[RHille]

Over the past six years, I have replaced my ’94 Cab’s battery four times…rather tiresome. After the second quality battery died, began thinking that maybe I’ve got some other issues going on. So, after installing a new battery, I did all the stuff I saw on the posts: checked for drains (nothing); got a top quality trickle charger (a BatteryMinder with a de-sulfanate cycle); checked cables and cleaned all connections; even installed Dan’s (a.k.a successor to IceShark) front mounted ground cable. All fixed, right? Wrong.



A month ago, about half way through a 200 mile trip, going through small towns (lower speeds) I started to see an occasional voltage drop from the usual 13 or so down toward 12.5 or so. Doesn’t sound like much, but when you’re used to seeing no movement, 0.5 volts is a lot. While I got home OK, figured I better load test the battery next morning after an all night trickle charge. Really don’t know why I bothered…I could have just checked my last battery receipt…sure enough, 1 year, 6 months, just like clockwork.



This time, having been smart enough to keep my Interstate 3-year free replacement warrantee receipt, I got a new, free battery with no hassle, other than me having to find an in stock store, install myself in their parking lot (in the rain), and later reset my CR-1 radio code and pre-set stations. Enough is enough!! Time to surf the net…THE TRUTH IS OUT THERE!



After learning about battery construction, proper charging voltages, voltage regulators, and alternator testing, I started researching BOSCH and saw several commentaries about them having been very conservative with their voltage regulator set point of about 13.5V (I’ve verified several times that mine generates about 13.4V). The advantage of 13.5V being very unlikely battery overcharge (boiling, water loss, then death) with any type of battery construction; the disadvantage being possible incomplete battery charging, especially if running lights, radio, radiator cooling and/or cabin ventilation fans. Very troubling, especially seeing much information to indicate that with most batteries, anything up to 15V should be considered quite safe.



Having now decided to install a higher output regulator, but still being a bit uncomfortable with the best voltage set point, I Googled “adjustable voltage regulator.” BINGO: www.davebarton.com. It explains EVERYTHING! Vintage Volvos use Bosch, and have the same problem I’m having, especially in hot weather with the regulator close to the engine (semiconductors don’t like heat). How could I go wrong with a fully adjustable regulator that allows the semiconductor to be mounted remotely in a cooler location??!



So, $55 via PayPal and three days later, I got my kit. Opted not to remove the alternator, but install in place (still not easy, have to do by feel only). Decided not to disconnect battery and only had one very minor "arc and spark." Besides difficulty in getting to screws (a 90 deg. ratcheting screw driver was VERY helpful), ran into one other problem. The sending unit supplied (the brush module) had to be trimmed to fit my OEM alternator.



Encountering difficulty getting the new unit installed (even after figuring out how to retract the brushes with a long, skinny bolt...wow, is that helpful), I compared my OEM regulator to the one supplied. The top profile on the plastic mount is appreciably taller than the OEM. Figured out that the top right side (looking at unit from it's outward side) was lodging against the positive out terminal; that is, with the outboard screw inserted, the inboard mounting hole would not move up to the screw hole in the alternator. So, I did some trim work...needed to remove right top plastic down and just into the grounding strap....maybe 3/16 inch of plastic removal at widest point....left side and center top are OK fit. [This will make sense if you do it!!]



Once the brush assembly was mounted in the alternator, the length of the supplied wire cable allowed me to mount the regulator toward the front of the engine compartment, far away from major heat, and in an area allowing easy voltage adjustment. Now for the amazing part....damn thing worked right out of the blocks!!



My old regulator generated 13.4 volts and not too steady at that. This thing gave me a rock solid 13.8 without touching it. But then you've got to play with it, right? With a running but still cold engine, I started advancing the potentiometer with my "assistant" watching the dash voltage gauge (questionable accuracy) as well as my trusty digital VOM. As I passed 14 volts, the engine became NOTICEABLY smoother! I took it up to Dave’s recommended 14.5 per my VOM while my dash gauge stopped right on 14 (many posts have confirmed these gauges to read about .5V lower than actual).



At 14.5V with no load, I’m now running more than a volt higher than my OEM regulator. Somewhat scary, but as mentioned, I've been buying a quality battery at the 1.5 year mark for the last 6 years. How can it get much worse? AND, everything is running stronger, even my cigarette lighter now glows bright red. I really think, problem is solved. But, I have a major trip planned next week, and need to confirm if I get extended battery life, hopefully 3+ years like my other cars. So, if you don’t see a follow-up post sooner than 1.5 years, “No news is good news!”

