Changing House Bank Battery Types

[firehoser75]

Hi Steve,
A "regular internally regulated" (car/light truck) alternator that is stock on many boat engine installations will not adequately recharge a house bank. Just saying, that is what I had on both my boats with battery monitors so I was able to monitor how my batteries were doing, and it (the alternator) 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.
Flooded lead acid batteries have a charge acceptance rate that diminishes greatly after about the 85-90% point of charge. To "put back in" the last 10% or so, takes a long time NO MATTER HOW LARGE A CHARGING SOURCE as at this point, the battery(s) is determining how much charge (amps) they will accept. Picture the hole in the bottom of the funnel getting smaller and smaller (for liquids). Not only is this a fact of life with these and many other battery types, but I have carefully observed the drop in charge rate on my battery monitors as the batteries get closer to 100%, no matter the charge source (alternator, shore power, generator, or solar).

Also, many (most) stock alternator setups on production boats, come with internally regulated alternators that not only are only designed for very short bursts of higher charge output but are wired to react (sense) the start battery. They are setup to ensure that the start battery will receive a full recharge which only requires a small charge rate as the battery is never really depleted like the house bank. So, normally after a relatively short time, the alternator will down rate it's charge output to match the requirements of the start battery (that is mostly already fully charged). In this way, the house bank will receive only a very small amount of charging. If this type of alternator were to be setup to charge a larger (depleted) house battery bank and run at full (or a much higher than what is "normal" output), it would overheat, again not being designed to adequately cool under these types of prolonged large loads. The output of this type of alternator can be improved (during the "bulk" stage) by having it modified to an external regulator (3 or more stage) with temperature compensation so as not to overheat it (fry it), but in most cases, the setup (wiring) will need to be changed to directly charge the house bank. I did this on my first boat with a noticeable improvement, but if a boater is hoping to rely on the alternator as a main charging source, better results can be achieved with "high output" (purpose built) charging alternators (Balmar is one brand) that are externally regulated with both battery and alternator temperature compensation. With that setup when the house bank is depleted, a larger charging rate can be applied and maintained until set point are reached or the battery imposed "tapering" occurs during the final 10% (which can take hours).

 

[SteveK]

Thanks Tom.
When you say you saw it was not fully charged, does that mean the voltage was less than 12.6

 

[firehoser75]

No Steve,

I base it on the battery monitor that reads as a percentage of total charge. (It would also read voltage, amperage in and out, state of charge as a percentage, and state of health). On my (former) sailboat before I installed solar, I might start a morning at 70% charge. After motoring for 4+ hours, my monitor would tell me I had only reached 75% charge (for example). I did not use voltage (alone) , as it is only an estimate of charge, and not as accurate as a properly installed smart battery monitor.
Also, when first started in the AM, my alternator (say rated at 80 amps) would be putting in about 40 amps, but would drop off to about 15-20 amps within a few minutes and stay at that rate of charge. That type of charge rate is only slightly more than the ongoing usage rate, so keeping me, just above "even". When trying to put 200 amp/hr back in, not even thinking about the diminishing charge acceptance rate or the ongoing usage (draw), it would take 10 hours to put the 200 amps back into the battery bank.

It is no wonder that boaters (lots of sailboaters) who rely on stock alternators for recharging, quickly "kill" their batteries. Going marina to marina and using shore power will reduce or eliminate this effect.

 

[SteveK]

Thanks, I have a SOC that shows Ah, volts and amps. Yours shows % which makes it simpler. Have not paid much attention to it before because it is at the lower helm. Must read the manual and start looking at least before and after a run for changes.
P.S. I have not had any issues with house bank, just that since I installed the freezer I am more interested

 

[Hippocampus]

