summer breeze

Such as a large hole in the bottom of one of the batteries? I have been taking the batteries out and testing their capacity and one of them has a good sized hole in the bottom. The open circuit voltage on this battery dropped pretty fast once disconnected from the bank. All the rest of the batteries held 13.06v for several days. The odd thing was the plastic was pushed in like the battery was dropped on a rock. It had to have been this way since first installed because the batteries have never been removed. I am curious what effect this had on the bank. Just reduced capacity? or something worse? Interesting, will give this some thought - thanks!

I spent some time with Charlie (Sterling) on the phone and he was as perplexed for a solution as the rest of us. Basically, Gibbo was correct when he said that the A-B-C unit would draw the voltage down as well and would not provide a solution. This leaves the following two solutions; 1. Isolate the battery bank after they are fully charged. This must be done manually as there is nothing on the market to accomplish this. 2. Connect an inverter to the alternator and provide AC power to the shore power charging system and give it exclusive rights to charge the batteries. I was really hoping someone knew of a programmable controller that would open a switch when the amps were X and the volts were Y. Thanks to everyone for spending time with me on this and if someone has an idea, please do not be bashful... I am a bit surprised they have lasted this long. There have been two events that left them undercharged for several days and then with the alternator at a constant 14.4 they were over charged the remainder of the time. I have pulled one of them from the fully charged (by shore power) bank and am running a capacity test...

Hey Pete, this vehicle has actually been in service for over 3 years with the Lifeline batteries hooked up directly to the 14.4 source. They have done pretty well all things considered. We will be replacing them because their capacity has been reduced and we would like the next set to fair better. As mentioned in a previous comment, the cabin AC unit is 110 volts and is powered by the inverter. A very good idea (I like simple) but not possible for us...

We do have a large inverter that will charge the batteries while on shore power. The cabin AC unit is 110 volts (alternating current) and is powered by the inverter when not connected to shore power. I have given thought to a second inverter hooked directly to the alternator to provide power to the house inverter/charger while the engine is running. It's not on the top of my list but I haven't scratched it from my list...

Hey Tony, something to consider but something I would like to keep in the last resort pile until we have exhausted all ideas with working with a 14.x output. At first glance the Alternator to Battery Charger from Sterling appears to be a device that we could place down stream from the alternator but Gibbo's comment leads me to believe it might not be. I will give them a call and make sure they are not fiddling with the output of the alternator. I appreciate your thoughts...

Hey Steve, a reasonable explanation. There is a very large gap between engineering and service here in the US. Changing the threshold is a good idea but my dealing with Freightliner leads me to believe the request would be rejected. Also, the AC unit was the only thing that showed itself during the low voltage condition. There could be other pieces that are equally sensitive but go unnoticed. I talked with the battery folks about this and found it interesting that they would prefer the charger to be shut off when the charging was completed. The float stage to them is simply to compensate for self discharge which would amount to next to nothing in our situation since the equipment is in frequent use. The house bank's purpose is to provide power when the engine is off. Why not just take the bank offline when it is fully charged and then put it online when the engine is off. The alternator can handle all of the loads while the engine is on...

My original post was about what would happen to the batteries if I stayed in absorb and could not switch to float. I did not really want to spend time on the Freightliner side of things. I am grateful for the answer which was that with the amount of time a day spent charging it could damage the batteries. However, I am not any further down the solution road other than knowing I must somehow reduce (or eliminate) the voltage once the batteries are charged but keep the alternator output at 14.x. I am not a commercial enterprise. I am a guy with a single vehicle who is much like you only I am forced to travel the roadways instead of the water ways (at least for now). If you decide to revisit this topic I have a few ideas I would like run past you.

Okay, I finally figured out the disconnect in our thoughts. The AC unit I am referring to is the cockpit AC system. It is only usable why the engine is running because the engine powers the compressor. When the engine is off the cabin AC unit (different unit) runs off the house bank. The engine, power train and chassis all belong to Freightliner. The cabin belongs to us. Also, this is a very modern 2010 piece of equipment and and there are times when I use similar terms to describe it but I assure you it is very sophisticated piece of equipment (why I stay clear)...

