Battery charger redesign

[AlexLbk]

Hello everyone.
The purpose of this post is two-fold:
1. Document what I have done.
2. Solicit feedback if any.

I own a 2018 Bavaria E40. Love the boat, but when moving her up the east coast two years ago I was forced to run the generator almost continuously to keep the house batteries topped off. The vessel has 4 banks of batteries:
1. House (3X140AH AGM)
2. Stern thruster (95ah AGM)
3. Bow thruster (95ah AGM)
4. Engine battery
The house batteries get used quite a bit between all the electronics, 4 refrigerators, all the network and computer equipment on board so they get to about 50% charge after 6-8 hours at sea.
The shore charging system consisted of a single 40A Cristec charger that can charged batteries through Quick charge separators through shore power or generator. The alternator kept the engine battery topped off, but that's about it.
My goals were:
1. To improve speed and quality of charging while connected to shore power or through the generator.
2. Allow the alternator to charge the batteries while underway.
3. Provide an ability to upgrade to lithium house bank in a year or two without rewiring half the boat.

AC charging was first. I added a 3000W Xantrex inverter charger and dedicated it to the house bank. I didn't really need the inverter, but this was the only way to get 150A charge current out of the charger.
I then rewired Cristec to the 3 remaining banks.

Alternator was more of an issue. The stock Volvo alternator on the D4 is capable of outputting 115A, but it doesn't do that in the stock configuration. My initial thought was to upgrade the alternator with the likes of Balmar. However this engine is electronic and Balmar could not definitively explain how they will interface with the engine. Not wanting to risk EVC alarms, I moved on. I found an external controller from Nordkyndesign, got it setup, but while the voltage on the atteries went up, the current on shunts showed almost nothing. After tracing the whole negative bus I figured out that the yard upgraded the positive wire from the alternator and ran it to charge separators, but left the thin factory negative wire running to the starter solenoid. I left the factory wire as is and added a 1/0 wire from the alternator to the negative bus bar, which immediately brought up the current values out of the alternator, I reconnected the shunt and tested charge parameters. Everything looked good on house batteries, but thruster and engine batteries were getting overcharged - more rewiring.
I added a victron DC-DC converter hanging off one of the charge separators and wired the output to another charge separator. Since the charger can only handle 30A, the charge parameters looked a lot better.
So the wire from the alternator goes to the charge separator input, output 1 goes to house batteries, output 2 to DC-DC converter. Converter output go to another charge separator that splits output between thruster and engine batteries.
This setup should also handle LiPO4 batteries once I'm ready to swap. The AC chargers are separate, so I can have different charging profiles between AGM and LiPO4 while on shore power and generator. While underway, the alternator controller will charge with a LiPO4 profile that would then be converter to AGM with DC-DC converter. If BMS decides the disconnect the lithium bank, the AGM batteries will still be in the circuit and alternator won't be running without load.

 

[julians]

It doesnt sound right that you had to run the generator in addition to the engines when cruising in order to keep all the batteries fully charged - sounds like you had a fault in the original system somewhere.

 

[jrudge]

Agree with Julian. The house bank also seems small for 4 x fridges and not sure what the “ computer equipment “ is.

 

[Portofino]

Test the pair of house batts , there ability to hold charge .
Thinking they are knackered.It doesn’t take much a few deep long dischargers to significantly reduce there holding capacity.
Yes I hear they were new .But duff old ish batts are around in the system .Seen this on car forums .Guy has all the symptoms of duff batts + say 5/6 yrs old .Gets a new one fitted supposed to fix all , but only makes a small difference.Gets it tested a s finds the new is a duffer so gets a another ( under guarantee etc ) = all issues resolved.

Aside the 140 pair as mentioned ^ seems a bit small for the fridges .
You can have the load of the fridges tested too and the output of the charger .

It feels to me you have thrown parts expensive techy solutions on this without a diagnosis first .

Perhaps all it needed was a new , bigger batts say a pair of 190 Ah ?
Its hard to tell from an armchair TBH .

The 115 Ah alternator should be able to power up everything + charge up all the banks when running .

 

[julians]

The 115 Ah alternator should be able to power up everything + charge up all the banks when running .

The boat presumably has two engines, so 2 x 115 amps = 230 amps of charging power. If that couldnt supply enough amps to charge all batteries even when all the electrics on board were being run, then there was a fault!

