I bought an Interstate brand 7AH battery 11 months ago. It has had maybe 50 cycles, some to receiver low-voltage shutoff, but most were not. It has spent most of its time in float charge on the Trimble Office Support Module. A Trimble manual says "The battery can be left plugged in indefinitely, with no damage."
Today at 40^F I got 4.5 hours out of it to receiver shutoff. Last week at 35^F I got 5.1 hours. Playing with the leap second at the end of December at 30^F I got 5.7 hours. The battery is obviously dying, although it hasn't had anywhere near the months or cycles I'd expect.
Should I chalk it up to a bad battery, or is the charger frying it so in the future I should unplug from the charger except for occasional top-off charges?
I think it may be the deep cycling that's killing it. Those 7ah batteries are mostly intended for emergency lighting in buildings, where they'll spend most of their life trickle-charging and only run their lights for a few hours occasionally. For deep-cycle use a different construction method is used that doesn't produce the permanent degradation as quickly as a regular SLA.
I use regular SLAs a lot for static GPS use, but mostly 18ah and I don't often run them all the way down. Still, I've had mixed results with longevity; some seem to last for years, others crap out after a season or two. I usually buy the cheapest ones I can find, though, which may contribute to the apparent lack of consistency.
I think that leaving any battery attached to any charger longer than it takes to get a complete charge is not good for the battery.
A Harris, post: 411832, member: 81 wrote: I think that leaving any battery attached to any charger longer than it takes to get a complete charge is not good for the battery.
As A Harris says, that's been my experience over the last 20 years using one with a robot.
I know people who have cycled a 7ah SLA battery a few hundred times depending on the connectors f2 are the most common I have seen you can pick up a new one for under $20.
I dunno about the ah, but I do know that your charger can make a huge difference in how long a battery will last. Invest in a charger that has several settings, and that really does switch between float, maintenance, and charge modes. We learned this when we had one "good" charger, and one "regular" charger. The regular one only did float charges, which sometimes wasn't enough to get the battery back to full for the next day. That battery lasted about 8 months. The charger that senses the batteries charge and adjusts itself from hard charge to a maintenance state, we have run several of those batteries for two years plus, before loosing noticeable charge. We do use the heavy (70lb) SLA, with a pretty high storage and ah, because we can't always be where we can recharge each night, if that makes a difference.
I have a special charger that I bought at Batteries Plus when I bought my first external battery for my Topcon Robot. I've been through several batteries, but the charger is fine. It is supposed to be designed specifically for these types of batteries. It has small alligator clips on it, and it is supposed to keep from overcharging the battery.
I've posted this before, but that's not the best battery for what you're using it for. We use 35 Ah gel cells that are made for electric wheelchairs and they've pretty much eliminated our battery issues.
I've tried the gell cells and not really got any better life than a large deep cycle battery designed for boats. The gell cells cost more but they also weigh alot less so that is a big advantage to them. I'm using mine to power a 35 watt gps radio though. I've got a charger that is both a charger and maintainer so it can be left hooked to the battery all the time.
A lot of the time lately I'm just using the large battery to power the built in base radio, which is only 1 or 2 watts. They last a really long time if thats all I'm doing with it. If I'm using it to power the 35 watt radio, one battery won't last all day and if I'm using it all the time, I don't get 2 years of life out of the battery.
A quick search turned up http://www.powertechsystems.eu/home/tech-corner/lead-acid-battery-downsides/&apos ;">this. Some good info on batteries, I know they are selling batteries, BUT this same type of data can be found many places on the interwebs.
I just replaced two 35AH AGM batteries with two 18AH Lithium-Iron-Phosphate batteries for powering my total station and GPS base. Should have about equivalent USABLE power and they weigh about 1/3 of lead batteries and should have about 4X plus lifespan. The upfront costs are more, BUT long term the costs should be 1/2 of lead from a smaller lighter package.
I bought two of https://www.bioennopower.com/collections/12v-series-lifepo4-batteries/products/12v-20ah-lfp-battery-abs-sealed&apos ;">these.
The best electronic equipment in the world is just a paperweight without power!
