Faster battery charging on the hook

[IslandTractor]

Can buy a lot of fuel for a generator as well....

If you like the sound of a generator running then yes.

The conversion to lithium is not cheap but it is a reasonable consideration when it comes time to replace a battery bank. Prices of lithium batteries has dropped and the benefits are quite significant if either weight, time of charging or ability to discharge to nearly 0% SOC without damage is desirable. A 1600 amp/hr bank of AGM discharged to 60% SOC is really just a functional 600 amp/hrs of usable battery storage and because of the prolonged absorption and float stages can take many hours of charging time to replenish. A 800 amp/hr lithium bank could be discharged to 20% SOC with identical functional capacity of about 600 amp/hrs but would take much less time to recharge each day. The Battleborn G31 size (or is is G27??) is 100 amp/hr and comes with a 10 year warranty so reliability has clearly improved as well. The SV Delos has a bank installed and these batteries are increasingly popular with the RV set too.

I'd guess we will all be using lithiums in ten years so the issue today is whether the benefits justify early retirement of functional flooded or AGM battery banks. If you are happy with your traditional battery bank then the answer is probably no but if you are dissatisfied with the time it takes to charge it up each day then an early conversion seems a reasonable consideration.

 

[Delfin]

Has anyone figured out a slick solution for faster battery charging while off shore power? I routinely drop to 60ish percent at anchor since the inverter does almost all the boats AC needs and with a 1600ah agm bank it’s about 8hrs of gen time to recharge using the xantrex 3000 inverter/charger. As far as I know the lifeline L16s will take way more charging amps than the 150, plus at 80 percent the xantrex drops charging rate as it switches to absorption, great if plugged in for long periods but not sure it’s needed during daily use.
I thought about 3 options:

Larger AC bulk charger - hard to wire and play nice with the xantrex, cheapest, requires generator run time.

Large alternator off gen or AC motor - noisy as I’d loose the sound shield, Ac motor would be super noisy given my watermaker sound. Requires generator run time.

Small engine with alternator - complex, another thing to service, But adds redundancy and low fuel usage.

Other than the washing machine, heat pumps (for cooling only) and water maker I don’t need the gen if I did a separate solution.

Has this problem already been solved, and/or am I over thinking it? This was interesting Diesel Battery Charger


AC

The problem is the charge taper rate for lead acid chemistry to get them charged fully so they don't die early. Increasing charging capacity doesn't help, since of the 8 hours you're charging, a big chunk of the time wouldn't benefit from increase initial capacity since the charge acceptance rate is below even a modest charging capacity. IMO the optimal solution is 800 Ah of LifePo4 batteries that have no taper. If your charge capacity is 150 amps from the Xantrex, you can replace the 320 amps you say you are using overnight in 2 hours, 15 minutes. Not a cheap solution, but you'd be happy with the result.

 

[dhays]

I'd guess we will all be using lithiums in ten years so the issue today is whether the benefits justify early retirement of functional flooded or AGM battery banks. If you are happy with your traditional battery bank then the answer is probably no but if you are dissatisfied with the time it takes to charge it up each day then an early conversion seems a reasonable consideration.

I think you are probably correct that the cost will come down and therefore the cost/benefit ratio will come down as well.


As has been pointed out, switching to Lithium isn't just a battery swap. It is a complete system change and so the entire cost needs to be considered. The OP may already be at that point since his current charging system can't even get up to his current batteries max charge acceptance in Bulk mode.


I'm a former sailor. I'm cheap. Both with money but also with Amp hours. It sounds to me as if the OP has a lot of inverter use but doesn't want to run the generator much. It may be that switching to Lithium and redoing his charging system may allow that. OTOH, a fuel cell might accomplish the same thing?