 

[Portofino]

As an aside when I got my boat a big step up in electrotwackery I paid a boat electrician to give it going over .

Symptoms .
1-One of the two fridges would work intermittently.
2- Occasionally no pattern could be in a marina after a night on shore power or @ anchor the main engines MAN 13 L s would turn slowly or even need the cross over switch to fire .
3-One morning the interior lights were dim ish in the berth on shore power + charger on etc .

Where do you start ?

Well this what he found .
1- one fridges 24/220 controller had bust and it only used 24 v ie the dom batts 24/7 .Hence @ anchor it warmed up as the V dropped below a certain level say 12.6 it auto switches off ….that part worked .

2- The OEM std 40 Ah charger was 14 y old and it’s max output was a mere 4 A h .Yes they don’t die suddenly apparently they just decay away .Decrease output until below or marginally capable to cope supplying juice to the banks .
So occasionally I needed the cross over switch to turn them over fast enough to fire them up .

3- As 2 .

The batts we’re new ish and tested ok .A pair of 190 Ah for the doms and starter set .[ he fitted a temp 100 Ah charger overnight and came back to really test them ]

The bowthruster being a 24 v boat uses one of the sets in the ER not sure which tbh .
The geny has its own 50ah starter and dedicated charger .

Solutions .
New cockpit fridge with a working 24/220 controller which goes for the 220 v if it sensors it first .Be it shore or geny .
New charger a modern smart one , you know with 5/6 cycles , programming it to each bank individually.
It a 80 A h ( up from the OEM 40 Ah ) .

End of issues .

In the past 7 / 8 seasons have replaced both banks conventional gel mat maintenance free .
The doms went first.

Additionally and fortunately have charging current gauge and importantly discharging current gauges for each bank measured in Ah s .
So,I can see what’s coming out and what goes in .Yes you can see the stages of the charger , the bulk the float etc .

Further more for I think my own piece of mind intend to run the geny evey 4 hrs at a to top off the domestic batts .
They absorb initially 40 Ah from a 80Ah charger stuffing into a 2x190 Ah bank .
The starter bank never moves as the run out tops them off .The alternator s are 55 Ah each .

If after say 4/5 hrs at anchor ( 2x fridges constantly being opened , toilets , the dash gear , the shower pump etc ) i don't run the the geny . I see a 40/50;a discharge on the gauges of the house / doms .A 40 min run back to the marina ( bear in mind the 2x55 Ah alternator s ) normally almost but not quite tops them off .When back the gauge say reads about 5 Ah short of the 2x190 .
Shore power + charger soon finishes them off .

I,am on my boat now in the marina typing this staring at the gauges .All on zero discharge and 32 volts both banks .The charger is floating them both .

Just one more thing when you say you ran your boat with the geny + charger simultaneously on with the main engine (s) to keep topped up ? I was of the understanding you shouldn’t.
It confuses the alternator and the “smartness “ of the charger possibly knackering something in one or the other .
Well the boat sparky advised me to never do it .= run the motors and the charger from the geny together.

Sure I run the main motors and geny occasionally……but only the Aircon or cabin sockets or kettle etc , never the charger as well .
No sure if this is generic or just a nuance of my particular set up .

It feels to me running both charging circuits is gonna throw one or the other out .Others might want to share there experiences ?

 

[Portofino]

Another thing , that cockpit fridge of mine that lost its 220/24 switch control and only worked on the 24 hence batts , sucked far too much juice than its spec .
Corroded contacts sea air under the helm seat took its toll .So it was robbing the house batts sucking them dry .
This was over and above its sticker consumption, it was faulty and increased its consumption as well .

The boat sparky measured the draw on everything.

 

[vas]

agree with all posters above.
house bank is silly small!

for reference: 43ft mobo, lots of electronics, two 80lt fridges (that count for 3 as the one still has a v.inefficient cooling and runs almost 80% of the time), 3kw multiplus inverter, all other normal stuff on, 2laptops 24/7 (almost!) and 600W solar on the hard top in the Med.
up to last year service bank was struggling with 4X6V T105RE (225Ah@24V) and every couple of days had to start the generator.
this year added a 8S 304Ah LiFePO4 bank in parallel, all issues gone. Now for the fifth day on anchor (2days crappy rainy weather) bank was at 52% in the morning will be close to 75-80 by sunset.

