Ok, Please be patient, I know you've probably covered this before, But I need a little advice. I have a 24 volt setup for my trolling motor and a battery for my motor(cranking battery). I want to buy a on- board charger and not sure what to buy. Read in past post that the BassPro Shop made by ProMariner is a good charger. Do I need a 2 bank ( 1 hook-up for the cranking battery and 1 hook-up for the two deep cycle batteries) or do I need a 3 bank charger (1 hook-up for the cranking battery and 1 hook-up for EACH deep cycle battery)? If you have the TM batteries wired together, will they charge if you just hook-up to one of them? If not do you have to seperate them before you charge them? What size charger would you recomend, 8,10,15, 20 amp? Can you leave the charger hooked up all the time and not worry about it? Even for extended periods of time, like over the winter or should you charge it and unplug it for the winter? Should I charge the cranking motor batteries everytime I charge the TM batteries since they would be hooked-up to the onboard charger also or would it hurt it? My motor charges it somewhat when it's running, but I don't make very long runs with it. Well I think I've covered all my questions and thank you for any help you can give me.

Doug

Personnaly, I would use a three bank charger. Your motor will almost never keep the cranking battery fully charged.  Plus when stored, the three bank will maintain all three, otherwise you would have to have a maintainer for the third battery.  With most any good onboard charger, you should plug it in and leave it while the boat is parked, just be sure to maintain the batteries, clean, dry  and water in them.

The size depends on how fast you want to be able to charge them.   If you have eight to ten hours between trips, a six amp per bank ProMariner (BPS or Cabela's brand made by them) should work fine.  If you need quicker charging time, then you should look at the ProMariner ProTourny 300.   I know this next comment is going to ruffles feathers with the Dual Pro supporters and others but the ProMariner six amp per bank will actually charge as fast if not faster than the Dual Pro 10 amp per bank.

As for connecting to the battery, how the batteries are connected in the boat has no bearing on how the charger will connect to them.  The charger will connect to each individual battery.  No matter how batteries are connected, each battery is still only a 12 volt battery as long as a charger is connected to that battery.

Thank you for the reply! I've read other post by you about batteries and was hoping you would be one of the persons responding! Couple more questions please. BPS list only one 3 bank charger--says XPI 5/5/5, DC systems 12/24/36 15 amps. Is this what I would want? I assume it's 5 amps per bank. Don't know what the 12/24/36 means.

Also, does it hurt the battery if you don't real use it that hard and it's not drained down that much, to keep putting it back on the charger? Will they take a memory? Somebody told me this and did not know if it applied to these type of batteries. I know some of the older cordless drill batteries were like this and if you didn't run them all the way down, they would not hold a charge very long. Maybe they are different. Thank you again.

Doug

12/24/36 means that since it's a three bank charger it will work on all three, 12 volt, 24 volt or 36 volt system. In your case it just means it will charge both TM batteries and the cranking battery.

Don't get confused thinking a ProMariner built charger is a 5 amp per bank charger when they say 5/5/5 per bank with a total of 15 amps. Unlike other chargers, it transfers it's output to the battery/s needing it. Since the cranking battery charges up fairly quickly, when it's fully charged, it transfers that output to the TM batteries and charges them a 7.5 amps each, instead of just the 5 amps. That is there On Demand Charging system.

My personal pick for a small charger would be this the Cabela's ProSport 20 plus http://www.cabelas.com/cabelas/en/templates/pod/horizontal-pod.jsp?id=0019015&navCount=6&parentId=cat600056&masterpathid=&navAction=push&cmCat=MainCatcat21276-cat600056&parentType=index&indexId=cat600056&rid=. This one will give you a full 10 amps for each TM battery once the cranking battery tops off. This can make a difference if you come in one night after heavy use and plan to go back out the next morning. My first pick and the only onboard I've run for years is the ProMariner ProTourny 300 three bank, just not too sure your looking for that much of a charger. That sucker will fully charge you batteries in about four hours.

As for charging partially discharged batteries. It's recommend you not charge a battery that has greater than 80% charge on it. I no longer fish all day, I go at or just before daylight and fish until I've had enough, usally about noon time. I go in, clean the fish we kept that morning, eat, take about an hours nap, and do things around the house until about 4:30 when I go back out and fish till dark or later. If my batteries are not down to 80%, I leave them alone and don't plug up the charge until I come in the next day at noon. I pretty much have to run my TM on high the whole time to have my batteries below 80% in just one trip, and that's usually when chasing schooling fish.   I guess I should also mention I run a Curtis Digital Batttery Charge Indicator that shows me the charge level of my batteries in 10% increments so it's pretty simple for me, that's also about a $200 toy.  In reality the monitor lights on the charger or a remote monitor will show you charge level in 25% increments and is all you need.

As the memory thing. Lead acid batteries will not develope a memory, NiCads are about the only ones you have to worry about for that and don't know of a NiCad Tm battery.

It's just recommended you not charge a lead acid battery with greater than 80 charger and never run one down below 20% charge to get max life out of the plates.

How do I measure the % of the battery? Thank you for the info.! That's just what I needed to know. I'm going to order the battery charger from Cabelas when I get off work tonight. Finally, with you help, starting to understand.

Well, you just complicated things a little.  I noticed the Cabela's and BPS chargers don't have the charge indicators.  My PM PT 300's have the same indicators built in, their remote charge indicator has that show's full charger, 50% and 20% and was thinking those had that also, which would at least give you some indication.   There are a number of companies that make charge indicators, some that can be wired in and used to check the batteries by flipping a switch.  The ProMariner remote gives you and idication but that's about all.  Any of them will work because they connect to the batteries, not the charger so you don't have to worry about them working with which ever charger you pick.

A digital volt meter will work also.  All you have to do is take a voltage reading on the battery.  Most new, fully charged deep cycle batteries will have approx 12.8 VDC when fully charged and let sit for 24 hours after charging.  Each 0.1 volt drop from that is approx 10 percent so if your battery had 12.8 VDC and was at 12.3 VDC after use, it would be at approx 50%.   These are just rough numbers but are more than close enough to serve your purpose.  If it's showing more than 12.84 VDC, it still has some some residual overcharge left from the charger.  Just to clear that up, all chargers over charge a battery.  It's necessary to over charge one a few percent to get it to full charge.  Just them cheap chargers over charge one too much if left connected too long.

If I remember, I think BPS used to have a cheap MinnKota unit to give you a % of charge.

I do have a digital volt meter (don't know why, cause I never knew how to use it). So I think I will got with that, I'll be able to figure it out then. Thanks again for all the help!

Doug

Let me clarify something about the charging at 80%.  If you're not going to be using the boat for 24 or more hours, go ahead and plug the charger up regardless of the percent of discharge.  You don't want to let it sit more than 24 hours with the batteries at any level of discharge.  

Also, leave the charger plugged in 24/7 when not using the boat.   Just be sure to check the water once a month (and only ad distilled water) and keep them clean and dry (wash them with a little baking soda from time to time).  It's also a good idea to disconnect everything from the batteries except the charger when you're putting the boat away for an extended time, like for the winter.