A quick question about battery chargers

I’ve installed a 4.8W trickle solar charger on the roof of my garage so I can keep my bikes’ batteries in tip-top shape. After installing it on Sunday morning I checked the voltage and it was showing 21V and it was in the shade. Am I OK to connect it to my battery?

It all depends on the rest of the circuitry :smiley:

Being solar powered I would expect the resistance
to be quite high, and it will not have much oomph,
so there will probably by a big drop in voltage when
you connect it to your battery. Put an ammeter in line
and check it’s only delivering a fraction of 1 A when
connected and also check the voltage when it’s connected,
it should only read 12 to 14 v.

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This might help http://store.sundancesolar.com/tricklechargingfaq.html

I you can buy a controller box, but I think you’ll be alright http://www.ebay.co.uk/itm/120983020694?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Cheers guys. I’ll connect it on Saturday and take some measurements - what’s the worst that can happen, eh?

It is unlikely to do anything very quickly. If it overcharges it will make the battery fizz, heat up and eventually boil off the electrolyte, dry it out and warp the plates. But that will take more than the few seconds it will take to connect it up, check it isn’t fizzing vigorously, check it isn’t warming up very quickly and take the voltage across the terminals. If when charging the voltage across the battery terminals is between 12.6 and 14.5v then all will be well.

try this:

OR you could just tape over some of the solar cells until it puts out 13-14v?