Camper Battery Selection

[brett13]

Its not an AGM battery and the other one is.

And that means...? Is that bad? Unreliable? Unsafe?

 

[pods8]

And that means...? Is that bad? Unreliable? Unsafe?


AGMs (adsorbant glass matt) are sealed batteries that don't vent flamable gas and can thus be mounted inside the camper without venting, non-agms need to be vented out of the camper or mounted outside the camper. AGMs can often be mounted on their sides if desired, non-agms can't. Non-agm batteries require maintenance (keeping the fluid levels topped off so you don't dry out the battery and kill it. Etc.

Both work, one is just more convenient and has fewer mounting location considerations.

 

[brett13]

AGMs (adsorbant glass matt) are sealed batteries that don't vent flamable gas and can thus be mounted inside the camper without venting, non-agms need to be vented out of the camper or mounted outside the camper. AGMs can often be mounted on their sides if desired, non-agms can't. Non-agm batteries require maintenance (keeping the fluid levels topped off so you don't dry out the battery and kill it. Etc.

Both work, one is just more convenient and has fewer mounting location considerations.

Aha. Must scratch that one off the list. Any others? Thx.

 

[pods8]

Aha. Must scratch that one off the list. Any others? Thx.


Any others what? Battery recommendations? If so my suggestion is see if a local battery retailer is having any closeouts like I suggested before.

By the way here is a good reference read on batteries if you want to know more: http://www.windsun.com/Batteries/Battery_FAQ.htm

 

[Barko1]

The Sam's 6v batteries are 170 ah for $72.

 

[brett13]

Any others what? Battery recommendations? If so my suggestion is see if a local battery retailer is having any closeouts like I suggested before.
I meant any others on that list that aren't AGM, so I/we can avoid wasting out time.

By the way here is a good reference read on batteries if you want to know more: http://www.windsun.com/Batteries/Battery_FAQ.htm

Thanks

 

[brett13]

The Sam's 6v batteries are 170 ah for $72.

So, you'd just wire two of these in series and end up with 12v and 170AH? Pretty slick idea.

 

[pods8]

I meant any others on that list that aren't AGM, so I/we can avoid wasting out time.


Chances are any batteries (that aren't on sale) that are in the $50-100 range are normal flooded cell batteries. $180+ and you'll start seeing the AGMs.

So, you'd just wire two of these in series and end up with 12v and 170AH? Pretty slick idea.


Yes when in series voltage is additive and capacity stays the same, when in parallel capacity is additive and voltage stays the same.

Those are going to be flooded cell batteries FYI.

 

[Tris]

You might want to check the charging characteristics of your inverter/charger before relying on it with a new battery. In my limited experience, they are not very well suited to charging and shorten battery life. Not much point in buying a great battery and then trashing it with a cheap charger. I've been able to get charging specs for my battery from the manufacturer's customer service folks. Then use a digital volt meter to see what your converting is doing. If they match, then your're lucky. It pays to check the output from your alternator charging circuit too. Sometimes the wires are too small and/or too long and you get an unacceptable voltage drop. In other words, you may need to buy a real charger too. Good luck.

Tris

 

[pods8]

You might want to check the charging characteristics of your inverter/charger before relying on it with a new battery. In my limited experience, they are not very well suited to charging and shorten battery life. Not much point in buying a great battery and then trashing it with a cheap charger. I've been able to get charging specs for my battery from the manufacturer's customer service folks. Then use a digital volt meter to see what your converting is doing. If they match, then your're lucky. It pays to check the output from your alternator charging circuit too. Sometimes the wires are too small and/or too long and you get an unacceptable voltage drop. In other words, you may need to buy a real charger too. Good luck.

Tris


I've advocated the same and fully agree.

 

[rock and roll]

You might want to check the charging characteristics of your inverter/charger before relying on it with a new battery. In my limited experience, they are not very well suited to charging and shorten battery life. Not much point in buying a great battery and then trashing it with a cheap charger. I've been able to get charging specs for my battery from the manufacturer's customer service folks. Then use a digital volt meter to see what your converting is doing. If they match, then your're lucky. It pays to check the output from your alternator charging circuit too. Sometimes the wires are too small and/or too long and you get an unacceptable voltage drop. In other words, you may need to buy a real charger too. Good luck.