Closing, from 6:00pm till 8:00am that solar don't cover the needs and battery is used, I've got 70-80Ah@24V (or 160Ah@12V for comparison)
If your consumptions are anywhere close (wont be as un north you dont have fridges taxed as much as down here with 30-35ambient in the cabin) it's obvious that service bank is way too small. Mind my Lifepo4 are happy working from 15-95%, your AGMs are only happy from 50/55-100%. Get the respective usable Ah and you know what to do.

cheers

V.

 

[Tranona]

Another for too small house bank. Extra charging capacity won't help - you already have mire than enough. The thruster batteries do not need charging much as they are only used for short periods when the engine is running. Batteries will only take what they can absorb and the maximum your 190Ah bank will take is maybe 40 amps unless massively discharged. when you are motoring the alternator will keep up with your domestic consumption and have enough left over to feed what the batteries will take. SAs soon as the engines stop all loads go onto the batteries.

The starting point for working out battery capacity and charging is a usage audit - how much you are taking out in a period between charges, then double that to give you basic capacity. I also had a Bavaria of similar age, but a sailboat with the same batteries - but 5 of them, one for engine start, one for bow thruster and windlass and 3 for house - 50% more for a boat with a fraction of your usage. That gave me less than 2 days between charging keeping within 50%. Never saw more than 35A going in (same alternator) from 50% discharged.

Your boat was set up for day use - short sharp blasts followed by long periods of charging from shorepower and use of generator when not motoring or on shorepower. As you have found, you use your house bank in a matter of hours. So, first thing if you want to reduce the amount of generator time, increase the house bank - you could double it easily within your engine alternator capacity. Your mains capacity is the standard Bavaria for up to 300Ah capacity but your new 150A charger is a waste of time because you don't have a big enough bank to absorb that amount. Look at the charging profile of the Exides and you will see that they take 15-20% when below 50% discharge, but quickly fall away as they get near fully charged. My bank used to take anything up to a day with no draw to get to float after a weekend away.

Lithium may not be the way to go for your pattern of usage. They really only work for heavy users like liveaboards, and even then only if space is a problem. The cost of doing it properly makes it simply uneconomic for leisure users as there is not enough usage to benefit from the greater number of cycles it offers. A simple calculation AGMs have expected cycles of between 500-1000, so more than 10 years of, say, 50 days usage a year if you size to keep above 50% discharge. Lithium at typically twice the price for a given capacity (ignoring capital cost of installation) will give you potentially above 2000 cycles - 40 years! You can achieve what you want by increasing the size of your bank with more of the same batteries. You already have more than enough charging capacity.

 

[petem]

I'm intrigued as to what electronics / computer equipment you have running that is using so much power.

Bitcoin mining?!

 

[BruceK]

Slightly off topic but my batteries must be able to last the full term that I can take the boat out for. That restriction is my water supply which currently for a family of 4 will last 5 days with some economy. (1 shower per day per person, dishes and laundary). I can only achieve that from my batteries with solar power (no genny) and a large house bank of 600Ahr. (4 x tv / 4 laptop, nav, vacuum pump, and fridge and freezer plus lighting on 12v and a 2000W inverter used judicously for microwave. ) I am itching to convert to LifePO4 5000Ahr and run some serious inverters but we are back to serious genny money so waiting for costs to come down. Coming back to port to top up with water is bearable. To do so to recharge batteries seems an anethma to me.

 

[AlexLbk]

It doesnt sound right that you had to run the generator in addition to the engines when cruising in order to keep all the batteries fully charged - sounds like you had a fault in the original system somewhere.

The engine usually runs at 1750RPM and alternator without the controller output less than 10A at a continuous 14.3V. So at see, I was 15-20A negative draw on the shunt. If i use the inverter the draw goes up to 1500A for the duration of usage. So 10A over 6 batteries is really not much.

 

[AlexLbk]

I'm intrigued as to what electronics / computer equipment you have running that is using so much power.

Bitcoin mining?!

Nothing too sophisticated, 2 MFDs, AIS, heading sensor, router, a couple of POE switches, a server that logs and analizes and graphs all data on the boat, cameras, temp sensors for fridges, weather station, ultrasonic tank monitors, forward looking sonar, radar. Might be a few more things that I'm forgetting.

