Decision Time - House Bank Is Toast

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markpj23

markpj23

Senior Member
Joined
Mar 25, 2021
Messages
197
Vessel Name
Black Horse
Vessel Make
Med Yachts 62
After our 2nd extended time away from the dock since purchase I feel safe in saying that our house bank is toast. There are 6 - 8d batteries less than 4 years old. Hard to believe they have such a short life but I have no clue as to how they have been treated. The right components seem to all be here: Balmar alternator controls, Xantrex inverter/chargers, BlueSeas ACRs and all seems to be functioning.

Assuming 200ah for each 8d, I should have 1200ah @50% discharge = 600ah or pretty close if I've got the math right. My Victron battery monitor showed a whopping 168ah consumed when the inverters shut down for low battery voltage (11.6 volts if I remember correctly).

My load averages 48 amps (measured by the Victron). We run a big residential refrigerator, plus a dorm sized fridge, plus some engine room blowers on 120v. Add to that my 12v loads for nav gear, etc and we are the definition of why trawlers love to travel from one dockside power connection to the next :D

I could go the cheaper and quick route and just swap out the 8d AGMs. I want to be able to get through the night w/o the generator and new AGMs would probably allow that. Not much reserve though.

Sure is tempting to go the LiFePO route and get at least twice that capacity, although still at nearly twice the cost for the UL listed Kilovaults. Throw in the external BMS, Wakespeed, etc and the cost difference is not trivial. Throw in the ABYC standards evolution and possible insurance issue and the decision gets 'complicated.'

Two questions for the group:
- Am I correct that my current batteries are shot or am I just expecting too much of them?
- Is the current cost & complexity of the LiFePO solution worth the additional capacity? (I know that's subjective....)
 
It's entirely possible that the current bank is shot, although 11.6 volts sounds high for an inverter low cutoff to me (a heavy burst of load with the batteries partially drained could definitely get down to 11.6).



If you want to find out for sure, do a C/20 discharge test. Get the batteries fully charged, then apply a load at the 20 hour rate (60 amps for a 1200ah bank) and time how long it takes to reach 10.5 volts (typical end of discharge voltage at C/20 for lead acid batteries). If it takes much under 20 hours, they've lost some capacity. If you hit 10.5 volts after, say, 10 hours, then they've lost half their capacity and would be considered end of life (usually the threshold to condemn is somewhere around 70 - 80% of original capacity).
 
What runs overnight? What is their draw in watts or V & A?

If electronics other than a dedicated anchor alarm is operating and the E.R. fans are running then you may be expecting to much.

Lighting changed to LED? That can make a big difference.

Before you make this kind of decision you need to assess what is allowed to operate overnight and how many watts those items add up to so you can estimate the draw.
I assume the fridges are run from the inverter. THe inverter itself will need power over and above what it supplies, about 10% as the static controls operation themselves need power constantly.

You will get many suggestions but you still need to do a decent electrical survey of what draws what and what is left running overnight before an informed decision can be made. Even LiFePO4 have limits.
You may be asking to much.
 
How long was your boat sitting unused before you took possession? In getting any recently purchased boat, RV or car properly set up, I have learned to expect the battery(s) to have been neglected through the listing period. This is especially true if the listing broker (or Used Car sales lot) to be inadequately set up to keep complex battery systems charged. In RVs, they often sit far from any possibility of being plugged in, and spend long days with all the interior lights fully on to show off to casual tire kickers.
My last car showed severe battery weakness in the first month after purchase, to the point that I was all set up to go and get a hard to source new one. One last attempt to get a full charge put that trip off, and now, 6 years later, my original battery is still doing just fine.
4 years in is too soon to give up on yours.
 
Average is 48 amps. Over 20 hours that is 960 or 360 over the 50% discharge rate.
IMO you need more batteries with total 1920 Ah or need to reduce load for the ones you have.
 
koliver said:
How long was your boat sitting unused before you took possession? In getting any recently purchased boat, RV or car properly set up, I have learned to expect the battery(s) to have been neglected through the listing period. This is especially true if the listing broker (or Used Car sales lot) to be inadequately set up to keep complex battery systems charged. In RVs, they often sit far from any possibility of being plugged in, and spend long days with all the interior lights fully on to show off to casual tire kickers.
My last car showed severe battery weakness in the first month after purchase, to the point that I was all set up to go and get a hard to source new one. One last attempt to get a full charge put that trip off, and now, 6 years later, my original battery is still doing just fine.
4 years in is too soon to give up on yours.
Click to expand...