Ran lifeline AGMs for 8 years as a pretty much full time active cruiser. When boat was sold they were load tested and still running 93-7% of initial. Did nothing special beyond reading MaineSails instructions on how to use them. Lifelines can be equalized. Did that once in 8 years. Unless you’re running a planing hull having the extra weight to keep you from ever getting down to 50% soc isn’t a big deal. We rarely got below 80% and that was not having a alternator running but rarely as it was a sailboat. On a trawler would think it’s even less of an issue. Did have solar and wind. On a trawler that’s being used either your genset (when AC is on) or your alternator (when moving) will get you through bulk and most likely absorb. The alt energy will get you that last little bit.
Believe most problems with shorten life with are in boats infrequently used. Shore power gets disconnected or fails or boat is on a mooring. Or boats monitoring system fails to alert owner SOC is down. Other common problem is folks don’t do an adequate energy budget so don’t have enough capacity. With just a modicum of attention think 10y service life from quality AGMs is easily done.
Unless the latest and greatest comes along when my current bank fails will likely use carbon foam firefly. Motivation is all of my batteries are on the starboard side on this boat so need to counter balance them. There’s enough drop in weight going to carbon that won’t be necessary and need to make no other changes.

 

[TBill36]

Tom, Your observations seem to hit on the problem of charging from an internally regulated alternator. If I understand correctly, an alternator output is determined by voltage. And I think a battery's voltage will increase pretty rapidly when being charged, even though it's amp-hrs are not there yet. So the alternator slows the charge rate and then it takes a long time to get there. Is that right?

Also, it seems to me that alternator wiring is usually way undersized. Without looking it up, 90 amps should have something like 2 awg cable for a 4 ft run. The terminals on a 90 amp alternator don't accommodate that and most come with something like 10 awg. What gives with that?

 

[koliver]

TB
I am trying to understand your present setup.
You have only 2 x 100Ah batteries for House use.
You have a constant need for an inverter, drawing up to 8 amps while in use.
You have 2 refrigeration users, combined draw of 10 amps while in use.
You have experienced some battery boiling.
You have no effective recharging of your house batteries from your alternators, as they have a Start battery recharge profile
Your Magnum charger is throttled back to 60 amps and you are considering a further reduction. The magnum has a 3 stage charging profile, suitable for your house bank.
You sometimes leave your boat connected to shore power but with the Magnum charger turned off.
You have lighting loads that are DC 12v, and a suite of nav instruments that also draw 12v

I agree with Tom (Firehoser) about the way the regulation of your alternators works. The first thing I would change would be to get one of the alternators properly regulated on a 3 stage profile, and connected only to the house bank. The other can remain on the Start battery.
The second thing would be to either reduce DC loads to 100 Ah/day maximum or increase the house bank size to adequately manage the present loads. IMO you need twice the capacity you presently have, and that is why your house bank has been troublesome.
Third, I would get in the habit of always leaving the charger turned on when away from the boat.

 

[TBill36]

Keith, you are correct in a lot of assumption except:
- I usually have charging from the inverter from running the generator or when I'm docked. The big draw down I mentioned was a mistake from working on it and leaving the lights on and inverter off.
- occasionally I will conservatively draw the bank down 50% (100 ah of the 200 ah bank), which is followed by 6 to 8 hrs of engine running, then maybe a couple of hrs with refrigeration draw and then the generator for 10 to 12 hrs. Most of the time it's run gen all night, run engines 6hrs, no charging for 3 hrs, then back on the gen. Or its at the dock being a queen with the charger on.
- even though I have internal voltage regulated alternators, I believe they are charging the bank to say 75% during the long engine run time. I'll measure the amps in once I get the new batteries installed, but I'm pretty conservative on my 50% calc as the 10 amp refrigeration draw is really about 1/2 as refrig and freezer only run 1/2 to 1/3 of the time.
- From previous measurements, my boiling is a result of too many amps into the bank at one time - half of which was coming from the alternator.
- I don't have room to add additional batteries without moving them farther away from the inverter which significantly lengthens cables and adds potential losses. If I continue to have problems, I may have to do this and since my inverted draw is low, I might be able to get away with it. But my highest amps through the cabling is due to charging so I have that to contend with.

 

[ranger58sb]

You sometimes leave your boat connected to shore power but with the Magnum charger turned off.

