Ann-Marie

Consider the Trollbridge24. It automatically puts the 24 volt batteries in parallel for charging so you can use your existing charger. It switches to series when you start your trolling motor. A big advantage is you can also charge the 24 volt trolling battery from your 12 volt alternator when the main engine is running. This will extend trolling time and extend battery life.

THE ULTIMATE SOLUTION TO TRAILER WIRING PROBLEMS. I mounted the license plate, stop lisghts, clearance lights turn lights etc, all on a 2X4 and made a clamp that would attach it to the trailer or the stern of the boat. A flexible cord plugs into the truck. No wiring on the trailer to give problems. (May not be quite legal to include the license plate but no one ever gave me any trouble.) You hang it on the trailer or boat when going to move, take it off, roll up the cable and put it back in the truck when you arrive. No need for waterproof fixtures, no burned out bulbs from the water, no rusty connections.

Yes running in parallel is OK for unmatched batteries. To answer your earlier question about battery life, the biggest killer of batteries is over discharging. For maximum battery life they should be discharged no more than 50%. I forget the actual numbers but its something like for every 10% below 50% you cut the life in half. So a 5 year battery at 50% is a 2.5 year at 40%, 1.25 at 30%, 8 months at 20%, 4 months at 10% and 2 months fully discharging. So if you were to add your extra battery up front you could more than double the life by minimizing depth of discharge and actually save money over replacing one a number of times.

BEFORE you buy new batteries, put the old ones back and test again. If you had a bad battery connection it would give the same symptoms and just substituting batteries may have cleaned up the connection.

Yes that appears to be standard Double Pole Double Throw switch, or frequently called a DPDT switch. If you can get one with "Center Off" it can also be used to disconnect the motor. You need to purchase one that is rated for the current drawn by your trolling motor or preferably higher for maximum life. Copy the wiring exactly from the old one before removing, if you make a mistake putting them back you can blow fuses or melt wires. I found a 30 amp one HERE for about $35. But many motors draw more than 30 amps. You can get an automatic switch for about $100 that automatically switches between 12 volts for charging and when your motor is set to 12 volts, or 24 volts when the motor is set to 24 volts. They are rated for trolling motors up to 80 amps.

Not sure what you mean by a "2/12V - 12V - 24V" switch. We make an automatic "Trollbridge24" switch that will change the batteries from parallel to series. The batteries are normally in parallel so you have 12 volts going to the motor supplied by both. If you switch the motor to 24 volts, the automatic switch will put the batteries in series so both are now giving you 24 volts. If that is not what you mean, I'll need a little more information.

Agree, you CAN provide precise controls matched to the load characteristics but since those specifications are so load dependent protection is usually provided by the manufacturer IN the load, not as a separate external fuse or circuit breaker. If it is a "motor control" with only a single specific motor on the output side you are correct, they have thermal and magnetic sensors matched to the load time constants and ratings. These can detect things like locked rotor and remove power befor the target self destructs. It is rare in small boats that an individual load would have a dedicated fuse or circuit breaker that would be precise enough to protect the device from overload without considerable research and expense. In general the discussions here typically refer to a distribution bus carrying multiple loads rather than trying to match individual loads.

Thanks Team_Dougherty, couldn't have said it better. If a load is relying on a cirucuit breaker or fuse for protection it is already dead by the time the breaker trips. Keep in mind the rating applies to the lightest gauge anywhere in the circuit. If you have a heavy gauge main line that branches to a light gauge feed to an instrument, then that light gauge needs its own protection since the main one could supply enough power to melt the small wire without tripping.

You may also need a larger battery. The biggest killer of batteries is discharging too deeply. And the final blow is trying to start an engine on a dead battery, that can kill it in seconds. A larger battery will have more power remaining at the end of the day for starting an engine and the depth of discharge will not be so deep giving much longer life. If non-startng battery loads are running it down and being able to start is very important, then you can use a Combiner100 http://www.yandina.com/c100InfoR3.htm between the starting battery and a dedicated "house" battery to keep them separate automatically for discharging but allow both to charge from a single output shore power charger or from the alternator on the motor.

And it is no advantage for avoiding property taxes. CALIFORNIA WILL GET YOU.

A Trollbridge24 will let you charge your 24 volt battery from the 12 volt alternator in your motor and it also equalizes the two batteries so they discharge evenly when running 12 volt items off one battery.

Yes you can put in a larger fuse to run both. Fuses do NOT protect the instrument from failure if it draws too much current. If it draws too much current it has ALREADY failed. Fuses protect the wiring and/or the failed instrument from melting insulation and catching fire. The downside is that if the fuse blows you lose both.

And check every fastener you use to make sure it is stainless. I just about completely rebuilt one seat replacing steel fasteners with stainless. It is hard to believe that manufacturers of marine products will save a few cents but ruin their reputation making products that have no business on a boat.

It can happen that the internal battery connections to the posts are bad, a load check at a battery store will diagnose it for you. If both posts are hot it seems too much coincidence for dirty connections.