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[Ryan]

Interesting stuff. Let us know if there is any problem with holding water content in the battery now.

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[flash]

i went the route of the adjustable regulator, set it for 14volts, and cooked an optima. boiled it right out. made a real mess in my trunk. and that was a gel battery. if it was a lead acid battery, there would have been a lot more water and a lot more destruction.



i had a regulator fail in the denali, causing it to push 14.5 volts for a while. boiled that conventional battery out in a matter of a week.



be very careful about this. i tend to think the problem is the alternator, and not the battery or regulator. it is entirely possible that the bearing was going bad, and although it showed adequate voltage, it is not outputting adequate amperage. i would load test the alternator before going down this path.

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[jfrahm]

I have heard that bad diodes in the regulator/rectifier can cause a battery drain and it is possible to solve the battery drain problem by replacing this part. It may be that if you solved your drain issue it was the new regulator and not the higher charging voltage (which I would not recommend) that did it.



The diodes should appear to be an open circuit to the battery but in reality there is a possibility of current flow if the rectifier circuit is breaking down.

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[rhudeboye]

I'm very interested in your long term results. I tend to run through batteries in about 1 year. I also find that when my car sits for a week the battery always needs a jump. I've ordered new cables from higher connection in hopes that it would solve my issues. Perhaps a new regulator wouldn't hurt either.

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[flash]

load test the alternator. i can't count the number of alternators i have found that are not outputting full amperage anymore, due to worn bearings.



it's not about volts. it's about amps.

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[rhudeboye]

will do.



thanks Flash

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[rhudeboye]

If my alt needs replacing, is there one particular brand that's superior or inferior to the rest?



http://www.autopartswarehouse.com/mmp/po...parts.html

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[RHille]

Well, it's now been over a year since installing variable voltage regulator which I've maintained at 14.5 V no load voltage output. Only regret: I should have made this change when I bought the car 7 years ago....would have saved me $$$ and hassle replacing batteries every 1.5 years. Have taken several 3-4 day trips as well as numerous quick runs to the store, etc. Absolutely NO PROBLEMS, and car runs better and starts easily after occasional 3+ weeks of sitting without a trickle charger. Have gotten used to seeing my voltage gauge sitting just at the 14V mark....touch higher when first get going...touch lower with AC and radiator fans turn on.



Have kept checking water level for possible boil over....put maybe an ounce or two in cell closest to firewall, but that's it...and as I recall this rear most cell is most subject to loss (Why?? Don't know, but have seen with several batteries in this car). For those still concerned with water loss/boil over, check out these sites....Optima (http://www.optimabatteries.com/us/en/sup.......Trojan (http://www.trojanbattery.com/BatteryMain...rging.aspx) And I'm sure there are others that confirm that 14.5 V charging is WELL WITHIN tolerance for conventional batteries.



Will check back in another year to confirm my present battery gets to the 2 year mark....would beat all predecessors by 6 months. Hope this helps anyone out there that's had similar problem with their 968's battery life.

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[968Syncro]

Thanks for the update, an interesting problem, and a good read. I have never had a big problem with battery life in the 968, new one in 2006 and then again in 2009; I normally expect about 4-5 years per battery, so perhaps two in six years is a bit frequent. I can't help but think that there is some other problem in play with your car, as if charging at 14 or 14.5 volts is covering up some other problem / root cause of failed batteries. Charging at 13.5 volts should be fine -- for example the charging voltage in my car drops to "12.something" pretty soon after starting the car suggesting that 13.5 is no longer needed and the regulator adjusts accordingly. Also would be interested to know why your battery didn't get damaged at the higher charging voltages when Flash reports differently -- different batteries I suppose.



Thanks for reporting back, that is really useful and a great service to the forum!



Roland

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[ds968]

I get about 3 to 4 years years out of my batteries, whether in the 968 or any of my other cars.. but at about $ 100 per, does it really matter if you replace them even as frequetly as once a year ?

also, on the 968 which is only a weekend driver now, I started to keep a trickle charger on the battery for the last couple of years

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[SILVY968]

Rhudeboye,



Used the one that Schucks sells. swap the pully.

Brian

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[psuphoto]

Awesome information! Now I know my 968 is normal (almost).

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[snova]

sounds like the problem I have been having.  Definitely heat related in my case.   When the car is cold it charges well... if I drive it hard for a while.. the generator will stop charging and the voltage drops to just above 12v... if I then chill out and drive casually, the needle eventually jumps back to around 14v and it charges again.  Kills my batteries in a couple years.