Third, I would get in the habit of always leaving the charger turned on when away from the boat.

Agree. Why leave a charger off while on shorepower?

Keith, you are correct in a lot of assumption except:
- I usually have charging from the inverter from running the generator or when I'm docked. The big draw down I mentioned was a mistake from working on it and leaving the lights on and inverter off.

But that's confusing. Unless the inverter is an inverter/charger? Or...?

-Chris

 

[RickyD]

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.

+1

 

[TemptUs]

Basics

I’m seeing red flags. I’d like to see how he has this wired before installing any new batteries. Please sketch us a wiring diagram of your 12VDC System. It sounds like one of these batteries is working harder than the other.

 

[contingensea]

Thoughts

Here’s a link to a post I offered back in April 2021 concerning battery chemistry changes and challenges that you may find helpful.

https://www.trawlerforum.com/forums/showpost.php?p=1000823&postcount=18

I do not pretend to be an expert on the subject. I’ve been educating myself on the topic of energy storage and maintenance in preparation of making changes on my trawler.

A couple of items come to mind given what you have described.
1. Boil over, this can sometimes be due to a higher bulk charge rate than the battery is designed for. The charge rate should be confirmed with the manufacturer. FLA’s typically want 25% max of their 20ah rating. 25% of 100ah bat = 25 amp max bulk charge rate.
2. ACR’s only switch the charging electrical path. Using an ACR attached to different battery chemistries with different charging profiles is not advisable.

Spend some time reading the materials from the links provided in my post from April 21. I wouldn’t want to see you move from one set of problems today to another set after making changes.

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.

 

[Phase3]

Hi Bill
We have just made the shift to lithium and definitely don't regret it one bit. Our situation is different though; we anchor a lot and have one 300 watt solar panel. No generator. Single engine with a Delco 19si alternator with external Wakespeed regulator. Everything works as it should, especially in the cloudy/rainy shoulder season.
However, I think if I were in your position having a generator, I would look into an AGM Carbon setup. Yes, more costly than normal AGM, but less costly than Lithium.
Victron has had good reviews on their AGM Carbon batteries.
Hopefully, I am not repeating what has already been said.
Good luck

Brent

 

[Phase3]

Bill
Attached is the data sheet for you on the Victron Carbon batteries for reference.

 

[ReedStr]

Hopefully this helps

Let’s see if I can ad something to this conversation. First, some facts.

• Lead acid batteries need about 14.2v to fully charge. If charged at less that 14v they will never fully charge. If charged at more than 14.4v they will off gas hydrogen and lose fluid from their electrolytes
• Lead acid batteries can be charged up to 1C at 14.2v or less until 80% soc without off gassing. However lead acid manufacturers typically recommend charging at .3C or preferably less while agm manufacturers typically recommend charging at at least .3C and preferably more.
• Once charged, a lead acid battery will maintain it’s SOC if subjected to a float voltage of 13.6v. If a float voltage is not applied they will gradually lose charge. If a voltage of 14v or higher is maintained they will off gas.
• A damaged or old battery has a C much less than original so the acceptable charge rate decreases with age and decreases dramatically with damage.
• it typically takes about 8 hours after a battery has reached 80%SOC to fully charge.
• Internally regulated alternators measure voltage at the alternator. But the voltage that affects the battery is at the terminal.
• Internally regulated alternators charge at their maximum amps until the target voltage is reached at which point the amperage is decreased to maintain a constantly voltage indefinitely. Alternators with internal regulators never drop to a float voltage.
• Most internal regulated alternators are set to 13.6v although they range from 13.5 v 15v which will not fully charge lead batteries because the voltage is too low. Note that if it’s set for 15v it will boil your batteries because internal regulators do not Drop to a float voltage.
• Most inverters are set to charge batteries in their absorption phase at 14.2v for 4 hours at which point they drop to a float voltage of 13.6v which will not fully charge lead acid batteries because the time is too short.
• The longer lead acid batteries sit without being fully charged the more their current SOC becomes their actual capacity. This can be partially reversed by an equalization charge which few people do.

