Confusion about 2 bank charger for 3 batteries

marks737

Active Member
Sep 15, 2009
333
NJ
Boat Info
2005 390 Sundancer
Engines
Cummins QSB 5.9
After reading a lot of battery/charger threads, I'm hearing different opinions. I have 3 batteries. 2 paralleled and one alone. A few years ago my mechanic installed a new pro tournament 360 2 bank charger. Since then I've had battery cooking issues. Some say the 2 bank charger is appropriate, some say 3 batteries require a 3 bank charger. I need to rectify this soon. By the way, the ProMariner tech support guy said I need a new 3 bank charger.

My other question is regarding how the charger is wired to the 2 paralleled batteries. Right now the wires are connected to the Pos & Neg terminals of one of the batteries. I'm wondering if the charging wires should be connected instead to the Positive side of one battery and the Negative side of the other battery. Would this change how the pair are charged and maybe solve my problem?

Thanks for the input!
 
2 batteries wired together = one large battery. So, a 2 bank is appropriate. There are some 3 bank charges that allow for stacking, as in 2 banks charging into 2 batteries that are connected. "cooking" as in over charging, does not sound like in issue with 2 or 3 bank charger, but rather a bad battery or a charger that cannot or is not evaluating the status of the bank properly. In most cases like this, we see short charger life due to a large AH bank and a charger will too little output. This cans also lead to short battery life as too little output may not provide enough initial bulk charge to a deeply depleted bank.
 
This comes down the Charger itself. Many chargers work fine with multiple batteries on each bank....hence the name.... battery bank. Those chargers also have the requirement that the batteries on the same bank be of the same type. Modern charges can mix different types AGM or flooded but not on the same bank because they require a different charging algorithm.

From personal experience, my boat came with a 3 Bank charger and one bank had two batteries on it. Back then.....batteries wouldn't last more than two years because the charger technology just dumbly applied charging voltage to the batteries whether they needed it or not. I switched to a Xantrex 3 bank 30 amp charger 14 years ago and battery life (flooded) went to 6 years (same type of Costco battery). I recently changed to Optimas (and changed the Charger settings) and have 3 Banks with 2 batteries on two banks and one on the other. No issues and the technology works.

In regards to your wiring. The charger needs a single access to a ground and multiple (one for each bank) positive wires. Promariner makes great products. Something is set up wrong if you are cooking batteries.
 
Checked the manual for the ProTournament 300 charger and it explicitly says "Each positive and negative bank wire will only be connected to one individual battery". So my setup of the parallel bank of 2 batteries being fed by one charger bank is wrong according to the manual.

I'm thinking I need a 3 bank charger for my three batteries even though 2 are paralleled together?
 
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Checked the manual for the ProTournament 300 charger and it explicitly says "Each positive and negative bank wire will only be connected to one individual battery". So my setup of the parallel bank of 2 batteries being fed by one charger bank is wrong according to the manual.

I'm thinking I need a 3 bank charger for my three batteries even though 2 are paralleled together?

No. You have two banks. As earlier poster said, the two in parallel are one bank. The charger only sees one load. You do NOT want to connect two separate charger leads to a single bank. I have the similar battery setup as you, and a Pronautic 1240 3 bank charger. I am only using 2 of the charger outputs for my two banks. If I had a genset with a separate battery, I would use the third charger bank.

As for the earlier question about connecting the charger to a parallel set of batteries, it does not matter if you connect the negative to the negative on either battery since they are effectively one post since they are linked by the wire post to post. Same on the positive side.

If you had two 6v batteries in series to make 12v (one of my 2 banks is that configuration, which effectively creates a single 12v battery), then it does matter and the two 6v batteries get wired with a wire from positive of one to negative of the other - that is, in series. Then the charger gets connected to the "open" positive and negative posts (not to the posts that are bridged for the two batteries)
 
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Checked the manual for the ProTournament 300 charger and it explicitly says "Each positive and negative bank wire will only be connected to one individual battery". So my setup of the parallel bank of 2 batteries being fed by one charger bank is wrong according to the manual.

I'm thinking I need a 3 bank charger for my three batteries even though 2 are paralleled together?
Nope, you have a large battery made up of 12 cells rather than a small battery with 6 cells.
 
Thanks for the help guys. Looks like I'm set up correctly then. Still a little uneasy about the manual's repeated warnings about bank wires going to "individual" batteries only. When I checked batteries yesterday, one of the paralleled batteries was wet on the side casing and there was fluid in the tray so not sure if they're over-charging. These are brand new batteries as of a few weeks ago.
 
Have you checked the operation of the charger with a volt meter?

I feel what the manual is telling you, is two things. Both cables of a bank must be connected in order for the charger to work. and second, the cables need to be connected to the battery, not remotely.

With two batteries wired parallel with sufficient gauge cables, I dont see that it matters much whether you connect to one battery's + and - or the others, or one's + and the others -. Now, if battery temp monitoring is part of the charger's scheme, then how that house bank was wired might matter.
 
Assuming that they are flooded batteries, I would keep a close eye on the water level in each battery for the next couple of months. The monitoring of the fluid level is the only way to determine if your suspicions are warranted.

Additionally, I took a look at the installation guide for your charger. Their wiring diagrams are misleading. I'm not sure what they were thinking but showing individual ground wires running back to the charger when the charger does not have a provision for that is misleading. That aside....what I think you are referring to is their comments concerning unused banks. The way their charger works is to push current to banks that are depleted. If you have a 3 bank charger and only 2 banks (in the real world this doesn't happen) they want you to terminate the third bank feed onto to one of the 2 banks. That way the charger doesn't see a bank with nothing on it. It is confusing because they do not use the term bank instead they use the word battery which is incorrect.

Their charger is powerful enough to have two batteries on every bank.
 
Assuming that they are flooded batteries, I would keep a close eye on the water level in each battery for the next couple of months. The monitoring of the fluid level is the only way to determine if your suspicions are warranted.

Additionally, I took a look at the installation guide for your charger. Their wiring diagrams are misleading. I'm not sure what they were thinking but showing individual ground wires running back to the charger when the charger does not have a provision for that is misleading. That aside....what I think you are referring to is their comments concerning unused banks. The way their charger works is to push current to banks that are depleted. If you have a 3 bank charger and only 2 banks (in the real world this doesn't happen) they want you to terminate the third bank feed onto to one of the 2 banks. That way the charger doesn't see a bank with nothing on it. It is confusing because they do not use the term bank instead they use the word battery which is incorrect.

Their charger is powerful enough to have two batteries on every bank.

I didn't realize my boat was not in the real world. That's really cool.

On another note for those that have the Pronautic chargers you do not connect the empty charger positve to anything. Here is what the manual says:

4. Empty Charger Banks - In the event of an empty charger bank there is no need to use a jumper as done with traditional chargers. Simply leave the DC positive unloaded and the unit will perform correctly.
 
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