Will a larger battery bank maintain voltage level better than a single battery?

[john61ct]

separate dedicated bank is a quick and easy fix, but better to solve doing it all from House if you can, simplicity, one less thing to monitor and maintain, Peukert advantage overall.

Yes fat wiring is expensive, but a once off investment.

But 52' is a long haul for a big load. . .

[skipmac]

Originally Posted by Privilege

I’ve got 00 cable running to a bus bar, a run of around 20’ one way. The winch is then supplied by 0 cable for the next 6’.

The winch is a 50 and draws a maximum of about 75amps.

Unless you do find a loose or corroded connection (or a bad crimp maybe?) the cabling is not contributing significantly to the problem. You should only see about 0.3 V drop from battery to windlass with this setup.

Is the battery fully charged when this happens? Any other significant or cumulative loads running at the same time?

If no to both the above then I would suspect the battery is being asked to supply more amps than it likes. I have 650 amp/hours capacity installed and if I run a heavy load on my inverter which draws about 150-160 amps from the batteries, I see a pretty good voltage drop, even when they are fully charged.

[Privilege]

Thanks Pat and to everyone for your input. It seems that I'd be better off wiring the sailing winch to either the start battery (which is much closer) or to put it on a dedicated start battery. My house bank and my starter battery are combined with a combiner anyway for charging. This seems like it should be a fairly straight forward solution for me.
Thanks.

[a64pilot]

Can’t be cableing, unless its the plotter cableing.
Reason is inadequate cable or loose or dirty connections will certainly cause low voltage at the winch, but not the battery.
I am assuming your plotter doesn’t draw power from the winch cable, but has its own power cable.
My boat came with a cheap Raymarine plotter, that I replaced with a B&G plotter with sounder and Radar. Well I was getting occasional low voltage alarms. Made sense as the power required was certainly more than it used to be. I finally ran 10 Ga wire to it, and as I was connecting it, discovered a loose ground. I’m 99% sure that the loose ground was my problem but as I had already run the 10 Ga wire I hooked it up anyway.
Should have checked connections first.

Your winch could be bad and drawing excessive amps, but a big battery like you have, with that size cables should be able to hold 100 amps intermittently easily I would think, cranking amps of an 8D is well over 1000 I think?

[guyrj33]

An 8D battery can easily supply 75 amps. The CCA value is 1450 amps, granted that's at 0 degrees for 30 seconds. But somewhere between 75 amp load and 1450 amp CCA an 8D battery can drive the windlass in question.
It's time to start tracing the connections.

[john61ct]

But if used for more than a second or two, you need to also make sure it is designed for true deep cycling.

Most - like 99.9% - auto / truck sized 12V batteries labelled "deep cycle" or marine, are not, just fraud.

Only a very short list of brands can be trusted in that market, and none of them are available in auto parts or big box retail.

[smac999]

Originally Posted by Cadence

That is a long run, 52'. It sounds like the current drain is just dropping the voltage enough that your electronics do not like it. If you're considering another battery can you add one closer and dedicated to the winch.

Unless the chart plotter is powered at the end of his winch cable. The winch voltage drop is irelivent.

The house feed and winch feed should split off near the battery so this does have an effect on each other.

An 8d battery itself shouldn't drop much with a 50a load.

Measure the voltage at the battery while running the winch. And at the chart plotter input. And compare.

[smac999]

Originally Posted by Privilege

Thanks Pat and to everyone for your input. It seems that I'd be better off wiring the sailing winch to either the start battery (which is much closer) or to put it on a dedicated start battery. My house bank and my starter battery are combined with a combiner anyway for charging. This seems like it should be a fairly straight forward solution for me.
Thanks.

If the winch is used for sailing when the motor is not running I would defiantly not take it off the start battery. That battery should not be drawn Down.

Find and fix the problem. A 50a load should not be shutting off a chart plotter.

[skipmac]

Originally Posted by smac999

Unless the chart plotter is powered at the end of his winch cable. The winch voltage drop is irelivent.

The house feed and winch feed should split off near the battery so this does have an effect on each other.

An 8d battery itself shouldn't drop much with a 50a load.