Tony, close. This is a class 8 vehicle that has been stretched into an RV. Unlike the normal body builders, we have elected to keep our systems separate as we have no need to access to their interface. We have however, increased the storage and charging system. We installed a high output alternator and the conductors (4/0) from the alternator to their common buss. We increased the conductors from their buss to their battery bank (also 4/0). Our point of demark is connecting our common buss with theirs (also 4/0). Everything works great as long as the voltage stays between 13.8 and 14.x which is all the time. If we have sit for awhile and drawn the voltage down below 13.8 then there is a brief period of time where the Ac does not work correctly but with the EcoTech that period is very brief...

Lets say that you are correct. I am still stuck in a no win situation. Let me tell you how I discovered this problem. The EcoTech failed and I was forced to put the undersized factory alternator (36SI) back in place. It did not have the amps to charge the bank so we were stuck in bulk for a very long time. It was summer so we had the AC on but it would not blow cold air. We took it to the shop and the tech explained that the system had taken the AC unit off line because of the low voltage (I think we were in the mid 13.x). The tech said the voltage needs to be between 13.8 and 14.x. I had just picked up the EcoTech replacement so I swapped it out. We pushed through the bulk stage and when the voltage passed 13.8 the cool air blew through the vents and the tech said I was good to go. Bottom line is I am not going to get any help from Freightliner as they expect the voltage to always be between 13.8-14.x and as long as it is everything work correctly. The wiring to the AC unit goes through their buss and everything is computer controlled (multiplexed even). I cannot make a change to their system as it is too delicate as it is. I am asking for help and am telling you my solution must not include dropping the alternator output below 13.8. My thought was that if anyone could help it was the folks in this forum. I apologize for not wanting to spend time on this part of the problem because it is a dead horse that I have already worn my self thin on...

I apologize and do recognize the value of Gibbo's knowledge as that is why I am here. I have spent a great deal of time researching the available resources. This forum has the most respectable representation. The AC problem belongs to Freightliner and we have been very careful to keep our world separate from theirs. The stock alternator behaves the same way and the EcoTech is the ONLY thing we have changed in their world. If we add a float this will change their world and I cannot go there. Their electronics are very sensitive.

I know it seems odd but the only changes made to the stock chassis is the cable between the alternator and chassis fuse panel has been doubled in size. The low voltage effect on the AC unit is well known to the folks that work on it. I don't have an answer for you other that that is the way it was designed. I cannot drop to float. Is my only off the shelf solution the Alternator to Battery Charger from Sterling? I would prefer to just isolate the battery bank when the amp draw was .5C to the batteries but I can't locate a product that will do this. I don't need the batteries while the vehicle is running. We have a common buss that peer the load, source and battery bank and we don't have a load that would exceed the alternator output even at idle. Could we just put a shunt in the negative lead and a solenoid in the positive lead and when the amps to the batteries dropped < 5 amps (in my case) and the voltage at the batteries was > 13.8 just open the solenoid? and if either of the criteria changed, just close the solenoid? this seems much simpler than turning everything over to the Sterling unit...

I have spent a great deal of time browsing these forums and you over estimate the suppliers. And I believe the suppliers to my solution might be represented here...

Sorry, you are correct, the air conditioner goes off line. There could be other systems that go off line as well but they may go unnoticed as they do not keep me comfortable on a hot summer day...

The vehicle is working as designed. When the voltage drops the AC goes offline until the voltage rises. The logs report a low voltage condition. This is the only system that I am aware of that goes offline but it is enough for me to keep the voltage where the stock alternators put it @14.4. Can we move on? we can't step it down to a float voltage...

The on board electronics require 14.x volts and things such as the AC unit will not work if the voltage is too low. The vehicle is a class 8 chassis (Freightliner)...

I have a high output alternator with remote voltage sense (Eco-Tech). I have a single large bank (10x12v) of AGM batteries (Lifeline GPL-31T). The vehicle operates 12-14 hours a day (sometimes 24). The bulk and absorb stage works as expected. My question is do we need to float the voltage down to 13.x? The problem with floating the alternator is the vehicle will not operate properly at 13.x and expects 14.x. If we don't float the voltage down what happens to the capacity of the batteries?