Bus conversion Self sufficient.

[cadillackid]

Originally Posted by Brewerbob

I dunno what that means.

You're not off grid are you? Does it make a difference?

You're always on the road and using that alternator. Is 200 amp big enough? Is there bigger? To do it over again, ...

i have 2 busses.. the DEV bus is the one set up as a mobile Tech Development lab.. I named it DEV RANDOM..

I do park the bus and work out of it.. so thats when the batteries come into play.. sure when im driving the alternator is running anything I have turned on., my big power user is the A/C when the bus is shut off... when im driving that load is gone as im running off of the engine-driven A/C then.. so the 200 amp has always been big enough to do the job...

to do it over again I'd gut the bus, replace the floors ,insulate the ceiling, and tint the windows.... electrically ive got exactly what I need.. and I could add a 3rd house battery if I run down the batteries too quickly.
-Christopher

[Brewerbob]

Originally Posted by cadillackid

my big power user is the A/C when the bus is shut off...

Fridge, heat, hot water? Cells and laptops wouldn't need a lot.

[cadillackid]

Originally Posted by Brewerbob

Fridge, heat, hot water? Cells and laptops wouldn't need a lot.

I dont camp so no water, heat I use the Webasto heater which is Diesel fired and then its just a bus heater fan to blow the heat(the webasto heats the coolant).. frig is just a little cubie.. it doesnt take too much..

I usually only strop for a couple hours at a time. if im over-nighting im in a hotel so everything is shut off.

-Christopher

[Brewerbob]

I dunno if you can be considered a Skoolie of you don't sleep on board!!

[cadillackid]

Originally Posted by Brewerbob

I dunno if you can be considered a Skoolie of you don't sleep on board!!

hmmm.. the little thing under my name says im a 'Bus Geek' thats really the perfect fit for me.. im just really into school buses ..

Ive tossed an air mattress on the floor of the bus and slept for a couple hours before...

I really just like driving , working on, and doing cool stuff with school buses, meeting cool people that are into skoolies..
-Christopher

[kflowers]

Originally Posted by cadillackid

I have my 2 main starting batteries.. and then have an isolated set of 2 AGM deep cycle batteries... since they are isolated the main bus batteries wont get run down when using my AGM's..

if I do decide i want all 4 batteries to do the job, either for helping to start the bus, or in the event I want all 4 running inside equipment, I can throw a manual switch to tie all 4 together...

I could easily see where you might want 5 batteries.. im guessing they will isolate some of them to not kill all 5..
-Christopher

That is exactly what we are doing. 2 for the bus and 3 for the house.

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[EastCoastCB]

Originally Posted by Brewerbob

I dunno if you can be considered a Skoolie of you don't sleep on board!!

To me a "skoolie" is anyone re-purposing a school bus for whatever.

[EastCoastCB]

Originally Posted by cadillackid

hmmm.. the little thing under my name says im a 'Bus Geek' thats really the perfect fit for me.. im just really into school buses ..

Ive tossed an air mattress on the floor of the bus and slept for a couple hours before...

I really just like driving , working on, and doing cool stuff with school buses, meeting cool people that are into skoolies..
-Christopher

[TAOLIK]

Edit: The below statement is probably incorrect, Thank you to BrewerBob for calling me out.

I'm only speaking with no experience, but isn't there some reason that using odd number batteries that's not ideal? I'm totally pulling BS from some distant memories, but I thought it was something about how the electrical draw on the batteries becomes unbalanced and it will discharge batteries unevenly, leading to imbalanced voltage, which will make the batteries slowly discharge themselves in an attempt to balance out the unbalanced voltages. I could totally be wrong or misunderstand, I'm no electrical expert.

Nice storage extensions though, I'm going to study your framework today for inspiration!

[Brewerbob]

Originally Posted by TAOLIK

I'm only speaking with no experience, but isn't there some reason that using odd number batteries that's not ideal? I'm totally pulling BS from some distant memories, but I thought it was something about how the electrical draw on the batteries becomes unbalanced and it will discharge batteries unevenly, leading to imbalanced voltage, which will make the batteries slowly discharge themselves in an attempt to balance out the unbalanced voltages. I could totally be wrong or misunderstand, I'm no electrical expert.

