Battery problems

About powering boats with electricity

Moderator: BruceDow

Dbeaul1444
Posts: 17
Joined: Sat May 31, 2008 5:19 pm

Battery problems

Postby Dbeaul1444 » Sun Jun 20, 2010 7:52 am

When I put her away she was running good....I had a Cabella Pro Sport battery charger on it all winter. When I went to start it up my voltage meter says I only have 30 volts ( I need 36) and my fuel gauge says I am low/empty. I purchased deepcycle batteries last summer. Is my battery charger not getting the job done? Why aren't they fully charged?

User avatar
kens
Posts: 4483
Joined: Wed Nov 12, 2003 5:25 pm
Location: Coastal Georgia

Re: Battery problems

Postby kens » Sun Jun 20, 2010 8:53 am

I assume you have 3 12v batteries in series?
if so, then disconnect them from each other and check them as individual 12v batteries and locate the bad one.

.......are you charging them from a 36v charger ,or, charging them as individual 12v batt each?
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

Dbeaul1444
Posts: 17
Joined: Sat May 31, 2008 5:19 pm

Re: Battery problems

Postby Dbeaul1444 » Sun Jun 20, 2010 2:21 pm

I have 3 12 v batteries in series. The battery charger I have has three connectors, Each one goes to a battery and has a - + connector. If I had a bad battery wouldn't my voltage meeter be at 24 v? I don't know why I am at 30 v ...that confuses me.

Trackhappy
Posts: 1411
Joined: Wed Feb 17, 2010 5:42 pm
Location: Sunshine Coast, Queensland, Australia. Building Gentry.

Re: Battery problems

Postby Trackhappy » Sun Jun 20, 2010 4:31 pm

Dbeaul1444 wrote:I have 3 12 v batteries in series. The battery charger I have has three connectors, Each one goes to a battery and has a - + connector. If I had a bad battery wouldn't my voltage meeter be at 24 v? I don't know why I am at 30 v ...that confuses me.


Each battery is made up of 6 2 volt cells in series. One type of failure is where a cell shorts out, thus you lose that voltage. If you lost 3 cells for example you end up with 30 volts across all batteries. The other type of failure is a high resistance, where a cell can't keep up with the demand placed on it. In this case the eventual voltage depends on the load drawn, so could be anything. Because the cells and batteries are all in series, a failure of any cell can cause this.
Kens is right, separate them and find the crook battery. As far as tha actual cause, could be a faulty charger, could be a faulty battery. How old are they? When it is hooked up on charge, use a multimeter to measure the voltage across each battery. If the charger is ok, each battery should have a float charge across it of around 13.5-13.8 volts. More than this on a permanent charge is too much, less will not charge properly.

You could try charging each battery separately to see if they come up. probably best to take them to a shop and put their tester across them after charging. Their tester measures the voltage with a known drain applied. Take them to where you brought them if you can, maybe they have an extended warranty or something.

Best of luck.

Oh, and clean all the connections, it may be just a bad connection losing voltage. Even fuses can do that.
By the time I have built a boat, I'll be ready to build a boat....

Dbeaul1444
Posts: 17
Joined: Sat May 31, 2008 5:19 pm

Re: Battery problems

Postby Dbeaul1444 » Sat Jul 03, 2010 6:46 am

I did in fact have a bad battery so now I am up and running.

My question now is, what is my running time?

When my three batteries are fully charged, each is at about 13.25 volts. The meter says I have about 40 volts when I start. By the way I have a 36 volt set up. Therefore, what happends when I get below 36 volts? I have been checking my batteries throughout the day when I am on the water. They go from about 13.25 to about 12.2 volts. The other day one battery went down to 11 volts. Am I correct in saying that my run time is essentially the difference from 40 at start, down to 36 and end, which is 4 volts??????

User avatar
galamb
Posts: 811
Joined: Sat Jan 17, 2009 1:37 am
Location: Inverary, Ontario - Cuddy Sport (modified)
Contact:

Re: Battery problems

Postby galamb » Sat Jul 03, 2010 9:20 am

Many electronics and electric motors rated as 12 volts have a cut-off at about 10.5 volts (so won't work or auto-shutoff below that).

You would have to research the specific requirements of your system to find out what it's extreme lower end is.

When running deep cycle batteries you are often more concerned with "amp hours" than voltage when trying to figure how much you need.

So say the total amp hours available from your combined battery banks is 75 @ 36 volts and your motor (burns) 25 amps/hr, then you have 3 hours of run time

To increase your amp hours (run time) you would need to add batteries and run both parallel and series circuits to increase your amp hour capacity without changing your 36 volt requirement.
Graham

Yes, Plywood is "real" wood :)

A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

User avatar
Cranky Badger
Posts: 268
Joined: Mon Feb 02, 2009 12:06 am
Location: BC coast

Re: Battery problems

Postby Cranky Badger » Sat Jul 03, 2010 1:17 pm

Deep cycle batteries will last way longer if you don't let them get below 50%
That's will be around 12.2 volts for flooded lead-acid.

