How long can I go after Alternator stops working w/four 12v batts? and diagnising/fixing 200amp hummer alt on LMTV

[coachgeo]

Looks like with depth of four batts.... you can easily do 30 miles. Stays at 24v on dash voltmeter.

not sure why yet but Tues. on its typical 30 mile round trip of late I saw 24v. NOT 28v like usual.... G!@#$% gut punch. No alternator charging

Anyway...... to work and back home is approx 30miles. (getting 6mpg if anyone cares). Half of round trip requires headlights (return trip). Do not have LED lights and one headlight is Halogen for brighter view on driver side.

. No problems at all with transmission.
. Lights do not seem to dim.
. 200amp Hummer alt.... so found no reason to drop to two batts.; thus still running four thankfully. More reserve to use.
. the four are 12v type 24 standard Lead Acid batts. (Everstart)
. Wed morning prior to charging... all the batts were between 12.2v and 12.5v. Forgot to mentally record which were at what. (see reference bottom of this post

- back pair by chassis rail... where 12v lights pull their juice from if I recall right.. dropped to 60% charge. both days (looses 40% charge).
>>>>After an hour and half of charge that 12v pair is up to 80% (according to smart charger read out) It charges at 15amp. (will finish top off in morning.
- Center road side pair seems to loose lot less volts..
>>>> one 10amp charger on that 12v pair. tops them up in about hour and a half.

Friday is first day will have full day available and can risk pulling things apart to trouble shoot. Next day will be Sunday. (other days have to worry about butting things up to get to work... now that it is my only transport... cant take that risk so its charge only.

reference chart for 12v lead acid (generic) at resting voltage


12V Flooded Lead Acid Batteries

Voltage	Capacity
12.64V	100%
12.53V	90%
12.41V	80%
12.29V	70%
12.18V	60%
12.07V	50%
11.97V	40%
11.87V	30%
11.76V	20%
11.63V	10%
11.59V	0%

 

[DeMilitarized]

Looks like with depth of four batts.... you can easily do 30 miles. Stays at 24v on dash voltmeter.

not sure why yet but Tues. on its typical 30 mile round trip of late I saw 24v. NOT 28v like usual.... G!@#$% gut punch. No alternator charging

Anyway...... to work and back home is approx 30miles. (getting 6mpg if anyone cares). Half of round trip requires headlights (return trip). Do not have LED lights and one headlight is Halogen for brighter view on driver side.

. No problems at all with transmission.
. Lights do not seem to dim.
. 200amp Hummer alt.... so found no reason to drop to two batts.; thus still running four thankfully. More reserve to use.
. the four are 12v type 24 standard Lead Acid batts. (Everstart)
. Wed morning prior to charging... all the batts were between 12.2v and 12.5v. Forgot to mentally record which were at what. (see reference bottom of this post

- back pair by chassis rail... where 12v lights pull their juice from if I recall right.. dropped to 60% charge. both days (looses 40% charge).
>>>>After an hour and half of charge that 12v pair is up to 80% (according to smart charger read out) It charges at 15amp. (will finish top off in morning.
- Center road side pair seems to loose lot less volts..
>>>> one 10amp charger on that 12v pair. tops them up in about hour and a half. (MAYBE*)

* say "maybe" cause no batt. wires were removed to charge. So the new fancy smart 15amp charger on the one pair on chassis rail side... may have some juice going also into the other pair on center road side... and confusing older school 10amp charger put there? Maybe this cross over causes it to kick on its fully charged green light on denoting full charge... when they may not actually be. Will update tomorrow if I learn more as I finish up the charging for another run to work.

Friday is first day will have full day available and can risk pulling things apart to trouble shoot. Next day will be Sunday. (other days have to worry about butting things up to get to work... now that it is my only transport... cant take that risk so its charge only.

reference chart for 12v lead acid (generic) at resting voltage


12V Flooded Lead Acid Batteries

Voltage	Capacity
12.64V	100%
12.53V	90%
12.41V	80%
12.29V	70%
12.18V	60%
12.07V	50%
11.97V	40%
11.87V	30%
11.76V	20%
11.63V	10%
11.59V	0%

I tried to limp my truck home on low voltage and screwed something up with my transmission when the converter unlocked from the controller losing power going up a hill in 6th. Don't recommend

 

[coachgeo]

I tried to limp my truck home on low voltage and screwed something up with my transmission when the converter unlocked from the controller losing power going up a hill in 6th. Don't recommend

you must have been extremely undercharged. did you test the voltages as pairs and individually?

