After a fairly deep discharge and a short 20-30 minute drive home, the guy at Odyssey said to turn on the headlights for a few minutes in order to get a true reading on the battery before charging it. That was when my starter and house batteries were one. Now I have a separate house battery connected through an ACR, and flipping on the lights won't effect the #2 battery. So what's a good and easily repeatable way to drain #2?
What's the best way to deliberately drain a battery?
- Thread starter JCruse
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He's trying to remove any 'surface charge'
Hook up a 12v halogen bulb for a minute, even just a bulb with some alligator clips.
Hook up a 12v halogen bulb for a minute, even just a bulb with some alligator clips.
- Thread starter
- #4
So just a bulb and socket will do? I suppose I could mount a pair of 50W halogen sockets to a board.
Yes I'm looking to remove surface charge. I've pulled the battery down to lets say 50% DOD, and the ACR has opened up the battery to alternator charge probably in just the last 10 minutes of the drive home. Now the battery charger is going to see 12.8V and think the battery is almost full. Then it'll only get a 1A charge for a short time (all #'s general) when what it needs is 50A and a 5 hour charging to put back all that was taken.
Hmmm... How hard could it be to take a spare Halogen shop light and bypass the AC portion...? That would be easier than fiddling with bulbs and wires every few days. A nice Anderson plug to go in the socket I already wired in the bumper for the charger and easy as pie.
Yes I'm looking to remove surface charge. I've pulled the battery down to lets say 50% DOD, and the ACR has opened up the battery to alternator charge probably in just the last 10 minutes of the drive home. Now the battery charger is going to see 12.8V and think the battery is almost full. Then it'll only get a 1A charge for a short time (all #'s general) when what it needs is 50A and a 5 hour charging to put back all that was taken.
Hmmm... How hard could it be to take a spare Halogen shop light and bypass the AC portion...? That would be easier than fiddling with bulbs and wires every few days. A nice Anderson plug to go in the socket I already wired in the bumper for the charger and easy as pie.
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I get what you are trying to do. Can you turn something that is connected to the house battery on for the duration of your drive to force the ACR to open up. Seems like the ACR should be a little more intelligent.
Let me make sure I understand the situation correctly. You discharged your house battery but not the starter battery and you are concerned that in the short amount of driving you are doing that the house battery is not going to be properly recharged. And you're also concerned that if you throw a battery charger on the house battery the ACR will close and because the starter battery is fully charged, then again the house battery will not get charged properly. If I've got this right, then why not just pull the small fuse that connects the ACR to ground (I think it's 5A or maybe 10A) which will disable the ACR. Then you can use a battery charger to properly change the house battery independent of the starter battery. A modern "smart" charger will sense that the house battery is very low and charge it at maximum amperage during its bulk charging phase (the 50A you mention in one of your posts).
Followup thoughts: If you did drain down your AGM house battery significantly, then the vehicle alternator will never recharge it properly. It was not designed for this application. It was designed to recharge a starter battery that was slightly discharged when you started the motor. To properly recharge a deeply discharged battery you need a charger that will charge the battery in multiple stages: 1) bulk charge stage, 2) absorption stage, 3) float stage, and 4) equalization (de-sulfation) stage. This process will require several hours to fully complete.
Agree the ACR needs to be a bit cleverer. When you get a fully charged battery and then connect in parallel a low battery they will eventually equalise, the alternator will simply see one battery that is low and will charge accordingly.
If I leave my car parked for more than about four days the ACR separates the 'house' battery from the starter, this is parasitic draw from the alarm. I then start the engine from the starter battery, within two minutes or so the batteries are paralleled, they both see a charge, and if your alternator has the available amperage it will recharge both batteries, but the clue was 'if your alternator has the amperage'.
So, you want an ACR that is more savvy and check what amps you have available.
regards
Dave
If I leave my car parked for more than about four days the ACR separates the 'house' battery from the starter, this is parasitic draw from the alarm. I then start the engine from the starter battery, within two minutes or so the batteries are paralleled, they both see a charge, and if your alternator has the available amperage it will recharge both batteries, but the clue was 'if your alternator has the amperage'.
So, you want an ACR that is more savvy and check what amps you have available.
regards
Dave
- Thread starter
- #9
Yes I got that part. That's why I'm using a ProMariner 50A charger, that's no sweat. This is why I don't want a "false" charge on top. That's how I killed my last battery.
The ACR is a Blue Sea SI-ACR, as I understand it when the start battery is up to full it closes and charges the house batt. But all that's gonna do in 10 -15 minutes is screw up my proper overnight recharge.
The alternator is stock.
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My dual battery set-up is based on a Blue Sea SI-ACR too. It works well for my purposes, especially since my 80 is not a daily driver and sits for extended periods between trips. I keep a Battery MINDer charger/desulfator connected during these times and the ACR thus keeps both batteries nicely maintained.