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[MCL968]

sounds like the problem I have been having.  Definitely heat related in my case.   When the car is cold it charges well... if I drive it hard for a while.. the generator will stop charging and the voltage drops to just above 12v... if I then chill out and drive casually, the needle eventually jumps back to around 14v and it charges again.  Kills my batteries in a couple years.

Sounds like the regulator at the back of the alternator is failing. They can be replaced without pulling the alternator if you are limber and resolute.

 

Have you replaced the deadly wire from the alternator to the starter and the trigger wire for both the starter and the alternator?

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[ds968]

My mechanic replaced the voltage regulator without moving the alternator, but it wasn’t easy by any means ; access as well as visibility to what you’re doing is a huge challenge ( much of it has to be done blindly just by feel ), so you have to be somewhat of a contortionist and have the right tools you can squeeze in there.  And he did that before the supercharger was in there, now it’d be an impossible task, without major disassembly work .. 

 But on the bright side, at least in our cars the regulator is separable and can be bought by itself, whereas in the majority of “newer” cars  it’s integrated with the alternator so if it goes bad, you’re stuck buying and replacing the whole thing .   

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[MCL968]

I plan to replace the stock regulator and brushes this spring, since the car seems to have too little voltage and the battery always seems to be on the low end of charged.

 

The wires were replaced about 10 years ago with heavier units, and the cables are all in good shape. I need to do the grounds at the same time.

 

This is the regulator I am looking to use, it is adjustable so you can dial in the right voltage at the battery and not rely too heavily on the gauge. The seller tells me that it is a direct replacement for our 968 alternators.

 

https://www.ebay.com/itm/291991290732

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[Waylander]

From changing a few just getting the cover off is fun, faffing about trying to hold at 2000 rpm with your arm in that tiny space and a hot engine will be next to impossible

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[snova]

I bought an external voltage regulator with spade connectors  going to a separate bosch brush holder.  The idea was I was going to move the external voltage regulatory

to a colder area as my regulator would stop working when it got hot inside the engine bay.   However, the separate brush holder didn't fit into the 968 alternator correctly.

So I was going to modify the stock voltage regulator which is integrated into the brush holder to rip out the integrated voltage regulator and attach spade connectors to allow me to use the existing brush assemble, but use the external voltage regulator.  In the process of doing this, the D+ brush broke off.   So I guess I'm ordering a new integrated voltage regulator/brush assembly and will give it another try.  Maybe there was already a crack in the original brush and the heat would make it not work right?  who knows.. you would think the spring loading of the brushes would be tolerant even if it had a hairline crack in the brush.    If the new integrated brush holder with voltage regulator starts to fail again with heat, then I'll go back to my original plan to separate the brush holder from the voltage regulator and move the voltage regulator to a location that is much cooler.   Kind of a silly fan design if you ask me... it blows from the front but the voltage regulator electronics are hidden away in the back, completely unventilated by that fan. Else the hot air is being pushed out of the housing, directly at the voltage regulator electronics. 

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[MCL968]

I bought an external voltage regulator with spade connectors  going to a separate bosch brush holder.  The idea was I was going to move the external voltage regulatory

to a colder area as my regulator would stop working when it got hot inside the engine bay.   However, the separate brush holder didn't fit into the 968 alternator correctly.

So I was going to modify the stock voltage regulator which is integrated into the brush holder to rip out the integrated voltage regulator and attach spade connectors to allow me to use the existing brush assemble, but use the external voltage regulator.  In the process of doing this, the D+ brush broke off.   So I guess I'm ordering a new integrated voltage regulator/brush assembly and will give it another try.  Maybe there was already a crack in the original brush and the heat would make it not work right?  who knows.. you would think the spring loading of the brushes would be tolerant even if it had a hairline crack in the brush.    If the new integrated brush holder with voltage regulator starts to fail again with heat, then I'll go back to my original plan to separate the brush holder from the voltage regulator and move the voltage regulator to a location that is much cooler.   Kind of a silly fan design if you ask me... it blows from the front but the voltage regulator electronics are hidden away in the back, completely unventilated by that fan. Else the hot air is being pushed out of the housing, directly at the voltage regulator electronics. 

In my searching for a solution to this, I also discovered that the Vanagon regulator will fit and it is set to 14v, not the lower value used on the 928/968 unit.

 

Also: Martin, as usual you are correct. Getting in there to adjust that tiny trim pot would be next to impossible. Plus, there is a hole in the back of the regulator that could cause all manner of problems. I am now considering the stock or the Vanagon units. What to do...

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