Keeping two batteries happy (separated)
Please excuse this long post, but I thought a more comprehensive discussion of this topic might be of interest.
As is common with many RV's, I have two batteries in my RV, one for starting the vehicle and the other for house lighting, tv, etc. I started to have problems with my starting battery getting drawn down. After various diagnostic efforts I figure out that the diode based battery isolator had failed and no longer was keeping the batteries separated. This allowed the house battery to draw the starting battery down. I decided this might be a good time to look into the various battery separator options and have learned there are at least three with none clearly the best.
These are the options:
1. Solenoid. This is basically a switch that allows linking the batteries for charging both from either the alternator, generator or shore power (through a converter) and then disconnecting the batteries when parked. This seemed like a good choice since it can easily be wired to automatically link the batteries from the ignition or manually with a switch. Unfortunately, I have learned that many people have experienced early failure, but even more concerning was one comment I read that said if the two batteries are not roughly equal in charge, then when they are linked there is a massive movement of electrical power from the charged one to the other one (think hot wires, blown breakers, etc.)
2. Smart solenoid. This is a switch, but it has some intelligence that will block charge to the auxiliary battery until to main battery is at full charge and then I believe it meters the charge to the other battery. There are various options with these devices that will allow flow in both directions between the two batteries and allow use of both to assist with engine starting. One brand I have seen is Smart Power, but I'm sure there are others. These devices are more expensive than the basic solenoid and don't seem to have the same number of significant comments about failure, although there are some. They also seem to be more challenging to install.
3. Diode based isolator. These devices keep the two batteries separate through the use of diodes that allow a charge from the alternator to be delivered to each battery, but won't allow a charge to return from one battery to the other. These devices seem to usually function without much trouble, but mine did fail. Their downside seems to be the small voltage drop they cause in the charge from the alternator. They also don't allow the charging of the starting battery from the converter (either shore power or generator power).
I would appreciate comments, insights, clarification or recommendations.
As is common with many RV's, I have two batteries in my RV, one for starting the vehicle and the other for house lighting, tv, etc. I started to have problems with my starting battery getting drawn down. After various diagnostic efforts I figure out that the diode based battery isolator had failed and no longer was keeping the batteries separated. This allowed the house battery to draw the starting battery down. I decided this might be a good time to look into the various battery separator options and have learned there are at least three with none clearly the best.
These are the options:
1. Solenoid. This is basically a switch that allows linking the batteries for charging both from either the alternator, generator or shore power (through a converter) and then disconnecting the batteries when parked. This seemed like a good choice since it can easily be wired to automatically link the batteries from the ignition or manually with a switch. Unfortunately, I have learned that many people have experienced early failure, but even more concerning was one comment I read that said if the two batteries are not roughly equal in charge, then when they are linked there is a massive movement of electrical power from the charged one to the other one (think hot wires, blown breakers, etc.)
2. Smart solenoid. This is a switch, but it has some intelligence that will block charge to the auxiliary battery until to main battery is at full charge and then I believe it meters the charge to the other battery. There are various options with these devices that will allow flow in both directions between the two batteries and allow use of both to assist with engine starting. One brand I have seen is Smart Power, but I'm sure there are others. These devices are more expensive than the basic solenoid and don't seem to have the same number of significant comments about failure, although there are some. They also seem to be more challenging to install.
3. Diode based isolator. These devices keep the two batteries separate through the use of diodes that allow a charge from the alternator to be delivered to each battery, but won't allow a charge to return from one battery to the other. These devices seem to usually function without much trouble, but mine did fail. Their downside seems to be the small voltage drop they cause in the charge from the alternator. They also don't allow the charging of the starting battery from the converter (either shore power or generator power).
I would appreciate comments, insights, clarification or recommendations.