Measure the voltage at the battery while running the winch. And at the chart plotter input. And compare.

I agree that in this specific case the battery should be able to supply the windlass without a large voltage drop but a large load will cause some voltage drop all the way back to the battery, not just at the load end.

I can see this directly when I run a heater or microwave off my inverter which draws over 150 amps. Even with a fully charged battery bank of 660 amp hour 6V GC2 deep cycle batteries I can see voltage on my battery monitor (which is connected of course directly to the battery bank) drop from 12.6V to below 12V. I only run this big of a load for a few minutes and as soon as the inverter is off voltage quickly pops back up to 12.5-12.6V.

Note, this is based on FLA batteries and can differ with other battery chemistries.

[john61ct]

And that drop does not in itself imply the bank is tired.

But as residual capacity drops

which can be pretty quick, well under 100 cycles, in a setup where chronic PSOC is coupled with very deep discharge levels

a clear symptom will be that drop going lower / faster and recovery taking longer, both charging and just from resting.

So tracking that drop precisely can be one SoH indicator for those not explicitly benchmarking it, in effect informal load testing.

[hpeer]

I have a RM C80 plotted and have the same issue. It doesn’t seem to bother any other electronics. I’ve layed it off to the RM being excessively fussy about the minimum voltage. I have 4 golf cart batteries in a 12 volt bank, they are new, and usually fully charged due to wind/solar charging. I idle the engine around 1,500. I have a Lofrans Falkon windlass, 1700 watt, (rated 210 Amps) but it trips even when letting the anchor down, when load, and current, is very low.

I cope by not turning on the plotter until the anchor is up and turning it off before dropping anchor. PITA. The C80 has this weird double ended power feed using the seatalk cable. IIRC it also lowers the radar and other instruments which makes the loop very long. Not a great arrangement.

[Cadence]

Originally Posted by smac999

Unless the chart plotter is powered at the end of his winch cable. The winch voltage drop is irelivent.

The house feed and winch feed should split off near the battery so this does have an effect on each other.

An 8d battery itself shouldn't drop much with a 50a load.

Measure the voltage at the battery while running the winch. And at the chart plotter input. And compare.

I guess I made it sound that way. I wasn't saying line drop to the winch was causing the voltage drop at the plotter. Two separate thoughts. Apparently the winch is drawing enough at the battery to cause the plotter to drop out. The other thought was possibly the winch would be happier without any possible drop caused by a long run. I would also agree that if in fact it is only a 50A draw an 8D should not drop much. Something is missing possibly the state of battery charge? A health 8D will let you turn over a 6-71 for quit awhile and that I believe is more draw than his winch. It could be as simple as the plotter is only getting a reduced voltage to begin with as the result of a corroded connector.

[john61ct]

Yes I believe the specific model and age of the bank have not been revealed yet?

Another approach could be isolating the sensitive electronics from the bank powering the big loads, likely smaller and closer to House.

[CarlF]

I blame the Raymarine chartplotter for crashing on a voltage sag. Probably would have cost them $0.10 to make it more tolerant of the realities of a sailboat.

As an easy experiment, get some wire - 14 gauge would be plenty big - and connect the electronics circuit back to the battery posts. (do both positive and negative and be sure it still goes through a breaker or fuse) If it still crashes then your problem is the battery not the wiring.

If it doesn't crash you could just add a two contact terminal to the battery and make it permanent. Blue Sea Makes a great one that includes a fuse for each connection.

If it does crash, first clean and check all of the cable connections. If that doesn't fix it, you could get another combiner and a small battery just to power the electronics. You'll have to figure a way to keep it charged when you are sailing. Presumably your solar would do that.

[hzcruiser]

Originally Posted by Nicholson58

Good advice on terminals and the engine. We never operate the windlass without the engine. I want to be sure we have control before drifting randomly as well as making sure there is enough powere to start.

I guess a lot of people here, including me, automatically thought "windlass" even though you said "winch". Mainly because an electric winch should never cause such issues if it's in working order and wired properly.


So does the chartplotter resets even when there is modest load on the sheet winch or just under maximum load?
If your wiring is up to scratch, like you said, then yes, an additional battery in parallel will reduce the voltage sag.