Or you could take a hydrometer with you initially to set up a baseline - 50% will be about 1.19, full is 1.265

That would tell you exactly what runtime you can expect.
-Brian

"Do or do not. There is no try."
- Yoda

Trackhappy
Posts: 1411
Joined: Wed Feb 17, 2010 5:42 pm
Location: Sunshine Coast, Queensland, Australia. Building Gentry.

Re: Battery problems

Postby Trackhappy » Sun Jul 04, 2010 4:15 am

A standard lead acid battery will fairly quickly drop to 12 volts under a nominal load. "Flat" depends on the manufacturers low voltage figure, but generally 11.5 volts is a safe minimum to stick to. Lower than that risks battery damage. The problem with batteries in series is that the total voltage can be ok, but a single battery can be below the minimum and hence suffer damage.
By the time I have built a boat, I'll be ready to build a boat....

Dbeaul1444
Posts: 17
Joined: Sat May 31, 2008 5:19 pm

Re: Battery problems

Postby Dbeaul1444 » Sun Jul 04, 2010 8:35 am

I checked my batteries they are Interstate SRM-29 Marine Deep Cycle. I looked up the specs online and it says for each battery the Hrs at Ampere Load 5 @21 15 @ 6.4 then 25 @ 3.4 ( I am not sure is it is 5 hrs at 21 amps or 21 hrs at 5 amps?) Can someone tell me which what it goes? I understood the explanation above about how 75 amps hrs with a motor buring 25 amps per hour equals 3 hrs. However, I can't seem to put it all together based on these numbers. Also I have an amp meter that came with the boat, if I hooked it up whould it tell me how many amps per hour I am burning or how many amps I have....I guess I need to know how to read an amp meter. Thanks to everyone for all your help and happy 4th of July.

User avatar
J Purcell
Posts: 145
Joined: Wed Mar 03, 2010 9:00 pm
Location: Puyallup, WA

Re: Battery problems

Postby J Purcell » Sun Jul 04, 2010 9:15 am

I looked up the specs online and it says for each battery the Hrs at Ampere Load 5 @21 15 @ 6.4 then 25 @ 3.4 ( I am not sure is it is 5 hrs at 21 amps or 21 hrs at 5 amps?)


21 hours at 5 amps. Your batteries should be about 100 Ah (or 105).

Divide 105 Ah by 5 Amps/hour and it should last 21 hours. If you are drawing 21 amps/hour then it should last 5 hours (although it wont).

Optima has a good explanation of Amp hours http://www.1st-optima-batteries.com/amp_hours.asp.

For why the ratings drop off for high loads check out http://www.windpowerunlimited.com/batteries/Amp_Hours.htm.
Jeremy

Dbeaul1444
Posts: 17
Joined: Sat May 31, 2008 5:19 pm

Re: Battery problems

Postby Dbeaul1444 » Sun Jul 04, 2010 10:08 am

Given that my batteries are in series (three 12v batteries) (each with 100 amp hrs) does that mean I have 300 amp hours? Also, how many amps is my motor using per hour. How do I find that out? (My motor is a 36 volt motor)

User avatar
J Purcell
Posts: 145
Joined: Wed Mar 03, 2010 9:00 pm
Location: Puyallup, WA

Re: Battery problems

Postby J Purcell » Sun Jul 04, 2010 1:55 pm

Running in series just increases the voltage. Running in parallel increases the capacity.

A good explanation http://www.batteryuniversity.com/partone-24.htm

You probably need to get the amp draw of your motor from the manufacturer if you do not have the manual.
Jeremy

Dbeaul1444
Posts: 17
Joined: Sat May 31, 2008 5:19 pm

Re: Battery problems

Postby Dbeaul1444 » Mon Jul 05, 2010 7:24 am

I am getting it. I figured I would post what I learned to help someone else.

I have three 12 v batteries in series. That is + to -, + to -, + to -. Each battery has 105 amp hours. Because they are in series the volts go up to 12+12+12 = 36, but the capacity of 105 amp hours stays the same. If they were in parallel + to + and - to -, the three batteries together would only have 12 volts but it would have a larger capacity of 315 amp hours. I found out my motor draws about 40 amps and hour at medium cruising speed. Therefore, 105 amp hr capacity divided by 40 amps an hour = about two and half hours of running time.

I also found out that my system has a shut off when the batteries get below 32 volts. Apparently this protects the system from draining and damaging the batteries. However, I have learned to make sure the batteries are at the same or approximately the same voltage. In other words, you don't what one battery to be at 8 volts and the others at 13 volts = 34, otherwise you will damage the low battery.

If anyone is interesting in my boat restoration, I have posted a thread uder "power boats" under "16' 1902 Fan Tail Launch."

Thanks for all your help and hopefully this thread will help someone else.


Return to “Electric Power”

Who is online

Users browsing this forum: No registered users and 2 guests