27DC two battery hookup

[nothermark]

Looking at what you posted I suspect the batteries were originally a pair of 6 V batteries. Someone went to Costco and bought new batteries but did not understand what they were doing. If they hooked up the two 12 VDC in series and tried to use them that way they probably did serious damage to the 12 VDC parts of the coach. That could include all the appliances. One way to hide that would be to remove all the connections and plead ignorance then let the buyer eat the cost of replacements. After all, they are all old so what can one expect? That leaves you with two problems.

One is to determine what the two batteries really are. I'd count the cell caps for that. Each cell needs a filler hole and puts out ~2.2 VDC. If there are six caps then it's a 12 VDC battery. If there are two caps that cover 3 cells each it's the same deal. If it's 3 caps they are 6 VDC batteries.

Before I connected up the batteries I would charge them with a separate charger. If they are really 12 VDC batteries they may be toast from sitting around at too low a charge state. You can try to bring them up with a 12 VDC charger with a high current load in series with the battery to protect the charger. I usually use an old headlight. As the cell voltage comes up the light gets dimmer and I check the battery voltage. Once it comes up over 10 VDC I remove the series load and top off the battery. At that point the cells are low but they are all working with the correct chemistry. Without the load you will probably mess up the charger by drawing too much current.

Once you get the batteries charged then try a 12 VDC setup with one 12 V battery or two 6 V batteries. See if everything works starting with the built in charging system that should be charging at something over 13 VDC. Then check all the appliances and lights for operation. Most RV appliances use 12 VDC for control voltage so they could all be damaged if the previous owner connected them to 24 VDC. It could be blown fuses but solid state electronics often blow faster than the fuse.

Once you get that far come back with data and questions if you still have them.

[kevingnet]

Originally Posted by nothermark

Looking at what you posted I suspect the batteries were originally a pair of 6 V batteries. Someone went to Costco and bought new batteries but did not understand what they were doing. If they hooked up the two 12 VDC in series and tried to use them that way they probably did serious damage to the 12 VDC parts of the coach. That could include all the appliances. One way to hide that would be to remove all the connections and plead ignorance then let the buyer eat the cost of replacements. After all, they are all old so what can one expect? That leaves you with two problems.

One is to determine what the two batteries really are. I'd count the cell caps for that. Each cell needs a filler hole and puts out ~2.2 VDC. If there are six caps then it's a 12 VDC battery. If there are two caps that cover 3 cells each it's the same deal. If it's 3 caps they are 6 VDC batteries.

Before I connected up the batteries I would charge them with a separate charger. If they are really 12 VDC batteries they may be toast from sitting around at too low a charge state. You can try to bring them up with a 12 VDC charger with a high current load in series with the battery to protect the charger. I usually use an old headlight. As the cell voltage comes up the light gets dimmer and I check the battery voltage. Once it comes up over 10 VDC I remove the series load and top off the battery. At that point the cells are low but they are all working with the correct chemistry. Without the load you will probably mess up the charger by drawing too much current.

Once you get the batteries charged then try a 12 VDC setup with one 12 V battery or two 6 V batteries. See if everything works starting with the built in charging system that should be charging at something over 13 VDC. Then check all the appliances and lights for operation. Most RV appliances use 12 VDC for control voltage so they could all be damaged if the previous owner connected them to 24 VDC. It could be blown fuses but solid state electronics often blow faster than the fuse.

Once you get that far come back with data and questions if you still have them.

Thanks so much. I had suspected that possibility. The current owners seem pretty trust worthy, and we even had arranged for a full check up before the sale and they would discount for any broken items. We'll see how that goes this weekend. I post the results.

[Big Oil Guy]

Group 27 batteries are 12v. Of concern would be the refrigerator, heater, and hot water heater. Your lights would be protected with fuses. Pretty much everything else runs off 120v, as I'm guessing that an 1986 Cross Country doesn't have an inverter. If it does, that would be in play also. You can check your converter with your voltmeter once the batteries are wired up correctly. If you get an honest 12v to the system and everything works, you are golden.... (with any luck).

[twinboat]

Originally Posted by Big Oil Guy

Group 27 batteries are 12v. Of concern would be the refrigerator, heater, and hot water heater. Your lights would be protected with fuses. Pretty much everything else runs off 120v, as I'm guessing that an 1986 Cross Country doesn't have an inverter. If it does, that would be in play also. You can check your converter with your voltmeter once the batteries are wired up correctly. If you get an honest 12v to the system and everything works, you are golden.... (with any luck).

Humm, I think the bulbs would burn out before the fuses fail.

At least they did when I stuck 12 volt bulbs into a 24 volt socket.

[Big Oil Guy]

Originally Posted by twinboat

Humm, I think the bulbs would burn out before the fuses fail.

At least they did when I stuck 12 volt bulbs into a 24 volt socket.

Perhaps that would be the case, then you'd just have to replace some light bulbs. Can't imagine that too many lights would be on at the same time. I think the lights that might have been on would be the least of my worries.

[nothermark]

Originally Posted by twinboat

Humm, I think the bulbs would burn out before the fuses fail.

At least they did when I stuck 12 volt bulbs into a 24 volt socket.

Fuses beat bulbs. Transistors often beat fuses.

[twinboat]

Originally Posted by nothermark

Fuses beat bulbs. Transistors often beat fuses.

Double the volts, half the amps. Bulb gets real bright until it fails.