| Author | Message | ||
| David Ljung Madison (Daveola)
Registered Member Username: Daveola Post Number: 68 Registered: 11-2005 Posted From: 63.204.157.4 Rating: N/A |
A while back I posted about my bus plan. It created quite a stir, and I was told that my electrical plan was essentially impossible. The best advice I got, however, was to go ahead and do it and post to the board about it. So here we go. The plan was to be able to get a large enough battery bank and genset to be able to run full power (including some air conditioning) off of batteries with occasional recharging. I ended up putting most of it together as I had planned. If you are unfamiliar with the design I was hoping to accomplish, most info is up at: http://bus.getdave.com/Infrastructure/Electrical/ Anyways, I finally installed the genset, battery bank and inverter and had a chance to briefly test it up in the desert. The batteries were fully charged (sadly I didn't get a chance to measure open-circuit resting voltage). Stats: Outside temp: Over 100 degrees (the A/C compressor was running strong) A/C: Carrier AirV 15kBTU (~14.5A full load) Batteries: 10 DEKA AGM Group 8D batteries (24V 1225Ah - 29.4kWh) Inverter: Trace SW4024 I ran one of my A/C units on high with full cooling for over 2.5 hours (as well as lights, refridgerator, etc..). Then I disconnected the batteries and let them sit for 1.5 hours. Measured the open circuit voltage and the batteries were still very close to full charge (almost 25.4V). The batteries weren't melting - they weren't even warmer then the ambient temp in the bay - the inverter (with batt temp sensor) showed similar voltage. In fact, they read slightly better than expected - I'll have to make sure that DEKA agrees with the Xantrex voltage setpoints for charging AGM batteries to make sure I'm not slightly overcharging. But, as expected, my electrical load was probably somewhere between 3 and 5 kWh, around 10-17% of my full capacity. At 2.5 hours, that's no more than a C/15 discharge rate. When I get a chance to get back out to the desert I'll run longer tests, I also need to finish my circuits and get another inverter to test running both A/Cs (and hopefully a Bogart meter to boot). I think it's clear they should work fine, probably pushing a C/10 discharge rate. I recognize that this will lower my battery life and am comfortable with that tradeoff. I think it's safe to say that the batteries won't start on fire.  For those of you who read the original "Dave's Fool Bus Idea" topic, no, the batteries do not weigh 6 tons. They're about 3/4 of a ton. My bus has not broken in half. So the summary is this: You *can* run Air Conditioning off of batteries. It requires a heck of a lot of batteries and a big inverter, so you probably want to have a definite need (as I do) to justify the expense. I know that a few others on this board have done similar things - thanks for the support and kind words. | ||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 263 Registered: 12-2004 Posted From: 206.212.230.165 Rating: N/A |
That's great that the batteries are working our for you. Do keep us posted so we all learn from your efforts. Thanks for the update. Craig - MC7 Oregon | ||
| Jerry Liebler (Jerry_liebler)
Registered Member Username: Jerry_liebler Post Number: 227 Registered: 3-2005 Posted From: 67.140.163.114 Rating: N/A |
Dave, You can do much better in terms of cooling per watt. I'm looking at a minisplit heat pump that does 18000 BTU/h cooling on 1200 watts. Unfortunately this is a 240 volt unit but my plan is to add a transformer so it will work on 120. With 90% tranformer efficiency it'll still draw under 11 amps. Regards Jerry 4107 1120 | ||
| David Ljung Madison (Daveola)
Registered Member Username: Daveola Post Number: 69 Registered: 11-2005 Posted From: 63.204.157.4 Rating: N/A |
Jerry: How much are these systems? Can you easily and safely mount the condenser side on the roof? | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 304 Registered: 10-2003 Posted From: 69.162.3.30 Rating: N/A |
I know that it may take a while to determine when the batteries will need replacing, but when that happens, calculate the total cost of your system compared to running a small gen set to accomplish the same result. | ||
