| Author | Message | ||
| Ray D Rating: N/A |
On putting batteries in the engine compartment, I called East Penn on AGM's . They said that the AGM battery would work fine there, but the life span may be slightly shortened and the chemical activity is greater at higher temps (is this good or bad?). He evaded any specifics on any of this & would not say if it would affect the efficiency a little or a lot. He only said that all batteries are affected by heat, even liquid acid. Just because a battery is installed under the hood of a car does not mean that is the best place to put it. More confused than ever??? Ray D | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Higher temps will affect the charge rate abilities and the discharge abilities of the pack. Also the heat can affect the case of the batts (wide/frequent thermal cycles can weaken the plasic and make it brittle). One other detail that is not often thought of is the temperature rating of the battery wires you use. You need to ensure that the voltage drop is okay for the lenght - and that the full electrical load you intend to apply to the wires will not raise the temp of the strands to where it will melt the insulator (8Ds make DC arc welding sets!). My advise to you if you place the batteries in the engine space, is to allow for thermal sheilding from the engine compartment and cool fresh air intake (preferably with no or a brushless fan) from the outside to keep them cool. Cheers! -Tim Strommen | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
I've had my house batteries literally on top of my engine for what, 5 years now, still going strong and not a hint of trouble. It's a set of T-105's and I've got that pancake "on it's side" cummins 220... the batteries get right up to engine temperature when I'm driving. No big deal. I think it is one thing if you were to put batteries in an engine compartment and drive 12 hours a day, 7 days a week for years on end, and it's an entirely different situation in a recreational bus that gets driven even 10,000 miles a year, probably loads less. You've got a lot more to worry about than keeping them cool (ie sitting unused for long periods of time, keeping them properly charged, etc) My vote is, don't worry about it. Put them where you want to, keep them properly charged and they'll probably outlast the bus!! | ||
| Robert J. Wies (Ncbob)
Rating: N/A |
For years I've used welding cable in situations where there is heavy current draw from the battery banks. I have both the scissor type crimpers and the 'bash it with a BFH' type for both terminal ends and haven't had a bad cable problem....ever. The welding cable does what it's designed for and maintains flexibility under all temperature conditions. Just MHO. | ||
| John MC9 Rating: N/A |
Since your question was regarding AGM batteries specifically, I found some good reading here: AGM Batteries They appear to answer your question (?): CHARGING VOLTAGE VALUE IS CRITICAL AGM and Gelled batteries require a charging voltage that does not exceed 14.00 volts (summer temperatures may require even lower voltages). Unfortunately almost all automotive charging systems have a permanently fixed set point voltage that exceeds 14.00 and this spells trouble. Subjecting the batteries to (commonly found) 14.6 volts for a prolonged period will eventually destroy them. Pusher diesel motorhomes normally use truck-type alternators and voltage regulators and most have internal set screws which can be fine-tuned (To lower the voltage set point). Automobiles (pickup trucks) and standard motorhome charging systems can be modified to accept an exterior adjustable voltage regulator. Your local automotive electrical rebuild shop can be a lifesaver if you elect to go that route. For your edification, 14.05 volts is my personal "upper limit" for charging valve regulated batteries. THERMAL RUNAWAY The name "thermal runaway" sounds ominous and when it happens to an Absorptive Glass Mat battery the results can be dramatic. A curious electro chemical reaction can take place inside an "AGM" battery if it is overheated while being charged. The phenomenon can be the result of too high a charging voltage, which will overheat any battery, too high an environmental temperature or a combination of both elements. Instead of tapering off, the charging current actually increases as the battery temperature increases. In extreme cases the electrolyte and binder material can be forcibly ejected from the battery vents. Obviously the battery will be destroyed. The point here is to pay attention to the battery's location and charging voltage limit. MODERATE TEMPERATURE ENVIRONMENT Both gelled electrolyte and AGM batteries insist on being located in an environment well away from high underhood engine or radiator temperatures. As a matter of fact the manufacturers of these types of batteries insist that all charging must cease altogether if the core of the battery reaches one hundred twenty degrees Fahrenheit. This point becomes critical in some pusher diesel bus applications that fit the house batteries in the path of radiator exhaust heat! The site contains much more info, and is worth the time to read! http://www.rversonline.org/ Cheers! | ||
| Jon W. Rating: N/A |
I should have pointed out when I discussed the problem of battery heat that my experiences were from the early nineties and I had one of the early sets of gel cells from Interstate (johnson Controls). We learned through actual use exactly what John posted above. I monitored the battery temperatures and during the period had numerous different sets of batteries and before we ended the test had two batteries burst. The conclusion as I posted on the other thread was that when batteries are exposed to elevated temperatures only wet cell batteries are capable of dissippating some of the heat. Interstate supplied the batteries (gell and conventional) for free throught the local distributor and because of the failures I reverted back to wet cell. The coolest part of the batteries during the period often was in excess of 130 degrees F, with higher temperatures toward the engine. Obviously these temperatures were only experienced when the engine was running and we were traveling. This was on a 1987 Prevost. The charging voltage is an entirely different issue, but in concert with high temperatures, a charging voltage of greater than 13.8 (or thereabouts) is the kiss of death for batteries. | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
Yeah...oops, foot in mouth... I'm talking about my experience with wet cells, not gel or agm... Guess I better learn how to read better  | ||
| John MC9 Rating: N/A |
Gary - I can't speak for others.... but I've never failed to learn something of value from your posts.... regardless of on, or off topic.. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
"a charging voltage of greater than 13.8 (or thereabouts) is the kiss of death for batteries." If I am not mistaken, all automotive charge systems are at approximately 14.5 volts. It would take forever to re-charge a discharged battery with only 13.8 volts. Maybe this was aimed at other than wet cell batteries. Richard | ||
| Ray D Rating: N/A |
Thanks for all the answers. I will not put AGM's back there, I just hate to waste that space. Does everyone think that AGM's are that much better than regular batteries? I could put them back there, but I don't want to if there is a big difference. Ray D | ||
| Jon W. Rating: N/A |
Driving miss lazy, The 13.8 is for AGM batteries. They have a different charging requirement than wet cell. If they are charged at the normal 14.25 and they are in a hot environment they will soon experience thermal runaway as John posted. | ||
| truthhunter@shaw.ca Rating: N/A |
Is it also true that you can put a larger amp charge in to AGM batteries and they can take less than full charge without a drastic reduction in the life span ? | ||
| FAST FRED Rating: N/A |
Is it also true that you can put a larger amp charge in to AGM batteries and they can take less than full charge without a drastic reduction in the life span ? The acceptance of the inital recharge rate IS better for AGM. Flooded will need to be limited to 20 or 25% of 20 hour rate (the real battery size) AGM can handle 75% , but ONLY with a temp sensor . AGM can be disacharged deeper and not suffer as much as wet cells. Thats why I think folks should decide batt cost in dollars per useable amp. IF you have a smallish bat set and huge alt the cost in recharge time may be justified , or are doing DC recharging with a BIG dc noisemaker. For a really large bat set the advantage would not be that great as few affordable alts are over 300A. FAST FRED |