 

[Charlie williams]

Lots of DC

I have 4 Northstar 8D AGM military grade tank batteries in our Mainship 390. 2000 AMP combined reserve capacity.
Xantrex 40 amp charger does the trick after being on the hook a couple days with no gen running.
The 3 175 watt solar panels on top of the bemini replaces what was used by noon back to 100%. By 10 am they produce 15-25 amps of current at 14.5 volts through a smart charger.
Solar system cost me about 700 bucks, panels are good for 6-10 years per the manufacturer ( high end not the cheap stuff)
4 gage from the solar system to the batteries....
1 refrigerator, 1 medium deep freeze and the big Dometic freezer chest (we can empty our side by side from home into when we head to the Tennessee river for extended stays. I also keep my stereo system cranked while on the hook if we’re in the water, so a 1000 watt CLASS D AMP is also getting a work out. We also keep a counter top Ice maker running most all day making ice on demand running off a zantrex 3600 watt inverter..
I converted EVERYTHING to LED, that made a big difference for night current draw.
Solar system was a good project and I’m glad I did it,.

 

[cabinetman1955]

Batteries

Have you looked at your energy consumption. Have you installed LED lights and looked at all the ways to reduce your power consumption. Energy efficiency is where I would start. Are you running things that do not need to run or do you have unnecessary drain on your system?

 

[Simi 60]

If you like the sound of a generator running then yes.

Not everyone has a poor installation.
Noisiest part of our genset is exhaust water sploshing

The conversion to lithium is not cheap but it is a reasonable consideration when it comes time to replace a battery bank. Prices of lithium batteries has dropped and the benefits are quite significant if either weight, time of charging or ability to discharge to nearly 0% SOC without damage is desirable.

Conversion to lithium is ridiculously expensive
We have 8 x 220ah agm and they cost $3000 aud in total ($2100 USD)
How much would 1800ah of lithium cost
or even half that size?

Running pretty much 240v everything including hot water, they rarely get down to 80% SOC overnight and are usually at 100% SOC by midday on solar alone.

Plus, we like the weight
We still have the old dead 6x250ah agms down below as ballast and are thinking of adding a couple more tonne of lead.

 

[Lou_tribal]

Not everyone has a poor installation.
Noisiest part of our genset is exhaust water sploshing



Conversion to lithium is ridiculously expensive
We have 8 x 220ah agm and they cost $3000 aud in total ($2100 USD)
How much would 1800ah of lithium cost
or even half that size?

Running pretty much 240v everything including hot water, they rarely get down to 80% SOC overnight and are usually at 100% SOC by midday on solar alone.

Plus, we like the weight
We still have the old dead 6x250ah agms down below as ballast and are thinking of adding a couple more tonne of lead.

Not everybody has a 60 feet trawler with enough room to fit as much solar and batteries as you have, this does not make it a poor installation but maybe the only one possible with the available space and configuration.
Still I agree lithium cost is prohibitive, but would I have that kind of money choice would be different.

L

 

[Simi 60]

Not everybody has a 60 feet trawler with enough room to fit as much solar and batteries as you have, this does not make it a poor installation but maybe the only one possible with the available space and configuration.
Still I agree lithium cost is prohibitive, but would I have that kind of money choice would be different.

L

Poor installation was in regards to noisy genset comment.
I have been on 35fters with a quiet genset install.

 

[rslifkin]

Poor installation was in regards to noisy genset comment.
I have been on 35fters with a quiet genset install.

Yup, size doesn't dictate genset noise. The gen on my 38 footer is very quiet from the outside, although they didn't bother to make it nearly as quiet inside.

 

[Maerin]

I'm a believer in solar. I resisted it for a time, my wife was pushing for it, so you know how that plays out. It made a HUGE difference with battery management. When we spend time in the Bahamas, we are off grid for months. We have 1100 AH AGM bank, 480W of solar that can catch shade from the bimini. Anticipated and planned for that from the get go.

The solar enables me to run the genset in the morning to get the batteries through the absorb charge, then shut down the genset. That run time works out to be long enough to do a load of wash, heat water, make more water than the wash consumes, and complete the absorb cycle. At that point, the genset can be shut down and the solar completes the float cycle, getting the bank to 100% charge in the afternoon. That 100% charge is critical for battery life; without that full float, the capacity of the bank erodes cumulatively, and each day that the bank doesn't float 100% reduces the capacity, it's not a straight line reduction.

Best move I ever made for battery bank maintenance. I killed an expensive LifeLine AGM bank through chronic undercharging. Along that same thread, it's also critically important to set the charging profile to the battery manufacturer's spec. That includes voltages AND temperature curves. Presets don't cut it. The devil's in the details.