 

[DeMilitarized]

you must have been extremely undercharged. did you test the voltages as pairs and individually?

No just bought the truck, new batteries, charged them, threw them in the truck and went for a 15 mile drive back home and then the tcm died unlocking the converter and spilled fluid out the bellhousing. Would limp along sometimes but now getting a code 25 11 and did all the troubleshooting tips and nothing. Even checked the tcm and it is good.

 

[coachgeo]

Decided not to trust smart charger. Think it's got Drain Bamage.

Banks after charging and sat to reach Rest State:

-Rear bank using smart charger says they are 80% charged.
>>> But voltage meter AND chart above says they are 100% charged (12.8v)
>>> Older Dumbish charger says bank is full also

- Front bank. using smart charger says they are 80% charged.
>>> But voltage meter and chart above says they are 100% charged (12.6v)
>>> Older Dumbish charger says bank is full also

 

[coachgeo]

No just bought the truck, new batteries, charged them, threw them in the truck and went for a 15 mile drive back home and then the tcm died unlocking the converter and spilled fluid out the bellhousing. Would limp along sometimes but now getting a code 25 11 and did all the troubleshooting tips and nothing. Even checked the tcm and it is good.

ok.. not enough time/history to know the issue yet if it is battery related. sorry for your troubles... must be frustrating

 

[MrMikey4026]

Mine went 20 miles, night time, headlights on. Transmission went into limp mode but I made it to work.
Then I got the pleasure of replacing the broken lower alternator bolt.

 

[GeneralDisorder]

Highly dependent on your batteries - both type and condition as well as ambient conditions. Under perfect conditions, all lights off to conserve power, etc I would hazard a guess that 50+ miles wouldn't be out of the question. One of the reasons I'm setting my rig up for my solar panels to charge my truck batteries if I desire it, and for my alternator to charge my house batteries, etc. Options. And I do think one of the reasons the military uses so much battery is for just such conditions.

 

[Ronmar]

It probably depends more on your charging capability with only 30 miles, perhaps an hour driving total?

With 4 decent batteries, charged, you should have 240AH. The total lighting load is ~25A@12. Thats double the standard 20 hour rate(12A) that the 240AH rate was determined at, so peukert will get his cut, but you should be good for 4-5 hours comfortably lights on if it is not too cold. I dont think the 24v load is anywhere near this, so should also be good. I would limit headight use as much as possible...

The ability to sustain this rests on your ability to fully recharge the 0-12V batts and the 12-24V batts, since lights on, the 0-12 batts will discharge much more deeply without the dual volt alt to balance them. A 24v charger will not recharge them equally, so you need a pair of 12V chargers in series and connected like the batts on the ground-, 12 and 12-24v terminals. You must use ungrounded chargers to do this(2 flat prongs on plug, plastic cases). They also need to be large enough to fully recharge the batts in the time allowed.

I just went a good part of winter without an alternator, same type of commute with lights on the last half getting home in the evening, by plughing it in to a charger every evening untill my workspace was available to change out the alt...

 

[Ronmar]

Batt voltage to gauge capacity is only good after the batteries are stabilized, so it is not particularly useful when a load is applied… y0u need to let the batteries set 30 minutes unloaded to allow the electrolyte to equalize somewhat, for that volt to state of charge table to be applicable…

 

[Ronmar]

No just bought the truck, new batteries, charged them, threw them in the truck and went for a 15 mile drive back home and then the tcm died unlocking the converter and spilled fluid out the bellhousing. Would limp along sometimes but now getting a code 25 11 and did all the troubleshooting tips and nothing. Even checked the tcm and it is good.

Thats weird. I am thinking you had something else going on. Dropping power should not be catastrophic for the transmission. It directs hydraulic pressure to clutches with electric power to solenoid valves. When you drop power, these valve stop sending fluid to clutches. no clutches, no engagements, kinda like bumping a manual transmission into neutral. The lockup clutch in the converter uncoupling should also be no big deal, as it simply goes back to fluid coupling, a mode that is capable of handling as much torque as the engine can create…

is there a discussion on this problem somewhere, dont want to hijack Geos…

 

[coachgeo]

You know why it is going to storm here heavy tomorrow. .......

