Negative terminal corrosion (1 Viewer)

[nwcoast]

I put in a dual battery system in my 200 with an isolator. Had the same isolator in my 80 and it worked great. My starting battery is an optima yellowtop, accessory battery is a red top. Anyhow on my main starting battery I’m getting tons of corrosion on the negative terminal. I’ve cleaned it multiple times. Used the felt pads, dialectic grease, etc.. this last time I soaked all the connectors and bolts in baking soda water and is dissolved all corrosion away so everything looked brand new. Now a week or two later it looks as bad as ever.
Any thoughts?
Do I need to replace negative cable?
I read that negative terminal is a sign of undercharging. I do a lot of short trips in the cruiser, but have a hard time thinking this much corrosion could build up in a few weeks?

 

[TeCKis300]

I read that negative terminal is a sign of undercharging. I do a lot of short trips in the cruiser, but have a hard time thinking this much corrosion could build up in a few weeks?

Yes, unfortunately I do believe that to be the case.

I've alluded to this in a number of dual battery threads. Dual battery systems as they use to be setup in older vehicles are not viable when installed in modern cars.

Modern cars have highly regulated electrical systems. They use smart alternators that don't produce excess current, partly due to mpg efficiency and party to better maintain batteries for longer life.

What happens in a isolator setup like you have is that the instant the car is started, the isolator links the accessory battery to the electrical system. This linked parallel battery drives what the alternator detects, which is that of a fully charge battery. Causing the alternator to never adequately replenish the starter battery that's given up some charge to start the vehicle. Rinse repeat. And the starter battery is systemically undercharged.

I'd take the battery cables off and test the voltage of the battery with a voltmeter. Report back what you're finding.

 

[CharlieS]

I am probably asking a stupid question, but do products like the Redarc "smart" battery isolators avoid this?

 

[nwcoast]

Interesting, I’ll check on the battery voltage and see. It’s hard to remember, but I almost feel like the negative terminal had corrrosion before I added the dual battery setup. I was reading somewhere else that once the corrosion starts on negative terminal you have to replace the cable because it feeds the corrosion?

 

[LBridges]

Not saying I have a solution to your problem, just something I saw several times back when I worked as a mechanic.

Someone picked a battery up out of the tray using a terminal lead and that produced a break in the seal between the battery post and the inside components. Corrosion resulted. Could be caused by a hard twist to a tight terminal as well. Maybe these were cheap batteries, don't remember, but know it happened.

One other thought. Don't know if true or not, but another mechanic told me that stopping corrosion at the battery due to charging issues could result in the other end of the cables corroding. Like a ground at the engine block, something a lot harder to spot and correct.

 

[RobW0]

I am slowly learning the ins and outs of a dual battery system and the pros and cons of the different types of batteries. Not sure if everyone will agree with the following but I think it is for the most part right.

Short trips tend to lead to and undercharged battery. If the trips are short enough the battery does not get fully recharged after starting. Another problem you might have is that the Optima yellow top wants a higher voltage to get fully charged. I believe it likes a voltage over 14V. The alternator on the 200 typically puts out about 13.8V and when hot can go down to about 13.3V, because it is a temperature compensating alternator. What you might want to do is get a battery charger like the Optima 1200 Digital Battery Charger and periodically charge it to make sure it gets a full charge.

A Redarc BCDC dual battery DC-DC charger could be a benefit for you aux battery because it can give it the higher voltage that the Redtop battery would also want.

 

[RET2]

Battery cables are relatively cheap, I'd replace it.

 

[nwcoast]

Didn’t get time to take terminals off batteries, but did test em with terminal on. Main battery was positive 12.3 volts, secondary battery was negative 12.7 volts. I have circuit breakers to disconnect power to them and got same reading. Then I flipped the switch hooked to isolator so. Secondary battery can start car and both battery’s had a negative voltage reading.
What’s up with the negative voltage reading? Is that normal?

 

[RET2]

 

[GordJ]

Yes, unfortunately I do believe that to be the case.

I've alluded to this in a number of dual battery threads. Dual battery systems as they use to be setup in older vehicles are not viable when installed in modern cars.

Modern cars have highly regulated electrical systems. They use smart alternators that don't produce excess current, partly due to mpg efficiency and party to better maintain batteries for longer life.

