Batteries

[XBoater]

Looking to upgrade battery systems on my new to me Jefferson.

First the previous owner removed the old 8D batteries and installed 2 Grp 31 in each battery box. Each engine uses a battery box for starting and has its alternator wired to charge the battery box. Each box is wired to a separate side of the house battery switch so I use 1,2 or both for house power.

My concern is I have a12 volt fridge and no central inverter so I worried one bank may not be enough to overnight.

I thinking about using bank 1 as the starter for both engines and replacing bank 2 with 8D lithium.

So to do that, can I attach both alternators to the starter bank?
I was thinking to attach a DC to DC charger from bank 1 to Bank 2.
Does the DC to DC sense the incoming voltage from the alternator to turn on, or what controls the charging, don’t want to drain starter battery bank.
I have to get a 120v charger for the lithium bank to charge on the generator as the 3 bank charger will only charge one type and I connect it to each battery AGM in bank 1 and gen battery.
Any thoughts or comments would been great.

 

[DavidM]

Not sure what lack of an inverter has to do with anything. Everything you mention runs on DC.

Sounds to me that you rely entirely on the 1,2,all switch to isolate the two banks. Much better to do it automatically.

Here is what I would do:

A single G31 battery should be able to start any diesel below 8 liters. So use a single G31 for each starting battery. Wire the two extra G31s in parallel as a house bank and supply all non starting DC loads from the new house bank.

Wire the output of each alternator to its respective starting bank, then through a Blue Seas ACR to the house bank.

This let’s both alternators charge the house bank through the ACRs but isolates them so they can’t inadvertently be run down.

Should be pretty cheap to implement: $200 for the ACRs pluse some wiring and connectors.

Wait until you really know how much house amp hours you use before considering Li. Install a Renogy or Victron shunt based battery monitor to give you that info. Another one or two G31s in parallel with the other two house batteries is a pretty cheap way to expand your house bank.

David

 

[tiltrider1]

You are on the right track with a dc to dc charger. You will need to run a power wire from your ignition to the dc to dc charger to activate it when the engines are running.

 

[ranger58sb]

First the previous owner removed the old 8D batteries and installed 2 Grp 31 in each battery box. Each engine uses a battery box for starting and has its alternator wired to charge the battery box. Each box is wired to a separate side of the house battery switch so I use 1,2 or both for house power.

My concern is I have a12 volt fridge and no central inverter so I worried one bank may not be enough to overnight.

I thinking about using bank 1 as the starter for both engines and replacing bank 2 with 8D lithium.

Might be easiest to just add battery capacity to the bank that runs your fridge. Or both banks... Depending on your space available. With a DC fridge, no inverter required... and inverter overhead would be another drain anyway.

The original 8Ds would have provided approx 220-245-ish Ah nominal capacity, depending on brand, type, etc.

Two typical G31s gives you approx 200 Ah, a step backwards in capacity. OTOH, three G31s -- i.e., adding one -- would give you about 300 Ah, possibly significant enough to be useful. (Lifeline makes a higher capacity AGM G31, 125 Ah each, so 3x would be 375 Ah... and no maintenance... but at significant $$$$$$.)

Or... 4x GC2 6V deep cycle batteries wired in series/parallel would give you approx 440 Ah, and would still be fine for engine starting.

There's some juggling to do, with old batteries vs. new. For example, just adding a new (eg., third) battery to an old bank isn't usually recommended. Instead, the usual recommendation is for all batteries in a given bank to be same size, age, brand, chemistry, type, etc. And then your charger may like all banks to be all that "same" stuff, too... although there's oftensome flexibility there as long as voltages for each bank pretty much match what the battery maker(s) recommend.

Usually not much additional tech involved in adding to bank capacity, though. New jumper wires, that's pretty much it.

-Chris

 

[Bmarler]

If you’re going to hook both alternators to the same bank they would need to externally regulated to be efficient.
Instead, maybe think about upgrading one alternator to a high output programmable one for charging the lithium bank, and use the other for the starting bank.

 

[O C Diver]

You can run both alternators to charge the start batteries, and they will run near full output if you're simultaneously running DC to DC battery chargers. Where they fall short is more quickly restoring the start batteries to full. In essence, an alternator with a standard internal regulator is designed to handle loads first, and be a mediocre battery charger second. That's why boaters with deep house battery banks use an external programmable regulator to make the alternator an optimal battery charger.

The more important question is, what alternators do you have? Most alternator aren't designed to run near full output for hours.

Possibly a better idea is to run both engines off one battery bank and charge it with ONE engine alternator. Use the second engine alternator to charge the house bank. If you feel you need a lot of alternator capacity, it may be worth upgrading the house bank alternator to a higher amperage model with an external regulator to optimize battery charging.

