Dumb Charging Question

[Shrew]

I modified my 12V system so that I now have:

Starting Bank: 1 x 4D (AGM)
House Bank: 2 x 8D (AGM - Wired in parallel).

Battery Charger: 50amp Charles 3 bank

The house bank takes a LONG time to recharge. It gets to around 14.1 ~ 14.2 then trickles for a long time. Too long to run an 8K diesel generator drawing 1.5 amps AC.

The three bank charger has a leg going to the generator battery, which makes no sense to me, since the generator has an alternator and the draw to start isn't that large.

Even though my house bank is in parallel, does it make sense to run a separate leg from the charger to each house battery individually?

Is there better way to charge the batteries more quickly??

 

[rslifkin]

If the charger is a well designed unit where it can distribute the 50A output however is needed between the 3 outputs then moving one leg from the gen battery to the house bank won't help anything.

In general, getting lead acid batteries from "mostly charged" to "full" takes a while. Doing it on generator power isn't very practical even though the batteries need frequent full charges to keep them healthy.

 

[Comodave]

The solution is to get a larger battery charger.

 

[dhays]

The solution is to get a larger battery charger.

I don't think so. The problem seems to be that it is getting to the absorb charge setting and then the amps gradually decrease. Trying to get a full charge via a generator always seems to be a futile exercise.

I would check to be sure if 14.1 is really the correct absorb voltage for your AGM batteries. My US Battery AGM batteries call for an absorb voltage of 14.7v. My Lifeline AGMs call for 14.2-14.4v. If your batteries can take a higher absorb voltage then you will be putting a lotore amos into the batteries during Bulk.

 

[DavidM]

The solution is to get a larger battery charger.

And/or a newer one with a better charging profile.

Solar panels is a better way to top off batteries during the day. Consider adding at least 200 watts.

David

 

[O C Diver]

I modified my 12V system so that I now have:

Starting Bank: 1 x 4D (AGM)
House Bank: 2 x 8D (AGM - Wired in parallel).

Battery Charger: 50amp Charles 3 bank

The house bank takes a LONG time to recharge. It gets to around 14.1 ~ 14.2 then trickles for a long time. Too long to run an 8K diesel generator drawing 1.5 amps AC.

The three bank charger has a leg going to the generator battery, which makes no sense to me, since the generator has an alternator and the draw to start isn't that large.

Even though my house bank is in parallel, does it make sense to run a separate leg from the charger to each house battery individually?

Is there better way to charge the batteries more quickly??

Do you know what the charging profile (number of stages) is for the charger? While Charles was a very respected name in chargers, the profile may be better for overnight charging at the dock.

Ted

 

[SteveK]

Do you know what the charging profile (number of stages) is for the charger? While Charles was a very respected name in chargers, the profile may be better for overnight charging at the dock.

Ted

I agree with this. Unless shown otherwise, a 50 amp three leg charger shares 1/3 of 50 to each leg. Indeed a very slow way of recharge.
I have one similar three bank charger and it is ideal for non house bank batteries from shore power. A slower recharge when time allows.

 

[Nick F]

I have absolutely no doubt that, to address your problem, you need a "smart" charger dedicated to your house bank alone.

 

[Delta Riverat]

Yeah, lead acid chargers have improved greatly, and how old are the batts?

 

[fryedaze]

Are any of the battery banks tied. If the generator alternator is tied to the house it will probably just put out 14.1v at what ever amps it is designed for. They are small so they dont put out much. The genset alternator will make the battery charger less effective because the genset alt keeps the volts at 14.1 and the battery charger thinks it should go to float.

 

[tiltrider1]

“The house bank takes a long time to recharge….Too long to run an 8k diesel generator drawing 1.5 amps AC”


First problem is that you only have a 50 amp charger and you are spreading the 50 amps among 3 batteries. Changing the wiring is not going to get you anything as most of the 50 amps is already going to the house.

There are solutions but not a cheap and easy one.

Solution 1 would be to add a 100 amp charger. This would cut the initial charge time but it would not help with absorption time.

Solution 2 would be to stop charging at 80% full and recharge more frequently, i.e. several times a day instead of once.

Solution 3 would be changing over to LFP and adding a 100 amp charger. This would put more load on the generator and significantly reduce charging time. However, this is going to be the more costly solution.

Solution 4 would be to introduce solar. This brings on a lot of discussion about feasibility and cost so it’s very hard to rank this solution with out more information.

