Charging taking too long on generator

GnrlPatton

GnrlPatton

Well-Known Member
Jul 12, 2010
719
Maple Valley, WA
Boat Info
Current: 1998 370 Express Cruiser
Sold:1988 230 Weekender
Engines
Twin Cat 3116T
Have been noticing lately that when I run my generator to charge up the batteries, it's taking forever and not really getting topped up. I have what I assume is the original charger - Pro Mar 40 - which is a 40 amp 3 bank charger. I've got 2 24v banks, one for each engine, and then a house bank of 4 6v golf cart batteries in series/parallel.

Yesterday while on the hook, my inverter alarm went off that my house voltage was low (11.7v), so I fired up the generator and ran it for 6 hours, expecting it to get me back to full charge. After running it that long, it looked like it only got to 12.4. That doesn't sound right to me, so I'm wondering if my charger is heading south. I'm going to check the battery fluid level, as I know that will impact charge capacity.

Think it's time to replace the charger? Or time to reset my expectations on generator charge times? I don't think I have the problem on shore power, but I always leave it for a week or more, so it would have plenty of time to slowly charge.

Thanks,
Kevin
 
Interesting. You don’t say what type batteries, flooded, AGM? How old are the battery banks? Could be a few things, including electrolite levels, but the charger would be high on my list. My charger died all of a sudden. I replace with a Promariner 1240P, been solid ever since.

I would check the batteries with a load meter to rule them out. You could verify 120 going to the charger, and voltage from the charger to the batteries are correct.
 
As long as the generator is operating correctly, supplying 120volts, it has nothing to do with the generator! 120 volts is 120 volts whether it is coming form shore or generator. You need to do more diagnostics. I can charge my batteries on generator in about an hour at most. You need a new charger most likely
 
You say you have 24v banks, but you are measuring voltage at 11.7?

does the charger work properly when plugged into shore power?
 
I think the generator would be last on my list of possible culprits. Your charger doesn't know the difference between shore 120 and Generator 120. I'd start by checking the batteries, and then move on to the charger. My guess is if you ran an identical test on shore power the results would be the same.

It's probably about time to upgrade that 22 year old charger. A new smart charger will help pay for itself by being gentler on your batteries.
 
GnrlPatton said:
Have been noticing lately that when I run my generator to charge up the batteries, it's taking forever and not really getting topped up. I have what I assume is the original charger - Pro Mar 40 - which is a 40 amp 3 bank charger. I've got 2 24v banks, one for each engine, and then a house bank of 4 6v golf cart batteries in series/parallel.

Yesterday while on the hook, my inverter alarm went off that my house voltage was low (11.7v), so I fired up the generator and ran it for 6 hours, expecting it to get me back to full charge. After running it that long, it looked like it only got to 12.4. That doesn't sound right to me, so I'm wondering if my charger is heading south. I'm going to check the battery fluid level, as I know that will impact charge capacity.

Think it's time to replace the charger? Or time to reset my expectations on generator charge times? I don't think I have the problem on shore power, but I always leave it for a week or more, so it would have plenty of time to slowly charge.

Thanks,
Kevin
Click to expand...
What are the battery sizes? Charge time is completely based upon how many amp hours the batteries need.
Also, There is no way that battery charger can charge 24 volt banks. Are you sure they are 24 Volt? Your boat listed is a 12 Volt boat unless someone did some major changes. I suspect for your engine start banks that they are two Gp 27 batteries in parallel providing 12 volt for each engine. That would be around 180 amp hours per engine start bank. Then as you say the house at series/parallel at 12 volt; can't do 4 six volt batteries in series/parallel and get 24 volts. For a typical 6 volt golf cart battery the storage capacity is 240 amp hours so the four batteries in series/parallel would be 480 amp hours at 12 volts. So 11.7 volts is about 50 % DOD (or a SOC of 0%) which means you need to pump 240 amp hours into the bank. That means for the bulk charge cycle the charger will take about 5.5 hours at the full 40 amps (dreaming) then the absorption phase (assuming lead acid that last 10%) will probably take another 3 to 5 hours.
The issue is you are working that little charger to it's grave for the house bank. That charger is probably shutting down on overheat several times during the house bank charging which will extensively extend the charge time.
 
The battery banks are all 12v, my bad. I have 2x 12v Group 27 flooded batteries wired up in parallel for each engine, and then the house bank is 4x 6V golf cart flooded batteries wired in 2 series to get them to 12v, and then in parallel to double up the aH. Each battery on the house bank is rated at 235aH, so in my configuration, I would have 470aH capacity.

I would need to trace the wiring configuration, but I think from a charger point of view, the house bank is bank 1, the engine batteries (all 4 of them) would be bank 2, and then the generator battery (Group 24, flooded) is bank 3. All are 12v. The house bank is 3 years old, starting batteries less than a year, and then generator is I think 5 years. I check all electrolyte levels about every 2 months and top up as needed.

