2 batteries different sizes

[stevecut55]

I have two batteries conected to a battery switch. one battery is 1000 CCA, the second is 600 CCA. I have no problem starting my motor with either battery. I only use one or the other. I know not to switch the batteries while the motor is running. My question is this, can I start the motor with the switch in the both position, and will it charge both batteries while the motor is running, without doing any damage to either battery or the charging system.

 

[JB]

Re: 2 batteries different sizes

Yup.

 

[JUSTINTIME]

Re: 2 batteries different sizes

yes u can charge but they will not get fully charged
never run Ur switch on both
u should have a starting battery and a deep cycle
also make sure u have a make not break switch this way u can switch over to either battery while the engine is running

 

[stevecut55]

Re: 2 batteries different sizes

yes u can charge but they will not get fully charged
never run Ur switch on both
u should have a starting battery and a deep cycle
also make sure u have a make not break switch this way u can switch over to either battery while the engine is running

 

[stevecut55]

Re: 2 batteries different sizes

If you could. What is a make not break switch? I have the red Perco switch, where one battery goes to the (a) post and the other goes to the (B) post and there is a common that goes to the motor. Also why won't both batteries fully charge?

 

[JUSTINTIME]

Re: 2 batteries different sizes

a make not break

it makes the connection before it breaks the connection

both batteries will not fully charge unless u have a high amp charging system

 

[bruceb58]

Re: 2 batteries different sizes

Both batteries will charge just fine in the both position.

You should just buy a combiner that allows both batteries to charge while the engine is running yet disconnects them while not running.

Blue Sea makes an excellent one.

http://www.bluesea.com/product.asp?Product_id=53476

They are less than $100.

 

[Boatist]

Re: 2 batteries different sizes

Yes you can put it in both postion and charge both batteries just fine. Only time it may be a problem is if your bigger battery is dead. When you switch to both the smaller charged battery will try and charge the bigger dead battery. If it dead enough it may run down your starting battery before you can start the motor.

Another time may not be a good idea to run in both is if you have a dead large battery and a low amp charger on a outboard. If your charger is low amps like 8 amps and trying to charge a large deep cycle it could overheat and do damage. With large alternator of 30 amps or more I think it works Good to charge both.


it is more comnonly called a make before break switch.
Meaning that battery B connects (makes) before Battery A disconnects (breaks). Perko makes both type switches.

With the make before break switch you should be able to turn switch with the motor running and not damage your alternator. However you can not turn thru off with the motor running as it will blow your alternator.

Personally I prefer a battery isolator to charge both batteries. With a battery isolator you can always turn your switch with out blowing your alternator as the load of both batteries is felt by the alternator. Also if the battery connection corodes to the battery you are switched to it still will not blow your alternator because the other battery is still connected. Batteries are isolated from each other all the time unless you set the switch to both or all.

I used a battery isolator on my boat since 1980 with a group 24 starting battery and a group 27 deep cycle battery and never have had a battery not last at least 6 years. It so simple and there no big surges when switches close or open. I will say that I do not have a trolling motor on my deep cycle just lights and electronics.

I also use a battery isolator on my 1974 truck to charge my camp trailer battery when have it hooked up. Also have had no problems with batteries in the truck or trailer.

 

[Dunaruna]

Re: 2 batteries different sizes

[colour=blue]

With the make before break switch you should be able to turn switch with the motor running and not damage your alternator. However you can not turn thru off with the motor running as it will blow your alternator.

One of the perko range has 'Alternator field disconnect' which protects the alt if the switch is turned off.

 

[bruceb58]

Re: 2 batteries different sizes

In the 80's isolators were your only choice...now combiners are what is best because you don't have all the drawbacks of the isolators not allowing your battery to completely charge.

Boatist, all newer trucks have relays that disconnect the trailer battery charge circuit when the truck is not running...just like a combiner.

