My batteries are not the same brand or even the same age. They are supposed to be similiar in capacity, condition etc or they might play havoc with each other.
So to test them I unhooked the negative terminal from one and started the engine. I noted the effort the starter was putting out. Then I reconnected the battery and disconnected the - terminal of the other one. I waited a few hours and started the engine using the second battery.
Both batteries seemed to make the starter put out the same sound so I concluded they are similiarly matched.
The best way to test the batteries would be with a loadmeter, that will determine the actual output capacity of the batteries. Sure, they may both roll it over, and even start it, but if one is putting out 400 cranking amps, the other 700, it's not a good situation.
The lower the output voltage and current going to a starter, it in effects creates a higher resistance, and generates more heat in the starter itself. In turn this will lead to premature failure of the starter. It also puts a greater load on the rest of the components, the solenoids, the cables, clamps, etc.
There are lots of folks here that are trying to help you out, and we realize that folks aren't always flush for money, but there are some areas that it's just not a good idea to cut corners on. It becomes a 'pay it now, or pay it later' scenario.
2001 F250 Superduty, 6.8V10, 2WD, auto. The 'family' truck.
1991 F350 4x4 E40D, N/A 7.3 Diesel, SRW, Crewcab, now with Meyer plow.
1990(?) F350 4x4, E40D, N/A 7.3 Diesel, with Meyer poly plow, needs a body swap.
1991 F250 4x4, E40D, N/A 7.3 Diesel, 'the runaway'
1989 F350 2wd C6 N/A 7.3 Diesel Dually w/flatbed dump, retired with a broken frame rail.
1988 F250 4x4 C6 N/A 6.9 Diesel, parts truck
Seriously dude, you're posting the same thing in multiple places. We are trying to help, but bandaid fixes and half-assed tests are just that.
Any good parts store should have a loadtester for batteries. If you can't physically lift them out of the truck to bring them in, have one of the associates at the store do it, thats what they are paid for. Many of the machines are mobile and so could be wheeled out to the truck.
My truck had two mismatched batteries when I bought it. I thought it started fine, until one January day when the temperature suddenly plummeted to below 20. I went to leave work, and it wouldn't start, batteries too low. I charged them up that night after getting towed home, and even swapped in a newer battery for the oldest looking one. A few days later it wouldn't start on the way to work, and this was after the block heater had been plugged in for a few hours.
That night it got a pair of new walmart batteries. Yes the Napa ones are better, and I had looked at that, but I damn well couldn't afford it. The walmart ones have lasted like 3 years, and I'm wondering how much longer, but they started my truck no problem in all sorts of weather.
So unless you want to get stranded somewhere, GET 2 NEW BATTERIES!!
1988 F250, 7.3L IDI, regular cab, long bed, 5spd ZF
Mods: ATS turbo, 3.5 inch exhaust, superduty springs front and rear, 4 gauge A-pillar pod: boost, pyro, coolant and 4th spot is switches; was 2wd, now 4wd with Dana 60 front axle
next projects: fix/complete the 3.5 inch exhaust (tailpipe exits waaaaaay to low, and needs to be extended out from under the bed) swap to a rust free cab
don't cut corners on batteries as everyone else has said. i had one shoot craps and replaced it. it worked most of the summer until one HOT september day i went out to start it and nothing.... flat nothing the one was a 1040 CA battery and the one i put in was a 1000 the 1040 both dead i had my brothers power stroke jumper cabled to it and the battery charger maxed out..... couldn't get enough juice to plug it and start it after about 45 min. so then i hooked brothers truck up to the ball and hit the plugs one last time and luckily had enough left heat the cylinders and pull start it. drove it down to the shop 20 miles. and load tested up. the 1040 only showed 200 amps and the 1000 ca only showed like 400 and that was after 45 min of charging off other truck and charger and 30 min of the alternator workin them over.
the 1 battery i got warrantied at walmart that i bought the 1000 ca one and then just got another from there so now i got 2 new ones and have had no problems starting since. i wanted to get the big john deere batteries but they were almost 200 a piece
1994 F250, IDI, 4x4, ZF5
1997 F350 CC LB 4x4, E40D, Riffraff wheel, Bellowed Up Pipes, Ceramic Coated Up and Down pipes, TS 6 POS w/ BTS Tunes, Edge Insight CTS, Riff Raff 6637 Kit, Autometer GS Water temp, Boost Pressure, and Low Side Oil Pressure. Rosewood Stage 1 injectors, 5 Inch Exhaust Downpipe Back, BTS E4OD Transmission, Duraflap Mud Flaps. Banks techni-cooler intercooler kit, 7.3 Super Duty Trans Cooler.
Well I figured out what to do thanks in no small part to you guys.
I will disconnect one of the batteries. That way there is no "two battery problem". And just because both batteries are new doesnt mean there cant be problems.
The truck starts fine on one battery. When it gets colder I will hook up the other one before starting, then disconnect it. I will put the disconnected battery on the charger every two weeks or so.
I only drive the truck to work 7 miles away on Saturdays. Otherwise it just sits waiting for me to think of something for it to do (so far I got my snowblower back from my brotherinlaw) If it starts and i get to work there is a shuttle bus there they keep equiped to jump employees with dead batteries. If it doesnt start I will just take my motorcycle or car.
If worst comes to worst theres always NAPA and a new $130 battery.
I know where you are coming from. Sometimes we have to do what we have to do to get by, even if it isn't the ideal solution. They key is to do good at work and spend/save your money wisely. You can buy a couple of matching batteries on down the road a ways.
1985 F250 Lariat Extended Cab 6.9 Diesel C6 Auto 4x4 BW1345 D50 Sterling 10.25 full float with 3.55s 20 MPG (achieved twice, averaging 16.5) 39 degree 134a A/C
But this really rasies a question in my mind. Why did Ford go with TWO small batteries, given the problems that can happen? Why not one big one? GM and Dodge do the same (2 batts) as I understand it so there must be a reason.
I wonder IS there a big battery out there that would fit the bill and would it make sense?
haha, nice mistype start lol. I run two 800 CCA batteries, the 83 has two 500 and the 84 has two 1000 CCA batteries, I dont screw around when it comes to batteries. Sometimes it sucks but you gotta do what you gotta do haha.
Quintin Aune BigBs'r #21 & Off. Slackmaster #31
1990 F-350 7.3l IDI ZF-5(sold)
2006 Ford Expedition 5.4l Eddie Bauer
2006 F-250 6.0l Power Stroke V8 85k miles XL
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