You don’t want a battery tester, you want a battery monitor. From $ to $$$ and simple to complex: A digital voltmeter is a great start and you can learn a lot from just this. They can be had from maybe $20 on up. There are good analog meters, but the difference between 12.5 and 12.6 or 14.0 and 14.2 is a big deal and it is rare to be able to see that on an analog meter. Add a good digital bi-directional ammeter and now you can see current going in or out. Once again there are analog meters, but it is hard to see the difference between 2 and 3 amps on a 100 or 200 amp scale. This is what I have – digital volts for the start battery, digital amps and digital volts for the house battery. After a while you get a good feel for what is normal. The next step up is an amp-hour meter. These keep track of amps in and out and try to give you a state of charge. For example, if you run a 5 amp load for 10 hours it should say -50 AH and if you charge at 5 amps for 10 hours it should count back up to zero (or it might count down from the programmed capacity – say 100 down to 50 and back up to 100). These are usually pretty expensive. I used to sell them and have mixed feelings about these units. The problem is Peukert’s Law (https://en.wikipedia.org/wiki/Peukert%27s_law). 100 amps for 1 hour is not the same as 1 amp for 100 hours on the discharge side, the battery will go dead faster at 100 amps, and the charging is not 100% efficient either. The meters use various formulas to try and stay accurate, but in my experience they always drift off and lose the idea of where full is. Balmar has a proprietary metering system that does not use current shunts, but somehow keeps track anyway and by all reports I have read actually works better. YMMV – never tried one – but here you go: http://www.balmar.net/?page_id=15245
I have a lot of fun with kids on the boat and the meters. Depending on my mood, they either have to keep the ammeter in the positive range while they play with their electronic toys or at least keep the voltage above a certain level. It keeps them motivated to move the solar panel and they learned to charge their toys when the engine is running LOL. Joe Coquina C&C 35 MK I From: CnC-List [mailto:[email protected]] On Behalf Of Franklin Schenk via CnC-List Sent: Monday, October 03, 2016 16:12 To: [email protected] Cc: Franklin Schenk Subject: Re: Stus-List Battery tester I like the KISS method. Use a multimeter to check the battery when fully charged. It should be about 12.5 volts. Check it when the engine is running and it should be 13.5 volts or higher. If the battery cannot be recharged to 12.5 volts, it is probably bad. That is when you pull it out and take it to a battery store. This has worked for me for more years than most of you guys have been alive,. Frank On Monday, October 3, 2016 1:21 PM, David Knecht via CnC-List <[email protected]<mailto:[email protected]>> wrote: I would like to be able to monitor the health of my batteries without having to haul them off the boat. I looked at Amazon and found many battery testers (load and conductance) from $15 to $250. Has anyone tried any of these devices and have any suggestions on what to buy or not to buy? Dave Aries 1990 C&C 34+ New London, CT [cid:[email protected]] _______________________________________________ This list is supported by the generous donations of our members. If you like what we do, please help us pay for our costs by donating. All Contributions are greatly appreciated!
_______________________________________________ This list is supported by the generous donations of our members. If you like what we do, please help us pay for our costs by donating. All Contributions are greatly appreciated!