| Jerry Liebler (Jerry_liebler)
Registered Member Username: Jerry_liebler Post Number: 228 Registered: 3-2005 Posted From: 67.140.163.114 Rating: N/A |
Dave, It's on Ebay for $999 + shipping (the brand is Celiera). The company selling them is in Detroit and I plan on picking it up to avoid shipping. Also when I called they offered a slightly lower price. I sure wouldn't want the condensor on the roof,it's about 2ft high and 3 ft wide, my plan is in the old HVAC bay. Regards Jerry 4107 1120 | ||
| David Ljung Madison (Daveola)
Registered Member Username: Daveola Post Number: 70 Registered: 11-2005 Posted From: 63.204.157.4 Rating: N/A |
I am quite clear that my system is more expensive than running a genset whenever I need A/C. I fully understand that. This system was not created to be the cheapest system possible, I had some requirements for genset runtime that I needed to accomplish regardless of cost. If this is difficult to understand, then I pose the question: calculate the total cost of running a genset versus being plugged into shore power or the grid to accomplish the same result. Obviously the genset is more. My circumstances are different from yours, so again, I do not recommend that everyone goes out to purchase 10 group 8D batteries. Note the end of my last posting: "so you probably want to have a definite need (as I do) to justify the expense." | ||
| Kyle Brandt (Kyle4501)
Registered Member Username: Kyle4501 Post Number: 188 Registered: 9-2004 Posted From: 65.12.100.208 Rating: |
David, thanks for buttin' heads with the naysayers! Keep on doing it your way! As far as putting the condenser on the roof... Watch for height issues, the taller your coach gets, the more stuff is out there trying to knock it off! BTDT Keep posting updates, as I'm very interested in the results too. kyle4501 | ||
| Rusty Thompson (Rusty)
Registered Member Username: Rusty Post Number: 39 Registered: 6-2005 Posted From: 12.191.99.42 Rating: N/A |
David I also went the ductless mini-split way, also bought off of e-bay about a year ago. I went with two 3/4 ton, (9000) btu units so that I could run one at a time (energy saving) if needed, on in front one in back, the indoor unit is small about 8in high 4in deep and 2 feet long, the out door unit is about 2 feet high 1 foot deep and 2.5 feet long, I also plan on mounting them in the bays of my bus facing out on each side. They are Sanyos, and they cost me total 855, 700+155 shipping, very reasonable I thought, just look for deals their out their. Hope this helps | ||
| Greg Peterson (Gpmci102)
Registered Member Username: Gpmci102 Post Number: 22 Registered: 8-2006 Posted From: 71.194.70.124 Rating: N/A |
Where did you get the AGM batteries? Did you find a good deal? You probably got a good price by buying 10 of them. I will need a couple someday for my bus. When I read your old post I believed you would be able to make your system work. They used to run Submarines on batteries so anything is possible if you have lots of big ones. Nuclear power is nicer in Subs though. Hey, how about a small nuclear power plant like the Russians used for their Satellites and Military Weapons. They probably are selling them for surplus. I will start watching ebay for one. If I had one of those nuclear generators in my bus the emissions from my 2-stroke engine would be the last thing the EPA would be worried about. | ||
| David Ljung Madison (Daveola)
Registered Member Username: Daveola Post Number: 71 Registered: 11-2005 Posted From: 63.204.157.4 Rating: N/A |
I got the batteries when I picked up the genset from Wrico. The batteries were a decent enough price, though I was really there for the genset, which is great so far. If I had more time, I would've waited and bought a used forklift battery and dealt with the shorter life span - seems if you find the right battery on ebay you can get it for under $1k. There was an awesome 75kWh bank going for $500, but it was bigger than I needed... Another option, given more time, is to take some used batteries from a server colocation facility - they usually toss out their batteries with lots of life left in them. Too bad I didn't have more time. | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 89 Registered: 7-2006 Posted From: 66.217.107.59 Rating: N/A |
