I was at my local Rural King today buying a car battery and came across a solar battery maintainer. It is a small 2.4 watt (.2 amp) trickle charger designed specifically for keeping a battery topped off.
I picked one up, since they were only $30, to give it a try. After reading the manual, I have a couple questions.
The manual says that it is only to be used as a maintainer and that charging a partially discharged battery with it may cause the battery to lose capacity. Anyone here know why or how that would happen? I was under the impression that a trickle charge was the best way to prevent a battery from losing capacity, not the other way around.
Also, it mentions that it must be unhooked prior to starting or running a vehicle because electrical surges from the alternator may damage it. Would I be able to get around this by using a relay that breaks the circuit whenever the ignition is on or by using a diode to prevent current from backfeeding into the maintainer? Would this be a problem with a system that doesn't have an alternator? I was thinking about using this on my upcoming HAM EMCOMM box build which obviously will not have one.
Originally Posted By Altair:
The manual says that it is only to be used as a maintainer and that charging a partially discharged battery with it may cause the battery to lose capacity. Anyone here know why or how that would happen?
Recharging a lead-acid battery requires a considerably higher voltage than simply maintaining it:
Charge voltage: approx. 14.5 V
Maintenance voltage: approx. 13.5 V
If the solar maintainer only produces 13.5 volts under load, it will not bring the battery up to anywhere near a full charge - and chronically undercharging a lead-acid battery can result in a permanent loss of capacity.
Originally Posted By Skibane:
Originally Posted By Altair:
The manual says that it is only to be used as a maintainer and that charging a partially discharged battery with it may cause the battery to lose capacity. Anyone here know why or how that would happen?
Recharging a lead-acid battery requires a considerably higher voltage than simply maintaining it:
Charge voltage: approx. 14.5 V
Maintenance voltage: approx. 13.5 V
If the solar maintainer only produces 13.5 volts under load, it will not bring the battery up to anywhere near a full charge - and chronically undercharging a lead-acid battery can result in a permanent loss of capacity.
The specs show "Optimum Working Voltage" at 17.5 volts. Would this vary based on sun conditions or would voltage remain constant while amperage would vary?
ETA: Also, am I on the right track with wiring with a diode or relay?
Originally Posted By Altair:
Originally Posted By Skibane:
Originally Posted By Altair:
The manual says that it is only to be used as a maintainer and that charging a partially discharged battery with it may cause the battery to lose capacity. Anyone here know why or how that would happen?
Recharging a lead-acid battery requires a considerably higher voltage than simply maintaining it:
Charge voltage: approx. 14.5 V
Maintenance voltage: approx. 13.5 V
If the solar maintainer only produces 13.5 volts under load, it will not bring the battery up to anywhere near a full charge - and chronically undercharging a lead-acid battery can result in a permanent loss of capacity.
The specs show "Optimum Working Voltage" at 17.5 volts. Would this vary based on sun conditions or would voltage remain constant while amperage would vary?
ETA: Also, am I on the right track with wiring with a diode or relay?
It's too small to produce anywhere near 17.5 volts with a partially-discharged battery - which is why they recommend only using it to maintain fully-charged batteries.
