Battery - Deep Cycle or Starting?

[hotajax]

OK, now that the boating season is only 3 short mos away, my local battery dealer tells me he's having a "sale" on Deka Marine batteries at the price of $100. Ouch - that's for one, I have two onboard.

The real question:
I have a 225 fuel-injected, Saltwater Series II Yamaha. Do I need deep cycle or starting?? Engine turns over EEEEEEZZZZZEEEEE. But I also have a FF, GPS, and stereo that are on most of the time when the engine is running. It's easier to charge the two of them at the same time if they are identical. Typical configuration with 4-position switch - Off, both, battery #1, or battery #2. I'd like to get two identical ones, but what do the old Grady owners say??

 

[catch22]

Imo a regular starting battery is fine for normal use, including leaving the gps and ff on for a few hours at a time. If you are using a lot of accessories, (with the motor off) your best bet is a dual purpose, (starting/deep cycle).

You don't want a straight deep cycle battery for starting use because they're designed for a long continues current draw, not a short high current draw... like starting.

Also, it's ok to temporarily charge both batteries at the same time, (like you mentioned) but don't leave the switch on "both" all the time. If one battery has a problem, it will pull the other one down. Run, (operate) on 1 battery at a time.

 

[G8RDave]

Deka makes a great battery. IMO you are better off getting two starting batteries since it doesn't sound like you spend much time running equipment with the motor off. My Dekas finally gave up last year and I switched over to 2 AGM dual purpose.

 

[CJBROWN]

Imo a regular starting battery is fine for normal use, including leaving the gps and ff on for a few hours at a time. If you are using a lot of accessories, (with the motor off) your best bet is a dual purpose, (starting/deep cycle).

There really is no such thing. A cheap deep cycle is probably the closest thing. A 'dual purpose' is a cranking battery with heavier plates so they'll stand discharging better.

You don't want a straight deep cycle battery for starting use because they're designed for a long continues current draw, not a short high current draw... like starting..

Not true. A deep cycle with sufficient CC's will work just fine as a starting battery.

Also, it's ok to temporarily charge both batteries at the same time, (like you mentioned) but don't leave the switch on "both" all the time. If one battery has a problem, it will pull the other one down. Run, (operate) on 1 battery at a time.

This is true, however as you say, if one gets a bad cell it will over charge the good one, and if left connected together will pull the good one down.


Jake, why not get one of each? Reserve the starting battery for just that, in the case that your deep cycle gets pulled down too far to start. A starting battery will have a very shortened life if discharged very much repeatedly. A large capacity deep cycle works really well for that type of application.

I don't know if your vintage of motor has the second charging circuit, but that's the best way to go to keep the reserved cranking battery topped up while keeping them isolated. If not, a regular battery isolator will work to keep them both charged when running.

Also, an outboard's charging system is pretty weak, and if you run a fairly large capacity deep cylce and run it down, it probably won't get completely recharged on an hour or two run back. Consider installing a good dual circuit charger, or at least get a good electronic battery charger that you can use shoreside.

Go here for all you want to know about 12 volt systems and batteries: http://www.ccis.com/home/mnemeth/12volt/12volt.htm

And there's a good book on marine 12V systems called The 12 Volt Battery Bible for Boats by Minor Brotherton. I have one from about 1984.

 

[JUST-IN-TIME]

http://www.marine-electronics.net/te..._faq/b_faq.htm

http://www.windsun.com/Batteries/Battery_FAQ.htm

 

[plymouthgrady]

You want matching batteries. Your batteries will only charge as stong as your weakest battery meaning a strong battery won't bring a weak one up, a weak one will bring a strong one down. Starting batteries are "all bark and no bite". Yes, they will start your boat and run your electronics but what you need to pay most attention to is the RC or the reserve capacity. You will kill starting batteries if you use them to run your electronics, especially when the engine is off. Livewell, washdown pump, stereo etc. will piss through your starting batts. If you keep discharging and recharging starting batteries, you'll blow out the cells (when the battery bows out on the ends).
Deep cycle batteries are designed for multiple discharges and recharges. With thicker plates, they take longer to discharge.
2 rules of thumb, you need 1 CCA for every CID of your engine and
2) the heavier, the better.

 

[Grog]

$100 for a good battery isn't a bad price.

I have 2 group 31 deep cycle batteries. A battery for each engine (200 SWSII), and they start the motors just fine. It's not the best set-up but there were other problems to take car of first. Why not get a group 31 deep cycle for the house and a 27 starting battery with an ACR to charge both?

 

[uncljohn]

I have one of each, but only a single engine. Sounds like you need 3 batteries- 2 starting and 1 deep cycle. I had trouble cold starting my 200hp engine from the deep cycle, so I added a starting battery, generally use that to start the engine and the DC for most of the other times, esp while anchored. Your stereo and GPS should both be direct-wired to the battery and are continuously drawing small current. And the bilge pump is hooked up too, so you want to be cautious about relying on a starting battery to keep all those other voltage draws ok.

 

[plymouthgrady]

3 batteries on a 20' single screw may be a little overkill.
I would not recommend hard wiring your stereo to the batt. You will lose your presets but the draw will kill your battery. The bilge is also hard wired but only draws when there is water present. The constant charge/discharge cycles of a starting battery will torch it.

 

[uncljohn]

The stereo won't drain a deep cycle battery unless you go months w/o using your boat. If you use it somewhat regularly, or put a charge on it once a month when not in use, the stereo and GPS won't drain your battery.

If you use it less than once a month, then not hard wiring it is an option.

