Capt_Leisure
Colorado Springs
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Here are the initial results of my battery charge tests. This thread originated from thoughts collected here: Battery Wire Replacement on a PUP???
Overall, I think I'm happy with the WFCO. I would like to perform the test again where the battery is slightly more discharged and possibly again, experimenting with turning lights on to add more load to the converter in an effort to get it into bulk mode. I'll need to do it again once the battery is relocated closer to the converter.
Bench results using Xantrex XPower Charger 40:
(charger set to 20 amp maximum output)
Open circuit battery voltage measured 12.37 VDC.
Specific gravity measured ~1.21.
Voltage and current measurements were read from the Xantrex unit's digital display panel (closely matches Fluke equipment used in next test).
7:20P 14.4V @ 20A
7:40P 14.4V @ 20A
8:00P no data
8:20P 14.4V @ 18A
8:40P 14.4V @ 10A
9:00P 14.4V @ 6.4A
9:20P 14.4V @ 4.4A
9:40P 13.6V @ 0A
10:00P 13.6V @ 0.7A - Disconnect
24 hours later, open circuit battery voltage measures 13.32 volts. Call it static charge, I guess.
Field results using WFCO 8735:
Open circuit battery voltage measured 12.33 VDC at battery.
Once connected, battery voltage measured 12.32 VDC at converter.
Specific gravity measured ~1.18.
Voltage and current measurements taken using two professional grade Fluke digital meters.
When the converter was first plugged in, the charge current initially climbed to almost 20 amps, then dropped quickly to about 8 amps. The current then started climbing slowly and within five minutes it had settled at about 14 amps. Converter voltage measured a pretty consistent 13.58 VDC and battery voltage varied a tiny bit (hundredths of a volt) depending on current.
12:25P 13.38V @ 14.5A
12:40P 13.39V @ 13.6A
1:00P 13.43V @ 11.0A
1:20P 13.48V @ 8.6A
1:40P no data
2:00P 13.50V @ 5.2A
2:20P no data
2:40P 13.51V @ 4.3A
3:00P 13.52V @ 3.0A - Begins to rain... unplug and fold up the PUP - leave battery connected
24 hours later, battery voltage measures 12.67 volts.
Technical Details
The battery is an Interstate Deep Cycle/Cranking, Model SRM-27, CCA = 775, Reserve Capacity = 160.
Temperature was approximately 60 degrees in both tests.
I have completely rewired my PUP in anticipation of relocating the battery to a rear bumper carrier. Currently, the battery still sits on the tongue.
There is a 14 foot length of #4 welding cable with a 40 amp fuse running from the positive terminal of the battery to a terminal block behind the converter.
There is a 3 foot length of #00 welding cable running from the negative terminal of the battery to the frame. There is a second 3 foot length of #00 welding cable running from the frame to a terminal block behind the converter.
I believe the converter uses only 10 ga. wire for the battery leads. The lengths are less than 1 foot from the terminal block to the converter itself.
* This post was
edited 04/28/09 12:12pm by Capt_Leisure *
2006 Starcraft 13RT - "We found that clowns are universally disliked by children."
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smkettner
Southern California
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Since the initial current only went to 20 amps the WFCO will not go to boost. You need to get the full 35 amp rating into the battery. Wire seems good at just 0.20 drop from converter to battery. A second battery or deeper discharge will be needed to get the full 35 amps out and cause the converter voltage to sag to 13.1 or less at the converter. Kinda sad but the 20 amp Xantrex performs better for this typical use.
Nice test and demonstration.
2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
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red31
Bryan
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Thanks Capt. I've been using the 8A setting on my Xantrex XPower Charger 15.
I believe I'll be going to the 15A mode, expecially with a generator!
I worried about being able to control the WFCO (thought about replacing my non charging 'power center'), 35 seems too much for one group 24 but Trojan replied when asked about 10% or 20% charge rate -
"There is really no limit to how high the initial charge current can be. We recommend that range of charge currents because charge systems are usually power limited and so we have to give customers a range. There are two things that you have to watch for when using high currents to charge batteries. The first one is that the current must be lowered before the batteries reach a voltage of 2.35 volts-per-cell. The second one is that the battery does not exceed 114°F. The only real advantage of having high charge currents is shorter charge times, but the implementation costs are usually too high."
Let the "smart" do it's job!
