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Discussion Starter #1
Does anyone know how the voltage regulator and alternator works on these rigs?
Are they essentially a voltage source, at about 14.5, until they reach the current limit, then the voltage drops? I'd go take some measurements, but of course my van is in the shop :crying::mad:
Or do they have some battery charging smarts or circuit such that the voltage drops when the load drops so the battery is not overcharged?
I'm wondering what it will do when connected to an auxiliary battery. A lot of current would be nice for bulk charging an AGM, but I don't want to overload the alternator. The diesel alternator is 220 amps, so I would think 100 amps for an hour or so would be fine.
 

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Hi,
I'd also be careful about how fast you charge the house battery. I have two 200 amp-hr 6 volt golf cart batteries in series for a house battery, and the maximum charge rate to keep the batteries from being damaged is 30 amps.
I have a 50 amp breaker in series with the the line from the van alternator/battery, and it has never tripped, so I guess the alternator is set up to charge at moderate rates.

Gary
 

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Discussion Starter #3
Thats the big advantage of AGM, they can take a huge charge rate, more than the alternator can put out. At least that's the case for lifeline and concorde (sun xtender).
Due to the low impedance design, Sun Xtender® batteries
can tolerate in-rush current levels as high as 5C (500A for a 100Ah battery).
 

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I'm looking at a this type of setup too, and I'm trying to wade through all the info that is out there. I want to stay as simple as possible (like GaryBIS), but I do want to run AGM batteries. I was looking at the Concorde lifeline's but I'm worried about charging the AGMs from my PMs 220A alternator.

Do you need a DC-DC charger to regulate the voltage to get a full charge? Will low internal resistance of the lifeline AGMs end up overloading the alternator? I don't have the van yet, but am trying to do as much planning as possible before I get it. I'm curious as to how the voltage is regulated from this alternator. If it can put out enough volts to properly charge the AGMs, but essentially float them when charged, that would be great!

Bear with me if me understanding isn't the best. I'm doing my best to learn this stuff as it will be my first camper conversion!
 

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Discussion Starter #5
I'm looking at a this type of setup too, and I'm trying to wade through all the info that is out there. I want to stay as simple as possible (like GaryBIS), but I do want to run AGM batteries. I was looking at the Concorde lifeline's but I'm worried about charging the AGMs from my PMs 220A alternator.

Do you need a DC-DC charger to regulate the voltage to get a full charge?
That would be the best way, but they are expensive.
Will low internal resistance of the lifeline AGMs end up overloading the alternator?
I don't think so, they have to be deeply discharged to draw a lot of current.
I don't have the van yet, but am trying to do as much planning as possible before I get it. I'm curious as to how the voltage is regulated from this alternator. If it can put out enough volts to properly charge the AGMs, but essentially float them when charged, that would be great!
In my experience it did not put out enough volts, and it took a really long time to charge, also it seemed to loose capacity after a trip with only alternator charging. The van only puts out about 14.1V. Considering voltage drop in the cable, you'll often get less than 14V. Lifeline recommends 14.3 at 77F, that's close, but if your camping in comfortable weather the battery might be closer to 60F, so you need 14.6V. With adequate solar panels and sun it would probably be fine. If the battery was deeply discharged you could get a bulk charge from the van, then get the recommended voltage from solar panels to complete the charge. I have a 4+ cuft fridge and a folding 100W panel & with good sun it will keep up.
Bear with me if me understanding isn't the best. I'm doing my best to learn this stuff as it will be my first camper conversion!
It seems like a lot of people have used flooded lead-acid batteries and have had good results charging straight from a van, but I think AGM batteries (at least Lifelines) are more finicky
For some discussion of my experience and solution, look here.
http://www.promasterforum.com/forum/showthread.php?t=43089
I caught a lot of flak for it but it works better than direct from the van system.
 

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I have used Deka AGM batteries charged through a voltage controlled relay (Blue Sea ACR) directly from the van's system on a Sprinter and now a Promaster. I have never had any problems with this set-up. 14.1 volts will fully charge the AGM if you do enough driving. With my current van I have a 230 amp hour AGM and when it is down halfway to 12.2 volts it gets fully recharged after just a couple of hours driving.
 