Cause I turned down extra hours at work to work my my alternator. grrrr

 

[GeneralDisorder]

Do you have LED's on the voltage regulator? If so what are they showing?

 

[87cr250r]

You can calculate this. The batteries have an amp-hour capacity. If it takes 10 amps to keep your truck running and you have 100Ah capacity then you can assume you can run for 10 hours. This number decreases as the batteries age. Batteries in series have the same Ah as a single battery. Batteries in parallel have the single Ah multiplied by the number of batteries.

 

[Ronmar]

You can calculate this. The batteries have an amp-hour capacity. If it takes 10 amps to keep your truck running and you have 100Ah capacity then you can assume you can run for 10 hours. This number decreases as the batteries age. Batteries in series have the same Ah as a single battery. Batteries in parallel have the single Ah multiplied by the number of batteries.

Not quite. That 100AH rating was for a 20 hour discharge rate(they do other ratings like 5 and 10 hours, but a 20 hour rate is the norm), so for a 100AH battery that is a 5A Load. As you increase the load above that 20 hour rate, the battery drops in efficiency. Basically the added current draw thru the cells generates heat in the battery that also consumes battery energy.

This is known as Peukert’s law some really detailed battery specs will show the Peukert factor, it is typically 1.2-1.6 for a wet cell lead-acid battery. It can also be determined by test discharging batteries, but basically when you up the discharge current above the 20 hour rate, the capacity drops off drastically. There are peukert calcs online and calcs for determining the peukert factor, but even at a low factor of 1.2, that 100AH battery with a 10A load will last about 6 hours to full dischrge, NOT 10… it also becomes worse with temp drop, and as you mentioned age… Conversely if you discharge at a rate lower than the 20 hour rate, you will get more than 100AH out of the battery…

 

[Ronmar]

So have you ordered your 24v alt and 24-12V converter yet? Now is the time to convert

 

[coachgeo]

So have you ordered your 24v alt and 24-12V converter yet? Now is the time to convert

priority is getting my daily driver going. only making 11 dollars a day by time pay fuel. Oh well.. that is the cost of having principles. Will figure something ou.

 

[coachgeo]

Interesting phenominom. Been nothing but storm after storm here... or just Farmer happy rain so all can do is charge batteries with the 110v charges for few hours then go to work... Wash rinse repeat.

Well last couple days it would jump to 28v charge randomly.... I've not found a pattern I trust. Might be corrosion in a wire in light circuit cause a HEAVY voltage draw.. or corrosion around PDP causing not full voltage to batts.... orrr...... cell in a battery not charging happy (all are 7/18 dated) ...... (two charge slower.. and one of those two even slower).. not sure what it is... but at least symptoms are forming some kind of pattern.

Have a pulse repair doing its thing on the slow batt right now. then will charge tomorrow. Will be interesting to see results

 

[GeneralDisorder]

Well - I deal with a lot of batteries being in the automotive industry and I can say that the quality in recent years has trended down - I'm told at least partially being built to a price but also the increasing use of "dirty" recycled lead that is not of the best quality. At any rate AAA (who sells a LOT of batteries right off their tow contractors trucks) compiles statistics on the life of car batteries and has concluded they have an average lifespan of 3 to 5 years:

How Long Do Car Batteries Last

There is no simple answer, but based on decades of industry experience, we know that three key factors affect the life of a car battery: time, heat and vibration.

www.aaa.com

Given your batteries are from 2018 - in my personal opinion they are due for replacement.

 

[coachgeo]

well since could drive the VW again... have not dove into this till today since not driving truck at moment.

Before start on this adventure. today:
-each batt by chassis showed 12.64 volts which appears to me to 100% SOC
- each batt out out most end of batt box showed 12.4v or 80% SOC

Swapped to two batts. Pretty sure I wired it up correct. shows 24v at Nato and at batts. Engine starts.... no smoke emitted. ...

Unfortunately NO CHANGE. I get 28v showing nowhere (dash or at batts) nor 14v anywhere. .

Only getting high 24v at dash and batts and 12v per batt .

soon as I can I'll tilt cab and check excite wire to alt. hope it is that.