# Dual battery testing procedure



## phideaux

I think I'm on the right track here, but yall can help steer me.
I dont have a battery load tester.

My truck is a Dodge Cummins diesel, and it uses 2 batteries.
They are 1000CCA , 150 reserve CA, 
So they are big heavy duty batteries, hooked up in parallel.

Problem .....last 3-4 times I started the truck, they had that draggy ,weak sound.

So today I throw the big battery charger on them and set it at 35 amps.

Its taking 30 amps for a minute, then drops to 20 amps and stays there,
and....I get this hot acid gas smell really bad, almost immediately.

So I shut it off, disconnected both batteries.

Put the charger on the driver side battery for 5 minutes, no smell, and charger droped to 10 amp, and stayed there (why?). Removed charger, checked voltage @13.2 v. thats good.

Put the charger on the passenger side battery, within 30 seconds I had that acid gas smell, charger did drop to 15 amps, and stayed there.
Removed charger and checked voltage @11.2 v.

I'm assuming that the passenger battery is bad.

But, I thought that the charger would drop to 0 amps on a good battery, so maybe the driver side is weak also....

Did I do this right?

Any other suggestions?

I know that all batteries in a pack will dive down to the level of the weakest one. 
I think I gotta buy 2 new batteries...:surrender:. man they are spensive.


Jim


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## Flight1630

If you goto your local garage they should have a load tester. A battery charger in my experience will always push into a bartery even when fully charged. But how you explained it it does sound like the left side that's bad.


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## backlash

Most auto parts stores should be able to test the batteries.
It sounds like you do have a bad one and it will not get better.
Better to get it fixed now rather than in the middle of nowhere at the worst possible time.


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## obg12

phideaux said:


> I think I'm on the right track here, but yall can help steer me.
> I dont have a battery load tester.
> 
> My truck is a Dodge Cummins diesel, and it uses 2 batteries.
> They are 1000CCA , 150 reserve CA,
> So they are big heavy duty batteries, hooked up in parallel.
> 
> Problem .....last 3-4 times I started the truck, they had that draggy ,weak sound.
> 
> So today I throw the big battery charger on them and set it at 35 amps.
> 
> Its taking 30 amps for a minute, then drops to 20 amps and stays there,
> and....I get this hot acid gas smell really bad, almost immediately.
> 
> So I shut it off, disconnected both batteries.
> 
> Put the charger on the driver side battery for 5 minutes, no smell, and charger droped to 10 amp, and stayed there (why?). Removed charger, checked voltage @13.2 v. thats good.
> 
> Put the charger on the passenger side battery, within 30 seconds I had that acid gas smell, charger did drop to 15 amps, and stayed there.
> Removed charger and checked voltage @11.2 v.
> 
> I'm assuming that the passenger battery is bad.
> 
> But, I thought that the charger would drop to 0 amps on a good battery, so maybe the driver side is weak also....
> 
> Did I do this right?
> 
> Any other suggestions?
> 
> I know that all batteries in a pack will dive down to the level of the weakest one.
> I think I gotta buy 2 new batteries...:surrender:. man they are spensive.
> 
> Jim


You'll need to disconnect the one on the passenger side to get a good load test on them,also I switch mine from side to side every year because they never charge equally in my truck


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## hiwall

A simple battery hydrometer can often tell you whether a battery is good or not. Less than $10 and they last about forever.
https://www.amazon.com/E-Z-Red-SP101-Battery-Hydrometer/dp/B000JFHMRU


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## Pessimistic2

obg12 said:


> You'll need to disconnect the one on the passenger side to get a good load test on them,also I switch mine from side to side every year because *they never charge equally in my truck*


Why is that?? Mine don't either, and it's a custom installation.:dunno:


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## tmttactical

Pessimistic2 said:


> Why is that?? Mine don't either, and it's a custom installation.:dunno:


I am going to take a guess: "least path of resistance". Wire / cables different length, different amount of corrosion on connectors, different resistance in battery plates or any number of other points of resistance. Just saying!


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## azrancher

hiwall said:


> A simple battery hydrometer can often tell you whether a battery is good or not. Less than $10 and they last about forever.
> https://www.amazon.com/E-Z-Red-SP101-Battery-Hydrometer/dp/B000JFHMRU


Yes a hydrometer will check each cell... assuming you have caps on your batteries, most are now sealed except for a breather hole, I think this was caused shortly after the Californians made gas cans that require 3 hands to spill twice as much fuel as before.

