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Old 06-03-2016, 12:44 AM   #21
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Old 06-05-2016, 11:27 AM   #22
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so help me out some more on this gassing thing...

if i understand this right the only time batteries off-gas is being charged,,,

so for me the only time is when my bus is running... isnt there enough air leakage and such in a school bus that using an AGM battery wont off-gas??

so then I read about these batteries called VRLA ..

im REALLY confused aboutthis whole thing...

I really just wanted to stuff a couple 8D batteries into a cabinet out of sight.. hook them up through an isolater so my fantastic 200 AMP alternator could charge them up when my bus is running.. and not kill my starting cells when the bus is off..

but off-gassing, AGM, VRLA... red top blue top yellow top.. all has me more confused than ever...

if a battery is supposedly sealed but yet off gasses doesnt that mean that battery is killing itself? if I cannot replace the water and it gives off gas seems like that battery is just being ruined quickly.. therefore does a sealed battery not off-gas?

if an alternator in a bus or car constantly charges a battery.. and therefore theorrtically over-charges since it charges 100% when the vehicle is on.. how are my maintenance free car batteries lasting close to 10 years? wouldnt they gas away all of their water and be dead?

-Christopher
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Old 06-05-2016, 11:56 AM   #23
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Quote:
Originally Posted by cadillackid View Post
if an alternator in a bus or car constantly charges a battery.. and therefore theorrtically over-charges since it charges 100% when the vehicle is on.. how are my maintenance free car batteries lasting close to 10 years? wouldnt they gas away all of their water and be dead?

-Christopher
Each alternator has a regulator that senses how much amperage the system requires then energizes enough windings to meet the need. You'll see the voltage output change a few tenths of a volt but it's the variable amperage that charges (and protects) the battery. As your batteries charge, the regulator adjusts the amperage down so it doesn't boil the cells dry. As long as the regulator is doing it's job there shouldn't be a problem. The vented enclosure is there for the times when things go sideways.
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Old 06-05-2016, 01:14 PM   #24
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makes sense.. the alternator does drop the voltage the longer it runs .. starts out at close to 14 volts then drops to 13....

so on a normal basis an AGM battery doesnt outgas?.. only if my regulator decided to just rip it a new one.... at which time id see my voltage gauge up at 15 or higher...

how does a VRLA battery work?

or I simply need to place a relay on the battery that monitors voltage and charge current from the alternator going to that battery to know its charged and turn it off?

-Christopher
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Old 06-05-2016, 03:02 PM   #25
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Explanation of battery types.
https://en.wikipedia.org/wiki/VRLA_battery

All batteries have a vent, they have to.

Quote:
VRLA batteries have a pressure relief valve which will activate when the battery starts building pressure of hydrogen gas, generally a result of being recharged
Also any battery with a bad cell will act like it is being overcharged on that cell, and because the voltage isn't right on the entire battery the voltage regulator will try to charge it harder. It's a vicious circle.

I once mounted some batteries in an indoor cabinet, it was pretty simple to enclose them and vent to the outside. I used a number of the little 1 inch vents made to vent siding. Like these

Round Screened Vent, 1", Pack of 6 - Walmart.com

That trailer is still here, if you need pics I can get them later.

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Old 06-05-2016, 03:14 PM   #26
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since I only charge when im runniung the bus what if i just had a little fan that blew the air from the battery compartment of VRLA AGM batteries into the bus itself? seems like theres enough air leakage into a school bus being driven that Hydrogen isnt going to build up to a concentration to explode or smell bad.. if I did smell something id know i have a dead cell perhaps..

im just trying not to drill holes in the side of my bus that will let in and out the hot and esp cold air.. I could see the need for outside holes if I was charging from shore power and the bus was parked where i would have very little air infiltration from the normal bus methods like defroster intakes, leaky windows, etc

-Christopher
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Old 06-05-2016, 04:37 PM   #27
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If you seal off a compartment,and vent to the outside, how is precious cool or warm air going to get away?

You can do whatever you want, there aren't any "skoolie" police.

Dick
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Old 06-06-2016, 08:13 AM   #28
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Quote:
Originally Posted by somewhereinusa View Post
If you seal off a compartment,and vent to the outside, how is precious cool or warm air going to get away?

You can do whatever you want, there aren't any "skoolie" police.

Dick

if there were skoolie police id already be in Jail since I left most of the seats in the bus and didnt tear down my ceiling

im just tryign to get answers to 2 questions..

1. AGM VRLA batteries - if you never put water in them.. how can they off gas enough to cause issues and not be "dried up" within a short time.

2. AGM VRLA batteries - if they in fact outgas because my alternator decides to go rogue and push out 16 volts.. is enough gas produced to fill up the inside of a moving school bus that would either cause me to pass out or cause a fire, assuming the compartment is vented to the interior of the bus...