Nice storage extensions though, I'm going to study your framework today for inspiration!

I believe you are correct, ... in that it's total BS being pulled from the nether regions.

Batteries tied in parallel will all see the same voltage and will have equal current draw. Now if you went stupid with wiring with WAY different lengths/resistances you could cause some problems.

My guess is you're remembering speakers and unbalanced impedance. Impedance equals resistance at a particular frequency.

[TAOLIK]

Thank you for calling me out, I resign my prior statement.

[Brewerbob]

Nah it's a fair question or a non electronics geek.

[MarkyDee]

Originally Posted by TAOLIK

Edit: The below statement is probably incorrect, Thank you to BrewerBob for calling me out.

I'm only speaking with no experience, but isn't there some reason that using odd number batteries that's not ideal? I'm totally pulling BS from some distant memories, but I thought it was something about how the electrical draw on the batteries becomes unbalanced and it will discharge batteries unevenly, leading to imbalanced voltage, which will make the batteries slowly discharge themselves in an attempt to balance out the unbalanced voltages. I could totally be wrong or misunderstand, I'm no electrical expert.

Nice storage extensions though, I'm going to study your framework today for inspiration!

Electrical Engineer here (hi guys! first post!). TAOLIK, you're actually quite correct. No battery is ever identical to another - there will always be a "weaker" or "weakest" one. When batteries are connected in parallel, the "weaker" or "weakest" battery will pull down all other batteries (and also won't let the stronger batteries charge fully which can cause problems like shortened lifespan). However, if you connect them via battery isolators (nothing more than a big diode - a one-way valve for electricity), then the weak battery won't pull down the strong batteries.

Now, should you have a charge/load controller that has terminals for multiple batteries, then it will act as the isolator so you don't have to have separate battery isolators. The controller will also be able to charge the batteries to their full capacities.

Now, if you connect your batteries in series then this whole "battery isolator" issue "goes away" - which is why series is generally more recommended than parallel if batteries need to be combined.

[TAOLIK]

Originally Posted by MarkyDee

Electrical Engineer here (hi guys! first post!). TAOLIK, you're actually quite correct. No battery is ever identical to another - there will always be a "weaker" or "weakest" one. When batteries are connected in parallel, the "weaker" or "weakest" battery will pull down all other batteries (and also won't let the stronger batteries charge fully which can cause problems like shortened lifespan). However, if you connect them via battery isolators (nothing more than a big diode - a one-way valve for electricity), then the weak battery won't pull down the strong batteries.

Now, should you have a charge/load controller that has terminals for multiple batteries, then it will act as the isolator so you don't have to have separate battery isolators. The controller will also be able to charge the batteries to their full capacities.

Now, if you connect your batteries in series then this whole "battery isolator" issue "goes away" - which is why series is generally more recommended than parallel if batteries need to be combined.

Thank you MarkyDee, and welcome to the forum! It is great to have electrical guru's here to keep us nuts alive. Based off your explanation, I assume that I may have been right, but the foundations of my statement still seem incorrect. Which brings up a few questions I'd love to pick your brain about.

1. If the batteries were wired up in a series wouldn't that increase the voltage to be between 36V (in the case of 3x12v batteries)? Would you just use a converter to convert that voltage down to 24 or 12v?

2. I am just about to make my own electrical system with 4x6v flooded batteries, I intend(ed) to run them series&parallel, but assuming I have the necessary charge controllers for the incoming wattage, I won't suffer the same fate that you were explaining where the weakest battery would burden the others?

3. In the case of this self sufficient bus conversion: Would a charge controller(I believe there was some mention of solar) resolve any imbalance between the 3 batteries being run in parallel?

Thank you for chiming in, I am glad we have +1 electrical expert in our community.

[Iceni John]

SmartGauge (maker of arguably the most rational and effective battery monitor anywhere) has some words to say about this subject: SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

It would be prudent to spend some time reading their other articles, and to heed their advice.

