Solar Trickle Charger Controller

[ko4nrbs]

Do I need a charge controller for a 1.5 watt Solar Trickle charger for 12 volt battery?

Bill

[gmanInPA]

Do I need a charge controller for a 1.5 watt Solar Trickle charger for 12 volt battery?

Bill

I doubt it. 1.5w / 12v = .125 amps of current which is very small and would not really ever pose an over-charge risk to your battery - not that I can see anyway. If others would disagree, i'd be interested to know why.

[Sunking]

What size 12 volt battery?

[ko4nrbs]

What size 12 volt battery?

This one:

http://www.walmart.ca/en/ip/everstart-battery-maxx/6000195362492

Bill

[Sunking]

Well you do know that is not a Deep Cycle battery right? It is a SLI (Starting Lighting Ignition) aka Cranking Battery? The dead giveaway is the Automotive Post and 900 CCA rating. If you press it into cycle service will not last long as it is not made to be cycled.

Anyway you can use the panel without a Charge Controller providing you use a Blocking Diode. Without a Blocking Diode it will only Discharge the Battery and kill it. Having said that a 1.5 watt Panel will not really even keep a battery that sized charged up assuming the battery was fully charged to begin with. It is just not large enough. About the best you can hope for is to slow down the self discharge of the battery.

FWIW a RC = 185 minutes is roughly equal a 75 to 100 AH battery. Pb self discharge rate is roughly 15% per month or 15 Amp Hours. A 1.5 watt panel made for a 12 volt battery has a current of roughly .08 amps and with 4 Sun Hours generates .32 Amp Hour per day. The battery will self discharge roughly .5 AH per day. That is roughly a net loss of .1 AH per day.

[ko4nrbs]

Well you do know that is not a Deep Cycle battery right? It is a SLI (Starting Lighting Ignition) aka Cranking Battery? The dead giveaway is the Automotive Post and 900 CCA rating. If you press it into cycle service will not last long as it is not made to be cycled.

Anyway you can use the panel without a Charge Controller providing you use a Blocking Diode. Without a Blocking Diode it will only Discharge the Battery and kill it. Having said that a 1.5 watt Panel will not really even keep a battery that sized charged up assuming the battery was fully charged to begin with. It is just not large enough. About the best you can hope for is to slow down the self discharge of the battery.

FWIW a RC = 185 minutes is roughly equal a 75 to 100 AH battery. Pb self discharge rate is roughly 15% per month or 15 Amp Hours. A 1.5 watt panel made for a 12 volt battery has a current of roughly .08 amps and with 4 Sun Hours generates .32 Amp Hour per day. The battery will self discharge roughly .5 AH per day. That is roughly a net loss of .1 AH per day.

It's the starting battery for my RV. I'll start with it fully charged and just use this as a Battery tender.
Bill

[Sunking]

OK but 1.5 watts is not going to do what you think. Just not enough power to over come self discharge rate of the battery. If the RV has ghost and/or parasitic loads like most vehicles have today, is not going to do much of anything. A Trickle Charger is intended to keep a disconnected fully charged battery charged and over come self discharge rate of the battery. For Flooded Lead Acid on solar the charge rate is typically C/33 to C/50. or C/100 using commercial AC. So on a 75 to 100 AH battery like yours would be 1.2 to 2 amps for solar. Your 1.5 watt panel at best will only generate 0.1 amps for a couple of hours a day. That is less than 1/10 of what is required. All it will do is barely slow down discharge. Leave it in the RV connected and it does virtually nothing. You need something in the 15 to 25 watt range.

[ko4nrbs]

OK but 1.5 watts is not going to do what you think. Just not enough power to over come self discharge rate of the battery. If the RV has ghost and/or parasitic loads like most vehicles have today, is not going to do much of anything. A Trickle Charger is intended to keep a disconnected fully charged battery charged and over come self discharge rate of the battery. For Flooded Lead Acid on solar the charge rate is typically C/33 to C/50. or C/100 using commercial AC. So on a 75 to 100 AH battery like yours would be 1.2 to 2 amps for solar. Your 1.5 watt panel at best will only generate 0.1 amps for a couple of hours a day. That is less than 1/10 of what is required. All it will do is barely slow down discharge. Leave it in the RV connected and it does virtually nothing. You need something in the 15 to 25 watt range.

Thank you for the detailed explanation!!

I'll try and find one in the 15 to 25 watt range.

Bill