AGM charge rate

[buswarrior]

Settle down.

No insult was intended.

The last thread should have started with, "windtrader, you've read..."

The discussion is about all of us, existing and intending busnuts.

It ain't easy being a busnut.

Happy coaching!
Buswarrior

[Branderson]

Fair enough...

I'm just having a heck of a day dealing with metrics and corporate today.  Ironically, it's taking a lot of self discipline to not tell corporate to shove it!

[neoneddy]

As the proud new owner of an AGM bank this topic interested me.  I eventually found some spec sheets saying same for charging voltages 14.4-14.8v 13.6 float.

As far as keeping things charged, solar , I'd think even 300-400 watts would do fine.   Right now I've got my 2000 watts keeping my electric water heater   on as well as the fridge and other stuff while the bus sits in the driveway.  I was down to 80% soc over night, should be up to

Here is the bank if anyone is interested.

https://www.youtube.com/watch?v=PZCPSNnoDns

[Jim Blackwood]

Used to be that the military used a lot of checklists, I doubt that has changed. We'd have a checklist for going to the john, I swear. OK so that's overdoing it but the point is valid, for those more important things (like making sure the batteries don't get drained unnecessarily) a checklist is still useful. If you make up a medium sized card, laminate it, put it on a string or chain so it can't wander, and then put it in a prominent place then you only have to make a habit of looking at it every once in awhile and soon you will know it by heart. Better still you can add those things that you keep asking, "Now which way did it go?" and remove the doubt.

Jim

[Oonrahnjay]

Used to be that the military used a lot of checklists, I doubt that has changed. We'd have a checklist for going to the john, I swear. OK so that's overdoing it but the point is valid, for those more important things (like making sure the batteries don't get drained unnecessarily) a checklist is still useful. If you make up a medium sized card, laminate it, put it on a string or chain so it can't wander, and then put it in a prominent place then you only have to make a habit of looking at it every once in awhile and soon you will know it by heart. Better still you can add those things that you keep asking, "Now which way did it go?" and remove the doubt.   Jim 

     Since I'm entering my 54th year of being a licensed pilot, I have checklists for many things on my bus.  But since I'm old enough to have been a pilot for 54 years, I have trouble remembering to use them.
     (PS Mfr. of my AGM bank says charge at 14.4, float at 13.6 +.2/-0.)

[Jim Blackwood]

Then I guess all hope is lost. Remind me not to fly with you! 

Jim

[eagle19952]

Mike, I haven't looked at this closely but my first instinct is to add a separate alternator for the "house batteries" and set that for AGM.  You'd have redundancy and a source of charge that you can set to the exact needed voltage.
But that may be over-thinking.

And that is why my starts are my house(well one reason).
I have 2 8ds now but have had 4. Depends on my plans/needs.
DEKA Marine AGM
Going on 8 years. This set. 16 years of combined.
probably looking for new soon.
PS Mfr. of my AGM bank says charge at 14.4, float at 13.6 +.2/-0.)


PS. My charge rates are the same...my inverter/charger and alternator are set to (pretty close) those parameters.

[MagnoliaBus]

I'm still at the beginning of my bus project and i have been thinking for a while about this battery bank vs alternator charging.
Since AGM batteries need a special charging algorithm, an alternator alone won't do!
What i'm thinking about for the house batteries is to have separate charger for each battery fed by an inverter or two or shore power.
Maybe four 8d (AGM). While under way, the alternator (let's say 450-500 amps 24v) would fed the inverters to supply 110-120 VAC to fridge, water heater and battery chargers. For sure it would require a lot of high amps relay to isolate each battery in the bank while in charge mode.
What do you think ?

[richard5933]

Personally, I'd never run a battery charger from an inverter. You're just layering loss on top of loss.

If you want to have something between the 24v chassis batteries and the AGM house batteries, then get something like this:

https://www.sterling-power-usa.com/SterlingPower24volt-to-12volt-dc-to-dc-batterytobatterycharger.aspx

We're using one to charge our 780 Ah 12v battery bank from the chassis alternator while underway. Allows us to push up to 70 amps to the battery bank, which for ours is just the right size charge. (Trojan recommends about a 10% charge for flooded cell).