 

[Boatist]

Re: 2 batteries different sizes

Dunaruna is right about the "alternator field disconnect circuit" However it only works with external regulators which are getting pretty rare in the USA. The circuit disconnects the field winding in the alternator turning off the charging before the switch breaks. If you have an external regulater it is worth the extra $10 Bucks.

 

[Dunaruna]

Re: 2 batteries different sizes

[colour=blue]You are correct sir, I should have read the fine print - my bad.

 

[Boatist]

Re: 2 batteries different sizes

Dunaruna
Your post was great lot of older alternator out their. My 1980 has a external regular.

 

[bruceb58]

Re: 2 batteries different sizes

Even newer alternators with internal regulators have inputs where you can disconnect the field.

 

[planktonguy]

Re: 2 batteries different sizes

I have a related question for this thread. I have a bank of battery sucking sensors for my boat (I study lake plankton and oxygen) that I have previously powered (on my old beast) using several deep-cycle batteries. My new (to me) boat has an 9.9 Evinrude electric-start motor so I want to try to maintain a battery bank. Just FYI, my sensors (and computer) usually drain 2 (75 AmpHr) deep-cycle batteries in the course of the day's research.

So here is the question: Can I use one dual-purpose battery for starting/basic boat electronics and another bank of 2 identical deep-cycles in parallel, or am I just making the situation more complicated than it needs to be? I have the same Perco switch as in this thread, but not installed since currently the boat only has the single start/deepcycle battery.

Your expertise would be welcome. Thanks.

I have two batteries conected to a battery switch.

 

[Dunaruna]

Re: 2 batteries different sizes

[colour=blue]Are you hoping to maintain 3 batts with the 9.9 alternator?

 

[steelespike]

Re: 2 batteries different sizes

Your 9.9 will not have the output to do much for your Deep cycles based on your description.Basic rule of thumb it takes 2 hours charge for each hour of use.
If you are draining your 2 75 amp hour batteries below 40% about 12.25 volts you are shortening their cycle life.
Based on your use I think you need a couple of 130 amperhour batteries.You won't be so hard on their cycle life and they will perform better for you.They will be pretty expensive at around $150 each for Trojans.But you will be surprised at the performance.Of course there are others out there Deka makes a pretty good
105 amperhour battery but keep in mind the higher the rating the longer the cycle life.
Allways try to recharge your deep cycles as soon as possible even if only an hours use never let the batteries stand partially discharged.
Use a regular starting battery for your motor and simply just charge it.Don't bother trying to do the deep cycles off the motor theres not enough charge there to notice.Your 2 deep cycles will take longer to recharge than one.

 

[planktonguy]

Re: 2 batteries different sizes

Thanks for the info. This confirms some of my ideas on this. I purchased the 75 amp-hr batteries because they were smaller and could be removed from the old boat and hauled up to my lab for charging. I didn't expect that the alternator would keep up, but was hoping that it would extend my sampling time and maintain the charge slightly. I unfortunately still don't have an outdoor outlet at the Univ location where I have to store the boat, and haven't yet come up with funds to install a solar panel of sufficient size to act as charger.

In your opinion, after a day of sampling (let us say we almost deplete the 120 amp-hr batteries), how long would it take to recharge them with an onboard battery charger (i.e. such as they sell at Cabela's or similar)? If the time is short enough, I might be able to do it outside of our building, but I was always told that deep-cycles must be charged slowly to maintain them.

Appreciated. Warren

Your 9.9 will not have the output to do much for your Deep cycles based on your description.Basic rule of thumb it takes 2 hours charge for each hour of use... Based on your use I think you need a couple of 130 amperhour batteries.

 

[bruceb58]

Re: 2 batteries different sizes

You shouldn't be discharging your batteries over 50% if you want them to last as long as they can. The deeper you discharge them the shorter life they will have.

You can do the basic math on the charging and then add 50%. For example, if you have a 100 Amp/hour battery that is discharged 50% you have 50Amp hours to charge up. If you use a 10 Amp charger, it will take around 7.5 hours to recharge using those numbers.

The 2 hours charge per hour of use number means nothing unless you know what your discharge rate is.