The ProMariner chargers are quality devices and will diagnosis the condition of your house battery as long it's only connected to only one battery at a time. If you just temporarily disable the ACR by pulling the fuse you can connect the charger and let it run overnight. No need to drain down any surface charge. The charger will start out in bulk charge phase and then monitor how many amps the battery wants to accept and from there determine what charge stage is appropriate.
The ProMariner chargers are quality devices and will diagnosis the condition of your house battery as long it's only connected to only one battery at a time. If you just temporarily disable the ACR by pulling the fuse you can connect the charger and let it run overnight. No need to drain down any surface charge. The charger will start out in bulk charge phase and then monitor how many amps the battery wants to accept and from there determine what charge stage is appropriate.
What kills the vast majority of batteries is having them sit around at less than 100% charged. Sulfate then builds up on the lead plates and eventually hardens, killing the battery. The biggest contributor to batteries being undercharged is short trips where the alternator doesn't have time to recharge the energy that was depleted when starting the engine. Plus vehicle alternators (at least those of the vintage we're talking about here) only have constant voltage regulators. These prevent overcharging of a starter battery but will not properly charge a deeply discharged battery. Periodically connecting your ProMariner charger overnight should go a long way in maximizing the life of your batteries.
EDIT: Quality battery chargers like your ProMariner don't get fooled by surface charge. They use a more sophisticated means to determine the charge state of the battery. If you were trying to estimate the charge state of a battery using a multimeter then it would be important to drain the surface charge in order to get a true voltage reading that represents the charge state.
Also, the voltage regulators in an FZJ80 alternator were never designed to charge an AGM battery and so naturally they don't do a good job at it. I don't know the details of your ProMariner charger, but most quality smart chargers let you choose the type of battery you're trying to charge. That's because flooded cell batteries produce a slightly different voltage then AGM batteries and it's important to match the profile the charger uses to the type of battery you have.
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- Thread starter
- #12
The PM charger is awesome. It does let you choose battery type and there's two different programs for each, 14 in all, PLUS you can write your own profile with the "Custom" option.
The 'turn on the headlights before charging' option was suggested to me by an Odyssey tech who also recommended the charger.
The 'turn on the headlights before charging' option was suggested to me by an Odyssey tech who also recommended the charger.
allowing the batteries to equalize by just connecting them in parallel is very hard on the battery. It tries to dump all of its current into the other battery all at once, which is as bad for it as it sounds.
Nothing gets dumped anywhere. The difference in potential between a fully charged battery (12.6v) and a 50% charged battery is around 12.3 volts, so a mere .3 of a volt. If you connect them in parallel, then the higher potential will trickle into the partially discharged battery, this would happen over a period of time but not more than a few minutes. And then no voltage will flow, this means you have two batteries with similar voltages but NOT similar charges, this where the confusion comes from.
If you take the surface charge off the lower charged battery (aforementioned bulbs for example), for a few minutes then the voltage of the lower charged battery will fall very quickly back to the 12.3 seen earlier, and now the true charge is shown.
Now apply 14.4 volts to both batteries simultaneously, BOTH batteries 'see' 14.4 volts but, each battery will take what amperage is available to recharge itself due to it's change in resistance. The first battery which was fully charged will only be accepting a few amps however, the lower charged battery will continue to accept the amperage, until it too is fully charged.
To explain this further.
Take two batteries, both are in good condition but one is fully charged, and one is 50% charged as per the OP 's example. Connect a little home style battery charger capable of supplying say 5 amps. Now connect both batteries in parallel, the home charger can be connected to whatever battery you like. Leave to charge for say 48 hours, and then disconnect and test. They will both be fully charged....period!
And to help you understand this further.
A car and a caravan, the car battery is fully charged, along comes the owner and connects his caravan, the caravan battery at around 50% charge. So does this now mean the car battery is being flattened by the caravan battery, of course not. Owner comes out an hour later starts and drives off.
With the typical 12S socket allowing 'van' battery charging at around a maximum of 10 amp, now we go for a drive. The car battery is fully charged, and the caravan battery is being charged but at a low rate, the car battery is not drawing anything, the alternator supplying vehicle demands and the lowly 10 amps to the caravan. The caravan battery will charge at a very low rate but will be charged assuming the drive is long enough. Experience dictates this 'drive' would need to be about EIGHT hours!