 

[AlexLbk]

The boat presumably has two engines, so 2 x 115 amps = 230 amps of charging power. If that couldnt supply enough amps to charge all batteries even when all the electrics on board were being run, then there was a fault!

The boat has one engine - a D4-300.

 

[Tranona]

The engine usually runs at 1750RPM and alternator without the controller output less than 10A at a continuous 14.3V. So at see, I was 15-20A negative draw on the shunt. If i use the inverter the draw goes up to 1500A for the duration of usage. So 10A over 6 batteries is really not much.

The low output is not because the alternator is not capable of producing more - it is already matching all your loads, but because that is all your tiny bank (by comparison) can absorb at their state of charge. The shunt is measuring the NET flow from the charging source not the total. You would need to measure that at the alternator.

See post#9. You need to work through that process to understand what you need to do - and at present upping charging capacity is not the way to go. Think of the battery as a fuel tank and the alternator as a hose - with the inlet to the tank a valve that gets smaller as the battery gets more fully charged. If you increase the size of your bank the "valve" increases in size when the engine is running and increases the "buffer" to power your electrics when the engine is not running.

As a test turn on your usual things and see the size of the -ve flow on your monitor - this is what the alternator is outputting in addition to charging the battery - the splitter ensures that the battery gets charged first. It is useful to think of the batteries as someone at a buffet - they take what they want from the table, not what the table has on it!

Your one engine/alternator should be enough, but would guess that you are consuming 50A+ and you may well find that if you increase the capacity (therefore increasing the acceptance) and run the batteries down the alternator might struggle to keep up with all your consumption, but you are nowhere near that yet.

 

[AlexLbk]

Another for too small house bank. Extra charging capacity won't help - you already have mire than enough. The thruster batteries do not need charging much as they are only used for short periods when the engine is running. Batteries will only take what they can absorb and the maximum your 190Ah bank will take is maybe 40 amps unless massively discharged. when you are motoring the alternator will keep up with your domestic consumption and have enough left over to feed what the batteries will take. SAs soon as the engines stop all loads go onto the batteries.

The starting point for working out battery capacity and charging is a usage audit - how much you are taking out in a period between charges, then double that to give you basic capacity. I also had a Bavaria of similar age, but a sailboat with the same batteries - but 5 of them, one for engine start, one for bow thruster and windlass and 3 for house - 50% more for a boat with a fraction of your usage. That gave me less than 2 days between charging keeping within 50%. Never saw more than 35A going in (same alternator) from 50% discharged.

Your boat was set up for day use - short sharp blasts followed by long periods of charging from shorepower and use of generator when not motoring or on shorepower. As you have found, you use your house bank in a matter of hours. So, first thing if you want to reduce the amount of generator time, increase the house bank - you could double it easily within your engine alternator capacity. Your mains capacity is the standard Bavaria for up to 300Ah capacity but your new 150A charger is a waste of time because you don't have a big enough bank to absorb that amount. Look at the charging profile of the Exides and you will see that they take 15-20% when below 50% discharge, but quickly fall away as they get near fully charged. My bank used to take anything up to a day with no draw to get to float after a weekend away.

Lithium may not be the way to go for your pattern of usage. They really only work for heavy users like liveaboards, and even then only if space is a problem. The cost of doing it properly makes it simply uneconomic for leisure users as there is not enough usage to benefit from the greater number of cycles it offers. A simple calculation AGMs have expected cycles of between 500-1000, so more than 10 years of, say, 50 days usage a year if you size to keep above 50% discharge. Lithium at typically twice the price for a given capacity (ignoring capital cost of installation) will give you potentially above 2000 cycles - 40 years! You can achieve what you want by increasing the size of your bank with more of the same batteries. You already have more than enough charging capacity.