3. Standard Lead Acid batteries - I do understand that they boil when charged and have seen iot / smelled it when a car bnattery is put on a charger that has no management solution... so these type batteries are OUT for me unless i magically learn how to weld a battery compartment into my bus soon...

I really just want to be warm / cool / dry and not Blow up or die from some wierd gas..

-Christopher
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Old 06-06-2016, 12:30 PM   #29
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They are still lead acid batteries.

From the WIKI article I supplied a link to.

Quote:
Lead-acid cells consist of two plates of lead, which serve as electrodes, suspended in diluted sulfuric acid, which is then the electrolyte. In conventional lead-acid cells, the diluted acid is in liquid form, hence the term "flooded" or "wet" cells. VRLA cells have essentially the same lead-acid chemistry, but the diluted acid electrolyte solution is immobilized, either by soaking a fiberglass mat in it (hence: glass-mat batteries), or by turning the liquid into a paste-like gel by the addition of silica and other gelling agents (hence: gel batteries).
When a cell discharges, the lead and diluted acid undergo a chemical reaction that produces lead sulfate and water . When a cell is subsequently charged, the lead sulfate and water are turned back into lead and acid. In all lead-acid battery designs, charge current must be adjusted to match the ability of the battery to absorb the energy. If the charging current is too great, some of it will be wasted decomposing water into hydrogen and oxygen, in addition to the intended conversion of lead sulphate and water into lead dioxide, lead, and sulphuric acid which reverses the discharge process. If these gases are allowed to escape, as in a conventional flooded cell, the battery may need to be topped up with water from time to time. In contrast, in VRLA batteries the gases are retained within the battery as long as the pressure remains within safe levels. Under normal operating conditions the gases can then recombine within the battery itself, sometimes with the help of a catalyst, and no topping-up is needed. However, if the pressure exceeds safety limits, safety valves open to allow the excess gases to escape, and in doing so regulate the pressure back to safe levels (hence "valve-regulated" in "VRLA").
In flooded lead-acid batteries, the liquid electrolyte is a hazard during shipping and makes them unsuitable for many portable applications. Furthermore, the need to maintain water levels makes them unsuitable for maintenance-free applications. The immobilized electrolyte in VRLA batteries addresses these problems. At the same time, since VRLA cells can't be "topped off" with water, any hydrogen lost during outgassing can't easily be replaced. To some extent, this can be compensated for by overprovisioning the quantity of electrolyte, but at the cost of increased weight. The main downside to the VRLA design is that the immobilizing agent also impedes the chemical reactions that generate current. For this reason, VRLAs have lower peak power ratings than conventional designs. This makes them less useful for roles like car starting batteries where usage patterns are brief high-current pulses (during starting) followed by long slow recharging cycles. VRLAs are mostly found in roles where the charge/recharge cycles are slower, such as power storage applications.
Both flooded and VRLA designs require suitable ventilation around the batteries; both to prevent hydrogen concentrations from building up (hydrogen gas is highly flammable, and is an asphyxiant), and to ensure that the batteries receive adequate cooling.
Quote:
if they in fact outgas because my alternator decides to go rogue and push out 16 volts
Probably not likely, alternator/regulators are more likely to undercharge or not charge at all. I would be more concerned about this,

Any battery with a bad cell will act like it is being overcharged on that cell, and because the voltage isn't right on the entire battery the voltage regulator will try to charge it harder. It's a vicious circle.

The compartment does not have to be welded up out of metal. Furnace ducting or wood as long as it's sealed would do fine.

Dick
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Old 06-06-2016, 07:02 PM   #30
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good stuff!!! for some reason the link didnt work for me previously.. not sure why..

anyway its a great read..

I also talked to someone that made a great point.. his idea is this..

1. my batteries are House batteries, not starting batteries so building a box fits under the bus doesnt mean the skirting has to be cut and a fancy door installed.. a battery box with vents can be bought.. and then easily hung and tucked up under a Bus.. so theres no access.. you typically dont have to touch the house batteries.. install AGM VRLA so never have to water them..

the box can be lifted up and down by a floor jack with a platform.. (ie my transmission jack..)..

a box is easily hung without needing to weld.. it would have through-bolts and either large wasgers / plates into the bus floor... and those bolt holes are easily sealed.. hardware can be stainless steel and / or treated with grease / jelly, etc during maint intervals to keep the bolts from rusting into a mess..

run the wires from the box to a terminal block inside the bus... and thats where the parallel connection occurs, the isolator is located, as well as the connection to the alternator.. circuit breakers or fuse links install at this location as well..

thus if or when a battery goes bad or needs to be disconnected it doesnt require access to the battery box / boxes immediately as that can be done inside the bus.. and then such time when the bus is home the battery box could be lowered and the battery replaced or serviced / etc...

it could be years between times that box has to be lowered if good quality AGM VRLA batteries are used.. and esp if an isolator used is also a charge manager that keeps the charge always more than 20% and controls overcharging..

what you think? is this viable? or do batteries have to be touched more often than he thinks they do?

-Christopher
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