Back to our OP. He does not have loads of hours, so his ACR should be 'in' within a minute or two of starting, this does depend on the brand fitted though. Having loads of amps available is also not the answer though, repeatedly pulling a typical battery down to 50% of charge will shorten it's life considerably. If this is unavoidable then the OP should increase his available amp hours by adding additional batteries, so the load on the batteries is shared.
regards
Dave
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- Thread starter
- #15
Well it is a deep cycle with 125Ah, so pulling it down 20-30% fairly often and 50% occasionally is kind of what it's for. At least from my meager understanding of the subject. I would put another 125Ah or even more in the back of the truck if it would mean significantly longer life, but space is really at a premium now.
Oh btw, It really does sound like pulling 50% out of a battery in just a few minutes would be a bad thing. At least if done often, as you described early on.
Wow this turned into an unexpectedly rousing discussion!
More More..!
Oh btw, It really does sound like pulling 50% out of a battery in just a few minutes would be a bad thing. At least if done often, as you described early on.
Wow this turned into an unexpectedly rousing discussion!
More More..!
What exactly makes you think the current "trickles" from one battery to the other in an unregulated circuit?
What are the max amps your lead acid battery can deliver?
While it will not make it explode, it is definitely very hard on the battery. If the difference in the state of charge is not great, it is not a huge deal. In the camper van example, I would expect your difference in state of charge to be quite significant.
Voltage does not flow, voltage is a measure of potential energy between two points. Electrons flow. Two cells in parallel that are not balanced will flow electronics to the cell with the lower potential. In an unregulated circuit, they will flow at the maximum rate until they are balanced, unless you have something between them to limit current flow. That is why companies sell something called a battery management system for your dual battery setup example.
By the way, I build batteries for a living.
Well it is a deep cycle with 125Ah, so pulling it down 20-30% fairly often and 50% occasionally is kind of what it's for. At least from my meager understanding of the subject. I would put another 125Ah or even more in the back of the truck if it would mean significantly longer life, but space is really at a premium now.
Oh btw, It really does sound like pulling 50% out of a battery in just a few minutes would be a bad thing. At least if done often, as you described early on.
Wow this turned into an unexpectedly rousing discussion!
More More..!
You did not mention a deep cycle battery in the mix, just a 'house battery' although to be fair it does not make much difference, apart from the part where I said you should not be pulling a battery down so far. But again there is an issue, deep cycle batteries are not designed to have a hard load applied to them, ("pulling 50% out of a battery in just a few minutes"), they are more about a trickle drain over a long period.
I run a starter and a 'house' battery but, they are both marine batteries. Having a 'starter' battery and a 'deep cycle' battery as an all in one (as I use) unit means there has to be a compromise. But a good quality marine battery is as good as it gets when using for mixed use, been doing it for more years than I can remember, each pair of batteries lasting around four years.
I would not worry about 'surface charge' when plugging in a decent 'smart' charger in, as per TrickyT said (good post), a decent charger will sort that out.
regards
Dave
First, please confirm that you are not the troll (spelt Tosser), that was on here a few weeks ago and coming up with the same old BS are you? If so my hands high in the air because you have caught me again and I have been well and truly hooked...well done, if not sit back and learn.
Yes you (or Google) may be right about electron flow, but voltage is the potential, it is the 'push' of amps and .3 of a volt is nothing in the whole scheme of things. And the amount of time it takes for the potential to equalise between the batteries is but a few minutes.
And re the caravan battery scenario........nope...Googling....nope no reports of caravans catching fire because one battery was lower in 'potential' than the other, which is what you are implying. If there is one thing I know about it is caravans and the battery wiring. And if the amount of amps flowing was that great then tell me why a 12S socket for the charging circuit should be fused for 10 amps....yep TEN!
My previous post was dumbed down a little for you, but I was also trying to not appear too condescending to the majority of the more knowledgeable people here on MUD.
So apologies for this:
TWO batteries one is at 50% charge @12.3 volts and the other is fully charged at 12.6 volts. I connect a piece of speaker wire to the negative of each battery, and now (God forbid) I connect another piece of speaker wire, to one terminal of the fully charged battery and now complete with furnace gloves a ballistic shield, and a EMT crew at the standby, I am going to connect it to...the.... other....battery....... positive.......(get ready to run).....fsst....er...um.ah......well er...yep I am still here. No dumping of masses of amps, the wires did not melt...but wait, surely this cable is rated at ...er...well it is 1 amp @ 12 volts, but the wire would get hot right, I mean it is merrily 'dumping' away right? Of course it is not!
OK, sorry, condescending attitude off.
I simply have tried this in the past, trying to get two batteries partially charged when one was flat and another fully charged, the potential is so small that it simply does not work...period.
