Charging issues

[Donald Tyson]

Took a shakedown cruise in the Chesapeake over the weekend and enjoyed the sunshine and warm weather. I hope you all enjoy your holiday weekend as well.

I had some significant issues with the batteries and need to learn the cause. If I turned on the batteries to All then the shore power would recharge my starting batteries. I know this because, of course, the boat would start but I'm not sure it was charging the house batteries. If I would leave the refrigerator on the batteries soon be died in spite of the solar panel and shore power working hard to recharge. The inverter was on and showed a good signal. I am not sure what the DC inverter switch does but I believe it allows certain items like the Fridge to toggle back and forth from AC to DC as needed. Once I would turn on the fridge the starting batteries would soon be dead. If I would have turned off the DC Inverter switch would the fridge have switched to the house batteries.

I have the impression that my problem with the dead batteries lies somewhere with how I'm turning the wrong switches on and off or the Fridge being bad or the house batteries being bad.

I'm land bound until I know I am doing the right thing. Dead batteries are too scary to "chance it".

The surveyor told me when he surveyed the boat that, although the batteries were performing well, I should replace them as soon as practical. So I guess there is a chance that one or both of the house batteries are dead but I don't know how to tell.

I don't have any handheld meters to use for diagnosing these things and could benefit from some suggestions.

Penny for your thoughts...

[Tom Hruby]

Don,
Here are some suggestions for trouble shooting.
1. Get a DC clamp meter that measures DC current without unhooking any cables. These run about $50. Make sure it is for DC not AC.
2. With everything turned off, check to see if there are any currents leaving the batteries. This will confirm if you have any slow leakage in your system.
3. Turn on your fridge and measure the current to see if the fridge is the problem (internal short that is draining the battery). Then determine which battery (house or starting or both) is powering the fridge by putting the clamp on the (+) wire leaving the battery.
4. Turn your different switches on and off to document how the power is moving in the boat.
5. You can also use the meter to document how the system is charged.
Hope this helps.

[thataway]

Yes, first but a digital volt ohm meter. I like the Klien CL 800 beause it does AC and DC up to 600 amps. It has maximum reading hold, but does not do true inrush current. This is more for the advanced boatowner, or some professonals. However it is $130 and has far more features than you will probably ever use. The best are Fluke. They are even more expensive.

Any cheap Home Depot or Lowes meter will work for you. General is one brand I have, (about 6 various meters) and then a collection of analog, incuding the one my dad used the in design and testing of San Onefre Nucular station. (and a lot of other major hydro and steam projects for Edison International)

Klein MM325 has most functions and is $35, or $40 for a Kein polarity teste, AC live circuit tester--over all probably the best deal...These only measure 10 amps of DC power (there are ways to measure more, but beyond what you need to know. Be certain that any meter has a 10 amp separate plug in; you may need to use that later as you gain expertise. I feel every boat under way needs to have a good ditial multimeter in its tool kit.

how to use a multimeter book

J

[Tom Hruby]

More thoughts:
The DC amp meter will also usually have a volt meter. Measure the voltage of your battery during use. If the voltage drops significantly, it is your battery that is the problem. When I was using lead acid batteries I also had a resistance battery tester I got at an auto parts store (or Harbor Freight). The smaller units put a 50 -100 A current across the battery and will tell you if the battery is bad (too high a voltage drop).

[ssobol]

[Donald Tyson]

Tom did you mean DC Amp meter or did you mean Clamp meter.

Dr.Bob, I downloaded the book. I'm picking up a 325 Kline soon.

SSobol, I have two batteries for starting and two batteries for the house.


All,
Tomorrow I will clean out the boat for access and examine exactly what I do have.

[gulfcoast john]

Hi Don,
Your AC/DC fridge will automatically run on AC power when that is available, and automatically switch over to run on 12v DC from your battery when no AC power is feeding it. You should find a circuit breaker for the fridge on your AC distribution panel, and a 10A fuse for the fridge on your DC fuse block (likely under the helm). If it’s not labelled, open the fridge door with the AC breaker off; the fridge light will stay on running on your battery. Start pulling unlabelled fuses; when the fridge light goes out, you have discovered the fridge 12v fuse. Label that on the fuse box cover.

To over simplify (which Bob rightly critiques me for), the power hog fridge compressor runs on DC. An internal module converts incoming AC current to DC, then feeds it to the Danfoss compressor. Converting the AC to DC wastes power, but who cares, the AC input is inexhaustible.

Your inverter converts precious DC power to AC, but VERY inefficiently…20% of the 12v output is wasted or turned into heat in that process.

SO, when you switch the battery selector to ALL with your inverter ON, you are sucking limited and precious DC amps out of your batteries, then wastefully converting those amps into AC amps, then feeding it to your automatic AC/DC fridge, which wastefully converts them back into DC amps to feed the hungry Danfoss DC compressor.

Also, true START batteries are engineered to provide a huge glob of amps for a few seconds to an engine starter motor. It’s such a huge glob that it’s the only circuit on a boat that does not even have a circuit breaker or fuse and still meet code (OK, code allows the bilge pump circuits to not require protection, but all my 13 trailer boats were wired with protection). Your START batteries will die early if asked to feed the DC Danfoss compressor for hours on end.

The batteries will have a mfg date code on them somewhere. Your surveyor found it. Average quality lead acid batteries reliability tends to degrade by four years old (from birth, not from purchase date). In your case, I contend that replacing them with flooded lead acid is a reasonable path if weight/size is not an issue. The 1860 technology is well proven, and a group 31 on sale runs $120 each. I previously favored Odessy and Northstar AGM, but after six years, with the Northstars still load testing fine, I replaced them when planning a Georgian Bay trip. They are not cheap.

https://www.interlightus.com/products/northstar-nsb-agm31.html?msclkid=fde12280f2ca176648724aeebd15f581&utm_source=bing&utm_medium=cpc&utm_campaign=PMax%20-%20Group%20NA%20%26%20ROAS%20%3C%205&utm_term=2325260935156096&utm_content=Asset%20group%201


You’ll be closer to civilization for the first few years. We are tucked into a remote cove on the UP on Lake Michigan (see Cat O’ Mine on NEBO). I understand the technology and have no fear of an inaccessible microprocessor in a lithium battery causing a ‘dark ship’ event here.

I suggest that four 12v batteries on a CD22 may be excessive. I’d suggest two FLA on sale group 31 deep cycle, if you have the room, one for starting the engines that meets ALL the specs in the engine manual, the other as House. Start each engine separately to reduce the load. Invest your savings in a Victron 702 or Bob’s equivalent battery monitor and maybe a solar panel. Then you can combine them (ALL) at anchor and monitor to not discharge over 50%. Swap the House and Start positions annually, Start battery leads a too easy life. I’ll convert to Lithium House when a true drop-in replacement with a ten year warranty is available from a company that has been in existence for ten full years.

Don’t fret, you’ll figure it all out like the rest of us. PM or call if my assumptions about your fridge model or start batteries are wrong. Safe travels!

John