What happens in a isolator setup like you have is that the instant the car is started, the isolator links the accessory battery to the electrical system. This linked parallel battery drives what the alternator detects, which is that of a fully charge battery. Causing the alternator to never adequately replenish the starter battery that's given up some charge to start the vehicle. Rinse repeat. And the starter battery is systemically undercharged.

I'd take the battery cables off and test the voltage of the battery with a voltmeter. Report back what you're finding.

I am unclear how undercharging can cause corrosion on the battery?

 

[RobW0]

I am unclear how undercharging can cause corrosion on the battery?

Undercharging the battery will lead to Sulfation, which is formation of lead sulfate on the battery plates. My guess is that this causes some type of migration to the neg term and the corrosion.

 

[GordJ]

Didn’t get time to take terminals off batteries, but did test em with terminal on. Main battery was positive 12.3 volts, secondary battery was negative 12.7 volts. I have circuit breakers to disconnect power to them and got same reading. Then I flipped the switch hooked to isolator so. Secondary battery can start car and both battery’s had a negative voltage reading.
What’s up with the negative voltage reading? Is that normal?

My guess is that you flipped the leads on the multi meter?

 

[TeCKis300]

I am unclear how undercharging can cause corrosion on the battery?

Undercharging the battery will lead to Sulfation, which is formation of lead sulfate on the battery plates. My guess is that this causes some type of migration to the neg term and the corrosion.

Spot on.

Yes, undercharging creates a chemistry with excess sulfuric acid. This is an external symptom of sulfation. Internally, the battery is also sulfating on the negative plates which is worse, because the battery is physically degrading on its way to premature failure.

The yellow top is supposedly a sealed AGM battery so the internal sulfation has likely already progressed to where it's now showing significant external symptoms. And/or this is exacerbated by a marginal seal at the negative terminal to @LBridges earlier point.

 

[TeCKis300]

Didn’t get time to take terminals off batteries, but did test em with terminal on. Main battery was positive 12.3 volts, secondary battery was negative 12.7 volts. I have circuit breakers to disconnect power to them and got same reading. Then I flipped the switch hooked to isolator so. Secondary battery can start car and both battery’s had a negative voltage reading.
What’s up with the negative voltage reading? Is that normal?

12.3V represents about 60-70% SOC (state of charge), which confirms your suspicion. A lead acid battery held at this level over the long term is going to fail prematurely. Vice the accessory battery at 12.7V which is full.

Curious as to the negative reading and I'm not understanding why. It shouldn't be that you hooked anything up backwards as things would short and breakers should trip. Stranger things have happened. I would definitely troubleshoot this further by taking readings between the battery (+) terminal and chassis. Or (-) terminal and chassis.

 

[TeCKis300]

Short trips tend to lead to and undercharged battery. If the trips are short enough the battery does not get fully recharged after starting. Another problem you might have is that the Optima yellow top wants a higher voltage to get fully charged. I believe it likes a voltage over 14V. The alternator on the 200 typically puts out about 13.8V and when hot can go down to about 13.3V, because it is a temperature compensating alternator. What you might want to do is get a battery charger like the Optima 1200 Digital Battery Charger and periodically charge it to make sure it gets a full charge.

Nope. This is a common fallacy carried on these boards. A properly designed battery system as the stock one is, will charge the starting battery every time even for the shortest of drives.

The alternator is designed for a standard flooded lead acid battery. It does not have the appropriate charge profile to support an AGM battery if that's what you're getting at with the higher voltage. AGMs particularly do not like high voltage along with high heat (i.e. underhood temps). Boosting the voltage is not going to solve these types of issues. Having to hookup an out-board charger regularly is a sign that the battery system is not designed correctly. Perhaps it's just me but that would also be a royal PITA and is not my idea of an "upgrade".

A Redarc BCDC dual battery DC-DC charger could be a benefit for you aux battery because it can give it the higher voltage that the Redtop battery would also want.

Now we're getting somewhere. Fact is that a single smart charger cannot charge 2 different batteries at two different SOCs simultaneously. Unless it's trickle charging an old school single stage charger. Smart alternators are like this too and it doesn't know what charging stage to use when two different batteries are hooked up in parallel. A secondary accessory battery requires a DC-DC charger to tender it. Benefit is that the modern ones also have settings to accommodate many chemistries.

One could remove all the complexity and do this - KISS Dual Battery Upgrade

 

[Fisher23]

Test that battery, that can be a sign the battery is going bad. They usually have a 3 year plan on them.