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| I have a 2002 225 Optimax and I am wondering if anyone runs two starting batteries parallel or if anyone knows if this is ok. Could it hurt the alternator or electrical system of the motor?
I don't want to run into problems running one battery down with my electronics and other accessories, but I don't want just a stand alone battery for them. I would like to run two parallel so the system is charged when running the opti. I have friends who have had problems not having enough left in the battery to turn over the opti when fishing long periods at night in one spot.
Does anyone do this?
Thanks |
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Posts: 32885
Location: Rhinelander, Wisconsin | I have, with no issues. |
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Posts: 433
Location: Cedarburg, Wisconsin | You could run a hundred batteries in parallel and the equipment hooked up to it wouldn't know the difference. All the equipment cares about is the voltage as long as the batteries can supply the amp draw required at that voltage. 12V is 12V. The only draw back is the cost of multiple batteries and the weight. If it makes you feel more secure go for it! |
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Posts: 307
| I wired up my 02 Opti 200 last year like this for just the issues you stated. I also have only one of my on board battery charger leads going to one of the batteries. I haven't encountered any problems yet. |
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Location: Green Bay, WI | You could indeed just hook up more than one 12-volt battery in parallel, and the engine wouldn't know any difference (neither would the accessories you are powering). However a potential issue is that if one discharges, then so does the other. Say your alternator doesn't charge anymore--then both batteries will simply continue to power the circuits until BOTH go dead.
The "right" way to do it, would be to install an Automatic Charging Relay (ACR), that isolates each battery, but still allows each to be charged by the alternator on the engine. Check out the information at this link:
http://bluesea.com/category/2
...and I think you'll see what I mean.
Keep in mind that an ACR is *not* absolutely necessary--it's simply an added measure of protection against both batteries going dead. When the voltage of one of the batteries goes below a certain point, then that battery is isolated from the circuit and a low-voltage light illuminates (on certain ACR models). But this might be overkill for most applications, to be honest, and I have seen guys simply put another tray and battery next to the start battery, just to have it available if needed. If the one battery supplies the minimum cranking amps required by the engine, then all is good. Of course you'd have to keep the spare battery charged yourself, but it will serve the same purpose in the event that the main unit dies...you will just have to disconnect the dead unit and hook up the fresh one.
If you are interested in learning more about the ACR thing, just let me know and I can point you towards more information on the web.
EDIT: RE-reading this post, I guess I should clarify one thing I said. If two 12-volt batteries are wired in parallel, then the volts in the entire circuit will be 12. However the current drop across each 'leg' will be additive, because the load (the engine starter) is being picked-up by both batteries. So in the case of a dual-battery configuration, the cranking capacity of each battery is essentially additive, and thus then engine "sees" much more cranking power from the power source (ie; both your batteries in parallel). For you this means the engine may turn over noticeably stronger, depending of course on the capacity of the existing battery you have there now. If it's more than sufficient for the engine's needs, then you might not notice ANY appreciable increase in start performance. But if it's borderline, your engine will like seem to "jump to life" when you turn the ignition key.
It's a small point, but one worth making: Parallel-wired start batteries can indeed make a difference, but don't expect to see a huge performance increase if the existing battery you have is of the correct size (capacity), and is properly maintained. I think that the main issue for most guys, is simply having another battery available in case the main start unit goes down. And for owners of the Mercury Verado engines, having strong, steady power is crucial--as the engine is very dependent on the proper voltage for normal operation. You can check out this issue in the library section of the Verado Owner's Club, if you want to know more.
http://www.veradoclub.com/smf/index.php?board=6.0
TB
Edited by tcbetka 4/22/2009 10:41 AM
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| Thanks for the info. I was concerned about the alternator having the additional load of charging the two battteries. I have a three bank charger but only one lead available for the two starting batteries. My owners manual for the on-board charger stated that it is not reommended (but can be done) to charge two batteries parallel as this can reduce the life of the charger since it is made to charge one. I wondered if the alternator of the motor would have the same issue.
I hooked it up and everything seems fine. I used two batteries parallel on my previous boat for the 12V trolling motor and it made a huge difference in the run time of the trolling motor. I assumed it would work just as well for my accessories and motor so I would not be sitting with a dead battery. Color electronics drain a lot of juice along with everything else at night.
Thanks |
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Location: Green Bay, WI | In the case of the ACR, the alternator does charge both batteries...but not simultaneously, as I understand it. I haven't installed mine yet, but I believe I read in a book on boat electrical systems, that the ACR units switch to first charge the battery with the lowest voltage--and then charge the other battery. But I am not 100% sure of this. The point is that they do not charge both batteries at once.