*Rancher*


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## Viking

If they are like the dual batteries on my Ford diesel, they don't have isolation from one another, so if one battery is bad it will drag the good battery down. I installed a isolation relay and a charge diode but, though it worked, the relay was not heavy enough to do a good job of providing full amperage to the starter so they are back to being directly connected parallel. Generally the rule of thumb is to install two new batteries at the same time, probably a good idea to check that they were manufactured the same day if possible because they would be, more likely, evenly matched.


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## zimmy

*Battery*



Viking said:


> If they are like the dual batteries on my Ford diesel, they don't have isolation from one another, so if one battery is bad it will drag the good battery down. I installed a isolation relay and a charge diode but, though it worked, the relay was not heavy enough to do a good job of providing full amperage to the starter so they are back to being directly connected parallel. Generally the rule of thumb is to install two new batteries at the same time, probably a good idea to check that they were manufactured the same day if possible because they would be, more likely, evenly matched.


I agree, replace both batteries at the same time, with the same type.


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## TheLazyL

zimmy said:


> I agree, replace both batteries at the same time, with the same type.


I'm cheap. Replace both batteries I'm in agreement on BUT first I'd disconnect the bad battery. Run just on the one battery until cold weather THEN replace both of them. Squeeze the good battery's life out of it for as long as I could.


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## phideaux

I pulled the battery that checked low voltage, and it has a sticker on the side 9/12. Instantly starts boiling/gas fumes, with charger on it, and still only 11V.

So, that seems a short life of 4 1/2 years. Who knows if they were maintained or not, as I've only had them since last Sept.(9 mo)

Im on the Cummins forum , and those guys talk about 10 years+ on batteries, if maintained properly.

Yes , the 850 CCA @0 deg, is what they are , 1000 CCA at 32deg.

Thats what the factory uses , and factory are Mopar @$250 each.

Johnson Controls makes most of these batteries ,The Autozone Duralast, and the WalMart Everstart are same battery just labeled different, $60 diff in price.

Autozone $154, Walmart $93 ea.

I have one old battery in the shed for a core, and the bad one from the truck, and will keep the good one from the truck, for a emergency spare.

Will replace both. Probably, WalMart, cheapest, then Napa is $123. 

The Cummins boys like the Walmart batteries. 

If I get 4-5 years for $186 , I'm happy.Maybe 10 years in my case (1000 miles a year)as I'm a picky nut on maintenance.


Jim


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## terri9630

azrancher said:


> Yes a hydrometer will check each cell... assuming you have caps on your batteries, most are now sealed except for a breather hole, I think this was caused shortly after the Californians made gas cans that require 3 hands to spill twice as much fuel as before.
> 
> *Rancher*


You can buy the old style replacement nozzles at Tractor Supply and Amazon. I've replaced all of the ones on my cans. They even come with vents that you can install on the gas can.


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## terri9630

phideaux said:


> I pulled the battery that checked low voltage, and it has a sticker on the side 9/12. Instantly starts boiling/gas fumes, with charger on it, and still only 11V.
> 
> So, that seems a short life of 4 1/2 years. Who knows if they were maintained or not, as I've only had them since last Sept.(9 mo)
> *
> Im on the Cummins forum , and those guys talk about 10 years+ on batteries, if maintained properly.*
> 
> Yes , the 850 CCA @0 deg, is what they are , 1000 CCA at 32deg.
> 
> Thats what the factory uses , and factory are Mopar @$250 each.
> 
> Johnson Controls makes most of these batteries ,The Autozone Duralast, and the WalMart Everstart are same battery just labeled different, $60 diff in price.
> 
> Autozone $154, Walmart $93 ea.
> 
> I have one old battery in the shed for a core, and the bad one from the truck, and will keep the good one from the truck, for a emergency spare.
> 
> Will replace both. Probably, WalMart, cheapest, then Napa is $123.
> 
> The Cummins boys like the Walmart batteries.
> 
> If I get 4-5 years for $186 , I'm happy.Maybe 10 years in my case (1000 miles a year)as I'm a picky nut on maintenance.
> 
> Jim


I have a 02 dodge with the Cummins turbo diesel and have never had a battery last more than about 5 years. I don't know how they have had them last 10.


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## phideaux

terri9630 said:


> I have a 02 dodge with the Cummins turbo diesel and have never had a battery last more than about 5 years. I don't know how they have had them last 10.


I know what your saying.

They use those *smart battery tenders*, and only use batteries that you can monitor and maintain water levels.
Some have even gotten 15 years.:dunno:

Thats the way(Smart battery charger,Genius) I keep my battery pack for the solar house batteries, (which don't get hammered with use every day), same on my Golf cart and MTV, last batteries on my Golf cart were 12 years old and still going, just weak.