Tris


Tris and Pods: thank you for your input. I don't anticipate using the converter/charger to be charging the battery often due to the nature of our trip (continuous driving to South America as opposed to weekend outings followed by weekly garaging). I posted my idea for wiring in another forum, perhaps you could let me know if this would be sufficient in your opinion? I can't readily check the actual charging characteristics of this set-up because it hasn't been built.

http://www.expeditionportal.com/forum/showthread.php?t=50205

 

[pods8]

Tris and Pods: thank you for your input. I don't anticipate using the converter/charger to be charging the battery often due to the nature of our trip (continuous driving to South America as opposed to weekend outings followed by weekly garaging). I posted my idea for wiring in another forum, perhaps you could let me know if this would be sufficient in your opinion? I can't readily check the actual charging characteristics of this set-up because it hasn't been built.

http://www.expeditionportal.com/forum/showthread.php?t=50205


I'm not a fan of charging AGMs off a basic alt output personally. Usually its too low for the bulk charge phase and too high for float charging. Others put less value on it though.

I run a 7.5amp DC/DC charge that does a charge profile from a 10-15VDC input thus it makes up for line losses as well (I can look up the numbers later if you care) that is more inline with what my batteries like. I do not use a separator as the charger has a remote input that I've tied into an ignition hot line thus it cuts out when the truck is off. Some folks might find the 7.5amps limiting but my battery bank is 210amp hours so I have quite a buffer to sit a while and then I'm usually driving a decent amount when I do move so I've never really had issues yet on my weekend warrior schedule.

 

[rock and roll]

I run a 7.5amp DC/DC charge that does a charge profile from a 10-15VDC input thus it makes up for line losses as well (I can look up the numbers later if you care) that is more inline with what my batteries like. I do not use a separator as the charger has a remote input that I've tied into an ignition hot line thus it cuts out when the truck is off. Some folks might find the 7.5amps limiting but my battery bank is 210amp hours so I have quite a buffer to sit a while and then I'm usually driving a decent amount when I do move so I've never really had issues yet on my weekend warrior schedule.


Thanks for the info Pods. I'm new to these sorts of things and open to the best option. Could you expand on this or point me to a write-up? Specifically what product do you wire in that allows you get get a 7.5amp DC/DC charge? I'm assuming this is not powered from the 7pin connector 12v feed wire.

 

[pods8]

Thanks for the info Pods. I'm new to these sorts of things and open to the best option. Could you expand on this or point me to a write-up? Specifically what product do you wire in that allows you get get a 7.5amp DC/DC charge? I'm assuming this is not powered from the 7pin connector 12v feed wire.


I'm running a powerstream http://www.powerstream.com/DC-input-chargers.htm PST-BC1212-15 charger, as mentioned the 7.5amps might be smaller than what some would desire but it works for me. Actually something like this would likely work well off the 7pin since its not a huge amp draw and it'll correct the voltage if there are any line losses. Edit: In your diagram linked above the charger would swap into the place the battery separator that is shown, you do not need a separator with it, its meant to only draw power on one side and output it on the other.

Looking at my notes it bulk charges at 13.7V, over charges at 14.4V and floats at 13.2V. Happened to be a good fit for the battery charge profile mine wanted.

Edit 2: By the way a battery "separator" wouldn't do anything in your sketch, a separator goes between the alt. and the batteries so each battery gets their own feed and can't go back and forth to each other. The 7pin would see your truck battery (but is likely ignition hot only via a relay, if so its already been isolated).

 

[rock and roll]

I'm running a powerstream http://www.powerstream.com/DC-input-chargers.htm PST-BC1212-15 charger, as mentioned the 7.5amps might be smaller than what some would desire but it works for me. Actually something like this would likely work well off the 7pin since its not a huge amp draw and it'll correct the voltage if there are any line losses. Edit: In your diagram linked above the charger would swap into the place the battery separator that is shown, you do not need a separator with it, its meant to only draw power on one side and output it on the other.

Looking at my notes it bulk charges at 13.7V, over charges at 14.4V and floats at 13.2V. Happened to be a good fit for the battery charge profile mine wanted.


Thanks again pods. You are a great wealth of knowledge. Seems like your setup using the 7.5amp charger is the way to go, but I just can't find much on it, doesn't appear to be the popular route. But, think I will scrap the separator idea. The only issue is at 7.5amps, it would take 14 hours to fully charge my 100 amp hour AGM battery (hopefully I'd never fully charge). I can't find anything in in the 15amp range? I've read you can get 30amps (25 after the losses from the distance) from your 7 pin.

