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Thrall
02-12-2011, 12:45 PM
I'm putting an onboard charger in my X2. Have 2 batteries, one start battery, one house battery for the amps. They are completely isolated from each other except for a Blue Seas ACR to link them for charging off the alternator.
I picked up a Pro Sport 6 single bank charger (meant for one battery). I don't need the extra charging ability of a 2 bank charger and with the ACR linking the batteries, it should charge both batteries equally.
Presumably the house battery gets more run down over the course of a day than the start battery.
My question is, will the single bank charger overcharge the start battery while bringing the house battery up to full charge?
With the ACR linking the batteries whenever it sees charging voltage, even if I got a 2 bank charger, wouldn't a 2 bank charger possibly do the same thing unless I installed a disconnect on the wire linking the batteries through the ACR?
Note, I've been re-charging/maintaining the batteries now for a year with just a little plug in maintainer/charger typically used on motorcycle/atv batteries by just hooking it to one battery (the house battery since it's more accessible) and letting the ACR link the 2 batteries. It appears to fully charge both batts as it goes into maint mode a day or 2 after pluggin it in. Also, both batteries are good AGM batteries although they're not identical. One Odyssey, one Optima, but they're similar aH capacity and will accept the same charging profile.
Do I need to put a hard disconnect in between the 2 batteries and use a 2 bank charger to maintain max battery life, or will my setup work fine (single bank charger, batteries link up for charging)?
Anyone who's installed an onboard charger, I'd welcome your experience.

robin
02-13-2011, 01:21 AM
thrall, i like you have the blue seas acr. i have installed the promariner promite 5 amp. it is wired to the house battery, and after the charging starts, the acr links the batteries for both to charge. i have observed no issues with over charge on the starter battery. it takes awhile with only a 5 amp charger, but so far so good. hopefully that damn ground hog was right...ready for spring!!

Thrall
02-14-2011, 12:41 AM
Thanks Robin. That's what I was hoping to hear. I can't see where it would terribly overcharge 1 battery unless maybe one was completely dead.

robin
02-14-2011, 10:14 PM
my understanding of electricity, including 12v dc, is best summed up with saying electricity always flows the path least resistant. if you've got 2 batteries together with the acr, electricity is going to go to the "empty" battery 1st....especially if it is the house battery on which the charger is hooked to. hope i make a little sense at least.

Thrall
02-14-2011, 10:48 PM
Yes that makes sense and was the premise I was working under for only needing a single bank charger. I read all the crap in the instructions about different charging profiles for different types of batteries and such and it got me thinking though.
I installed the charger, but actually put it back in the engine compartment and wired it to the starter motor/engine block. The batteries were pretty well topped off since I've had them on the little maintainer off and on. Plugged it in, it went to charge mode for a little while and then they were topped off and it dropped into maint mode, so I think all's good.

EarmarkMarine
02-15-2011, 12:57 PM
I'm an advocate of isolated dual bank charging to promote maximum battery longevity. I understand that current will flow to the battery that is most discharged with the lowest internal resistance. But when you apply current to a fully charged battery with a high resistance won't the battery's voltage still continue to rise until it gases out? So I'm not sure that being in parallel with another battery automatically resolves the question. Battery chargers at various times may deliver a much higher voltage than an alternator for example. I'd be most concerned as the two batteries are being used very differently and age very differently, particularly later in their life cycle. The charger profile will be based on the average reading of the two paralleled batteries so that almost guarantees some degree of over/undercharging.

David
Earmark Marine

BNIROOSTER
02-15-2011, 06:06 PM
If the batteries are of the same type (ie., agm or lead acid) they should charge fine. If you think about each cell in a battery there is some degree of unequal discharge or recharge, but not really enough to change the life span of the individualy battery. When you connect 2 or more batteries in a 12v system each battery acts similar to an individual cell.

Thrall
02-16-2011, 07:08 PM
I'm an advocate of isolated dual bank charging to promote maximum battery longevity. I understand that current will flow to the battery that is most discharged with the lowest internal resistance. But when you apply current to a fully charged battery with a high resistance won't the battery's voltage still continue to rise until it gases out? So I'm not sure that being in parallel with another battery automatically resolves the question. Battery chargers at various times may deliver a much higher voltage than an alternator for example. I'd be most concerned as the two batteries are being used very differently and age very differently, particularly later in their life cycle. The charger profile will be based on the average reading of the two paralleled batteries so that almost guarantees some degree of over/undercharging.

David
Earmark Marine

If the batteries are of the same type (ie., agm or lead acid) they should charge fine. If you think about each cell in a battery there is some degree of unequal discharge or recharge, but not really enough to change the life span of the individualy battery. When you connect 2 or more batteries in a 12v system each battery acts similar to an individual cell.

So there's some food for thought. David's explanation is what I was originally concerned about.
BNI, yes both batteries are the same type, HP AGM, although one is a year older and they are different brands although very close in capacity, CCA, reserve time, etc.
My goal was to make the charging as simple as possible. ACR to link the batteries for alternator charging, no switches to throw to plug in for a full recharge, etc.
Seems you can't have your cake and eat it too. Guess I'll give it a shot and see how long the batteries last. Once I actually start using the boat in the summer I can monitor if the start battery is getting too warm from overcharging.
Thanks for everyones help.