 

[Mainship Pilot]

Solar means you are always charging......at least during sunlight hours. I have 2 Renogy 175 Flex panels with a 60 MMPT controller, and on the mooring my batteries are up to full by 10:00am, with normal weekend use of systems. Honestly, I dont' even need a generator while on the mooring, except to make hot water for showers.

 

[SteveK]

Solar means you are always charging......at least during sunlight hours. I have 2 Renogy 175 Flex panels with a 60 MMPT controller, and on the mooring my batteries are up to full by 10:00am, with normal weekend use of systems. Honestly, I dont' even need a generator while on the mooring, except to make hot water for showers.

How many hours, how much charge over that time. I cannot see more than 15A per hour at peak. Your needs are spartan. I use an average 15A per hour over 24

 

[jleonard]

I used to use a sears car battery charger in addition to the on board charger to get my house bank up quicker when running the gen set. Set at 10 amps. I do the same now with my travel trailer if necessary

 

[Mainship Pilot]

How many hours, how much charge over that time. I cannot see more than 15A per hour at peak. Your needs are spartan. I use an average 15A per hour over 24

You are correct, my needs may not meet yours but it was more of an example. You could add more/larger panels to excentuate your needs quicker. You can always run a genny while using solar to increase your charging , solar is always charging unless the MPPT tells it to quit! My fridge only draws 3 amps, stereo, VHF, phones charging, and maybe a small fan. I draw 6 amps at the most at one time, unless I'm inverting to use a Microwave, or other momentary AC needs.

 

[SteveK]

@Mainship Pilot
I am very interested in solutions and have started this thread
Charging LifePO4 batteries.

Solar to meet my needs or at least make sense requires real estate I may not have. That is why I look for what you and others use and how solar makes sense.

 

[Mainship Pilot]

@Mainship Pilot
I am very interested in solutions and have started this thread
Charging LifePO4 batteries.

Solar to meet my needs or at least make sense requires real estate I may not have. That is why I look for what you and others use and how solar makes sense.

Your needs and systems are vastly different than mine so not sure how much help I can provide other than a different set up to observe. I’m still FLA in all 3 banks, thrust, start and house banks. Solar only charges the house. 2/175 Watt Flex panels mounted on Plastic breathable boards I cut to size, acquired at HD. House is 2 T-165’s.

 

[Iggy]

Are any of the battery banks tied. If the generator alternator is tied to the house it will probably just put out 14.1v at what ever amps it is designed for. They are small so they dont put out much. The genset alternator will make the battery charger less effective because the genset alt keeps the volts at 14.1 and the battery charger thinks it should go to float.

Yes. This will fool the charger. For winter storage, I would only have the genset battery on that charger. Or use a 2nd charger for the genset that you can turn on and off.

 

[SteveK]

@Mainship Pilot
You have helped. You have 350 watts with 2 panels and this tells me the 400 watt set I bought for the previous boat is not worth installing on this boat as it may only provide 25% of my daily usage. I need to add another charger to load the generator which has to run anyway to reduce run time. Thanks

 

[rslifkin]

It might not be worth buying a solar setup that only covers 25% of your needs, but if you already have it, it's worth installing. That's 25% less power you need from the generator every day which means shorter runtime, or possibly only needing to run it every other day.

 

[Bmarler]

@Mainship Pilot
You have helped. You have 350 watts with 2 panels and this tells me the 400 watt set I bought for the previous boat is not worth installing on this boat as it may only provide 25% of my daily usage. I need to add another charger to load the generator which has to run anyway to reduce run time. Thanks

I have close to the same draw as you, and I installed 2, 385 watt panels with separate controllers. The solar adds enough power back so that a don’t have to run the genset when out for a three day weekend. On the very sunny days it’s amazing. I love to sip my morning coffee in silence and watch the batteries charge on my phone.

 

[Mainship Pilot]

I have close to the same draw as you, and I installed 2, 385 watt panels with separate controllers. The solar adds enough power back so that a don’t have to run the genset when out for a three day weekend. On the very sunny days it’s amazing. I love to sip my morning coffee in silence and watch the batteries charge on my phone.

Exactly! The new Bluetooth option is awesome, every part of your charging/usage is summarized on one click on your phone so you always know you’re SOC.