And I thought he was talking about a boat w/ dual outboards. Yes, 3 batteries on a single screw would be overkill unless you were running massive electronics. With a single, you'd be fine w/ 1 starting and 1 deep cycle.

 

[plymouthgrady]

I misread your post. I thought it said to hard wire to the starting batt.
Should be fine on a deep cycle.

 

[jethro99]

You want matching batteries. Your batteries will only charge as stong as your weakest battery meaning a strong battery won't bring a weak one up, a weak one will bring a strong one down.

Where did you get this from? It is completely untrue.

Think about it. Assume that one battery is twenty feet east of the rectifier/regulator. The other battery is twenty feet west of the R/R. Current is flowing out of the R/R to both batteries, with each battery getting an amount of current that is dependent upon the difference in voltage between the R/R and the battery. The lesser charged battery will get more current and the higher charged battery will get less current. The weaker battey will have no effect on the stronger battery.

 

[CJBROWN]

You want matching batteries. Your batteries will only charge as stong as your weakest battery meaning a strong battery won't bring a weak one up, a weak one will bring a strong one down.

Where did you get this from? It is completely untrue.

Think about it. Assume that one battery is twenty feet east of the rectifier/regulator. The other battery is twenty feet west of the R/R. Current is flowing out of the R/R to both batteries, with each battery getting an amount of current that is dependent upon the difference in voltage between the R/R and the battery. The lesser charged battery will get more current and the higher charged battery will get less current. The weaker battey will have no effect on the stronger battery.

Uh, no, your statement is the one that's completely untrue. I have witnessed it personally with a bank of batteries on a couple'a v-8's in a 40 footer. Here's how:

A voltage regulator senses the draw needed from a specific voltage and puts out amps accordingly for recharging. If one battery in a bank has a bad cell it makes the whole bank look like it is less discharged than it is and will increase the amps charging. The good cells/batteries will get over charged and even boil the water out of them from being over-charged.

I could see one engine putting out a LOT more voltage than the other. Sure enough, the one with the higher voltage on the ammeter was the one with a bad battery and boiled out cells on the other batteries on that bank. The other bank was all level and fully charged with a normal ammeter/volts indicated.

If you connect two (or more) batteries together in series they will always try to equalize. If one has a bad cell that won't take a charge the other cells will be constantaly drawn down to it's level - discharged!

 

[plymouthgrady]

You want matching batteries. Your batteries will only charge as stong as your weakest battery meaning a strong battery won't bring a weak one up, a weak one will bring a strong one down.

Where did you get this from? It is completely untrue.

Think about it. Assume that one battery is twenty feet east of the rectifier/regulator. The other battery is twenty feet west of the R/R. Current is flowing out of the R/R to both batteries, with each battery getting an amount of current that is dependent upon the difference in voltage between the R/R and the battery. The lesser charged battery will get more current and the higher charged battery will get less current. The weaker battey will have no effect on the stronger battery.

From my Exide driver, my boat yard mechanic, every National Sales meeting I've been to, personal experience, and a little bit of knowledge.

 

[Grog]

Why would you want both batteries wired in parallel? That's the worst way to do it. Either have a ACR to charge both or a 3 way switch (off, 1,2 both). If two batteries are wired in parallel, the voltage is the same at either battery. If one has a bad cell it's going to mess you up. Outboards don't have that much charging capability. if a battery is NG it may not have the power to charge both.

 

[CJBROWN]

Why would you want both batteries wired in parallel? That's the worst way to do it. Either have a ACR to charge both or a 3 way switch (off, 1,2 both). If two batteries are wired in parallel, the voltage is the same at either battery. If one has a bad cell it's going to mess you up. Outboards don't have that much charging capability. if a battery is NG it may not have the power to charge both.

It's not common for the outboards. You'll see a couple of deepcycles, or one DC for 'house' and a starting for each motor.

In larger vessels and RV's you'll see banks of batteries wired parallel for reserve capacity, onboard chargers powered by the genset, and solar chargers. I have seen installations where there were for and six batteries wired together in banks. However, the rule is that if you replace one you replace them all, and they must all be of the same size and capacity. Some installers even go so far as to match batteries for sets based on the voltage of their charged state.

But yeah, for the OP, Jake, a deepcyle and a starting is what he needs. Run on the deepcyle for everything and keep the starting batt reserved for when it's really needed. I've been doing that for a couple of years now and it works out great. Unfortunately, the starting batter just never gets used - cheap insurance though, and it will last many years since it stays charged up.

 

[ahill]

My dealer said that deep cycle take too long to recharge.
They use 650 Deka's for house & start.
I generally recharge on the hook with a 2000 Honda Gen & recharge is relatively quck

 

[CJBROWN]

My dealer said that deep cycle take too long to recharge.
They use 650 Deka's for house & start.
I generally recharge on the hook with a 2000 Honda Gen & recharge is relatively quck

Recharge time is a function of battery capacity, level of current charge, amps in, and charger capacity - not the type of battery.

If you review the link content provided earlier in the thread you'll find recommend charge rates based on battery capacity/size and type, ie; AGM, wet cell, ect.

In a sense, they're right in that large deep cycle batteries, while offer a large reserve capacity to run things, will take a very long time to recharge if completely or severly discharged. Certainly more than an outboard can do on a run back to the bay. However, if you need the capacity and have a way to recharge once back to port, then they could conceivably fulfull that intended purpose/need.

I run a group 27 deep cycle to power, sometimes all at the same time, lights, vhf radio, finder/plotter, stereo with amp and sub, live-well pump, all with the motor shut of from time to time. It always seems to get charged back up, although I do top it off occasionally with a shore-side automatice electronic charger.