Question does the bad/low battery decrease the output of the three good batteries? I connect them like the drawing. if I put the bad battery at place "D" would it affect or have no effect of the battery bank power output to engine?
You're missing a wire and a bunch of info. Is this a 24V system, or are these 6V batteries? How did you determine that one is 50%? Do you have a real carbon pile load tester? Just my opinion, but it one of the batteries has a bad cell or a few bad cells, it will quickly kill the other batteries as they try to compensate for it. You need 4 new batteries.
The weak battery always drags down the strong ones
Wes J has it right. If it is a 24 volt system like in a D10 you probably won't notice much difference in starting as one set of batteries in 24 is probably enough. The low battery will drag down the one in series with it though. The bigger question is why the one low battery? Is it older, is there some other piece of gear added that uses a lower system voltage. My last thought on the issue concerns one low battery in a series system will cause excessive charging amperage across both batteries usually causing the high battery to overcharge. Overcharging shows up as gassing and low fluid levels in the cells. In any case it is not a good thing to have happening.
thank you for your inputs,I will purchase a new battery. To save the good batteries.
Knowing what the batteries are in and what voltage would help, but having said that batteries are somewhat like a chain the weakest link determines how much a load it can carry! Also curious how you determined those percentages?
I used a battery tester. the tester displays the % of battery give my keyed input of the CCA of the battery, also the current amps of battery is displayed. QUESTION These are 950 CCA batteries I have a good 625 CCA battery any comment on putting the 625 CCA battery with the 950 CCA battery in the series? Say in location "D" on my drawing above attached file.
kshansen see my reply to John C. for information.
The machine is a CAT 120 excavator.
Take out the weak one if 12V, the weak one and it's "series partner" if it's 24V. Or get FOUR (4) new batteries. I don't know the size of these batteries, or the voltage of the machine even, but I always prefer 750 CCA batteries over higher CCA of the same size. The higher CCA is from thinner plates and less room at the bottom of the cells. Live fast, die young.
Probably not happening here but make sure you are not pulling a accessory load off one battery. If pulling twelve volts off one bank of a 24 volt system you will mess up your batteries for sure. Use a 24 to 12 transformer to pull equal off the system.
OK machine has 4 12 volt batteries. all rated at 950 CCA. It is a 12 volt starting system with 55 AMP alternator. one battery is at 100% other two are at 95%, forth is at 60% all % after charging the batteries. two sets of series; positive to red wire, negative to black wire and negative terminal to positive terminal. two of this set up. My question is; should I replace the 60% powered battery ? If I leave the 60% battery in the system will it damage the other three batteries?
If your starter and alternator say 24V on them, then you have a 24V system. If they say 12V then i give up. Yes, the weak battery can damage the three good ones. It's pair won't charge right, and the other two might drain while sitting. Have you checked the water level? and the voltage after they've sat for a week? that be more important to me than the percentage read from a high tech tester. Another question, is this a all day everyday getting paid machine, or summer weekend type work?
Your schematic seems to show two groups of batteries in series that are then hooked in parallel. If you have a 12V system, that's all wrong. I suggest having the batteries tested with a real carbon pile load tester. They should be able to output 475A for 15 seconds without dropping below 10 volts. If they can't do that, replace them. If it's a 12V system, hook all the + together, and all the - together.
Is this a series/parallel system? do you have a series/parallel switch in there that looks like this?
I've not seen a Cat 120 since the Mitsubishi days. Do you mean it is a 320 or a 312. The extra set of batteries if for when it get northern Alaska in the middle of winter cold. You don't even need that second set of batteries and I've seen plenty of machines that haven't replaced them when a set goes bad. The cable terminals are taped over and tied out of the way so they don't short out. It's really nothing to worry about.
Why does battery "B" only have 1 cable connected?
See new draw
I've never seen an E120B with a cold start system? Something else is going on with this machine.
What cold start system? or are you talking about the series parallel switch? Yes, for the third time, it will have an affect on the other batteries. It MAY damage the other two, it IS reducing the output of it's partner (C). Two things can happen: one, it maintains voltage fine, just doesn't have the amps it should. In this case it is not hurting the other two or it's partner, maybe hurting it's partner a little. Second possibility, if you disconnect the grounds from both series and let it sit a week, come back and measure the voltage of each battery separately, only the two ground cables have to be removed to do this. If the bad battery, or any other battery is more than .2V? below the others, then take that one and it's partner out if you don't have to start this in extremely cold weather. If you need four batteries to start it reliably in cold weather, get FOUR NEW batteries.
I don't know how many times we can tell this guy the same thing.
A cold start system has been an option on Cat machines for many years. Four batteries instead of two plus ether injection. People here in Washington buy into the come on all the time. I've looked at many machines with that had places for four batteries with two missing and a rusted out ether bottle still sitting the brackets and rusted through.