John

[MarkyDee]

Originally Posted by TAOLIK

Thank you MarkyDee, and welcome to the forum! It is great to have electrical guru's here to keep us nuts alive. Based off your explanation, I assume that I may have been right, but the foundations of my statement still seem incorrect. Which brings up a few questions I'd love to pick your brain about.

1. If the batteries were wired up in a series wouldn't that increase the voltage to be between 36V (in the case of 3x12v batteries)? Would you just use a converter to convert that voltage down to 24 or 12v?

2. I am just about to make my own electrical system with 4x6v flooded batteries, I intend(ed) to run them series&parallel, but assuming I have the necessary charge controllers for the incoming wattage, I won't suffer the same fate that you were explaining where the weakest battery would burden the others?

3. In the case of this self sufficient bus conversion: Would a charge controller(I believe there was some mention of solar) resolve any imbalance between the 3 batteries being run in parallel?

Thank you for chiming in, I am glad we have +1 electrical expert in our community.

Thank you for the welcome! I'm always humbled by the generosity of communities sincere in their pursuits.

I'll try to answer your questions, but nothing sufficies for our own research.

1. Series connections multiply voltage; parallel connections multiply current. So, yes, the three batteries in series would be nominally 36v. The actual voltage would fluctuate based on various factors like age, current draw, temperature, etc.

As for 36v to 12v conversion, yes, there are products on the market that can do that kind of conversion - at least there were when I was researching electric car conversions back in the mid-90s (i.e. down-converting the traction pack's usually 96v or greater to 12v to run the car's accessories without using yet-another-battery). I'd be surprised with th EV car culture out in California if those products weren't still around....

2. Yes, the 'weaker' string will pull down the 'stronger' string if the two battery strings aren't isolated from each other. There are other knock-on effects as well like shortening the life of the stronger string, and not allowing the stronger string to fully charge or take a balancing charge. What will happen is the weaker string will gobble up the energy and split the water inside into hydrogen/oxygen. If the batteries aren't properly vented then you could end up with a bomb in your battery bay and not know it.

3. For parallel connections only if the charge controller has individual connections for each battery or series-connected strings. Otherwise what I explained in point 2, above, will happen.

Please don't misunderstand me - there's probably someone 'out there' who has had a parallel-connected battery bank since "the beginning of time" and never had an issue, but generally speaking its not the best way of connecting batteries together (especially for the layman who isn't expecting certain issues). Lead-acid can be an incredibly forgiving battery (compared to the other battery chemistries - i.e. the flaming LIon batteries we carry in our pockets), but there's still 'gotchas'.

Basically I'm advocating for good maintenance. If you connect in parallel, then be sure to disconnect the parallel structure every so often and apply a finishing and, if using flooded batteries, a de-sulfating charge to the individual batteries or strings. You will be rewarded with longer battery life and deeper discharges....

By the way, try not to discharge a lead-acid battery 'all the way' . Always try to maintain a minimum of 20% charge. Your battery life will thank you....

[TAOLIK]

Thank you for taking the time to detail all that out, I really appreciate it!

[MarkyDee]

Originally Posted by TAOLIK

Thank you for taking the time to detail all that out, I really appreciate it!

No problem. However, I'm just regurgitating information that can be found around the internet like what Iceni John found (oh, and what I learned in college after blowing up a few things... yea, my prof wasn't happy, but I sure had fun...).

[Brewerbob]

Originally Posted by MarkyDee

No problem. However, I'm just regurgitating information that can be found around the internet like what Iceni John found (oh, and what I learned in college after blowing up a few things... yea, my prof wasn't happy, but I sure had fun...).

Ah, someone else that plugged electrolytics into power strips and launched them across the room. Better still is charging one, "here, hold this".


When buying a bus that has two different brands of batteries and two vastly different dates on them, I can see what you've mentioned happening without isolators. Two batteries out of the same manufacture batch tho... Again, I haven't looked into electrical for a bus yet but I wouldn't go out of my way to do anything special with them. Now if the solar system comes with an isolator, or they are the next aisle over and stupid cheap, then why not?

I've also not priced bus batteries. I suspect they are more than car batteries but about the same as marine. Is this the case?

[kflowers]

We Made a good amount of progress this weekend making the couch. We are working on the sides sometime this week.




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