Never let them go below 80% charge, keep the water level proper, keep terminals clean....life expectancy on them is infinite.

Auto batteries is a different ball game.

Jim


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## readytogo

hiwall is right on the hydrometer testing if your battery is the type that is not a seal battery but you will need a simple multimeter for a cranking test ,positive to positive negative to negative set at 20 amps ,crank the Eng. and if it drops bellow 10 amps you have a problem. Make sure all your connections are clean and shiny ,used Dielectric grease to coat the battery post and all other electric connections to prevent corrosion. You mention 2 batteries ,you need a battery isolator to prevent drainage from the main battery and it would be nice to have a solar battery charger ,they keep your battery charge but not over charge .A good alternator should give you 14.5 volts at least.


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## Flight1630

Caribou said:


> When I get a new battery I wash with soapy water, rinse and let dry. Then I tape the terminals and spray with a clear lacquer. My batteries last twice as long as advertised. An electronics tech friend of mine gave me this trick forty years ago and it works for me.


Hmmm I never heard of that before but me thinks it would work very well. I'm going to have to try that trick


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## readytogo

Not all batteries are made the same just like the weather ,here in Miami summer is in the 90`s and the engine compartment can get in the 100`s so a battery suffers a lot .The average life is about 5 years or so ,so a good maintenance is necessary .Clean terminals and tight connections a good alternator and a battery solar keeper would help also .The Sub is free and a fully charge battery keeps from cycling so much ,a battery has so many cycles to it. But like anything mechanical sooner or later it will fail so is time to get the emergency mason jar out and buy a new one ,after all we are a prepared society .


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## Tirediron

Check to see if a Group 31 heavy truck battery will fit, they are ment for rough service, the Batteries in my Peterbilt are more than 10 years old, Live in a rough climate and start a 1000 cubic inch Caterpillar with ease.
also follow Caribou's method


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## phideaux

Ok, I did decided that the one on the passenger side was a bad battery.

So I went to Walmart , bought 2 new Johnson Controls, Everstart Super Maxx , Type 65N, 850 CCA a 0 deg.

Man what a pain to install with those felt blankets around them.

I did pull all connections, for both batteries , and the crossover, which were some rusty , but no white type oxidation, 
Cleaned up like a new penny, 
Used dielectric lube on all bolts, nuts, terminals, 

Hit the key....bang ....never fired up that quick..

COOL....I'm happy.



Jim


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## mosquitomountainman

Glad you got it going. Lots of good tips here. Batteries hooked together will never be better than the weakest battery. That's why it's best to replace them all at once. If you have a good load tester you might be able to fudge on this a bit if you have some that test well and just replace the weak ones. I use a load tester from Harbor Freight Tools. They're cheap and work okay IME. I used the 100 amp model. 

The reason one battery was taking more to charge it up was because it was never reaching full charge. It's like trying to fill a leaking bucket. The water runs out as you're trying to fill it so you have to keep adding more water at a higher rate.

Some chargers will never drop to zero (or even a trickle charge of one amp) on higher settings. Even if the battery is full they'll stay at 10 amps or so. They're designed as battery chargers rather than for simply maintaining a charge like a trickle charger. I've used "smart chargers" and while they have some advantages they also have some disadvantages. A completely dead battery has very high resistance and often needs a hefty fast charger to recharge it. Even then it may take several hours to reach full charge.

Automotive btteries have thin plates that recharge quickly but also discharge quickly under load. the less they're discharged the longer they will last.

If you have one battery in a series that doesn't reach full charge you need to check the way they are wired. The best way is to have the first battery wired to the charge/discharge side on the positive post. Then connect the next battery's positive post to the positive post of the first battery and keep it up on down the line. Connect the ground wire from the first battery to the second etc. and ground the last one in the series directly to ground. That way when it charges the electricity must travel equally through every battery to make the circuit. If you have power to the first battery and also ground the first battery then it will do 80 percent of the work while the other batteries just kind of coast along. They will seldom reach full charge in that configuration. CAUTION: be sure that the cables are large diameter and can handle the load. If they aren't they can overheat and start a fire.

The most "wear" occurs in batteries in the charge/discharge cycle. The less you discharge them the longer they'll last so keep your rig in good shape so that it starts easily. Some people use deep cycle batteries in their vehicles (I do on my pickup with the winch on it). Just be aware that deep cycle batteries, due to their thicker plates, need to be "overcharged" occassionally for the longest life. Good charge controllers on solar power systems will do this about once a month. You don't get that on automotive charging systems. I put my pickup on the fast charger once a year (it doesn't get used often ... mainly for hauling firewood) and overcharge it about an hour on fast charge (40 amp charge rate) to drive the charge deeper into the plates. Seems to make the battery last longer. Do not let batteries discharge when not using a vehicle. I clean the tops of our regularly and disconnect them during winter on vehicles that sit for long periods (like the pickup and whatever motorhome we aren't going to use for awhile). Be sure to clean the tops because they can self-discharge if you don't. It goes without saying to keep the terminals/connections clean and inspect the cable ends for swelling inside the copper terminals (which indicates internal corrosion).