That being said, my RV has a Caterpillar engine and I just installed two new starting batteries. We bought it used, and it only had one chassis battery--but the tray holds two. When we picked it up in Florida a month ago, a mechanic I hired told me to simply buy two new start batteries (you never want to put a new battery next to an old one, by the way), and then just wire them in parallel. In other words, the alternator just charges both units. So that's what I did when I got it back home, and man what a difference it makes in turning that Diesel engine over! It's pretty remarkable.
So if I were you, I would probably just buy another battery and set it in a tray next to your current start battery--and only use it when/if needed. This would be the easiest way to go, and then you could simply charge it with your 3-bank charger, alternating a cycle with the main start battery. In this case, the ages of the batteries would not matter, as you're not going to be using them simultaneously anyway. Your other option(s) would be to replace both batteries and either install an ACR to isolate them each, or simply take your chances and wire them directly in parallel. It shouldn't hurt the alternator, as far as I know. Look at your battery charger when you first start charging the start battery--I don't think you'll see that many amps being drawn, although don't forget that the charger is 110v so the current may not be the same as that from your 12v DC output engine alternator (depending upon your particular battery charger). Still, your alternator should have plenty of output to charge both batteries. Don't forget...neither start battery will be discharged nearly as much, as they are in parallel and share the load from the starter. Thus you really shouldn't need all that much more current from the alternator.
Another thing you could do is to do a search on the forums at:
http://www.thehulltruth.com/
Copy & paste "parallel battery starting" into the search engine. I found several threads there that look helpful for you.
Good luck!
TB
Edited by tcbetka 4/22/2009 3:16 PM
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| I don't think anybody has already said this: I have always used two batteries, but I have the boat wired so that things that draw a lot of power, like the trolling motor or pumps go to one battery, and the other is wired to the starter and electronics, which don't use much. That way if I ever run the one down with the trolling motor or run the bilge pump a lot on a rainy day my starting battery will always be good. The only draw back to this is that the second battery doesn't get recharged by the engine while running down a lake. But I've always been OK with just putting a charger on the second battery at the dock |
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Location: Green Bay, WI | Hence my recommendation for the OP to simply install another battery in a tray next to the first, and only use it to start if needed. Of course he could always power various circuits from it, but then it might not be as strong if it is ever needed to start the engine. But there's nothing wrong with the plan you outlined, as long as a guy remembers to charge the thing, lol.
But the "right way" to do it would be to install two batteries and an ACR device. Then the batteries can each power their respective circuits and the alternator will charge them both in turn (depending upon their voltage level), and each will be protected from excess draw down of the other battery.
It's certainly more expensive to install two batteries and wire up an ACR system, but it isn't difficult. Perhaps the difficult part of the installation is finding enough open space to install the hardware...
TB
Edited by tcbetka 4/24/2009 6:54 AM
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| Tom is right on with his advice here. If you want to examine a few diagrams, check out this similar posting.
http://forums.iboats.com/showthread.php?t=248130 |
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Posts: 3240
Location: Racine, Wi | Along the same lines, what sized battery are you guys that are only using one starting battery, using? I picked up a new one late last fall, but it was the only one they had left, and not as big as I wanted to go. I just don't want to run my battery down running the GPS and 2 locators, and lights if at night.
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Location: Green Bay, WI | I believe my Verado is wired to a group 31 (it might even be group 34), with about 1000 cranking amps. I haven't looked in a while, to be honest, but I seem to recall that it was a group 31. Mercury tends to really push for high capacity batteries on the Verado engines, simply because so much depends upon flowing electrons--DTS, SmartCraft gauges, power steering, the ECU. I don't know anything about Opti engines, but if you have the DTS and SmartCraft gauges, I bet you'll need just as big a battery as the Verado does.
If you're worried, make sure that you at least have a long pair of jumper cables on board, so that you can run from a trolling motor battery to the start battery. I have had to jump a start battery in an old boat more than once.
TB
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Posts: 3240
Location: Racine, Wi | I run a Yami 4 banger, so not sure how much those use, but I don't have the smartcraft guages etc on it. Just the locators, gps, and lights at night. I'd rather have a bigger battery than a smaller. I'll have to take a look at what I'm running. I seem to think it's an 800 amp (or whatever that is) battery. Thanks for the info Tom! |
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