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Discussion Starter #7
How long did you Deka's last?
With you current van what method are you using to know that it is fully recharged?
 

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From papab:
"It seems like a lot of people have used flooded lead-acid batteries and have had good results charging straight from a van, but I think AGM batteries (at least Lifelines) are more finicky."

Due to the issues listed above I installed two golf cart 6 volt FLA batteries in series. Their lifetime is reputed to be longer than AGM, they are much less expensive, the van's alternator can charge them as is, and my interconnect is 50 amps and has not blown. My 200watts of solar does 99% of the charging anyway. They must be vented but I now read posts that say AGMs should be vented too. I am very happy with them and I don't understand why I would have been better off with AGM? Consider FLA.
 

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rd,

It's a tough call, but in my experience, I have used AGMs for in-my-house use at my ham radio setup for years. No venting required, even in the house.

If they were extremely overcharged, I guess that they could emit some gasses, but not under any circumstances I have ever heard about.

Good write-up : http://roadslesstraveled.us/wet-cell-vs-agm-batteries-rv-installation-wiring-tips/

I have an AGM now, might add another one. On the other hand, I like the lower cost of the FLA's. On the other hand, then I'd have to make a hole in the van for a vent.

Snowing in CT - bigtime... snow probably won't make it up to NH, definitely not happening in AZ!

Ed
 

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Question is how long do the Dekas last. My Sprinter I had for three years and they were fine when it was sold. My present Promaster is only a year old. A better measure is my previous live aboard trawler boat. On that boat they were installed about 15 years ago and were in full time use for 4 years when I sold the boat to a friend who uses the boat only part time but they are still going strong! Interestingly the alternator on that boat has a dumb regulator set at 14.1 and when running the boat the batteries float at that voltage for hours at a time and are not damaged by any over charging. The shore power charger is the original 1988 ferro resonant unit (just a big transformer and rectifier) that is dumb. I once left the boat for two weeks for surgery and forgot to turn off the charger. When I returned they were happy sitting at 14.1 and no damage was done. Internal resistance of the fully charged battery had reduced the current flow from the ferro resonant charger to about 1 amp as shown on the boat's meter and that represented battery leakage current. I think 3-stage smart chargers are over hyped.

How do I know if they are fully charged. I figure this by the discharge as follows. My single house AGM is a size 8D of 230 amp hours. I do lot of stealth camping. After driving just a couple of hours they are fully charged and have a resting voltage of about 12.8 after running light loads (such as LED lights) to burn off the "surface charge". I then run my 750 watt water heater off the inverter and it typically takes 45 minutes to heat the water before before the heater thermostat shuts off. The inverter shows a draw of 80 amps during this process which is about 60 amp hours out of the battery. During this process the voltage under the 80 amp load drops to only about 12.0 not he expected 11.8. After letting the battery rest just 3 minutes it pops back up to 12.4 or 12.5. If you run some numbers assuming that 12.2 would be half discharged indications are that the battery was fully charged. I have also done other tests of measuring discharge loads.

Two points. Deka batteries made by East Penn are expensive. "You get what you pay for." Secondly, I have only once ever seen evidence of venting by a Sealed Valve Regulated battery. About 25 ago an original set of batteries on my boat mentioned above vented some at one cell. A small stain around the cap over one of the pressure release valves indicated that some tiny amount of electrolyte, perhaps a teaspoon full, had been forced by gas pressure. That original battery continued to operate OK but soon after I replaced it.
 

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Batteries don't 'die' they are murdered.

With the PM having AGM's from the factory the alternator voltage will be limited to keep from damaging their OEM battery, instead of 14.7V or above a FLA cell requires it may be limited to 14.1 or 14.2...

The 'bad deal' with AGM & Gel batteries is bubbles forming on plates that can/will not move from the spot they form at, and so, being trapped there make a permanent 'scar' and reduce capacity.