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## phideaux

Once I got the 2 batterries disconnected, and went thru the Volt test and recharge attemts, I knew one was definetly bad.

They are both almost 5 years old, so I just decided to replace them.
I used the bad one, and an old battery I had, for cores and kept the good one.

Like I said, I've never had the truck fire up like it did with the new ones.

Hey $198 OTD, and they are rated as some of the best batteries by the Cummins boys. (gotta be Johnson Controls).

I ordered a battery minder to help keep these full of life when the toy sits for weeks . I keep my solar 8 battery pack on one all the time. Last forever.

https://www.amazon.com/KeyLine-Char...&sr=8-2-spons&keywords=keyline+chargers&psc=1

I also learned from the Cummis forum, to swap the 2 batteries position , once a year, as the passenger battery gets all the charge before the drivers side does, due to the parallel cables and connections show minute resistance, so swapping them helps keep them balanced. :dunno:

Jim


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## TheLazyL

phideaux said:


> ...I also learned from the Cummis forum, to swap the 2 batteries position , once a year, as the passenger battery gets all the charge before the drivers side does, due to the parallel cables and connections show minute resistance, so swapping them helps keep them balanced. Jim


Interesting. I would think that (as mosquitomountainman posted) hooking them up like batteries in a solar array a person would not have to swap the batteries position to keep them balanced:

Vehicle power to Battery 1 + and Battery 1 + to Battery 2 +.

Vehicle ground to Battery 2 - and Battery 2 - to Battery 1 -.

Not being a mechanic or electrical engineer, am I missing something in my thinking?


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## forluvofsmoke

tmttactical said:


> I am going to take a guess: "least path of resistance". Wire / cables different length, different amount of corrosion on connectors, different resistance in battery plates or any number of other points of resistance. Just saying!


You're guessing correctly. Not only do different cable lengths affect resistance, but 2 or more of the same brand, type, model and age of battery will not test with the same internal resistance. Any time you run batteries in parallel you end up with variations in the amounts of actual discharge and recharge current/voltage. That's why with residential RE/Back-up battery banks it is not recommended to run parallel batteries, but instead, run larger batteries for higher capacity, or, run series strings with higher battery bank voltage (same WHrs capacity as parallel bank).


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## phideaux

I kinda think its because , on the solar array (all hooked parallel) are monitored and charged thru a PWM controller.

On the truck its a simple voltage reguator direct to the batteries, which are also parallel.

Now , if the connecting cables from Battery 1 to battery 2 were corroded, ( maybe unseen) then the first battery from the charging system would possibly overcharge , while the #2 is undercharging due to high connection resistance. No balance.

I'm sure this can happen on a solar array also, with corroded cables/connections, but the smarter PWM controller will keep them safe from overchraging.

On my 8 battery pack , I can check the voltage output on each individual battery and they are all over the place from 6.3 v up to 6.9 v. 
2 six volt in series ....4 sets in parallel...output 12 v.

Jim

OMG.... did I say all that...???


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## phideaux

Caribou said:


> If I read you right, it is better to run an eight 6V battery band configured to 48V rather than the same eight batteries configured at 12V or 24V?


Much smaller cables required for the 48v.

I suppose it will depend on what your using them for.

Jim


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## forluvofsmoke

Caribou said:


> If I read you right, it is better to run an eight 6V battery band configured to 48V rather than the same eight batteries configured at 12V or 24V?


Correct. All in series is less risk of battery discharge/charge related issues. You just have to spend the extra cash for the inverter. The upside is that the battery cable size and charge controller output cables can be reduced due to less current from the higher voltage with the same actual power usage/charge as measured in watts. The seemingly bad news is that if you lose one battery due to shorted cell, etc, you lose the entire string...no power, or very reduced output, if any. Then you just have to figure out which one died on you, which is not that difficult with a simple volt-meter or hydrometer, but you know about the problem in short order. If you were running parallels instead, you could have 1 or more strings go bad and never know it until you realized that your actual usable capacity may have diminished. Really it's a coin toss as to which is better unless you have high peak demands, which are met more easily with higher string voltage going into an appropriately sized inverter. High-output low input voltage inverters can really put a strain on the batteries and shorten their duration of cycle time quite a bit, even if cables are sized correctly, as the current doubles when the voltage is reduced to 1/2. That means each battery has to put out that much more current.