For about 60 you can get a Combiner100 to connect between the starting battery and a house battery that is on the charger. That way the starting battery will get topped off with the existing charger. You have the added benefit that when the engine is running the alternator will maintain charge on the house battery since the Combiner100 is bi-directional

You don't need a 4 bank. A good size 2 bank will do the job. Keep in mind that you can use a Trollbridge24 which would allow you to use a cheaper single output 12 volt charger and would also allow your outboard engine alternator to charge the 24 volt battery. Then you can also use 12 volt charging line from the tow vehicle to charge all the boat batteries.

IRRESPECTIVE OF THE THEORY, LOOK AT THE PRACTICAL SIDE. 1. A battery is fully charged at rest at about 12.8 volts. If your BIG battery and your SMALL battery are in parallel at 12.8 volts then both are fully charged. 2. You apply your lamp load to both batteries and pay no attention to how much current each supplies. Voltage starts to drop over time until it gets down to 12.2 volts. 3. DID the smaller one get discharged more than the big one? IF it was discharged MORE it would have a lower voltage. 4. BUT THEY ARE IN PARALLEL. This means they are at the SAME voltage. How are you going to discharge the smaller one (to a lower voltage) WITHOUT discharging the big one? You can't have the smaller one at a lower voltage (discharged more) than the big one too, they are tied together. The same applies to charging. When they are in parallel and get to 14.2 when a charger would cut back to maintenance stage, HOW could the smaller one be OVERCHARGED without overcharging the BIG ONE TOO? To over charge the small one its voltage would have to get above 14.2, but so would the big one and the charger will cut them both back to maintenance.

Your basic assumption is wrong. You say But you won't draw 25 amps from each battery. You will draw 66.6% from the 100amp hour battery and 33.3% from the smaller one. This is because the amount of current is governed by ohms law, current = Voltage / Resistance. The voltages have to be the same because they are in parallel but the resistance of the small one will be TWICE the resistance of the large one so it will only supply half as much current. The resistance is inversely proportional to the surface area of plates in the battery and the 100 amp one will have HALF as much as the 50. Same happens when charging, twice as much current will go into the 100amp-hour battery as will go into the 50 amp hour so the process is self regulating for charge and for discharge. The reason some advise matching size and age is to get maximum CAPACITY out of your battery installation and maximum battery sales. If you have a 50 amp capacity that is brand new and a 100 amp capacity that is 50% dead, then your total capacity is only 100 amp-hours. But if you are content with the final capacity it is no reason to throw away an aging battery. If you need full capacity, then replace them frequently. Also with batteries in parallel, if one dies it won't damage the other one but it will drag the charge and voltage down so you have minimal remaining capacity. If you want maximum time between failures then that is a reason to use matching batteries and replace them both as soon as they get old. I prefer to get the maximum I can out of my batteries.

This is an incorrect assumption but very common. When batteries are in parallel you can't discharge one more than the other because they are at the same voltage = they are CONNECTED TOGETHER. To discharge the small one more than the big one would mean it would have to be at a lower voltage but that can't happen. Same when charging, you can't overcharge the small one without overcharging the big one. If the small one gets to full charge = full voltage, then the big one must be at the same voltage and also fully charged.

I agree. complain to the charger manufacturer and get a replacement if under warranty. It should not be possible for a battery to damage a charger if the charger is designed correctly.

If your charger has adjustable charging characteristics all you need to do is select the AGM or Sealed battery setting. That is the most conservative setting to protect sealed batteries but it will still charge all batteries OK. The only difference is it may take 10 minutes longer since it will limit how high the voltage can go to push current in. Although you can mix size, age, chemistry etc., for batteries used in parallel, it becomes important to match the batteries in series for 24 or 36 volt motors as closely as possible. Not only is the chain as weak as the weakest link when in series, the stronger links can damage the weaker ones and reduce battery life considerably.

Although it is good advise to wash the batteries down to minimize corrosion, the amount of power lost through the surface conductivity is too small to measure. Battery capacity is measured in ampere-hours, that is the amount of amps being drawn multiplied by how long it flows. Although a volt meter can measure "3 or 4 volts" that says nothing about how much current is flowing. To get a reading on a modern voltmeter only takes a few millionths of an amp. Even if the amount of current on the surface was 1,000 times as much that would still only be 1/1000 amp so it would take 3.5 years just to waste 1% of the battery capacity.

I just used regular trailer lights, no waterproofing. I mounted them on a 2X4 along with the trailer license plate. It has a 30 ft flexible cable that plugs into the truck so there is no wiring on the trailer. On my boat I had a rudder so the rudder was pulled out and a pin on the 2X4 held it in place when driving. An extra hole drilled in the trailer held it there if running without the boat. When you get to the ramp, just take everything off and put it in the back of the truck.

Charging at the 2 amp setting is going to take at least 5 to 7 days to charge it. Give it a real charge and try again.

Many of the symptoms you describe correspond to batteries with a dead cell. Take the batteries to a load testing place and get them tested. They fail to charge because the voltage is too low and the reading is unreliable. They rapidly show full charge because with the dead cell the battery voltage rises very quickly when it won't accept a charge and it looks like it is 100% charged.