Battery question - solar charger

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bartmac
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Re: Battery question - solar charger

Post by bartmac » Mon May 13, 2013 8:54 pm

The charger would "see" one voltage ie the combination of the 2...hence the averaging....just because the batteries are in parallel they are not actually the same voltage especially if usage is being taken from only one. This is demonstrated when you have a 2 battery system with a switch...when you watch the voltmeter switched to 1 then switch to 2 and then to combined....the meter will show somewhere in between to the two batteries. The equalizing of 2 or more batteries does not actually occur...there's not enough pressure (read voltage) for one battery at say 12.6-12.7 to charge another of lower voltage

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Sumner
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Re: Battery question - solar charger

Post by Sumner » Mon May 13, 2013 10:13 pm

bartmac wrote:.....there's not enough pressure (read voltage) for one battery at say 12.6-12.7 to charge another of lower voltage
A little story.

My buddy and I were in the Navy in Bremerton, WA and left our ship that was in dry dock and went over to the parking lot to get our car that we owned jointly. There was a guy sitting there we knew. He had a battery on the ground in front of his car with battery cables going to the battery in the car. We asked him what he was doing. He said "I'm waiting for the electricity from the one battery to go into the other so I can start the car" :P ,

Sum

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bartmac
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Re: Battery question - solar charger

Post by bartmac » Mon May 13, 2013 11:29 pm

There's a lot of supposed experts when it comes to electrickiery ......then again an EX is a has been and spert is a drip under pressure....not sure if it translates from OZ to US but you get the drift

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Re: Battery question - solar charger

Post by Rick Westlake » Mon May 13, 2013 11:34 pm

bartmac wrote:There's a lot of supposed experts when it comes to electrickiery ......then again an EX is a has been and spert is a drip under pressure....not sure if it translates from OZ to US but you get the drift
In fookin'asshole-Yank, 'spert' is spelled with at 'u' as in 'spurt.' But you're right about the 'drip under pressure.'

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Rick Westlake
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Re: Battery question - solar charger

Post by Rick Westlake » Mon May 13, 2013 11:37 pm

Sea Wind wrote:
Two batteries Perko switch, controller hooked up to the switch, I charge house, or starter or both by using the Perko switch.
I have the same setup
Take a look up the gate end of Greg's line-up. Bossa Nova has a 'duo' circuit setup ...

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Re: Battery question - solar charger

Post by kurz » Tue May 14, 2013 2:30 am

Well, I do not answer the first question. But I manage very well with just one batterie as follows:

I mounted a 10W solar panal on the arch.
The most power takes the coling box. All the lights are in LED. The coling box has a switch that turns out when volt is low. I realized that this does not work properly.
So I bought a relais that can turn out at such a volt that I can chose. So I put this relais this way, that that cooler just gets on WHEN SOLAR POWER IS AVALABLE DIRECTLY (I guess 13 V).

So now all the problem are solved. Even in wheather with clouds the fridge is cool enough, turns out in the night and gets on early in the morning.

The cabin/runing lights are LED, so I do not take out much AH.
Is to say that I have no need vor TV etc.
For me works great, is not heavy for trailering (and in an emergency the engine can be rope startet, of course I had a test on this: Take a long rope and stand down in the cabin!).

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Re: Battery question - solar charger

Post by Catigale » Tue May 14, 2013 4:07 am

battery in the car. We asked him what he was doing. He said "I'm waiting for the electricity from the one battery to go into the other so I can start the car" ,
Should have told him to put his ear to the cables so he could listen for the sounds of the electrons running up the wire ...when it stops, he would know it was finished. Sounds like tiny feet..

:D

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Re: Battery question - solar charger

Post by Boblee » Tue May 14, 2013 7:48 pm

Obelix
It may seem that way but when you tie the two batteries hard together the voltage MUST equalize or average but yes they will try to balance like water finding it's own level but slower and in the meantime the fully charged battery could be getting over charged or the flat battery won't get enough and if enough time is not allowed for full charging could be put back into service in a constantly undercharged state.
My method is to leave all batteries linked to discharge/charge equally except in some circumstances where the start battery may be isolated to preserve it for it's primary use but there is no doubt that the preffered method should be to charge them independently, this is just not feasible with our useage and I am happy with 7 years life and still going.

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Re: Battery question - solar charger

Post by DaveB » Tue May 14, 2013 8:01 pm

And as you know, a good battery jumpstarting a dead sulfated battery is a waste of time trying to charge and best to quick jump start so they have the alternator to get them home.
Dave :)

) He said "I'm waiting for the electricity from the one battery to go into the other so I can start the car" :P ,

Sum)

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Re: Battery question - solar charger

Post by rszobel » Wed May 15, 2013 8:49 am

OK so here is what i have installed -- took some time to find the info ....
here is a post from the previous owner of the boat with the info on the panels and controller.

http://www.macgregorsailors.com/modt/in ... ?view=1477

would the following work to replace the existing charger and adding an additional battery ??

Ganz 10 Amp Dual Charge Controller
http://www.defender.com/product.jsp?pat ... id=1802202

Any help would be greatly appreciated. I really don't know a lot about electronics and want something really simple -- it seems like the dual charge controller would fit my needs. Any advice ?