Thanks for the insight. Before the changes, the house shunt showed negative 25-30A with the engine idling, it then settled down to -15A when running at 1750RPM. Now the shunt shows +20A at engine start, then settles down to +5-8A at runtime. My boat actually has 6 batteries (3 house, 2 thusters, 1 engine - so quote similar to yours). I haven't tried my normal trip yet - 10-12 hours like I usually do, but in the past I got to about 60% after motoring the whole day. The 150A charger was purchased for the lithium, but for now I was more was interested in the speed at while the batteries charged and 40A for 6 batteries was woefully insufficient. The xantrex also has a NMEA interface so I can watch and log it and interface with it. The space is a problem for me. The batteries are in the engine room and it's a tight fit, so there is not way to grow the existing bank size with AGM - they simply don't fit. Money is definitely a consideration, 1-2K really won't change anything in my life.

 

[AlexLbk]

The low output is not because the alternator is not capable of producing more - it is already matching all your loads, but because that is all your tiny bank (by comparison) can absorb at their state of charge. The shunt is measuring the NET flow from the charging source not the total. You would need to measure that at the alternator.

See post#9. You need to work through that process to understand what you need to do - and at present upping charging capacity is not the way to go. Think of the battery as a fuel tank and the alternator as a hose - with the inlet to the tank a valve that gets smaller as the battery gets more fully charged. If you increase the size of your bank the "valve" increases in size when the engine is running and increases the "buffer" to power your electrics when the engine is not running.

As a test turn on your usual things and see the size of the -ve flow on your monitor - this is what the alternatoe is outputting in addition to charging the battery - the splitter ensures that the battery gets charged first. It is useful to think of the batteries as someone at a buffet - they take what they want from the table, not what the table has on it!

Hence the thought of lithium. I have no space to grow the existing battery bank using AGM. I will take her out for a day this week, then a 2 week trip coming up soon, so I can judge where the batteries are.

 

[Tranona]

Thanks for the insight. Before the changes, the house shunt showed negative 25-30A with the engine idling, it then settled down to -15A when running at 1750RPM. Now the shunt shows +20A at engine start, then settles down to +5-8A at runtime. My boat actually has 6 batteries (3 house, 2 thusters, 1 engine - so quote similar to yours). I haven't tried my normal trip yet - 10-12 hours like I usually do, but in the past I got to about 60% after motoring the whole day. The 150A charger was purchased for the lithium, but for now I was more was interested in the speed at while the batteries charged and 40A for 6 batteries was woefully insufficient. The xantrex also has a NMEA interface so I can watch and log it and interface with it. The space is a problem for me. The batteries are in the engine room and it's a tight fit, so there is not way to grow the existing bank size with AGM - they simply don't fit. Money is definitely a consideration, 1-2K really won't change anything in my life.

The alternator is not charging 6 batteries - just 3. The engine start, thruster batteries do not need charging as they only use a few amps at a time and they get priority so are charged within minutes of startup. The alternator is correctly sized as is the original mains charger. Your "problem" is your high consumption, so extra capacity is the answer if you want to consume at your current rate. space considerations do lead to lithium, but a bank that size (300Ah+ compared with your current usable 150) is a big investment in both batteries and systems to use them properly.

 

[vas]

if you go lifepo4, don't put them in the e/r for sure, they need to be cool!
btw, your NMEA/plotter/AIS/router/et al is similar to what I curry/run

 

[AlexLbk]

Test the pair of house batts , there ability to hold charge .
Thinking they are knackered.It doesn’t take much a few deep long dischargers to significantly reduce there holding capacity.
Yes I hear they were new .But duff old ish batts are around in the system .Seen this on car forums .Guy has all the symptoms of duff batts + say 5/6 yrs old .Gets a new one fitted supposed to fix all , but only makes a small difference.Gets it tested a s finds the new is a duffer so gets a another ( under guarantee etc ) = all issues resolved.

Aside the 140 pair as mentioned ^ seems a bit small for the fridges .
You can have the load of the fridges tested too and the output of the charger .

It feels to me you have thrown parts expensive techy solutions on this without a diagnosis first .

Perhaps all it needed was a new , bigger batts say a pair of 190 Ah ?
Its hard to tell from an armchair TBH .

The 115 Ah alternator should be able to power up everything + charge up all the banks when running .

I have 3 140Aah batteries. They were tested both using the carbon pile tester and by discharging at C20 rate. They definitely do not have full capacity anymore, but based on tests they hold 85-90% of the original capacity. They will die eventually and at that point I will throw LoPO4 in and bump the capacity to around a 800AH. That will get my overengineered solution to add more value. For now my goal is to keep the batteries topped off while at sea.