Charging setup for multiple batteries.

I have several bikes hooked up to one battery conditioner. Simple flick of the switch to alternate which bike is on charge. Maybe something like this with a auto timer could work?

loudhvx wrote: ...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.

About fooling the microprocessor, If I was charging four batteries and one or two of them reached full charge wouldn't the micro processor still sense the state of the two weaker batteries and continue charging until all four were topped up?
Thanks
Bill

How come those companies who make those battery booster devices don't make a device that takes it's power from a 12 volt lead acid battery and steps it up to 15 volts to trickle charge another 12 volt battery? I realize that the source battery would have to be much larger than the battery to be charged. All I want is to take a few 7 to 10 amp hour batteries that are at 80% and top them up from a large 12 volt deep cycle battery. Once the bikes in storage are topped up I'd bring the big battery home and charge it by conventional power, returning the next day to top up the next group of bikes.
Seems simple to me.
Bill

KZQ wrote:

loudhvx wrote: ...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.

About fooling the microprocessor, If I was charging four batteries and one or two of them reached full charge wouldn't the micro processor still sense the state of the two weaker batteries and continue charging until all four were topped up?
Thanks
Bill

If all of the batteries are simply connected in parallel (bad idea unto itself), it can't distinguish between batteries so it's an all or nothing scenario. Depending on the algorithm used to control the charging, it may shutoff when one or more is charged but the others aren't. How it determines battery condition is unknown, it could be based on voltage or current but more likely some combination of both. So I am recommending against this setup.

The presumption is that you have isolated the batteries from each other so one bad one can't kill the other ones, and you've devised a way to allow the batteries to float albeit at a very safe level, lower than typical float chargers which are meant to be turned off after a few hours or days. That's the diode and resistor setup I posted.

Next is to fool the charger to stay on all the time so that you have a power source. But I recommend using a dumb charger then you will have your power source all the time without having to fool anything.

KZQ wrote: How come those companies who make those battery booster devices don't make a device that takes it's power from a 12 volt lead acid battery and steps it up to 15 volts to trickle charge another 12 volt battery? I realize that the source battery would have to be much larger than the battery to be charged. All I want is to take a few 7 to 10 amp hour batteries that are at 80% and top them up from a large 12 volt deep cycle battery. Once the bikes in storage are topped up I'd bring the big battery home and charge it by conventional power, returning the next day to top up the next group of bikes.
Seems simple to me.
Bill

They make 7-cell batteries for total-loss racing. They have an ambient voltage just over 14v. I've never looked into it, but they probably aren't cheap since they are for racing.

Another option is just to use two 12v, deep-cycle batteries in series and a simple (linear) regulator. This will be very inefficient because the regulator will be dropping 24v down to 14 or so. The larger the drop, the more energy is wasted as heat when using a classic linear regulator.

But nowadays, you can get a "switching power supply" which reduces the output by rapidly turning the input on and off at a high frequency. This is much more efficient, but is something you would buy rather than build.

Here's one I found on Amazon on a very brief search. You can use a 12v battery for this one to get 15v.
Switching regulators sometimes have special requirements. For instance this one has a minimum load of 30mA. That means it will work for several batteries, but to use only 1 or 2 batteries as loads, you may need a load resistor.
www.amazon.com/DROK-Converter-Non-isolat...id=1576090920&sr=8-4

I don't see a problem charging multiple batteries in parallel on one charger. When in parallel the batteries will self balance and settle at one voltage and will essentially be one large battery.

The initial connection can be troublesome as a large voltage difference between two batteries will cause a large current draw from the more charged battery to the less charged one.

It's fine for ideal conditions, but say one develops a short in a cell. Now all batteries will drain through that short and all will be ruined.

That's a good thing to consider haha.

We use These at work. Reliable for the most part and not too bad on price if you wanted a few

I've wired up a harness as per Lou's diagram above, which is exactly what a local electronics guy suggested. I'll get the collector mounted before this weekend, it's supposed to be sunny and see what it'll do. I figure I'll drain down a few batteries with a 12 bulb and hook 'em up.
Bill

If you want to actually re-charge batteries (as opposed to just topping off losses from sitting), then the array will have to be powerful enough that it will require a limiter for when the batteries are full, and then you will also need some sort of smart controller to shut off the charging otherwise you might boil off the batteries in the long term.

Another factor is indeed temperature. It works against you. On a warm day (70's), you will want maybe half of a volt lower than on a cold day (30's). So in the summer, when you want less voltage, the increased sun will give you more voltage.

If the array is weak enough you can get away without the smart device, temperature comp, and maybe even the limiter, though it wouldn't hurt to have a limiter anyway in case of a really sunny day, but then you have to be willing to allow for days or weeks to re-charge a low battery.

There is a lot of juggling of resistor values and limiter voltages you will have to do until you know the actual output of the array on the sunniest day... which of course will be much higher in the summer if you intend to store them that long.

Since we are basically at the winter solstice, an array output reading will give you basically the low point. There is probably a chart somewhere on what to expect the array to give you at noon near the summer solstice based on what you measure today.

Or make life easy for yourself and fully charge them individually and then disconnect them from the loom on the bike. Leaving them isolated from the charger and the the possible drain from the loom.

I would tend to agree with warren on removing them, charging them, clean them, then store them on a wooden shelf in a heated, ventilated area. 6 months is a long time to try to maintain a fully charged battery. I would monitor the voltages, and connect a battery tender if / when the voltages drop.

A battery at a constant charge will get cooked dry over a extended time-frame. As the loud one pointed out, a tender should plateau at the desired voltage, then shut off until it reaches a predetermined low, then return voltage to the proper levels, repeat as necessary.