Hey Greg...... HAR HAR HAR | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 889 Registered: 12-2000 Posted From: 64.228.88.210 Rating: |
Hello David. Great job, keep the info coming! I knew a couple with 16 golf cart batteries up under the nose of an MC9, big Trace, rear bedroom, roof airs, well insulated. Silent sleeping, in any conditions. What progress has ever come from conventional thinking? happy coaching! buswarrior | ||
| Brian Brown (Blue_velvet)
Registered Member Username: Blue_velvet Post Number: 380 Registered: 6-2005 Posted From: 67.174.112.202 Rating: N/A |
Hey Dave: Keep pushing that technological envelope! Great work. I hope you continue to post your findings with us. FWIW, I had a guy that came by my place a few months ago from Austin, TX. He was looking at a bus conversion I had for sale then, but we got to talking about battery technology advancements. He works on the "bleeding edge" of technology by providing venture capital to start-ups. Anyways, he mentioned one company that was developing inverter/ battery bank combos for the trucking industry to give truckers heat and A/C in anti-idle zones. IIRC, he mentioned things like "double the current desnsities of lead-acid cells" and "extremely fast recharge rates off of a truck alternator". This isn't exactly my area of knowledge, but I dunno if anyone's read up on these things... Brian Brown 4108-216 Longmont, CO | ||
| David Ljung Madison (Daveola)
Registered Member Username: Daveola Post Number: 72 Registered: 11-2005 Posted From: 63.204.157.4 Rating: N/A |
Yea, but I wonder what the cost is. In five years or so we'll hopefully see nanotube capacitors as a battery replacement - then we'll have recharge rates of a few *seconds* (given a strong enough power source) without the battery life problems of lead-acid. When that day comes, if I can afford the batteries, I'm tempted to try to put a clutched genhead (or set of genheads) on my bus engine to generate about 175kW of juice. With that I could charge my battery bank for the whole day in about 8 minutes of running my bus engine. Ahh... Dream on... | ||
| Tim Strommen (Tim_strommen)
Registered Member Username: Tim_strommen Post Number: 234 Registered: 11-2004 Posted From: 64.186.173.26 Rating: N/A |
For now you can always get Ultra Caps from Maxwell. 430 Farads @16.2v (2.5mOhm ESR) anyone? I've been playing with some of their smaller ones (and they're fairly inexpensive) for power supply stiffening for the stereo in my pickup. Makes a heck of a difference. Maxwells caps are being used for fast energy recoverey in regenerative-braking/hybrid drive systems now. Cheers! -Tim (Message edited by Tim Strommen on September 14, 2006) | ||
| David Ljung Madison (Daveola)
Registered Member Username: Daveola Post Number: 73 Registered: 11-2005 Posted From: 63.204.157.4 Rating: N/A |
Are you using the caps in your A/C units for motor startup, or just on your batteries? | ||
| Tim Strommen (Tim_strommen)
Registered Member Username: Tim_strommen Post Number: 235 Registered: 11-2004 Posted From: 24.6.207.238 Rating: N/A |
Clarification: As of yet, not using them in a permanent installation on my bus - only my pickup truck for the stereo (Simple economics: 1F Monster "Power" cap= $145, 56F Maxwell Ultra-cap=$250, naturally I bought two - one for each amp). I did, however, experiment with them in series on the bus at the starter solenoid (24v bus power) - and it did appear that they enhanced the surge start current of the engine. I'm planning on acquiring a few of their slightly higher rating caps (taking the leap from the 56 Farad caps to the 430F ;-) ) for DC power generation and stiffening - since all of the batteries for the engine are now located in the engine compartment (within 3-feet of the Alternator). I was planning on trying to replace the 8D batteries with some Optima Blue-Top Deep Cycles 35M Ithink?) and allowing the 215 farads of series caps to take up the high surge demand from the starter, just as an experiment on battery life cycles. I'm a fan of all-electric coaches - just not the AC variety. 24VDC all the way! Cheers! -Tim |