The Sterling battery-to-battery charger can be setup to charge AGM batteries, it's a smart multi-stage charger, and it makes the whole thing really simple. Ours is connected in a way so that I've got to flip a switch to start the charging, but out of the box it will automatically charge when ever the chassis alternator is putting out a charging voltage.

The 120v battery chargers should be used only when on shore power or on generator power, not from another battery. Not sure why you need a separate charger for each battery either - just get one large enough to handle the whole battery bank and wire them all in parallel to each other.

[Branderson]

I'm still at the beginning of my bus project and i have been thinking for a while about this battery bank vs alternator charging.
Since AGM batteries need a special charging algorithm, an alternator alone won't do!
What i'm thinking about for the house batteries is to have separate charger for each battery fed by an inverter or two or shore power.
Maybe four 8d (AGM). While under way, the alternator (let's say 450-500 amps 24v) would fed the inverters to supply 110-120 VAC to fridge, water heater and battery chargers. For sure it would require a lot of high amps relay to isolate each battery in the bank while in charge mode.
What do you think ?

I'm by no means an expert if you have ever read any of my posts but I'm confused with your statement.  As long as I'm either connected to shore power or running the generator, my inverter charges my 2 house AGM batteries.  My assumption is that's the norm when having an inverter but maybe I'm wrong about it.

My alternator charges my start batteries btw. 

I don't understand why you think you need a separate charger for your house batteries.

[richard5933]

I'm by no means an expert if you have ever read any of my posts but I'm confused with your statement.  As long as I'm either connected to shore power or running the generator, my inverter charges my 2 house AGM batteries.  My assumption is that's the norm when having an inverter but maybe I'm wrong about it.

My alternator charges my start batteries btw. 

I don't understand why you think you need a separate charger for your house batteries.

Sounds like you have an inverter/charger. When you are plugged in, it acts like a charger for your house batteries. When you're not plugged in, it draws from your batteries and puts out 120vac. To contrast what you've got, our system uses a stand-alone charger that will charge the house batteries when we're plugged in, and a stand-alone inverter to make 120vac from the batteries when we're not.

Seemed like to me that he was going to use the chassis 24v system to power a couple of stand-alone 24v-to-120v inverters, and then use those inverters to power a couple of stand-alone 120v-to-12v battery chargers. That's why I recommended he skip the middleman (inverter) and just use a 24v-to-12v charger.

[MagnoliaBus]

I was just being too paranoid about batteries imbalance. You know, separating each battery for them to be charge by an intelligent charger.
I guess trying to achieve perfection is overkill...
Yes, will look at the Sterling products. Thanks !

[richard5933]

...Yes, will look at the Sterling products. Thanks !

If you have questions about the Sterling products, don't hesitate to call the number on their website. The guy that does their US sales seems to know his stuff and he was quite helpful when I was setting mine up. Their chargers give LOTS of options for how to set up.

[Oonrahnjay]

Sounds like you have an inverter/charger. When you are plugged in, it acts like a charger for your house batteries. When you're not plugged in, it draws from your batteries and puts out 120vac. ... 

      Yes, Brad, you have an inverter/charger, as Richard describes.  That's the "default" for most installations (bus conversions, service vehicles, specialty vehicles like mobile classrooms or bloodmobiles, etc.).  But some people prefer to have a separate charger for specific control of the charging; other people prefer to use models of inverters (brands like some models of AIMS, or Power Jack, for instance) that don't have chargers as part of their design. 
      You and I - and probably most other people that we'd meet at a bus rally - have inverter/chargers but; when we're talking about specifics of systems, it's probably good to remember that system types vary and a few people have systems that don't involve an inverter/charger, so when we're talking about those, their charging setup will be different.
      I have a 2kW "Outback" inverter/charger that has very good control of house battery charging; there is a separate control module that allows a flexible range of settings.  That part is really good, some of the other design characteristics and features of the inverter, I'm not so crazy about.

[TomC]

I have an old Trace 2512 modified sine wave inverter with 3 stage charging. I have 2-8D Lifeline AGM. I have the charge set at 14.1v max, and 13.2 float. First set lasted 7 years (with 5yr warranty). Now on second set.

Now starting to look at Lithium Iron batts. About 1/3 the weight, but about 5 times the cost of AGM. Good Luck, TomC