Your Resident Electrician for all your electrical questions!
- Thread starter Young Frankenstein
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In some cases, a simple voltage measurement work. You have to see the pattern of voltage drop as the battery drains. If its somewhat linear, you are good. Else you have to rely on internal resistance and to measure that you'll need an appropriate load and measure its current instead
powers2001
started reefing 1999
Since the Centech power supply in the video has a USB port, could I keep something with low power consumption plugged into it where the trickle charger could keep up with battery discharge. Something like a tablet?
Paul B
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Unfortunately you can't measure if a lead acid battery is good or not with a simple volt/amp/watt test. A dead lead acid battery will still read 12 volts unless it is like really dead, dead.
There is a load test for testing them, but they are not cheap.
There is a load test for testing them, but they are not cheap.
powers2001
started reefing 1999
So if I know how much juice my trickle charger can charge and it keeps up with the amount of "juice" that my tablet uses, I'm good?
Brew12
Electrical Gru
Not really, that load is too small. If you would check it with something like this 2 to 4 times a year, you would know if it were reliable.
https://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html
powers2001
started reefing 1999
Could I leave that hooked up to the battery all the time?
Brew12
Electrical Gru
Definitely not.
The problem is that to find out if a led acid battery is good, you need to discharge it at a high rate. Otherwise, as Paul B said, it could be on a trickle charge or slight discharge for a months and look to be working just fine. Then you put a load on it and it dies in minutes.
Unfortunately, there has not been a continuous battery health monitoring system developed yet.
Shaun Sweeney
Active Member
You want to read volts. Amps would tell you your usage but volts will tell you what is left. Also, if you are using a wet cell battery, they should NEVER be discharged to less than 65% of capacity. Use deep cycle batteries as opposed to starting batteries which have cranking amps but less overall capacity to store. And remember, wet cell batteries produce an explosive gas when charging but not when discharging. So, the bottom line answer, install a voltmeter (that you can just turn on momentarily) and read the charged voltage. Multiply that time 0.65 and try to stay above that number at all times.
FYI ... you can get "smart" battery chargers that will knock the sulphates off the plates from time to time. Used properly, they will extend the battery life almost indefinitely. Lastly, keep an eye on your water levels and use distilled water only.
FYI ... you can get "smart" battery chargers that will knock the sulphates off the plates from time to time. Used properly, they will extend the battery life almost indefinitely. Lastly, keep an eye on your water levels and use distilled water only.
Shaun Sweeney
Active Member
Stay away from load testers unless you are suspicious that the batter is damaged or past it's use by date. As they name suggests, they place a significant load on a battery to give you a reading.
powers2001
started reefing 1999
I was told to use a sealed battery. Is that a wet cell or deep cycle?
Shaun Sweeney
Active Member
There are different kinds of sealed batteries. Gel and wet cell but unless it is an AGM battery both are still really wet cell. unless you have a serious concern about ventilation, I'd stick to plain old deep cycle wet cell batteries that you can open and check the electrolyte on. As to ventilation, I have 5 deep cycle batteries in the midship hold of my boat with minimal ventilation and I am not concerned about the off gassing. I had 24 in my previous boat and still wasn't concerned about the gas but I did put my ventilation on if I was hitting them hard with a maintenance charge.
Haven't seen any discussion on wiring but keep in mind that you should minimize the distance from the batteries to your inverter as low volts (like 12) means lots of amps when there is a call for power. Don't be using light gauge wire between batteries and inverter.
Also, keep a maintenance charger on the batteries at all times and never store the batteries on concrete.
Haven't seen any discussion on wiring but keep in mind that you should minimize the distance from the batteries to your inverter as low volts (like 12) means lots of amps when there is a call for power. Don't be using light gauge wire between batteries and inverter.
Also, keep a maintenance charger on the batteries at all times and never store the batteries on concrete.
powers2001
started reefing 1999
Could I keep a SEALED car battery in a battery box with the top on or off during use?
Victoria M
5000 Club Member
I have a question for electrical stuff. My husband added a dedicated circuit to our home circuit breaker box. It has 8 outlets at the basement sump, 3 lights in the fish-room, and 2 outlets for my QT. Can more outlets be added? or can I add a DJ switch/plug bar to manage my sump equipment?
Brew12
Electrical Gru
This is a tough question to answer. The NEC (National Electric Code) does not specify a maximum number of circuits for a feeder breaker. A good rule of thumb is that each outlet counts as 1.5A and that you can load a breaker up to 80%.
If he installed a 15A breaker that would limit you to 12A (80% of 15) or 8 receptacles. With a 20A breaker you can install 10 receptacles. Based on this, you already have more than is recommended. This thumb rule is also adopted as local electrical code in some areas. The only way to know that would be to call your local inspector or a knowledgeable local residential electrician.
Adding a DJ switch or plug bar is always a good option.
Victoria M
5000 Club Member
Thank you for your help. I appreciate the thoughtful answer.
Victoria M
5000 Club Member
And hubby just said it was a 20A and he thinks only the receptacles are dedicated. We will check again later. It was 7 years ago...
Brew12
Electrical Gru
Yup, it does seem odd. There are some other rules you need to apply when it comes to receptacles but nothing limiting the number in a branch. I think that is why many areas have adopted more stringent number requirements as part of their local building codes.
Glad to help, just wish I could give you a more definitive answer!
I like the 12 device limit, however, now that LED lights are about it kind of sucks that they count against that number still... For instance, adding 12 LED pot lights counts as one cct, even though the amp draw is going to be 1 amp. :/
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