EarmarkMarine
02-16-2011, 07:33 PM
Thrall,
Typically the ACR/VSR schemes advocate using a single bank charger to charge both banks as their scheme keeps both banks conbined during AC shore charging. Its not the end of the world in the context of a fishing boat where the house bank is moderate and the load at rest is limited to a fishfinder. However...Do you really think anyone would charge the depleted trolling motor bank along with a starting battery off of a single bank charger? That's what we're talking about here. The scheme has got to graduate as the system capacity and demands get larger. One size does not fit all.
I would want an ACR/VSR that isolates the two banks during AC shore charging. I would want an ACR that combines at a threshold that is a little lower than a full volt above a fully charged resting battery. I would want a dual bank charger that has a capacity that is 10 to 13 percent of my total battery amp/hour capacity for the purpose of desulphation.
The right schemes are available.

David
Earmark Marine

Thrall
02-17-2011, 11:04 AM
David, that makes complete sense. Seeing as I really don't need to maintain/charge teh start battery during the boating season, I think the simplest correct way to keep a good charge on the house battery (in my setup where the house and start battery are ONLY linked by the ACR) would be to connect the charger directly to the house battery and install a simple disconnect on the wire that links the 2 batteries thru the ACR.

If I may, hre's another question. The charger is a Promariner 6, single bank. The instructions said not to cut/shorten the charging leads. Right now I have it mounted in a location that I would prefer to keep it at, but in htis location, the charging leads are not long enough to reach the house battery or the distribution blocks for it. Do you know if it's acceptable to lengthen the charging leads? (Not much, they are about 5' ? long now and would need to add another 3-4' of length)

EarmarkMarine
02-17-2011, 12:21 PM
Thrall,
ProSport recommends that you use their 5 or 15 foot extenders so that you don't void the warranty and compliance with certain marine standards that I cannot recite (and do not want to learn).
If your warranty has run its term then you could extend the wires from the very end with the same gauge wire. Or, you can use a thick piece of ABS and a couple of S.S. bolts and double nuts, washers, etc, to make a junction block without removing the ring connectors.
I agree with the switch scheme to isolate the starting battery from the closed ACR during shore charging. And, you can always add a very cost effective 'tender' for the starting battery for the winter to offset the 3 to 6 percent self-discharge per month.

David
Earmark Marine

Thrall
02-17-2011, 04:35 PM
That's what I'll do then I think. Disconnect switch on one of the ACR wires. Extend the charging leads. It's brand new so still under warranty so maybe I'll look into the 5' extension or just build jumper wires with ring terminals and bolt and heat shrink them together.
For the off months, assuming both batteries start out with a full charge, don't think it would hurt to let the ACR link them for maintenance purposes, do you?

BNIROOSTER
02-17-2011, 05:29 PM
Thrall,
Typically the ACR/VSR schemes advocate using a single bank charger to charge both banks as their scheme keeps both banks conbined during AC shore charging. Its not the end of the world in the context of a fishing boat where the house bank is moderate and the load at rest is limited to a fishfinder. However...Do you really think anyone would charge the depleted trolling motor bank along with a starting battery off of a single bank charger? That's what we're talking about here. The scheme has got to graduate as the system capacity and demands get larger. One size does not fit all.
I would want an ACR/VSR that isolates the two banks during AC shore charging. I would want an ACR that combines at a threshold that is a little lower than a full volt above a fully charged resting battery. I would want a dual bank charger that has a capacity that is 10 to 13 percent of my total battery amp/hour capacity for the purpose of desulphation.
The right schemes are available.

David
Earmark Marine


If you arent using an external regulator on your alternator (which most stock MC alts dont) that has dual zone charge rates, isnt the alternator charging both the house and the starting batteries when switched to "all"? Assuming that you need to charge both banks while on the water. I am using a balmar HO alt paired with a multi stage regulator that senses which bank of batteries need charged and at what voltage (only because my stereo system consumes around 200 amps at peak) IMHO two like batteries would be similar to the charging system used in most diesel pick ups. Prior to this was using a single charger to charge both (like) batteries with the batt switch in the "all" position with no noticeable premature failure....maybe I was just lucky?

EarmarkMarine
02-17-2011, 08:50 PM
One thing for sure is that when it comes to boat charging systems and two banks there are many conflicts and contradictions. You won't achieve perfection so you'll do the best you can. Protecting your alternator can often conflict with preserving your batteries. As systems increase in size you have to alter your charging scheme to suit. Few people have the benefits of a Balmar alternator and regulator. Alternators in general are intended as maintainers and not chargers and are comparatively primitive to a multistage charger. Also, keep in mind that the alternator may deliver less voltage than some charger stages and are less likely to gas out a battery(s). Its really apples and oranges.

David
Earmark Marine

hbomb
02-17-2011, 10:20 PM
my recently arrived 07 X2 has an onboard charger (Guest) which i note is a single bank but has a piggy back wire to the second battery however, my issue was being in Australia - 240 volts.... after some research I went with the Xantrex Truecharge 2, a 3 bank charger which I purchased from the east coast (abes of Maine) for less than $ 200 and included a specific temp guage for the house battery and an led display you can fit ...which notes charging etc Guest has a 230 volt version but the price here is a joke and I have left out the word describing what sort of descriptive joke the price is!
undertand what you are going through thrall but for a few bucks...Guest have a 2 bank charger and ProMariner which would save you a hell of a lot of work and time but hey, I do understand the value of the buck!