 

[Mainship Pilot]

@Mainship Pilot
You have helped. You have 350 watts with 2 panels and this tells me the 400 watt set I bought for the previous boat is not worth installing on this boat as it may only provide 25% of my daily usage. I need to add another charger to load the generator which has to run anyway to reduce run time. Thanks

Steve, Also note that the 25% is only in optimum conditions! I live in So Cal so I probably see more optimum conditions than most, but even without any blockage or shadows, the lower the sun, the less opitimal for solar. On the flip side, if a couple panels can support 25% of your needs, that a big help! If you can one or two to that, your way ahead!

 

[Turtle Blues]

My original setup was very similar.
Is the Charles new enough to have the AGM charge profile?
It still takes a long time to achieve 100% and with 2x in parallel I would not want to chase that with the generator.
Would agree that constant charging of the isolated generator start battery is unnecessary and the power could be put to better use.
IMO adding solar for charging is the way to go. At first I laughed at the 200W panel that was installed to "maintain the house bank when unattended" but have found over an extended period of time it makes a significant contribution to keeping them topped off.

 

[SteveK]

Here is a calculator
400 watts may charge 160A on daily average during May, June, July, August for my location. This is why I hesitate to install what I have.
Does not seem cost effective during days on board. The last trip out 2 of 14 days had rain/cloud.

 

[darnold]

Here is a calculator
400 watts may charge 160A on daily average during May, June, July, August for my location. This is why I hesitate to install what I have.
Does not seem cost effective during days on board. The last trip out 2 of 14 days had rain/cloud.

Except the solar can do the final top off of your batteries in silence while trying to do that with a generator takes a very long time. You might find that running the generator for a couple hours in the AM to heat water and do the initial charge and leaving the rest to solar might work for your needs. Our usage is much more like MainshipPilot's and we have run our generator twice this summer (for hot water as we don't have a large enough inverter to supply the hot water tank) The setup is an 8D start, two LiFePo AH batteries, a 50amp DC-DC MMPT controller/charger and 400W solar. Your 160 AH estimate is in line with our experience this summer. I replaced the two 8D FLA batteries with two LiFePo 280 AH batteries and it is overkill for our usage, but you can never have too much power!

 

[SteveK]

Except the solar can do the final top off of your batteries in silence while trying to do that with a generator takes a very long time. You might find that running the generator for a couple hours in the AM to heat water and do the initial charge and leaving the rest to solar might work for your needs. Our usage is much more like MainshipPilot's and we have run our generator twice this summer (for hot water as we don't have a large enough inverter to supply the hot water tank) The setup is an 8D start, two LiFePo AH batteries, a 50amp DC-DC MMPT controller/charger and 400W solar. Your 160 AH estimate is in line with our experience this summer. I replaced the two 8D FLA batteries with two LiFePo 280 AH batteries and it is overkill for our usage, but you can never have too much power!

You have 400 watts solar, I bought this 400w kit to install on a GB36 and yes that would be more than enough for that boat.
Thanks for sharing that with a 560Ah bank you managed with 400w panels without GEN. That is useful info. You may have got away with one 280Ah for your needs.
I am now prepared to lay out the panels on the deck and see the result of a day of charging on the hook after an hour of GEN.

 

[Bmarler]

I’m in south Puget sound and it’s been cloudy all morning, and still cloudy now. I’ve produced only 50 amp hours so far but when the sun finally breaks through it’ll go up dramatically. I haven’t run the genset since we’ve been out.
Even if the solar helps offset the draw down during daylight hours it’s worth it to me.

 

[SteveK]

I’m in south Puget sound and it’s been cloudy all morning, and still cloudy now. I’ve produced only 50 amp hours so far but when the sun finally breaks through it’ll go up dramatically. I haven’t run the genset since we’ve been out.
Even if the solar helps offset the draw down during daylight hours it’s worth it to me.

It would help if you included the bat bank Ah and the solar panel watts along with your 24hr Ah needs.

 

[darnold]

You have 400 watts solar, I bought this 400w kit to install on a GB36 and yes that would be more than enough for that boat.
Thanks for sharing that with a 560Ah bank you managed with 400w panels without GEN. That is useful info. You may have got away with one 280Ah for your needs.
I am now prepared to lay out the panels on the deck and see the result of a day of charging on the hook after an hour of GEN.

You are spot on, after the experience this season the current plan is to move one of the batteries to my RV to replace the FLA house batteries as we never got below 400Ah so we were always able to recover to 100% SOC using solar. Running the furnace next month will be the final test to see if I need more than 280Ah and to determine if I need another 200W solar, but I am pretty sure the one battery and 400W of solar will be enough.