​

From this set of facts we can see a couple of things:

• Assuming you regulator is outputting 14.2v or less at the battery bank and the same for the charging output of your inverter you should be able to charge your 200ah bank at at least 65amps and agm batteries up to 200amps.
• We need to know the voltage at the batteries when your engine is running at cruising rpms and your alternator is putting out significantly less than the rated output. And we need to know the same thing for your inverter when it is charging. If it’s more than 14.4v then that’s why your batteries are boiling. If it’s less than 14v then that’s why your batteries never get fully charged. As long as you are not exceeding the maximum CAR as recommended by the manufacturer (and the battery is not damaged) It’s not amps that boil batteries it’s volts. The caveat here is that if you are running long periods, say 16 hours, and your internally regulated alternator is set to greater than 13.8v then that will boil your batteries and damage them.
• Once your batteries ran dry then it is quite possible that the charging capacity of your alternator or inverter is greater than what the battery can absorb without further off gassing and damage.
• If the system is working well, i.e. charging at max amps until 14.2v is reached and then decreasing amperage to maintain 14.2v, then only when you run the engine for substantially more than 8 hours will your batteries ever get fully charged. Most people rarely if ever run their boats that long so the rule of thumb is that lead acid batteries are never fully charged when away from the dock.
• When at the doc, since most people’s inverters have too short an absorption phase to fully charge their batteries, battery capacity diminishes over time and this increases the risk that your charging capacity is too high relative to the size of your battery bank and will thus cause off gassing, battery damage, and a further decrease in capacity

​

.
If you decide to switch to lithiums then the usage and charge profiles are completely different from lead acid. Lead acid likes to be stored fully charged on a float voltage. Lithium’s will be destroyed by storing them fully charged on a float voltage. Lead acid takes 8 hours of gradually decreasing CAR to go from 80% charged to fully charged. Lithiums go from accepting maximum charger output to full in 2 minutes although sometimes you leave them for another hour to equalize. In both cases most of us never thought very much about our battery systems until something went wrong and then we find out that diagnosing, fixing, or changing our system is far more complicated than we thought.

 

[TBill36]

Thanks for the responses. Contigensea and ReedSTR - great info. I'll get back with some data, once I get the new batteries installed. It will be a few weeks as I'm going out of town for a while at the end of this week. ReedSTR, I think you might have the answer I'm looking for, I just need to run it and find out. Great info - thanks.
I'll also try to sketch up a schematic of my system as suggested and post it.

 

[Capt Dan]

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…

If you don’t know that paralleled batteries maintain the same voltage, then you don’t know enuf about electricity to be dabbling in Lithium. There is a lot to it.

Besides the fact that an internally regulated alternator is ancient history. Poorly treated batteries, no matter the composition, will fail prematurely.

But you are getting a lot of good advice here.

Do your homework. Lithium is not a drop in replacement solution.

For those that are lusting for Firefly carbon foam, you might want to take note that Ben Ellison, (Panbo) had his Fireflys fail in I think two years. Just saying.

Still looking for mis-spelled words.

 

[TBill36]

Capt Dan, thanks for pointing that out in such a pleasant manner. I certainly know the difference in series and parallel, just made a mistake in my description. But if you're really going to scold someone you should learn how to spell first. Enough said!

 

[OldDan1943]

I am not an expert on anything. That being said, install AGm batteries. They may not be the best but they are a drop-in.
Nothing fancy but, they do work without a lot of maintenance

 

[SteveK]

@ Reedstr
Your post 45 in Bullitt form suggests it is a fact, is it your opinion or is it fact. Sounds good just curious.
Your post is like many, but there is also a common denominator. There is no specific answer to "What is fully charged". There is undercharge leading to memory and lower SOC, there is overcharge boiling batteries ruining battery life.
What is a perfect fully charge and how do you measure it to know it.

