Solar Trickle Charging for ATV Batteries

[mjp24coho]

After buying too many batteries for my ATV's over the years, I'm thinking of using solar to trickle charge my ATV batteries when not in use. I store my 3 ATVs in our garage at our offsite cabin, where temperatures gut up into the 90's in the summer, and in the teens in the winter. I only use the quads once a month, and too frequently they've been getting drained down due to the limited use and temperature swings.

I'd like to set something up where I could connect each quad to a solar trickle charger when I leave, so the it maintains the batteries while I'm away for each month. Since I'll need three of them (one for each quad), I'd like to keep it as simple and cheap as possible. The ATV batteries are fairly large (for Polaris 500 EFIs) One option appears to be a 1W panel that I can wire directly to the battery w/out a charge controller, and another would be a 5W panel that may/may not need a charge controller. Both are for sale by our sponsor. What I'd like some input on, is whether or not the 1W would be sufficient, or if not, whether the 5W would need a charge controller. My other concern is how safe these are, since they'll be connected and unsupervised at our remote cabin while I'm away for ~1 month at a time. Overcharging and any risk of sparks, fire, etc. is not anything I want to deal with.

Any advice/thoughts any of you could offer would be greatly appreciated. Thanks!

[mike95490]

Depends on the size (amp hour capacity) of the ATV batterys, and if they are flooded or AGM type.

If flooded, I'd just stick a 5W panel on , and watch the water level, if it does not expose the plates after a month, it's likely OK. If it boils water to the plates in a month, then 5W is too big. Amount of sun is a factor. 5W for 3 hours is different than 5W 7 hours. Maybe instead of a charge controller, park on the east side, and limit the charging hours.

[niel]

waiting to see if the plates get exposed is not a good idea as you don't want to damage the batteries, but just trickle them and keep them maintained. the current is low, but the vmp is high enough on the pvs that it could creep up in voltage with a fully charged battery of low capacity. we would need more info on the battery to comment better on possible regulation needs.
anything electrical can pose a slight risk, but there's usually no problems with low voltage low current sources as far as hazards go. fusing helps too and should be utilized as the batteries can pump out huge current levels when shorted. the panels may need mounted extraneously from the atvs and being sheltered from the elements aren't exposed to the sun so i'm thinking 1 pv of maybe 5w and 3 separate leads to each battery complete with the diodes and fusing from the output of the pv. the pv's output can be led in by just 2 wires and the diodes and fusing located in doors and from there it can separately be distributed to each battery. the diodes would isolate each battery from each other so a bad battery won't drag down the other 2. the voltage drop will be about a 1/2 volt or so making the voltage output from the pv slightly lower, but for maintaining batteries i don't feel that will pose a problem and it depends also on the batteries you have as to how small or large they may be if regulation may be needed with odds being you won't need any regulation. the hard part would be configuring the diodes and fusing to be mounted in a box. it need not be an expensive utility grade or nec approved type box for this and most parts could be bought at a radio shack or similar store. you can make it as neat and elaborate as you like, but it must be functional.
another option may be to install switches for the outputs to each battery in case 1 or 2 of the batteries are disconnected from this trickle charger for you don't want those unused leads shorting even though you would have fuses on them or you may just want to not include a battery even though it is connected up.

[blackswan555]

A month seems a little short to be getting that much discharge, Is there anything on the quads drawing current ? eg Immobilizer / alarm / clock ? may be worth checking with a meter ? If so disconnecting the bat or adding a bat switch may help ?

Have a good one
Tim

[mike95490]

waiting to see if the plates get exposed is not a good idea as you don't want to damage the batteries, but just trickle them and keep them maintained. the current is low, but the vmp is high enough on the pvs that it could creep up in voltage with a fully charged battery of low capacity.

At this point, I'm guessing a $80 battery is less expensive than a $120 charge controller for it.

What's the damage to a flooded battery, if it has a gentle overcharge for a couple hours a day ? A 5W panel would find a tough job to really heat up any kind of a starter battery. Can't acid levels drop to the top of the plates, and as long as the separators stay wet, and you refill before use, still be OK ? Boiling off water below the plates, drying and cracking, are all bad, but unlikely with a 5W panel, in 1 month.

I just thought this would be a simple, fairly benign experiment to do on someone else's battery :)

[Dave Sparks]

The problem I believe is the use of an AGM battery with an on-board charger that is allowing the battery to hit 14.7 or higher. The easy fix is a high power silicon diode in series with the battery. My Honda use to eat AGM's before I did this and my last battery is going on 6 years.

Imagine what happens to AGM's when lightning takes out the charge controller and $15K of batteries get over volted?

[niel]

mike,
it was your words and letting batteries go bad repeatably isn't justification for not using some regulation if that's the case. regulation does not necessarily cost that much and i think you know that as he would not necessarily need 3 separate controllers and there are linear regulators out there that are cheap too. also, what if he is using agms in there?

dave,
yes, a diode may fix that if that's the case. it also depends if such a charger is regulated or not too as some are for the cheap fla types and voltages can be seen up around 17 or 18v. diodes will reduce the voltage by around a half volt and make things better, but may still not be right for the battery be it agm or not. one will know if the pv is too much and in need of regulation if the voltages seen on the battery rise beyond about 14.5v for agm and 15v for fla types. those are rounded figures and are signs the battery could be overcharging when exceeded. each battery manufacturer should state the battery max and if not those voltages i gave should be good ballpark figures. they really don't need to be that high in voltage as read off of the battery either for if i saw the arrangement of a pv and diode settle in at 14.8v on a standard fla type battery i would place another diode in line as a trickle charge does not need to have voltages that high and are usually in the 13-14v range.
btw, the lightning strike and overcharge can happen to any cc and battery regardless of type, but usually the regulation circuits open up making overcharge unlikely.

mjp,
as i said, more info can yield better advice or comments, but if you elect to not reply again, do know that the diodes need to be rated for the current that is to pass. if using the 3 battery idea and 5w pv on only 1 or 2 batteries, be aware that there will be a higher current to the batteries and a better chance of an overcharge with voltages going too far. there's allot to be said for regulation be it a controller or something made from linear ics as it does make it more maintenance free and reliable.

[mjp24coho]

Thanks for the responses, all. A little more info - the batteries are all 12V AGMs. One is 18 Ah (20HL-BS), one is 28 Ah (XTA-30L), and the smallest is is 12 Ah (14-BS).

[RCinFLA]

ATV is probably alot like a riding lawn mower for battery usage.

In winter time the grass doesn't grow that quick and mover sits 5-7 weeks in between. After buying a new battery about every 18 months I bought a small Battery Tender. It is a three state charger and floats the battery at 13.2 vdc.

Now its been four years and battery still going strong.

[niel]

if you still do the solar route then i recommend either a controller or some other regulation circuitry as agms are sensitive to overvoltages. separate systems may also still be not needed if one has the isolation diodes, but i'm not to sure what will happen with the differing ah sizes of batteries. btw, that rules out anything that does not isolate or you will need totally separate systems for each as mixing batteries of different sizes is not recommended ever even if they are separated by a long length of wire in between.