I don't have timers on our coach, but I do have 2 Battery Tenders, 1 for the coach & 1 for the chassis batteries. They worked great last spring after being in storage for 6 months.As best as I can tell, there were/are no problems with freezing & we do get below zero temps. The previous 4 years I would disconnect all the dozens of wires/cables & take all 5 batteries out & place them in an above freezing area. I don't miss that aspect one bit. If anyone is interested in going with Battery Tenders, I'd recommend checking out some of the motorcycle parts/equipment suppliers, they seem to have the best prices.Some even offer free shipping.
BTW,I have been using the Tenders on our classic car for 6-7 years with excellent results. HTH, Bob L.
From the great barren white north--
Batteries LIKE cold , do not freeze (when charged), need 90 day charge"top up", should be disconnected to prevent phantom load discharge. Need to have clean terminals and CAN sit on a cement floor.
Do not start A/C's in freezing weather- very tough on the compressor.
A fully charged battery will not freeze until 60 to 70 below zero whereas a discharged battery can freeze at 20 degrees above zero. As a battery discharges, the acid turns into water by the basic chemical nature of the lead acid battery. The more discharge, the more water and the more likely it is to freeze. Also a dirty, acid covered battery will self-discharge at a faster rate than a clean treated battery, even in cooler temperatures.
From: http://www.isnare.com/?aid=185779&ca=Sports
Sealed Lead Acid Battery Storage
Power-Sonic Batteries should not be stored in a discharged state or at elevated temperatures. If a battery has been discharged for some time or the load was left on indefinitely, it may not readily take a charge. To overcome this, leave the charger connected and the battery should eventually begin to accept charge. Although Power-Sonic batteries have a low self-discharge rate which permits storage of a fully charged battery for up to a year, it is recommended that a battery be charged 6-9 months after receipt to account for storage from the date of manufacture to the date of purchase. Otherwise, permanent loss of capacity might occur as a result of sulfation. To prolong shelf life without charging, store batteries at 10 degrees Celsius or less.
Gaston: Lead-acid batteries previously were affected by long term storage after charging. But Gaston SLA batteries are not so affected. This battery offers longer extended storage than conventional batteries (referenced curve shows 3% per month self discharge rate at 20 degrees C.) During storage, carry out supplementary charging according to Table 3 (below 20 degrees charge every 6 months, 20 to 30 degrees C charge every 3 months, over 30 don't store). Although the self-discharge rate is low, specific precautions must be taken against the battery over discharging itself by self-discharge when in storage or not operating. In general, to optimize performance and service life, it is recommended that Gaston batteries which are to be stored for extended periods of time be given a supplementary charge, commonly referred to "top charging" periodically. The top charge referred to is a charge of 20-24 hours at a constant voltage of 2.4 volts per cell.
from:
http://www.powerstream.com/Storage.htm
Trickle chargers are set at near 15V. For a float charge they need to be 13.5 volts. This is not available in a cheap charger.
Get a multi-stage charger if you feel the need to charge it more than necessary.
Below is fromttp://www.batteryuniversity.com/partone-13.htm
Charging lead-acid batteries with a power supply
Lead-acid batteries can be charged manually with a commercial power supply featuring voltage regulation and current limiting. Calculate the charge voltage according to the number of cells and desired voltage limit. Charging a 12-volt battery (6 cells) at a cell voltage limit of 2.40V, for example, would require a voltage setting of 14.40V.
The charge current for small lead-acid batteries should be set between 10% and 30% of the rated capacity (30% of a 2Ah battery would be 600mA). Larger batteries, such as those used in the automotive industry, are generally charged at lower current ratings. Cells constructed of a non-antimonial lead grid material allow higher charge currents but have a lower capacity. The cylindrical Cyclone is sealed and can sustain a pressure of up to 3.5 Bar (50 psi). A pressurized cell assists in the recombination of gases.
Observe the battery temperature, voltage and current during charge. Charge only at ambient temperatures and in a ventilated room. Once the battery is fully charged and the current has dropped to 3% of the rated current, the charge is completed. A good car battery will drop to about 40mA when fully charged; a bad battery may not fall below 100mA.
After full charge, remove the battery from the charger. If float charge is needed for operational readiness, lower the charge voltage to about 13.50V (2.25V/cell). Most chargers perform this function automatically. The float charge can be applied for an unlimited time.
* This post was
edited 10/08/08 08:50am by dentmac *
I installed a multi-stage charger converter in my old Bounder and it works great. I could leave it plugged in all the time and the batteries held up perfectly. While boondocking, I would run the generator for a couple hours in the evening and this charger had kept the battries up much better than the old one.
While I recognize the "AC" stands for both Alternating Current AND Air Conditioning, I'm sure the original poster meant that he wants to turn on the electricity once in a while and not the Air Conditioner. (I hate letter abbreviations - they either cause confusion or someone like me doesn't know what they mean, period.)
Anyway, I think Bumpy has a simple and adaquate solution, of just tuning on the power once a day, and know that things are going to be fine.
I was never one to believe in "exercising"
Ive had a set of deep cycles for the boat that I take out every year I think they are about 8-10 years old I make sure they are charged, and take them into the basement,, I never trickled, floated, tended, or any of those things, Put them in the boat in the spring and crank away on the sams club specials never have failed me.
Also have a early 80's homelite gen,,, sat for 8 years, drained the oil, cleaned the mice out of the airfilter and cleaned the plug new oil 3 pulls, ran for a week straight when our power was out no issues
I will make sre they are charged and then disconnect them from everything including the series/parrallel wiring to each other. they are new. I dont 4c any issues with letting them sit for a couple months (same with the genny)
Our solar charging system does well keep batteries up to full charge while stored with no power access...until the white stuff comes a;ong and buried the face plates. Then the generator needs to top off every once and awhile. Last year I had a small issue with the generator and was unable top off in minus zero weather...froze them solid...really enjoyed my new batteries this year.
Joan and Bruce
05 Excursion 39L
powered by 350 KittyCATS on a Spartan
2005 CRV SE toad (Blue Ox & Breakbuddy)
...and a "road dog" named Max
"May the wind be always at your back"
Many thanks to all who took the time to reply. Replacing the converter is a good idea, but a bit expensive at this time. I think the idea of putting two mechanical timers in series is a good one and I'll experiment with it. I plan to get a Trik-L-Start to keep the chassis battery charged as well.
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