oakleyb
Well-Known Member
I would like to keep spare battery on boat fully charged by using a cheap solar pannel. The battery wont have any load but be purley for when others fail. Is this a good idea
Solar
- Thread starter oakleyb
- Start date
aknight
Well-Known Member
In principle, yes. A solar panel will keep your battery topped up nicely between uses.
However, in the solar panel world, a cheap panel usually won't produce very much charge. It depends on your definition of cheap. If you're thinking of the Maplin-type £9.99 special, it's great for floating your car battery (e.g. when parked at the airport for a week or two) but in reality, it's regular charging from the alternator that is truly charging the car battery, not the solar panel. That kind of small solar panel is in essence a trickle charger and is putting in a float charge at best. Rated wattages vary but will usually be in the range of 6 - 9 watts.
If you really want to put charge into a battery from solar energy - i.e. if the battery is not fully charged when you leave the boat, but you want it to be fully charged when you return - you will need a panel of a reasonable size. People tend to disagree over what the minimum size is, but few would suggest less than a 12-15W panel unless your battery was very small.
Normally, people conduct - some more scientifically than others - a power consumption audit by adding up all the draws on the battery and working out from that how much charge they need to replace. Your post isn't very detailed but it sounds as if that would be a bit OTT in your case. Howeve, you should try to get some idea of what your power consumption is on an 'average' day on the boat, so you know how much charge has to be replaced.
Generally fitting a regulator (controller) between the solar panel and the battery is good investment when the rated amps of the panel exceed 1% of the battery capacity in amps. It will protect the battery from overcharging and, in case the panel itself has no blocking diode fitted, the controller will also usually prevent reverse drain on the battery at night.
However, in the solar panel world, a cheap panel usually won't produce very much charge. It depends on your definition of cheap. If you're thinking of the Maplin-type £9.99 special, it's great for floating your car battery (e.g. when parked at the airport for a week or two) but in reality, it's regular charging from the alternator that is truly charging the car battery, not the solar panel. That kind of small solar panel is in essence a trickle charger and is putting in a float charge at best. Rated wattages vary but will usually be in the range of 6 - 9 watts.
If you really want to put charge into a battery from solar energy - i.e. if the battery is not fully charged when you leave the boat, but you want it to be fully charged when you return - you will need a panel of a reasonable size. People tend to disagree over what the minimum size is, but few would suggest less than a 12-15W panel unless your battery was very small.
Normally, people conduct - some more scientifically than others - a power consumption audit by adding up all the draws on the battery and working out from that how much charge they need to replace. Your post isn't very detailed but it sounds as if that would be a bit OTT in your case. Howeve, you should try to get some idea of what your power consumption is on an 'average' day on the boat, so you know how much charge has to be replaced.
Generally fitting a regulator (controller) between the solar panel and the battery is good investment when the rated amps of the panel exceed 1% of the battery capacity in amps. It will protect the battery from overcharging and, in case the panel itself has no blocking diode fitted, the controller will also usually prevent reverse drain on the battery at night.
VicMallows
Well-Known Member
How can it be anything other than extra 'insurance'? Just make sure your 'cheap solar panel' incorporates a diode so that you don't in fact end up discharging it every night. Even without a panel to keep it topped up the self-discharge of a good battery would be negligible over a couple of months so you could just charge it from mains once or twice a season (take it home if no mains power otherwise available).
Vic
Vic
simonfraser
Well-Known Member
i would spend the time, effort and money on keeping the current system in good working order.
William_H
Well-Known Member
Solar is not cheap and can be very inconvenient to mount and protect from damage.
The simplest charge method for you would be a simple switch which connects the main battery to the standby battery when ever you have the engine running. You should have the negatives of the system connected to the spare battery with heavy wire so you only have to Jumper one lead. Of course a VSR would do the same thing automatically. You can make a simple VSR with just a few components if you are electronically minded. olewill
The simplest charge method for you would be a simple switch which connects the main battery to the standby battery when ever you have the engine running. You should have the negatives of the system connected to the spare battery with heavy wire so you only have to Jumper one lead. Of course a VSR would do the same thing automatically. You can make a simple VSR with just a few components if you are electronically minded. olewill
roly_voya
Well-Known Member
In a word No - the problem is that if a battery is left idle, even with the correct trickle charge rate to compensate for self discharge it will still deteriorate. Batteries like some work. I presume you are thinking of emergency starting and if that is the case look at one of the portable emergency start packs and take it off the boat when you are not on board. Either keep it at home or better keep it in the car and get an emergency light that runs off it, charge it off mains or lighter outlet. That way you are much more likely to look after it and it serves several functions.
willie4646
Well-Known Member
Why don't you connect the battery to the system through a 1,2,both switch and alternate the use of the batteries. Much cheaper than Solar power.
Willie
Willie
Moonshiners
Well-Known Member
I'm going to fit a second battery with a split charging relay from the "main battery" and a cheapo solar panel to keep the second trickle charged and topped up.
I used to build old cars and Kustoms. Rule 1. Car battery for Engine, lights etc... 2nd/leisure battery for the stereo and toys.
This meant that when you ran the battery down watching telly/dvd/stereo etc... you could always start your main and get going...
Split charging relays are around £15 and worth thinking about if your running a second batt.
I used to build old cars and Kustoms. Rule 1. Car battery for Engine, lights etc... 2nd/leisure battery for the stereo and toys.
This meant that when you ran the battery down watching telly/dvd/stereo etc... you could always start your main and get going...
Split charging relays are around £15 and worth thinking about if your running a second batt.