Excellent points.
Is this a new to you boat. If so Kolivers suggestion would be very valid.


Something I just though of is have you checked for Ghost loads. I have had a few on mine, much smaller simpler boat, but none the less they caused me some trouble. They could be outright leakage from goofy wiring causing a drain. They could be electronics that do not truly shut down as long as a power source is available. Although each is small if they do not fully shutdown then the draws can add up.

TV, your inverter controls mentioned, VHFs, , radar, sounders, MFD, and so on, literally any thing with a push button On/Off control.
 
If you do decide to upgrade...I changed over to AmperTime Li and could not be happier for all the reasons I am sure you have read about. But the primary reason is that I don't have to be so consumed by managing and wthem to try to get max life span. Non Li batteries can be severely damaged with just one or a few mistakes (draining them). And the other big advantage is recharge time. I put 3x 200Ah 12V on my 48 ft Hattwras. Runs a chest freezer and a full size fridge along with TV, lights etc fine overnight. I usually run our genset for about an hour in the am and again at dinner for cooking and water heater. I did all the work and yes to do it right it is not cheap but there are ways to keep most of your existing infrastructure by using boost regulators.
 
I assume you have checked the water level on your batteries. This is the first place that I would start.
 
rslifkin said:
It's entirely possible that the current bank is shot, although 11.6 volts sounds high for an inverter low cutoff to me (a heavy burst of load with the batteries partially drained could definitely get down to 11.6)....
Click to expand...


I checked my Xantrex settings and the low DC voltage cutout is set to 10.5 volts. I don't ever remember seeing the voltage this low but apparently it did get there.
 
C lectric said:
What runs overnight? What is their draw in watts or V & A?

If electronics other than a dedicated anchor alarm is operating and the E.R. fans are running then you may be expecting to much.

Lighting changed to LED? That can make a big difference.

Before you make this kind of decision you need to assess what is allowed to operate overnight and how many watts those items add up to so you can estimate the draw.
I assume the fridges are run from the inverter. THe inverter itself will need power over and above what it supplies, about 10% as the static controls operation themselves need power constantly.

You will get many suggestions but you still need to do a decent electrical survey of what draws what and what is left running overnight before an informed decision can be made. Even LiFePO4 have limits.
You may be asking to much.
Click to expand...


Agreed. I can tell the load of course by just looking at the Victron and seeing the amp draw. Once I've shut down anything I don't consider essential, the amp draw reading is my baseline. That average right now is 48a.
 
You say chargers, alternators, etc. “all seem to be functioning”. Learn your system in detail and check that your charging profiles are set correctly and working correctly. It’s worth the effort because incorrect charging is one of the most common ways to kill your batteries.

Lots of new batteries are damaged or killed because they are installed to “fix” the problem, when the charging system was always the cause. I always suggest that you test your charging system and make changes and adjustments, including testing, with your old batteries in place. Then put new batts into a system that you know works. That way you don’t abuse new batts while you are sorting it out.
 
Nigel Calder's book(s) on boat electrical systems are required reading for
troubleshooting battery related issues. I would methodically check every
potential problem and correct it, then see if your batteries can be saved or not.
 
C lectric said:
...Something I just though of is have you checked for Ghost loads. ....
Click to expand...

I already know that my 33 year old boat has many, many connections made outside of the main electrical panels. Heck, I've added a few myself.

I guess my approach at this point is that I know what my loads are, ghost or otherwise, by just reading what the Victron tells me after I've shut down everything not needed while at anchor. That 48a average load is what I want to be able to satisfy for 10 hours to get through the night with no generator.
 
guy with a boat said:
You say chargers, alternators, etc. “all seem to be functioning”. Learn your system in detail and check that your charging profiles are set correctly and working correctly. It’s worth the effort because incorrect charging is one of the most common ways to kill your batteries.

Lots of new batteries are damaged or killed because they are installed to “fix” the problem, when the charging system was always the cause. I always suggest that you test your charging system and make changes and adjustments, including testing, with your old batteries in place. Then put new batts into a system that you know works. That way you don’t abuse new batts while you are sorting it out.
Click to expand...


