I’m planning on replacing my battery within the next week and have studied the do’s and don’t of battery maintenance through this site over the past few months. I have two outstanding questions that hopefully someone can help me with. 1. How may Amp Hours did I use – what’s the quickest way for me to gauge how many AH were used during a trip – sure I can calculate that I used the stereo for 2 hours and the lights for ½ hour but is there a quicker way and come up with the AH used. As an alternative, can I check the voltage on the battery and assume that if the voltage is @ 80% then I used up 20% of the AH? 2. How long to run the Outboard to Recharge – I don’t have shore power, so I’m stuck with 2 VW solar panels that give me a trickle charge and running my Mariner 9.8 2 cycle outboard. When running at idle, how do I calculate how long I need to run the engine until the battery is charged to 100% - do I use the volts as an indicator and wait until the volts reflect 100% or is there a more intuitive way to calculate how long I need to run the engine at idle until the battery is recharged. Thanx for all the assistance in advance,
Recharge Time
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Check your charging voltage
Most of the outboards I've seen are designed to charge at normal operating RPMs, not at idle. Check the charge voltage vs. RPMs that you're getting from your outboard. You might not be getting enough voltage to charge batteries at idle, and surely won't get enough to bring the batteries to full charge capacity.
Most of the outboards I've seen are designed to charge at normal operating RPMs, not at idle. Check the charge voltage vs. RPMs that you're getting from your outboard. You might not be getting enough voltage to charge batteries at idle, and surely won't get enough to bring the batteries to full charge capacity.
Charging with outboard
You need to check the specks for that engine. Most small outboards have very small alternators. Usually just enough to run nav. lights. The models made for sailboats might have slightly larger alternators, but still not very large. Your owners manual should give you the alternator output and at what RPM it max's out. But like the previous poster stated, at idle it is probably not going to do much. If your solar panels will get the battery up to a full charge between trips, and you don't use a lot of power, you might be fine. As for batteries, many will disagree, but I use the Wal Mart Max deep cycle batteries. They are 105 AH rated, priced right and I have had very good luck with them.
You need to check the specks for that engine. Most small outboards have very small alternators. Usually just enough to run nav. lights. The models made for sailboats might have slightly larger alternators, but still not very large. Your owners manual should give you the alternator output and at what RPM it max's out. But like the previous poster stated, at idle it is probably not going to do much. If your solar panels will get the battery up to a full charge between trips, and you don't use a lot of power, you might be fine. As for batteries, many will disagree, but I use the Wal Mart Max deep cycle batteries. They are 105 AH rated, priced right and I have had very good luck with them.
My OB won't charge sufficiently at idle
And I use it for such short times that it's just not practical to rely on it for charging. My boat's much the same size as yours, so for what it's worth, here's what I do: I replaced the old battery with an AGM. It requires practically no attention, but best of all, it holds a charge when not in use for a long time. I installed a small Guest charger connected to a power cord inlet in the cockpit locker. When I need to, I plug in to shore power to charge. With the minimal power requirements on my boat (lights, VHF, depth, 12 volt inlet & a portable inverter for charging rechargeable batteries for cell phone, etc.), this is sufficient. Since you don't have shore power, perhaps a portable generator would be useful - certainly more efficient than the outboard. FWIW, Tricia Freedom 25 "Muse"
And I use it for such short times that it's just not practical to rely on it for charging. My boat's much the same size as yours, so for what it's worth, here's what I do: I replaced the old battery with an AGM. It requires practically no attention, but best of all, it holds a charge when not in use for a long time. I installed a small Guest charger connected to a power cord inlet in the cockpit locker. When I need to, I plug in to shore power to charge. With the minimal power requirements on my boat (lights, VHF, depth, 12 volt inlet & a portable inverter for charging rechargeable batteries for cell phone, etc.), this is sufficient. Since you don't have shore power, perhaps a portable generator would be useful - certainly more efficient than the outboard. FWIW, Tricia Freedom 25 "Muse"
2 great books on 12 volts
There are 2 books on living with 12 volts. They are by David Smead and Ruth Ishihara published by RIDES Publishing Company. The books' titles are: 1. Living on 12 Volts with Ample Power. 2. Wiring 12 Volts for Ample Power. These books will help you figure out how many amp hours you need, how to configure it, wire it, charge it, use it. Some of the topics may be more than you want to know, but the books are great for reference. I've had these books for over 15 years, and I still find them useful.