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smkettner
Southern California
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By the look of the first test you have 20 amps for one hour and maybe 8 amps average for the second hour. Seems like you were down maybe 30 amp hours and compared to a capacity of 115 it was at about 75% charge.
Second test looks like 24 amp hours replaced but it was not fully charged so again the battery was probably in the 70/75% charged range.
Get the battery down into the 30%/40% charged range and I think the WFCO performance could be very different.
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Guest
USA
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My cheapie Walmart deep cycle Group 27 has been charged and maintained by a WFCO converter since 2004 and still seems to have like new performance. If it weren't doing a good charge job, it wouldn't have survived my use so long and so well. Here's my routine:
1. Hook up battery to PU and PU to outlet 48 hours before camping.
2. Go camping
3. Keep plugged in at home for 48 hours after dry camping.
4. Unplug PU and unplug battery for storage.
5. Check water every 6 months and charge twice during winter (basement storage).
Battery gets about 7-8 deep cycles a year (usually down to about 12.0 volts)
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Capt_Leisure
Colorado Springs
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smkettner wrote:Get the battery down into the 30%/40% charged range and I think the WFCO performance could be very different. Yeah, that's what I was wondering too.
At first, I thought a depth of discharge to 30% seemed like pointless abuse. But then, recharging at a 20+ amp rate (in order to keep generator run time to a minimum) isn't helping prolong battery life either. After reading U.S. Battery Mfg's Expected Cycle Life Vs. Depth of Discharge table you linked to in the original thread, my overall picture became even clearer. I just had to do the math.
We only get out four or five times per year and recharge the battery once every 48 hours. Let's say my Interstate has half the cycles by discharging to 30% state of charge as compared to a U.S. Battery made battery (390 vs. 780). Let's say charging at a 20+ amp charge rate cuts the number of cycles in half again (totally made up number). Now I'm at 195 cycles. If we camp five times per year, the battery will be discharged ten times.
I don't expect any battery to last 19 1/2 years. Does this logic fly with you guys? Or, did I miss something?
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smkettner
Southern California
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I agree with letting the battery run down more than 50%. 11.5 to 11.9 volts under a small load is fine IMO. Recharging fully when done and proper storage is far more important to long battery life. US Battery also says it may take 25+ cycles to even break in and reach full capacity. That alone could take a year or two. Also figure if you discharge more it is few cycles.
I think the 50% limit is far more geared to the full timer that is consistantly off grid.
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4runnerguy
Glenwood Springs, CO
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Capt_Leisure wrote: I would like to perform the test again where the battery is slightly more discharged and possibly again, experimenting with turning lights on to add more load to the converter in an effort to get it into bulk mode. I read here that having all the lights on (and any other 12V usages going) helps convince the WFCO to go into bulk mode. Seems like a lot of effort compared to your Xantrex charger. I do wonder whether dumping 35 amps into a group 27 is the best thing for the battery.
Thanks for all the effort in pulling off these tests. From reading your earlier posts, I guess the good thing is that by reconditioning your battery, you got all the cells to about the same SG.
Ken & Allison
2 Camping Cats (1 diabetic)
1996 4Runner, TRD Supercharger, Edelbrock headers
2007 Fleetwood Arcadia, Honda EU2000i
4 mountain bikes, 1 canoe, 4 tents, 8 sleeping bags, 2 backpacks
(You get the idea!)
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Capt_Leisure
Colorado Springs
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4runnerguy wrote:I do wonder whether dumping 35 amps into a group 27 is the best thing for the battery.
I do not believe the converter is capable of charging at a 35 amp rate. I can't find any information on max. charge current, however the manual does specify a fuse no larger than 30 amps for the battery circuit.
When the converter was first powered up, the charge current ran up to 20 amps, then quickly dropped again. So, we know it's capable of charging at a 20 amp rate at least.
I kinda doubt the converter is designed this way, but with an isolated 20 amp charge circuit, if you plugged into shore power the converter would still be capable of providing 15 amps to run lights, furnace, water pump, etc.
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red31
Bryan
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From WFCO
"For any of our converters there is no way to control current entering into the battery. If the battery resistance is low it will draw up to the limit of the converter minus the electrical load of the RV.
Be Well,
Daniel Derrow
Technical Support
Phone: 877 294 8997 ext. 106
d.derrow@wfcoelectronics.com
www.wfcoelectronics.com
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