ac.
- The Trojan 6v AGMs list the suggested charging rate as .2C which for the 225 AH. So the 12v at 40 amps should be right for the 2 6v batteries in series.
- I'll update this and let you know once I get the new batteries.

 

[OldDan1943]

Please correct me if I am wrong. As I understand it, alternators do not bring the battery up to 100% The output of the alternator's output decreases as it approaches 100%. To do the final percentage, you need a trickle charge such as solar panels or wind generators. This is assuming you are not using anything from the battery, aka dead/dark boat.

 

[SteveK]

There is many references to not expect the last 15% to be charged from an alternator. Have not found the reason for it. Many have gone to 100, 150 amp alternators as a way I suppose to overcome that issue. And then I read that 3 or more stage charging is needed to get 100% charge.

I have 3 stage charger on shore connection. So I wanted to see what happens if I turn off float. Two days later all batteries are holding at 12.6 /12.7. The house does have a fridge running which has not yet affected it.
Fully charged battery is 12.6 or higher. I must remember to check this after a trip without shore charger, see where the house batteries are at after an alternator charge.