 

[TBill36]

Attached is a schematic of my battery and inverter/charger system if I figured out how to attach something on this site. There is an additional cut out switch on the inverter positive lead and a 160 amp fuse. There is also a large (can't remember size) fuse on the alternator lead prior to it terminating at the master cut off switch. The master switch does not cut off either the alternator or inverter leads from the batteries. The batteries are oriented with length perpendicular to boat centerline as shown in the look down view of the battery top. The cables are all 1/0 or bigger. This is a parallel set up as they are 12v. When I go to 6v, they will be wired in series.

 

[Simi 60]

Interesting discussion touched on with a cruiser/boatbuilder/ electrically smart mate yesterday afternoon when talking about alts to charge the LFP bank and why I don't have one on the big motor (hint- due to excessive cost of balmar)

His suggestion, why not a 240v alt wired straight into the Victron multiplus.
Reckons a 3kw one can be had cheap and the interwebs suggest same


Anyone gone down this path?

 

[Simi 60]

This one unfortunately in England on ebay but Australian made Dunlite
3kva
240v
$150 (2nd hand)

https://www.ebay.com.au/itm/Dunlite...8-15cd-42b1-a72c-cf72e62de090&redirect=mobile

 

[ReedStr]

Well, mostly it’s information i found on battery university that once understood made it easier for me to understand what’s going on with my batteries. For what it’s worth lead acid batteries are considered fully charged when their CAR at 14.2v drops to 3 to 5% of their ah capacity so in his case with 200ah capacity they are fully charged when they accept 6 to 10 amps at 14.2v.

 

[Mako]

Simi that alternator doesn't appear to have a regulator, so is it a constant speed?

 

[twistedtree]

Simi that alternator doesn't appear to have a regulator, so is it a constant speed?

That's intended as a constant speed alternator as would be used in a genset. That particular one is for 240V 50hz when being turned at 3000 rpm. That's how you would need to run it if you wanted to feed its output into the AC input of an inverter charger, as you would the output of a genset.


The hangup is the need for a constant 3000 rpm, and that's not how a typical propulsion engine runs. Now I suppose you could use an appropriate pulley or gear step-up such that at your preferred cruise engine rpm, the alternator was running at 3000 rpm. At that speed, the output would pass the inverter's test for voltage and frequency, the inverter would switch to the alternator input, power the loads, and start charging batteries. For a boat that spends a lot of time at a specific RPM, it's actually a pretty interesting idea. But you would only get usable output at that particular engine RPM. Run faster or slower and the output would drop out of spec and the inverter would disconnect.


The advantage over a conventional alternator that rectifies it's AC output to DC and then regulates at battery voltage is that the higher voltage alternator would generally be more efficient. But then the higher voltage AC would run through the inverter/charger and get converted to DC for battery charging, so you pick up some losses there. It would take a pretty careful analysis to figure out which is actually better, and by how much.


The down side is that you would need to do a bunch of engineering to figure out the loading and sizing of a pulley or gear system for the speed step-up (assumes you don't want to run your engine at 3000 rpm, and 3600 rpm for 60hz power). Depending on your engine rpm range, a 4 pole alternator might be better since it would put out 50hz or 60hz at 1500 or 1800 rpm respectively. And then when you are done you have a very custom batch of hardware that will be all yours to maintain, diagnose, and fix.

 

[Simi 60]

.


The hangup is the need for a constant 3000 rpm, and that's not how a typical propulsion engine runs. Now I suppose you could use an appropriate pulley or gear step-up such that at your preferred cruise engine rpm, the alternator was running at 3000 rpm. At that speed, the output would pass the inverter's test for voltage and frequency, the inverter would switch to the alternator input, power the loads, and start charging batteries. For a boat that spends a lot of time at a specific RPM, it's actually a pretty interesting idea. But you would only get usable output at that particular engine RPM. Run faster or slower and the output would drop out of spec and the inverter would disconnect.

That was the thought

We run a constant 1150rpm when cruising
And using a pulley calculator would tell you pulley size needed.
https://www.blocklayer.com/pulley-belteng.aspx
(For example if engine pulley is 8 inch a 3.08 on gen gets 3000rpm)
Add: quick look, our engine pulley is approx 9.5 inches, gen pulley would be 3.64 approx

A simple 240v light coming on at helm will tell you when it's producing power, adjust RPM accordingly.