_*EDITED:*_
It really boils down to personal preference and wants/needs. If you have a critical item needing uninterrupted power, such as a CPAP, then _parallel_ (should be _series_) may not be the route for you to go, unless, you have a smaller system just for your critical items and a larger series string for your main domestic power source. It's a little more to keep track of, but good piece of mind.

Crap, sorry, Jim. Hope we don't derail this thread...this discussion should be in the homesteading electrical/energy section.


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## forluvofsmoke

Quote:
I kinda think its because , on the solar array (all hooked parallel) are monitored and charged thru a PWM controller.

Jim, the only RE/Back-up battery systems I know of that monitor individual batteries for depth of discharge and recharge voltages are Lithium Iron Phospate (LiFePO 4). These are actually designed for electric vehicles, but I have read of someone trying out these batteries in a mobile unit...RV converted bus, IIRC. He broke-down the battery pack and restrung it for 48VDC and tested them due to their light weight. Unfortunately, they suffer from higher storage temps even worse than lead-acid...storage life was very poor. Anyway, these are extremely sensitive batteries and do not have float or equalization charging. When they reach full charge voltage on the string the charger disconnects all charging output to the batteries. They will, however, return to charging mode at an adjusted output voltage/current to complete charging if a battery has indicated it is not up to specs at end of charge cycle...sort of like equalization charging for lead-acid, but a bit more tightly controlled. For this system to work properly they have independent battery cell monitoring of each cell in the string. And, no, those monitoring systems are not cheap...neither are the charge controllers.

If there is a new charge controller system available for individual monitoring of FLA or SLA types of batteries when installed in a string it's news to me...would love to read about it. If available, that technology could potentially change a lot of the periodic maintenance equalization charge guess-work and hydrometer reads to as needed only, and doing it automatically with no input from the owner/user. The only maintenance needed would be watering for FLA and terminal/cable corrosion protection. Man, now, that would be sweet!!!


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## phideaux

The best I can do there, is the NOCO Genius 7200 smart charger,
This is the one I keep on my Battery pack, until the grid goes down then I switch them over to the solar controller.

The Genius is fantastic at keeping my pack in balance , and floats them just below gaseous stage, will go thru desulforation cycle, and if I ever get a defective battery , it is suppose to alert me, but not which battery is bad, thats where I have to trouble shoot them.

Just a little back on topic.

I hooked up the 2 new truck batteries to the Genius for 30 minutes before installing , just to see them at full charge and equalize them. It took about 30 minutes , but they were almost at full charge anyway.


Jim


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## obg12

Be careful where you buy them not all are new 

http://www.johnsoncontrols.com/batteries/battery-recycling


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## obg12

The longest lasting ones I have found for my trucks 

http://www.interstatebatteries.com/...8-4294493586-4239492642-4294493584-2147384906

As far as I know they don't sell recycled batteries all new ones,also it's important to re-use the battery blanket that was on the old battery.If your truck didn't come with them a dealer can order them


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## terri9630

obg12 said:


> The longest lasting ones I have found for my trucks
> 
> http://www.interstatebatteries.com/...8-4294493586-4239492642-4294493584-2147384906
> 
> As far as I know they don't sell recycled batteries all new ones,also it's important to re-use the battery blanket that was on the old battery.If your truck didn't come with them a dealer can order them


What does the blanket do?


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## obg12

terri9630 said:


> What does the blanket do?


Keeps it from getting too hot and protects it from freezing 

http://www.cumminsforum.com/forum/0...neral-discussion/1170482-battery-blanket.html


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## mosquitomountainman

obg12 said:


> Keeps it from getting too hot and protects it from freezing
> 
> http://www.cumminsforum.com/forum/0...neral-discussion/1170482-battery-blanket.html


A fully charged battery will freeze at -76 Fahrenheit. The blanket is there to protect it from excessive heat in the engine compartment which will shorten it's lifespan considerably. A blanket will not keep a battery warm unless you have a battery heater in which case it will help the battery retain heat in cold weather while the heater is on.


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## Flight1630

mosquitomountainman said:


> A fully charged battery will freeze at -76 Fahrenheit. The blanket is there to protect it from excessive heat in the engine compartment which will shorten it's lifespan considerably. A blanket will not keep a battery warm unless you have a battery heater in which case it will help the battery retain heat in cold weather while the heater is on.


Also if like you said if it's a battery heater in it. The engine will start faster if the battery is warm.


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