Good advice - thanks
 
koliver said:
How long was your boat sitting unused before you took possession? In getting any recently purchased boat, RV or car properly set up, I have learned to expect the battery(s) to have been neglected through the listing period. This is especially true if the listing broker (or Used Car sales lot) to be inadequately set up to keep complex battery systems charged. In RVs, they often sit far from any possibility of being plugged in, and spend long days with all the interior lights fully on to show off to casual tire kickers.
My last car showed severe battery weakness in the first month after purchase, to the point that I was all set up to go and get a hard to source new one. One last attempt to get a full charge put that trip off, and now, 6 years later, my original battery is still doing just fine.
4 years in is too soon to give up on yours.
Click to expand...
Agreed. The boat was in active use before purchase though.
 
rslifkin said:
....If you want to find out for sure, do a C/20 discharge test. Get the batteries fully charged, then apply a load at the 20 hour rate (60 amps for a 1200ah bank) and time how long it takes to reach 10.5 volts (typical end of discharge voltage at C/20 for lead acid batteries). If it takes much under 20 hours, they've lost some capacity. If you hit 10.5 volts after, say, 10 hours, then they've lost half their capacity and would be considered end of life (usually the threshold to condemn is somewhere around 70 - 80% of original capacity).
Click to expand...
OK but real use of the system did essentially this test. I drew a bit less than the 20% amperage (48a) for 3.5 hours and the system cutout on low battery voltage. Isn't that enough to let me know that the battery capacity is not there?
 
Soo-Valley said:
Average is 48 amps. Over 20 hours that is 960 or 360 over the 50% discharge rate.
IMO you need more batteries with total 1920 Ah or need to reduce load for the ones you have.
Click to expand...
I disagree with the 20 hours in the equation though. I need only 10 hours for an overnight with no genset running. So that should be ~480 Ah.
 
markpj23 said:
OK but real use of the system did essentially this test. I drew a bit less than the 20% amperage (48a) for 3.5 hours and the system cutout on low battery voltage. Isn't that enough to let me know that the battery capacity is not there?
Click to expand...
Yes, but you have not shown that the batteries are toast. But they will be at that draw.
You need more batteries for that 48A draw.
The 1200Ah rating. It is 1200/20/2= 30A average, you are drawing 18A more per hour so shortening the time they reach 10.5V. JMO
 
markpj23 said:
After our 2nd extended time away from the dock since purchase I feel safe in saying that our house bank is toast. There are 6 - 8d batteries less than 4 years old. Hard to believe they have such a short life but I have no clue as to how they have been treated. The right components seem to all be here: Balmar alternator controls, Xantrex inverter/chargers, BlueSeas ACRs and all seems to be functioning.

Assuming 200ah for each 8d, I should have 1200ah @50% discharge = 600ah or pretty close if I've got the math right. My Victron battery monitor showed a whopping 168ah consumed when the inverters shut down for low battery voltage (11.6 volts if I remember correctly).

My load averages 48 amps (measured by the Victron). We run a big residential refrigerator, plus a dorm sized fridge, plus some engine room blowers on 120v. Add to that my 12v loads for nav gear, etc and we are the definition of why trawlers love to travel from one dockside power connection to the next :D

I could go the cheaper and quick route and just swap out the 8d AGMs. I want to be able to get through the night w/o the generator and new AGMs would probably allow that. Not much reserve though.
Click to expand...


You mean average load is 48A per hour, yes?

If so, that low voltage shut-down after 168Ah consumption was at about the 3½-hour mark?

If so, and if I understand what you're describing, yes I'd guess batteries are toast -- or maybe one battery, or one cell in one battery (or something like that) is hosed and drawing down the rest of the bank. But maybe a load test would pinpoint some of that better.

Lifeline 8D AGMs (for example) are rated at 255Ah -- so 1530Ah for a bank of 6x. I've read it's not great to parallel more than 4x 12V batteries.

A 6x bank of their 6V L16s, 400Ah each, would give you 1200Ah total. (Or 8x for 1600?) Maybe worth a look?

(Other less expensive brands exist, of course.)

Either route, or some other route, oughta be able to get you through the night without needing to start the genset... even without many reserve issues, I'd think.

-Chris
 
Last edited:
ranger58sb said:
You mean average load is 48A per hour, yes?

If so, that low voltage shut-down after 168Ah consumption was at about the 3½-hour mark? ...
Click to expand...
Yes exactly right.
 
It could be just one cell on one of the 8Ds bad. Test the 8Ds individually.
 
if the average amp draw was 48, what was the peak, and how long was the duration of the peak? it's easy to get my 1125 ah bank to show low voltage if i load it that heavily. remove the load and let them recover and i bet you'll see volts that are in-line with the amp hours removed.
i don't necessarily think your batteries are used up, but they seem like they're being a bit abused by that heavy load. i agree that you might need a bigger house bank if you can't reduce that load.
 