Let me also ask you: I have also read that you can wire your camper battery directly to the 12v 7 pin feed wire (with a separator or isolator to be safe). The advantage of this would be the full 25 amps to charge the battery, the disadvantage would be loosing the 4 stage charging offered by the 7.5amp charger, correct?

 

[pods8]

Thanks again pods. You are a great wealth of knowledge. Seems like your setup using the 7.5amp charger is the way to go, but I just can't find much on it, doesn't appear to be the popular route. But, think I will scrap the separator idea. The only issue is at 7.5amps, it would take 14 hours to fully charge my 100 amp hour AGM battery (hopefully I'd never fully charge). I can't find anything in in the 15amp range? I've read you can get 30amps (25 after the losses from the distance) from your 7 pin.

Let me also ask you: I have also read that you can wire your camper battery directly to the 12v 7 pin feed wire (with a separator or isolator to be safe). The advantage of this would be the full 25 amps to charge the battery, the disadvantage would be loosing the 4 stage charging offered by the 7.5amp charger, correct?


I think something like this isn't as popular because folks don't care or don't want to think about proper DC-DC charging (plus many go over to solar which does have voltage regulation available, stage charging & voltage conversion is what you are paying for in the more expensive models). Or some also just accept (or don't realize) they might get premature battery failure, however most are happy when they have a couple years in that they don't realized they could have had a couple more. If I was running flooded cells I likely wouldn't bother with it either because even if the alternator floats the batteries too high/too long you can just top off the fluid levels. Can't do that with AGMs. The other option would be to be able to monitor & shut off the charge going to the batteries when they get full.

One would hope you don't drain down your battery completely. Some options if you did want to pursue something like this though and did drain your battery all the way:

A ) For starters since you are using a 7pin you could wire up two pigtails (the connector you plug in) with one going to the charger (this would be your normal one that you plug in) and another going directly to the battery and bypassing the charger (plug this one in when you need more juice for a while, assuming your 7pin actually provides what you are looking for, and then swap them back later when the batteries just need to be topped of and float charged).
B ) They used to have a switch on that charger to click it over to 15amps but stopped doing that, not sure if it could be modified still.
C ) Promarinier makes a 40amp DC-DC charger but it runs over $400 if I recall.
D ) In a pinch if you were really looking to dump some charge in quickly to a dead battery in a short period of the truck running but not driving you could always use jumper cables from the alternator which would handle the charge.

As long as your 7pin power line is ignition hot only (ie only has power when the truck is on) then it already has a relay on it and there is no need for an isolator as well. I'm assuming you're 7pin power line is around 10ga, if not then you should likely upgrade it for the sure you want to do. Yes you can connect directly to it and yes you'll get whatever voltage comes out the other side (that will likely vary some depending on how much current is flowing at the time as well).

 

[rock and roll]

Cannot thank you enough pods8. I plan on running some tests and going with your approach #1 if I'm getting the amps off the 7 pin that I expect (10-20amps). I will keep everybody updated in a separate post for others who are looking to charge from the truck.

 

[rock and roll]

pods8 (or anybody, but pods seems to be the resident expert): What is the difference in the 7.5amp DC/DC charger and a controller (voltage regulator) used in solar applications?

Using this as an example (Morningstar SunSavere Controller): http://www.morningstarcorp.com/en/support/library/SSMPPT.IOM.EN.02.pdf

I could wire my 12V DC 7 pin feed wire into solar input of a controller and get voltage regulated, staged charging without amperage restrictions as with the 7.5amp charger. Would this work or is there something unique to the solar panel input that it wouldn't accept my 10-15 amp charge at 12-14 volts?

Not only would this approach get more amps to your camper battery while driving down the road, but would make solar integration an easy next step? I must be missing something otherwise everybody would be wiring their 7pin into a solar setup.

 

[pods8]

I had the same exact thought when I was in your shoes, I talked to the manufacturer and its a no go (can't exactly recall what the issue was in my early morning mind right now).

But I invite you to give the manufacturers tech support a call the double check the issue as sometimes the default answer to an application something wasn't originally designed for is "no that won't work" without really considering it. It would be nice if it did function in that manner and I know I'd personally just opt for something like that on future projects and feed either alt output or solar into it to always get proper charging.

 

[rock and roll]

Thanks again Pods.

I talked to Tech Support at Morningstar and it appears the alternator voltage is to low to work with the controller.

"The 13.5V supply from the alternator is too low of an input voltage for any of our controllers to regulate because they use 14V-15V Bulk regulation set points."