Temperature compensated charging & common sense will see us get battery lifetimes well beyond the warranty period. An example - I have a set of used 102lb 110AH 12V AGMs that are 10-year batteries; these came out of a cell phone tower where they saw float duty as back ups. The OEM data provided was extensive, these would be the flavor of batteries they put in areas that takes snow machines or helicopters to service the repeater or cell stations. Take as gospel their statement 'ANY (even compensated reduced voltage) charging with internal temperature over 106°F will result in internal damage'.

Another point to note on these hybrid cells, the partially gelled electrolyte and fiberglass matting with valve-regulated venting, is they like a high surge current when recharging that forces the electrolyte to convect by providing strong enough thermal pulses that the 'surplus' fluids above/below the plates gets pushed into service.

Anyhow, keeping batteries cool - no batteries touching each other, battery box floor with some airflow underneath it, no stale airspace that allows temperatures to keep creeping up; and batteries shielded from sun-heating will improve our odds they will last the through the warranty period. Adding temperature compensated charging will keep the batteries useful through cool/cold weather and likely help once internal battery temperatures creep up into the 80's or 90's AND you simply have to charge to prepare for the next discharge cycles...
 

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Great information. I won't relate much of my experience with FLAs in my off grid home years ago but their lifetime seemed like 15 years as they were still working fine when I sold them. Controlled conditions so no murder= long life. I read the above to mean our batteries are AGM? I guess when I looked at mine to hook up the FLAs for the coach batteries I missed that. 2015 Diesel. I might have done AGMs if I had realized! Now I wonder.
Here it is: It has a vent tube on the end, has fume warnings etc. so I assumed FLA but it says AGM!. Who knew!?

Fluid vent in circle:
 

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Discussion Starter #13
Maybe I should of bought a Deka. My 150ah lifeline was not cheap but it takes a long time to charge up. I can get to 90% state of charge pretty quickly, but the last 10% takes a long time, at least 4 hrs. That's at the recommended voltage (14.3 + temp compensation), it takes longer at 14.1. I'm basing this off my trimetric battery monitor, and the lifeline recommendation for full charge when the current drops to 0.5% (0.75 amps) with the recommended voltage . A typical trip for me doesn't include a long drive every day. I've noticed that if I don't get it to a full charge for a few days it charges up slower and slower, making it take even longer to get to 100%, and it just gets worse.

I talked to lifeline tech support twice, after 2 trips, where I wasn't getting to full charge very often and described the symptoms and they said the battery was sulphated, they said I needed to do a conditioning/equalizing charge and charge up every day. If I couldn't get to a full charge every day the battery will only last about 3 yrs, instead of the 5+ that I should get. Since then I've had some good sunny trips so I can keep the battery happy with the solar. If I do a trip like my last trip to BC I'll have to plug in once in a while.

Here's a good write up on the partial state of charge issue. He likes lifelines because they can be equalized.
http://forums.sailboatowners.com/index.php?threads/agm-batteries-making-the-choice.124973/

Here's something from lifeline (I think it's fairly old):
http://www.kp44.org/LifelineBatteryLetter__JustinGodber.php
I found some other fairly old quotes on sailboat forums or blogs from JG and asked him via email he still stood by those statements and he didn't respond.

On the venting question, they don't need to be vented to the outside, but they shouldn't be in an airtight box.
 

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In either case, AGM or FLA, what is regulating the charging amp draw? I understand that the batteries have a recommended charge amperage. In my case with a gas engine, but 220 amp alternator, how can I calculate (and regulate) what the battery will actually draw. It sounds to me like charge rate is going to be the biggest issue. The alternator shouldn't overcharge the batteries, although it may undercharge them. I am ok with this as I will be using solar to give a complete charge. My other concern is that I have proper wire gauge, solenoid rating, and fuses/breakers, for whatever the maximum amp draw could be from the battery.

I'm still trying to decide between AGM or FLA. I'd really like to do AGM just so I don't have to worry about venting, mess, and maintenance, but if it makes things much easier from a charging perspective, I could go with FLA.
 

