New Battery/Adding battery questions

We have had our boat for 5 years and the battery is getting pretty week. Last summer we upgraded the stereo and added 2 amps. We have tended to spend more time anchored then driving with rising boat traffic and gas prices. If you don't keep an eye on the battery it will get to low to start. I want to get a new battery but I don't want to spend a ton, what would you recommend? Also I was thinking, since the current battery still holds a charge fine it just drains quickly and I need to buy a new battery anyway, of going with a 2 battery set up. What all parts and material are needed for this. I installed the whole stereo on the boat so I am confident I can do this myself I just really don't want to spend a ton of money on batteries when there is so much cooler stuff to buy.

Thanks,

Erling

I would look at Deka AGM series batteries. Deka batteries are still made in the USA and are OEM on almost all heavy duty truck manufactures. I believe they outperform anything Optima has to offer. I would go with 2 group 27 agm's or a 27 and a 31. Use the 31 for the stereo system. You will also want to use some sort of battery separator, switch or isolator. My suggestion is to use a Sure Power 1314. It is fully automatic, easy to install and priced very fair. Here is a link to some more info on the sure power unit.

http://surepower.com/pdf/separatorinterconnect.pdf

there are few different ways to go, here is some info that might get you started, I would use a battery seperator, plus here is a parts list here http://www.ase-supply.com/category_s/122.htm for all the little stuff that you will need..

If you have a dual battery switch and no isolater, do you want to run it with both batteries on?? seems if you rig it so one is for stereo and one is for the motor thats your only option, I was considering having everything on one then just using the other as a backup if my 1st goes dead just to get the motor started.

Also is there any risk to over drawing out of the stock alternator charging two batteries at once?

didn't mean to hijack just thought these questions answered here may help

hey brett, can you use that 1314 with two different types/brands of batteries? i have a new optoma blue top as my primary at the moment.

trying to talk my wife into having Shane do half the work sooner than later (like next week) before our lake roosevelt trip. not sure if she's going to go for it, but i'm working on her.

also not sure how shane's going to wire it. with everything on 1 and 2 as backup, or audio on 2. either way, i need 2 batts and some sort of safety for starting.

should i just buy that stuff from him?

oh, and how about if you end up adding an onboard smart charger, does that change whether or not you can have different batteries? i used to have a chargetek 500 and may put one in this boat down the road for winter.

Bruce, it will work with 2 different types of batteries but isn't necessarily recommended. It is going to shorten the life of the batteries. Different batteries require different voltage for charging.

I don't think Shane sells the sure power unit although maybe I should talk to him and see if I can start selling it to him.

I agree with what Brett is saying concerning the Deka batteries. Another brand to look at is Lifeline. In high current applications I would stay away from the Optima. If you want the info as to why...pm me and I'll give it to you.

I do not agree with what Brett said about the using 2 types of batteries with the 1314. In this application I think it would be fine. They would only be paralleled for a short duration.

If the two were paralleled continuously I would agree. Two types of batteries paralleled for an extended period of time would self discharge much faster due to different internal resistance and self discharge rates.

Voltage is not the issue. The 1314 does however look at the battery voltage to judge the battery's SOC. When the starting battery has a low voltage(12.8),which is not very low, it parallels the second battery. By setting the switching voltage at 12.8 instead 11.5 (for example) they can somewhat assume the inrush current from the paralleled will be lower and the starting needed from both batteries would be lower. I would be curious to see the voltage spikes caused by swithing back and forth under load while charging. These could could pose a problem for the charging system. The claim of charging system protection is, IMHO, something put in place to protect the contactor in the 1314 from overcurrent. I can't imagine it would last for a long time.

I PM'd you Terry, curious to get your take on the "issue" with optima batteries.

I replied nu bu....

I'm a big fan of lifeline batt's too but if this guy want to save money just go with a optima because while they (lifeline's) are worth every dime IMHO they are still 300-500 for a battery. With two amps and only one battery you will spend lots of time idleing and bumming jumps from friends and maybe using your paddle.

i'm adding the 1314 per brett's recommendation, having my installer add a second matching blue top (both large) and hanging the stereo only off of battery 2.

terry forgive me, but i don't understand this part:

I would be curious to see the voltage spikes caused by swithing back and forth under load while charging. These could could pose a problem for the charging system. The claim of charging system protection is, IMHO, something put in place to protect the contactor in the 1314 from overcurrent. I can't imagine it would last for a long time.


why would there be any switching back and forth while under way? wouldn't it be combined while charging and isolated while either overdrawn or the boat was off?
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also what does soc stand for?

thanks

(Message edited by brucemac on July 16, 2008)

Bruce, SOC is state of charge. We sell the a ton of the 1314's and I don't think we have ever got one back for warranty.

A battery connected to the alternator in this case is a load. Anytime a connection is broken (under load) resistance will go up at the contact point and the voltage will spike for a short duration. Some contactors are design for switching underload but spikes are still created.

Contactors are rated for a certain current. Running over the max would cause the contact points to heat up and if the contacts are open under load this will cause damage to the contacts.

If the 1314 switched at a higher SOC (state of charge) this will lessen the amount of current through it when the batteries are combined for starting. For example, Looking at the spec sheet under "protecting the charging" they say that when the main battery reaches 13.2 it will connect the aux battery. During this point if the voltage pulls down the 12.8 it will swith back. When it connects the aux battery to the main and charging system current will flow from the main battery and charging system to the aux battery. This will charge the aux battery. By setting the low voltage at 12.8 instead of something lower they can assume max current flow and protect the contactor. It will continue to connect and disconnect the aux battery until the point where the combined voltage stays above 12.8 and the contact stays closed and both batteries are charged together.

So lets say your stereo is connected to the aux battery and you anchor for hours with the stereo running and discharge the battery way down. When you start the engine and it begins charging it will cycle through the above process alot longer til the aux battery is charged back up. I would be curious what the cycle life of this device would be.

If the aux battery is used just as a backup for starting it is probably a cheap, reliable and easy method for adding a second battery since the aux would not get drained as much.

SOC is state of charge measured in percent. For example. If I run a constant current charge of 25 amps for 3 hours in a 100 amp hour battery the state of charge would be 75%. If I discharge the a fully charged 100AH battery for 1 hour at a constant current of 25 amps I'll be at 25%DOD (depth of discharge).

Sorry for the book..................

Brett....What is the manufacturers cycle life of the contactor in the 1314?

terry is your above example assuming that the draw to recharge both batteries at the same time is enough to initiate the "protection" mode or is it a constant on/off charging state for battery 2 no matter what? i'm going to call surepower when i have time and see what they can tell me regarding this application.

Constant on/off state until the aux battery is charged enough to remain above 12.8 and switching stops. So after reading the spec sheet the aux battery is only charged to a voltage point of 12.8.

I think I'll give them a call to just to make sure I'm reading the spec sheet right and my theory of operation is correct.....I'll keep you posted.

terry, one thing i should reiterate in case it matters is that the stereo is the only thing that will be drawing off of battery 2.