Battery charger for marine grade dual battery setup

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If you apply the charger to the same point where the alternator attaches (in our case, the anode or input of the device), the charger will charge all batteries just like your alternator would. On my LC, I apply the charger to the anode aux. battery and the charger charges both my aux. battery and main battery through the isolator. If you're using a IBS or some other mechanical relay that's voltage sensing, it should work the same way....sensing elevated charging voltage from the charger and causing the relay to close.

So in Spresso's case, if he applied the charger to the anode post, it would charge both his batteries and when both batteries reach a point of saturation, the charger should turn off or drop down to float charging, however his charger is set up.

Scott

mechanixhorseman said:
I'd be interested to hear mobi-arc chime in on this as this is his area of expertise as well.
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mobi-arc said:
If you apply the charger to the same point where the alternator attaches (in our case, the anode or input of the device), the charger will charge all batteries just like your alternator would. On my LC, I apply the charger to the anode aux. battery and the charger charges both my aux. battery and main battery through the isolator. If you're using a IBS or some other mechanical relay that's voltage sensing, it should work the same way....sensing elevated charging voltage from the charger and causing the relay to close.

So in Spresso's case, if he applied the charger to the anode post, it would charge both his batteries and when both batteries reach a point of saturation, the charger should turn off or drop down to float charging, however his charger is set up.

Scott
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Thanks for the input. Mike suggested that there would be an issue in the case where both batteries are of differing sizes (in my case a 31M prim and 34M aux). Is this true and if so, why?
 
Why not just lift the ground of the IBS relay? Doing so will not allow it to close at which point you can charge battery A, then when that's done, switch it to battery B.

Which respect to two differing sizes of batteries, I think the issue is more a function of differing grounds. If you ground the two batteries to each other (battery A ground tied to battery B ground), then when the charger ground is applied, all batteries and the charger are all grounded at the same level. I think where charging multiple batteries becomes an issue is when different ground cause batteries to get charged differently due to inconsistent grounds. I was up in Orange County a few weeks ago helping an Odyssey battery rep sort out a problem with a police fleet. They have a main battery in the engine compartment, and a second battery in the trunk which powers the computer and comms. So they keep having to replace the rear trunk battery after about a month and they can't figure out why the rear battery keeps being problematic. Well they have the main starting battery in the engine compartment grounded in its OEM harness and they have the trunk battery ground next to its mounting location in trunk. Not surprising, the alternator's ground reference for the main battery is far better than the ground reference for the rear battery so rear battery isn't getting much current due to resistance on the ground leg. When they run a dedicated ground line from the main battery ground to the rear battery ground, problem solved.

Spresso had a similar issue on his truck. Just because the ground "looks" perfect doesn't necessarily mean it's a good ground.

Scott


mechanixhorseman said:
Well so far I've got somewhat conflicting information from IBS and the aforementioned odyssey distributor. IBS claims that there is no issue with charging both batteries while linked together because the "smart charge" sees them as one big battery. On the other hand the odyssey rep states that because the batteries are of differing sizes this can and will lead to negative complications. In order to err on the side of caution I would be manually isolating them (one way or another) on probably a monthly basis and charging them individually.

The Optimate 6 has been doing a pretty phenomenal job with charging and I've got it out on the garage now desulfating and reviving my old red top group 35. It is recommended for the full range and types of batteries and since it was recommended by someone whose occupational duties include reconditioning my exact battery, I think it's probably safe to rely on. Initially I found a lot of documentation indicating that the 31M needed a high amp charger, but throughout my research, I really haven't been able to find any rationale for that. I'm still waiting for some answers to a couple more questions I had for IBS, but so far that's where I'm at.

Any ideas for manually isolating that's cheaper than a marine grade 200amp breaker? I don't really feel like busting out the sockets and resetting my clocks every time I want to charge my batteries.

Edit to answer your last about disconnecting the controller: I actually hadn't thought of that and that may very well do the trick. My only concern with that, although minor, is the wear and tear on the connector from regularly disconnecting and reconnecting it. It's a pretty beefy connector and I'm not sure if the T-max is the same, but try to limit the amount of times I have to stress plastic parts if I can.

The only thing I can't seem to get my head around is the thought that this charging issue either 1) is not that big of a deal or 2) nobody acknowledges it and just expects to only get 2-3 years out of their AGM batteries. It seems like IBS/T-Max, etc, would have put a manual isolate button on the controller if it was and maybe I'm just getting wound around the axle for no reason.
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mobi-arc said:
Why not just lift the ground of the IBS relay? Doing so will not allow it to close at which point you can charge battery A, then when that's done, switch it to battery B.

Which respect to two differing sizes of batteries, I think the issue is more a function of differing grounds. If you ground the two batteries to each other (battery A ground tied to battery B ground), then when the charger ground is applied, all batteries and the charger are all grounded at the same level. I think where charging multiple batteries becomes an issue is when different ground cause batteries to get charged differently due to inconsistent grounds. I was up in Orange County a few weeks ago helping an Odyssey battery rep sort out a problem with a police fleet. They have a main battery in the engine compartment, and a second battery in the trunk which powers the computer and comms. So they keep having to replace the rear trunk battery after about a month and they can't figure out why the rear battery keeps being problematic. Well they have the main starting battery in the engine compartment grounded in its OEM harness and they have the trunk battery ground next to its mounting location in trunk. Not surprising, the alternator's ground reference for the main battery is far better than the ground reference for the rear battery so rear battery isn't getting much current due to resistance on the ground leg. When they run a dedicated ground line from the main battery ground to the rear battery ground, problem solved.