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I have a pair of 6 volt golf cart FLA batteries from Sam's Club which are 20 amp hour rate is 215. I have 200 watts of solar and an MPPT controller which I can set for FLA (or AGM). In good sun the batteries are at float in about 3- 1/2 hours after a night running the fridge, lights, radio, computers, fan, and whatever else. I almost NEVER need the van to charge the batteries so I have a switch on the interconnect to the van and keep it off unless I need the van's power to charge. That way the MPPT controller will do a good job at properly charging the batteries. For equalization or de-sulfation I will use a charger specific for the task which I keep at home. Perhaps the charging from the van is less important than you think. For me it is a non issue. BTW the FLAs are clean, dry, vented, no maintenance, no corrosion, and fine after 6 months.
 

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A question was raised above concerning calculating the charge current. The charge current depends on the voltage applied and the internal resistance of the battery as it fills up. All batteries have increasing internal resistance as they fill up and the current will taper off. I think that only battery manufacturers can answer the question accurately. In theory I believe that flooded batteries have slightly lower internal resistance and thus they should charge a bit faster.

A question often comes up as to how a charger decides to drop to a lower float voltage. For most chargers I believe this is simply based on time. After all, the charger cannot base the decision to drop to float based on current going into the battery because the charger does not know if it is connected to a tiny battery or a very large battery bank. If you feel that the charger has dropped to float prematurely you can turn it off and them back on causing the time function to reset. Batteries are usually fully charged if the resting voltage is 12.8 or higher after surface charge has been burned off by a light load for a while. Since most chargers float at around 13.3 a battery will become fully charged at this voltage if given enough time.
 

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Thanks guys,

RDinNHandAZ, it sounds like I am shooting for a very similar setup. I'd like to have the option to charge from the alternator when needed, but I think solar should take care of the majority of our needs.

So, if we are uncertain of how many amps the batteries are drawing, how are people sizing the cables and fuses from van -> isolator -> house bank? Is there a general rule of thumb that you can go off of?
 

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I fused the interconnect between the van battery and the coach battery at 50 amps and it hasn't blown but I have an 80 amp replacement fuse JIC. So that wire needs to carry 80 amps, really 100 to keep the losses small. For short runs #4AGW wire is large enough but "2 ought (2/0)" multi-stranded is not much more cost as it is not a log run so consider that, it is larger so it is a bit harder to manipulate but should not a be a problem. Get good crimp and solder terminal lugs and both crimp and solder them. I used the chassis ground for the negative side so only a red + was purchased. My "mains" are fused at 80 amps to the distribution box so more #4AGW , and the chassis ground again, My 1500 watt inverter came with a couple of "2/0" cables so I used them. My solar panels carry about 10 amps so I used #10AGW wire spec'ed with MC-4 connectors. See my build for more info. See:http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm All this from a feeble memory. Best to you.
 

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I fused the interconnect between the van battery and the coach battery at 50 amps and it hasn't blown but I have an 80 amp replacement fuse JIC. So that wire needs to carry 80 amps, really 100 to keep the losses small. For short runs #4AGW wire is large enough but "2 ought (2/0)" multi-stranded is not much more cost as it is not a log run so consider that, it is larger so it is a bit harder to manipulate but should not a be a problem. Get good crimp and solder terminal lugs and both crimp and solder them. I used the chassis ground for the negative side so only a red + was purchased. My "mains" are fused at 80 amps to the distribution box so more #4AGW , and the chassis ground again, My 1500 watt inverter came with a couple of "2/0" cables so I used them. My solar panels carry about 10 amps so I used #10AGW wire spec'ed with MC-4 connectors. See my build for more info. See:http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm All this from a feeble memory. Best to you.
That is extremely helpful. Thank you, and I look forward to checking out your build!
 

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Discussion Starter #20
It depends on what type and size of battery you have. I never found any good rules of thumb or ways to calculate it so it's kind of a guess. I went with a 1/0 cable from battery to battery, and a 100 amp fuse. When my 150 ah atm battery was fairly low, ~30 or 40%, I saw a brief 100 amp inrush, and >50 amps quite a bit. If you have a flooded lead acid like RD, 50 is probably OK because they don't draw as much current as an AGM .
 
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