Charging issues

Donald Tyson · Joined: 24 Jul 2023 Posts: 570 Photos: Thistle

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 · Posted: Tue Jul 08, 2025 3:45 pm Post subject:

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 · Posted: Tue Jul 08, 2025 3:45 pm Post subject:

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 · Posted: Tue Jul 08, 2025 3:52 pm Post subject:

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 · Posted: Tue Jul 08, 2025 5:58 pm Post subject: Re: Charging issues

Donald Tyson · Joined: 24 Jul 2023 Posts: 570 Photos: Thistle

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.