Q: With all due respect, I think that one of your answers that I read was incorrect. The question was essentially: “can I connect multiple batteries in parallel, and use one battery charger to keep them charged over the winter?” You said no, use a separate charger for each battery. With a separate charger for each battery, you could control the amount of charge for each battery, but it would be much more expensive, and I do not see why it would be necessary. Electrically (and there are math equations for this), hooking several batteries in parallel looks the same to the charger, as if it was just one large battery. The only impact that I can see is if the current from the charger would be spread across the several batteries. The amount would depend upon the internal resistance of each battery. This internal resistance would vary depending upon things such as size, age and charge. I am interested in your thoughts.
— J.R., West Hartford, Conn.
A: Although several batteries can be connected to a single charger (or more precisely a maintainer), we do not recommend it. One faulty battery could create problems for the arrangement as you allude. Additionally, all the batteries in the chain must split the charging current. To be on the safe side, we suggest a discrete charger for each, or for a couple, but not seven batteries.
Q: I own a 2012 Hyundai Sonata. I recently went to get my first tire rotation at about 32,000 miles. I was told it was not possible due to severe cupping on the inside of both rear tires. A tire dealer told me that I should rotate the tires twice each year. If I rotate new tires regularly, won’t I just equalize the cupping between front and rear tires? This still seems like abnormal wear.
— B.D., Chicago
A: There is nothing stopping you from rotating your tires now. Of course, they may make some noise or vibration, but that should eventually go away. When you do a four-wheel rotation, each of the tires spends some time at each of the four corners. Hence, they wear evenly and equally. Twice-yearly rotations may be fine, but we prefer to go by mileage. Every 10,000-12,000 miles seems to work for us. When you buy new tires, have the suspension checked and aligned if necessary. Cupping is often due to worn shock absorbers.
Q: My 2004 Land Rover Discovery has a loud rattling noise coming from the engine area only when I’m driving it. It gets louder the faster I go, but when I come to a stop and the car is just idling the noise stops. I have been told that it’s the front differential. Just what is that and can I drive for long with the car sounding this way? Is this repair expensive and can my mechanic fix it or do I have to go to the dealer?
— R.B., Mount Prospect
A: A differential converts the rotation of the driveshaft (longitudinal) to the two axles driving the wheels (lateral or crosswise). While doing this, it also allows one wheel (the outermost) to turn faster than the inner wheel when turning. Quite a nice trick. Two-wheel-drive vehicles have one differential, either front or rear. Four-wheel-drive vehicles have one at each end. If it fails, you are going nowhere. A good tech can repair it or, in many circumstances, replace it as a unit and save some time if not money. Yes, it is expensive, but get it fixed soon.