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Re: Battery question - solar charger

Post by Obelix » Wed May 15, 2013 9:07 am

Boblee,

This is exactly what I said; two batteries permanently connected in parallel will have the same voltage. If you parallel them only for charging then you can see different voltages at the begin of the charge, that's why the manufacturers of combiner relays insist not to shorten the interconnecting leads so the wires can act as current-limiting resistance until voltage-equalization takes place.

Obelix

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Re: Battery question - solar charger

Post by rszobel » Wed May 15, 2013 7:02 pm

I am the one that started this thread and finally was able to post the exact equipment that i have and have a question that i would like to hopefully get an answer to -- see above post by me showing specifics on equipment and the controller that i was considering -- a dual solar controllerr -- will it work for what i want to do - a simple solution if so.

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Re: Battery question - solar charger

Post by DaveB » Wed May 15, 2013 8:44 pm

You have twin 12 watt solar panels that are outdated.
Get a 40watt panel (21 in. x 24in) for $58 and a cheap 4amp controler.
If you get twin 29 group batteries in parrel than you may want two 40 watt panels with a 6 amp controler like I have.
Hook you wires from solar to battery selector switch than to controler than to house or engine battery.
I just have a direct wire to controler than to twin house batteries as the house is the ones that depleate and need charge.
I have refig. and computers that draw down battery and only use the twin 40 watt solars if on anchor more than 3 days or if sailing . Motor on recharges Bat.
You haven't stated what your elect. demands were.
I am in the prossess of redoing my bimini top and going to put snaps with tags on them to hold the twin 40 watt solars in place with quick release.
Just completed all cockpit and lower chusions with Sunbrella and the Admrial has done a excellent job . Combination of hard foam and closed cell foam along with Velcro and zippers .
Will do a update later with pictures in how to turn a sunbrella 20 ft.umbrella into a MacX.
Dave
rszobel wrote:I am the one that started this thread and finally was able to post the exact equipment that i have and have a question that i would like to hopefully get an answer to -- see above post by me showing specifics on equipment and the controller that i was considering -- a dual solar controllerr -- will it work for what i want to do - a simple solution if so.
Last edited by DaveB on Wed May 15, 2013 9:04 pm, edited 2 times in total.

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Re: Battery question - solar charger

Post by Boblee » Wed May 15, 2013 8:59 pm

rszobel
Never seen one like that but it looks good although can't tell what the display is or do you need the meter advertised seperately, you would if like myself am always checking to make sure the batteries stay charged but we have a fridge that creates abnormal load.
If you are going to use different batteries for different jobs you either need to charge them seperately or hard wire them so they both charge and discharge together, the start battery can be protected either manually or with a low voltage protection to keep enough charge for it's individual duty or with a perko switch.
We actually run three batteries from time to time with two hooked together but at opposite ends of the boat for house batteries and the start battery which is linked through the perko switch and unless I think voltage is getting down a bit stays linked to the other two but all through very heavy wires to combat voltage drop.
For what you are doing and unless you expect to draw both batteries down to the stage where they won't start the motor why bother? but it certainly won't hurt having it hooked up to that setup but remember then if you want to use the start battery as a helper you will need to have a manual connect between them anyway.
The biggest mistake made by most people when charging batteries is how long they need to get full charge it is not just a case of even putting a eg 25 amp charger on for 3 hours if you want to put 75 amps into a battery, battery type, slower charge and allowing about 25% more for loss etc need to be allowed for.
The mod setup is great for a trickle charge but at even ideal conditions the max you would get is about 9.5 amps per day but more likely 3-4 amps if that suits it's good if not it needs to be bigger but if you only use about 20 amps (240w)out of the batteries when on the boat and it has a week to recover the batteries will be kept in good order.
obelix
As above if you are using the batteries for different purposes ie where one might draw right down, you need to really charge them seperately to get the best results, even relying on the leads to create a vd is very hit and miss but if as I suspect the controller shown by rszobel charges each battery seperately you get the best of both worlds except you can't use the batteries to power the same downstream circuits without a manual combiner.
If you use leads that are too small or long between your batteries when connecting them in parralel sure you will see different voltages at all points along the circuits but if your fully charged battery is close to the charging source and it is a fairly large source the regulater will sniff out the lower voltages and maintain a higher voltage than optimal on that battery until the second battery eventually charges which will depend on many factors including voltage drop/ current
and if the resistence is too high it may never charge or not charge quickly enough as the voltage at the battery terminals could be only allowing it to trickle charge and this could be especially true if you add a load on the circuits.
My own setup while not foolproof works because I am aware of it's limitations but with smaller interconnecting wires or dissimilar batteries there would be problems.
Every situation is different but very rarely is it as simple as many make it out to be unless you charge each battery seperately and allow the batteries to charge to optimum levels for their type and don't mix types.
We have rescued plenty of people who had been sold and told their setup would work but didn't by experts.

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Re: Battery question - solar charger

Post by rszobel » Fri May 17, 2013 9:02 pm

I have not taken the time yet to calculate my typical draw but I am sure that it is very low. I only have a chart plotter, VHF, stereo/cd, all cabin lights, running lights, etc. are LEDs. I really don't see myself out for more than maybe 3-4 days at a time and even at that I would likely be at a marina for 1 or 2. I do not have any kind of meter attached to my existing battery. I just thought it would be best to have a house and a separate starting battery for safety and redundancy. Don't have a fridge or anything like that with large draw. So far my single battery along with solar panels to trickle charge works well. I usually only use boat on weekends and it has plenty of time to recover by trickle charging.

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