Charging setup for multiple batteries.

Hi Guys,
I'm wantin' to setup a charger, could be solar powered, that will charge multiple bikes at the same time. There is no conventional power available so I've I'm planning to use a Battery Tender (brand) solar array to charge a deep cycle battery which will do lights. I'm pretty sure I cant just hook up other batteries in parallel but I just don't know what may be needed to keep the batteries all happy.
Any suggestions will be greatly appreciated.
Bill

It may depend on which model you get. The 15 watt one seems to have a microporcessor to analyze battery condition etc. Hooking up multiple batteries to that would probably be problematic as you will be trying to fool the microporcessor into charging all the time. That is because if one battery is fully charged, you will still want to charge the other ones.

For your situation, I would think a "dumb" solar array with a simple regulator would be better. Then you could just connect each battery through a diode (and maybe a resistor), and make a very-slow trickle and float charger. It will not quickly re-charge a dead battery, but it will be able to maintain several already-charged batteries.

If you want the "smart" controller for each battery and the option to charge quicker, then I think you would be stuck trying to find a one charger per battery solution... pretty expensive. I see the 5 watt solar battery tender is close to $100, and I think that is just for one battery.

The spec is somewhat ambiguous. It says "Output: 12VDC, 0.270 Amp DC, 5 Watt Max" but obviously 12v would be too low to charge a battery. I think it's just to indicate its for 12v batteries. So it doesn't really indicate what the actual voltage is. If the actual output voltage is closer to 15v, then you could just use 1 isolation diode per battery (So one bad battery won't drag down the rest). Then you may want to add a small resistor (like 1 ohm) to each in order to reduce the amperage to each battery so that one won't take all the power away from the others.

As you can see, when you only have one source, it's hard to protect against one bad battery harming the others.

Hi Lou,
When you say: ' a "dumb" solar array with a simple regulator would be better.' I'm not sure what the regulator would do.
I think I understand your "isolation diode and the one ohm resistor" to isolate the batteries.
I have a local solar array manufacturer who sells defective but repaired arrays out the back door. I'll ask them if they also have a regulator they would recommend.
Thank you
Bill

The regulator, in that case, is just a limiter so the voltage does not go too high.

I'll draw a fan out diagram just so we're on the same page.

Yes, if you can get a cheap solar array, that may be the way to go, especially if they are more powerful.
The thing is, making this sort of thing needs some thorough testing. You don't want to go up in smoke.

You want the array output low enough that it is easy to regulate, but then you want it to be powerful enough to work on cloudy days.

I haven't worked with solar arrays, but I get the sense that any clouds really kill off the power output.

There is a chance that you might even be able to use a Kz voltage regulator. They are designed for AC input, but will also take DC input. As long as your array is not too powerful, the Kz regulator should be able to handle it. If the array is too powerful, you can reduce the output with a big resistor or diode.

The diagram below does not show the regulator or array, just a generic, weak power source putting out about 14 to 15v.

The diodes give the isolation. The resistors balance the load between the batteries. They are in the 1 ohm range, and 1 to 5 watts, depending on how powerful the power source is.

Thanks Lou,
I've got a whole bench of motorcycle batteries I can test with. I'll start assembling the other parts and post about it soon.
Bill

Another option.......

products.batterytender.com/Chargers/4-Ba...tern-Hemisphere.html

Ed

Hi Ed,
The bikes I need to charge are stored in a container from November until March. I'd like to rotate around some charging leads through the winter so that come next training season I don't have to replace too many batteries. My problem is that there is no conventional power available hence my interest in solar power. I've already set up a couple of ten watt solar arrays at our Redmond, Oregon location however these are limited to one bike at a time. Ideally I could hook up to more than one or two bikes at a time and not damage any batteries.
Regards
Bill

It might be worthwhile to contact the folks at Deltran to ask them if they have a solar battery charger can be used to keep multiple batteries charged. They make solar powered chargers (see link below), but I don't know if they have one that can attach to multiple batteries. If nothing else their advice might prove helpful in setting up your own chargers. Ed

products.batterytender.com/Solar/

I have to pull the batteries in my bikes for the season (normally I don't, but this year is shaping up like last year, temperature-wise, so I better pull them). I'm going to top them off and I can make some measurements while doing so.

How many batteries were you thinking of connecting?
And about what size are they? or what displacement bikes are they?
This is to get a sense of how comparable the data will be from my Kz550 batteries.

These bikes are all 250 CC or less. Suzuki TU 250X, Suzuki GZ 250, Kawasaki BN 125 Eliminator, Suzuki Van Van, Yamaha TrailWay 200, Suzuki DR 200, I believe they are all in the 7 to 10 amp hour range. I'm thinking that charging four at a time would be ideal.
Thanks
Bill

I think you will want to look for an array that can provide around .040 amp at 15v to 16v for each battery you want connected, and that is when the sun is about at its brightest.

So, for 4 batteries you will want around .160 amp at around 15 to 16v on a sunny day.
And for 6 batteries you will want around .240 amp at around 15 to 16v on a sunny day.

If most days are sunny, you might get away with .030 amp per battery, if most days are cloudy, you can probably go .050 amp per battery. The final output level will be set by adjusting the resistance value after confirming the array's actual output.

I have a battery connected right now at .020 amp, so I may revise the numbers tomorrow depending on what I find.