If the batteries are all equal then he should be drawing 8 amps per battery which is less than the 20 hr rate. Before you throw out the whole bank, I would do some tests and calculations. When on shore power next time, once the bank is fully charged, disconnect the bank from supplying DC (the Xantrex should be providing 12v). Isolate each battery by disconnecting the grounds and let them sit. After about 12 hrs check the voltage on each battery and see where they are at. The resting voltage will tell you the approximate condition of the battery. I believe if it measures less than 12.6v or what the battery Mfr says then it is not fully capable. This will find a bad battery quickly. Next step is to draw out your DC system to insure the 6 batteries are connected to the load through cabling that is the same length. It’s possible that each bank of three is connected to each other and the last one in the chain is connected to the load. I also recommend reading Nigel Caulder’s book.

I had a 4 battery AGM bank that was acting like yours after 3 years and after removing 3 parallel cables between port and starboard banks, I got another 4 years out of them.

Tom
 
markpj23 said:
After our 2nd extended time away from the dock since purchase I feel safe in saying that our house bank is toast. There are 6 - 8d batteries less than 4 years old. Hard to believe they have such a short life but I have no clue as to how they have been treated. The right components seem to all be here: Balmar alternator controls, Xantrex inverter/chargers, BlueSeas ACRs and all seems to be functioning.

Assuming 200ah for each 8d, I should have 1200ah @50% discharge = 600ah or pretty close if I've got the math right. My Victron battery monitor showed a whopping 168ah consumed when the inverters shut down for low battery voltage (11.6 volts if I remember correctly).

My load averages 48 amps (measured by the Victron). We run a big residential refrigerator, plus a dorm sized fridge, plus some engine room blowers on 120v. Add to that my 12v loads for nav gear, etc and we are the definition of why trawlers love to travel from one dockside power connection to the next :D

I could go the cheaper and quick route and just swap out the 8d AGMs. I want to be able to get through the night w/o the generator and new AGMs would probably allow that. Not much reserve though.

Sure is tempting to go the LiFePO route and get at least twice that capacity, although still at nearly twice the cost for the UL listed Kilovaults. Throw in the external BMS, Wakespeed, etc and the cost difference is not trivial. Throw in the ABYC standards evolution and possible insurance issue and the decision gets 'complicated.'

Two questions for the group:
- Am I correct that my current batteries are shot or am I just expecting too much of them?
- Is the current cost & complexity of the LiFePO solution worth the additional capacity? (I know that's subjective....)
Click to expand...

8D’s are too heavy for me to lift. Cheapest & durable solution is replace with GC2’s or even better, GC1’s which will fit in your existing spaces & give more Ahrs. Deka makes decent GC’s & cheapest through Costco, Lowes or NAPA. Add a battery watering system for $200 and watering even the most inaccessible FLA takes <5 minutes and u r good for another 5 yrs+. If battery height and weight is not an issue - L16 FLA scrubber batteries will almost double the GC2’s Ahrs with similar footprint.

I share other posters concerns re 48A routine requirement. With an apartment size 1120v fridge, plus icemaker plus all the 12v stuff (though all lighting is LED) I only pull 30A when both compressors are on their duty cycle, average load is <20A.
 
I we have been on anchor all weekend. Sat TV, full size fridge, chest freezer, led lights. My consumpution is between 15-25 A per hour. But I could easily see how with eng. Room blowers it could add up to 48 A. If so I would suggest you put in around 1000 Ah of lithium. Solar would significantly reduce generator run time.
 
Yeah those blowers... Do you need them running when not underway? Why? Do you know how much current they draw?

Agree that 48a seems like a very high baseline. I'd sort that first.

Quick pedantic engineer note: A "load" is measured in Amps (or better, Watts). Amp-hours (better, Watt-hours) is a measure of energy. "Amps per hour" doesn't make any sense, as Amperage is a unit analogous to flow - so saying "Amps per hour" is like saying "gallons per hour per hour"
 
socalrider said:
Quick pedantic engineer note: A "load" is measured in Amps (or better, Watts). Amp-hours (better, Watt-hours) is a measure of energy. "Amps per hour" doesn't make any sense, as Amperage is a unit analogous to flow - so saying "Amps per hour" is like saying "gallons per hour per hour"
Click to expand...


My bad, for introducing that term. Then again, have to admit I don't fully understand the distinctions...

I think I understand Mark load averages 48A over the period of each hour...

-Chris
 
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