There are 2 books on living with 12 volts. They are by David Smead and Ruth Ishihara published by RIDES Publishing Company. The books' titles are: 1. Living on 12 Volts with Ample Power. 2. Wiring 12 Volts for Ample Power. These books will help you figure out how many amp hours you need, how to configure it, wire it, charge it, use it. Some of the topics may be more than you want to know, but the books are great for reference. I've had these books for over 15 years, and I still find them useful.
Let a meter do it for you...
The easiest way to know what's going into and out of the battery is with an amp-hour meter such as the Xantrex Battery Monitor, successor to the popular Link 10, which was known as the e-Meter in its early days. Meters like this measure current going in either direction across a shunt in the battery(ies) negative connection, and integrate it over time. They also consider charging efficiency (i.e. you have to put back in about 10% more than you take out), as well as Peukert Effect (high level discharge, such as that from an inverter, use much more capacity than the amps X hours would indicate). AGM batteries are a great idea in an environment with limited charging. They have less than 25% of the self-discharge of flooded cells, plus they have a much lower internal resistance and ensure as much of the limited charging capability as possible is used. There are many more advantages to AGMs, but I won't go into them here.
The easiest way to know what's going into and out of the battery is with an amp-hour meter such as the Xantrex Battery Monitor, successor to the popular Link 10, which was known as the e-Meter in its early days. Meters like this measure current going in either direction across a shunt in the battery(ies) negative connection, and integrate it over time. They also consider charging efficiency (i.e. you have to put back in about 10% more than you take out), as well as Peukert Effect (high level discharge, such as that from an inverter, use much more capacity than the amps X hours would indicate). AGM batteries are a great idea in an environment with limited charging. They have less than 25% of the self-discharge of flooded cells, plus they have a much lower internal resistance and ensure as much of the limited charging capability as possible is used. There are many more advantages to AGMs, but I won't go into them here.
Xantrex link meters
I had the same problems with my Catalina 27 as you do. The OB was spec'ed to charge at 6 amps, but I never knew how much power I'ed used. I spent about $300 and installed a Xantrex Link 20, which tells you current voltage, current amps going in (or out) of the battery, total amps used, how many amps are left in the battery, and how many hours that represents at the current rate of usage. The Link 20 monitors two banks of batteries. (You can get a Link 10 to monitor one bank for less, or other meters that provide a little less info for less $$.) Doing the calculation thing is always inaccurate, because of hidden errors, like power needed to run the station memory in the stereo, or errors in estimating amps used by various appliances. My OB alternator, spec'ed at 6 amps also typically only puts in about 2-3 amps if the battery is not far down. (The more highly charged the battery is, the less amperage actually actaully goes in, and the longer it takes to charge.)
I had the same problems with my Catalina 27 as you do. The OB was spec'ed to charge at 6 amps, but I never knew how much power I'ed used. I spent about $300 and installed a Xantrex Link 20, which tells you current voltage, current amps going in (or out) of the battery, total amps used, how many amps are left in the battery, and how many hours that represents at the current rate of usage. The Link 20 monitors two banks of batteries. (You can get a Link 10 to monitor one bank for less, or other meters that provide a little less info for less $$.) Doing the calculation thing is always inaccurate, because of hidden errors, like power needed to run the station memory in the stereo, or errors in estimating amps used by various appliances. My OB alternator, spec'ed at 6 amps also typically only puts in about 2-3 amps if the battery is not far down. (The more highly charged the battery is, the less amperage actually actaully goes in, and the longer it takes to charge.)
charge it
Tony; Get a Honda EU1000 generator. It the quickest and easiest way to fulfull your minimal needs.
Tony; Get a Honda EU1000 generator. It the quickest and easiest way to fulfull your minimal needs.
solar panel ?
Like Larry, I also have the same Honda generator and also find it an asset on the boat and at home, in the event of a power failure. You can run you fridge or freezer with it. Some people at my club have added a solar panel to keep the battery topped-up for the outboard. I see more of them each year, so somebody must be happy.
Like Larry, I also have the same Honda generator and also find it an asset on the boat and at home, in the event of a power failure. You can run you fridge or freezer with it. Some people at my club have added a solar panel to keep the battery topped-up for the outboard. I see more of them each year, so somebody must be happy.
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