SHG
This is a Trimble cowbell battery unit, and I've checked the OSM voltage - it settles out at 13.65 which is generally what I find recommended so don't think it's frying the battery. Last year I replaced the (probably original) PC1270 battery with the BSL1075 that Interstate said was the equivalent in stock.
I was hoping to get a lifetime more like shown in this company's data, which suggested 200 cycles even if I ran it down to the receiver cutoff voltage every time. But there may be differences in models for batteries of the same size.
http://www.power-sonic.com/images/powersonic/technical/1277751263_20100627-TechManual-Lo.pdf
SLA batteries are SO twentieth century. I have a couple 4500 mAh LiFePO4 batteries. One of them will run the robot AND the modem longer than I want to work on any given day. They're more expensive than SLA's, $65, but I'm near the end of 3 years with them, and still going-going-going. They also weigh much less than an equivalent SLA.
These folks know batteries:
http://www.batteryspace.com/128vlifepo4batterypacks.aspx
I bought a charger from them, too. $20
Sergeant Schultz, post: 411939, member: 315 wrote: I have a couple 4500 mAh LiFePO4 batteries.
Are those the kind that like to catch fire and burn their host building down?
Jim Frame, post: 411947, member: 10 wrote: Are those the kind that like to catch fire and burn their host building down?
No.
Jim Frame, post: 411947, member: 10 wrote: Are those the kind that like to catch fire and burn their host building down?
https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery
Sergeant Schultz, post: 411939, member: 315 wrote: SLA batteries are SO twentieth century. I have a couple 4500 mAh LiFePO4 batteries. One of them will run the robot AND the modem longer than I want to work on any given day. They're more expensive than SLA's, $65, but I'm near the end of 3 years with them, and still going-going-going. They also weigh much less than an equivalent SLA.
These folks know batteries:
http://www.batteryspace.com/128vlifepo4batterypacks.aspx
I bought a charger from them, too. $20
Rough calculations place my 18AH LiFePO4 batteries at about 24 hour run time for my Leica GNSS receiver and an Intuicom RTK bridge, so about three days in the field in a seven pound package.
Expensive upfront? Yes! Not running short of battery, PRICELESS!
SHG
Shelby H. Griggs PLS, post: 412040, member: 335 wrote: Rough calculations place my 18AH LiFePO4 batteries at about 24 hour run time for my Leica GNSS receiver and an Intuicom RTK bridge, so about three days in the field in a seven pound package.
Expensive upfront? Yes! Not running short of battery, PRICELESS!
Agreed. In 2008 I made up several similar batteries (8aH) which still keep a robot going for three days. I assume they must eventually reach life expiry. They also seem to hold charge indefinitely. One is kept "spare" on the shelf for emergencies: after 6 months it will still have nearly full charge. Yes, I know they aren't supposed to be kept fully charged, so the spare is occasionally rotated with the others but it doesn't seem to have done any harm. When constructed they cost the equivalent of $200.
I think I know what killed my battery. The leap-second experiment ran it down to receiver shut-off and then it sat for 3 or 4 hours before we got home and I brought it in out of the cold. The outside temperature started at 30^F and got colder through the night, so in the discharged state the battery may have started to freeze and disrupted the internal construction. A charged battery won't freeze at any temperature we're likely to experience here, so I hadn't foreseen that.
The guy at the battery store didn't know much, so I looked around and found this nice summary of 4 types of SLA batteries.
https://www.batteriesplus.com/t/battery/sla-types
I had an AGM (absorbent glass mat) type meant for standby use that should have given 200+ cycles. I want deep-cycle one made for scooters because it should handle cycling better. The GEL type would be nice but probably not compatible with my charger as they need to float at a slightly lower voltage. The high-rate ones are for uninterruptible power supplies that will empty them in under an hour, but won't hold up as well to cycling.
The alternative to deep-cycle is to have at least double the amp-hours you ever expect to use and not run it down so far, as that more than proportionally increases the life.
I have been thinking about cutting down on the chargers, and getting this 4-bank charger
https://www.amazon.com/NOCO-G4-UltraSafe-Battery-Charger/dp/B0068EV26I