Low engine running voltage question

[Pumba]

Hi guys,

I have a 1995 110 tdi defender with a ABR-sidewinder dual battery system and 2 brand new optima red and yellow tops plus a recently installed engel fridge attached to the second battery.

Since installing the fridge 2 days ago ive been keeping a close eye on the voltage on both batteries while driving and parked up and ive noticed the running voltage will be random. This morning on the way to work (45 min drive) it was 12.9 is and up to 13.2V which is what i usually see it at in the past prior to the fridge (the highest ive ever seen it go in the past was 13.9V) but later in the afternoon while driving home i noticed it stayed at 12.5V max even while on the highway. Ive left the fridge on since ive installed it and even with the vehicle being parked for 8 hrs in the sun the yellow top has yet to drop below 12V which im quite happy with.

My question is should i be worried about the 12.5v im getting while driving? My understanding is that the alternator will drop voltage when the battery is getting close to charge but i didnt think it would get that low? Should i consider a larger or new alternator?

Cheers, Dave

[d2dave]

Hi guys,

I have a 1995 110 tdi defender with a ABR-sidewinder dual battery system and 2 brand new optima red and yellow tops plus a recently installed engel fridge attached to the second battery.

Since installing the fridge 2 days ago ive been keeping a close eye on the voltage on both batteries while driving and parked up and ive noticed the running voltage will be random. This morning on the way to work (45 min drive) it was 12.9 is and up to 13.2V which is what i usually see it at in the past prior to the fridge (the highest ive ever seen it go in the past was 13.9V) but later in the afternoon while driving home i noticed it stayed at 12.5V max even while on the highway. Ive left the fridge on since ive installed it and even with the vehicle being parked for 8 hrs in the sun the yellow top has yet to drop below 12V which im quite happy with.

My question is should i be worried about the 12.5v im getting while driving? My understanding is that the alternator will drop voltage when the battery is getting close to charge but i didnt think it would get that low? Should i consider a larger or new alternator?

Cheers, Dave

Definitely should be worried. The minimum voltage you should have is in the high 13's. When a battery is flat the alternator has to work a lot harder, so voltage will be a bit lower.

When the battery is charged, the alternator is not working hard so can supply a higher voltage. You should always have a higher voltage on a charged battery.

Regardless of what accessories are running, when the engine is running you should always have a minimum voltage of high 13's.(with the exception of a winch or anything that is pulling 100+ amps)

[justinc]

If your 110 still has the original type of alt it will only be 65A output. The discovery alt is 100A and a direct fit although the belt length changes on any 300tdi from TA VIN number. The optimas do req a decent current so perhaps an upgrade to the disco alternator is the first stage...?

Jc

[Pumba]

Cheers for the reply Dave thats what i was thinking

Just now when ducked out to the car now and with the engine running and fridge unplugged im getting
12.86V at alternator
12.77V at battery
and 12.46V at battery with engine off

[Pumba]

If your 110 still has the original type of alt it will only be 65A output. The discovery alt is 100A and a direct fit although the belt length changes on any 300tdi from TA VIN number. The optimas do req a decent current so perhaps an upgrade to the disco alternator is the first stage...?

Jc

Sounds like a good idea JC, i was looking at the disco alts for when i plan to add more electrics later on but might be worth investing in one now

[justinc]

Thats too much volt drop at the battery too. Make sure you aren't experiencing any wiring issues when the alternator is trying to push 50+amps into the batteries or you'll soon find the problem...😮😈

Jc

[d2dave]

Cheers for the reply Dave thats what i was thinking

Just now when ducked out to the car now and with the engine running and fridge unplugged im getting
12.86V at alternator
12.77V at battery
and 12.46V at battery with engine off

It is not charging. Regardless of whether it is 65 amps or a Disco 100 amp is irrelevant.

A fully charged battery should be 12.7 volts when at rest.