Ted

 

[SteveK]

Prior to going to 800Ah LFP house bank the starboard engine charged the house bank. The port engine charged the start bank which is used for both main engines. Both 75~A ALT are internal regulator type
My solution was to leave port charging start bank, I moved the starboard ALT to the GEN start battery. From engine start and GEN start DC2DC chargers (100A total) to the new house LFP bank.
With the GEN running the FLA charger and two inverters I can charge the house bank with 200-250 amps per hour.

 

[Mac2]

You are on the right track with a dc to dc charger. You will need to run a power wire from your ignition to the dc to dc charger to activate it when the engines are running.

I have an ACR charging relay I have not hooked up yet. What is the difference between the ACR and dc to dc charger? I'm thinking it might be the ignition wire you referred to because (I was told by the marine store) the ACR voltage can go both ways to charge batteries in either direction. Maybe the "optional" ignition wire stops the bi-directional charging, preventing the house battery from draining a start battery.

 

[Ka_sea_ta]

ACRs will disconnect when the battery voltage drops below the charge voltage. ACR's work best when the batteries are the same chemistry ie agm to agm . DC to DC chargers are a good way to go when the battery chemistry is different and especially when charging lithium batteries from a charging source designed for LA batteries

 

[tiltrider1]

I want to caution people about connecting alternators directly to LiFePo4 battery banks. It can kill your alternator under certain circumstances. There are two ways to do this. One is with the right equipment that properly manages the alternator. The other is to use the boat’s systems in a way that you will never experience the issue.

Back in the day we had 1,2,all, off switches to determine which batteries got charged but we forgot to flip the switches appropriately. Then we came up with a better solution called the battery isolaters. This idea fixed our poor memory issues but it consumed a lot of our battery power. To solve this the ACR was invented, only the ACR doesn’t play well with mixed use batteries, such as, Li to LA or Deep cycle to Start batteries. For these issues DC to DC chargers were invented.

 

[luna]

To solve this the ACR was invented, only the ACR doesn’t play well with mixed use batteries, such as, Li to LA or Deep cycle to Start batteries. For these issues DC to DC chargers were invented.

I'm curious, why does an ACR not play well with mixed use batteries such as Deep Cycle (Antimony) to Start (Calcium) batteries?

 

[tiltrider1]

I'm curious, why does an ACR not play well with mixed use batteries such as Deep Cycle (Antimony) to Start (Calcium) batteries?

DeepCycle banks usually get deep discharges where Start banks usually do not experience a deep discharge. What happens is the ACR kicks in, the charger sees the deep discharge and kicks in the voltage and amperage. The DC batteries are now happy but the Start batteries are now getting boiled. Each time this happens the start batteries lose some life expectancy.

Is this the end of the world? No. Its just not as optimum as using a DC to DC charger.

 

[Barking Sands]

Looking to upgrade battery systems on my new to me Jefferson.

First the previous owner removed the old 8D batteries and installed 2 Grp 31 in each battery box. Each engine uses a battery box for starting and has its alternator wired to charge the battery box. Each box is wired to a separate side of the house battery switch so I use 1,2 or both for house power.

My concern is I have a12 volt fridge and no central inverter so I worried one bank may not be enough to overnight.

I thinking about using bank 1 as the starter for both engines and replacing bank 2 with 8D lithium.

So to do that, can I attach both alternators to the starter bank?
I was thinking to attach a DC to DC charger from bank 1 to Bank 2.
Does the DC to DC sense the incoming voltage from the alternator to turn on, or what controls the charging, don’t want to drain starter battery bank.
I have to get a 120v charger for the lithium bank to charge on the generator as the 3 bank charger will only charge one type and I connect it to each battery AGM in bank 1 and gen battery.
Any thoughts or comments would been great.

A minimalist system for overnighting....The new Victron Orion 50 amp DC2DC charger is an excellent unit. Its very efficient and does not heat up like the old one. To help your internally regulated alternator you can adjust amp output from 0-50 amps in .1 increments. So essentially you can use this DC to DC charger programming to limit alternator output. You can wire up activation of the 50 amp Orion in several ways. Remote switch, activation with ignition or any 12 volt source, activation with any ground, such as through an oil pressure switch. I believe you could also control it via bluetooth. For a charger you might look into the Victron IP22 30 amp charger if you are just doing overnights. If 30 amps isnt enough you can stack them. And for the price this isnt a bad way to go. Essentially you would leave the dock with the lifepo4 bank already charged by the 30 amp IP22, continue to be topped off with the alternator and DC2DC charger under way and when anchored have 100% of whatever Lifepo4 bank you have. Size Lifepo4 bank for sufficient power to run items overnight. More than likely a single 300 ah will be plenty. You can also build on these items in the future. Whatever charger you get though, be sure it is fully capable of custom settings. Anything that simply has "Lithium" setting is probably going to be inadequate. You should be able to set bulk/absorb voltage as well as float voltage to your exact settings. Of course you can get much more elaborate but the above would probably be in the $1000 range not including wiring or terminals.