Batteries for Dual Battery systems?

[flintsghost]

I'm in the process of installing a dual battery system or having it installed as the case may be. I've done part of the work already. Some still to do. I have been told several different things about battery choices and want to know if anyone, anywhere has some knowledge and experience that can enlighten me. The things I've been told seem to be counter to each other in some cases.

First: I need to use "exactly" the same battery in both positions in the system.

Second: The batteries don't need to be the same battery.

Third: Batteries need to be of the same type and have the same charge rate so the alternator can keep them up to speed, but don't need to be the same exact size or make.

I'm going to use a Optima 34 series in the second or auxillary position. But their optima battery for the standard position on my FJ Cruiser is a larger and heavier Group 27. Since both would be yellow tops, they would be of the same type. I can't seem to find out from anywhere whether they have the same charge rate. The group 27 has a heck of a lot larger capacity and is the battery Optima recommends for my application as a primary.

Hopefully someone will have an answer.

[goodtimes]

What are you separating them with?

My 2 starting batteries (diesel) are identical - old school flooded, non-maintenance free, off brand batteries. My house battery is a Odyssey AGM.

There is a National Luna charge controller separating them - and I haven't had any problems with them being different sizes & types.

[tradman]

I've got an Odyssey PC1700 and an Optima yellow top in my dual batt. setup. Separated with an IBS charge controller. No issues whatsoever with the batteries being different.

[LR Max]

Meh on all of that. I've got a Yellow top and a Red top optima in my rig. Sitting right next to each other under the hood, wired directly in parallel. They are the same size battery but that is it. Otherwise, not a single problem.

Oh and its been like that for 10 years so yes, it works.

Only thing I've heard is to avoid the blue top optimas. Apparently the cause spontaneous vehicle combustion. Obviously this is anti-productive.

[flintsghost]

Thanks for the replies. Odyssey and Optima are basically the same technology and "might" have similar charge rates. I personally think two Optima batteries of different sizes shouldn't be a problem. But it's interesting to see what people are using. The Blue top Optima by the way are actually intended for Marine application as in water not military. I don't think they are a good choice for a vehicle that has such high charge rates off a constant charge alternator system which boats don't have, but what do I know. That could be why they have had problems in the past.

[cnynrat]

I have an Optima Yellow top in my FJC as a second battery, and the standard sealed lead acid battery that Toyota installs as the primary battery. I have the dual battery kit from Dirty Parts, and everything works fine.

When people hard wire two 12v batteries in parallel in an attempt to increase the AH capacity it's standard advice that both batteries be the same brand/model, and in fact it's best if they have the same date code. Even then, I've found that configuration doesn't give me the performance I expect.

[flintsghost]

I have an Optima Yellow top in my FJC as a second battery, and the standard sealed lead acid battery that Toyota installs as the primary battery. I have the dual battery kit from Dirty Parts, and everything works fine.

When people hard wire two 12v batteries in parallel in an attempt to increase the AH capacity it's standard advice that both batteries be the same brand/model, and in fact it's best if they have the same date code. Even then, I've found that configuration doesn't give me the performance I expect.

Interesting. Dirty Parts are the people who told me that they didn't have to be the same.

[LR Max]

For the Odyssey batteries, do some research. They make the Sears high end batteries. Same thing as the Odyssey, just got a different color and has a different sticker on it.

Could save you some $$$ to get the same thing.

[flintsghost]

For the Odyssey batteries, do some research. They make the Sears high end batteries. Same thing as the Odyssey, just got a different color and has a different sticker on it.

Could save you some $$$ to get the same thing.

I already knew that but there are two reasons I won't do that. First I have been a Sears victim many times on many different items and they will never get another penny of my money. Second, my spare battery tray is made for an Optima battery and I already have it. I have nothing against Odyssey batterys other than that.

[cnynrat]

Interesting. Dirty Parts are the people who told me that they didn't have to be the same.

And just to be clear, they do not need to be the same in this application.

What some people in the RV world do (and I guess some off-road trailers as well), is take two batteries and wire them in parallel to try to double the available capacity (amp-hours). Note that there is typically no switch in this configuration. The discharge behavior isn't always what you expect from that configuration, particularly if the resistance of the two batteries differs from one another. Hence the recommendation in this type of setup to use same brand/model/date code - it's an attempt to try to ensure the two batteries have the same resistance.

In a switched dual battery set up in a vehicle it doesn't seem to be a problem. I think that's because by and large the only time your batteries are connected in parallel is when they are charging (because the vehicle is running and the solenoid is closed). You might get some charging anomalies, for example one battery may not charge as quickly or fully as the other, but as I said I haven't seen a problem with two very disimilar batteries. I've had my dual battery kit installed for about 4 years now.

[Buliwyf]

Batteries don't have to be the same.

But you may want to use a good battery isolator.