Spresso had a similar issue on his truck. Just because the ground "looks" perfect doesn't necessarily mean it's a good ground.

Scott
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Great info Scott. So then off that I've got two questions:

1) If I simply insert a two-position switch on the IBS controller or relay ground wire, will that successfully kill power to the controller and therefore isolate the two batteries, or do I need to use a relay in place of a switch?

2) Currently my Aux batt is grounded to its nearest location on the chassis. If I wanted to run a line back over to the prim battery, would 4 AWG welding cable be sufficient for the ground? I've got plenty of that and I'm all out of 1/0. I'd just assume use what I have if it is sufficient but if necessary I'd purchase more.

It seems like my first question might be irrelevant if I can successfully ground them together. If I understand correctly, you are saying there is no issue charging them together linked through the isolator so long as they share the same ground because the charger detects the batteries current charge level through its ground, right?.
 
Every ground on the vehicle is common with the negative battery ground post. The amount of resistance from your rear ground attachment point and the actual ground post on the battery is the concern. You are relying on many mechanical grounds to be "good enough" while the best ground is going to be a direct bonding between the actual battery negative post, and whatever component you're trying to ground using an appropriately sized cable to carry the current. So yes, if you have #4 cable, then go for it....it's cheap insurance. and can make a huge difference in the efficiency of the electrical system.

With respect to the IBS relay, put a toggle switch on either the ground or positive 16ga wire connecting to the small terminals presumably used to power the coil. If the coil doesn't get power or ground, it can't close thereby isolating the batteries from each other if you want to individually charge each battery.

Scott


mechanixhorseman said:
Great info Scott. So then off that I've got two questions:

1) If I simply insert a two-position switch on the IBS controller or relay ground wire, will that successfully kill power to the controller and therefore isolate the two batteries, or do I need to use a relay in place of a switch?

2) Currently my Aux batt is grounded to its nearest location on the chassis. If I wanted to run a line back over to the prim battery, would 4 AWG welding cable be sufficient for the ground? I've got plenty of that and I'm all out of 1/0. I'd just assume use what I have if it is sufficient but if necessary I'd purchase more.

It seems like my first question might be irrelevant if I can successfully ground them together. If I understand correctly, you are saying there is no issue charging them together linked through the isolator so long as they share the same ground because the charger detects the batteries current charge level through its ground, right?.
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Great info guys. I just picked up a Promariner dual bank 20 amp charger today. The charging algorithm it has for high performance agm batteries matched what both Optima and Odyssey recommend. I'll be unplugging the controller while charging until I can add a switch to the solenoid to manually ensure the batteries don't link. I think that is key, especially if the batteries are in different states of charge. One will still require bulk mode while the other needs a voltage drop. Thanks again. I'll report back on how she does...

Edit- perhaps with a dual bank charger I don't need to overide the solenoid...? I'm a total electrical noob..,
 
quick update- I disconnected the isolator controller and put the batteries on the charger. Measured at the battery terminals on the red top shows 15.2-15.4 volts. Isn't that too high? I remember reading somewhere not to charge over 15 volts. The platinum is showing between 14.2-14.4 volts while charging. Funny, because the charger specifically states that it will charge agm batteries at 14.7 absorption and 13.6 float. Is the red top going to blow?!
 
1407driver said:
Great info guys. I just picked up a Promariner dual bank 20 amp charger today. The charging algorithm it has for high performance agm batteries matched what both Optima and Odyssey recommend. I'll be unplugging the controller while charging until I can add a switch to the solenoid to manually ensure the batteries don't link. I think that is key, especially if the batteries are in different states of charge. One will still require bulk mode while the other needs a voltage drop. Thanks again. I'll report back on how she does...

Edit- perhaps with a dual bank charger I don't need to overide the solenoid...? I'm a total electrical noob..,
Click to expand...

Before you go snipping wires and throwing switches in check this out...

After a pretty good while of going back and forth with one of the IBS engineers, he finally recalled that if you hold the "link" button for 5 seconds the batteries will be manually isolated until you hold the "manual" button for another 5 seconds. I don't recall this being in the IBS manual so this is an unadvertised feature I guess. He states that it isn't well documented and that he barely even remembered programming this functionality into the controller because no one ever uses it. I for one though, will definitely find some use out of this. I went ahead and ran a wire back between both batteries' negative posts, while leaving both of their chassis grounds in place. Even with this and Scott's suggestions, I'll still probably be charging them separately once a month or so.

The other way this feature makes itself useful to me is that as I understand it, once my Aux battery drops below a certain level, the IBS may automatically link my primary battery to it to keep it from dying. Somebody correct me if I'm wrong but this seems like a terrible idea and robs me of my peace of mind in knowing that I'll always have one good charged battery. Once I have set up camp, I can now manually isolate the batteries to make sure the system will never draw from my starter battery under any circumstances. Running my aux battery all the way down may not be healthy for that battery and I would pay for that mistake later at sears, but at least I won't be stranded and will be able to eventually get myself to sears.
 
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