The advantage over a conventional alternator that rectifies it's AC output to DC and then regulates at battery voltage is that the higher voltage alternator would generally be more efficient. But then the higher voltage AC would run through the inverter/charger and get converted to DC for battery charging, so you pick up some losses there. It would take a pretty careful analysis to figure out which is actually better, and by how much.

Additional advantage over here at least is this type of setup will cost significantly less than the balmar, Wakefield type of alt.

 

[TBill36]

I promised to follow up once I got some AGM batteries installed. I ordered Trojan T105 AGMs, but they came in about 6 weeks after I ordered them with the wrong terminals and they would not give me a date for being able to deliver with the correct ones. So I'm going to pick up what's locally available from Batteries Plus. My choice is between Crown - Season All 6V AGM that states 220AH @ 20 hrs that weighs 66lbs, or Magna Power with 190 AH @ 20 hrs that weighs 70lbs. I've always thought the easiest way to assess LA batteries was by weight. Crown used to be top of the line, don't know about Magna Power. The Magnas are $30 more which I don't mind spending if they are better. Spec stays they are not, but weight says they are. Anyone have experience with either of these two and recommendations on which to buy.

 

[Gdavid]

I promised to follow up once I got some AGM batteries installed. I ordered Trojan T105 AGMs, but they came in about 6 weeks after I ordered them with the wrong terminals and they would not give me a date for being able to deliver with the correct ones. So I'm going to pick up what's locally available from Batteries Plus. My choice is between Crown - Season All 6V AGM that states 220AH @ 20 hrs that weighs 66lbs, or Magna Power with 190 AH @ 20 hrs that weighs 70lbs. I've always thought the easiest way to assess LA batteries was by weight. Crown used to be top of the line, don't know about Magna Power. The Magnas are $30 more which I don't mind spending if they are better. Spec stays they are not, but weight says they are. Anyone have experience with either of these two and recommendations on which to buy.

I can't speak to the batteries you are considering but I can say that I was pleased with my experience of buying through my local Batteries Plus last year, supply chain delays were probably at their peak at the time but the communication and timeliness of getting the batteries through them impressed me. I have a simple and modest system and went with 4 Duracell Group 31's for a nominal total capacity of 420 AH, i don't have enough time on them to speak their long term performance.

 

[TBill36]

Data I promised - think I found an over-active alternator. I finally got the Crown all-season 6Vs AGMs installed and it sat for a couple of weeks on the inverter/charger that the monitor showed float 13.4V and 0 amps. A VM across the terminals read 13.63 and an amp meter measured 0 amps through the positive battery cable. I plugged in a fan that drew 4.4 amps and left it on for 17 hrs. The VM across the batteries read 12.65v immediately after turning on the fan.

After the 17 hrs, I measured 4.4 amps leaving the battery and the VM read 12.21 across the batteries which increased to 12.37 after turning the fan off.

Then turned on the inverter/charger and saw 12.86v at terminals and a 29 amp bulk charge reading on inverter which diminished to 18 amps after a few minutes that was confirmed with my amp meter. I then cranked up the engine and set it to 1000 rpm and measured 87 amps going into the battery. I then shut off the inverter/charger and measured 58 amps going into the battery. Turning the inverter/charger back on it increased to 87 amps again. I didn't want to run very long with that condition as it is way over the desired C rating for 220 amp hrs of batteries.

So now I have to figure out how to get my 90 amp alternator to quit over charging. It is a Leece-Neville internally regulated alternator. Maybe have to go with an external regulator, although, I would think having high output alternators that don't cook batteries without external regulators are pretty common. Also, it is not sensing the output from the charger and just adds to whatever it's putting out.

Anyone got info on where to proceed from here. I'd like to keep the 90 amp capability so when I'm running everything on the boat it will be big enough and still have some capacity to charge the batteries, but don't want to cook the batteries.