Solar planning thoughts

freds · October 25, 2019, 05:44:35 PM

My house battery's are going to be Tesla Battery modules which I will pair with a 6KW split phase 240 volt inverter that works with the Tesla Chemistry.

Kicking around idea's on how to charge the house battery while in motion using the 24volt alternator.

The safest I think would be to use a solar charge controller and switch the alternator from the start battery's to the charge controller and boost charging voltage to 30 volts so the charge controller has the necessary head room to work. Maximum voltage for the Tesla battery pack will be 24 volts.

Any thoughts?

richard5933 · October 25, 2019, 05:57:29 PM

You could get a battery-to-battery charger like the ones that Sterling makes. We've got one to charge our 12v house battery bank from the 24v chassis system. They also have 24v-to-24v. The advantage to something like this would be that it is a true multi-stage charger. You could also do it like you're describing with the solar charge controller, but I prefer to have dedicated equipment.

neoneddy · October 25, 2019, 06:09:13 PM

You can charge direct from the alternator, just keep the voltage below I'm the max voltage.

I used to be looking for Tesla packs until I saw a few blow up. Cost per watt hour those valence ones are hard to beat.

Iceni John · October 25, 2019, 08:42:23 PM

My PV installation is essentially two entirely separate systems running in parallel, so if anything goes tits up I will still have at least 50% of my power production ability. Redundancy is good! I first made a walkway between my two roof hatches, then hinged each panel from that walkway, four on each side; each side of four parallel-wired panels feeds its own charge controller that charges its own bank of batteries, then both banks are combined through Schottky diodes to prevent one bank back-feeding into the other. The panels and walkway also keep the bus appreciably cooler inside because so little of the roof now gets any direct sunlight on it. The panels lock down (at 21 degrees down) for travel, or can be raised to 21, 33 or 45 degrees up depending on the season. I also put two quick-connect water outlets on the walkway, so to wash bird crap / dust / leaves / etc off the panels I get up onto the walkway and just plug in my washdown brush - it's almost fun to clean them this way!

In addition to always having my house batteries fully charged each day, they now also provide power to the start batteries' maintainer chargers, so even they are now solar-charged to 100% every day. For the desert SW of the US there's really no reason to not have solar - there's nearly always ample sunlight all year.

John

chessie4905 · October 26, 2019, 04:45:30 AM

Does it hurt a solar panel to be in sunlight with it not connected?

petarm1 · October 26, 2019, 08:07:53 AM

I would like to see some pictures of the folks that have a permanent mount on their buses.

Brian Diehl · October 26, 2019, 08:10:44 AM

Quote from: neoneddy on October 25, 2019, 10:16:53 AM

I also didn't see anything there about batteries. In a bus you have options. A lot of people recommend Battle Born batteries and they are good for the lithiums, but super expensive. I'm really impressed with these Valence Batteries right now https://www.ebay.com/b/Valence-Rechargeable-Batteries/48619/bn_114829959 130+AH@12v for $450 Most of these are testing at 95% capacity. The medical devices they come from are switched out yearly or something. I ended up with 6 Telecom AGM batteries I got for $150-ish each or so. 210 AH @12v , yeah they weigh 130lb each, but $1000 for 14kw of battery storage is hard to beat even if it's an older chemistry.

Is there any information available on what type of BMS these batteries have internally to them?

neoneddy · October 26, 2019, 09:11:11 AM

Brian, re:bms there are balance leads under the cap. Word is there is a company developing a system that works with its bms wiring. I've seen talk on the DIY RV solar Facebook group.

freds · October 26, 2019, 10:27:34 AM

Quote from: richard5933 on October 25, 2019, 05:57:29 PM
You could get a battery-to-battery charger like the ones that Sterling makes. We've got one to charge our 12v house battery bank from the 24v chassis system. They also have 24v-to-24v. The advantage to something like this would be that it is a true multi-stage charger. You could also do it like you're describing with the solar charge controller, but I prefer to have dedicated equipment.

I dropped them a note, however it looks like they don't support user configurable settings which I would need for my Tesla Battery modules.

I also came across another vendor that I sent a note too: https://ablemail.co.uk/battery-charger

freds · October 26, 2019, 10:33:55 AM

Quote from: neoneddy on October 25, 2019, 06:09:13 PM
You can charge direct from the alternator, just keep the voltage below I'm the max voltage.

I used to be looking for Tesla packs until I saw a few blow up. Cost per watt hour those valence ones are hard to beat.