I suspect that, as Tom says, I'm overworking the charger. As many of you have said, I don't think it has anything to do with the generator. The previous configuration was the house bank was 3 12v Group 27 batteries, so much less capacity, and probably a quicker charge time which worked for the current charger. Looking at options for upgrading the charger, I'm seeing the ProMariner pronautic line that goes 30-60a (I don't need the charger/inverter option, as I installed a Xantrex 2000 last year), would I be better off going with a larger charger like the 12-60?

1 other variable in this is that I also installed a solar array last year, that feeds in to my house bank. 2x ~100W panels hooked up in parallel and going through an MPPT charge controller. I thought that it would feed enough juice in to slow the bleeding of power, but I am so far not that impressed with the performance. At best I'm getting 3-4 amps with direct sun, and that's only for about 2-3 hours of the day. Solar is probably not the best solution in this part of the world!

Thanks all for the inputs, appreciate it.
Kevin
 
The pronautic 12-xx are excellent chargers. Given your setup, I'd go with the 60, making sure your cabling is of sufficient gage to handle the loads.
 
I think I looked at this when I replaced. The AC side will allow the 40, 50 or 60 A version , but if you go above the 40A, the DC wires to the battery banks may have to be resized... I think I had #6 and the larger chargers require #4. If you did the wiring for the inverter, you likely already have the crimper (or can get one cheaply). However with that big house bank, your still looking at several hours to recharge a 470 Ah battery bank to 100%

Just a thought. You might consider upgrading the inverter to an inverter charger instead. The Xantrex XC series has a 2000W True Sine inverter with 80A dedicated charger. You could leave the current charger to charge the engine batteries. One other upshot is that charger can handle LiFePo4 batteries that are getting pretty reasonable and are much better for inverter setups.
 
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dtfeld said:
I think I looked at this when I replaced. The AC side will allow the 40, 50 or 60 A version , but if you go above the 40A, the DC wires to the battery banks may have to be resized... I think I had #6 and the larger chargers require #4. If you did the wiring for the inverter, you likely already have the crimper.
Click to expand...
Yep, as well as some extra #4 wiring, so I likely have everything I would need.

Looking at the math from tmott's post, it looks like 11.7v is the lower threshold to start looking for external power (either shore or generator), and with the 60a charger I'd be looking at about 4 hours of bulk charge and another ~3 hours of float? Is 11.7 too low, should I start that sooner? I know the GC batteries are built to be able to run lower than standard deep cycles, but I don't want to lead them to an early death...

Kevin
 
ttmott said:
Victron Centaur 12/80
https://www.victronenergy.com/upload/documents/Datasheet-Centaur-Charger-EN.pdf
Or when that Xantrex craps the bed (and it will) step over to a Victron Quatro Inverter / Charger
https://www.victronenergy.com/upload/documents/Datasheet-Quattro-3-10kVA-120V-EN.pdf
Click to expand...

I installed a Magnum Energy MS 2812 with a 125A charger. I purchased used to save some cash and see if I like/use it. It lives up to what I had intended for use, but now, one of the biggest limitations on the boat is knowing the status of batteries.

I'm considering upgrading the DC system and have been looking and studying up on the Victron offering. If I were doing it again today, I would probably install a Victron system. Well integrated with in its own product line, but also with Raymarine. Lots of data to see where your battery power is going.

The other improvement is looking at LIFePO4 batteries. Expensive up front but better costs long term.
 
GnrlPatton said:
Yep, as well as some extra #4 wiring, so I likely have everything I would need.

Looking at the math from tmott's post, it looks like 11.7v is the lower threshold to start looking for external power (either shore or generator), and with the 60a charger I'd be looking at about 4 hours of bulk charge and another ~3 hours of float? Is 11.7 too low, should I start that sooner? I know the GC batteries are built to be able to run lower than standard deep cycles, but I don't want to lead them to an early death...

Kevin
Click to expand...
Kevin - the interesting thing about Lead Acid batteries is they will take a permanent memory if routinely discharged fully to that 0% SOC (which is around 50% of the total battery rating) and then never be able to realize the full Ah capability. Even worse if discharged below 0% SOC they will be irreparably damaged and their life expectancy shortened. I try to never go below 10% SOC and keep margin plus this greatly extends the life of the battery. If you continue to manage your batteries as you are doing expect more than 5 years of good service. It goes without saying that a good multistage charger is essential.
One thing not mentioned is you can supplement the generator powered charger with the main engine alternator for the house bank; it is additive.... But that's burning diesel; A high output charger is the best answer.
 
dtfeld said:
I installed a Magnum Energy MS 2812 with a 125A charger. I purchased used to save some cash and see if I like/use it. It lives up to what I had intended for use, but now, one of the biggest limitations on the boat is knowing the status of batteries.

I'm considering upgrading the DC system and have been looking and studying up on the Victron offering. If I were doing it again today, I would probably install a Victron system. Well integrated with in its own product line, but also with Raymarine. Lots of data to see where your battery power is going.

The other improvement is looking at LIFePO4 batteries. Expensive up front but better costs long term.
Click to expand...
I think you know where I'm going....
http://clubsearay.com/index.php?threads/500-520-db-official-thread.90789/page-49#post-1147125
 
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