[jrule]

I do not recommend Optima batteries I have had nothing but problems with there new batteries . The old optima was a good battery not sure what they did to them one discharge and there junk.
I started running DEKA Intimidator Batteries they are great. http://www.dekabatteries.com/default.aspx?pageid=163
85011
Running a Painless Wiring 40102 250-Amp Dual Battery Current Control System

[Nonimouse]

Always use Numax - mainly CVX27 or 31

They do what it says on the tin for the right money

[Antichrist]

I do not recommend Optima batteries I have had nothing but problems with there new batteries . The old optima was a good battery not sure what they did to them one discharge and there junk.It seems to have coincided with their sell out to Johnson Controls and production being moved to Mexico.

If you want something the same size as an Optima, check out Exide's AGM batteries. I used them before switching to the Diehard Platinum and, at the time, all their specs, including warranty, was better than Optima. I got good life out of them and the last time I checked, the AGM's were made in the US, if that matters to you.

[clandr1]

I'm running a blue top optima in my truck as the secondary battery, hooked up with a blue sea automatic charging relay.

I'd like to know more about this "spontaneous combustion" issue. I've been running mine for close to a year without a hiccup.

[flintsghost]

I'm running a blue top optima in my truck as the secondary battery, hooked up with a blue sea automatic charging relay.

I'd like to know more about this "spontaneous combustion" issue. I've been running mine for close to a year without a hiccup.

Keep in mind that LR max said that he had "heard" that. There may be someone who can shed more light on it. The Optima website does indicate that they are "Marine" use batterys and doesn't recommend them for the application as a auxillary battery. They recommend "yellow tops" for auxillary and HD use and "red" is for standard auto starting and continuous charge use. If you don't have to use your auxillary very much there shouldn't be much problem but what do I know. That's why I asked about batterys to start with.

[Karma]

HI All,
In myJeep Wrangler I installed dual batteries with an isolation system about 6 years ago. I started with Optima Yellow Tops because of their reputation. I had nothing but trouble with the Yellow's. After about 4 years (I'm a slow learner) I switched to Odyssey's and have had no trouble. How it goes in the long run, only time will tell.

I do think that the two batteries should match. Any battery engineer will tell you this. This is not trivial; there are good reasons. If you switch one, you should switch the other. After all, we install dual batteries to improve the reliability of our vehicles. Why defeat this by taking shortcuts?

Sparky

[HillbillyfromAL]

FWIW you can connect your winch safely to the post of Odyssey batteries, not an optima.

[flintsghost]

FWIW you can connect your winch safely to the post of Odyssey batteries, not an optima.

I guess I don't understand what you are saying. Because it sounds like you are saying I can't run a winch off an optima battery. Since both batteries are built on essentially the same design and run the same things one should be able to run a winch off either. If you don't think you can I would be interested in knowing what your rationale is for that statement.

[MoGas]

I think he is referring to the side posts. Optima specifically mentions that you should not hook a winch to the side posts. Why? I'm not really sure.

[MoGas]

BTW, My setup is Red Top for starting, factory vehicle systems, and winch, with a Yellow Top for fridge, inverter, and lights separated by a National Luna system.

[flintsghost]

BTW, My setup is Red Top for starting, factory vehicle systems, and winch, with a Yellow Top for fridge, inverter, and lights separated by a National Luna system.

That's interesting because the system I am installing right now will be a D34 yellow optima as a auxillary battery for emergency use and a Red Top for the main. Tentatively planning on using an
IBS system to control them. I was wondering about what was said and now that you mention it the side posts might make sense but since all optima's don't have them and I've never seen anyone hook a winch up to them, why did he bring that up. The original idea when I asked the question was to get answers about similar or different batteries being hooked together. While I received some pretty good information, I also got a lot of suggestions about which battery to use. That was never in question since my auxillary tray is one of Roger Moody's and it is made for a specific group 34 Optima battery. I also specified to the dealer who got it from the warehouse that I didn't want a D34/78 with side terminals. Just a D34 straight. The Red Top I pick up tomorrow is a group 35 with reverse terminals for the Toyota housing. Thanks for the info. I appreciate it.

[HillbillyfromAL]

I think he is referring to the side posts. Optima specifically mentions that you should not hook a winch to the side posts. Why? I'm not really sure.

Well after emailing them to find out why they replied back saying that the internal connections weren't built to handle the amp load for any period of time other than starting they also claimed that this was true for all batteries but that is not the case. A quick email to Odyssey and they said there were built to handle the same load on the side terminals as the top terminals.
Some dual battery setups have a battery laying side ways connecting to the other battery side terminals. So if that were going to be the case an optima may not be the best choice to use.

[HillbillyfromAL]

I guess I don't understand what you are saying. Because it sounds like you are saying I can't run a winch off an optima battery. Since both batteries are built on essentially the same design and run the same things one should be able to run a winch off either. If you don't think you can I would be interested in knowing what your rationale is for that statement.

Yes I meant to say side post.

[zimm]

if youre not hooking the cells in parallel for extended periods i wouldnt worry. in series, with high voltage and large draws like the UPS systems i install? yes. internal resistance is the reason. but even then, when a customer wants to delay a re battery, i'll swap in a few new ones with the old, and instead of buying 40, they buy 5 and put off the investment another 18 months.

i run sears platinums. cant beat em. they honor the warranty too. i killed one three years in, and it was my bad. they tested it, and handed me a new one. no receipt.

[zimm]

spiral cell design is a round peg in a square hole.