Was this in RV usage? Power density wise each module is equivalent to four battle borns. So, needs to be treated with respect and management.

My daily driver is a Tesla Model S that bought five years ago, so I guess you can say that I drank the Kool Aid!!! (The only problem is that it doesn't fly).

richard5933 · October 26, 2019, 01:10:49 PM

Quote from: freds on October 26, 2019, 10:27:34 AM
I dropped them a note, however it looks like they don't support user configurable settings which I would need for my Tesla Battery modules.

I also came across another vendor that I sent a note too: https://ablemail.co.uk/battery-charger

Check page 11 of this manual: http://www.sterling-power-usa.com/library/2018_green_ultra__Ultra_InstructionsEng_Ger.pdf

I've got the 12v output version, and if it works like mine you can custom set all three charging stages. My reading of this manual shows that you can custom set the output on the 24v version as well.

Best bet for contact with Sterling is to call the phone number on their website. When I've done this in the past, it went directly to the US rep. He called me back quickly, even while he was on vacation. Seems like a stand-up guy.

somewhereinusa · October 26, 2019, 07:37:21 PM

Quote from: neoneddy on October 25, 2019, 10:16:53 AM

I'm really impressed with these Valence Batteries right now https://www.ebay.com/b/Valence-Rechargeable-Batteries/48619/bn_114829959 130+AH@12v for $450 Most of these are testing at 95% capacity. The medical devices they come from are switched out yearly or something.

I have 6 of these as well as the software to communicate with the internal BMS. Still in initial testing not hooked to solar yet. I'm using with a Victron inverter/charger and so far have been impressed. From what I have been able to determine the U27 138 Ah ones were used, at least most of the ones that seem to be for sale, in Smith electric trucks. My first four were all cycled less that 200 times, the last two less than 10. If you are near Milwaukee you can get them from the guy who is going around buying these trucks for about $300, if you need shipped there are $400. In 6 batteries I have about 660 Ah usable.
The 40 Ah models are the ones used in medical equipment.

Oonrahnjay · October 26, 2019, 08:23:52 PM

Quote from: neoneddy on October 25, 2019, 10:16:53 AM... I'm really impressed with these Valence Batteries right now https://www.ebay.com/b/Valence-Rechargeable-Batteries/48619/bn_114829959 130+AH@12v for $450 Most of these are testing at 95% capacity. The medical devices they come from are switched out yearly or something. I ended up with 6 Telecom AGM batteries I got for $150-ish each or so. 210 AH @12v , yeah they weigh 130lb each, but $1000 for 14kw of battery storage is hard to beat even if it's an older chemistry.

I got an incredible deal on used batteries. A storage guy had 10 AGM "High Rate Max" batteries, 12V. 78 A/hr each that somebody had bought surplus from a cell phone maintenance company and dumped at his place. I asked him if he'd sell them - he said "yes, I was going to take them to the battery recycle place, they offered me $12 apiece for them but it's such a pain in the **s to haul them down there, I haven't gotten around to it. I should though, I need to get them out from in the way". I asked "how much for each? - he said "I told you, $12 - you're doing me a favor so I don't have to haul them". I got that battery bank for $120. They have about 5 years left on their "expected" life span. I put each on a battery maintainer, at 6 Amp charge they all went to "Float" in less than an hour (so they hadn't been sitting around discharged).
I went by a bit later, the storage place was sold and the guy who had them (not that it would do any good because he didn't know where they came from) wasn't working there any more, so it's a buy I can never repeat.
I don't put a lot of load on them but they're working just fine.

No interest in solar, but I'm lovin this battery bank.

freds · October 26, 2019, 09:46:27 PM

Quote from: Oonrahnjay on October 26, 2019, 08:23:52 PM
I don't put a lot of load on them but they're working just fine.

No interest in solar, but I'm lovin this battery bank.

And since you are not supposed to discharge below 50% that is how many kilowatts usable and how many pounds to truck the road?

Oonrahnjay · October 26, 2019, 10:59:38 PM

Quote from: freds on October 26, 2019, 09:46:27 PMAnd since you are not supposed to discharge below 50% that is how many kilowatts usable and how many pounds to truck the road?

Since some b*ts**d stole one of them from my shop, I only have nine. Therefore, it's about 682 12V/A-hrs. or about 8.7 total k/watt/hrs or 4.35 useable. But for $120, who ITF cares??