If we take your thoughts a little further and if you still stand by your post, try this:
Again same battery scenario, one full and one 50%, we already know the potential difference is .3 of a volt. The two batteries are separated by a VSR, I am going to use my own VSR setup as an example as I know it works. Start the engine, and the alternator immediately ramps up the voltage to the battery to 14.4 volts, and we are now going to assume that battery is near fully charged. Now we switch in the VSR, remember the potential of the house battery is at 12.3 volts, and all of a sudden it is exposed to not another .3 of a volt but 1.8 volts, that is SIX TIMES the amount that you feel (your words) "is definitely very hard on the battery", and of course it also exposed to the 900 cranking amps my charged battery can offer, AND the 150 amps my alternator can offer, geeez over a thousand amps, I have a potential Nuclear disaster here just waiting to happen!!
No, my batteries last just as long as the next persons, so......I guess that covers that part of your post?
Now to battery management, this is more about charging and/or extending the life of batteries with different technologies gel versus wet plates as an example, some needing particularly higher voltages, or maintaining a battery with 'X' technology with 'bulk' and 'float' charges. They are fairly new technology and were not in mainstream use when the 80 was designed THIRTY years ago, when pretty much every car battery was a wet cell. But if you have batteries of similar technology then they are not needed anyway, I am (or rather my last sets of batteries) and systems are living proof, as per my long running thread here on MUD, oh and throw in 47 years of previous experience, but hey, some are easily led with some good marketing and a pretty box right?
And to your final line of "BTW, I build batteries for a living". It would have been more impressive if you had said "BTW, I design batteries for a living", instead of being someone who just spends all day, repeatedly pressing the buttons on a machine, which was doing the work on a production line.
As usual, I spend a great deal of my time explaining and offering evidence of my findings and where ever possible offer examples as evidence.
All done with this one!
regards
Dave
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Most of the things you are arguing I did not say, so I'm not sure what the point of most of your post is... but it seems like you are coming up with arguments to disprove. I did not state was 50% SOC voltage is. I did not say that anything would catch fire. I did not say anything about a nuclear disaster. I cannot bring myself to read the rest of your post to find out what else you miss quoted, but I feel I have proven my point here.
Battery voltage can be affected by three factors — state of charge, current, and temperature. You keep referencing 12.3V as 50% SOC but it is such an arbitrary measure that you have just further demonstrated that you only have enough knowledge to be dangerous.
Measuring state-of-charge by voltage is simple, but it can be inaccurate because cell materials and temperature affect the voltage. The most blatant error of the voltage-based SoC occurs when disturbing a battery with a charge or discharge. The resulting agitation distorts the voltage and it no longer represents a correct SoC reference. To get accurate readings, the battery needs to rest in the open circuit state for at least four hours; battery manufacturers recommend 24 hours for lead acid. This makes the voltage-based SoC method impractical for a battery in active duty. (The example you gave of your "Test" is exactly what is described in this paragraph as the "most blatant error" of measuring SOC.) Measuring State-of-charge - Battery University
Just so you are aware lead acid 2.1V per cell (a 12v lead acid battery has 6 cells) is 90% SOC, so 12.6V is actually 90% SOC not 100% as you stated.
While you are good at incorporating attitude into your posts, you are helplessly short of facts.
I would consider confirming if your google sources are actually reputable before spreading more of your "information"
Here is some factual information for you:
BU-403: Charging Lead Acid
Learn how to optimize charging conditions to extend service life.
Most battery systems allow reasonably fast charging of one hour or so. The energy can also be withdrawn in about the same time, meaning that the charge and discharge times can be made similar. Lead acid is unique in that the battery can be discharged at a very high rate but requires more than 14 hours to fully charge. Lead acid also needs periodic equalization to de-sulfate the plates and correct other ills.
The lead acid battery uses the constant current constant voltage (CC/CV) charge method. A regulated current raises the terminal voltage until the upper charge voltage limit is reached, at which point the current drops due to saturation. The charge time is 12–16 hours and up to 36–48 hours for large stationary batteries. With higher charge currents and multi-stage charge methods, the charge time can be reduced to 8–10 hours; however, without full topping charge. Lead acid is sluggish and cannot be charged as quickly as other battery systems. (See BU-202: New Lead Acid Systems.)
Lead acid batteries should be charged in three stages, which are [1] constant-current charge, [2] topping charge and [3] float charge. The constant-current charge applies the bulk of the charge and takes up roughly half of the required charge time; the topping charge continues at a lower charge current and provides saturation, and the float charge compensates for the loss caused by self-discharge.
During the constant-current charge, the battery charges to about 70 percent in 5–8 hours; the remaining 30 percent is filled with the slower topping charge that lasts another 7–10 hours. The topping charge is essential for the well-being of the battery and can be compared to a little rest after a good meal. If continually deprived, the battery will eventually lose the ability to accept a full charge and the performance will decrease due to sulfation. The float charge in the third stage maintains the battery at full charge. Figure 1 illustrates these three stages.
Charging Information For Lead Acid Batteries – Battery University